Gammaropsis elvirae, Paz-Ríos & Pech, 2019

Paz-Ríos, Carlos E. & Pech, Daniel, 2019, Gammaropsis elvirae sp. nov., a widely distributed amphipod (Amphipoda: Photidae) in the Yucatan Shelf, with ecological comments and a key for the genus in tropical America, Zootaxa 4555 (3), pp. 359-371 : 360-365

Gammaropsis elvirae sp. nov.

( Figs 1–6 )

? Gammaropsis sp. A LeCroy, 2000: 138, fig. 179.

Gammaropsis sp. B LeCroy, 2000: 139, fig. 180. ―in Paz-Ríos & Ardisson, 2013: 153.

Holotype. Male (dissected and drawn), 4.2 mm, northern Yucatan shelf, Yucatan, Mexico, 21.9335°N, 86.9833°W, 25 m, 29 August 2016, coll. A. León-Hernández, ECOSUR0200 .

Paratypes. Gravid female (dissected and drawn), 4.9 mm, northern Yucatan shelf, Yucatan, Mexico, 21.4668°N, 91.3835°W, 44 m, 7 September 2016, coll. S. Balam-Zetina, ECOSUR0201 ; two males and two females (one male dissected and drawn, 3 mm), northern Yucatan shelf, Yucatan, Mexico, 21.8833°N, 89.6336°W, 42 m, 31 August 2016, coll. A. León-Hernández, ECOSUR0202 ; two males (one male dissected and drawn, 3 mm), northern Yucatan shelf, Yucatan, Mexico, 20.7770°N, 90.9584°W, 22 m, 2 December 2012, coll. A. León- Hernández, ECOSUR0203 .

Type locality. Northern Yucatan Shelf, Yucatan, Mexico, 21.9335°N, 86.9833°W.

Etymology. The new species is named after Elvira Maldonado, the beloved wife of the first author, for her unconditional support and passion for marine life.

Diagnosis. Lateral cephalic lobes rounded. Article 2 of mandibular palp longer than article 3. Outer lobes of lower lip with one cone on each lobe. Coxae 2–4 subrectangular, slightly broader than long. Gnathopod 1 propodus longer than carpus. Gnathopod 2, basis, carpus and propodus with a dense marginal fringe of long setae; propodus enlarged with small convoluted processes on posterior margin; palmar margin weakly sinuous, and palmar angle undefined; dactylus short, less than one half in length of propodus, with setae on anterior margin. Epimera 1–3 rounded. Uropods 1–3, inner ramus longer than outer ramus. Telson emarginated.

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Description. Based on holotype male, 4.2 mm, ECOSUR0200. Head with lateral cephalic lobes rounded and strongly produced, subocular cephalic margin strongly recessed, extending behind posterior margin of eye. Eyes ovate. Antennae missing. Upper lip with a small apical notch, pubescent apically. Lower lip inner and outer lobe pubescent apically; outer lobes with one cone on each lobe, inner margin with robust setae and mandibular process well developed with lobes apically acute. Mandible incisor well developed, six-dentate; molar triturative with a short plumose seta; four-toothed lacinia mobilis; accessory setal row with eight dentate setae; palp article 2 longest and setose; palp article 3 spatulate, heavily setose apically, without an apical notch. Maxilla 1 inner plate with apex acute bearing three subapically long slender setae; outer plate with ten serrate robust setae; palp two-articulated, apical part of palp article 2 with five robust and three slender setae subapically. Maxilla 2 inner plate smaller than outer, with a marginal row of long slender setae and an oblique row of setae on the surface; outer plate rounded apically and subapically, with slender setae and lateral margin with pubescence. Maxilliped inner plate with three apical robust setae and an oblique row of plumose setae on surface reaching the apex, outer margin with distal corner bearing one robust setae; outer plate not reaching end of article 2 on palp, with six distal robust setae and three apical plumose setae, outer margin with distal corner bearing one robust setae; palp four-articulate, article 2 longest bearing long slender setae, article 3 with four subapical plumose setae on inner margin, article 4 with one apical serrate seta.

