taxonID	type	description	language	source
03D987B588667D01FF4EFF38FDF8FA7F.taxon	description	Figs 5, 6 Diagnosis. Adult female, 1,260 µm in length excluding caudal setae. Genital double- somite 1.1 times longer than wide, ducts divided horizontally into two parts (Fig. 5 A). Antenna basis with two rows of spinules (Figs 5 B, C, 6 E, F). Basis of P 4 has well-developed spinous process on distal margin (Fig. 6 B, C). Coxopodite with few short rows of small spinules (Figs 5 D, 6 C); terminal outer spine of P 4 endopod 1.2 times longer than median spine (Figs 4 B, H, 5 E). Inner spine of P 5 shorter than whole segment (Fig. 6 A, D). Caudal rami approximately 4 times longer than wide (Fig. 6 G). Remarks. Illustrated specimen from the Machadinho Reservoir, Uruguay River. Einsle (1996) stated that this “ European ” species has wide seasonal and spatial variability. In South America, its morphology and variability need to be better investigated, as some taxonomic characters do not fully agree with the description of A. robustus robustus. Molecular techniques should be used to compare the South American populations with populations from other continents. This species is distributed in southeastern and southern Brazil, and also occurs in Uruguay and Argentina. A. robustus robustus is found in the Tietê and Iguaçu rivers, but has not been recorded in the Paranapanema River, which is located between them. It is considered that A. robustus robustus prefers lower and moderate temperatures. It was found in the Barra Bonita Reservoir (Tietê River), a relatively shallow reservoir with few months of low temperatures during the year. It seems to be abundant in eutrophic reservoirs (Perbiche-Neves et al. 2016).	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588677D01FEF4F9F6FAF0F9D3.taxon	description	Figs 7, 8 Diagnosis. Adult female, 990 µm in length excluding caudal setae. Body fusiform (Fig. 8 A, B). P 5 short and fused to somite, closely adjoined to body surface, all setae similar in size and reach to or passing midlength of genital double-somite (Figs 7 A, 8 D). Caudal ramus short, 1.2 to 1.8 times longer than wide, with at least three transverse rows of spinules, each row of different size (Figs 7 B, C, 8 C). Remarks. Species with a wide geographic distribution in the Americas, often found in littoral regions, aquatic macrophytes and rivers, seldom occurring in the zooplankton of reservoirs. The body shape is fusiform. Animals with a dark (black or brownish) color, usually with debris attached to the body somites and appendages due to their benthic habit. This genus requires thorough taxonomic revision.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588677D02FCBBF99AFAF5F9B3.taxon	description	Fig. 9 Diagnosis. Adult female, 750 µm in length excluding caudal setae. Inner spine of the terminal endopod of P 4 D 1.3 – 1.4 times longer than the outer spine of the same segment (Fig. 9 A). Caudal rami 3.6 – 4 times longer than wide (Fig. 9 B). Genital double-somite divided horizontally, both portions having equal or similar widths (Fig. 9 C). Remarks. Species with a wide geographic distribution in the Americas. It is often found in littoral zones, among aquatic macrophytes and in rivers, and is seldom found in the pelagic zone of reservoirs. Animals with a dark (black or brownish) color, usually with debris attached to the segments and appendages due to their benthic habit. A distinctive character that allows its separation from other closely related species is the proportional width and length of the caudal rami.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588647D03FC8FF9BBFA5FF960.taxon	description	Figs 10, 11 Diagnosis. Adult female, 1,340 µm in length excluding caudal setae. P 5 inner seta shorter than the median and out- er setae (Figs 10 A, 11 B); genital double-somite with lateral projections beating tuffs of setules, divided horizontally and the lower part is wider than the upper part. (Fig. 10 A). Long caudal rami, 8 times longer than wide, spinules along the entire outer margin or only on the distal margin (Figs 10 A, B, 11 C, D). Dorsal row of spinules on each side of the anus at last urosomal segment (Fig. 10 C). P 4 endopod terminal segment is 2 times longer than wide, outer terminal spine of this segment is 1.4 times longer than the inner spine (Fig. 10 D). Remarks. A species with a wide geographic distribution in the Americas. It is often found in coastal regions, aquatic macrophytes and rivers, and it is seldom found in the plankton of reservoirs. Animals with a dark (black or brownish) color, usually with debris attached to the segments and appendages, due to their benthic habit. This species can be easily distinguished by the long caudal rami, compared to the other congeners. The subspecies Eucyclops neumani titicacae Kiefer, 1957, recorded from Peru, Colombia and Venezuela, was raised to species rank by Fuentes-Reinés and Suárez-Morales (2013).	