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Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Order Amphipoda
Family Pseudoniphargidae

Pseudoniphargus grandimanus Stock, Holsinger, Sket & Iliffe, 1986


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Pseudoniphargus grandimanus

Taxonomic Characterization: Pseudoniphargus grandimanus is colorless and eyeless. The cephalosome lacks a rostrum and the body somites lack teeth. The upper lip is broadly rounded and the lower lip has large inner lobes. The mandible palp is 3-segmented and the 1st maxilla is contralaterally symmetrical with a 2-segmented palp. The 2nd maxilla has a slightly bilobed outer lobe and the maxilliped has a 4-segmented palp. The 1st gnathopod is sexually dimorphous in large specimens with the propodus of males being larger than that of females. The 2nd gnathopod is also sexually dimorphous in the propodus among specimens of at least 6 mm. The pleopods are biramous. The telson has a broad, rounded, medial cleft. The male genital papillae are small, rounded and on pereionite 7 (Stock et al., 1986).

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Pseudoniphargus grandimanus: head

Disposition of Specimens: Specimens were deposited in the Zo÷logisch Museum Amsterdam, the United States National Museum of Natural History and in the collection of B. Sket, Ljubljana.

Ecological Classification: Stygobitic

Size: Total body length of adult male ranges from 6.5-8 mm, total body length of adult female with setose oostegites 7 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 the Madeira, Faial (Azores), Canary and Balearic Islands, Morocco and France and in Bermudian groundwater (Subterranean Genera of Pseudoniphargidae).

Species Range: P. grandimanus inhabits wells, waterworks and cave waters in Hamilton, St. George's, Devonshire, Paget, Smith's and Warwick Parishes, Bermuda including Church, Wonderland, Admiral's and Government Quarry Caves (Stock et. al., 1986).

Closest Related Species: P. grandimanus is closest to P. carpalis, 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: Anchialine limestone caves and freshwater lenses

Ecology: P. grandimanus occurs in wells, waterworks and cave waters of Bermuda throughout the entire salinity range, but prefers oligohaline waters. It is usually found together with P. carpalis. 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 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: 195 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. Two specimens were collected that are believed to be intersexes due to their propodus of gnathopod 2 which is intermediate in size (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. P. grandimanus was originally described as P. adriaticus which was at the time the only salt water taxon and the collection consisted mostly of small juveniles (Stock et al., 1986).

Conservation Status: P. grandimanus is considered to be critically endangered (IUCN, 2000). The species is found in a wide range of Bermudian cave and groundwater habitats.

References:

  • IUCN, 2000. The 2000 IUCN Red List of Threatened Species. Gland, IUCN, 61 pages.
  • 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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