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Sexual reproduction of the cyanobacteriosponge, Terpios hoshinota, was studied at Lyudao (Green Island), Taiwan, from 2011 to 2013 through histological examinations, electron microscopy, and in situ observations of larval release. Histological examinations identified five reproductive structures: oocytes, sperm cysts, cell masses, early-stage embryos, and mature embryos. These reproductive structures were often observed in the same specimens, indicating that T. hoshinota is a hermaphroditic brooder. No cyanobacteria were seen in the gametes, and transmission of symbiotic cyanobacteria from parental tissues to larvae likely occurred during embryogenesis. The cell mass, a loose aggregate of numerous symbiotic cyanobacteria and maternal sponge cells, appeared to be eventually incorporated and constitutes the inner part of pre-hatching larvae, suggesting that the larval type is pseudoblastula instead of parenchymella as previously suggested. A clear lunar periodicity was seen in the reproductive cycle; larvae were released mostly around the full moon and occasionally around the new moon. Reproductive activity declined during months with low temperatures (January-April). The larvae were characterized by negative buoyancy and limited mobility, suggesting a larval dispersal distance on a scale of meters under calm weather. However, long-distance dispersal of larvae could still be possible through occasional strong currents during bad weather, such as typhoons, if the larvae survived during the dispersal period by accessing extra energy from the symbiotic cyanobacteria through their photosynthates and/or consuming the cyanobacteria as a source of nutrients. This study showed that T. hoshinota has high fecundity, with a monthly release of numerous larvae over a long reproductive season. This high fecundity, along with local larval dispersal and rapid post-settlement growth, enables rapid population expansion of T. hoshinota. [ABSTRACT FROM AUTHOR]

Species of the genus Dendrodoris are defined as 'radula-less' dorids (Nudibranchia: Doridina: Porostomata: Dendrodorididae). These sea slugs are colorful nudibranchs distributed across the world's oceans. Because of color variations and anatomical similarities, species discrimination has been disputed in several Dendrodoris species. We determined the partial mitochondrial COI gene sequences and 18S rRNA gene sequences of five Dendrodoris species ( D. arborescens, D. denisoni, D. guttata, D. nigra, and D. rubra) and Doriopsilla miniata in Japan to clarify the species identity of each dendrodorid species. We examined a total of 50 specimens from the intertidal zone at 10 sites in four regions along the Pacific coast of Japan. Partial COI gene sequences significantly differed among the six species. Although six partial 18S rRNA gene sequences were obtained for the six species, sequences differed little among species and did not clarify details of the Dendrodoris phylogeny. We also described the morphological features of veliger larvae of three Dendrodoris species. ( D. arborescens, D. guttata, and D. rubra) The veligers of D. arborescens had a brown-pigmented, cup-shaped shell, and its foot was not retracted into the shell. In contrast, the veligers of D. guttata and D. rubra had a transparent, coiled shell with an operculum. Mean shell lengths of D. arborescens, D. rubra, and D. guttata were 171.5 ± 8.0, 172.8 ± 4.9, and 222.3 ± 15.2 μm, respectively. The present molecular analysis and larval characteristics indicated that each of the six species is a distinct species. [ABSTRACT FROM AUTHOR]

Peltogasterella sensuru n. sp. infests Pagurixus hermit crabs inhabiting rocky shores off Okinawa Island (Ryukyu Archipelago, Japan). This species is clearly distinguishable from Peltogasterella gracilis (Boschma, 1927): the stalk emerges from the middle part of the externa in the present species and P. sulcata (Lilljeborg, 1859), while the stalk in P. gracilis emerges from the posterior end of the externae. The new species differs from P. sulcata based on the morphology of the mantle aperture. Peltogasterella sensuru n. sp. repeatedly produces single brood externae that have not been previously observed in species belonging to the suborder Kentrogonida Delage, 1884. We also determined partial sequences of the COI gene and 16S rRNA gene of the new species for use as molecular markers for species identification. [ABSTRACT FROM AUTHOR]