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588627D05FEFCFA6AFE86FBF1.taxon	description	Figs 12, 13 Diagnosis. Adult female, 870 µm in length excluding caudal setae. Simple duct projections in the genital double-somite, not divided by an internal integumental scar as in Eucyclops (Denticyclops) leptacanthus (Fig. 12 A). Hyaline membrane on the last antennule segment with a finely serrulate pattern (Fig. 13 A). Caudal ramus 4.6 times longer than wide, outer ornamentation (spinules) without gradual change in size (Figs 12 B, 13 B, C). Inner terminal spine of the last segment of of P 4 endopod 1.3 times longer than the segment (Fig. 12 C, D). Remarks. Species with a wide geographic distribution in the Americas. It is often found in coastal regions, among aquatic macrophytes and in rivers, and it is seldom found in the plankton of reservoirs. Animals with a dark (black or brownish) color, usually with debris attached to the appendages and body surface due to their benthic habit. This species can be distinguished from congeners by the spinules along the entire outer margin of the caudal rami, and by its proportional width and length. C D	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588637D05FF3EFA88FA5FF965.taxon	description	Figs 14, 15 Diagnosis. Adult female, 1,390 µm in length excluding caudal setae. Caudal ramus 5 times longer than wide (Fig. 15 A, D, E); row of spines extending over half or up to the entire outer margin of the caudal ramus (Figs 14 A, D, 15 D, E). Seminal receptacle ducts horizontally divided into two parts (Fig. 14 B). P 5 middle seta 1.8 – 1.9 times longer than the inner spine (Figs 14 C, 15 B, C). Inner spine of the terminal P 4 - endopod segment 1.2 times shorter than the outer spine (Fig. 12 D). Remarks. Species with a wide geographic distribution in the Americas, often found in coastal regions, aquatic macrophytes and rivers. It is seldom found in pelagic regions of reservoirs or lakes. Animals dark or brown-colored and usually with debris attached to the body segments and appendages, due to the benthic or littoral habit. This species can be distinguished from the other congeners by the proportions of the caudal rami and the extent of the spinules along the outer margin. The division of the genital double-somite and the proportions of the spines and setae on the P 5 are also distinctive characters. Possibly, a complex of cryptic or semi-cryptic species is hidden under similar morphologies.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588607D06FEEEFA54FB53F9A6.taxon	description	Fig. 16 Diagnosis. Adult female, 1,730 µm in length excluding caudal setae. Broad and robust body. Maxilliped has few rows of spinules on the exopod (Fig. 16 A). Genital double-somite 1.2 times wider than long (Fig. 16 B). Seminal receptacle has lateral projections (Fig. 16 B). Antennule is 17 - segmented. P 5 middle seta longer than the outer and inner setae (Fig. 16 C). P 4 - endopod outer terminal spine 0.8 – 0.9 times the length of the segment (Fig. 16 D). Remarks. Species with wide geographic distribution and usually found in low numbers in zooplankton samples. Large-bodied copepod, often associated with aquatic macrophytes and littoral zones. In samples from macrophytes, several individuals were collected.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588607D07FC89F9A6FEEDF965.taxon	description	Figs 17, 18 Diagnosis. Adult female, 1,280 µm in length excluding caudal setae. Caudal ramus without ornamentation on the inner margin, 2.0 times longer than broad (Figs 17 A, 18 A). A Hyaline membrane of the last segment of the antennule smooth (not serrulate). P 4 - intercoxal sclerite with three rows of spinules. Inner and outer P 4 terminal spines of the same length (Figs 15 B, 18 C). First segment of P 5 with row of small spinules on the surface being an outer proximal row, an inner curved medial row and an inner distal row (Figs 17 C, 18 B). Remarks. Cosmopolitan species, usually found in low numbers in samples from rivers, littoral zones, aquatic macrophytes and various environments such as caves, dolomitic lakes, puddles, and others. In these environments, peaks of high abundance can occur. It is seldom found in reservoirs zooplankton.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588617D18FC8DFA81FCC1FAF2.taxon	description	Fig. 19 Diagnosis. Adult female, 1,950 µm in length excluding caudal setae. Caudal ramus 2.5 – 2.6 times longer than wide, lateral outer setae inserted in the distal third; row of spinules on the distal margin of the third urosomal segment (Fig. 19 A). P 5 ending in an inner acuminate tip (Fig. 19 B, C, E). Inner spine of the P 4 - endopod terminal segment slightly longer than the outer one (Fig. 19 D). Remarks. Large, cosmopolitan species, seldom appearing in high numbers. Specimens found in aquatic macrophyte banks. It is very rare in reservoir zooplankton, but common in lotic stretches and floodplains. As it is the only species of the genus, it is easily identifiable by the P 5.