Evolution of Thyroid Enhancement of Embryogenesis and Early Survival

Abstract

Iodine imparts protective antioxidant actions that improve the fitness of invertebrate organisms, and peptides carrying iodine initially appear to have served in a defensive capacity. Tyrosine carries multiple iodines in some echinoderms, and these peptides transferred to progeny serve both protective and signaling purposes. This parental relationship appears to be the most likely evolutionary basis for emergence of the vertebrate thyroid endocrine system, and its critically important development-promoting actions in larval and (later) fetal ontogeny. Thyroxine (T4) and Triiodothyronine (T3) induce settlement and stimulate transitions to alternative feeding modes in some echinoderms. This transgenerational relationship has been conserved and elaborated in vertebrates, including humans, which share common ancestry with echinoderms. Thyroid insufficiency is damaging or can be lethal to larval fishes; egg yolk that is insufficiently primed with maternal thyroid hormones (TH) results in compromised development and high mortality rates at the time of first-feeding. Maternally-derived TH supplied to offspring supports the onset of independent feeding in fishes (eye, mouth, lateral line, swim bladder and intestinal maturation) and survival by comparable developmental mechanisms in placental mammals. Fishes evolved precise control of TH secretion and peripheral processing; early metamorphic and feeding mode actions were joined by controlled thermogenesis in homeotherms.

Probiotic Treatment Enhances Pre‐feeding Larval Development and Early Survival in Zebrafish Danio rerio

“…The PTL showed Digestive function can also be disrupted by pathogens in the GI tract; LAB species like those to which the PTL group was exposed have been shown to protect Atlantic Salmon Salmo salar from intestinal damage (Ringø et al 2010). Significantly accelerated differentiation of swim bladders and eyes was also evident in the PTL group compared to the ATL group, even before the onset of feeding; visual acuity and buoyancy are essential for successful exogenous feeding by larvae (Pataueg et al 2021). The eyes and swim bladder are both subject to regulation by compounds of maternal origin (see Molla et al 2019).…”

Epigenetics and Probiotics Application toward the Modulation of Fish Reproductive Performance

“…Broodstock management is necessary for the optimization of reproductive processes in cultured fishes. Maternal health, nutrition, and endocrine status are determinants of larval capacity for survival [89]. In captive conditions, confinement under suboptimal conditions has been associated with the production of reduced milt quality in male fishes, leading to difficulties in breeding on farms [99].…”

“…The detrimental impact of stress on vitellogenesis process (for example, follicular atresia) has been recorded in salmonids such as rainbow trout, brown trout and brook trout in the last few decades [85][86][87][88]. Some fishes are far more sensitive to stress-related inhibition of their reproductive axes than others, and in such cases even mild stress or captivity can result in complete reproductive failure [89]. Water temperature and photoperiod are primary environmental cues that trigger oocyte maturation and spawning in fish [60,90,91].…”

"Study on the Prevalence of Goiter and Associated Factors Among Hospitalized Patients of District Timergara, Dir Lower Pakistan"

“…Thyroid stimulating hormone (TSH) is released by the anterior pituitary gland and helps to regulate thyroid hormone levels, which are controlled by thyrotropin releasing hormone (TRH) from the hypothalamus. A negative feedback loop is present between TRH and TSH in the circulation system, and the regulation is carried out by T4 and T3 [12,13]. An iodine deficiency causes goiter, the enlarged thyroid glands that are greater than the terminal phalanx of the thumb, which indicates chronic iodine deficiency [14].…”