Leptochelia mexicana, Jarquín-González, Jani, García-Madrigal, María Del Socorro & Carrera-Parra, Luis Fernando, 2015

Jarquín-González, Jani, García-Madrigal, María Del Socorro & Carrera-Parra, Luis Fernando, 2015, First species of Leptochelia Dana, 1849 (Crustacea: Tanaidacea) from the Eastern Pacific, with an annotated checklist and identification keys for the genus, Zootaxa 3920 (4), pp. 501-533 : 510-516

publication ID	https://doi.org/ 10.11646/zootaxa.3920.4.1
publication LSID	lsid:zoobank.org:pub:2E0EB0EB-0019-4FCF-8204-E748A7511A3F
DOI	https://doi.org/10.5281/zenodo.5463401
persistent identifier	https://treatment.plazi.org/id/0B3AD532-A641-7E60-9BB1-C11E0874E5D8
treatment provided by	Plazi
scientific name	Leptochelia mexicana
status	sp. nov.

Treatment

Leptochelia mexicana View in CoL n. sp.

Figs 2‒5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Leptochelia cf. dubia Jarquín-González & García-Madrigal (2010) View in CoL : 55–56, figs 2D–E.

Material examined. Holotype —adult male (UMAR-Pera 015), 2.2 mm, Coral Beach, Ixtapa Island, Guerrero, Mexico, rocks with algae in pool tide, littoral, 19 September 2007.

Paratypes —19 ovigerous females, 132 non-ovigerous females, 15 males, 58 juveniles (UMAR-Pera 485), same data as holotype.

Diagnosis. Male. Cephalothorax similar in length to pleon, rounded. Antennule less than ½ the length of body; flagellum with eight articles. Cheliped about ¾ the length of the body; cutting edge of fixed finger with two blunt unequal processes widely separated; carpus is wider proximally, four times longer than wide; dactylus slightly longer than fixed finger. Pereopods 2–3 with a row of setules distally on propodus. Endopod of uropod with a strong spiniform seta on second article. Female. Cephalothorax longer than pleon, suboval. Antennule with article 1 about three times longer than wide; article 2 slightly longer than article 3. Basis of maxilliped with five distal setae. Cheliped with three dorsal setae on carpus; fixed finger with three processes. Exopod of uropod uniarticulate, shorter than first article of endopod.

Description. Adult male, 2.2 mm ( Fig. 2 View FIGURE 2 A). Body slender, about six times longer than wide. In dorsal view, cephalothorax rounded and slightly narrowing; approximately 1/5 the length of body. Eyes with dark pigments. Pereon about 3/5 the length of body; fourth pereonite longer and wider than others pereonites. Pleon similar in length to cephalothorax. Pleotelson with posterior margin rounded and two pairs of setae.

Antennule ( Fig. 2 View FIGURE 2 B) less than a half the length of body; with three basal articles and flagellum with eight articles. Article 1 approximately five times longer than wide, with two simple distal setae. Article 2 about 1/2 the length of article 1, with two simple setae and a plumose distal seta. Article 3 approximately 1/5 the length of article 1.

Antenna ( Fig. 2 View FIGURE 2 C) with six articles. Article 1 small, without setae. Article 2 is the broadest of all, with three setae. Articles 2 and 3 with similar length. Article 4 about six times longer than wide, with three distal setae. Article 5 seven times longer than wide, with two distal setae. Article 6 minute, with three long setae.

Mouthparts reduced.

Cheliped ( Figs 2 View FIGURE 2 D–E) more than 1/2 the length of body; basis short and stout; merus wider than long; carpus four times longer than wide; propodus with inner comb-like row of about 16 setae and a separate longer seta near articulation with dactylus; fixed finger similar in length to dactylus, with two unequal inner processes widely separated and five distal setae; dactylus ventral margin smoothly-curved, crenulated proximally, with row of ten very short setae.

Pereopod 1 ( Fig. 2 View FIGURE 2 F) with basis slender and a short inner seta on basis; merus longer than carpus, merus with three distal setae; carpus shorter than propodus, carpus with six distal setae; propodus about five times longer than wide, with a row of setules and four distal setae; dactylus and unguis together shorter than propodus.

