Main Article Content

Dulce Marie Pili Nisperos
Gliceria B. Ramos


The establishment and survival of the population of species in their breeding ground can be attributed to the species’ reproductive characteristic and capacity. The Monopterus albus species is an introduced fish in the Philippines. It is a protogynous hermaphrodite which has a natural ability for sex reversal. This study describes the histomorphology of the different stages of gonadal maturation and determines the concentration levels of the steroid hormones 17ß-estradiol (E2) and testosterone (T) in the blood plasma. These aim to a further understanding on the gonadal development and sex differentiation of the rice paddy eel as a hermaphroditic fish. Fish samples were collected randomly from farm ponds located in three provinces within the island of Luzon, Philippines. The sexual identity of the fish was categorized based on the presence or absence of ovarian and testicular tissues. Histological analysis of the gonad showed that immature, maturing-matured female gonad exhibited ovarian tissues of varying stages. The intersex gonad showed the existence of both ovarian and testicular tissues. Enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration levels of gonadal steroid hormones. Differences in the concentration levels of the two hormones were evident across all the stages of gonad maturation. The functional role of these hormones in vitellogenesis and spermatogenesis leads to the development of this sex-changing gonads. This reproductive characteristic contributes to our understanding of the reproductive success of hermaphroditic fish.


Download data is not yet available.

Article Details

Original Articles


Aires, B. (2002). Oogenesis in the swamp eel Synbranchus marmoratus (Bloch , 1795 ) ( Teleostei ; synbranchidae ). Ovarian anatomy, stages of oocyte development and micropyle structure, 26(3), 325–337.

Alam, M. A., Komuro, H., Bhandari, R. K., Nakamura, S., Soyano, K., & Nakamura, M. (2005). Immunohistochemical evidence identifying the site of androgen production in the ovary of the protogynous grouper Epinephelus merra. Cell and Tissue Research, 320(2), 323–329. https://doi.org/10.1007/s00441-004-1037-9

Alvarado, M., Serrano, E., Sanchez, J & Valladares, L. (2015). Changes in plasma steroid hormones and gonadal histology associated with sexual maturation in wild southern hake (Merluccius australis). (2015), 43(4), 632–640. http://doi.org/10.3856/vol43-issue4-fulltext-2

Angelis, D., Adamski, J., Tokarz, J., Möller, G., & Hrabe, M. (2015). Steroids in teleost fishes: A functional point of view, (June). http://doi.org/10.1016/j.steroids.2015.06.011

Cardwell JR & Liley NR (1991) Hormonal control of sex and color change in the stoplight parrotfish, Sparisoma viride. Gen Comp Endocrinol 81:7–20

Chan, S.T.H. and Phillips, J.G. (1967). The structure of the gonad during natural sex reversal in Monopterus albus (Pisces: Teleostei), J. Zool 151:129–141.

Chan, S.T.H (1967). Seasonal changes in the distribution of gonadal lipids and spermatogenetic tissue in the male phase, 31–41.
Chan, S. T. H., Phillips, J. G., & Gottfried, G. (1969). The Biosynthesis of Steroids by the Gonads of the Ricefield Eel Monopterus Phases during Natural a / bus at Various Sex Reversal, (1964).
Chan, S. T. H., O, W. ‐S, Tang, F., & Lofts, B. (1972). Biopsy studies on the natural sex reversal in Monopterus albus (Pisces: Teleostei). Journal of Zoology, 167(4), 415–421. https://doi.org/10.1111/j.1469-7998.1972.tb01733.x
Cheng, H., Guo, Y., Yu, Q., & Zhou, R. (2003). The rice field eel as a model system for vertebrate sexual development, 277, 274–277. http://doi.org/10.1159/000074348
Devlin, R.H. and Nagahama, Y. (2002). Sex determination and sex differentiation in fish: an overview of genetic, physiological and environmental influences. Aquaculture 208 191-364.
Gailard, S., Grillasca, J-P., Leung-Tack, D., Aubert, J. (2004). A Brief Story of Fish Sex. J. Fish. Soc.Taiwan. 31(1): 1-11.
Guerrero III, R. (2014). Impacts of Introduced Freshwater Fishes in the Philippines (1905-2013): A Review and Recommendations. Philippine Journal of Science, 143(1): 49-59.
Kotellat, M. et. al., (1993). Freshwater Fishes of Western Indonesia and Sulawesi. 15.
Koya, Y., H. Watanabe, K. Soyano, K. Ohta, M. Aritaki & T. Matsubara. (2003). Testicular development and serum steroid hormone levels in captive male spotted halibut Verasper variegatus. Fish. Sci., 69: 792-798.

Liem, K.F. (1963). Sex reversal as a natural process in the synbranchiform fish Monopterus albus. Copeia 1963(2):303 312.
Lokman PM, Harris B, Kusakabe M, Kime DE, Schulz RW, Adachi S,Young G (2002)11-Oxygenated androgens in female teleosts: prevalence, abundance, and life history implications. Gen Comp Endocrinol 129:1–12
Matsumoto, S., Takeyama, T., Ohnishi, N., Kohda, M., Matsumoto, S., Takeyama, T., Kohda, M. (2011). Mating System and Size Advantage of Male Mating in the Protogynous Swamp Eel Monopterus albus with Paternal Care, 28(5), 360–367. http://doi.org/10.2108/zsj.28.360
Mazzoni, R., Fenerich-Verani, N., & Caramaschi, E. P. (2000). Electrofishing as a sampling technique for coastal stream fish populations and communities in the Southeast of Brazil. Revista Brasileira de Biologia, 60(2), 205–216. https://doi.org/10.1590/s0034-71082000000200003
Murua, H., Kraus, G., Saborido-Rey, F., Witthames, P.R., Thorsen, A. Junquera, S. (2003). Procedures to Estimate Fecundity of Marine Fish Species in Relation to their Reproductive Strategy. J. Northw. Atl. Fish. Sci. Vol.33: 33-54.
Nagahama, Y. (1994). Endocrine regulation of gametogenesis in fish, 229, 217–229.

Rainboth F. O. R. (1996). Identification, S., Guide, F., & Fishery. Department of Biology and Microbiology University of Wisconsin Oshkosh Oshkosh, Wisconsin, U.S.A.

Ravaglia, M, Maggese, MC. (2002). Oogenesis in the swamp eel Synbranchus marmoratus (Bloch, 1795) (Teleostei; synbranchidae ). Ovarian anatomy, stages of oocyte development and micropyle structure. 26(3), 325–337.

Rinchard, J., P. Kestemont, E.R. Kühn & A. Fostier. (1993). Seasonal changes in plasma levels of steroid hormones in an asynchronous fish the gudgeon Gobio gobio L. (Teleostei, Cyprinidae). Gen. Comp. Endocrinol., 92: 168-178.
Rosen, D. E., and P. H. Greenwood (1976). A fourth neotropical species of Synbranchid eel and the phylogeny and systematics of Synbranchiform fishes. Bull. Am. Mus. Nat. Hist., 157: 1–69

Wallace, Robin A. and Selman, Kelly (1981). Oocyte Growth in Teleosts 1. 343, 325–343.

Yamamoto, T., 1969. Sex differentiation. In: Fish Physiology, vol. 3A. Hoar, W.S., Randall, D.J. (Eds.), Academic Press, New York, pp. 117–175.
Zhou et.al Hou, R. Z., & Heng, H. C. (2002). SRY -related genes in the genome of the rice field eel (Monopterus albus), 34, 129–137. http://doi.org/10.1051/gse