Coxal plate 1 subquadrate; plate 2 subrectangular, about 1.6 times broader than long; plates 3–4 subrectangular, about 1.2 times broader than long; plates 5–6 bilobate, anterior lobe rounded, larger than posterior lobe, expanded distally and bearing several long slender setae; plate 7 subovate with setae on anterior and posterior margins. Gnathopod 1 subchelate, slightly smaller than gnathopod 2; basis with setae on anterior margin; carpus and propodus setose on inner lateral surface; propodus broadly subovate with four robust setae on posterior margin (three robust setae on right propodus, not illustrated) and small processes on posterodistal margin; dactylus falcate, slightly more than two thirds in length of propodus, anterior margin with four setae. Gnathopod 2 subchelate, basis, carpus and propodus with a dense marginal fringe of long setae; propodus enlarged with two small convoluted processes on posterior margin, palmar margin weakly sinuous, with palmar angle undefined; dactylus falcate, less than one half in length of propodus, anterior margin with five setae. Pereopods 3–4 similar in shape, slender; basis linear; carpus subequal in length and width to merus; propodus longer than carpus. Pereopods 5–7 basis slightly expanded, distinctly longer than broad with an anterior marginal row of robust setae; anterodistal and posterodistal corner of basis, merus, carpus, and propodus defined by one or two robust setae; propodus longer than carpus; dactylus bearing a proximal plumose seta.

Epimeral plates 1–3 rounded on the posteroventral corner. Urosomites 1–2 smooth dorsolaterally. Uropod 1 peduncle subrectangular, subequal in length to rami, with four and five robust setae on inner and outer margin, respectively, inter-ramal process well developed; both rami linear and slender with a group of four robust setae on apex, inner ramus slightly longer than outer ramus (more notorious on right ramus, not illustrated). Uropod 2 peduncle shorter than both rami in length, with distal and subdistal robust setae dorsolaterally and a ventral row of three robust setae; both rami linear and slender with a group of four robust setae on the apex, inner ramus longer than outer ramus. Uropod 3 peduncle shorter than both rami in length, with one distal robust setae dorsolaterally; both rami with slender and robust setae on apex; inner ramus longer than outer ramus. Telson emarginate, with the apex of each side bearing three robust setae and one slender setae.

Female (sexually dimorphic characters). Based on paratype female, 4.9 mm, ECOSUR0201. Gnathopod 1 basis strongly narrowing proximally, with short slender setae on anterior and posterior margin; carpus enlarged, subequal in length to propodus; propodus elongate, with three robust setae on ventral margin (two in left gnathopod 1, not illustrated) increasing in size distally, ventrodistal margin evenly rounded and minutely serrate; dactylus falcate, inner margin serrate with 4–5 posterior teeth, outer margin with three slender setae. Gnathopod 2 similar in shape to gnathopod 1; long oostegites, narrow with long marginal setae; propodus with two robust setae on ventral margin and small processes on ventrodistal margin, located at dactylus hinge.

