General ecology of the cassiduloid urchin Cassidulus caribbearum

摘要: Cassidulus caribbearum, a representative of the echinoid order Cassiduloida, occurs in localized populations high densities (up to 100 m-2) among islands Puerto Rico bank eastern Caribbean Sea. These small 35 mm) urchins are burrowers, principally shallow-water areas with coarse sand bottom. Locomotion is achieved by ditaxic waves, passing from front rear large movable spines on lateral portions ventral surface; this mechanism unique echinoids. Digging was most effective grain sizes closely approximating those environment (0 1ϕ). somewhat selective deposit feeders, which ingest substrate particles primarily size range 0 1ϕ. Individuals more or less continuously; complete passage through gut takes an average 6 h laboratory. Aristotle's lantern present young juveniles (test length <1.0 mm), but resorbed before reach test 5.0 mm. The shows similarities gross morphology spatangoid gut. Oxygen consumption comparable that other tropical echinoids similar wet weight. C. caribbearum broods its (350 μm) yolky eggs aboral for 10 12 days, at time crawl off into sand. Successive, overlapping produced, so frequently two different developmental stages single urchin. Single may brood continuously up 4 months more. Throughout year, least 50% all individuals over 18 mm were found brooding, maximum 85% brooding mid-summer. sex ratio population sampled greater than 5 females 1 male. No evidence protandric hermaphroditism found. Growth rate, measured tagged indivuduals and increase median samples, between 0.5 1.0 month-1. Mortality due predation gastropod Cassis tuberosa, although occasional, episodic mortality caused physical factors such as heavy storm swells.