Quantitative study of the behavior of two broadcast spawners, the sea urchins and , during mass spawning events in situ.

Background: The spatial distribution of spawners and temporal parameters of spawning in motile invertebrates with external fertilization might influence reproductive success. However, to date, data on the prespawning and spawning behaviors of broadcast spawners in the field have been scarce and mostly qualitative. The present study was intended to clarify the behavioral adaptations of two sea urchin species, and , using quantitative analysis of their behavior during mass spawning events under natural conditions.

Long-term study of behaviors of two cohabiting sea urchin species, and , under conditions of high food quantity and predation risk in situ.

Background: In the predator-sea urchin-macrophyte trophic cascade, the ecological effect of sea urchins as grazers depends both on their density and the changes in foraging activity, which are influenced by various disturbing factors. However, the complete duration of the alarm reactions of echinoids has not been studied until now. Here, we tested a hypothesis that two cohabiting sea urchins, and , which differ morphologically, might display different behavioral responses to high hydrodynamic activity and predation.

Lipofuscin-like pigment in gonads of Sea Urchin Strongylocentrotus intermedius as a potential biomarker of marine pollution: a field study.

Accumulation of lipofuscin-like pigments (LLPs) has been shown to be an appropriate index of both age and stress in some aquatic invertebrates. In the present study, LLP was quantified by measuring its autofluorescence intensity (ex 450 nm/em 512 nm) in nutritive phagocytes (NPs) of sea urchins Strongylocentrotus intermedius inhabiting polluted and relatively clean areas of Japan Sea. To avoid variations in LLP content related to sea urchin reproductive condition, only developing gonads with acini occupied mostly by NPs were used for LLP quantification as well as semiquantitative histopathological analysis.

Neuroplastic and neuropathological changes in the central nervous system of the Gray mussel Crenomytilus grayanus (Dunker) under environmental stress.

We studied here neuron ultrastructure, synaptic plasticity and subcellular localization of NADPH-diaphorase (NADPH-d), a cytochemical marker for nitric oxide syntase, in the pedal ganglia of the Gray mussel Crenomytilus grayanus sampled from the polluted and reference sites in Amursky Bay (Sea of Japan) at lower and higher water temperature (in the beginning and the end of August, respectively). At lower temperature, neuroplastic changes in mussel ganglia prevailed: a sharp increase in the number of cytosomes in NADPH-d-positive neurons and a sharp decrease in the number of mitochondria in both NADPH-d-positive and NADPH-d-negative neurons. At higher temperature, neurodegenerative changes prevailed: disruption of a part of NADPH-d-negative axons and interneuronal contacts, formation of concentric lamellar structures in the neuropils, and accumulation of autophagosomes in NADPH-d negative neurons.

Morphology of spermatogenic and accessory cells in the mussel Modiolus kurilensis under environmental pollution.

A comparative light- and electron microscopic study of the male gonads of the bivalve mollusk Modiolus kurilensis from the reference and polluted sites in Amursky Bay (Sea of Japan) was conducted. Testicular acini in the mussels from the reference site had well-ordered structure (vertical spermatogenic columns located among the accessory cells bodies) whereas in the testes of the mollusks from the polluted site, the accessory and spermatogenic cell populations were disarranged. Mussels from the polluted station had about 26% of spermatogenic cells with marginal localization of nuclear chromatin, swollen outer nuclear membrane and heavily vacuolated cytoplasm and about 8% of spermatozoa with transformed or destructed acrosome; in mussels from the reference station, these values were close to zero.