Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan

Abstract

We found 39 cheilostome species among more than 7000 specimens collected at 10 intertidal sites in rocky habitats along the shore of Akkeshi Bay, eastern Hokkaido Island, Japan. These species are herein described in detail and illustrated by scanning electron microscopy. Nine species (23% of total) are described as new (Electra asiatica, Callopora sarae, Conopeum nakanosum, Cauloramphus cryptoarmatus, Cauloramphus multispinosus, Cauloramphus niger, Stomachetosella decorata, Microporella luellae, and Celleporina minima), and 21 species (54%) are reported for the first time from Japan. Species richness ranged from eight to 29 species per study site. A TWINSPAN analysis showed the species fell into nine groups defined by the local pattern of distribution. A cluster analysis of study sites based on similarity of species composition showed three faunistic groups distributed geographically: in Akkeshi Lake, along the eastern-central shore of the bay, and at the mouth of the bay. Species richness in estuarine Akkeshi Lake was low, with a species composition very different from the outer bay. Most cheilostomes were found on rock and shell substrata, but uncommonly occurred on concrete walls, algae, hydroids, tubes of polychaetes, other bryozoans, and anthropogenic debris. Of the 39 species found, 33 (85%) contained embryos during the collecting periods, 2-7 June and 3-6 July 2004. The biogeographical composition of intertidal cheilostomes at Akkeshi Bay included species with Arctic-Boreal (28%), Boreal (59%), and Boreal-Subtropical (13%) distributions. The overall species richness of intertidal cheilostomes was two-thirds that documented intertidally in a comparable study at Kodiak, Alaska, a locality 15u higher in latitude. We attribute the lower richness at Akkeshi to differences in the nearshore marine environment between the two localities.

The Internal-Brooding Apparatus in the Bryozoan Genus Cauloramphus (Cheilostomata: Calloporidae) and Its Inferred Homology to Ovicells

“…Although in the course of this study we directly observed embryos in only two of the species examined (C. spinifer and C. cryptoarmatus), internally brooded embryos have been reported for all the species examined (Dick and Ross, 1988;Dick et al, 2005;Grischenko et al, 2007). These data coupled with our observation of ooecia in the eight species studied strongly suggest that a reduced, maternally produced kenozooidal ooecium and internal brood sac are characters common to all species of Cauloramphus and should thus be appended as diagnostic characters for this genus.…”

“…Cauloramphus spinifer (Johnston, 1832); Cauloramphus magnus Dick and Ross, 1988; Cauloramphus cryptoarmatus Grischenko, Dick, and Mawatari, 2007; Cauloramphus niger Grischenko, Dick, and Mawatari, 2007; Cauloramphus multispinosus Grischenko, Dick, and Mawatari, 2007. Narrow Strait, Kodiak, Alaska, USA, September-December 1982:…”

“…1B, C, 2005 clearly show a fairly substantial ooecium. Dick et al (2005) and Grischenko et al (2007) reported, but did not describe in detail, both ooecia and internal brooding in all seven species of Cauloramphus they treated between them, including five new species. This result suggests that an ooecium, reduced to a variable extent, and internal brooding are features common to all species of Cauloramphus.…”

First occurrence of the non-native bryozoan Schizoporella japonica Ortmann (1890) in Western Europe

“…Recent papers with more detailed descriptions (e.g. Dick et al 2005;Grischenko et al 2007) generally include means and standard deviations (but need also to include sample size), in addition to range, so that the data sets can be incorporated into any subsequent analysis (as in this paper). To conform with usual practice, we include ranges in Tables 1, 3 and 4.…”

“…The bryozoan was identified as Schizoporella japonica Ortmann (1890) on the basis of the most recent comprehensive redescription of material from Alaska and Japan (Dick et al 2005;Grischenko et al 2007). The original description by Ortmann (1890), as S. unicornis var.…”