Platorchestia bousfieldi, Hou & Li, 2003

Hou, Z. - E. & Li, S., 2003, Terrestrial talitrid amphipods (Crustacea: Amphipoda) from China and Vietnam: studies on the collection of IZCAS, Journal of Natural History 37, pp. 2441-2460 : 2448-2453

Platorchestia bousfieldi n. sp.

(figures 5–8)

Material examined. One female (holotype), one female and one juvenile (paratypes). Collection label not seen. Blind terrestrial talitrids are rare, especially in China, where this phenomenon has been found for the first time. Description of this taxon may be important for the phylogeny of landhoppers .

Etymology. The species name is in honour of Dr E. L. Bousfield, who kindly gave us much help when we were in a difficult period during the present research.

Description. Female (  , IZCAS-I-A0015), body length 7.5 mm. Head subrectangular, inferior antennal sinus distinct. Eyes lacking. Antenna 1: peduncle segments subequal, with distal spines, flagellum four-articulate with some spines. Antenna 2: peduncular article 4 about 71% of length of article 5, thicker than article 5, both with marginal spines; flagellum 1.67 times as long as peduncular article 5, nine-articulate, armed with fine marginal spines.

Upper lip convex, with minute setae apically. Left mandible: incisor five-dentate, lacinia mobilis with five weak teeth. Right mandible: incisor five-dentate, lacinia mobilis bifurcate, ridge of each cusp minutely serrate. Lower lip: inner shoulder and margin of central trough pilose. Maxilla 1: inner plate with two apical spinulate setae, outer plate with nine saw-like spines on distal margin, palp minute. Maxilla 2: inner plate with one large seta on outer distal angle, outer plate with several long setae near outer distal angle. Maxilliped: inner plate with three distal spines, article 4 of palp distinct.

Gnathopod 1: coxal plate smoothly rounded anterodistally, low margin with three spines and some setae; basis with two spines on posterior margin; ischium with a marginal and two distal spines; merus without tumescent hump, posterior margin spinose; carpus and propodus lacking tumescent hump, propodus about 0.67 times as long as carpus, palm truncate, with a spine and two setae at posterior angle; dactylus longer than palm of propodus, with one stiff setae on concave margin. Gnathopod 2: coxal plate with cuspidate posterior margin; basis expanded anteriorly, anterior margin with seven small spines evenly; merus with spines on posterior margin and lateral surface; carpus and propodus tumescent posteriorly, propodus shorter than carpus, with spines-row on lateral surface; dactylus hooked distally, grasping margin with a row of four setae.

Pereopods 3 and 4: coxal plates wider than deep, ventral margin straight, with short setae, posterior margin cuspidate; bases almost parallel-sided; carpus short, posterior margins of merus to propodus with denser spines than anterior margins; dactylus with a spine at hinge of nail. Pereopod 3 longer than pereopod 4, carpus of pereopod 4 shorter than that of pereopod 3.

Pereopod 5: anterior lobe of coxal plate larger than posterior one, posterior margin with four fine setae; posterior margin of basis expanded roundly, armed with several short setae, anterior margin with spines; dactylus cuspidactylate, with a spine near hinge of nail. Pereopod 6 much longer than pereopod 5, coxal plate posterolobate; basis ovate, posterior margin with some spinules; merus to propodus with groups of spines along anterior and posterior margins. Pereopod 7: coxal plate shallow, non-lobate, ventral margin weakly convex; basis expanded posteriorly.

Coxal gills of pereopods 2–6 present.

Oostegites of pereopods 2–4 parallel-sided and elongate, oostegite 5 shortest and widened in the middle. All without marginal setae.

Epimeral plates 1–3 with slightly pointed posterior angles, ventral margin unarmed, posterior margin with one to three setae. Pleopods 1–3 similar, peduncles with two retinaculae, peduncles of pleopods 1 and 2 marginally bare, peduncle of pleopod 3 with a few setae on outer margin; both rami with about 10 particles, fringed with long plumose setae.

Uropod 1: peduncle longer than rami, with five spines on outer margin, three spines on inner margin; outer ramus a little shorter than inner ramus, marginally bare; inner ramus with three spines on outer margin; both rami with distal spines. Uropod 2: peduncle with three spines on both margins, outer ramus with one midmarginal and two distal spines, inner ramus with three outer marginal and three distal spines. Uropod 3: peduncle longer than deep, with three distal spines; ramus about 0.6 times as long as peduncle, with one subdistal and two distal spines.

Telson apically notched, longer than wide, bearing one or two spines on dorsal surface and three distal spines.

Male unknown.

Remarks. The new species is similar to Platorchestia japonica in the parallelsided propodus of gnathopod 1, the tumescent carpus and propodus of gnathopod 2, and pereopod 5 smaller than pereopods 6 and 7. It differs from Platorchestia japonica in the absence of eyes, the telson notched apically bearing two facial and three to four distal spines, and the oostegites bearing few marginal setae.

Although there is no information on the habitats of the present blind species, it is very unusual. We are sure it is definitely terrestrial because it has narrow oostegites. The long and biramous pleopods of the present species are more like those of some of the Tasmanian cuspidactylate species, which are less terrestrially adapted than simplidactylate species (Friend, 1987).