Pseudidothea richardsoni Hurley, 1957

Poore And T, Gary C. B., 2004, Pseudidotheidae (Crustacea: Isopoda: Valvifera) reviewed with description of a new species, first from Australia, Memoirs of Museum Victoria 61 (1), pp. 75-83 : 81-82

Pseudidothea richardsoni Hurley

Figure 4

Pseudidothea richardsoni Hurley, 1957: 15–17 , figs 74–91.

Material examined. New Zealand, Banks Peninsula region . Off Lyttelton, 4 fm [7.3 m], H. Suter, CMNZ (4 females, 5.1–6.1 mm; 4 males, 4.8–5.1 mm, 1 figured); NMV J47116 (1 female, 1 male). Big Bay, mud bottom, 12 m, MNZ CR-9846 (2). Beacon Rock, mud bottom, 10–12 m, MNZ CR-9850 (1). E side of Port Levy, mud bottom, MNZ CR-9855 (1) .

Diagnosis. Head with anterior margin vaguely tuberculate, dorsally with tubercles, pereon finely setose and vaguely tuberculate; tergites slightly laterally produced. Pleotelson with blunt anterolateral processes, laterally tuberculate, dorsally smooth, tapering to a blunt apex. Male antenna 1 flagellum with about 7 clusters of aesthetascs. Antennae and pereopods without tubercles. Pereopods finely setose. Antenna 2 peduncle with long, fine setae on articles 3–5. Male pleopod 1 endopod about as long as peduncle, with plumose setae apically; exopod longer than endopod, with 15 spinules on lateral margin, tapering distally, thickened and folded laterally to partially cover groove that runs to apex. Male pleopod 2 appendix masculina styliform, about as long as endopod. Uropodal exopod with strong apical setae, endopod with 3 pappose setae; exopod about two-thirds as long as endopod. Oostegite absent from pereopod 5.

Descriptive notes. We examined a male specimen of P. richardsoni and here figure and describe pleopods 1 and 2 and the penial process:

Male pleopod 1 peduncle twice as long as wide, with 8 coupling hooks mesially; endopod lamellar with 5 lateral spinules proximally, tapering distally with 5 apical plumose setae; exopod longer than endopod with 15 spinules on lateral margin, tapering distally, thickened and folded laterally to partially cover a groove that runs to the obtuse apex. Male pleopod 2 endopod with 13 apical plumose setae; exopod with 39 marginal plumose setae; appendix masculina styliform, about as long as endopod. Penial process fused, distally bilobate.

Distribution. Cook Strait and Lyttelton Harbour, New Zealand, 7–146 m depth.

Remarks. Hurley (1957) observed that P. richardsoni is close to “ P. bonnieri Ohlin ” (= P. miersii ) but he considered there are sufficient differences to warrant a separate species; these include uropodal endopod with three pappose setae, lack of tubercles on the pereopods and antenna 2 peduncle with long fine setae on articles 3–5.

The first male pleopods are also different from those of P. miersii . Pseudidothea miersii has a male pleopod 1 peduncle with 6–7 coupling hooks, endopod with plumose setae marginally, exopod with 16 or 17 spinules laterally and with an acute apex bent outwards, almost at right angles. In contrast, P. richardsoni has a peduncle with eight coupling hooks, an endopod with five lateral spinules proximally and five apical plumose setae, and an exopod with 15 spinules on its lateral margin, tapering distally to an obtuse apex.