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.

The role of circadian rhythm and environmental factors in the regulation of sea urchin spawning.

Simultaneous video recording of the sea urchin spawning behavior and recording of environmental factors enabled us to found synergism of the effects of circadian rhythm and phytoplankton on the spawning activity of the sea urchin Strongylocentrotus intermedius (Agassiz, 1864).

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.