Anomura

Morphological Diversity

Among the decapods, anomurans show the highest order of variability and complexity in spermatophore morphology. An interesting exception is that the anomuran genus Aegla lacks spermatophore in all the species studied so far. In Aegla platensis, males transfer unbound spermatozoa, instead of sper- matophores to females during mating (Sokolowicz et al., 2007). Anomuran spermatophores are pedunculate and structurally species-specific. Invariably, the spermatophores are attached to the female body to effect epizoic fertilization. Spermatophoric structure in anomurans can be broadly categorized into two major types. The superfamily Paguroidea, represented by the hermit crabs, produce a tripartite, pedunculate type of spermatophore, consisting of a sperm-bearing distal ampulla, raised on a stalk or peduncle, which is fixed on a gelatinous pedestal that is glued to the sternal region of the female during copulation (Tudge, 1999). Exceptions were observed in some species of the genus Clibanarius (family Diogenidae), where the stalk and the pedestal are absent (Uma and Subramoniam, 1984; Hess and Bauer, 2002).

The next type is found in Hippidae represented by mole crabs in which the spermatophore is ribbon-like, bearing resemblance to the macruran type of spermatophoric mass (Subramoniam, 1984; Tudge et al., 1999). Among the pedunculate type of anomuran spermatophores, the size and external morphology are relatively constant within a species, but vary between them, making these reproductive structures taxonomically useful for differentiating between closely related species. Phylogenetic relationship apart, variations found in the spermatophore morphology of anomuran crabs and the associated modes of sperm transfer mechanisms may be influenced by the habitat conditions in which these reproductive activities are accomplished (Subramoniam, 1993).

 
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