Pereopod 2 ( Fig. 3 View FIGURE 3 A) with basis slender and a long inner seta on basis; merus similar in length to carpus, merus with two distal setae; carpus shorter than propodus, carpus with four setae and two small spiniform distal setae; propodus about three times longer than wide, with a row of setules, two setae and a spiniform seta distally; dactylus slightly stout, with a row of setules.

Pereopod 3 ( Fig. 3 View FIGURE 3 B) with basis slender and a long inner seta on basis; merus shorter than carpus, merus with two distal setae; carpus shorter than propodus, carpus with four setae and a small spiniform distal seta; propodus about three times longer than wide, with a row of setules, two setae and a spiniform seta distally; dactylus slender, with a row of setules.

Pereopod 4 ( Fig. 3 View FIGURE 3 C) with basis stout and without setae; merus similar in length to carpus, merus with two spiniform distal setae; carpus shorter than propodus, carpus with two unequal spiniform setae on dorsal surface and a spiniform seta on ventral surface; propodus five times longer than wide, with medial scales, two spiniform setae and four distal setae; dactylus and unguis fused into a stout claw, with a row of setules.

Pereopod 5 ( Fig. 3 View FIGURE 3 D) similar to pereopod 4, but merus longer than carpus. Pereopod 6 ( Fig. 3 View FIGURE 3 E) similar to pereopod 5, but propodus about four times longer than wide, with a long seta and a row of six setulae.

Uropod ( Fig. 3 View FIGURE 3 F) with six setae on dorsal surface of protopod; exopod uniarticulate, shorter than article 1 of endopod; with two long terminal setae, one of theme extending until the article 5 of endopod; endopod with five articles, second article with a strong spiniform medial seta.

Ovigerous female, 2.8 mm ( Fig. 4 View FIGURE 4 A). Body about six times longer than wide; cephalothorax nearly oval, 1/5 the length of body; with pointed eyes. Pereon approximately 3/5 the length of body; pereonite 4 wider than all. Pleon shorter than cephalothorax. Pleotelson with posterior margin rounded, slightly extended, with two pair of simple setae and two plumose setules.

Antennule ( Fig. 4 View FIGURE 4 B) with four articles. Article 1 about three times longer than wide. Article 2 slightly longer than article 3. Article 4 minute, with five distal setae and an aesthetasc.

Antenna ( Figs 4 View FIGURE 4 C–D) with six articles. Article 1 short (not drawn). Article 2 longer than article 3, with two spiniform setae and a simple seta. Article 3 with a spiniform seta. Article 4 about four times longer than wide, with four simple setae. Article 5 about two times longer than wide. Article 6 minute.

Mouthparts. Labrum ( Fig. 4 View FIGURE 4 E) rounded and expanded, setulose distally. Right mandible ( Fig. 4 View FIGURE 4 F) with four denticles in lacinia mobilis, pars incisiva with smooth apex, molar robust, with rugose distal ridges and fine serrated denticles; left mandible ( Fig. 4 View FIGURE 4 G) with lacinia mobilis and pars incisiva crenulate distally, molar robust, with ten serrated denticles. Labium ( Fig. 4 View FIGURE 4 H) with two pairs of lobes, both finely setulose; outer lobe slightly shorter than inner lobe. Maxillule ( Fig. 4 View FIGURE 4 I) apex with six distal spiniform setae, setulose distally; palp with two terminal simple seta. Maxilliped ( Fig. 4 View FIGURE 4 J) basis with five long setae, extending until the middle of palp article 3; palp article 1 short and wide; article 2 with four setae and numerous setules; article 3 with six ventral setae; article 4 with nine setae; endite ( Fig. 4 View FIGURE 4 K) with three flat setae, dorsal surface setulose and with a long simple seta.

Cheliped ( Fig. 5 View FIGURE 5 A) with basis slightly longer than wide, dorsal surface with a seta. Merus short, with three unequal setae. Carpus wide distally, with three distal setae. Propodus with four small setae near to the articulation with dactylus. Fixed finger with three processes and five distal setae; dactylus inner margin smoothly-curved, without setae.

Pereopod 1 ( Fig. 5 View FIGURE 5 B) basis with proximal seta. Merus longer than carpus, merus with a small seta. Carpus with six distal setae. Propodus less than four times longer than wide, with four distal setae. Dactylus long and slender; dactylus and unguis together almost as long as propodus.