The life cycle of the fish ectoparasitic isopod Gnathia trimaculata is described based on both field samplings and laboratory observations. Species identification of the larvae was based on morphological observation and supported by molecular analysis. As the results of field samplings in several sites of southwestern and central Japan (24-34°N, 124-139°E) from 2005-2011, approximately 900 third-stage larvae of G. trimaculata were found on 25 elasmobranch species, and 220 first- and second-stage larvae were found on three teleost species. No third-stage larvae were found on the teleosts, and the larvae of younger stages never infested elasmobranchs. Therefore, G. trimaculata is supposed to shift its host from teleosts to elasmobranchs as it develops. We discuss the developmental periods, life span, distribution, and predation risk of the present species compared with other gnathiid species. [ABSTRACT FROM AUTHOR]

postanal tail is a major synapomorphy of the phylum Chordata, which is composed of three subphyla: Vertebrata, Cephalochordata, and Tunicata (Urochordata). Among tunicates, appendicularians are the only group that retains the tail in the adult, and the adult tail functions in locomotion and feeding in combination with a cellulose-based house structure. Given the phylogenetic position of tunicates, the appendicularian adult tail may possess ancestral features of the chordate tail. We assess the ultrastructural development of the tail epidermis of the appendicularian Oikopleura dioica. The epidermis of the larval tail is enclosed by the larval envelope, which is a thin sheet similar to the outer tunic layer of ascidian larvae. The epidermis of the adult tail seems to bear no tunic-like cellulosic integuments, and the tail fin is a simple folding of the epidermis. Every epidermal cell, except for the triangular cells at the edge of the tail fin, has a conspicuous matrix layer of fibrous content in the apical cytoplasm without enclosing membranes. The epidermis of the larval tail does not have a fibrous matrix layer, suggesting the production of the layer during larval development and metamorphosis. Zonulae adhaerentes firmly bind the epidermal cells of the adult tail to one another, and the dense microfilaments lining the cell borders constitute a mechanical support for the cell membranes. The intracellular matrix, cell junctions, and cytoskeletons probably make the tail epidermis a tough, flexible shell supporting the active beating of the oikopleuran adult tail. [ABSTRACT FROM AUTHOR]

The native form of cellulose is a fibrillar composite of two crystalline phases, the triclinic I and monoclinic I allomorphs. Allomorph ratios are species-specific, and this gives rise to natural structural variations in cellulose crystals. However, the mechanisms contributing to crystal formation remain unknown. We show that the two crystalline phases of cellulose are tailored to distinct structures during different developmental stages of the tunicate chordate Oikopleura dioica. Larval cellulose consisting of I allomorph constitutes the body cuticle fin, whereas adult cellulose consisting of I allomorph frames a mucous filter-feeding device, the 'house.' Both structures are secreted from the epidermis in accordance with the mutually exclusive expression patterns of two distinct putative cellulose synthase genes. We discuss a possible linkage between structural variations of the crystalline phases of cellulose and the underlying evolutionary genetics of cellulose biosynthesis. [ABSTRACT FROM AUTHOR]

