Reproduction in the Western Mud Snake, Farancia abacura reinwardtii (Serpentes: Colubridae), in Arkansas

Journal of the Arkansas Academy of Science Volume 46 Article 8 1992 Reproduction in the Western Mud Snake, Farancia abacura reinwardtii (Serpentes: Colubridae), in Arkansas John W. Robinette Arkansas State University Stanley E. Trauth Arkansas State University Follow this and additional works at: http://scholarworks.uark.edu/jaas Part of the Zoology Commons Recommended Citation Robinette, John W. and Trauth, Stanley E. (1992) "Reproduction in the Western Mud Snake, Farancia abacura reinwardtii (Serpentes: Colubridae), in Arkansas," Journal of the Arkansas Academy of Science: Vol. 46 , Article 8. Available at: http://scholarworks.uark.edu/jaas/vol46/iss1/8 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact , . Journal of the Arkansas Academy of Science, Vol. 46 [1992], Art. 8 FARANCIA ABACURA REINWARDTII (SERPENTES: COLUBRIDAE), INARKANSAS JOHN W. ROBINETTE and STANLEY E. TRAUTH Department of Biological Sciences Arkansas State University State University, AR 72467-0599 ABSTRACT The reproductive cycle of Farancia abacura reinwardtii was studied using samples of snakes collected throughout Arkansas from 1985 to 1991 ;museum specimens were also examined. The right testis of 22 males was examined by light microscopy. Histological analysis of the testis indicated a postnuptial spermatogenic cycle. Testicular recrudescence begins in late May with sperm production peaking in late summer; sperm overwinter in the ductus deferens. Ovarian follicles of 22 females were measured and counted; two follicular sizes were noted. In those undergoing primary vitellogenesis, a maximum size of 6.5 mm was reached; those exhibiting secondary viteilogenesis ranged in size from 12 to 21 mm. Average clutch size in females with follicles over 10 mm was 14.6 (n=6). Oviductal eggs were observed in a single female in early September. Female F. abacura require at least 2.5 years to become sexually mature. Follicular growth is slow over the first two years but increases dramatically during the spring of the third year. INTRODUCTION The western mud snake, Farancia abacura reinwardtii, is a largebodied, aquatic colubrid that ranges throughout much of the southeastern and southcentral United States (Conant and Collins, 1991). The mud snake inhabits shallow, soft-bottomed waterways with slow current, favoring Cyprus swamps, sloughs, bogs, creeks, and marshes. Amphiumas and sirens are the preferred food of adults, although freshwater eels, frogs, tadpoles, aquatic salamanders, and fish are preyed upon (Ernst and Barbour, 1989). The reproductive biology ofF. a. reinwardtii has received very little attention (McDaniel and Karges, 1982; Mitchell, 1982); most accounts deal with morphological features, feeding habits, distribution, and habitat. The breeding season of this oviparous snake is not well understood with few and varying documented accounts of mating. Fitch (1985) stated that F. abacura is one of the most prolific North American snakes; however, clutch size records are few and not well distributed to show geographic variation. The Arkansas populations ofF. a. reinwardtii occupy the northwesternmost extent of the range of the species; thus, data on the reproductive biology in Arkansas can contribute to a better evaluation of the variation in this wide-ranging species. The present study was undertaken to document the reproductive biology of the species in Arkansas. We specifically investigated the timing of the testicular cycle as well as the type of ovarian cycle in females. MATERIALSANDMETHODS Mud snakes were collected throughout Arkansas from 1985 to 1991 additional individuals coming from preserved museum specimens (n =with 44). Snakes were collected alive or dead on the road. Live snakes were given a lethal injection of sodium pentobarbital and fixed in 10% formalin. All snakes were sexed, and the SVL and tail length were recorded. Snakes were preserved in 70% ethanol and deposited in the Arkansas State University Museum of Zoology. The right testis and attached epididymis of 22 males were removed and prepared for light microscopy. Tissues were dehydrated in a graded series of ethanol and cleared in xylene. The testes were then embedded in paraffin, sectioned serially at 8 Jim, and stained with Harris* hematoxylin and eosin. Each testis was examined by light microscopy noting testicular stage and presence ofsperm in the ductus deferens. Seminiferous tubule diameters were measured using an ocular micrometer. The reproductive tracts of 22 females were examined macroscopically. The diameters of ova were measured to the nearest 0.1 mm with vernier calipers, and the number of variously-sized follicles was counted. Standard statistical data were obtained from all measurements; means are accompanied by ± 2 standard errors. RESULTS MALETESTICULAR CYCLE The left testis of the mud snake lies about one-third of the body length anterior to the vent. The testis is composed of a coiled mass of seminiferous tubules held together by a thin fibrous tunica albuginea. The intertubular spaces contain many interstitial cells, blood vessels, and some connective tissue cells. The seminiferous tubules contain numerous Sertoli (nurse) cells in variable amounts within a syncytium of germinal cells; germinal cell types fluctuate seasonally during the annual lesticular cycle (Fox, 1952). The ducti deferentia, which consist of tall-to-flat epithelial cells, function in overwinter storage of spermatozoa. Spermatozoa in the ductus deferens were present in large quantities upon emergence from hibernation in the early spring, whereas the testes were completely regressed. Seminiferous tubules exhibited mainly Sertoli cells and spermatogonia in April. Lumina of seminiferous tubules were occluded by the spermatogonia/Seitoli cell syncytium and large amounts of lipiddroplets (Fig. 1). The ductus deferens were completely packed with sperm at this time (Fig. 1 ). This condition remained throughout April. Spermatogenesis began in May (Fig 2). The seminiferous tubules exhibited primary spermatocytes as the dominant cell type. By mid-May one individual had a few secondary spermatocyles, and another individual had started producing secondary spermatocytes by the end of May. While the ductus deferens remained packed with sperm, the amount of lipid material within the tubules gradually disappears. In June secondary spermatocytes were the dominant cell type within the lumina of the seminiferous tubu (...truncated)