Reproductive endocrinology in chondrichthyans: The present and the future

Awruch, CA

doi:10.1016/j.ygcen.2013.05.021

Cited by 70 publications

(75 citation statements)

References 128 publications

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“…Measurement of steroid hormones has the potential to be used as a non-lethal technique to address reproduction of whale sharks. Indeed, in a number of elasmobranches, steroid hormone profiles are associated with reproductive events such as sexual maturity and reproductive cycle (Koob et al, 1986;Rasmussen and Gruber, 1993;Sulikowski et al, 2006Sulikowski et al, , 2007Awruch et al, 2008a, b;Henningsen et al, 2008;Hoffmayer et al, 2010;Awruch, 2013;Williams et al, 2013). Thus, the continuous measurement of steroid hormones could be used to detect sexual maturity in female whale sharks.…”

Section: Resultsmentioning

confidence: 99%

Gonadal Morphology, Histology, and Endocrinological Characteristics of Immature Female Whale Sharks,Rhincodon typus

Nozu¹,

Murakumo²,

Matsumoto³

et al. 2015

Zoological Science

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Captive breeding of whale sharks is one of the great challenges for aquariums. However, there is limited information available related to reproductive physiology due to the difficulty of sampling and long-term observation. In the present report, we provide information on the reproductive physiology of female whale sharks, which were incidentally captured as bycatch in a set-net off the coast of Okinawa, Japan. Total lengths of three captured female whale sharks were 403, 665, and 761 cm, respectively, at the time of their death. Collected paired ovaries differed in size between right and left. However, it seems not to determine which side of ovary becomes developed. Histological observations revealed that oocytes surrounded by follicle cell layers localized in the developed ovary, and most developed oocytes exhibited yolk vesicle stage. Additionally, in the largest specimen, there were low levels of three steroid hormones (Testosterone, Dihydrotestosterone, and Estradiol-17ß) that did not show seasonal variation. The present results indicate that even the whale shark over 7 m in TL are still histologically and endocrinologically immature. We expect that the present data will provide fundamental information related to reproductive physiology of female whale sharks, and will contribute to protection activities and increased success in captive breeding of whale sharks.

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Section: Resultsmentioning

confidence: 99%

Gonadal Morphology, Histology, and Endocrinological Characteristics of Immature Female Whale Sharks,Rhincodon typus

Nozu¹,

Murakumo²,

Matsumoto³

et al. 2015

Zoological Science

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“…However, this could be coincidental because increases in sex steroids associated with ovulation during late-gestation also occur in R. taylori 23. Because sex steroid concentrations can vary depending on reproductive modes and species20, documenting species-specific cycles in sex steroid concentrations of wild-caught females are necessary in future studies to better understand the effects of captivity and experimental conditions when assessing the potential implications of fisheries capture.…”

Section: Discussionmentioning

confidence: 99%

“…In S. tiburo the maternal deposition of hormones in yolk is correlated with circulating concentrations during vitellogenesis and may influence aspects such as embryonic growth and sex differentiation72. Estradiol regulation of yolk synthesis by the liver may also be affected, influencing the quality of yolk available during early embryonic development20. Furthermore, declines in E 2 have been suggested as possible causes of lower fertility rates in chondrichthyans by impairing sperm storage73.…”

Section: Discussionmentioning

confidence: 99%

“…Reproductive consequences of stress are largely mediated by the maternal endocrine response which regulates energy allocated to self-maintenance relative to reproduction itself19. Little is known about endocrine regulation of reproduction in chondrichthyans, including the roles of the primary sex steroids 17β-estradiol (E 2 ), progesterone (P 4 ) and testosterone (T), but it appears structurally and functionally similar to other vertebrates20. However, because of the diversity of reproductive strategies within chondrichthyan viviparity, ranging from lecithotrophic viviparity to placental viviparity, it is difficult to generalise the roles of hormones regulating reproductive events20.…”

mentioning

confidence: 99%

“…Little is known about endocrine regulation of reproduction in chondrichthyans, including the roles of the primary sex steroids 17β-estradiol (E 2 ), progesterone (P 4 ) and testosterone (T), but it appears structurally and functionally similar to other vertebrates20. However, because of the diversity of reproductive strategies within chondrichthyan viviparity, ranging from lecithotrophic viviparity to placental viviparity, it is difficult to generalise the roles of hormones regulating reproductive events20. For several species examined so far, E 2 is generally associated with follicular development and yolk uptake followed by increases in P 4 at the onset of ovulation.…”