Pereopod 2 ( Fig. 5 View FIGURE 5 C) basis with three setae. Merus shorter than carpus, merus with two setae. Carpus with a small spiniform seta, outer margin setulose. Propodus about twice longer than wide, with four distal setae, dorsal surface setulose. Dactylus and unguis together about ½ the length of propodus.

Pereopod 3 ( Fig. 5 View FIGURE 5 D) with merus without spiniform setae; carpus with two spiniform setae and two simple setae, outer margin setulose; propodus about twice longer than wide, with small distal spiniform seta and two simple setae distally.

Pereopod 4 ( Fig. 5 View FIGURE 5 E) basis without setae. Merus shorter than carpus, without spiniform setae. Carpus broad, with four spiniform setae. Propodus about two times longer than wide, with a simple seta and two smooth spiniform setae. Dactylus and unguis together almost as long as propodus.

Pereopod 5 ( Fig. 5 View FIGURE 5 F) similar to pereopod 4, but basis with three setae. Merus with a small spiniform seta. Carpus with three spiniform setae. Propodus almost three times longer than wide, with two distal simple setae and two plumose spiniform setae.

Pereopod 6 ( Fig. 5 View FIGURE 5 G) basis without setae. Merus with two spiniform setae. Propodus two times longer than wide, with five plumose setae and a simple seta.

First pleopod ( Fig. 5 View FIGURE 5 H) with a plumose seta on basal article; exopod with 23 plumose setae on outer margin; endopod with 16 plumose setae on outer margin.

Uropod ( Fig. 5 View FIGURE 5 I) basal article without setae. Exopod uniarticulate, shorter than article 1 of endopod; with three long setae, one extending until the article 4 of endopod. Endopod with five articles; article 4 shortest.

Variation. Small males with five articles in flagellum of antennule and weak spiniform seta on second article of endopod. Small females with four articles in the uropod endopod.

Etymology. The name honours the country of Mexico.

Discussion. Leptochelia mexicana n. sp. belongs to the ‘ Leptochelia dubia’ group which, according to Bamber (2010), is separated from the ‘ Leptochelia minuta ’ group by the relatively robust and short male chelipeds. Given the restricted distributions of tanaidaceans, we here compare the new species only with species from the Americas. The male of L. mexicana differs from all male species known for Leptochelia by the presence of a spiniform seta on the second article of the uropod endopod, a consistent character even in small males. In addition, only two species with males of the “ L. dubia ” group are known from America, L. algicola from Massachusetts and L. tenuicula from Cuba. By comparison with L. algicola , L. mexicana has two distal processes on the fixed fingers of chelipeds, whereas in L. algicola the processes are proximal; when compared to L. tenuicula , the main difference is that L. mexicana has an uniarticulate uropodal exopod, whereas in L. tenuicula it is biarticulate.

On the other hand, there are two records of L. dubia in America with descriptions of male specimens: Dojiri & Sieg (1997) from California, and Suárez-Morales et al. (2004) from the Mexican Caribbean. However, due to the uncertain status of the male in this species (see remarks of L. dubia ), after the re-description of male of L. dubia , a redefinition of these records will be necessary. Nevertheless, L. mexicana differs from “ L. dubia ” from California and “ L. dubia ” from Mexican Caribbean, because L. mexicana has the fixed finger linear, while in both other forms of “ L. dubia ” it is strongly curved; also, L. mexicana has two blunt processes widely spaced on the cutting edge of the fixed finger, while in both forms of “ L. dubia ” the cutting edge has two pointed processes, closely spaced.

With respect to the females of the “ L. dubia ” group, two species are known from America: L. dubia s.s. from Brazil, and L. mortenseni ( Lang, 1973) from Tobago. Leptochelia mexicana differs from these species by having the uropodal endopod with the fourth article shortest, whereas in L. dubia the third article is shortest. Also, L. mexicana has five articles in the uropodal endopod, while L. mortenseni has a maximum of four articles.

Remarks. This is the first leptocheliid species described from the Eastern Pacific.

Geographic distribution. Only known from the type locality.

Habitat. In algae and coral, littoral.