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Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Order Amphipoda
Family Pseudoniphargidae

Pseudoniphargus carpalis Stock, Holsinger, Sket & Iliffe, 1986



Taxonomic Characterization: The posterior margin of the epimeral plates of P. carpalis lacks setules. The 3rd peduncle segment of the 1st antenna is elongate and the 1st segment of the accessory flagellum is very slender. The spines of the outer lobe of the 1st maxilla have 8 or 9 denticles on the medial margin and 0-4 denticles on the lateral margin. The carpus of P1 and P2 is elongate-rectangular and there are 6 groups of setae on the posterior carpal margin. The ventral margin of the coxal plates of the 3rd and 4th pereiopods have 11 or 12 setules with a short posterior emargination of coxal plate 4. The postero-ventral lobe on the basis of pereiopods 5-7 is large. There are no differences between the sexes except for the absence of oostegites and the presence of genital papillae in the male (Stock et al., 1986).

Disposition of Specimens: Specimens were deposited in the Zo÷logisch Museum Amsterdam, including a female holotype and a male allotype.

Ecological Classification: Stygobitic

Size: Total body length of male with genital papillae 4 mm; total body length of female with spiniferous oostegites 4 mm.

Number of Species in Genus: At least 58; occurring in inland groundwater around the Mediterranean basin, in Atlantic drainage systems of Portugal and Spain, on Madeira, Faial (Azores), Canary and Balearic Islands, Morocco and France and in Bermudian groundwater (Subterranean Genera of Pseudoniphargidae).

Species Range: P. carpalis was collected from wells in Devonshire, Paget and Warwick Parishes, Bermuda (Stock et al., 1986).

Closest Related Species: P. carpalis is closest to P. grandimanus, the only other species of the genus from Bermuda. The two differ from their congeners by the presence of a hyaline lobe on the posterior margin of the merus of gnathopod 1, the slender rami of uropods 1 and 2, the larger number of spines on the ventral margin of the epimeral plates among adults and by the unarmed tip of the telson lobes (Stock et al., 1986).

Habitat: Fresh groundwater lenses

Ecology: P. carpalis occurs in wells of Bermuda throughout the entire salinity range, but prefers oligohaline waters. It is usually found together with P. grandimanus. The adults of the species were found at greater distances from the sea coast than the juveniles (147-853 m) vs. (11-180 m) respectively, which could indicate a dependence on anchialine/ marine habitats for reproduction. It also indicates that the juveniles migrate inland to mature. The chlorinities at which large-sized (>3 mm) and small-sized (<3 mm) specimens were found did not differ significantly. The majority of the specimens were collected at Lufkin Tunnel, Watlington Waterworks, Devonshire Parish (Stock et al., 1986).

Life History: 18 specimens were collected, among which were adult males and females, subadult males and females and juveniles, the majority of which were juveniles. No ovigerous females were found among the samples (Stock et al., 1986).

Evolutionary Origins: The insular areas now inhabited by Pseudoniphargus were more than likely populated from marine ancestors stranded during the lowering of sea level during the Tertiary. The occurrence of this genus on Bermuda represents amphiatlantic distribution of stygofaunal elements (Stock et al., 1986).

Conservation Status: The species is restricted to a range the freshwater lens of central Bermuda.

Reference:

  • Stock, J.H., J.R. Holsinger, B. Sket and T.M. Iliffe. 1986. Two new species of Pseudoniphargus (Amphipoda), in Bermudian groundwaters. Zoologica Scripta, 15(3): 237-249, 8 figures, 2 tables.

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