The feeding ecology and reproductive cycle of the sea cucumber Cucumaria frondosa (Gunnerus) from the Bay of Fundy.

摘要

Preliminary observations indicated that Cucumaria frondosa (Gunnerus) in the Bay of Fundy did not feed throughout the year; hence, the overall objectives of this project were: (a) to determine the factors influencing feeding activity using laboratory experiments and in situ video monitoring; and (b) to correlate the seasonal feeding activity with the reproductive cycle. In laboratory experiments, sea cucumbers were exposed to different chloropigment concentrations by manipulating the seston concentration. As seston chloropigment concentration increased, the percentage of sea cucumbers feeding increased reaching a maximun before leveling off. Tentacle insertion rate of sea cucumbers increased with seston chloropigment concentration and up to a critical level, the amount of chloropigment in sea cucumber stomachs also increased.;Field observations of Cucumaria frondosa at a shallow-water site revealed a seasonal rhythm. Sea cucumbers extended their tentacles and began feeding in March/April and ceased feeding in September/October. Daylength and seston quality explained most of the variability in percentage feeding. Feeding activity was not significantly related to the distinct annual temperature cycle. As in the laboratory, sea cucumbers increased their rate of tentacle insertion as seston quality increased, however, tentacle insertion rate was negatively related to the current velocity. Both long- and short-term observations indicate that seston quality is likely the major environmental variable influencing feeding activity.;Cucumaria frondosa displays an annual spawning season from May--July. Sea cucumbers from both shallow and deep sites displayed synchronous reproductive cycles. Clear indications of spawning were shown by decreases in gonad dry weight, volume fractions of tubule wall and spermatids, and by dramatic increases in testis haemal fluid. Tubule cross-sectional areas were smallest just after spawning. Spermatogenesis starts immediately after one spawning event and tubules became filled with spermatids and spermatozoa months before the next spawning. Different sized oocytes were always present in ovarian tubules, however, dramatic decreases in the occurrence of the largest oocytes occurred at spawning. Environmental factors explained more of the variability of the histological measurements in males than females. Correlations between histological measurements and feeding activity were low. Gametogenesis continues throughout the seasonal non-feeding period indicating the probable use of nutrient reserves.