Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The soupfin shark, Galeorhinus galeus, is a circum-global shark species of great economical
importance. Their reproductive biology is reasonably well understood, but intraspecific
differences between global populations necessitate the study o f populations separately. For
this study, 70 male and 74 female specimens were collected along the southwestern coast of
South Africa between 34°8'S; 18°27'E and 34°24S; 21°25'E. Morphological changes were
described and serum steroid hormone concentrations evaluated by enzyme-linked
immunosorbent assay (ELISA) over an almost-complete reproductive cycle. Males display an
annual spermatogenic cycle that starts with a significant peak in testosterone concentrations
coinciding with the start o f spermatogenesis around April-May. Testosterone levels decrease
to reach a minimum in late-winter after which spermiogenesis commences. The prevalence of
spermiogenic cysts in the testis increase to reach a peak between February and April, after
which mating occurs until about July. Females (aplacentally viviparous) are suggested to
have a triennial cycle, similar to the Brazilian & Australian populations, but different from the
Californian & Mediterranean populations. During the first year after parturition there is not
much reproductive development. The following year sees increased vitellogenic activity in
ovarian follicles and development of the oviducal glands and uteri. Ovulation then occurs
towards the end of that year. Mating is suggested to precede ovulation by two to three months
necessitating sperm storage by the females in their oviducal glands. A 12-15 month gestation
ensues and ends in parturition the following summer. Testosterone and estradiol levels
fluctuate together and are involved in the preparation for ovulation and oviducal gland
development. Progesterone levels show two distinct peaks during the year, in both immature
and mature females, and could not yet be functionally linked to any reproductive activity or
condition. This cycle is not very tightly synchronised among the South African females. / AFRIKAANSE OPSOMMING: Die vaalhaai, Galeorhinus galeus, kom wereld-wyd voor en is van groot ekonomiese belang
in baie lande. Die spesie se voorplantings biologie is reeds redelik deeglik ondersoek maar
intraspesifieke verskille tussen verskillende wereld populasies noodsaak die bestudering van
populasies afsondelik. Daar is 70 mannetjies en 74 wyfies versamel vir hierdie studie langs
die Suid Afrikaanse suid-wes kus tussen 34°8'S; 18°27'E and 34°24S; 21°25'E. Morfologiese
veranderinge is beskryf en serum hormoon konsentrasies is ge-evalueer deur middel van die
ELISA tegniek vir 'n amper-volledige voortplanting siklus. Mannetjies vertoon 'n jaarlikse
spermatogeniese siklus met 'n piek in testosteroon konsentrasies aan die begin van
spermatogenese in April-Mei. Hiema daal testosteroon vlakke tot minimum vlakke in die
laat-winter, waama spermiogenese begin. Die proporsie spermiogeniese siste in die testis
vermeerder tot maksimum waardes bereik word tussen Februarie en April. Paring vind hiema
plaas tot omtrent Julie. Wyfies (aplasentaal vivipaar) het 'n voorgestelde driejaarlikse siklus,
soortgelyk aan die Brasiliaanse & Australiese populasies maar anders as die Kalifomiese &
Mediterreense populasies. Tydens die eerste jaar na bevalling vind daar nie veel
voortplantings ontwikkeling plaas nie. Die daaropvolgende jaar verhoog vitellogeniese
aktiwiteit in die ovarium follikels en ontwikkeling van die dopkliere en uteri. Ovulasie vind
nader aan die einde van hierdie jaar plaas. Paring vind heel moontlik twee tot drie maande
voor ovulasie plaas, wat noodsaak dat die wyfies sperm moet stoor in hulle dopkliere. 'n 12-
15 maande dratyd begin na ovulasie en eindig in geboorte teen die volgende somer.
Testosteroon en estradiol konsentrasies fluktueer saam en speel 'n rol tydens voorbereidings
vir ovulasie en dopklier ontwikkeling. Progesteroon vlakke piek twee maal gedurende die
jaar, in beide onvolwasse en volwasse wyfies, maar dit kon nog nie funksioneel geassosieer
word met enige voortplantings aktiwiteit of toestand nie. Die siklus is nie baie nou
gesinkroniseer onder die Suid Afrikaanse wyfies nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52431 |
| Date | 12 1900 |
| