Masato Hirose

Description and molecular phylogeny of a new species of Phoronis (Phoronida) from Japan, with a redescription of topotypes of P. ijimai Oka, 1897

Abstract We describe Phoronis emigi sp. n. as the eighth member of the genus based on specimens collected from a sandy bottom at 33.2 m depth in Tomioka Bay, Amakusa, Japan. The new species is morphologically similar to P. psammophila Cori, 1889, but can be distinguished from the latter by the number of longitudinal muscle bundles in the body wall (56–72 vs. 25–50 in P. psammophila) and the position of the nephridiopores (situated level with the anus vs. lower than the anus in P. psammophila). Using sequences of the nuclear 18S and 28S rRNA genes and the mitochondrial cytochrome c oxidase subunit I (COI) gene, we inferred the relationship of P. emigi to other phoronids by the maximum likelihood method and Bayesian analysis. The analyses showed that P. emigi is closely related to P. hippocrepia Wright, 1856 and P. psammophila Cori, 1889. We describe the morphology of the topotypes and additional material for P. ijimai Oka, 1897. Neither our morphological observations of P. ijimai, nor the phylogenetic analyses based on 18S and COI sequences, contradicts that P. vancouverensis Pixell, 1912 is conspecific with P. ijimai, a synonymy that has long been disputed.

Are Plumatellid Statoblasts in Freshwater Bryozoans Phylogenetically Informative

Morphological characters of statoblasts (including floatoblasts and sessoblasts) in freshwater bryozoans have been important in phylactolaemate systematics and identification in that older phylogenetic hypotheses relied heavily on statoblast morphology. To assess the reliability of statoblast characters in drawing conclusions about phylogeny, we examined the phylogenetic distribution of metric and proportional floatoblast characters, floatoblast symmetry, and floatoblast and sessoblast microsculpture in Plumatellidae, the largest family of phylactolaemates, in the context of molecular phylogenetic reconstructions based on nucleotide sequences of parts of the mitochondrial 12S rRNA, 16S rRNA, and cytochrome b (cytb) genes. Adding cytb sequences to a previous phylogeny based on 12S and 16S increased support only for a node including Plumatella vaihiriae in the P. repens clade. Characters of gross floatoblast morphology were generally not phylogenetically informative individually, but collectively discriminated among members of three relatively well-supported clades that were analyzed as pre-defined groups in a discriminant analysis. Two characters of floatoblast microsculpture (reticulation and hypertubercles) were restricted to particular clades; other characters (e.g., villi) were clearly convergent. In nine of 11 cases, fenestral microsculpture was identical or partly correlated between the floatoblast and sessoblast of a species. Overall, our results indicate that statoblast morphology is not highly phylogenetically constrained.

Freshwater Bryozoa of Tonle Sap, Cambodia

Abstract We identified a collection of freshwater bryozoans from Tonle Sap (meaning Tonle Lake), Cambodia, a body of water fed by the Mekong River and characterized by extreme fluctuations in water level between the wet and dry seasons. The collection also included specimens from the moat of Angkor Wat, located at the north end of the lake. We found four phylactolaemate species (Plumatella bombayensis, Plumatella casmiana, Plumatella vorstmani, Hyalinella lendenfeldi) and one ctenostome species (Hislopia cambodgiensis) from the lake, and only a single, additional phylactolaemate species (Plumatella javanica) from the moat. We provide brief descriptions of these species, photographs of colonies for some, and photomicrographs by light and scanning electron microscopy (SEM) of statoblasts. None of the species encountered in this study is endemic to Cambodia, and the wide distributions of the species are possibly related to the dispersability of floatoblasts by birds. We briefly discuss some of the taxonomic problems surrounding Hislopia cambodgiensis.

Molecular Distance and Morphological Divergence in Cauloramphus (Cheilostomata: Calloporidae)

Molecular phylogenetic analysis of cytochrome c oxidase I (COI) sequences in the calloporid genus Cauloramphus was used to examine (1) the correlation between COI genetic distance and morphological divergence in selected characters; (2) relative levels of intra- and inter-population COI genetic divergence; and (3) the utility of COI in discriminating species and species groups. The phylogeny includes representatives of 15 previously described morphospecies and five unidentified taxa. Kimura 2-parameter (K2P) distances within local populations of five morphospecies ranged from 0.00% to 3.01%. For three morphospecies, K2P distances ranged from 0.50% to 11.0% between populations separated geographically by 750–4,500 km, with no correlation between genetic distance and geographical separation; we identified at least one putative cryptic species. The phylogeny detected at least three undescribed morphospecies; two other specimens not identified to species prior to the analysis emerged as divergent populations of, or sister taxa to, previously described or newly detected morphospecies. Our results indicate that in Cauloramphus, and perhaps in many other cheilostomes, there is a necessary bias in application of the morphological species concept. Lack of detectable morphological differences between geographically separate populations says little about genetic distance between them, and operationally they must be considered as populations within a single morphospecies. On the other hand, geographically separate populations exhibiting overt differences in the form of, or non-overlapping differences in the ranges of, one or more characters indicate substantial genetic divergence and probable reproductive isolation, validating application of the morphological species concept as a proxy for the biological species concept in these cases.

