Pseudoniphargus carpalis Stock, Holsinger, Sket & Iliffe,
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.
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
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
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.
- 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.