Developing methodologies that will allow biomarkers in skeletal muscle tissue to be used as a reliable, noninvasive technique for the study of elasmobranch reproductive biology. This method holds great promise as skeletal muscle has been shown to act as a depot for steroid hormones and their metabolites in other species.
Why this is important:
According to the IUCN Red List, approximately 75% of all elasmobranchs (sharks, skates, and rays) are threatened, or lacking sufficient data necessary for proper management. An important step in reversing this trend is developing non-lethal techniques or protocols for the study of their life history characteristics.
Reproduction is one such life history trait that must be fully understood if successful management of these cartilaginous fish is to occur. Without information regarding when elasmobranchs mature and reproduce, population demography or stock assessments can never be adequately conducted. Unfortunately, existing information regarding sexual maturity and reproductive cycles in elasmobranchs is largely based on gross examination of morphological changes associated with reproductive organs and structures (i.e. testes in males and ovary weight in females). While this information has proven valuable in obtaining reproductive information, collecting pertinent data requires that specimens be sacrificed. This can be problematic, especially for species that have been classified as endangered or threatened.
Recently, circulating concentrations of plasma steroid hormones, such as 17-?-estradiol, progesterone, and testosterone, have been used with gross morphological changes to evaluate events associated with reproductive cycles and sexual maturity in a number of sharks, skates, and rays. The results from such studies indicate that morphological changes in reproductive tracts and gonadal steroid hormone biosynthesis are intimately linked in elasmobranch reproduction. That is, as the reproductive tracts become active, they begin to produce more hormones. While research suggests that plasma steroid hormone concentrations alone can provide the necessary information to gauge sexual maturity and reproductive cycle status of elasmobranchs by non-lethal means, drawing blood to obtain a plasma sample from large specimens is problematic. Thus, unless other non-lethal methods can be identified, management related information regarding reproductive biology for prohibited or large species will remain difficult if not impossible to obtain.
Aims and Objectives
This project seeks to develop the methodologies that will allow hormone concentrations in skeletal muscle tissue to be used as a reliable and noninvasive surrogate for the study of elasmobranch reproductive biology representing four different reproductive modes:
- oviparous [Leucoraja erinacea];
- placental viviparous [Rhizoprionodon terraenovae];
- lecithotrophic aplacental viviparous [Squalus acanthias];
- matrotrophic aplacental viviparous [Dasyatis Sabina].
These species were chosen for this study because they have robust populations within their given geographic ranges.
October has been a very busy month for us up here at the University of New England. We spent much of the month finishing up a manuscript detailing our methodologies and results to date for submission to the journal of…
August has been a great month. Early on we traveled to Vancouver, Canada for the Annual Meeting of the American Elasmobranch Society, where we presented some of our preliminary data in a presentation entitled, “Potential Utilization of Steroid Hormones Extracted…
The annual meeting of the American Elasmobranch Society, being held this year in conjunction with the World Congress of Herpetology, will be held in Vancouver Canada from August 8-14th. We are looking forward to presenting data from our spiny dogfish…
In mid May we traveled down to Ocean Springs Mississippi to work with fisheries biologist Jill Hendon at the Gulf Coast Research Lab. We were lucky enough to participate in multiple shark field surveys while at the lab. We were…
Field and lab work have been going great here in Maine. We have been collecting samples and extracting hormones back in the lab. We have two trips to the Gulf of Mexico planned for this summer, one of which we…