Spermatophore and spermatozoal ultrastructure of the Mediterranean hermit crab Pagurus excavatus (Paguridae: Anomura: Decapoda)

• Published in: Journal of the Marine Biological Association of the United Kingdom 2013-08, Vol.93 (5), p.1363-1371
• Main Authors: Tirelli, Tina, Gamba, Marco, Pessani, Daniela, Tudge, Christopher C.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Anomura; Biological and medical sciences; Crustacea; Crustaceans; Decapoda; Females; Fundamental and applied biological sciences. Psychology; Invertebrates; Male reproductive system; Marine; Microscopy; Morphology; Paguridae; Paguroidea; Pagurus; Pagurus excavatus; Phylogenetics; Sea water ecosystems; Sperm; Synecology; Taxonomy; Testes
• ISSN: 0025-3154; 1469-7769
• DOI: 10.1017/S0025315412001877

The ultrastructure of the spermatophores and spermatozoa of the Mediterranean hermit crab Pagurus excavatus are described, using transmission electron microscopy. The size of the different parts of the spermatophore and spermatozoa are given and their ultrastructure described and compared to similar data already present in the literature for other hermit crabs. The morphology and ultrastructure of the spermatophore and spermatozoa of P. excavatus are species-specific, clearly distinguishing the species from the others already described. The spermatophore and spermatozoa show some similarities with those produced by other representatives of the genus. In particular, the tripartite spermatophore is divided into two halves by the lateral ridge and, as with the spermatophores produced by other species belonging to the genus Pagurus, it is morphologically very different from any other Paguroidea. The spermatozoa are composed of an ovoidal acrosomal vesicle capped by the operculum; the acrosome has a length:width ratio of approximately 1.75, therefore larger than 1 as reported for all anomurans studied to date. At the base of the acrosomal vesicle, there is the thin cytoplasm, the large nucleus and three arms positioned to form a 120° angle between each other. The present description is an important additional step allowing for better understanding of the relationships among the different hermit crab taxa.