| Title |
-
en
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis
|
| Creator |
|
| Accessrights |
metadata only access |
| Subject |
-
Other
en
Gas chromatography-flame ionization detection
-
Other
en
northern fur seal
-
Other
en
reproductive status
-
Other
en
steroid hormones
-
Other
en
testosterone
-
Other
en
time-resolved fluoroimmunoassay
-
NDC
480
|
| Description |
-
Abstract
en
Information about the reproductive status of free-ranging pinnipeds provides useful insight into their population dynamics, which is essential to their management and conservation. To determine the reproductive status of individual animals, blood sampling is often required despite being impractical to collect in open water. Hair as an endocrine marker has been used to less invasively assess the reproductive status of terrestrial animals. However, it is unknown whether pinniped reproductive status can be assessed from hair samples. Here, we examine testosterone levels in hair obtained from 57 male northern fur seals and used it to compare their age class and spermatogenesis during the non-breeding season off Hokkaido. We isolated testosterone from the samples using gas chromatography and measured testosterone levels using time-resolved fluoroimmunoassay. Testosterone levels in hair increased towards the breeding season. In May, testosterone levels were the highest in seals aged between 4 and 7 years, followed by those over the age of 8 years and under the age of 4 years. Spermatids, the final phase of spermatogenesis, werepresent inthe seals sampled between April and June, eventhough testosterone levels were lowin April. The seals with spermatids in May showed the highest testosterone levels. Our results demonstrate that seals with higher testosterone levels in May are likely to be mature males (>= 4 years). Since hair can be collected using biopsy darts in the field, it will be possible to less invasively determine testosterone levels of male seals in the future.
|
| Publisher |
en
Oxford University Press
|
| Date |
|
| Language |
|
| Resource Type |
journal article |
| Version Type |
NA |
| Identifier |
HDL
http://hdl.handle.net/2115/83650
|
| Relation |
-
isIdenticalTo
DOI
https://doi.org/10.1093/conphys/coab031
|
| Journal |
-
-
PISSN
2051-1434
-
en
Conservation Physiology
-
Volume Number9
Page Start1
Page End11
|
| Oaidate |
2023-07-26 |