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5887E7D19FF0FFA7AFBE8F961.taxon	description	Fig. 20 Diagnosis. Adult female, 1,300 µm in length excluding caudal setae (Fig. 20 A). Caudal rami about 3 times longer than wide, setules along the entire inner margin; telson has a continuous row of spinules near each caudal rami insertion (Fig. 20 B). Genital double-somite 1.1 – 1.3 times longer than wide, without setules (Fig. 20 C). Seminal receptacle tapering distally in the lateral projections; proximal margin usually sinuous in the middle (Fig. 20 C, arrow). Transverse seminal ducts forming a fused V shape in the copulatory pore; copulatory duct usually strongly curved (Fig. 20 C). Irregular intervals of 4 – 10 spinules rows on the distal margin of P 4 coxa; 4 – 11 spinules usually arranged in a single row at the latero-distal angle; proximal row of 4 – 12 large spinules, and dense outer setulae patch (Fig. 20 D). Inner apical spine of terminal P 4 - endopod segment 1.1 times longer than the outer one (Fig. 20 F). Basis of antenna spinule ornamentation patterns similar to the M. leuckarti - type, a wide field of spinules on posterior margin at the level of the insertion of the median seta, a group of very small longitudinal spinules along the outer margin, and an inner row of longitudinal spinules at irregular intervals, near the concave margin (Fig. 20 G, H). Anterior face of the antenna basis composed of 17 – 35 spinules arranged in a longitudinal row along the inner concave margin, transverse row of small spinules on the distal margin, and a transverse row of spinules medially, on the outer margin (Fig. 20 G, H). Strongly serrulate hyaline membrane on the last segment of antennule, large indentation in its medial portion (Fig. 20 E). Remarks. Collected in the middle stretch of the Paraguay River, which has slow flow and many drifting macrophyte banks. Perbiche-Neves et al. (2014) found this species in the Barra Bonita reservoir, which is the first record of this species for São Paulo state. The species was previously recorded by Reid et al. (1988) in Minas Gerais and Reid (1994) in the Federal District. Reid (1985) stated that this species has been recorded from Colombia, Venezuela, Antilles, Africa, Asia and islands of the Pacific Ocean. It is one of Mesocyclops species considered as a pantropical species (Holyńska 2000), and present in Australia. Holyńska et al. (2003) mentioned this species from the islands of Sumatra, Singapore, and Hawaii.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5887C7D1AFEE9FB98FBA3F965.taxon	description	Fig. 21 Diagnosis. Adult female, 960 µm in length excluding caudal setae (Fig. 21 A). Setules on inner margin of caudal rami (Fig. 21 B). Genital double-somite 1.0 – 1.2 times longer than wide, seminal receptacle with very narrow elliptical ducts expanding horizontally (Fig. 21 C). Ornamentation of P 4 - coxa in posterior view composed of 5 or 6 groups of spinules; with one proximal row in the middle, one inner row (close to the intercoxal sclerite) medially on the segment, two spinules rows on the distal outer margin and one row on the distal inner margin; occasionally, individual spinules also occur in the middle portion (Fig. 21 D). P 5 terminal seta slightly longer than the inner spine and the outer seta of the anterior segment (Fig. 21 E). P 4 endopod outer terminal spine 1.1 times longer than the inner one (Fig. 21 G). Terminal segment of the antennule with a finely serrulate hyaline membrane (Fig. 21 F). Antenna basis with row of spinules on the inner concave margin in anterior and posterior views in a similar trend, slightly smaller spines in the proximal and distal regions and larger spinules in the middle, giving a semi elliptical shape to this ornamentation (Fig. 21 H, I). Remarks. In this study, this species was found only in the upper stretch of the Paraguay River, which has a slow flow and many drifting aquatic macrophyte banks, especially Eichhornia sp. Holyńska et al. (2003) mentioned that this species occurred in small puddles (type locality is Bom Conselho, Pernambuco, Brazil) and in large lakes such as Lake Maracaibo in Venezuela, and these authors mentioned a variation for the P 4 terminal endopod inner spine between 0.9 – 1.2 times than the outer one. In Brazil, Perbiche-Neves et al. (2014) found this species in the eutrophic Barra Bonita Reservoir, contrasting with the suggestions by Dussart (1984) and Rocha and Botelho (1998) that this species prefers oligotrophic waters. Probably the association with macrophytes is valid. This species is easily recognizable by the elliptical seminal receptacle, the basis of the antenna, and the P 4 coxa. It can be confused with Mesocyclops reidae, but this latter species has been recorded only in Central America and southern North America.