Influence of sipunculan (peanut worm) activity on orifice formation in scleractinian Heterocyathus for adaptation to soft substrates.

Mutualism profoundly affects the morphology and ecological evolution of both hosts and symbionts involved. Heterocyathus is a solitary scleractinian coral that lives on soft substrata, and sipunculan worms live symbiotically in the tube-like cavities (orifice) inside the coral skeletons. This habitat provides protection to the sipunculan worms against predators and-owing to the mobility of the worms-prevents the coral from being buried with sediments. The orifice growth is closely related to the symbiont sipunculan worms; however, this has not been previously elucidated. Here, we clarified the growth process of scleractinian coral orifices and the influence of sipunculan activity on this. The orifices were originally formed by rapid accretion deposits. The coral soft tissue enveloping the growth edge of the orifice repeatedly retreated to the outer side due to direct damage to the soft part and/or excessive stress caused by the rubbing of the sipunculan through locomotion, excretion, and feeding behaviour. This resulted in a toppled-domino microskeletal structure appearance and maintenance of the orifice growth. These outcomes demonstrate the first example of the direct influence of symbionts on the skeletal morphogenesis of scleractinian corals. The mutualism between the two organisms is maintained by the beneficial confrontation in forming orifices.

Four new dendrochirotid holothurians collected from the Seto Inland Sea and the western part of the Sea of Japan, western Japan.

Fifteen dendrochirotid holothurians, including four new species, were collected from the Seto Inland Sea and the western part of the Sea of Japan, western Japan by the training and research vessel (TR/V) TOYOSHIO MARU of Hiroshima University, during the 201415 surveys. Massinium toyoshiomaruae sp. nov., Thyone kyushuensis sp. nov., T. liaoi sp. nov., and T. toyoshiomaruae sp. nov. are described as new species. Massinium toyoshiomaruae sp. nov. is readily distinguishable from all congeners by the absence of bodywall ossicles and the presence of table ossicles in the tentacle base. Thyone kyushuensis sp. nov. possesses large polyporous-tables in the introvert and tentacles, bodywall ossicles of a peculiar shape, and tentacle ossicles comprised mostly of unbranching rods and/or rod-like rosettes, which differ from those of all congeners. Thyone liaoi sp. nov. resembles T. pedata Semper, 1867 in its bodywall ossicles, however, it is distinguishable by the absences of huge ossicles in the body wall and the needle-shaped ossicles in the gonadal tubules. Thyone toyoshiomaruae sp. nov. is distinguishable from all other Thyone by the presence of the peculiar shape of the bodywall ossicles. Partial sequences of the mitochondrial cytochrome c oxidase subunit I gene are provided from the type specimens of the new species as DNA barcoding data.

Evolutionary Modification of Pereopods in Phronimid Amphipods (Crustacea: Amphipoda: Hyperiidea: Phronimidae) Reflects Host Differences.

Phronimid amphipods are oceanic crustaceans associated with gelatinous zooplankters. Their host organisms belong mainly to two taxonomic groups: tunicates (salps or pyrosomes; subphylum Tunicata) and siphonophores (Cnidaria). After these amphipods devour the inner tissues of their hosts, they display the unique behavior of modifying their hosts into hollow barrel-shaped shelters, which are then utilized as neonatal nurseries by the females. Although previous studies have revealed the host specificity of these amphipods, it has not been inferred which types of hosts ancestral phronimids could have originally used. Moreover, morphological changes associated with host switching have not yet been studied. To deduce the evolutionary patterns of host switching, we investigated the phylogenetic relationships of phronimid species by using two genes: (1) cytochrome c oxidase subunit I (COI) and (2) 18S ribosomal RNA (18S). In addition, a morphometric analysis was conducted in order to better understand the morphological relationships between phronimids and their host organisms. Our phylogenetic analysis suggests that the ancestral host animals of phronimids could have been tunicates and that the host organisms have independently switched from tunicates to siphonophores at least twice in the family Phronimidae. Our morphometric analysis revealed that phronimids using siphonophores as hosts have a relatively shorter pereopod 5 compared to those using tunicates. The shortening of pereopod 5 seems to be an adaptation to the narrower internal space of siphonophore barrels compared to those of tunicates.

Pulsed Terahertz Radiation for Sensitive Quantification of Carbonate Minerals.

Quantification of natural carbonate minerals, namely, aragonite, high- and low-Mg calcite, and dolomite provides essential information about biomineralization, carbon cycling on Earth, and the evolution of ocean chemistry, and is also useful in many other scientific, pharmaceutical, and industrial fields. However, X-ray diffractometer has previously been the only practical tool to identify and quantify carbonate minerals, including calcium carbonate (CaCO3) polymorphs. We propose new fingerprint terahertz (THz) absorption and reflective index spectra in the 1-6 THz range that probe the lattice phonon modes and can be used for sensitive quantification of these four carbonate minerals, including polymorphs. In THz time-domain spectroscopy with our unique attenuated total reflection system, high- and low-Mg calcite and aragonite show different absorbance and reflective index amplitudes at 3.32 THz, which corresponds to the transverse optic mode. Dolomite shows a distinct absorbance peak and reflective index at 4.82 THz because its space group (R3̅) is different from that of calcite (R3̅c). THz absorbance and reflective index curves of the mixed carbonate materials, which typically occur in natural environments, correspond well to the curves calculated from the results of single-mineral samples (R 2 > 0.98). Remarkably, the absorbance and reflective index can quantify small fractions (<1%) of low-Mg calcite in an aragonite matrix with high linearity (R 2 = 0.99). Our findings provide a new method for screening low-Mg calcite diagenetic overprints on primary aragonitic skeletons such as corals, which is crucial for climate reconstructions using the isotopic analyses because a 1% overprint can cause estimated temperature deviations of ∼1 °C. THz spectra of carbonate minerals offer not only a new high-sensitivity quantification tool for interdisciplinary fields, but also safer light-source handling than X-ray diffractometer.

New records of six deep-sea caridean shrimps (Crustacea: Decapoda) from the Ryukyu Islands and its adjacent waters, southwestern Japan.

Six species of caridean shrimps from four families are recorded from Japanese waters for the first time on the basis of material from the Ryukyu Islands and its adjacent waters, collected during research cruises of the T/RV "Toyoshio-maru" of Faculty of Applied Biological Science, Hiroshima University: two species of Crangonidae, Lissosabinea unispinosa Komai, 2006 and Pseudopontophilus serratus Komai, 2004; one species of Oplophoridae, Systellaspis pellucida (Filhol, 1885); one species of Pandalidae, Calipandalus elachys Komai Chan, 2003; and two species of Pasiphaeidae, Pasiphaea debitusae Hayashi, 1999 and P. gracilis Hayashi, 1999. Of them, L. unispinosa, Pseudopontophilus serratus, Pasiphaea debitusae and P. gracilis are heretofore known from the South-West Pacific localities, and then the geographical ranges of these four species are greatly extended to the north and west. Illustrations and/or colour images are provided for each species to supplement previous descriptions and to give evidence for identification.