Revision of the genus Buchneria (Bryozoa, Cheilostomata) from Japan

Abstract Buchneria dofleini (Buchner, 1924), type species of Buchneria Harmer, 1957,was first described from material collected in 1904–1905 from Sagami Bay, Japan, but the type specimens had not been reexamined since the original description. In this study, I examined specimens of Buchneria from historical collections and material recently collected near Akkeshi, Hokkaido, Japan. Three Buchneria species were detected, two from Sagami Bay that Ortmann (1890) had placed in Escharoides, and one from Akkeshi that Androsova (1958) had described as Porella variabilis. I concluded that Buchneria dofleini is a junior synonym of Escharoides teres Ortmann, 1890; selected a lectotype for Escharoides teres among Ortmann’s syntypes; and established the new combination Buchneria teres (Ortmann, 1890), which becomes the type species of Buchneria. I also established the new combination Buchneria rhomboidalis (Ortmann, 1890) and selected a lectotype among Ortmann’s syntypes. Porella variabilis is transferred to Buchneria establishing the new combination Buchneria variabilis (Androsova, 1958). Here the three new combinations are redescribed and a key to the Japanese Buchneria species is provided. Finally, I transferred Buchneria to Bryocryptellidae on the basis of ovicell and orifice morphology. Therefore, Buchneria now includes a total of three species; Buchneria sinuata Harmer, 1957, a species from Indonesia that has hitherto been placed in this genus, is almost certainly not congeneric with other Buchneria. As far as is now known, Buchneria is endemic to northern Japan and the northern Sea of Japan.

Diversity of Freshwater and Marine Bryozoans in Japan

Bryozoans comprise a phylum of clonal, modular animals that inhabit marine and freshwater environments, with more than 6000 living species described. The long latitudinal range of Japan across several climatic zones and a complex nearshore bottom topography have resulted in high bryozoan diversity, which may exceed 1000 species. Bryozoan diversity has been studied in Japan from the late nineteenth century to the present. Revisional studies of historical collections and taxonomic inventories in previously uninvestigated localities and poorly studied habitats such as the intertidal zone and deep sea will increase our knowledge of bryozoan diversity in Japanese waters. This chapter reviews the history of Japanese bryozoan research and summarizes the diversity of bryozoans in this region.

The life of the freshwater bryozoan Stephanella hina (Bryozoa, Phylactolaemata)—a crucial key to elucidating bryozoan evolution

BackgroundPhylactolaemata is the earliest branch and the sister group to all extant bryozoans. It is considered a small relict group that, perhaps due to the invasion of freshwater, has retained ancestral features. Reconstruction of the ground pattern of Phylactolaemata is thus essential for reconstructing the ground pattern of all Bryozoa, and for inferring phylogenetic relationships to possible sister taxa. It is well known that Stephanella hina, the sole member of the family Stephanelllidae, is probably one of the earliest offshoots among the Phylactolaemata and shows some morphological peculiarities. However, key aspects of its biology are largely unknown. The aim of the present study was to analyze live specimens of this species, in order to both document its behavior and describe its colony morphology.ResultsThe colony morphology of Stephanella hina consists of zooidal arrangements with lateral budding sites reminiscent of other bryozoan taxa, i.e., Steno- and Gymnolaemata. Zooids protrude vertically from the substrate and are covered in a non-rigid jelly-like ectocyst. The latter is a transparent, sticky hull that for the most part shows no distinct connection to the endocyst. Interestingly, individual zooids can be readily separated from the rest of the colony. The loose tube-like ectocyst can be removed from the animals that produces individuals that are unable to retract their lophophore, but merely shorten their trunk by contraction of the retractor muscles.ConclusionsThese observations indicate that S. hina is unique among Phylactolaemata and support the notion that bryozoans evolved from worm-like ancestors. In addition, we raise several arguments for its placement into a separate family, Stephanellidae, rather than among the Plumatellidae, as previously suggested.

Distribution and Diversity of Erect Bryozoan Assemblages Along the Pacific Coast of Japan

To assess factors involved in the high diversity of benthic fauna in Sagami Bay, we examined the species composition of bryozoans forming rigidly erect colonies, possibly occuring in dense assemblages called bryozoan thickets. We identified erect bryozoans from collections made in the bay in four time intervals over ~125 years. To examine latitudinal effects on diversity, we also identified specimens in collections from near Otsuchi Bay to the north and the Nansei Islands to the south. In addition, we compared the composition and diversity of erect bryozoans in Sagami Bay with those in bryozoan thickets at Otago Shelf, New Zealand. We categorized erect bryozoans into five form categories based on the colony morphologies; detected 17 species in representing the five forms in Sagami Bay, five species representing four forms in the Nansei Islands, and three species representing two forms at Otsuchi Bay. Erect bryozoan diversity thus did not show a latitudinal gradient; it was higher in Sagami Bay than farther north or farther south, though we cannot rule out sampling effects. We speculate that the high diversity in Sagami Bay is due to greater environmental complexity than the other areas, including warming and cooling influences from the Kuroshio and Oyashio Currents, respectively, in different parts of the bay. We detected no clear differences in species composition between eastern and western Sagami Bay, but did detect an apparent loss of diversity of four species overall and nine species in western Sagami Bay between the 1928–1988 and the 2001–2005 intervals, suggesting differential environmental changes in different parts of the bay. Sagami Bay was richer in rigidly erect species than the bryozoan thickets at Otago Shelf, though the same colony morphologies were represented.