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5887D7D1CFF51FB1FFD87FA13.taxon	diagnosis	Diagnosis. Adult female, 1,510 µm in length excluding caudal setae. Four groups of spinule rows on the anterior side of the P 4 basis (Fig. 22 A). Ducts of seminal receptacle curved posteriorly (Fig. 22 B). Caudal ramus is 3.2 times longer than wide and with setules on inner margin (Fig. 22 C). One row and two patches of spinules at maxilliped exopod (Fig. 22 D). Hyaline membrane of last segment of antennule is strongly serrulate, strongly indentation medially developed (Fig. 22 E). Antenna basis with three small rows of spinules in anterior view (Fig. 22 F) and two larger rows of spinules in posterior view, without small spinules (Fig. 22 G). P 5 apical seta 2 times longer than the median spine. P 4 - endopod terminal segment 2.5 times longer than wide. Remarks. The specimen examined was found in the Iguaçu River, in the Foz do Areia Reservoir. It is widely distributed in the upper Paraná River Basin, as shown by several reports (Perbiche-Neves et al. 2014). This species has a wide geographic distribution in South America, and is usually found in low numbers, possibly because it is large and predatory. It is eurythermal and produces egg-sacs with many eggs (> 100). In Brazil, the subspecies M. longisetus curvatus has been widely reported, but the validity of this subspecies has been doubted, as the details used to identify it are rarely observed. We decided in this study to be conservative, however a revision of these subspecies especially in the Neotropics is necessary to validate the difference. Considering the results of Wyngaard et al. (2010), these authors do not find significant difference between populations of M. longisetus from USA and M. longisetus curvatus from Brazil. This species can occur in various environments, such as the pelagic zone, littoral of rivers and lakes, among aquatic macrophytes, river channel, puddles, etc.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5887A7D1DFF00FA5BFB92F964.taxon	description	Figs 23, 24 Diagnosis. Adult female, 1,100 µm in length excluding caudal setae. Genital double-somite is 1.3 times longer than wide. Seminal receptacle has narrow, almost filiform and horizontal lateral expansions (Fig. 23 A). P 4 endopod outer terminal spine is approximately in the same length as its segment (Figs 23 B, 24 E). Hyaline membrane on the last segment of antennule with small indentations in the proximal 2 / 3 and heavily indented, more than three large invaginations in the distal 1 / 3 (Figs 23 C, 24 C). Distal margin of P 4 intercoxal sclerite smooth (Fig. 23 D); P 4 basis with six groups of spinules in posterior view: three short rows of small spinules proximally, one row in the medial region, one group transversely on the lateral outer margin, and a row on the inner distal margin (Fig. 23 D). Spinule pattern of antenna basis anterior surface: two converging rows proximally, near the concave margin; two rows of different lengths near the insertion of the outer seta, and a short row, medially, on the inner margin (Fig. 23 E). Mandible endopod segment with proximal, middle, and distal rows of spinules in anterior view (Fig. 24 A). Caudal ramus 2.6 times longer than broad, smooth, or finely hirsute on the inner margin (Fig. 24 B). Remarks. Specimen collected in the Middle Paraguay River. This species is widely distributed in the La Plata Basin. It was described by Kiefer (1926) from samples from the Paraguay River. It was, and still is, confused with Mesocyclops brasilianus, described from the Amazon region by Kiefer (1933). Dussart (1984) suggested a possible synonymy of M. meridianus with M. brasilianus. Gutiérrez-Aguirre and Suárez-Morales (2001) confirmed some morphological differences between these two species, and identified some specimens from São Paulo state as M. meridianus. Later, supporting the previous hypothesis, Gutiérrez-Aguirre et al. (2006) reviewed the Neotropical Mesocyclops and observed that M. brasilianus occurs in the Amazon region and M. meridianus more southward on the continent. Possibly, records in northern Brazil are of M. brasilianus, but they need to be verified. The original description of M. meridianus was based on specimens from Paraguay, and several studies indicate that M. meridianus occurs in almost the entire La Plata Basin. However, further studies are needed, as it is possibly a complex of species that cannot be reliably identified based on morphological characters only, since specimens with intermediate characteristics between these two species are often found. In this study, all specimens of this species were checked in detail and confirmed as M. meridianus. However, molecular analyses are needed, comparing organisms from different regions across South America and looking for variations within populations. When comparing this species with others presented by Holyńska et al. (2003), it can be confused with Mesocyclops meridionalis, Mesocyclops pseudomeridianus and Mesocyclops paranaensis.