Chelorchestia limicola ( Haswell, 1880 )

Serejo, Cristiana S., 2009, Talitridae *, Zootaxa 2260 (1), pp. 892-903 : 893-896

Chelorchestia limicola ( Haswell, 1880) (comb. nov.)

( Figs 1 , 2 , Pl. 6E, F)

Talorchestia limicola Haswell, 1880: 98 , pl. V, fig. 2. — Stebbing, 1906a: 547. — Stebbing, 1910: 645. — Sheard, 1937: 26. — Springthorpe & Lowry, 1994: 128. — Lowry & Stoddart, 2003: 275.

Type material. Neotype, male, 10.7 mm, AM P80168, Mermaid Cove , Lizard Island, Queensland, Australia (14°38.91’S 145°27.26’E), mangrove roots from mangroves behind beach, intertidal, C. Serejo, 3 March 2005 ( QLD 1785 ).

Additional material examined. 6 males and 33 females, AM P71337 ( QLD 1784 ) ; 2 males and 2 females, MNRJ ( QLD 1784 ) ; 1 female, 9.8 mm, AM P80169 ( QLD 1785 ) ; 1 male and 1 female, AM P71317 ( QLD 1785 ) ; 3 males and 22 females, AM P71338 ( QLD 1785 ) .

Type locality. Mermaid Cove , Lizard Island, Queensland, Australia (14°38'50"S 145°27'14"E), on mangrove roots behind beach .

Description. Based on neotype male, 10.7 mm, AM P80168.

Head. Head eye small, round, less than 1/5 head length. Antenna 1 shorter than peduncle article 4 of antenna 2. Antenna 2 longer than pereonite 3 and up to half body length; peduncular articles narrow, with sparse, small robust setae, article 5 longer than article 4. Mandible left lacinia mobilis 4–dentate. Maxilliped palp article 4 reduced.

Pereon. Coxae 2–4 wider than deep. Gnathopod 1 sexually dimorphic, subchelate; posterior margin of merus, carpus and propodus with rugose lobe; propodus subrectangular; palm concave; dactylus subequal in length to palm, simplidactylate. Gnathopod 2 sexually dimorphic, chelate; basis anteriorly smooth; posterior margin of merus and propodus with rugose lobe; carpus indistinct; propodus with two small humps on anterior margin, palm with large midpalmar sinus followed by a large thumb-like bifid process; dactylus fitting palm with well developed process that fits the palmar sinus. Pereopods 3–7 simplidactylate. Pereopod 4 slightly shorter than pereopod 3. Pereopods 3–4 with similar dactyli. Pereopods 6–7 not sexually dimorphic.

Pleon. Pleopods 1–3 well developed, peduncles not expanded. Epimeron 3 posterior margin smooth, without setae, posteroventral corner subquadrate, ventral margin without robust setae. Uropod 1 peduncle with 5 and 3 robust setae in two rows, distolateral robust seta present, less than 1/4 length of outer ramus; inner ramus subequal in length to outer ramus and with marginal robust setae; outer ramus without robust setae. Uropod 2 peduncle with 3 and 2 robust setae in two rows, inner ramus subequal in length to outer ramus; inner ramus and outer ramus with 2 marginal robust setae each. Telson longer than broad; apical margin incised and with a pair of robust setae, each lobe with 2 – 3 robust setae.

Female (sexually dimorphic characters). Based on female, 9.8 mm, AM P80169. Gnathopod 1 posterior margin of merus, carpus and propodus without rugose lobe; palm oblique; dactylus sightly longer than palm. Gnathopod 2 mitten-shaped; basis narrow; posterior margin of merus, carpus and propodus with rugose lobe; carpus posterior margin distally concave; palm smooth; dactylus shorter than palm. Oostegites 2–4 oval with 18, 20 and 15 setae. Oostegite 5 margins convex with 9 setae.

Habitat. The material was found on mangrove roots behind beach, or under the leaf litter from around crab holes at back of beach.

Remarks. Chelorchestia limicola was described by Haswell (1880) within Talorchestia , but has never been redescribed. Despite the brief description of Haswell (1880), it was possible to identify this species based on the diagnostic male gnathopod 2. The type material is apparently lost ( Lowry & Stoddart 2003) and the designation of a neotype, based on material from Lizard Island, is herein proposed as the type locality was originally from Queensland. Chelorchestia currently includes five species: C. costaricana from mangrove swamps in Costa Rica ( Stebbing 1906b); C. darwini from mangrove and estuarine areas of the Brazilian coast ( Serejo 2004b); C. forceps from south-eastern coast of United States; C. colombiensis from Palma Island, off the Pacific coast of Colombia found on the littoral fringe zone associated to encrusting and filamentous algae ( Valencia & Giraldo, 2009), and C. vaggala from San Cristóbal Island (Galapagos Islands) found on litter of altitudes varying from 450 to 600 m ( Bowman, 1977).

Chelorchestia limicola is easily identified as a Chelorchestia as the male gnathopod 2 is chelate, the outer ramus of uropod 1 lacks setae and the species typically lives in mangroves as most species do. However, the general structure of male gnathopod 2 of C. limicola is different when compared with other species of the genus. Chelorchestia vaggala is the most different. In the original description a small male (9.4 mm) was described as having a subchelate male second gnathopod with transverse palm ( Bowman 1977). However, ontogenetic variation in this appendage suggests that this gnathopod form could be a juvenile stage of a terminal chelate gnathopod (see Smith & Heard 2001), although not yet documented for this species. Considering that the chelate gnathopod is a diagnostic feature for Chelorchestia it would important to collect more mature males of C. vaggala to confirm its generic status.

Comparing C. limicola with the recently described C. colombiensis , both have gnathopod 2 propodus not elongated and the thumb-like process is bifid. However, the basis of male gnathopod 2 of C. limicola does not have tubercules on the anterior margin; the ischium is not lobate and the proximal hump on palm is also absent. Moreover, the dactylus of C. limicola has a better developed process. Compared with the other three Chelorchestia species ( C. costaricana , C. darwinii and C. forceps ), C. limicola has the male gnathopod 2 propodus about 1.4 x as long as broad (vs around 2 x as long as broad); and the propodus thumb-like process is thick and bifid, not much extended anteriorly (vs. slender, not bifid and very extended anteriorly, especially in terminal males).

Distribution. Australia. Queensland: near Bowen ( Haswell 1880); Mermaid Cove, Lizard Island (current study).

Figures

FIGURE 1. Chelorchestia limicola (Haswell, 1880), neotype, male, 10.7 mm, AM P80168, Lizard Island, Great Barrier Reef.

FIGURE 2. Chelorchestia limicola (Haswell, 1880), neotype, male, 10.7 mm, AM P80168 (telson); female, 9.8 mm, AM P80169; Lizard Island, Great Barrier Reef.