Podocerus cuspiclunis, Horton, 2008

Horton, Tammy, 2008, Amphipoda from marine caves of Hong Kong Island, Journal of Natural History 42 (9 - 12), pp. 825-854 : 847-849

Podocerus cuspiclunis sp. nov.

( Figure 11 )

Type material

Holotype male, 4.5 mm, Epifauna station 2 (25/10/02), NHM Reg. Nos. 2005.2749–2750.

Material examined

Paratypes. Epifauna station 1 (21/10/02), one female specimen, one juvenile, NHM Reg. Nos. 2005.2760–2761; Epifauna station 2 (25/10/02), four females, three males and two juvenile specimens, NHM Reg. Nos. 2005.2751–2759; Epifauna station 3 (25/10/ 02), one female specimen, NHM Reg. No. 2005.2762; Epifauna station 6 (21/10/02), three females, three juvenile specimens, NHM Reg. Nos. 2005.2763–2768; Epifauna station 8 (21/10/02), one male specimen, NHM Reg. No. 2005.2769; Epifauna station 10 (21/10/02), two juvenile specimens, NHM Reg. Nos. 2005.2770–2771; all from Conic Island Cave, Hong Kong .

Description

Male, holotype 4.5 mm. Lateral cephalic lobes truncated; lateral ocular bulges strongly developed. Pereon segments 3, 4, 5, and 6 with acute dorsal carinations increasing in size posteriorly; rounded dorsal carinations on pereon segment 7 and pleon segments 1 and 2. Antenna 1 slender, peduncular article ratios 1:1.6:1.3; accessory flagellum small, 1-articulate; primary flagellum longer than peduncle article 3, with five articles. Antenna 2 elongate; peduncle article 5 twice the length of article 4, flagellum less than half the length of article 5 with three articles. Mouthparts typical of the genus. Gnathopod 1; coxa extended forward, rounded anterodistally; propodus slender, setose, palm obtuse almost simple; dactyl long, reaching palm edge. Male gnathopod 2; coxa produced anterodistally to a small projection with a robust seta; basis distally expanded with a posterodistal robust seta; merus with acute distal tooth; propodus enlarged, subovoid, palm and posterior margin confluent, strongly setose (setae omitted from figure for clarity), with proximal projection, mediodistal subrectangular projection and a distal process; dactyl simple, extending to proximal palmar process. Pereopods 3–7 ordinary. Uropod 1 elongate, peduncle with five robust setae; outer ramus shorter than inner, with four robust dorsal setae, one long robust seta and one short robust seta terminally; inner ramus with nine robust dorsal setae, one long robust seta and one short robust setae terminally. Uropod 2; peduncle short; inner ramus longer and stouter than outer ramus, with five dorsomedial robust setae, two dorsolateral robust setae, two apical robust setae and one long terminal seta; outer ramus half the length of inner ramus with two dorsomedial robust setae and two terminal robust setae. Uropod 3 very small, lacking rami and setae. Telson subtriangular with two lateral robust setae and two long terminal robust setae.

Female, as male except gnathopod 2; coxa distally expanded and rounded; basis distally expanded with two posterodistal robust setae; merus without acute distal tooth as in male but with numerous distal setae; propodus subovoid, palm distinct straight and setose with three robust setae proximally; dactyl simple, extending to proximal palm edge.

Remarks

This species was collected at a number of sites, but was most numerous from the epifaunal samples 2, 10 and 6 on 25/10/02. The genus Podocerus is difficult taxonomically both because of the fragility of the specimens and tendency to lose appendages, and the variability in carination with growth ( Moore 1990). This species most closely resembles Californian specimens of Podocerus cristatus ( Thomson 1913) as figured by Barnard (1962). Despite wide intraspecific variability in the genus Podocerus , the differences warrant a new species status for the Hong Kong material. Podocerus cuspiclunis differs in having pereonal segments 3–7 with dorsal carination compared to segments 5–7 for P. cristatus , and in gnathopod 2 propodus being more robust with three distinct palmar processes compared to the two distal processes of P. cristatus .

Etymology

From the Latin: cuspis , (f) meaning pointed, and clunis, (f) meaning rump or buttocks, thus alluding to the carinated ‘‘rump’’ area of the amphipod.

Figures

Figure 11. Podocerus cuspiclunis sp. nov.