Porrorhynchus (Rhomborhynchus) depressus misoolensis ( Ochs) 1955

Polhemus, Dan A., 2011, New distributional records for Gyrinidae (Insecta: Coleoptera) on New Guinea and nearby islands, with a checklist of the New Guinea species, Zootaxa 2900, pp. 51-68 : 53

Porrorhynchus (Rhomborhynchus) depressus misoolensis ( Ochs) 1955 new combination

Fig. 1

Dineutus (Rhomborhynchus) depressus misoolensis Ochs, 1955: 135 .

Material examined. INDONESIA, Papua Prov. [= former Irian Jaya Prov.]: 6 males, 15 females, Misool Is., central interior, Tama River, upper trib. to Kasim River, SE of former Fakal village site, 60 m. [200 ft.], 1°51'38.1"S, 129°55'24.1"E, water temp. 26.5° C., 22 April 1999, 10:30–14:30 hrs., CL 7110, D. A. Polhemus ( USNM).

Discussion. This subspecies is apparently endemic to the island of Misool ( Fig. 1 ), and was previously recorded in the literature only from the type series ( Ochs, 1955). The new record provided below also comes from this island, and based on known collections, this subspecies is confined to the Misool area of freshwater endemism (Area 3) as defined by Polhemus & Allen (2007).

This taxon was taken on Misool at the Tama River, a broad, clear, upland river flowing at moderate speed through alternating riffles and pools in a bed of metamorphic and sedimentary cobbles and gravels, with the channel margins partly shaded by intact upland rain forest. Although many other streams on Misool were sampled during a survey in 1999, individuals of P. depressus misoolensis were found only at this locality, which was also the only collecting site to lie along a stream reach flowing through non-carbonate rocks. Misool is largely an upraised limestone platform, but has a central ridge of metamorphics and sandstones, and it is possible that underlying petrology may influence stream water chemistry and substrate characteristics, and thus the distribution of this gyrinid taxon on Misool.

Figures

FIGURE 1. Distribution of certain Porrorhynchus (Rhomborhynchus) depressus subspecies on New Guinea and adjacent islands. Symbols with grey centers represent previous records; symbols with black centers represent new records presented in this paper.