A new Sphaeronella species (Copepoda: Siphonostomatoida: Nicothoidae) parasitic on Euphilomedes sp. (Ostracoda: Myodocopa: Philomedidae) from Hokkaido, Japan, with an 18S molecular phylogeny

With about 80 species, Sphaeronella is the most species-rich genus in the copepod family Nicothoidae. To date, 20 named Sphaeronella species have been reported as ectoparasites on ostracod crustaceans. Here we describe Sphaeronella uyenoi sp. nov. parasitic on the philomedid ostracod Euphilomedes sp. collected from Akkeshi Bay, Hokkaido, Japan, northwestern Pacific. Sphaeronella uyenoi most closely resembles S. monothrix (Bowman & Kornicker, 1967), parasitic on the cylindroleberidid Parasterope pollex Kornicker in Bowman & Kornicker in the northwestern Atlantic, but differs from the latter in having (1) the submedian skeleton containing paired, strongly chitinized, Λ-shaped areas and paired wide oblong holes bearing a strongly chitinized fringe posteriorly, and (2) maxillipedal segment 3 with antero-subdistal serration. We determined partial sequences for the cytochrome c oxidase subunit I (COI) and 18S rRNA (18S) genes for S. uyenoi and constructed an 18S-based phylogenetic tree of copepods. In our tree, Nicothoidae was not monophyletic, and S. uyenoi was the sister taxon to Cancerilla sp. in Cancerillidae (ectoparasites on brittle stars)

A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella

BackgroundXenoturbella is a group of marine benthic animals lacking an anus and a centralized nervous system. Molecular phylogenetic analyses group the animal together with the Acoelomorpha, forming the Xenacoelomorpha. This group has been suggested to be either a sister group to the Nephrozoa or a deuterostome, and therefore it may provide important insights into origins of bilaterian traits such as an anus, the nephron, feeding larvae and centralized nervous systems. However, only five Xenoturbella species have been reported and the evolutionary history of xenoturbellids and Xenacoelomorpha remains obscure.ResultsHere we describe a new Xenoturbella species from the western Pacific Ocean, and report a new xenoturbellid structure - the frontal pore. Non-destructive microCT was used to investigate the internal morphology of this soft-bodied animal. This revealed the presence of a frontal pore that is continuous with the ventral glandular network and which exhibits similarities with the frontal organ in acoelomorphs.ConclusionsOur results suggest that large size, oval mouth, frontal pore and ventral glandular network may be ancestral features for Xenoturbella. Further studies will clarify the evolutionary relationship of the frontal pore and ventral glandular network of xenoturbellids and the acoelomorph frontal organ. One of the habitats of the newly identified species is easily accessible from a marine station and so this species promises to be valuable for research on bilaterian and deuterostome evolution

Multiple processes generate productivity–diversity relationships in experimental wood-fall communities

Energy availability has long been recognized as a predictor of community structure, and changes in both terrestrial and marine productivity under climate change necessitate a deeper understanding of this relationship. The productivity–diversity relationship (PDR) is well explored in both empirical and theoretical work in ecology, but numerous questions remain. Here, we test four different theories for PDRs (More-Individuals Hypothesis, Resource-Ratio Theory, More Specialization Theory, and the Connectivity–Diversity Hypothesis) with experimental deep-sea wood falls. We manipulated productivity by altering wood-fall sizes and measured responses after 5 and 7 years. In November 2006, 32 Acacia sp. logs were deployed at 3203 m in the Northeast Pacific Ocean (Station Deadwood: 36.154098° N, 122.40852° W). Overall, we found a significant increase in diversity with increased wood-fall size for these communities. Increases in diversity with wood-fall size occurred because of the addition of rare species and increases of overall abundance, although individual species responses varied. We also found that limited dispersal helped maintain the positive PDR relationship. Our experiment suggests that multiple interacting mechanisms influence PDRs

Tube-constructing paratanaoidean tanaidaceans (Crustacea: Peracarida): a brief review

This study summarizes previous reports of tubes constructed with thread or mucus by paratanaoidean tanaidaceans. A literature survey found 34 genera in 14 extant families to contain species with for which information exists on tubes, whereas five families (Akanthophoreidae, Heterotanoididae, Paranarthrurellidae, Pseudozeuxidae, and Teleotanaidae) lacked any records of tube-use

Review of the Taxonomy, Diversity, Ecology, and Other Biological Aspects of Order Tanaidacea from Japan and Surrounding Waters

The order Tanaidacea is a group of benthic crustaceans, most of which are small, up to a few millimeters long. Tanaidaceans are distributed worldwide, with more than 1,200 described species. Following the first taxonomic paper on a Japanese tanaidacean in 1936, many researchers have studied their taxonomy, morphology, reproductive biology, or ecology in the waters around Japan. This chapter presents a brief introduction to tanaidaceans and then reviews what is known of their systematics (taxonomy and phylogeny), biology (including feeding habits, phenology, morphology, reproductive modes, parasites, predators), and ecology in Japan. The chapter ends with a summary and prospects for future research. The general conclusion is that tanaidaceans have been under-studied, both globally and within Japan; the 104 nominal species reported from around Japan and the 1,200 species reported globally likely represent a fraction of the actual diversity. The phylogeny of tanaidaceans is largely unresolved at all taxonomic levels. Recent, significant new discoveries dealing with herbivory, selfing, skin-digging activity in holothuroid hosts, possible sound production, and tube building suggest that much remains to be learned about their general biology

