Reproductive Morphology of the Golden Tree Snake Chrysopelea ornata (Serpentes: Colubridae) from Ao Nang, Krabi Province, Thailand

Sains Malaysiana 51(5)(2022): 1293-1303 http://doi.org/10.17576/jsm-2022-5105-02

ABSTRACT We monitored the reproductive morphology of the female and male Golden tree snake, Chrysopelea ornata. The females and males were collected during a year from Ao Nang, Muang Krabi, Krabi province, a southern part of Thailand. We investigated the female and male reproductive systems via anatomical and histological approaches. The results demonstrated that the reproductive tracts of females and males were located above the kidney and its right tract was more anteriorly than the left tract. Ovarian follicles were classified into the previtellogenic, early vitellogenic, and late vitellogenic follicles. Previtellogenic follicles were contained three types of cells in the multi-layered granulosa layer: small, intermediate, and large pyriform cells. This such layer becomes the single layer in which the pyriform cells were disappeared in the vitellogenic follicles. Various stages including corpora lutea, gestation, oviposition, and birth were all observed in this study. The oviductal structure of the Golden tree snake was divided into four regions: anterior and posterior infundibulum, uterus, and vagina. The anterior oviductal wall was covered by ciliated and non-ciliated cuboidal epithelial cells and a thin muscularis layer while its posterior portion was contained by ciliated and non-ciliated cuboidal and columnar epithelial cell, and a thick muscularis layer. We found the tubular ciliated glands in the posterior infundibulum. Additionally, the hypertrophied uterine glands in the uterus were observed during the vitellogenic stage. The seminiferous tubules were active simultaneously with the hypertrophied sexual segment of the kidney.

INTRODUCTION The Golden tree snake (Chrysopelea ornata Shaw 1802) is common in all regions of Thailand and often found in house buildings. The Genus Chrysopelea distributes over almost tropical part of southeast Asia (Bulian 1997) and contains 5 species (Socha 2011), including C. ornata Shaw 1802; C. paradisi Boie 1827; C. pelias Linnaeus 1758; C. rhodopleuron Fischer 1880; C. aprobanica Smith 1943, of which the first three species are restricted to Thailand. A few natural historical studies were available to such this species, especially information on the reproductive biology of this species was little available as far as it was concerned. For example, it belongs to oviparous and polyandrous species with its copulation period being from January to April in Surat Thani province, a southern part of Thailand (Bulian 1997).

We were interested in the female and male reproductive systems of the Golden tree snake. Typically, the reproductive system of female snakes contains a paired ovary and oviduct connecting to a cloacal opening. The terminology of several oviductal portions was a controversial issue among reptilian groups (Rojas et al. 2015). Blackburn (1998) demonstrated that the oviduct was anatomically divided into three different parts, namely infundibulum, uterus, and vagina in an oviparous Horned lizard, Phrynosoma cornutum. However, with a histological approach, the oviduct can be divided into several different portions, including the infundibulum, the uterine tube (glandular region), the isthmus (aglandular segment), the uterus (shell-forming region), and the vagina (cervix) in the gekkonid species, Hoplodactylus maculatus (Girling 2002). Anatomically, the oviductal regions of the Common garter snake, Thamnophis sirtalis (Blackburn 1998), and the Crowned snake, Tantilla coronata (Aldridge 1992) can also be divided roughly into three distinct regions: infundibulum, uterus, and vagina as a Horned lizard, Phrynosoma cornutum. However, based on the histological approach, the oviductal regions of the Crowned snake can be allocated into several different segments: namely infundibulum, seminal receptacle at the infundibulum-uterus junction, anterior and posterior uterus, and vagina (Aldridge 1992). The several distinguishable regions mentioned above are not recognized in all reptilian species and additional regions may also be included (Aldridge 1992). Rojas et al. (2015) additionally demonstrated that in the Patagonia green racer, Philodryas patagoniensis, there are two portions of infundibulum, anterior and posterior infundibulum. The latter one functions as a sperm storagesite in both pregnant and non-pregnant snakes of this species. This species also stores sperm at utero-vaginal junction (UVJ) (Rojas et al. 2015). In Military ground snake, Erythrolamprus miliaris, its uterine part is also contained both glandular and non-glandular regions (Rojas et al. 2017). Grossly, the male reproductive system of typical snakes is comprised of two elongated oval testes, ductus deferens, and hemipenis (Tumkiratiwong et al. 2012). Histologically, the seminiferous tubules pass spermatozoa sequentially through rete testis, ductuli efferentes, ductus epididymis, and ductus deferens (Trauth & Sever 2011). In male squamates, the sexual segment of the kidney (SSK) is another unique characteristic of their reproductive system. SSK is a male accessory sexual gland that passes secretions into the ureter (Trauth & Sever 2011). SSK has a secretory function, and its secretions are mixed with the semen to be transmitted into the female tract during copulation (Aldridge et al. 2011). It undergoes hypertrophy and secretes materials that help maintain sperm stored in the vas deferens prior to ejaculation (Aldridge et al. 2011). It is the largest at the time of spermatogenesis in the Common garter snake, Thamnophis sirtalis (Bishop 1959). In some species, it may contribute secretions to the formation of the copulatory plug produced to block the female cloaca after copulation and prevent the entry of sperm from another male (Norris & Carr 2013). In this study, we monitored the anatomical and histological reproductive morphologies of the female and male Golden tree snake Chrysopelea ornata from Ao Nang, Krabi Province, Thailand.

Sains Malaysiana 51(5)(2022): 1293-1303 http://doi.org/10.17576/jsm-2022-5105-02