Seasonal incidence of egg-bearing in the New Zealand paddle crab Ovalipes catharus (Crustacea: Brachyura), and its production of multiple egg batches

Abstract

The annual reproductive cycle of Ovalipes catharus (White) was investigated by determining the proportion of mature females carrying eggs, in samples of crabs taken at dusk every 4 or 5 weeks for 22 months from Plimmerton Beach, near Wellington, New Zealand. Three peaks of egg-bearing were found over each breeding season: the first during August, the second through late November and early December, and the last during early January into early April. The average carapace width (CW) of crabs carrying eggs was 84.6 ± 9.65 mm and this average did not alter significantly during the year. Smaller female crabs (41-60 mm CW) were found carrying eggs predominantly during January and February. Captive O. catharus were able to produce a maximum of five batches of eggs during one intermoult period, from a single insemination. The average number of egg batches produced increased with crab size. Crabs < 50 mm CW produced only one egg batch before moulting, whereas those > 90 mm CW produced an average of three batches. Overall, the mean number produced was 2.6 batches. The period of incubation and the inter-batch period for captive females each became as short as 2.5 weeks during December and January. This was about half the time taken at the beginning and end of the egg-bearing season. No evidence was found for retention of sperm between moults. © The Royal Society of New Zealand 1993.