Molecular basis for regulating seasonal reproduction in vertebrates

Abstract

Animals that inhabit mid- to high-latitude regions exhibit various adaptive behaviors, such as migration, reproduction, molting and hibernation in response to seasonal cues. These adaptive behaviors are tightly regulated by seasonal changes in photoperiod, the relative day length vs night length. Recently, the regulatory pathway of seasonal reproduction has been elucidated using quail. In birds, deep brain photoreceptors receive and transmit light information to the pars tuberalis in the pituitary gland, which induces the secretion of thyroid-stimulating hormone. Thyroid-stimulating hormone locally activates thyroid hormone via induction of type 2 deiodinase in the mediobasal hypothalamus. Thyroid hormone then induces morphological changes in the terminals of neurons that express gonadotropin-releasing hormone and facilitates gonadotropin secretion from the pituitary gland. In mammals, light information is received by photoreceptors in the retina and neurally transmitted to the pineal gland, where it inhibits the synthesis and secretion of melatonin, which is crucial for seasonal reproduction. Importantly, the signaling pathway downstream of light detection and signaling is fully conserved between mammals and birds. In fish, the regulatory components of seasonal reproduction are integrated, from light detection to neuroendocrine output, in a fish-specific organ called the saccus vasculosus. Various physiological processes in humans are also influenced by seasonal environmental changes. The findings discussed herein may provide clues to addressing human diseases, such as seasonal affective disorder.

Histological development of the long‐snouted seahorse Hippocampus guttulatus during ontogeny

“…This endocrine gland is involved in teleost growth and reproduction, through liberation of hormonal stimuli and gonadotropin activation (Falk-Petersen, 2005;Patiño & Sullivan, 2002;Piccinetti et al, 2012;Piferrer & Guiguen, 2008). In addition, development of the saccus vasculosus allowed juveniles to perceive seasonal changes in day length (control of photoperiod) (Nakane et al, 2013;Nishiwaki-Ohkawa & Yoshimura, 2016) and is related to reproduction and growth, influencing the metabolic rate, body pigmentation, behavioural activity and feeding performance (Crovatto-Veras et al, 2013).…”

Regulation of Agouti-Related Protein and Pro-Opiomelanocortin Gene Expression in the Avian Arcuate Nucleus

“…Seasonal changes in reproductive physiology mediated by photoperiod in birds and seasonal mammals have been linked to release of thyroid-stimulating hormone from the pars tuberalis of the pituitary gland. This results in conversion within the medio-basal hypothalamus of thyroxine into triiodothyronine (T3) that promotes release of gonadotropin-releasing hormone from neuron terminals in the median eminence (60). It is possible that locally increased tissue concentrations of T3 mediate seasonal cycles in appetite and fat deposition in addition to reproduction.…”

The comparison of reproductive hormone receptor expressions of the sheep ovary and hormone concentrations in two Chinese breeds

“…Additional environmental factors such as photoperiod, nutrition and temperature also participate in the regulation of seasonal reproductive activity (Estrada-Cortés et al, 2009;Forcada & Abecia, 2006;Rosa & Bryant, 2003). Among these, photoperiod is regarded as the most important factor in the seasonal regulation of reproduction (Menassol, Collet, Chesneau, Malpaux, & Scaramuzzi, 2012;Nishiwaki-Ohkawa & Yoshimura, 2016). Numerous studies have confirmed that seasonal photoperiodic information is conveyed to the pineal gland through the retina.…”