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Differences in sexual development in inbred and outbred zebrafish (Danio rerio) and implications for chemical testing

Differences in sexual development in inbred and outbred zebrafish (Danio rerio) and implications for chemical testing
Differences in sexual development in inbred and outbred zebrafish (Danio rerio) and implications for chemical testing
Outbred laboratory animal strains used in ecotoxicology are intended to represent wild populations. However, breeding history may vary considerably between strains, driving differences in genetic variation and phenotypes used for assessing effects of chemical exposure. We compared a range of phenotypic endpoints in zebrafish from four different “breeding treatments” comprising a Wild Indian Karyotype (WIK) zebrafish strain and a WIK/Wild strain with three levels of inbreeding (FIT = n, n + 0.25, n + 0.375) in a new Fish Sexual Development Test (FSDT). There were no differences between treatments in terms of egg viability, hatch success or fry survival. However, compared with WIKs, WIK/Wild hybrids were significantly larger in size, with more advanced gonadal (germ cell) development at the end of the test (63 days post fertilisation). Increasing the levels of inbreeding in the related WIK/Wild lines did not affect body size, but there was a significant male-bias (72%) in the most inbred line (FIT = n + 0.375). Conversely, in the reference WIK strain there was a significant female-bias in the population (80% females).

Overall, our results support the use of outbred zebrafish strains in the FSDT, where one of the core endpoints is sex ratio. Despite increased variance (and reduced statistical power) for some endpoints, WIK/Wild outbreds (FIT = n) met all acceptance criteria for controls in this test, whereas WIKs failed to comply with tolerance limits for sex ratio (30–70% females). Sexual development was also more advanced in WIK/Wild outbreds (cf. WIKs), providing greater scope for detection of developmental reproductive toxicity following chemical exposure.
27-38
Brown, Andrew Ross
a1559845-3808-4116-8fc2-9480019a9aef
Bickley, Lisa
88a23de3-c23f-41bf-a57e-3a8484ca5244
Ryan, Thomas
ea35c378-0f6e-4ea0-8a55-2a8703d85412
Owen, Stewart
814ac720-464c-4d91-9491-c1fa9d9c5076
Paull, Gregory
316cca2e-0eca-49da-8f14-d8367c93cc5e
Hamilton, Patrick
23ab808a-4723-4fb3-a283-8d8ee4ab5548
Sharpe, Alan
0cb34473-4fa1-400f-a53d-31f89aad60f8
Tyler, Charles
edc5379c-81a3-4348-94c9-d61ba33e7acc
Brown, Andrew Ross
a1559845-3808-4116-8fc2-9480019a9aef
Bickley, Lisa
88a23de3-c23f-41bf-a57e-3a8484ca5244
Ryan, Thomas
ea35c378-0f6e-4ea0-8a55-2a8703d85412
Owen, Stewart
814ac720-464c-4d91-9491-c1fa9d9c5076
Paull, Gregory
316cca2e-0eca-49da-8f14-d8367c93cc5e
Hamilton, Patrick
23ab808a-4723-4fb3-a283-8d8ee4ab5548
Sharpe, Alan
0cb34473-4fa1-400f-a53d-31f89aad60f8
Tyler, Charles
edc5379c-81a3-4348-94c9-d61ba33e7acc

Brown, Andrew Ross, Bickley, Lisa, Ryan, Thomas, Owen, Stewart, Paull, Gregory, Hamilton, Patrick, Sharpe, Alan and Tyler, Charles (2012) Differences in sexual development in inbred and outbred zebrafish (Danio rerio) and implications for chemical testing. Aquatic Toxicology, 112–113, 27-38. (doi:10.1016/j.aquatox.2012.01.017).

Record type: Article

Abstract

Outbred laboratory animal strains used in ecotoxicology are intended to represent wild populations. However, breeding history may vary considerably between strains, driving differences in genetic variation and phenotypes used for assessing effects of chemical exposure. We compared a range of phenotypic endpoints in zebrafish from four different “breeding treatments” comprising a Wild Indian Karyotype (WIK) zebrafish strain and a WIK/Wild strain with three levels of inbreeding (FIT = n, n + 0.25, n + 0.375) in a new Fish Sexual Development Test (FSDT). There were no differences between treatments in terms of egg viability, hatch success or fry survival. However, compared with WIKs, WIK/Wild hybrids were significantly larger in size, with more advanced gonadal (germ cell) development at the end of the test (63 days post fertilisation). Increasing the levels of inbreeding in the related WIK/Wild lines did not affect body size, but there was a significant male-bias (72%) in the most inbred line (FIT = n + 0.375). Conversely, in the reference WIK strain there was a significant female-bias in the population (80% females).

Overall, our results support the use of outbred zebrafish strains in the FSDT, where one of the core endpoints is sex ratio. Despite increased variance (and reduced statistical power) for some endpoints, WIK/Wild outbreds (FIT = n) met all acceptance criteria for controls in this test, whereas WIKs failed to comply with tolerance limits for sex ratio (30–70% females). Sexual development was also more advanced in WIK/Wild outbreds (cf. WIKs), providing greater scope for detection of developmental reproductive toxicity following chemical exposure.

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Accepted/In Press date: 21 January 2012
Published date: 15 May 2012

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Local EPrints ID: 414013
URI: https://eprints.soton.ac.uk/id/eprint/414013
PURE UUID: a5883d86-781f-4c2f-aac0-3914051f8a70

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Date deposited: 12 Sep 2017 16:31
Last modified: 14 Aug 2019 17:33

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