Pseudochydorus margaritalfonsorum, Sinev & Silva-Briano, 2021

Sinev, Artem Y. & Silva-Briano, Marcelo, 2021, A new species of scavenger Cladocera Pseudochydorus Fryer, 1968 (Cladocera: Anomopoda: Chydoridae) from the Central Mexican Plateau, Zootaxa 5039 (4), pp. 551-560 : 552-557

publication ID	https://doi.org/ 10.11646/zootaxa.5039.4.6
publication LSID	lsid:zoobank.org:pub:68373271-626A-4AFB-9CAC-4EBD66C47276
persistent identifier	https://treatment.plazi.org/id/4C0F87BA-FFF0-FFF4-FF58-FB0BFC72C43A
treatment provided by	Plazi
scientific name	Pseudochydorus margaritalfonsorum
status	sp. nov.

Treatment

Pseudochydorus margaritalfonsorum sp. nov.

Elías-Gutiérrrez, Suárez-Morales, Gutiérrez-Aguirre, Silva-Briano, Granados-Ramírez & Garfias-Espejo, 2008: 45–46, Fig. 29.6, 30.1–2 ( cf. globosus ).

Type locality: reservoir near San Miguel de los Sandovales town , El Llano, Aguascalientes, México, 21° 53’ 5.87” N, 102° 06’ 22.60” W, 12.10.1991 GoogleMaps .

Type material. Holotype. Parthenogenetic female from the type locality, Zoological Museum of M. V. Lomonosov Moscow State University Ml-247.

Paratypes. Two adult parthenogenetic females and four juvenile females from the type locality, Zoological Museum of M. V. Lomonosov Moscow State University , Ml-248. About twenty more females from the type locality and numerous exuvia were dissected for the analysis of appendages or used in SEM studies .

Etymology. The species name honors the memory of a couple of our friends and colleagues, Margarita Palacio Núñez and Alfonso Salado Rodríguez, who died a few years ago.

Description. Parthenogenetic female. Body of preserved specimens yellowish, with brownish pigment spot at the middle of the valves. In lateral view body almost round ( Fig. 1A–C View FIGURE 1 , 2A–C View FIGURE 2 ); height/length ratio about 0.9, maximum height at the middle of the body. Body globular, only weakly compressed laterally ( Fig. 2E View FIGURE 2 ).

Valves with broad flattened flange going from the middle of ventral margin to the posterodorsal corner. Anterior corner broadly rounded. Ventral margin ( Fig. 1D View FIGURE 1 ) with about 80 setae located on the inner side of the valves. Postero-ventral corner without denticles. Valves, except posteroventral flange, covered by polygonal sculpture, and unlike in other species of the genus, there are no depressions inside the polygons.

Head with moderately long rostrum, pointing down. Length of rostrum (measured from tip to the level of mandibular articulation point) about 0.33–0.36 height of the body. Diameter of ocellus 2.5 times smaller than diameter of eye. In adults, distance between ocellus and tip of the rostrum is about 1.5 distance between ocellus and center of the eye. Head shield ( Fig. 1E View FIGURE 1 , 2F View FIGURE 2 ) large, with maximum width at the middle of posterior portion; its posterior portion wide oval. Rostrum with elongated blunt tip ( Fig. 1F View FIGURE 1 ). Head shield with polygonal sculpture, less pronounced than on valves. Head pores typical for Chydorinae morphology ( Fig. 1G View FIGURE 1 , 2G View FIGURE 2 ), PP about 2 IP. Labrum with reduced labral keel.

