Morphology and histology of male and female reproductive systems in the inseminating species Scoloplax distolothrix (Ostariophysi: Siluriformes: Scoloplacidae)

Abstract

The morphology and histology of male and female reproductive systems were examined in Scoloplax distolothrix. Internal insemination was documented in this species by the presence of sperm within the ovaries. Mature males and females have elongated genital papillae, exhibiting a tubular shape in males and a plain heart-shape with two median protuberances in females. The testes are two elongated structures that converge ventrally, under the intestine, towards the genital papilla. They are joined at the caudal end, forming an ovoid single chamber for sperm storage. Secretory regions were not observed. In the lumen of the testicular tubules, spermatozoa can be tightly packed along their lengths, but do not constitute a spermatozeugmata. The lumen of the sperm storage chamber and spermatic duct are filled with free spermatozoa without the accompanying secretions. The ovaries are bird-wing shaped, saccular structures that converge ventrally under the intestine, towards the genital papilla. They are joined at the caudal end, forming a tubular chamber possibly destined for oocyte storage. An oviduct with an irregular outline connects the chamber to the tubular region of the genital papilla. No distinct sperm storage structure was found in the ovaries. The unique male and female genital papillae suggest that these structures are associated with the reproductive mode in scoloplacids, representing evidence for insemination. The occurrence of free spermatozoa, without the accompanying secretions and not arranged in a spermatozeugmata can be associated with the presence of a tubular male genital papilla for sperm transfer to the female genital tract. This reinforces the idea that sperm packets are not necessary for all inseminating species. The male reproductive system in scoloplacids is very different from that in auchenipterids, a second catfish family with insemination, which indicates that the occurrence of insemination is not connected to the internal morphology of reproductive organs.

Reproductive cycle of the Neotropical cichlid yellow peacock bass Cichla kelberi: A novel pattern of testicular development

“…The morphological characterization of C. kelberi testes as lobular type, phylogenetically corroborates with Parenti & Grier (2004) results, who propose this testicular type as a synapomorphic character present in all surviving Neoteleost, just like the results obtained for other species of the orders Perciformes, Scorpaeniformes and Synbranchiformes, which represent more derived taxa when compared to Characiformes, Cypriniformes, and Siluriformes, whose testes were classified as anastomosing tubular (Selman & Wallace, 1986 Muñoz et al, 2002;Lo Nostro et al, 2003b;Arias et al, 2004, Dadzie & Abou-Seedo, 2004Parenti & Grier, 2004;Thacker & Grier, 2005;Nobrega & Quágio-Grassiotto, 2007;Spadella et al, 2008;Matta et al, 2009;Leal et al, 2009;Martins et al, 2010;Muñoz et al, 2010).…”

Comparative morphology of the gonadal structure related to reproductive strategies in six species of neotropical catfishes (Teleostei: Siluriformes)

“…In this study, spermatozeugmata packages were observed stored in narrow and complex folds of the cuboidal lamellar epithelium in T. galeatus females. In Siluriformes, internal fertilization was observed only in the families Auchenipteridae and Scoloplacidae (Loir et al,1989; Meisner et al,2000; Burns et al,2002; Mazzoldi et al,2007; Spadella et al,2008; Parreira et al,2009). The spermatozeugmata stored in the epithelial cells lining ovarian lamellae of the mature and partially spawned ovaries of T. galeatus may represent an important strategy to maintain the viability of the spermatozoa for long periods.…”

“…The success that has been achieved by these catfishes in different environments is also related to their diverse reproductive strategies (Suzuki et al,2000; Sato et al,2003; Sato and Godinho,2004; Godinho et al,2009). Several previous studies have discussed the relationship of reproductive strategies and the morphological characteristics of the reproductive systems in Siluriformes (Loir et al,1989; Meisner et al,2000; Rizzo et al,2002; Mazzoldi et al,2007; Spadella et al,2008).…”

“…In others families, the caudal region of the testes contains seminal vesicles or secretory cells without spermatogenic activity that have secretory and/or storage functions (Legendre et al,1996; Meisner et al,2000; Santos et al,2001). Some species in the families Auchenipteridae and Scoloplacidae exhibit internal fertilization associated with modifications to the spermatozoon and the reproductive system (Burns et al,2002; Spadella et al,2008; Parreira et al,2009).…”

Formation of zona radiata and ultrastructural analysis of egg envelope during oogenesis of Chinese perch Siniperca chuatsi

“…The zona radiata configuration is conservative in teleost reproduction. The zona radiata of S. chuatsi is composed of Z1, Z2 and Z3, which is similar to other species in structure and formation pattern (Flegler, 1977;Zhang and Xie, 1995;Wei et al, 1995;Fang and Zheng, 2002;Francolini et al, 2003;Ravaglia and Maggese, 2003;Spadella et al, 2008). Mature oocytes in the ovary have follicular envelopes that are composed of disaggregated follicular cells, theca cells, basalmembrane and thin connective tissue.…”