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588787D11FF08FAE1FD57F9AB.taxon	description	Fig. 25 Diagnosis. Adult female, 1,180 µm in length excluding caudal setae. Genital double-somite 1.2 times longer than wide, seminal receptacle with lateral and posterior expansions (Fig. 25 A). The last P 4 endopod segment 1.1 times longer than the inner terminal spine of this segment; this inner terminal spine not exceeds the outer apical spine length (Fig. 25 B). Last segment of antennule is ornamented with a narrow, finely serrulate hyaline membrane almost entirely, except to a large subterminal invagination (Fig. 25 C). Row of spinules in the anterior region of the maxillule palp (Fig. 25 D). Antenna basis is of the “ leuckarti ” type with proximal, medial, and distal rows of spinules; in anterior view a row of spinules on the lateral outer margin and two rows of spinules in the middle of the segment, three rows in the inner margin, and a row of larger spinules on the distal margin, close to the insertion of the terminal setae (Fig. 25 E). P 4 basis with three rows of large spinules in anterior view, two on distal margin and one transverse row close to the outer margin, almost in the middle of the segment (Fig. 25 F). P 4 intercoxal sclerite has small projections on the distal margin. Caudal ramus 2.7 times longer than wide, without setules on the inner margin. Remarks. Specimen collected in the Rio Grande River, Água Vermelha Reservoir. This species is native from Africa and is now widely distributed in southeastern Brazil. Until now, the records indicate that this invasion began in the upper Paraná River Basin. It may have been introduced with tilapia culture (Coelho and Henry 2017, Macêdo et al. 2022). More studies are needed to determine its true distribution, whether it is restricted to specific regions, or whether it is limited to the tropics, as it has been found only in southeastern Brazil, not occurring farther south in the La Plata Basin (Perbiche-Neves et al. 2014). Based on data from Castilho-Noll et al. (2023), this species was found in 43 studies in Brazil, the first dated from 1994 in Furnas Reservoir (Reid and Pinto-Coelho 1994), followed by 2001 and 2002 in the Upper Paraná River floodplain (Velho et al. 2001, Lansac-Tôha et al. 2002), and several records were published after 2002 in São Paulo State, especially in reservoirs (e. g., Matsumura-Tundisi and Silva 2002). Custodio et al. (2024) listed 63 records of M. ogunnus in Brazil distributed in 70 articles, and these authors provided models for the distribution of M. ogunnus in the main river basins in Brazil, with potential colonization across the Paraná River Basin, the main watercourses of the Amazon River Basin, and the San Francisco River. The first record in Northeast Brazil was published in 2013 (Cardôso et al. 2013) and in the Amazon in 2017 (Silva and Roche 2017). Probably previous records of Mesocyclops kieferi in São Paulo State refer to M. ogunnus, as Matsumura-Tundisi et al. (1990) corrected by Matsumura-Tundisi and Silva (2002), Nogueira (2001), Rocha et al. (2002), Santos-Wisniewski and Rocha (2007), and Sartori et al. (2009), according to Castilho-Noll et al. (2023).	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588777D14FF15F9A3FF34FEB8.taxon	description	Fig. 26 Diagnosis. Adult female, 770 µm in length excluding caudal setae. Short P 5 apical setae; seminal receptacle with thin lateral projections and a long and wide posterior projection (Fig. 26 A). A row of spinules on the distal margin of the last urosomal segment, near the basis of the caudal ramus; caudal rami 2.3 times longer than wide; inner terminal setae of the caudal ramus shorter than the outer terminal setae (0.7: 1) (Fig. 26 B). P 4 endopod outer terminal spine is 1.1 times longer than inner terminal spine (Fig. 26 C). Intercoxal sclerite of P 4 is ornamented with small spinules (Fig. 26 C). P 1 intercoxal sclerite with 3 spinules on each rounded projection (Fig. 26 D). A D Remarks. The specimen illustrated was collected in the middle stretch of the Paraguay River. Reid (1985) reported this species in Paraguay, in swamps, and Dussart and Frutos (1985) found this species in the middle Paraná River, but did not provide a description. In our study this species occurred only in low numbers. The genus Metacyclops is diverse and in studies of planktonic organisms, few species are found. Most species occur in swamps, puddles, and ephemeral environments. A D B E C A	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588727D15FF59FA65FE86FA12.taxon	description	Fig. 27 Diagnosis. Adult female, 1,150 µm in length