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Life History Pattens of the Littoral Gastropods Shaskyus Festivus (Hinds) and Ocenebra Poulsoni Carpenter (Prosobranchia: Muricidae)
Author(s) -
Fotheringham Nick
Publication year - 1971
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936023
Subject(s) - prosobranchia , muricidae , biology , littoral zone , predation , ecology , gastropoda , predator , reproduction , wader , whelk , zoology
Monthly recaptures of marked individuals in intertidal populations of the predatory gastropods Shaskyus festivus and Oceanebra poulsoni for 39 months near La Jolla, California, show annual variation in growth, reproduction, and recruitment rates consistent with the conclusion that the snails experienced only 1 successful year in 3. Eggs are deposited in capsules from March through July, and free—swimming veligers are released in 3 to 4 weeks. More than 99% of the mortality occurs in the plankton or during settlement. The major predator on the adults, the crab Cancer antennarius, annually destroys less than 1% of the adults Shaskyus and less than 2.5% of the adult Ocenebra. After settlement, Shaskyus can expect to live for more than 10 years, and Ocenebra for more than 9 years. The adult mortality rate was generally highest during the reproductive season but lowest in 1969, when the greatest reproductive effort was observed. Marked individuals of both species have been found in breeding aggregations in more than one season, suggesting iteroparity. Shell growth rates decreased and mortality rates increased as shell length increased in both species. The sex ratio of Shaskyus from 25.0 mm to 44.9 mm did not differ significantly from 1:1. The proporations of female Ocenebra longer than 14.9 mm increased as shell length increased. The determination of sex in smaller size classes was uncertain because many smaller males were probably immature and lacked penises. Sexual differences in growth and mortality rates were probably responsible for the paucity of males in the larger size classes. No evidence for sex reversal was found in repeated sex determinations of marked snails.