Ostracods (Crustacea) from Sarobetsu Marsh, Northern Hokkaido, Japan : Taxonomy and Phenology with Description of Pseudocandona tenuirostris sp. nov.

Abstract

We sampled ostracods in Sarobetsu Marsh, Rishiri Rebun Sarobetsu National Park, Hokkaido, Japan, from April 2005 to November 2007 and identified four species: Cryptocandona sp., Pseudocandona tenuirostris sp. nov., Physocypria nipponica Okubo, 1990, and Metacypris digitiformis Smith and Hiruta, 2004. Cryptocandona sp. is similar to C. reducta (Alm, 1914) and C. brehmi (Klie, 1934), but positive identification is postponed due to the absence of male specimens. In having three setae in the setal group of the second segment of the mandibular palp, Pseudocandona tenuirostris sp. nov. belongs to the Ps. rostrata species group, and it is characterized by a beak-like medial lobe on the distal end of each hemipenis. From literature based information, Japanese populations of Physocypria nipponica and Ph. kraepelini from Europe have morphological differences at their hemipenis. We regard Ph. nipponica as a distinct species, even though this taxon has been suggested to be a synonym of Ph. kraepelini Muller, 1993. We discuss the seasonal prevalence of the four species detected.