excluding caudal setae. The P 4 intercoxal sclerite bears a distal patch and irregular rows of spinules; coxa with two outer rows proximally (Fig. 27 B); inner apical spine of P 4 - endopod is 2.3 times the length of the outer one (Fig. 27 A). P 5 inner terminal spine is 2.5 times shorter than outer terminal one (Fig. 27 C). Inner and outer terminal seta of the caudal ramus about the same length; inner middle terminal seta of caudal ramus is less than 2 times the length of the ramus; caudal ramus 5.1 times longer than wide (Fig. 27 D). Genital double somite as long as wide; seminal receptacle with short lateral projections, with a wide proximal and tapered distal part (Fig. 27 E). Remarks. The specimen illustrated was collected in the Iguaçu River, in the Foz do Areia reservoir, which receives effluents from a large city. Perbiche-Neves et al. (2014) noted that this species occurs in impacted reservoirs, which was confirmed in this study. This species is widely distributed in reservoirs in the southeast-south regions of Brazil. Reid A (1985) reported its occurrence in some South American countries. It can be easily identified by its 2 - segmented P 4 and relatively long caudal rami compared to Metacyclops and Microcyclops.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588737D15FF2FFA5AFAC4F965.taxon	description	Figs 28, 29, 30 Diagnosis. Adult female, 720 µm in length excluding caudal setae (Fig. 28 A). The distal margin of the second prosomite bears an ornate scalloped membrane, and the other segments have smooth membrane (Figs 28 B, 29 B, C). Caudal ramus 3.1 times longer than wide (Figs 28 C, 29 A). The P 1 endopod terminal segment has a pore close to the outer margin in anterior view; P 1 endopod terminal spine serrated shape slightly asymmetric compared to Microcyclops finitimus and Microcyclops ceibaensis (Figs 28 D, 30 A, B, C). The inner apical spine on the terminal P 4 endopod segment 1.4 times longer than the outer spine (Fig. 30 D). P 5 last segment 2.4 times longer than wide; P 5 terminal spine 1.6 times shorter than the width of its segment in the middle portion (Fig. 30 E). Remarks. The specimen was collected in the upper stretch of the Paraguay River. Rocha (1998) provided simple and practical characteristics for the identification of five species of Microcyclops that occur in Brazil. Microcyclops anceps is widely distributed in South America (Dussart and Frutos 1985, José de Paggi and Paggi 2008). Reid (1985) reported it from Brazil, Argentina, Bolivia, Chile, Ecuador, Paraguay, Peru, Uruguay, Venezuela, Central America, and Mexico and Gutiérrez-Aguirre and Cervantes-MartÍnez (2016) examined specimens also from Guyana and Guatemala.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588707D16FF01FAC4FB8AF965.taxon	description	Fig. 31 Diagnosis. Adult female, 870 µm in length excluding caudal setae. Caudal ramus 3.3 times longer than wide (but the literature indicates a variation between 2.8 – 5 times), 5 – 6 spinules inserted anteriorly to the distal outer seta (Fig. 31 A). Genital double-somite 1.1 times longer than wide. P 1 - endopod last segment with two pores on the surface, close to the outer margin in anterior view; P 1 endopod last segment with a row of long spinules gradually increasing in length in the distal margin, close to the terminal spine, and long spinules gradually increasing in length close to the insertion of the distalmost inner distal seta (Fig. 31 B). Dorsal margin of prosomites 2 to 4 slightly serrated; urosomites with serrated hyaline fringes. P 4 basis has two transverse series of spinules in anterior view. Remarks. The specimen illustrated was collected in the lower stretch of the Paraná River. Reid (1985) reported this species in several countries in South America, in the coastal zone of lakes. Reid (1986) reported this species based on the observation of the type material deposited at the National Museum of Natural History, Smithsonian Institution (USA). Among the Microcyclops species found in the La Plata Basin, it is the only species with two pores in the last endopod segment of the P 1. Gutiérrez-Aguirre and Cervantes-MartÍnez (2016) advanced M. diversus as a synonym of M. ceibaensis.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588717D17FF00FA48FBBFF965.taxon	description	Figs 32, 33 Diagnosis. Adult female, 580 µm in length excluding caudal setae (Figs 32 A, 33 A). Prosomites 4 and 5 with a finely serrulate membrane on the distal margin and at the corners (Fig. 33 B, C), dorsal margin of first to third prosomites smooth. Last P 1 - endopod segment has a pore on the anterior surface, close to the outer margin, also a row of small spinules on the distal margin; terminal spine 1.2 times longer than the segment (Fig. 32 B). Caudal ramus 4 times longer than wide (Fig. 33 D). Remarks. The illustrated specimen was collected in the Tietê River, in the Três Irmãos reservoir. It has a wide distribution in South America, from Venezuela to the upper Paraná River Basin. It is more common near macrophyte banks or in the littoral zone. In the sampling sites it was relatively frequent, along with M. anceps. A complementary description of this species was provided by Gutiérrez-Aguirre and Cervantes-MartÍnez (2016).	