Remarks. Variations from holotype male were observed on a paratype male (ECOSUR0202) with gnathopod 1 propodus (not illustrated) bearing 2–3 robust setae on posterior margin (instead 3–4), a distal palmar margin of gnathopod 2 propodus (illustrated) with small convoluted processes (instead weakly sinuous), and outer margin of gnathopod 2 dactylus with six setae (instead five); on another paratype male (ECOSUR0203) bearing two robust setae on posterior margin of gnathopod 2 propodus (illustrated). Gammaropsis elvirae sp. nov. can be distinguished from all other congeners by the unique combination of characteristics such as the lateral cephalic lobes rounded, outer lobes of lower lip with one cone on each lobe, gnathopod 2 propodus enlarged with small convoluted processes on posterior margin and palmar angle undefined, a dense setation on basis, carpus, and propodus of gnathopod 2, epimeral plates 1–3 rounded, inner ramus longer than outer ramus on uropods 1–3, and telson emarginated. The dense setation on gnathopod 2 is a remarkable characteristic presents in other congeners as G. arawakia , G. setifera (Schellenberg, 1938) , G. shoemakeri , G. thompsoni , G. tonichi , and G. tawahi Barnard, 1972 , but, G. elvirae sp. nov. is differentiated from all these species (except from G. setifera ) by the following characteristics (but not limited to these): lateral cephalic lobes rounded (acute on those species) and epimeral plate 1–3 rounded (notched or toothed on those species). It differs from G. setifera by palm gnathopod 1–2 evenly round (convex, defined by a middle tooth on G. setifera ); rami uropod 3 longer than peduncle (rami subequal in length to peduncle on G. setifera ); telson emarginated (entire and triangularly hollow posteromedially on G. setifera ). The new species resembles G. dubia in the head recession; lateral cephalic lobes rounded; shape of female gnathopods 1–2; epimera 1–3 rounded; uropod 3, inner ramus longer than outer ramus, but it is differentiated by inner plate on maxilla 1 with apex acute (rounded on G. dubia ); carpus gnathopod 1 shorther than propodus (carpus subequal than propodus on G. dubia ); propodus gnathopod 2 slightly larger than gnathopod 1 and dactylus short (both propodus and dactylus gnathopod 2 greatly enlarged on G. dubia ), telson emarginated (telson entire on G. dubia ). The presence of robust setae on posterior margin of gnathopod 2 propodus is a shared feature with juvenile males of Gammaropsis dentata Chevreux, 1900 (a very different species to G. elvirae sp. nov.), however, this feature disappears on the adult stage. The loss of robust setae due a morphological variation in the propodus of gnathopod 2 in males during its development is a signal of an ontogenetic change from juvenile to adult. The new species shows a close similarity with a generic species ( Gammaropsis sp. A) identified by LeCroy (2000) from southern Florida, but, is distinguished by the relatively elongated article 2 of mandibular palp (relatively stout in Gammaropsis sp. A), propodus longer than carpus in peraeopods 3–4 (subequal to carpus in Gammaropsis sp. A), and presence of small convoluted processes on posterior margin of gnathopod 2 propodus (processes absent in Gammaropsis sp. A). Regarding this last characteristic, LeCroy (2000) suggested that probably the gnathopod 2 illustrated for males of Gammaropsis sp. A is for younger specimens, that eventually, could be well developed with small convoluted processes on posterior margin, as in G. elvirae sp. nov.

Figures

FIGURE 1. Habitus of Gammaropsis elvirae sp. nov., holotype male, 4.2 mm, ECOSUR0200; northern Yucatan shelf, Yucatan, Mexico. Scale bar represents 1 mm. Photography provided by Daniela Ríos-Elósegui.

FIGURE 2. Gammaropsis elvirae sp. nov., holotype male, 4.2 mm, ECOSUR0200; northern Yucatan shelf, Yucatan, Mexico. Scale bar for H represents 1 mm; scale bars for G1 and G2 represent 0.3 mm.

FIGURE 3. Gammaropsis elvirae sp. nov., holotype male, 4.2 mm, ECOSUR0200; northern Yucatan shelf, Yucatan, Mexico. Scale bars represent 0.1 mm.

FIGURE 4. Gammaropsis elvirae sp. nov., holotype male, 4.2 mm, omitted setae on G1 and G2; ECOSUR0200; northern Yucatan shelf, Yucatan, Mexico. Scale bars represent 0.3 mm.

FIGURE 5. Gammaropsis elvirae sp. nov., holotype male, 4.2 mm, ECOSUR0200; G2’, paratype male, 3 mm, ECOSUR0203; G2’’, paratype male, 3 mm, ECOSUR0202; northern Yucatan shelf, Yucatan, Mexico. Scale bars for G2’and G2’’ represent 0.3 mm; scale bars for U1, U2, U3, and T represent 0.2 mm.

FIGURE 6. Gammaropsis elvirae sp. nov., paratype female, 4.9 mm, ECOSUR0201; northern Yucatan shelf, Yucatan, Mexico. Scale bars represent 0.1 mm.