Postabdomen ( Fig. 1H–I View FIGURE 1 , 2H–I View FIGURE 2 ) long and narrow, in postanal portion with parallel margins or weakly narrowing distally; maximum height at postanal angle. Length about 3.5–4 height. Ventral margin straight. Basis of claws separated from distal margin by clear incision. Distal margin weakly convex, distal angle rounded. Dorsal margin almost straight in postanal portion, strongly concave in anal portion, concave in preanal portion. Distal (anal + postanal) part 2–2.5 times longer than the preanal portion. Postanal portion 1.5–1.8 times longer than anal portion. Preanal angle well expressed, prominent; postanal angle weakly defined. About 12 narrow sharp denticles, decreasing in size basally, at postanal margin; some of them with additional smaller denticles basally. Length of longest denticles little more than width of the postabdominal claw base. Postanal portion with row of 7–8 lateral fascicles of short setulae, sometimes with several additional fascicles above them; distalmost fascicles consisting of 1–6 thick setulae only, in basal portion fascicles consist of more than 10 longer and thinner setulae. Postabdominal claw ( Fig. 2J View FIGURE 2 ) long, slender, curved, slightly longer than preanal portion of postabdomen; two basal spines, distal spine about 0.2 length of the claw, proximal spine 4 times shorter.A pecten of short spinules on dorsal side of claw; in basal part spinules thicker and spaced more sparsely than in distal part. A row of very thin short setulae along ventral margin of claw which can be observed only at high magnification.

Antenna I ( Fig. 1J View FIGURE 1 ) large, massive; length about 1.5 widths. Antennular seta long, about half length of antennule itself, arising almost at 1/2 distance from the base of antennule. Nine terminal aesthetascs, longest ones as longer as antennule.

Antenna II relatively short ( Fig. 1K View FIGURE 1 ). Antennal formula: setae 0-0-3/1-1-3; spines 1-0-1/0-0-1. Basal segment robust, with very short seta between branches. Branches slender; endopodite longer than exopodite; in both branches basal segment 2 times longer and thicker than the two others. Seta arising from basal segment of endopodite reaching to the middle of apical segment. Seta arising from middle segment of endopodite of similar size of apical setae. Apical setae of the exopodite have similar thickness and length, one apical seta of endopodite much shorter and thicker than two others. All spines are very short.

Mandibles typical for the subfamily. Maxillae ( Fig. 1L View FIGURE 1 ) with three slender setae armed with spinules; two shorter setae 2 times shorter than the longest one.

Trunk limb I larger than others ( Fig. 3A–E View FIGURE 3 ). Epipodite oval, without projection. ODL with two setae, one of them very small. IDL with three setae, a row of long setulae and two rows of short thick spines. IDL seta 1 very thick, hook-like, about 1/2 length of longest ODL seta, with a row of spinules at the middle; seta 2 about 2/3 length of longest ODL seta; seta 3 little shorter than longest ODL seta; setae 2–3 armed with thick spinules in distal part. Endite 3 with four setae, inner seta (1) short, with shortened distal portion, armed with 5–7 long setulae longer than distal portion of seta; outer setae (a–c) of same morphology much longer than inner seta (1), armed with 2–3 thick spines on one side and with numerous small spinules on other side. Endite 2 with inner seta (2) as long as setae a–c, and three outer setae (d–f); seta d similar in shape and armament to setae a–c, but longer; setae e–f long, slender, in basal portion armed unilaterally with long setulae, and in distal portion bilaterally with spinules. Endite 1 with single two-segmented seta (g) and a naked inner seta (3) on anterior face of limb; seta h absent. Five rows of thin long setulae on ventral face of limb. Two thin ejector hooks of similar size.

Trunk limb II subtriangular ( Fig. 3F–G View FIGURE 3 ). Exopodite small, rounded, exopodites very long, as long as scraping spine 1. Eight scraping spines; spines 1–3 long, decreasing in size basally, armed with small denticles; spines 4–8 shorter, decreasing in size basally; spines 4–5 and 8 armed with small spinules; spines 6–7 with short setulae. Two small setae or sensillae located between spines 3–4. Distal armature of gnathobase with four elements. Gnathobase filter plate with five setae, distalmost setae (1–2) short, of similar length, oriented toward scraping spines, setae 3–5 two times longer than setae 1–2, pointed dorsally.

