Shark Hormones

Cross references:  Hormones in General      Amphioxus Hormones 
Lamprey Hormones     Teleost Hormones    
Teleost Dominance Hierarchies       Sharks & Rays  
Shark Dominance Hierarchies    Steroids   Steroid Actions 
Glucocorticoids  
 

1997   
Serum Concentrations of Steroid Hormones in the Mature Male Bonnethead Shark,Sphyrna tiburo (Goog) 
Only abstract available online. 
    "
The male bonnethead shark, Sphyrna tiburo, undergoes an annual cycle of spermatogenesis and testicular regression and recrudescence. In southwestern Florida populations, testicular development and spermatogenesis begin in late spring and peak in late summer, with mating not taking place until about 2 months after the peak.
    Steroid hormones, some of which are known to play influential, essential roles in spermatogenesis, were measured in the serum during a full annual cycle in mature males from a wild population. Serum 17β-estradiol (E2), progesterone (P4), testosterone (T), and dihydrotestosterone (DHT) concentrations were determined by radioimmunoassay.
    Serum T, DHT, and P4 concentrations followed the pattern of testicular development and regression, with all three steroid hormones attaining the highest significant levels (P < 0.001) in late summer and falling to the lowest levels in mid-winter.
    Serum E2 concentrations showed significant changes (P < 0.01) with a peak in early spring. Male bonnethead sharks had significantly lower concentrations of E2 (P < 0.001) and significantly higher concentrations of T, DHT (P < 0.001), and P4 (P < 0.05) than those published for females.
    When steroid concentrations were compared to a behavioral rating of stress, only P4showed a significant correlation to the stress behavior (P = 0.0447), but the significance was much lower than the significant correlation of P4 by month (P < 0.001)."    


2007  
Sex, seasonal, and stress-related variations in elasmobranch corticosterone concentrations  
Full length PDF available online for free.   
from the abstract
    "Serum corticosterone in S. tiburo increased following capture and again 24 h post-capture, possibly caused by interference with 1α-hydroxycorticosterone, the primary stress hormone in elasmobranchs."
    "These results indicate that corticosterone has a limited role, if any, in
acute and chronic stress associated with capture in S. tiburo, but likely has physiological functions associated with its glucocorticoid properties across the reproductive cycle of both species."  
from the text 

    "The steroid hormone 1α-hydroxycorticosterone (1α-OHB) is considered the major stress hormone in elasmobranchs, but corticosterone (CS) is also found in measurable concentrations in a number of different elasmobranchs
    Although considered primarily a stress hormone in many different taxa, CS has a number of other functions. Like other glucocorticoids, CS can regulate energy balance and lipogenesis, promote feeding behavior, stimulate nitrogen metabolism and gluconeogenesis, and inhibit sexual behaviors. ... In elasmobranchs, both CS and 1α-OHB are produced by the interrenal gland by conversion from progesterone ..." 
    "... seasonal changes in both cortisol and CS, which indicates seasonal regulation of physiologic state, including body mass, energy reserves, and reproductive function ... were found in ...  amphibians, reptiles, marine teleosts, and human males.  Romero provided a thorough review of seasonal changes in glucocorticoid concentrations in wild vertebrates that showed glucocorticoids were frequently elevated during the breeding season in free-living reptiles, amphibians, and birds, but not mammals.
    Corticosterone seasonal changes also co-vary with testosterone in female bullfrogs, male stingrays and Galápagos tortoises, but are negatively correlated with testosterone concentrations in the crested newt.
    However, little is known about seasonal variations or functions of CS in relation to elasmobranch reproduction.
    Sex differences in glucocorticoid concentrations are found in such diverse taxa as mammals, amphibians, reptiles, and fish, e.g., the bullfrog, Rana catesbeiana, ... immature whitetip reef sharks, Triaenodon obesus, and Atlantic stingrays, Dasyatis sabina. Glucocorticoids can have sex specific effects on behavior that inhibit the attractiveness of certain mates or responses to potential competitors, but such effects on elasmobranch behavior are unknown.
    Glucocorticoids in most vertebrates are secreted in response to various stressors. Acute stressors, such as capture and handling, often cause increased glucocorticoid concentrations, usually within 2–10 min, depending on the taxa involved. Chronic stressors, such as maintenance of wild animals in captivity, cause a more prolonged elevation measured in days or longer, that is dependent on the severity of the chronic stress. Elasmobranchs are especially susceptible to both acute and chronic stress associated with capture, handling and maintenance in captivity, but the relationship between corticosterone concentrations and stressors remains unexamined in this vertebrate group."   
    "At concentrations attained during acute or chronic stress, glucocorticoids are known to inhibit gonadal hormone release" 
    "The present study demonstrates both a short- and long-term  corticosterone response to capture and handling stress in an elasmobranch species. However, future studies are needed to examine the relationship between CS and stress because corticosterone appears not to be the major stress hormone in elasmobranchs and elevations observed in the present study may be due to interference by 1α-OHB rather than actual elevations in CS." 
My comment #1
    Since the "steroid hormone 1α-hydroxycorticosterone (1α-OHB)" which is considered the major stress hormone in elasmobranchs is not discussed in   Steroids  , I've offered two online references  to it, below.  Don't be confused by the different abbreviations:  1α-OHB = 1alpha-B  . 
ref 1