Descriptions of two new species of Rhizorhina Hansen, 1892 (Copepoda: Siphonostomatoida: Nicothoidae) parasitic on tanaidacean crustaceans, with a note on their phylogenetic position

Two new species of nicothoid copepod are described. Rhizorhina ohtsukai n. sp. found on a leptocheliid (Leptochelia sp.) collected at depths of 151-136 m in the North Pacific Ocean is most similar to Rhizorhina aesthetes Boxshall & Harrison, 1988 but can be distinguished by the possession of a narrower body with a rounded anterior end, and in the position of the gonopores. Rhizorhina soyoae n. sp. found on an apseudid (Fageapseudes sp.) collected at depths of 1,595-1,557 m in East China Sea most closely resembles Rhizorhina tanaidaceae Gotto, 1984 but differs in having a narrower body with a rounded anterior end. Partial nucleotide sequences of the cytochrome c oxidase subunit I (COI) gene were obtained from the two copepods in order to enable future barcoding. A phylogenetic reconstruction based on the 18S rRNA gene placed the copepods within the Siphonostomatoida Burmeister, 1835, with the nicothoid Choniosphaera maenadis (Bloch & Gallien, 1933), and separate from the Rhizorhina spp. clade, suggesting that the family Nicothoidae Dana, 1849 is not monophyletic. This is the third report of copepods parasitic on tanaidacean crustaceans

Shell-Exchange Behavior in a Hermit-Crab-Like Tanaidacean (Crustacea : Malacostraca)

This study describes shell-exchange behavior in the hermit-crab-like tanaidacean Macrolabrum sp. (Pagurapseudidae: Pagurapseudinae) under captive conditions. I observed one shell exchange by Macrolabrum sp., the behavioral sequence of which was as follows: a shell-carrying tanaidacean 1) grasped the edge of the aperture of an empty gastropod shell with its right cheliped; 2) inspected the condition inside the shell four times by inserting the anterior portion of its body into the shell; and 3) moved into the shell, posterior end (pleotelson) first. The elapsed time from the initial grasping of the empty shell to completing the move into it was 2 min 20 sec. In contrast to a Pagurapseudes tanaidacean and hermit crabs, the individual of Macrolabrum sp. did not examine the external surface of the shell during the single shell exchange observed

Digenean Metacercariae Parasitic in a Staurozoan Cnidarian

I report digenean metacercariae from Staurozoa, which were not previously known as digenean hosts. The host species, Haliclystus tenuis Kishinouye, 1910, was collected from algae in Oshoro Bay, Hokkaido, Japan, and contained metacercariae in the mesoglea. The metacercariae were encysted; cysts were oval, 93 μm long by 64 μm wide in one live individual. For the digenean, I generated partial sequences for the 18S rRNA (1585 bp) and 28S rRNA (1672 bp) genes, and the region spanning the 3′ end of the cytochrome c oxidase subunit gene and the 5′ end of the 16S rRNA gene, including the threonine tRNA gene (868 bp in total). Phylogenetic reconstructions based on combined 18S+28S datasets showed the digenean to belong in Opecoelidae, members of which utilize marine or freshwater teleost fishes as definitive hosts, and placed it in Plagioporinae (sensu lato) clade C within Opecoelidae

Haimormus shimojiensis, a new genus and species of Pseudozeuxidae (Crustacea: Tanaidacea) from a submarine limestone cave in Northwestern Pacific

We establish a new pseudozeuxid genus Haimormus gen. nov. based on a new species Haimormus shimojiensis sp. nov. which was collected from a submarine limestone cave with the entrance at 35 m depth, in the Northwestern Pacific Ocean. H. shimojiensis differs from the other confamilial members, Pseudozeuxo belizensis Sieg, 1982 and Charbeitanais spongicola Bamber & Bird, 1997, in having the pleonite 1 without the pleopod, the pereopods 2 and 3 propodus with a ventral spiniform seta, and the pereopods 4-6 propodus with one long and two short dorsodistal setae. A key to females of species of Pseudozeuxidae is presented. This is the first tanaidacean report from submarine caves around Japan

Apseudes ranma sp. nov. (Tanaidacea: Apseudidae) found in a public aquarium, with notes on phylogeny and a presumptive stridulatory organ

We describe Apseudes ranma sp. nov. from the Port of Nagoya Public Aquarium, Nagoya, Japan. It resembles two congeners, Apseudes curtiramus (Guţu, 2007) and Apseudes orghidani Guţu and Iliffe, 1989, in having the rostrum triangular, wider than long, the carapace without lateral spines, distinct and round eye lobes, pereonites 3–6 with a pair of tongue-shaped anterolateral projections, and the pleotelson with two pairs of lateral projections, but differs from them in having lateral setae on the anterolateral margin of the carapace and a ventro-subproximal spine on the pereopod-1 basis, and in the number of spiniform setae on articles of pereopods 2–4. We determined partial nucleotide sequences for the cytochrome c oxidase subunit I (COI) and 18S rRNA (18S) genes in A. ranma sp. nov. for future DNA barcoding and phylogeny reconstruction. In an 18S tree, A. ranma sp. nov. was the sister taxon to Apseudes nipponicus Shiino, 1937, and this clade was the sister group to moderately supported Carpoapseudes clade. We discovered a presumptive stridulatory organ in A. ranma sp. nov. consisting of a cylindrical protrusion and knobbly area on the inner surface of each of the left and right chelipedal bases. The location of the protrusion and knobbly area suggests that these may be a plectrum and pars stridens, respectively