|The fundamentals of insemination in cirripedes|
Klepal, W. (1990). The fundamentals of insemination in cirripedes. Oceanogr. Mar. Biol. Ann. Rev. 28: 353-379
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Biological fertilization; Cirripedia [WoRMS]; Marine
Current knowledge of males in various stages of reduction and of the fundamentals of insemination in cirripedes is reviewed. Anatomical data (based on light and electron microscopy) as well as behavioural and theoretical aspects of reproduction are discussed. Interest focuses on the Cirripedia sensu stricto but Rhizocephala are also considered.Cirripedes are aberrant in having a penis which is not just a tube for the transfer of semen. It is a highly sensitive organ first involved in the search of the functional female, into whose mantle cavity the semen is then deposited. This process is called pseudo-copulation after which the penis degenerates in some species (Thoracica), while in others the male itself deteriorates (Thoracica, Acrothoracica). At the new breeding season the penis regenerates or new males become active, respectively.The cirrepede spermatozoon is unusual in having an elongate nucleus alongside the flagellum, a single mitochondrion, and a single centriole. An accessory droplet, species-specific in its structure, presumably assumes the function of multiple mitochondria in other spermatozoa.The question of whether hermaphroditism or gonochorism is the original type of reproduction in cirripedes is still a matter of discussion. Two possible pathways for the evolution of sexuality in cirripedes are discussed.