Effects of hyperthyroidism in the development of the appendicular skeleton and muscles of zebrafish, with notes on evolutionary developmental pathology (Evo-Devo-Path)

Abstract

The hypothalamus-pituitary-thyroid (HPT) axis plays a crucial role in the metabolism, homeostasis, somatic growth and development of teleostean fishes. Thyroid hormones regulate essential biological functions such as growth and development, regulation of stress, energy expenditure, tissue compound, and psychological processes. Teleost thyroid follicles produce the same thyroid hormones as in other vertebrates: thyroxin (T4) and triiodothyronine (T3), making the zebrafish a very useful model to study hypo- and hyperthyroidism in other vertebrate taxa, including humans. Here we investigate morphological changes in T3 hyperthyroid cases in the zebrafish to better understand malformations provoked by alterations of T3 levels. In particular, we describe musculoskeletal abnormalities during the development of the zebrafish appendicular skeleton and muscles, compare our observations with those recently done by us on the normal developmental of the zebrafish, and discuss these comparisons within the context of evolutionary developmental pathology (Evo-Devo-Path), including human pathologies.

Direct development of the catfish pectoral fin: An alternative pectoral fin pattern of teleosts

“…These hormoneinduced experimental heterochronies often result in the abnormal pectoral fin phenotype. [20][21][22][53][54][55] TH developmental profiles in the studied ontogenetic series of C. gariepinus differ from each other. All series display a surge of the TH level associated with the pronounced increase in body length and active ossification of the cranial and postcranial skeleton.…”

“…[16][17][18][19] The fin's larval-adult transition is a part of complex metamorphic transformation that affects various organs and tissues and proceeds under the thyroid hormones' control. 18,[20][21][22][23][24][25] However, the remarkable morphological and functional diversity of teleosts' pectoral fin allows suggesting the hidden developmental potential and existence of lineage specific developmental patterns. 26 Here, we present a thorough description of the development of the pectoral fin skeleton and soft tissues in the North African (African sharptooth) catfish, which displays an alternative fin pattern characterized by a lack of the larval stage typical of other teleosts.…”

“…Participation in respiration is regarded as the primary function of the larval fin, 14,15 whereas the adult fin carries other functional loads: locomotion, sensitivity, defense, etc 16‐19 . The fin's larval‐adult transition is a part of complex metamorphic transformation that affects various organs and tissues and proceeds under the thyroid hormones’ control 18,20‐25 …”

Role of dietary probiotic Ecotec in growth enhancement, thyroid tuning, hematomorphology and resistance to pathogenic challenge in Labeo rohita juveniles

“…They found an increase in total fat and protein content in the probiotic treated group which can be due to high feed intake in probiotic treated fish. Thyroid hormones, secreted from the hypothalamic-pituitary-thyroid axis, are responsible for body metablosim, growth, behaviour, immunoregulation and stress reponses in fish (Dorshkind and Horseman 2001;Peter 2011;Shkil et al 2019). Therefore, variation T3, T4 and TSH levels can be used to monitor essential biological functions of fish.…”

“…Depressed growth, lowered immune response and NBT activity has been reported in L.rohita when given a high oral administration of T3 (Sahoo 2003). Elevated levels of thyroid hormones can cause 'hypothyroidism' in fish producing severe irregularities in nervous and/or metabolic systems (Vancamp et al 2018;Shkil et al 2019). Higher levels of T3/T4 might cause a negative impact on fish specific immune response than the non-specific one resulting in high susceptibility to infections.…”