The skeletal growth patterns of two irregular sea urchins, Astriclypeus manni (Verrill 1867) and Clypeaster japonicus (Döderlein 1885), widely distributed in the shallow coastal Jeju Island, were investigated in this study. After charring by flame and subsequent clearing with xylene, a series of light and dark bands appeared on the plates consisting oral and aboral tests of both species. A strong correlation was observed between the number of dark bands and the size of A. manni as a test diameter (TD, r²=0.921); as the number of dark band increased, TD increased logarithmically. From digitized image of the plate, the radius and area of each dark band was measured using an image analyzing software. The size of sand dollar was also positively correlated with radius of the plate (r²=0.886 for A. manni and r²=0.422 for C. japonicus) or area of the plate (PA, r²=0.904 for A. manni and r²=0.704 for C. japonicus). As the correlation coefficient indicated, PA was found to be a better estimation for the skeletal growth of the sand dollars. The proportion of each dark band area in a plate increased dramatically from the first band to the second and third band then it dropped gradually as the number of dark band increased. After the 7 or 8th bands, the area or radius could no longer be measured since the distance between the two adjacent bands become too close. It was believed that the alteration of dark and light bands appeared on the plate represents the annual or seasonal growth ring, as was reported from other sea urchins and the skeletal growth of the two sand dollars are possibly age-dependent.

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Associations between pycnogonids and the mesopelagic anthomedusan Pandea rubra are reported from two in situ video footage records off the Pacific coast of northern Japan, and from a plankton sample collected in the Weddell Sea (one juvenile of the pycnogonid Pallenopsis (Bathypallenopsis) tritonis). This is the first pelagic record of a pycnogonid in the Southern Ocean and the first record of an association between pycnogonids and a hydroidomedusa at mesopelagic depths. Taxonomic descriptions of both host and associate are given. Two early stages of a parasitic narcomedusa adhered to the medusan subumbrella are also reported. Possible origins for the pycnogonid-medusa association are postulated.

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Thraustochytrids are cosmopolitan osmotrophic or heterotrophic microorganisms that play, especially in coastal ecosystems, important roles as decomposers and producers of polyunsaturated fatty acids (PUFA), and are also known to be pathogens of mollusks and seaweeds. However, because of shortcomings in the current methods for detection and enumeration of thraustochytrids, very little information is available concerning their natural dynamics and ecological roles. In this study, we propose a new method for detecting thraustochytrids using a fluorescent 18S ribosomal RNA (rRNA)-targeted oligonucleotide probe (Probe ThrFL1). Detection of thraustochytrids by means of the fluorescence in situ hybridization (FISH) technique with ThrFL1 was specific; the probe did not react with the other stramenopile organisms or with the dinoflagellate that was tested. Because of the high specificity and intense reactivity, the FISH protocol is expected to be a strong tool for examining ecological features of thraustochytrids.

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Two tentaculate ctenophores were observed floating above the sediment at 7,217m depth in the Ryukyu Trench, Japan, anchored by a pair of long, flexible filaments emerging from the end of the animal opposite the simple tentacles. Several characters suggest taxonomic affinities to the genus Aulacoctena, and the taxonomic placement of this genus is reviewed and discussed with reference to recently collected material. In the light of this re-examination a new family is proposed to contain the genus Aulacoctena. The exact taxonomic placement of the enigmatic benthopelagic ctenophore species remains pending due to the difficulty of procuring samples from such abyssal depths with the recent loss of the world's only submersible platform rated below 7,000m—the ROV Kaiko.

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We isolated seven additional polymorphic microsatellites from the crown-of-thorns starfish, Acanthaster planci. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from 5 to 13 and the observed and expected heterozygosities ranged from 0.083 to 0.957 and from 0.082 to 0.872, respectively. After Mann-Whitney test, there was no significant difference in the number of alleles, the PCR efficiency, and the observed and expected heterozygosities between the newly developed 7 markers and the previously reported markers. We consider that these loci are potentially useful for detailing the genetic structure and gene flow among A. planci populations.

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