Reproduction

Finding a mate in the deep-sea is an enormous challenge for echinoderms due to low density of populations over an incredibly vast environment. Most deep sea echinoderms possess two separate sexes (gonochorism) between which external fertilization occurs, although the methods of reproduction are unclear (Lawrence and Herrera, 2000). Echinoderms of the deep sea have also adapted a range of reproductive patterns to ensure reproductive success including continuous reproduction, intermediate development and seasonal reproduction (Gage and Tyler, 1991).

Most deep sea brittle stars are thought to reproduce seasonally releasing pelagic larvae (Hendler and Tran, 2001). Seasonality in echinoderm reproductive cycles is thought to be controlled by the exogenous factors of food supply associated with sinking particulate matter resultant from seasonality in primary production of sea surface layers (Galley et al., 2008).

Some deep-sea Asteroidea display a seasonal pattern in breeding, employing the coupling of high fecundity with small egg size (Mercier and Hamel, 2008) while contrasting studies show no seasonality and large egg size in deep sea Asteroidea species (Benitez-Villalobos et al. 2007).

Evidence from studies has shown that some deep-sea holothurians will form breeding aggregations of 2-3 individuals all within a state of continuous reproduction producing large oocytes with large yolk supplies (Tyler et al. 1992).

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