Meeting Abstract

66.4  Wednesday, Jan. 6  Reversed asymmetry in lithodid crabs: an absence of evidence for heritability or induction DUGUID, W.D.; Univ. of Victoria

The mechanisms controlling development of left-right asymmetries remain an intriguing problem in developmental biology. Individuals exhibiting reversal of directionally asymmetric characters provide an opportunity to study these mechanisms and may also provide insight into evolutionary changes in asymmetry states. King crabs (family Lithodidae) exhibit a dramatic morphological handedness; both sexes have a larger right claw, and the female abdomen is deflected to the right. The first recorded capture of an egg-bearing female lithodid (Lopholithodes foraminatus) with reversed asymmetry of the claws and abdomen provided an opportunity to investigate possible heritability or induction of reversed asymmetry in lithodid crabs. A high incidence of reversed claw asymmetry (approximately 25%) was observed for the offspring of both reversed (n = 1) and normal (n = 3) females. Reversed claw asymmetry persisted through development and was correlated with development of reversed abdominal asymmetry in juvenile females. The direction of asymmetry could not be reversed through major claw removal, and the incidence of reversed asymmetry was apparently independent of larval rearing temperature. Reversed mandibular asymmetry was never observed in zoeae, or in either normal or reversed juveniles. This suggests that while the asymmetric development of the claws and abdomen are linked, they are separate from the primary asymmetry of the organism. The apparent absence of heritability for variation in the direction of asymmetry in L. foraminatus contradicts expectation. Further research on this subject may challenge assumptions about the evolution and development of bilateral asymmetries.