The ultrastructure of spermiogenesis and spermatozoa in Diplomystes mesembrinus

Abstract

Spermiogenesis inDiplomystes mesembrinus, one of the most primitive species from the Siluriformes, occurs in cysts. Differentiation of spermatids is characterized by chromatin compaction, flagellum development, nuclear fossa formation, rotation of the nucleus, and excess cytoplasm elimination. The spermatozoon head is round, the nucleus contains highly condensed chromatin clusters, the midpiece is short, the axoneme shows a 9+2 pattern with two discrete lateral projections, and the acrosome is absent. The nuclear fossa penetrates deeply into the nucleus, including the centriolar complex and the start of the axoneme. The single large C-shaped mitochondrion surrounds the initial segment of the axoneme. The structural features of D. mesembrinus spermatozoon are similar to the Clupeiformes. 2001 The Fisheries Society of the British Isles

Spermatic cell characteristics in Gymnotiformes (Teleostei: Ostariophysi) and their phylogenetic meaning

“…Some spermatic cell characteristic shared by the group formed by Sternopygidae, Rhamphichthyidae and Apteronotidae (current study) are also found in the Siluriformes, O. mesembrinus (Quagio‐Grassiotto et al , 2001), in the Characiformes of the genera Salminus and Brycon (Veríssimo‐Silveira et al , 2006), and Piaractus (Burns et al , 2009), and in the Gonorynchiformes, C. chanos (Gwo et al , 1995). In all these fishes, spermiogenesis is of the type I, the nuclear rotation is complete (90°), the centriolar complex is housed the nuclear fossa, and there is a flocculent pattern of chromatin condensation.…”

Occurrence of biflagellate spermatozoa in Cetopsidae, Aspredinidae, and Nematogenyidae (Teleostei: Ostariophysi: Siluriformes)

“…Data were obtained for the following families: Amblycipitidae (Lee and Kim 1999), Auchenipteridae (Burns et al 2002), Bagridae (Emel'yanova andMakeyeva 1991a;Lee 1998;Kim and Lee 2000;Mansour and Lahnsteiner 2003), Clariidae (Mansour et al 2002), Diplomystidae (Quagio-Grassiotto et al 2001), Ictaluridae (Poirier and Nicholson 1982;Emel'yanova and Makeyeva 1991a, b), Loricariidae (Mansour and Lahnsteiner 2003), Pimelodidae (Quagio-Grassiotto and Carvalho 2000; Santos et al 2001), and Siluridae (Emel'yanova and Makeyeva 1991a; Kwon et al 1998;Lee and Kim 2001). The available information regarding the families Ariidae and Malapteruridae are restricted to some schematic drawings (Mattei 1991).…”

“…À + + À À À + À À + + À + À + À + + Pimelodidae À À + À À À À À + + À À + À À À À À À + Diplomystidae À À À + À À À + À À À + + À À À À À À À Siluridae À À + À À À À À + À À À + À + À + À + + Clariidae À À À À À À À + À À À + + À À À À À À À Loricariidae À À À À À À À + À À À + + À À À + À À + Auchenipteridae À À À À À + À À + À À À À + À + + À À + + Present, À absent, ? unavailable or contradictory information Presence of two flagella, 2 presence of lateral and parallel centrioles, 3 presence of elongated vesicles, 4 presence of lateral fins, 5 shape of the nucleus (a semi-ovoid, b conic, c ovoid with the larger axis in the horizontal position), 6 pattern of chromatin condensation (a heterogeneous, b homogeneous), 7 absence of nuclear fossa; 8 nuclear fossa as a simple arc in biflagellate spermatozoa, 9 centriole inserted in the nuclear fossa, 10 midpiece size (a short, b long), 11 cytoplasmic channel size (a short, b long), 12 number of cytoplasmic channels (a one, b two), 13 mitochondria shape (a rounded, b elongated) spermatozoa described in the literature (Quagio-Grassiotto et al 2001;Lee and Kim 1999;Mansour et al 2002;Lee and Kim 2001;Kwon et al 1998;Poirier and Nicholson 1982;Burns et al 2002;Quagio-Grassiotto and Carvalho 2000;Santos et al 2001;Lee 1998;Kim and Lee 2000), the midpiece size (character 10) was considered short when its total length was £ 1.7 lm, but considered long with the length >1.7 lm. The cytoplasmic channel size (character 11) was considered short when its total length was £ 1.5 lm, but considered long with the length >1.5 lm.…”

“…However, two previous studies with species of Bagridae described their spermatozoa as uniflagellate (Lee 1998;Kim and Lee 2000). In the species of all other siluriforms studied, such as Diplomystidae, there is only one flagellum (Quagio-Grassiotto et al 2001;Mansour and Lahnsteiner 2003) (Table 1).…”

“…Although the studies by Jamieson (1991) and Mattei (1991) present data related to spermatozoa structure of practically all major fish groups, the information about siluriform spermatozoa is still quite incomplete, since there are data lacking for several families and absence of data for several families (Quagio-Grassiotto et al 2001;Santos et al 2001). Studies of spermiogenesis and spermatozoal ultrastructure in Diplomystes mesembrinus, member of the most primitive siluriform family, have shown that many of the characteristics found in this species are not found in other groups of Siluriformes or Ostariophysi (Quagio- Grassiotto et al 2001).…”