Vol. 59, 2020
(update: 2020.05.12; 06.17)
Chronology of Gonadal
Development in the Malayan Snail-eating Turtle Malayemys macrocephala
Pewphong1, Jirarach Kitana1,2, and Noppadon Kitana1,2,*
of Biology, Faculty of Science, Chulalongkorn University, Bangkok
*Correspondence: E-mail: firstname.lastname@example.org (NK)
E-mail: email@example.com (Pewphong); firstname.lastname@example.org (JK)
2BioSentinel Research Group (Special Task Force for
Activating Research), Department of Biology, Faculty of Science,
Chulalongkorn University, Bangkok 10330, Thailand
(Received 6 July 2019 / Accepted 8 May
Communicated by Benny K.K. Chan
snail-eating turtle, Malayemys
is a common freshwater turtle that can be used as an animal model for
developmental biology. However, a thorough investigation of its
development is needed before this species can be used as a model. Thus,
this study aimed to examine the gonadal development of M. macrocephala.
Turtle eggs were collected from rice fields in Phra Nakhon Si Ayutthaya
Province, Thailand, and transported to the laboratory. Eggs were
incubated in microprocessor-controlled incubators and randomly
dissected on a weekly basis to reveal the developing embryos, then
their developmental stage was identified according to Yntema (1968).
Primordial germ cells and gonad structure were processed through the
paraffin method. Moreover, the dynamics of germ cell proliferation and
apoptosis were examined by immunohistochemical detection of
proliferating cell nuclear antigen (PCNA) and the terminal
deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL),
respectively. Examination of the gonad revealed four main stages of
gonadal development: (i) germ cell migration, (ii) genital ridge
appearance, (iii) testicular formation, and (iv) ovarian formation. In
the male turtle (incubated at 26°C), gonad developed into the testis
with medullary sex cords starting at Yntema stage 17. In the female
turtle (incubated at 32°C), these sex cords then degenerated, followed
by cortical development into an ovarian structure starting at Yntema
stage 19. Subsequently, testicular and ovarian development occurred
independently, and distinct sex organs were apparent at Yntema stage
25. In addition, the presumptive testis showed germ cell proliferation
in the medulla at Yntema stages 17, 19, and 25 and germ cell apoptosis
in the cortex at Yntema stages 19 and 25. The presumptive ovary showed
germ cell proliferation in the cortex at Yntema stages 19 and 25, and
germ cell apoptosis in the medulla at Yntema stages 19 and 25.
Key words: Apoptosis, Embryos,
Freshwater turtle, Microscopic examination, Proliferation.
Citation: Pewphong R, Kitana J, Kitana N.
2020. Chronology of gonadal development in the Malayan snail-eating
turtle Malayemys macrocephala.
Zool Stud 59:20.