Hyalella villalobosi, Marrón-Becerra & Hermoso-Salazar, 2022

Marrón-Becerra, Aurora & Hermoso-Salazar, Margarita, 2022, Morphological comparison and description of five new species of Hyalella (Crustacea: Amphipoda) from Veracruz and Mexico City, Journal of Natural History 56 (25 - 28), pp. 1215-1263 : 1239-1245

publication ID	https://doi.org/ 10.1080/00222933.2022.2078241
publication LSID	lsid:zoobank.org:pub:9DF27EA5-D5DD-4010-9092-CB6BB358E6B7
DOI	https://doi.org/10.5281/zenodo.7102153
persistent identifier	https://treatment.plazi.org/id/0207BC20-8C52-7B52-CBCE-FF1C4FBCFB43
treatment provided by	Plazi
scientific name	Hyalella villalobosi
status	sp. nov.

Treatment

Hyalella villalobosi sp. nov.

http://www.zoobank.org/ urn:lsid:zoobank.org:act:E4237141-1948-4D18-A6F3-7AFB6F5592F8

( Figures 11–13 View Figure 11 View Figure 12 View Figure 13 )

Etymology. The new species is named in honour of Dr José Luis Villalobos Hiriart, in recognition of his valuable and outstanding contributions to the marine and freshwater carcinology of Mexico.

Material examined. Holotype male, size 5.4 mm (Cat. No. CNCR 35729 ), from Lake Catemaco in state of Veracruz, Mexico (18.366°N, 95.084°W), 24 July 2015, 337 m a.s.l., temp. 34°C, pH 7. Collectors: A. Marrón-Becerra, E. Lemus-Santana and M. HermosoSalazar. GoogleMaps Paratypes (n = 30 males, n = 30 females): males – mean body total length 5.1 ± 0.5 mm, mean head length 0.6 ± 0.03 mm (n = 27), females – mean body total length 4.5 ± 0.5 mm, mean head lenght 0.5 ± 0.04 (n = 30) (permanent slides Cat. No. CNCR 35739 , paratypes and SEM preparations CNCR 35740 ), locality same as holotype GoogleMaps .

Type locality ( Figure 1 View Figure 1 ). Lake Catemaco GoogleMaps , state of Veracruz, Mexico (18.366°N, 95.084°W).

Diagnosis. Pleonite 1 and 2 with dorsoposterior carina. Coxa 4 excavated posteriorly. Eyes pigmented. Antenna 1 shorter than antenna 2. Antenna 2 less than half body length. Maxilla 1 palp short, overreaching half of length between base of palp and base of setae in outer plate, with 1 short stout distal seta and setules; inner plate slender with 3 strong pappose distal setae. Maxilla 2 inner plate with 2 strong pappose setae on inner margin. Gnathopod 1, propodus hammer shaped, palm slope transverse, inner face with 2 pappose setae, comb scales on distoposterior and distoanterior border, carpus inner face lobe with 5 pappose setae. Gnathopod 2, basis hind margin with 1 medial seta, excavation of palm wide. Uropods without curved setae. Uropod 3, peduncle longer than ramus, styliform. Telson as long as wide, distal margin acute, with 2 long simple apposed setae. Coxal gills on segments 2–6. Sternal gills on segments 3–7.

Description

Body ( Figures 11a View Figure 11 , and 18a View Figure 18 ), tergites of pleon 1 and 2 with dorsoposterior carina. Epimeral plates 1–3 slightly acuminate. Coxae 1–3 ( Figures 11a View Figure 11 , and 18a View Figure 18 ) subequal in shape, subrectangular, longer than wide; coxa 1 shorter than coxae 2–3; coxa 4 wider than coxae 1–3 with deep posterior excavation, acumination absent; coxa 5 with two subequal lobes, anterior lobe slightly shorter than posterior; coxa 6 anterior lobe reduced; coxa 7 anterior lobe absent.

Head typically gammaridean ( Figures 11a View Figure 11 , and 18a View Figure 18 ), shorter than first two thoracic segments, rostrum absent. Eyes pigmented, medium, rounded, located between insertions of antennae 1 and 2.

Antenna 1 ( Figure 11a–b View Figure 11 ) less than half the body length, shorter than antenna 2, but longer than peduncle of antenna 2, almost reaching to middle of third pereonite; peduncle longer than head, reaching to middle of length of first pereonite; article 1 and 2 subequal in length, article 1 wider than articles 2–3, article 2 longer and wider than article 3, proportions (1.3:1.26:1), article 1 with 3 short setae, 1 smaller, and one cluster with 3 cuspidate setae ventrally at distal end, articles 1–3 mid-ventral margin with slender setae; flagellum longer than peduncle with 9 articles gradually shorter towards distal portion; aesthetascs on flagellum, present on articles 2–6 (one pair), 7–8 (one).

