Reproductive Biology and Population Structure of Eurycea chamberlaini in North Carolina
Eurycea chamberlaini (Chamberlain's Dwarf Salamander) is a small spelerpine salamander with scant reproductive and life-history data available. Therefore, the objectives of our study were to examine the reproductive life history and population structure of E. chamberlaini from a North Carolina population. From February 2008 to February 2009, monthly collections were made in Craven County, North Carolina. All specimens (n = 392) were histologically examined for reproductive life history and population characteristics by month. Overall, male and female E. chamberlaini follow a reproductive cycle similar to other spelerpine species with sperm in the Wolffian ducts of specimens from September to February; however, spermatidogenesis was delayed until August and September with the presence of mature sperm in testes from August through November. We captured 201 female salamanders of which 36 were considered immature. We caught 191 males of which 27 were considered immature. The mean snout–vent length (SVL±1 SD) of mature females (27.13±2.33 mm) and males (25.84±2.03 mm) was statistically different from one another. Females tended to be larger than males from our monthly samples, with a greater proportion of the largest specimens being female. Overall, population structure of E. chamblerlaini appears similar to other coastal plain salamander species.
Overview of the male and female reproductive cycle of Eurycea chamberlaini. Gray bars indicate that only some of the specimens sampled during those months possessed the labeled condition. Please see the results section for specifics.
Histological micrographs depicting germ cell development and sperm transport within male testes throughout the year (hematoxylin and eosin). (A) April; (B) March; (C–F) August; (G) November; (H) January; M1c, cyst containing primary spermatocytes undergoing meiosis I; M2c, cyst containing secondary spermatocytes undergoing meiosis II; Mpt, mid-principal piece of sperm tails; Msc, cyst containing primarily mature sperm; Ppt, principal piece of sperm tails; Sc, Sertoli cell; Sc1c, cyst containing primary spermatocytes; Scn, Sertoli cell nuclei; Sg1l, lobule containing primary spermatogonia; Sg2l, lobule containing secondary spermatogonia; Sn, sperm nuclei; Soc, cyst containing spermatids in early spermiogenesis; Sp, sperm; Stl, post-spermiating lobule; Wen, nuclei of Wolffian duct epithelium. Scale bar = 50 μm.
Histological micrographs depicting the progressive size increase of male mental exocrine gland tubules (tissue within dashed aqua ovals) throughout the year (hematoxylin and eosin). (A) April; (B) July; (C) September; (D) December; Scale bar = 200 μm.
Histological micrographs depicting complex spermathecae of females throughout the year. (A,a) September; (B,b) January; (C,c) March; Clo, cloacal orifice; Nep, nuclei of spermathecal tubule epithelium; Sp, sperm; Spt, spermathecal tubules; Vt, vent. Scale bars = 200 μm (A–C) and 20 μm (a–c).
Number of male and female Eurycea chamberlaini collected from different size classes. Note that a higher proportion of females attain greater lengths in comparison to males.
Total number of Eurycea chamberlaini captured from each month. Solid circle indicates a potential cohort of recently metamorphosed salamanders from the same year as oviposition; i.e., the smallest immature individuals were captured around the timing of previous reports of metamorphosis (Semlitsch, 1980) and increased in size until winter. Larger immature metamorphs (dashed circle) from January and May through July most likely represent individuals that metamorphosed the previous year and that are close enough in size to mature individuals that they probably would have been ready for reproduction in the coming fall.
Contributor Notes
Associate Editor: W. L. Smith.