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confidence: 99%

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Prenatal stress from trawl capture affects mothers and neonates: a case study using the southern fiddler ray (Trygonorrhina dumerilii)

Guida

Awruch

Walker

et al. 2017

Sci Rep

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Assessing fishing effects on chondrichthyan populations has predominantly focused on quantifying mortality rates. Consequently, sub-lethal effects of capture stress on the reproductive capacity of chondrichthyans are largely unknown. We investigated the reproductive consequences of capture on pregnant southern fiddler rays (Trygonorrhina dumerilii) collected from Swan Bay, Australia, in response to laboratory-simulated trawl capture (8 h) followed immediately by air exposure (30 min). Immediately prior to, and for up to 28 days post trawling, all females were measured for body mass (BM), sex steroid concentrations (17-β estradiol, progesterone, testosterone) and granulocyte to lymphocyte (G:L) ratio. At parturition, neonates were measured for total length (TL), BM and G:L ratio. Trawling reduced maternal BM and elevated the G:L ratio for up to 28 days. Trawling did not significantly affect any sex steroid concentrations relative to controls. Neonates from trawled mothers were significantly lower in BM and TL than control animals, and had an elevated G:L ratio. Our results show that capture of pregnant T. dumerilii can influence their reproductive potential and affect the fitness of neonates. We suggest other viviparous species are likely to be similarly affected. Sub-lethal effects of capture, particularly on reproduction, require further study to improve fisheries management and conservation of chondrichthyans.

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Identification of essential habitats: Including chimaeras into current shark protected areas

Barnett

McAllister²,

Semmens³

et al. 2019

Aquatic Conservation

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1. Essential habitats are areas required to support specific functions, such as providing foraging grounds, shelter or used for reproductive purposes. For mobile aquatic species that move throughout numerous components of the seascape, identifying essential habitats within a species' broader distribution range is crucial to understanding their ecology and provide vital information needed to underpin effective conservation and management (e.g. the implementation of protected areas). 2. In Tasmania (Australia), a number of coastal habitats have been declared shark refuge areas (SRAs), where fishing for elasmobranchs (sharks, rays and skates) is prohibited.3. Chimaeras are relatives of elasmobranchs (class Chondrichthyes) and share traits that predispose many elasmobranch species to be vulnerable to overfishing (e.g. slow growth rates and low reproductive output). However, fishing for elephantfish Callorhinchus milii (the chimaera species found in coastal Tasmania) is still permitted in SRAs. 4.Here, a combination of acoustic tracking, catch data and reproductive information was used to determine the significance of the SRA coastal habitats for C. milii. 5.Results suggest that these areas are essential habitats for reproduction and likely important for other purposes, such as foraging. 6. Given that a key strategy in managing fish stocks is protecting areas important for reproduction, and the importance of these coastal areas of Tasmania for C. milii reproductive purposes, we recommend including C. milii in current SRAs, and decreeing these areas as chondrichthyan refuge areas.

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Reproductive endocrinology in chondrichthyans: The present and the future

Cited by 70 publications

References 128 publications

Gonadal Morphology, Histology, and Endocrinological Characteristics of Immature Female Whale Sharks,Rhincodon typus

Gonadal Morphology, Histology, and Endocrinological Characteristics of Immature Female Whale Sharks,Rhincodon typus

Prenatal stress from trawl capture affects mothers and neonates: a case study using the southern fiddler ray (Trygonorrhina dumerilii)

Identification of essential habitats: Including chimaeras into current shark protected areas

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