Antenna 2 ( Figure 11a, c View Figure 11 ) almost 1.27 times longer than antenna 1, reaching one-third body length, reaching fourth pereonite; peduncle reaching second pereonite, peduncle articles increase gradually in length and decrease in width; article 3 shorter but wider than 4 and 5, article 4 longer than article 3, article 5 slightly longer than article 4; flagellum with 8–10 articles slightly longer than peduncle (subequal), without aesthetascs.

Buccal parts: upper lip ( Figure 11f View Figure 11 ), distal margin rounded with numerous setules.

Lower lip ( Figure 11g View Figure 11 ) subquadrate, outer lobes without notches or excavations; mandibular projection of outer lobes rounded.

Mandibles ( Figure 11h–i View Figure 11 ) without palp, asymmetric. Incisor toothed, 6 teeth present. Left lacinia mobilis, with 5 teeth; setal row on left mandible with 3 main pappose setae plus accessory setae. Right mandible with 6 teeth, right lacinia mobilis reduced than left, with 2 pairs of asymmetric L-shape teeth; setal row on right mandible with 2 main pappose setae plus accessory setae and with setulae near molar process. Both molar processes large, cylindrical and triturative, with accessory pappose setae.

Maxilla 1 ( Figures 11d View Figure 11 , and 19e View Figure 19 ), palp vestigial, uniarticulate, longer than wide, distally pointed and with 1 distal stout distal seta (A 5 type), setules present; palp length overreaches half of the distance between base of palp and base of seta on outer plate, or reaching to middle; inner plate slender, shorter than outer plate, with 3–4 pappose distal setae (2 distal and 2 subdistal); outer plate with 9 distal stout serrate setae and with setules.

Maxilla 2 ( Figure 11e View Figure 11 ) plates subequal; inner plate shorter and slender with 2 pappose setae on mid-distal inner margin, and with 6 serrulate setae on distal margin; outer plate without serrate setae but with 2 long pappose setae; outer and inner plates with abundant large simple setae (type A2) and setules on both distal surfaces and margins.

Maxilliped ( Figures 11j View Figure 11 , and 20e View Figure 20 ) inner plate lobe longer than outer plate lobe; distal margin slightly convex; inner plate distal margin with 3 cuspidate setae of equal size and with plumose setae, inner margin with several pappose setae; outer plate, inner and distal margins with numerous simple setae. Palp composed of four articles subequal in maximum length; first article with 2 simple setae at the inner distal end and 1 seta at outer distal end; second article with numerous simple setae on inner margin and 1 on outer distal end; third article with several long setae on distal margin, outer margin with 1 simple seta and comb scales, inner margin with 5 setae and 5 at distal end; fourth article unguiform slightly longer than nail, with comb scales, inner margin near distal half with 3 setae, and 2 setae near nail base on outer margin; nail exceeds two-thirds of fourth article, with serration at distal half.

Gnathopod 1 ( Figure 12a View Figure 12 ) subchelate, hammer shaped. Basis elongated, maximum length almost 3 times longer than maximum width posterior margin with 2 setae, distal end without cluster of setae. Ischium short, subquadrate; distal posterior end with one cluster of 2 setae. Merus longer than wide, ventral surface with comb scales; distal margin with 8 setae. Carpus longer than wide, longer than propodus; with strong, short, and wide posterior lobe forming one scoop-like structure open to inside; inner surface with 5 serrate setae. Propodus less than 1.5 times longer than wide (1.36 times); inner surface near distal margin with 2 serrate setae in one row, distal anterior end with 2 clusters of approximately 8 setae; distal anterior and posterior surfaces with comb scales; palm transverse, posterior distal end with 1 robust seta and cup for dactylus. Dactylus clawlike; nail present; with 1 plumose seta, with comb scales.

Gnathopod 2 ( Figures 12b View Figure 12 , and 21e View Figure 21 ) subchelated; palm slightly oblique. Basis elongate, more than 3 times longer than wide; posterior margin with 0–1 medial seta. Ischium short, subquadrate, shorter than merus. Merus short, posterior margin with 8 simple setae, posterior inner and outer surfaces with comb scales. Carpus shorter than propodus; anterodistal end with 6 setae; posterior lobe scoop-like, elongate, length similar to merus maximum length, almost 1.5 times width of merus, with several submarginal pappose setae and comb scales. Propodus robust, almost 1.5 times as long as wide, subrectangular; palm similar length to or slightly longer than posterior margin; slope slightly irregular, with several long simple setae, and some short and medium setae; distal margin of palm with one truncated process near insertion of dactylus, and with wide posterior excavation at base ( Figure 22e View Figure 22 ); palm posterior distal end with 2 strong setae, comb scales and cup for the dactylus. Dactylus claw-like, congruent with palm without comb scales; outer margin with 1 plumose seta; inner margin crenulated, with setules.