Zoanthids comprise an order of benthic, generally colonial cnidarians, which can usually be distinguished from other hexacorallians by embedded sand and detritus in their mesoglea to help strengthen their structure. These animals are becoming increasingly important research subjects in biochemistry and other research fields. Their inclusion of both calcium and silica results in the need for both decalcification and desilification for internal morphological examinations. Since the methodology of hydrofluoric acid (HF) desilification has rarely been documented in zoanthids, histological surveys for zoanthid taxonomy have often been abandoned and their taxonomy is often problematic. Recent investigations utilizing molecular methods have brought a clearer understanding of zoanthid diversity, but standardization of HF treatments are still needed to provide a link between molecular and more traditional techniques, and to properly examine specimens for which molecular methods may not be an option (e.g., formalin-preserved specimens, etc.). Here, we use both 'straight' HF and, for the first time with zoanthids, buffered HF (BHF) treatments at different treatment lengths (1-48 h) on polyps from three different species of zoanthids for histological examination. Section conditions were judged based on the presence/absence of embedded detritus, drag marks, and tissue condition. Results show that the BHF treatment resulted in slightly better tissue conditions for all specimens, and suggest that desilification works well regardless of treatment time for species with smaller (polyp diameter <0.5 cm), less heavily encrusted polyps. Desilification of heavily encrusted Palythoa mutuki polyps were still problematic, with at least 24 h treatment needed. To aid future research, we provide guidelines for HF treatments of zoanthid specimens. [ABSTRACT FROM AUTHOR]

Monthly samplings of solitary entoprocts were carried out at Mizugama and Ginowan Fishery Port, Okinawa Island, the central Ryukyus, Japan from November 2000 to November 2001. We examined the entoproct populations on the glass slides that had been placed at the two sites for 2 months, and a total of 18,322 individuals of solitary entoprocts were recorded. They were Loxomitra mizugamaensis, L. ryukyuensis, L. tetraorganon, Loxosomella aloxiata, L. intragemmata, L. lecythifera, L. monocera, L. stomatophora, and Loxocorone allax. Our analyses indicate that (1) the abundance of solitary entoprocts in this region is high in summer and low in winter, (2) most species reproduce by budding all year round, and (3) sexual reproduction is restricted to a short period in summer (July or August). [ABSTRACT FROM AUTHOR]

In obligate symbioses between didemnid ascidians and prokaryotic algae (cyanobacteria), the larvae of the host ascidian usually possess Prochloron cells that are acquired from their mother colony. The process of vertical transmission of the photosymbionts has been histologically described in several species harboring Prochloron in the common cloacal cavity, where Prochloron cells are attached to the hairy surface of the tunic of the larvae during or just before larval spawning. Since the process has never been described in species harboring the photosymbionts in the tunic of the colony, here we describe the histological and ultrastructural process of vertical transmission in a photosymbiotic didemnid, Trididemnum miniatum. No photosymbionts were associated with gametes of the ascidian. Prochloron cells appeared in the epithelial pouch enclosing the embryo and were then incorporated in the tunic of embryos in late embryonic stages. Although Prochloron cells in the tunic of the colony were rarely associated with the host cells, some amoeboid-shaped tunic cells containing Prochloron cells were occasionally found around the epithelial pouch. Therefore, the host cell is thought to be a vehicle transporting the photosymbionts in the tunic of the colony to the tunic of the embryos. The photosymbiont cells were directly embedded in the tunic of the larval trunk. They were not contained in the host cells, as are those in the tunic of the colony. These observations revealed that the mechanism of vertical transmission in T. miniatum is very different from that in didemnids harboring Prochloron in the common cloacal cavity of the colonies, such as Trididemnum cyclops. The mechanisms of symbiont transmission are diverse even within the genus Trididemnum. [ABSTRACT FROM AUTHOR]

The contents of mycosporine-like amino acids (MAAs) were compared in the two color morphs (dark-gray and brown colonies) of the tropical ascidian Didemnum molle (Herdman, 1886), which harbors the photosymbiotic prokaryote Prochloron. The colonies of each color morph were exclusively distributed in shallow reef lagoons at the different sites. Spectroscopic and chromatographic analyses showed that the Prochloron cell density and MAA concentration in the dark-gray colonies were an estimated 1.4 and 2.4 times higher, respectively, than in the brown colonies. The significant difference in MAA contents between the color morphs was primarily due to the difference in shinorine contents ( p < 0.01, Mann–Whitney U-test). The high concentration of MAAs in the dark-gray colonies may provide better conditions for Prochloron cells, compared to the brown colonies with lower MAA concentrations. [ABSTRACT FROM AUTHOR]