Spermatogenesis and related plasma androgen and progestin level in wild male golden mahseer, Tor putitora (Hamilton, 1822), during the spawning season

Abstract

Testicular development and plasma levels of sex steroid [11-ketotestosterone (11-KT), testosterone (T) and 17,20β-dihydoxy-4-pregnen-3-one (17,20β-P)] were studied for the first time in wild golden mahseer, Tor putitora. Testicular development was investigated by macroscopic observation and histology of the gonads, whereas steroids were measured by enzyme-linked immunosorbent assay. Based on macroscopic observation and germ cell types present in gonad histology, the testes of T. putitora were divided into five developmental stages: immature [stage I; spermatogonia (SPG)], early spermatogenesis [stage II; SPG and spermatocytes (SPC)], late spermatogenesis [stage III; SPG, SPC, spermatids (SPD) and spermatozoa (SPZ)], spermiation (stage IV; SPZ) and post-spawning (stage V; SPG, SPD and SPZ). During the stage I of the testes, the lowest levels of plasma sex steroid and gonadosomatic index (I G) were recorded. The highest plasma level of T was 0.89 ± 0.09 ng/mL and 11-KT was 4.23 ± 0.54 ng/mL, which was during the stage III and IV, respectively. The peak in 11-KT was coincident with the peak in I G (1.65 ± 0.12 %). The lowest T and 11-KT levels were 0.25 ± 0.02 ng/mL and 0.47 ± 0.09 ng/mL, respectively, which was at stage I. Plasma levels of 17,20β-P increased significantly at stage III (1.04 ± 0.06 ng/mL) and stage IV testes (1.28 ± 0.03 ng/mL) and then declined in post-spawned fish. This indicates that 17,20β-P could also be a possible maturation-inducing steroid in this fish. The condition factor (K) significantly decreased during the testicular development and was lowest at spermiation stage (0.53 ± 0.02 %). The proportion of running male peaked concomitantly with the appearance of stage IV testes. Presence of germ cells of different developmental stages indicates that T. putitora male is a multiple spawner, and the information generated here is important for developing a captive breeding, culture and conservation programs for this endangered coldwater Himalayan fish species.

Intra‐annual changes in reproductive indices of male and female Himalayan snow trout,Schizothorax richardsonii(Gray, 1832)

“…Subsequently in June, testicular histology showed tubule with cysts of spermatogenic germ cells in the periphery, indicating re‐initiation and progression of spermatogenic activity (spermatogonial proliferation) as previously reported in S. richardsonii (Bisht, 1974). These cyclic changes in GSI values concordant with the spermatogenic process that we observed is in agreement with previous studies in male teleosts (Adebiyi et al., 2013; Chakrabarti & Banerjee, 2015; Koya, Soyano, Yamamoto, Obana, & Matsubara, 2002; Shahi, Mallik, Pande, Das, & Singh, 2015). Period‐wise, gonadal cycle starts with minimal spermatogenic activity indicated by few emerging cysts of spermatogenic germ cells and with lesser luminal spermatozoa in June representing initiation of spermatogenesis (regenerating stage); thereafter, the appearance of comparatively different sizes of testicular tubules filled with spermatozoa during September to February indicates presence of spawning‐ready mature individuals and finally decreased relative size and occurrence of luminal residual spermatozoa in the month of April representing regressing stage.…”

“…This finding nearly concurs with our testicular histology and GSI observations. Similarly, earlier studies documented progressive increase in 11‐KT and GSI during testicular development and reached peak during spermiation in several teleost (Roberts et al., 1999; Shahi et al., 2015).…”

“…This finding nearly concurs with our testicular histology and GSI observations. Similarly, earlier studies documented progressive increase in 11-KT and GSI during testicular development and reached peak during spermiation in several teleost (Roberts et al, 1999;Shahi et al, 2015). spermiation, milt production and sperm motility (Amer, Miura, Miura, & Yamauchi, 2001;Nagahama, 1994;Scott et al, 2010;Tubbs & Thomas, 2008;Yueh & Chang, 1997).…”

“…We visibly confirmed this, as almost all the male fish examined during September to February had matured testes with oozing milt. Elevated 17α, 20β DHP during spermiation has been reported in males of several teleost including other hill stream cyprinids, Barilius bendelisis and Tor putitora (Canario, 1991; Shahi et al., 2015; Sharma et al, 2018).…”

Estudio del control ambiental, hormonal y molecular de la pubertad anticipada de la lubina aplicando ventanas de corta duración de luz continua.

“…Por el contrario, durante la recrudescencia tardía y/o la espermiación, las progestinas y los estrógenos parecen ejercer un papel clave. En el caso de las progestinas se considera que éstas son necesarias para el reclutamiento de espermatogonias, la meiosis (Miura et al, 2006;Chen et al, 2013;Liu et al, 2014) y la estimulación del proceso de espermiación (Scott et al, 2010;Bryan et al, 2015;Shahi et al, 2015). Por ejemplo, se ha demostrado que existe una correlación entre los niveles de Lh circulantes con un incremento de DHP, coincidiendo con la aparición de células germinales post-meióticas y del receptor de la Lh en los testículos (Prat et al, 1996;Gómez et al, 1999;Campbell et al, 2003).…”