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5884E7D29FF48FA22FDB1F9CC.taxon	description	Fig. 34 Diagnosis. Adult female, 1,180 µm in length excluding caudal setae. Caudal ramus 2 - 2.5 times longer than wide; small spinules at the insertion of the lateral seta and at the insertion of the terminal outer spine (Fig. 34 A, D). Last P 1 - endopod segment has three pores on the surface in anterior view, and large spinules gradually increasing in length close to the insertion of the apical spine (Fig. 34 B, C). Prosomites 4 and 5 has very finely serrate membranes. Seminal receptacle divided into two sections, one above and one below the ovigerous ducts; it has lateral projections that slightly taper distally. P 5 apical seta 3 times longer than the segment in which it is inserted. Remarks. The illustrated specimen was found in the lower stretch of the Paraná River, where it is commonly found near the banks of macrophytes. It can be easily identified by the lack of ornamentations on the second prosomites margins (excluding M. anceps) or fouth prosomite plus first urosomite (excluding M. finitimus) and the presence of three pores on the last segment of the P 1 - endopod.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5884F7D2AFF2DF984FDF0F9AD.taxon	description	Fig. 35 Diagnosis. Adult female, 1,340 µm in length excluding caudal setae. Inner terminal spine of the last P 4 - endopod segment 3 times longer than the outer terminal spine (Fig. 35 A). Caudal rami 3 times longer than wide (Fig. 35 B). P 5 - outer seta 1.3 times longer than the inner spine (Fig. 35 C). Remarks. This species has a wide geographic distribution in the Americas, and may belong to a complex of species. It is frequently found in rivers, littoral zones and among aquatic macrophytes. It can also occur in reservoirs, but seldom in the pelagic zone of storage reservoirs. The genus can be easily recognized by the single row of transverse spinules proximal to the lateral seta of the caudal ramus, different from Eucyclops which generally has spinules along the outer margin, or from Ectocyclops which has several small rows transversely and horizontally. Karaytug (1999) published a world revision and key for Paracyclops.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5884C7D2BFEFAF9A5FA4DF9CA.taxon	description	Figs 36, 37 Diagnosis. Adult female, 850 µm in length excluding caudal setae (Fig. 36 A). Caudal ramus 2.5 times longer than broad; lateral seta inserted in the distal third of the ramus; inner terminal seta is 3 times longer than the outer terminal seta (Fig. 36 A). Seminal receptacle with posteriorly curved aliform projections (Fig. 36 B). P 5 terminal spine is 1.1 times longer than the terminal seta (Figs 36 C, 37 D). Inner spine of terminal P 4 - endopod segment is 2.4 times longer than the out- er one (Figs 36 D, 37 A, B). P 4 intercoxal sclerite has ornamented spatula-shaped bilaterally symmetrical structures on the distal margin (Figs 36 E, 37 C). Mandible endopod has two patches of spinules in anterior view, one close to the distal outer margin, and another semicircular patch proximally (Fig. 37 E, F). Remarks. The specimen illustrated was found in the Uruguay River, in the Machadinho Reservoir. It is the most widely distributed species of Cyclopoida in reservoirs of the La Plata Basin, occurring in Brazil, Argentina, Paraguay, Uruguay, and other countries of the continent. Several studies report its wide occurrence in Brazil (Silva and Matsumura-Tundisi 2005, Nogueira et al. 2008). It is also present in Asia, Africa, and North America (Reid 1989) and Australia (Mirabdullayev et al. 2003). It is well adapted and often dominant in reservoirs and lakes, associated with increased trophy in some reservoirs (Sendacz and Kubo 1982, Landa et al. 2007, Silva 2011, Perbiche-Neves et al. 2016, 2021). However, it is also present in more oligotrophic locations, in both storage and run-of-river reservoirs (Nogueira et al. 2008). In this study, this species was found in almost all sampled environments, occurring both in reservoirs with oligotrophic characteristics, such as Furnas Reservoir in the Rio Grande, and in eutrophic reservoirs, such as Barra Bonita in the Tietê River Basin and Foz do Areia in the Iguaçu River Basin, where it was the dominant species. These results suggest that the use of this species as a bioindicator must be viewed with caution. In addition, the widespread use of the ratio Thermocyclops decipiens / Thermocyclops minutus should be critically addressed (Perbiche-Neves et al. 2021). Long-term or laboratory studies could shed some light on this question, with experiments designed to test hypotheses about the ratio of Thermocyclops decipiens / Thermocyclops minutus in different degrees of trophy. Studies of this nature could also include the other co-occurring species of the genus, T. inversus. This species can be distinguished from T. minutus and T. inversus by the shape of the cephalothorax, which is more fusiform in Thermocyclops decipiens, and by the curved caudal setae.