Characterization of the gonadotropin-releasing hormone system in the Neotropical teleost, Steindachneridion parahybae during the annual reproductive cycle in captivity

Abstract

This study evaluated by immunohistochemical and Western blot methods, the distribution of two distinct gonadotropin-releasing hormones (GnRHs), corresponding to catfish GnRH (cfGnRH or GnRH1) and chicken-II GnRH (cGnRH-II or GnRH2), in Steindachneridion parahybae females in captivity, focusing these analyses on the reproductive cycle by semi-quantification of optical density (OD). Further, we found that the GnRH neuronal systems co-localized with their respective GnRH-associated peptides (GAPs). A group of neurons immunoreactive (ir) to GnRH1 were identified along the ventral region of the olfactory bulb (vOB) in the telencephalon (vTel) and in the main areas of the diencephalon (especially the medial basal hypothalamus, HBM), including fibers extending into the pituitary gland. In contrast, GnRH2 neurons were confined to the midbrain tegmentum, close to the ventricular surface, without projections to the pituitary gland. Moreover, a cfGAP (GnRH1)-specific band (9 kDa) was identified in the brain and pituitary gland, while a cGAP-II (GnRH2)-specific band (26 kDa) was observed only in the brain extract. During the reproductive cycle, GnRH1-ir presented greater OD values at the vitellogenic and regression stages than at the previtellogenic stage and after artificially induced to spawn. Larger GnRH2-ir neurons were observed during the reproductive cycle, but a higher OD was identified only in the regression stage compared with the other maturation stages. Finally, GnRH1 axons were found to be directed towards the pituitary, and this GnRH type, which is probably the hypophysiotropic form, can contribute to the reproductive dysfunction that occurs in S. parahybae females in captivity, whereas GnRH2 may act as a neuromodulator and/or neurotransmitter.

Dynamics of ovarian maturation during the annual reproductive cycle of the endangered fish Steindachneridion parahybae (Siluriformes: Pimelodidae) in captivity

“…S. parahybae presents two different gonadotropin‐releasing hormone (GnRH) forms (GnRH1 and GnRH2). GnRH1 neurons and fibres are intimately related to pituitary regulation, and GnRH2 neurons and fibres (which do not innervate the pituitary gland) are probably related to neuromodulation and/or reproductive behaviour in this species (Honji et al ., 2019). Vitellogenesis is likely to be controlled by follicle‐stimulating hormone, and during the RC in S. parahybae , the data found here (E 2 plasma profile) and this species' gonadotropin profile (Honji et al ., 2015) suggested a higher amount of this hormone during the PRV, displaying a close relationship with the seasonality of ovarian development.…”

“…The specimens were randomly divided into two ponds (200 m 2 ) to characterize the annual RC. During this period, carnivorous fish were fed at 08.00 and 16.00 hours with commercial extruded food containing 40% crude protein at a rate of 2% biomass per day, provided twice a day and under natural photoperiod, according to previous studies (Honji et al ., 2012, 2015, 2017, 2019). In addition, water quality parameters (temperature and dissolved oxygen) were monitored daily using an oximeter (Horiba – ModU10) and are presented in Table 1.…”

Gonad-stimulating potential of laserpuncture induction on the male African Sharptooth catfish (Clarias gariepinus)

“…Ministry, 2018). The catfish species are widely cultivated for the provision of animal protein-based feed (Jooste et al, 2015;Kusuma et al, 2015;Fisheries Research Institute of Indonesia, 2018). This fish species has a high growth rate and adaptable to environmental factors, such as temperature and oxygen changes.…”

“…In C. gariepinus broodstock, the hypothalamic-pituitary-gonad axis primarily manages the reproduction activity. The GnRH is a key player for reproductive activity (Chaube et al, 2015;Golan et al, 2015;Honji et al, 2019). When C. gariepinus broodstock spawn, the gonads are influenced by the hypothalamus, as it synthesizes and liberates the GnRH, stimulates the anterior pituitary to produce the gonadotropin hormone; gonadotropins stimulate steroidogenesis (Zohar et al, 2010;Borella et al, 2020).…”

Spermatogenesis and reproductive cycle of male piracanjuba ( Brycon orbignyanus ) raised for use in repopulation programmes

“…These studies are generally descriptive or comparative in nature, relating reproductive characteristics to biotic and abiotic variables, and thereby presenting an ecological perspective. In aquacultural environments, several studies have been conducted in purpose to describe the gametogenesis and also the reproductive cycle of neotropical species, either complete as in lambaris (Chehade et al, 2015;Mazzoni et al, 2015;Cassel et al 2017) and Rhamdia quelen (Ghiraldelli et al, 2008;Mazzoni et al, 2020) or partial as in the studies with Steindachneridion parahybae (Honji et al, 2019), Prochilodus lineatus (De Souza et al, 2015) and Colossoma macropomum (Pires et al, 2017). Studies on this topic with species of Bryconidae from captivity are rare and those found, both with matrinxã, Brycon cephalus (Romagosa et al, 2000) and Brycon amazonicus (Arias et al, 2006).…”