Diversity and distribution of adeonid bryozoans (Cheilostomata: Adeonidae) in Japanese waters

Masato Hirose

doi:10.5852/ejt.2016.203

Abstract

Adeonid bryozoans construct antler-like erect colonies and are common in bryozoan assemblages along the Japanese Pacific coast. The taxonomy of Japanese adeonid species, however, has not been studied since their original descriptions more than 100 years ago. In the present study, adeonid specimens from historical collections and material recently collected along the Japanese coast are examined. Eight adeonid species in two genera were detected, of which Adeonella jahanai sp. nov., Adeonellopsis parvirostrum sp. nov., and Adeonellopsis toyoshioae sp. nov. are described as new species based on the branch width, size and morphology of frontal or suboral avicularia, shape and size of areolar pores, and size of the spiramen. Adeonellopsis arculifera (Canu & Bassler, 1929) is a new record for Japan. Lectotypes for Adeonellopsis japonica (Ortmann, 1890) and Adeonella sparassis (Ortmann, 1890) were selected among Ortmann’s syntypes. Most species of Adeonellopsis around Japan have a southern distribution from Sagami Bay to Okinawa, while A. japonica shows a more northern distribution from Kouchi to Otsuchi. In contrast, Adeonellopsis arculifera was collected only from southwestern Japan. A key to Japanese adeonid species is provided.

Highlights

Order Cheilostomata in Class Gymnolaemata is the most speciose group of bryozoans in modern marine environments (Bock & Gordon 2013)
Adeonella and Adeonellopsis differ in the type of frontal shield: Adeonella has a lepralioid shield in which a spiramen leads into the space above the sinus, and a distinct primary orifice, while Adeonellopsis is thought to have an umbonuloid frontal shield and the spiramen leads into the space above the frontal membrane (Cook 1973; Lidgard 1996; Berning et al 2014)
Adeonella and Adeonellopsis are different in the arrangement of the spiramen and frontal/suboral avicularia; Adeonella generally has a monoporous spiramen and frontal avicularia in various positions, whereas Adeonellopsis has a monoporous or multiporous spiramen, with a suboral avicularium situated distal to the spiramen, directed distally or distolaterally

Summary

Introduction

Order Cheilostomata in Class Gymnolaemata is the most speciose group of bryozoans in modern marine environments (Bock & Gordon 2013). One of the largest genera in the family, Adeonellopsis, comprises about 50 species that are almost globally distributed but are absent from higher latitudes (or alternatively: boreal and arctic waters) Another large genus, Adeonella, comprises about 50 species, distributed in the Indo-West Pacific, Mediterranean, and Atlantic. The Adeonidae have received a relatively great amount of attention over the past decades, a number of new species were introduced, and several known species revised (e.g., Cook 1982; Arístegui 1985; Hayward 1988; Amui 2005; Rosso & Novosel 2010; Almeida et al 2015). Owing to their complexity at zooidal and zoarial level, the ontogeny and astogeny of the Adeonidae is fairly well known (e.g., Cook 1973; Cheetham & Hayek 1983; Wass 1991; Lidgard & Buckley 1994; Lidgard 1996; Bock & Cook 2000, 2004; Smith et al 2001)

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Conclusion