Trunk limb III ( Fig. 3H–J View FIGURE 3 ). Epipodite oval, without projection. Exopodite narrow, rectangular, with three lateral (1–3) and four terminal (4–7) setae. All setae rather short, seta 4 being longest, only 1.5 times longer than exopodite itself. Seta 5 slightly shorter than seta 4; seta 6 about 2/3 length of seta 4; seta 1 and 7 about 1/2 the length of seta 4; setae 2 and 3 very short. Setae 1–5 plumose; setae 6 armed with long setulae in basal portion and with very short setulae in distal portion; seta 7 unilaterally armed with very short setulae. Distal endite with three scraping setae (1–3), slender, sharp, with small denticles in distal part; seta 2 longer than the two others. Basal endite with 4 setae (a–d), seta a three times shorter than setae b–d. Three short inner setae (4–6), a small bottle-shaped sensillum near the distalmost seta. Distal armature of gnathobase with three elements: a longer seta and two spines. Gnathobase filter plate with five setae, oriented in opposite directions.

Limb IV ( Fig. 3K–N View FIGURE 3 ). Pre-epipodite setulated; epipodite oval, without projection. Exopodite oval, with seven setae; seta 1 being longest; length of setae decreases evenly from seta 1 to seta 6; seta 7 about half length of seta 6; setae 1–6 plumose, seta 7 naked. Inner portion of limb IV with three setae and large sensillum; scraping seta (1) long and slender, setae 2–3 reduced to the small spines, seta 4 absent. Two inner setae (a–b) of similar size. Gnathobase with one two segmented setae (gbs) and two small spines or sensillae. Gnathobase filter plate with four setae.

Limb V ( Fig. 3O View FIGURE 3 ). Pre-epipodite setulated; epipodite oval, without projection. Exopodite large, oval, with four plumose setae decreasing in length basally; seta 4 about 2/3 length of seta 1. Inner lobe narrow oval, with several clusters of long setulae on inner margin. Inner face with two setae; distal seta 2 very short, curved, two times shorter than the basal one. Gnathobase filter plate with two setae.

Ephippial female and male unknown.

Size. In instar I juvenile female length was 0.34–0.35 mm, height 0.27–0.29 mm; in instar II juvenile female length 0.37–0.41 mm, height 0.30–0.34 mm; in adult parthenogenetic female length 0.44–0.55 mm, height 0.40– 0.47mm.

Differential diagnosis. Pseudochydorus margaritalfonsorum sp. nov. differs from both P. bopingi ( Fig. 4 A–D View FIGURE 4 ) and P. globosus ( Fig. 4E–H View FIGURE 4 ) in: (1) the endite 1 of limb I without seta h, seta which is present in both Old World species ( Fig. 4A, 4E View FIGURE 4 ); (2) in inner seta 1 of endite 3 of limb I being short, with shortened distal portion, armed with 5–7 long setulae, in both these species seta 1 is long, with long distal portion, armed with over 10 short setulae ( Fig. 4B, 4F View FIGURE 4 ); (3) in scrapers 6–7 of limb II armed with short setulae instead of long ones, in shorter scraper 8, and in scrapers 1–4 armed with much smaller spinules, than in both Old World species ( Fig. 4 View FIGURE 4 С, 4G); (4) in gnathobase filter plate II with distalmost setae (1–2) being short, of similar length, much shorter than setae 3–5, in both Old World species seta 2 is much longer than seta 1, of similar length to setae 3–5 in P. globosus ( Fig. 4G View FIGURE 4 ), and longer than setae 3–5 in P. bopingi ( Fig. 4C View FIGURE 4 ); (5) in short scraping setae (1–3) of distal endite of limb III, with seta 2 being only slightly longer than other, in both Old World species these setae are much longer than in P. margaritalfonsorum sp. nov., seta 1 being longest, almost 2 times longer than seta 3 ( Fig. 4D, 4H View FIGURE 4 ). It also differs from P. globosus in much smaller size, length of P. globosus female is up to 0.8 mm.

Distribution. P. margaritalfonsorum sp. nov. is widely distributed in Aguascalientes State, and also in the states of Mexico, Durango and Tlaxala of the Mexican Republic. The list of localities is recorded in Table 1. It was not recorded in the rest of the country ( Elías-Gutiérrrez et al. 2008).