    The Evolution of Steroid Receptor-Hormone Interactions
(Goog) 
http://evodevo.uoregon.edu/people/carroll.html 

Short article available online for free.  Very highly recommended. 
    "1α-hydroxycorticosterone (1α-B), a steroid found only in elasmobranch fishes"   
ref 2
    Regulation of interrenal gland steroidogenesis in the Atlantic stingray
(PubMed)  
Only abstract available online. 
    "
The interrenal gland (the homologue of the mammalian adrenal cortex) of elasmobranchs (sharks, skates, and rays) produces 1alpha-hydroxycorticosterone (1alpha-B), which has been reported to function both as a gluco- and mineralocorticosteroid.

My comment #2
    There were some references from the above that I found interesting.  However, there were relevant to glucocorticoids in general, so I've moved them to the
Glucocorticoids   page.   


2008   
Serum levels of reproductive steroid hormones in captive sand tiger sharks, Carchariastaurus (Rafinesque), and comments on their relation to sexual conflicts 
(Goog) 
Only abstract available online.  I got the PDF through the library.   
    "
The steroid levels obtained showed distinct annual hormonal cycles in the male sharks and corroborated a biennial cycle for the single serially-sampled female shark. Furthermore, the steroid levels for individual males correlated with sexual conflicts as well as their position within the male dominance hierarchy.
"   


2008   
Evolution of Hormone Signaling in Elasmobranchs by Exploitation of Promiscuous Receptors  
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721552/?tool=pubmed 
Full length article available online for free. 
from the Abstract
    "
The hormone 1α-hydroxycorticosterone (1α-B) is a physiologically important steroid synthesized only in elasmobranchs. We show that 1α-B modulates gene expression in vitro by activating two paralogous intracellular transcription factors, the mineralocorticoid receptor (MR) and glucocorticoid receptor (GR), in the little skate Leucoraja erinacea; MR serves as a high-sensitivity and GR as a low-sensitivity receptor. Using functional analysis of extant and resurrected ancestral proteins, we show that receptor sensitivity to 1α-B evolved millions of years before the hormone itself evolved. The 1α-B differs from more ancient corticosteroids only by the addition of a hydroxyl group; the three-dimensional structure of the ancestral receptor shows that the ligand pocket contained ample unoccupied space to accommodate this moiety. Our findings indicate that the interactions between 1α-B and elasmobranch GR and MR proteins evolved by molecular exploitation: a novel hormone recruited into new functional partnerships two ancient receptors that had previously interacted with other ligands. The ancestral receptor's promiscuous capacity to fortuitously bind compounds that are slight structural variants of its original ligands set the stage for the evolution of this new interaction."      


2009   
Characterization of the neurohypophysial hormone gene loci in elephant shark and the Japanese lamprey: origin of the vertebrate neurohypophysial hormone genes  (Goog) 
Full length HTML and PDF available online for free. 
    "
The cartilaginous fishes are divided into two groups: elasmobranchs (sharks, rays and skates) and holocephalians (chimaeras). The elephant shark is a holocephalian chimaera ... We chose elephant shark as a representative cartilaginous fish because it has the smallest genome (910 Mb) among cartilaginous fishes [11,12].

    See:  Lamprey Neuropeptides





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