Pereopods 3–7 ( Figure 12e–i View Figure 12 ) simple, gradually longer posteriorly. Pereopod 5 slightly shorter than 4 and 6.

Pereopod 3 ( Figure 12e View Figure 12 ) basis elongate; mid-posterior margin without simple seta. Merus anterior margin almost at half with 1 seta; posterior margin with 3 long simple setae; anterodistal and posterodistal ends with one cluster of 4 and 7 setae, respectively. Carpus slightly shorter and slenderer than merus; posterior margin with 2 stout setae plus accessory setae; posterodistal end with at least 7 slender setae, anterodistal end with at least 6 setae. Propodus, slenderer than carpus; posterior margin with 3 stout setae; anterodistal end with 5 simple setae. Dactylus claw-like; length less than half of propodus; nail present.

Pereopod 4 ( Figure 12f View Figure 12 ) similar in shape to pereopod 3 but slightly longer; coxa 4 wider than coxa 3 with posterior excavation; basis posterior margin without simple seta; merus mid-anterior margin without setae; propodus posterior margin with 3 stout setae.

Pereopods 5–7 ( Figure 12g –i View Figure 12 ) similar in shape; basis posterior lobe rounded and denticulated. Pereopod 7 ( Figure 12i View Figure 12 ) basis lobe widely expanded, overreaching ischium distal margin; basis lobe width 1.7 times as wide as basis (measured at cleft between basis and basis lobe); posterior margin with 13 serrations with setules and without stout seta on distal margin; anterior margin with 2 stout setae and one cluster of 2 setae at distal end. Dactylus length almost one-third of propodus length.

Pleopods 1–3 ( Figure 13e View Figure 13 ) not modified, biramous, elongated, rami multi-annulated, with numerous plumose setae; pleopod 1, inner margin of peduncle at distal end with 2 short retinacula (coupling hooks).

Uropod 1 ( Figure 13a View Figure 13 ) longer than uropod 2; peduncle longer than rami, dorsal margin with 2 dorsal setae, inner and outer distal ends each with 1 seta; rami subequal, inner ramus slightly longer, with 2 dorsal and 5 distal setae; outer ramus with 2 dorsal and 3 distal setae; male without curved setae on inner ramus.

Uropod 2 ( Figure 13b View Figure 13 ) as long as peduncle of uropod 1; peduncle shorter than outer rami, with 1 dorsal seta and 1 seta at distal end; rami subequal, inner ramus slightly longer with 2 dorsal and 6 distal setae, outer ramus with 2 dorsal and 4 distal setae.

Uropod 3 ( Figures 13c View Figure 13 , and 23e View Figure 23 ) slightly longer than or as long as peduncle of uropod 2; peduncle rectangular, wider than ramus, with 5 strong distal setae of variable length; inner ramus absent; outer ramus uniarticulate, slender, slightly shorter than peduncle; basal width almost 3 times width of apex of ramus, with 3 slender apical setae (one longer) and 1 connate seta.

Telson ( Figures 13d View Figure 13 , and 24e View Figure 24 ) entire, longer than wide, distal margin pointed or truncated, with 2 long simple apposed setae; outer surface bearing two clusters of 3 plumose setae, near margin, symmetrically distributed.

Coxal gills sac-like, present on segments 2–6. Sternal gills tubular, present on segments 3–7.

Female ( Figure 18b View Figure 18 ) similar to male. Gnathopod 1 ( Figure 12c View Figure 12 ), carpus with 7 serrate setae on inner face lobe; propodus with 4 serrate setae in row over inner face. Gnathopod 2 ( Figure 12d View Figure 12 ) smaller than male gnathopod 2, parachelated, palm reverse oblique, basis posterior margin without seta; propodus longer than twice maximum width, inner face with 4 serrate setae in a row and 1 simple seta, outer face with 4 setae in one row and 3 large setae near palm, anterior and posterior distal half with comb scales. Pereonite 2 with anterior excavation or notch for amplexus. Pereopod 7 lobes with 11 serrations and setules, and without stout setae on distal margin. Oostegites subtriangular with curled setae on margins.

Habitat. Freshwater, epigean, littoral, associated with sediment and Eichhornia crassipes (Mart.) Solms.

Distribution. Lake Catemaco, state of Veracruz, Mexico (18.366°N, 95.084°W).

Remarks

This species has parasites of the genus Lagenophrys , possibly Lagenophrys patina (Stokes, 1887) ; they are abundant in the coxae and the basis of pereopods; the protozoos are even attached to the setae.

This species is morphologically similar to H. azteca , with two dorsal mucronations on the pleon and the telson with the distal margin acute with 2 distal apposed setae. But this species differs in the following: telson is longer than wider, isquium is longer than its width, uropod 2 is similar in length to peduncle of uropod 1, peduncle is shorter than ramus in uropod 2, and this species has more articles in the antennae despite its shorter size ( Tables 1, S1 View Table 1 ).