POST-LARVAL GROWTH OF DISSODACTYLUS PRIMITIVUS BOUVIER, 1917 (BRACHYURA: PINNOTHERIDAE) UNDER LABORATORY CONDITIONS

¹ Department of Zoology, University of Toronto, Ontario, Canada M5S 1A1

Dissodactylus primitivus is a small pinnotherid crab parasitic on spatangoid urchins. Post-larval growth has been observed in the laboratory in the absence of hosts. Individual animals were grown over the whole size range of the species for a period of 691 days after hatching. During growth of D. primitivus males and females, there was no significant change in carapace width with length. Relative to carapace width, male abdominal width increased isometrically. Growth of the female abdomen was allometric and could not be explained by a simple relationship. Two phases leading to sexual maturity were recognized: one of low positive allometry, the other of strong allometric growth. During the latter phase pubertal molts occurred.

Growth over time showed decreasing increments and an increase in intermolt periods, with slight differences between sexes. The resulting growth rates closely fitted power curves. Compared to females, growth of males decreased after the first year. This could explain the presence of larger females in natural populations.

Several growth relationships analogous to weight were demonstrated and the results discussed in relation to other Crustacea.