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B5884D7D2DFC68F981FA5FF964.taxon	description	Fig. 38 Diagnosis. Adult female, 530 µm in length excluding caudal setae. Lateral arms of genital receptacle are straight (Fig. 38 A). Seminal receptacle exceeds ¾ the length of the genital double-somite (Fig. 38 A). Caudal rami 3 times longer than wide; the two median setae of the caudal ramus are thicker than in the other Thermocyclops species (Fig. 38 A). P 4 - endopod last segment terminal spine as long as the segment, and slightly shorter or in the same length than the outer terminal spine (Fig. 38 B). The specimen was found in the upper ParanaÍba River, Emborcação Reservoir. The body length of T. inversus from different locations shows wide seasonal and spatial variability. This species has been reported in Brazil, Paraguay, and Central America (Reid 1989, Perbiche-Neves et al. 2014) and is considered indicative of mesotrophic conditions by some authors (Silva 2011, Perbiche-Neves et al. 2016, 2021).	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588497D2FFF1FFAA1FA42F965.taxon	description	Fig. 39 Diagnosis. Adult female, 500 µm in length excluding caudal setae (Fig. 39 A). Seminal receptacle reaches ¾ of the the genital double — somite length (Fig. 39 B). Seminal receptacle lateral arms relatively short, with curveted expansion (Fig. 39 B). P 5 terminal spine and seta approximately of the same length (Fig. 39 C). P 4 - endopod last segment with sigmoid inner distal spine and longer than the segment, 5 times longer than the outer spine (Fig. 39 D). Caudal rami 2.5 – 2.8 times longer than wide, with a small spine at the base of the lateral seta of the caudal ramus (Fig. 39 E). Remarks. This species is common in Brazilian reservoirs and has been recorded in many studies. It generally predominates in oligo / mesotrophic waters, a trend observed in recent studies (Landa et al. 2007, Silva 2011, Perbiche-Neves et al. 2016). The proportion of this species compared to T. decipiens may indicate the trophic status, with a potential high abundance of T. decipiens in more trophic waters. However, this must be carefully evaluated since T. decipiens can also dominate in oligo / mesotrophic waters. Nevertheless, T. minutus is rare in eutrophic waters. This species is small compared to other cyclopoids, and extra care must be taken to avoid confusing it with copepodites of larger species. The curved inner terminal spine and the short outer spine of the third endopodal segment of P 4 are useful for the correct identification of this species.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
03D987B588467D22FF45F9B0FEB8FCEF.taxon	description	Fig. 40 Diagnosis. Adult female, 500 µm in length excluding caudal setae (Fig. 40 C). Genital double-somite 1.6 times longer than wide; seminal receptacle with two horizontal projections (Fig. 40 A). Caudal ramus 1.7 – 2.1 times longer than wide (Fig. 40 B). The P 5 inner seta and the outer spine has approximately the same length (Fig. 40 D). The P 4 - endopod outer terminal spine is slightly less than half the length of the inner terminal spine (Fig. 40 E). Remarks. This species is common in reservoirs and other lentic environments (pools, ponds, lakes, burrows) of Brazil and Argentina, and occurs in ephemeral environments where few species can survive, such as very warm waters or areas susceptible to freezing, or in ponds rich in humic acids in Amazonia. This species occurs from latitude 3 ° N in Brazil (Perbiche-Neves unpublished data) to southern Argentina (Menu Marque 2001). It can be dominant in eutrophic reservoirs, if conditions are unfavorable for other species. Due to its small size, it may be mistaken for a copepodite. Tropocyclops prasinus meridionalis may co-occur with T. prasinus prasinus, but in the latter species, the caudal rami tend to be slightly longer than in T. prasinus meridionalis 0 In addition, there are differences in the terminal outer and inner spine length of the P 4 - endopod segment, according to Reid (1985). The T. prasinus complex requires an urgent worldwide revision.	en	Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G., da Rocha, and Carlos E. F. (2025): Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America. Zoologia (e 24023) 42: 1-47, DOI: 10.1590/S1984-4689.v42.e24023, URL: https://doi.org/10.1590/s1984-4689.v42.e24023
