PARENT SESSION
COMPARATIVE ASPECTS OF REPRODUCTION
Harborside C
7:30 AM-10:00 AM

(402) A STUDY IN REPRODUCTIVE BIOLOGY AND ENDOCRINOLOGY OF A PRIMITIVE TELEOSTEI, THE AMERICAN SHAD (Alosa sapidissima).

Abraham, Eytan¹, Richardson, Brian², Minkkinen, Steven², Alok, Deoraj¹, Zohar, Yonathan¹, ¹ Maryland Biotechnology Institute, Baltimore, MD² Maryland Department of Natural Resources, Annapolis, MD

ABSTRACT- American shad is an anadromous fish that displays an asynchronous spawning pattern. In an effort to enhance our understanding of the reproductive cycle of this primitive Teleostei species, and provide better management tools for the Chesapeake fishery, we have conducted studies of its gonadal and hormonal cycles. Fish were collected from the Susquehanna River during their spawning migration. One group of fish was sacrificed on site. Ovarian biopsies were collected and evaluated to assess the stage of ovarian development by examining oocyte size and morphology. Milt was collected and assessed for volume, spermatozoid count and motility. Lueteinizing hormone (LH), testosterone (T) and 11-ketotestosterone levels were measured in the male blood plasma. LH, T, 17-estradiol (E₂), 17,20-dihydroxy-4-pregnen-3-one and 17,20, 21-trihydroxy-4-pregnen-3-one were measured in the female blood plasma. The levels of three gonadotropin-releasing hormones that we have identified in the shad (sGnRH, hGnRH and cGnRH-II) were measured in brain samples. A second group was transported to the Maryland State hatchery and treated with gonadotropin-releasing hormone agonist (GnRHa) in the form of EVAc implants (75g/kg) or GnRHa microspheres (75g/kg) or with a sham treatment. These treatments were followed during a two-week period by measurement of the same parameters examined in the first group. In addition, fecundity and fertilization of the hatchery groups were measured by daily collection and examination of spawned eggs. Results are currently being analyzed with the objective of elucidating the hypothalamo-pituitary-gonadal axis in this primitive Teleostei model.

KEY WORDS: GnRH, Fish, Shad, Implants