Testis structure and sperm packet formation in the phylogenetically basal teleost Pantodon buchholzi

Spermatogenesis in the inseminating African butterflyfish Pantodon buchholzi (Teleostei: Osteoglossiformes: Pantodontidae) with the revision of residual bodies formation

“…A unique aspect of spermiogenesis reported by van Deurs (1975) is the formation of peculiar RBs containing spindle-shaped bodies (SSBs), mitochondria, cisternae of endoplasmic reticulum (ER), granules of glycogen and a "peculiar structure" composed of two rows of vesicles associated with cross-bridges. Dymek and Pecio (2019) confirmed phagocytosis of the RBs by Sertoli cells, which was predicted by van Deurs (1975). Dymek and Pecio (2019) also presented data on testis structure as well as the formation of sperm packets within the cysts at the end of spermiogenesis, which strengthens the evidence for insemination.…”

“…Dymek and Pecio (2019) confirmed phagocytosis of the RBs by Sertoli cells, which was predicted by van Deurs (1975). Dymek and Pecio (2019) also presented data on testis structure as well as the formation of sperm packets within the cysts at the end of spermiogenesis, which strengthens the evidence for insemination.…”

“…Among 272 extant osteoglossomorph species, sperm ultrastructure was investigated in 9 representatives of the families: Pantodontidae, Osteoglossidae, Notopteridae, Mormyridae and Gymnarchidae. The sole representative of the Pantodontidae, Pantodon buchholzi (Peters 1876), exhibits complex introsperm ultrastructure and sperm packet formation (Dymek & Pecio, 2019; van Deurs, 1975; van Deurs & Lastein, 1973), whereas all other osteoglossomorphs studied produce aquasperm. Uniflagellate aquasperm were reported only in the notopterid Papyrocranus afer (Günther 1868) (Mattei, 1970), and biflagellate aquasperm were described recently in the osteoglossid Heterotis niloticus (Cuvier 1829) (Mattei et al ., 2019).…”

Ovary structure and oogenesis in internally and externally fertilizing Osteoglossiformes (Teleostei:Osteoglossomorpha)

“…Tissues obtained from P. buchholzi and O. bicirrhosum were fixed in the Bouin's solution for 72 hr, whereas those from M. cyprinoides, B. niger, G. petersii and M. rume were kept in 75% ethanol also for 72 hr. Subsequently, all samples were dehydrated in a graded series of ethanol, cleared with xylene and embedded in paraffin (Paraplast® Regular, Sigma-Aldrich®) as previously described (Dymek & Pecio, 2019). Samples were then serially sectioned (4 µm) and stained with haematoxylin and eosin to visualize the organ structure, while Mallory's trichrome stain was used for the differentiation of connective tissue, and combined alcian blue/periodic acid-Schiff (AB-PAS) at a pH of 2.5 was applied to visualize cytoplasmic structures in oocytes for the detection of neutral or acidic polysaccharides.…”

Diversity of Balbiani body formation in internally and externally fertilizing representatives of Osteoglossiformes (Teleostei: Osteoglossomorpha)

“…Pantodon buchholzi (Pantodontidae), the only extant osteoglossomorph with insemination, produces complex introsperm packed into naked bundles (spermatozeugmata), whereas all other species classified into this group produce sperm releasing into water, called aquasperm, which is categorized as uniflagellate, biflagellate, and aflagellate (Mattei, 1970, 1991; Mattei et al, 1967; Mattei et al, 1972; Mattei et al, 2019; van Deurs, 1973; van Deurs & Lastein, 1973). This suggests that P. buchholzi may be the most basal teleost species in which insemination has evolved (Dymek & Pecio, 2019). The process of spermatogenesis in this species leads to the formation of one of the most complex introsperm among fish.…”