Spermiogenesis in Barnacles With Special Reference to Organization of the Accessory Body*

Abstract

Ultrastructural changes during spermiogenesis in the barnacles, Ba/anus amphitrite albicostatus, Balanus tintinnabulum rosa. BaIanus trigonus and Tetraclita squamosa japonica. and organization of the sperm with special reference to the accessory body were studied. The Golgi complex organizes both the acrosome and the accessory body at different stages during spermiogenesis; the former is formed at the mid-spermatid stage and the latter is formed at the late spermatid stage. The arrangement of the components in the mature filiform sperm is quite unique, with the acrosome, the basal body just behind the acrosome, the axial filament parallel to a long nucleus, and a slender long mitochondrion behind the nucleus. The sperm in the anterior and posterior half of the ejaculatory duct differ from each other in form in that the sperm in the anterior duct are not equipped with the accessory body and the sperm in the posterior duct are. The accessory body can be artificially broken down by some treatments (1 M urea, alkaline sea water: pH 9.0-9.7, low ionic concentration of sea water). The loss of the accessory body from the sperm is assumed to be related to the fertilizability of the sperm.The structure of the crustacean sperm is remarkably varied among members of the class. BROWN (6) described the various forms of the crustacean sperm following comparative and phylogenetic studies and emphasized that the sperm of the class Crustacea can be separated into two groups, the flagellated (Cirripedia, Branchiura, Mystacocarida) and nonflagellated sperm (Cephalocarida, Branchiopoda, Malacostrace). It is widely believed that, especially in Cirripedia barnacles, the sperm is filiform with an appendage that has been called the unique vesicle (11) or the large accessory droplet (10). Recently, we observed that the sperm collected from the male ejaculatory duct of some barnacles were swimming actively by flagellar motion, and that while part of them were equipped with the appendage we named the accessory body, part lacked it.The present study was carried out in order to determine (i) whether this morphological difference in the sperm depends on the maturation of the male germ cell, (ii) how the accessory body is organized during spermiogenesis and (iii) which types of sperm are effective in fertilization.

Sperm ultrastructure in the Cirripedia and its phylogenetic significance

“…61). Kubo et al (1979) mentioned that the droplet of Tetraclita squamosa was of 'dual texture', exhibiting spherical, differentiated zones, but we could find no clear evidence of this in our material (sea water/formalin-fixed). Droplet lengths range from 6.5 J.Ull in Epopella (Fig.…”

“…This study, in conjunction with other work on sperm ultrastructure in the Thecostraca (Bocquet -Vedrine & Pochon-Masson, 1969;Turquier & Pochon-Masson, 1969;Brown, 1970;Pochon-Massonetal., 1970;Pochon-Masson, 1971;Munn & Barnes, 1970a, 1970bKubo et al, 1979;Azevedo & Corral, 1982;Grygier, 1981Grygier, , 1982; also Anderson & Personne, 1970;Klepal, 1985), confirms that the Thoracica, Acrothoracica and Rhizocephala share a distinctive type of filiform spermatozoon (Fig. 1c-g), the chief characteristics of which are: (1) a simple, conical acrosome capping the axoneme; (2) a filiform nucleus running parallel to the axoneme; (3) a single, rod shaped mitochondrion posterior to the nucleus; (4) substantial glycogen deposits associated with the axoneme in the posterior half of the spermatozoon.…”

“…Among the Crustacea, only the maxillopod groups Thecostraca (sensu Grygier, 1987a;Newman, 1987), Branchiura and Mystacocarida retain an axoneme in their spermatozoa (Brown & Metz, 1967;Brown, 1970;Munn & Barnes, 1970a, 1970bWingstrand, 1972Wingstrand, , 1978Wingstrand, , 1988Pochon-Masson, 1978;Kubo et al, 1979;Grygier, 1981Grygier, , 1982Grygier, , 1987a. In other crustaceans, sperm motility is either wanting, (e.g.…”

“…lc-g), the basic features of which include a conical acrosome at the apex of the axoneme, a filamentous nucleus parallel to the axoneme, a single elongate mitochondrion and glycogen deposit parallel to the axoneme (Munn & Barnes, 1970a, 1970bPochon-Masson, 1971). The spermatozoa of thoracicans, acrothoracicans and possibly rhizocephalans also possess an accessory droplet, a basically fusiform body produced by the Golgi complex during the later stages of spermiogenesis (Kubo et aI., 1979;Azevedo & Corral, 1982), but then lost in the seminal vesicles, in the anterior portion of the ejaculatory duct, or soon after leaving the penis (Munn & Barnes, 1970b;Barnes et al, 1971;Barnes et al, 1977;Kubo et al, 1979). The accessory droplet is unique to this sperm type and adds further weight to the concept that the filiform sperm of Thoracica, Acrothoracica and Rhizocephala is a synapomorphy, placing the Rhizocephala close to, if not within, the Cirripedia.…”

“…A review of spermatozoa and spermiogenesis in the Rhizocephala is currently being prepared by Hoeg & Jespersen (J. Hoeg, personal communication). The accessory droplet of balanomorph spermatozoa is known to vary in internal structure from species to species (for example Munn & Barnes, 1970b;Kubo et al, 1979), but no attempt has been made to relate this structure to phylogeny. In the present work, we offer comparative data on sperm ultrastructure in a wide range of species, with particular emphasis on specific variation in the ultrastructure of the accessory droplet.…”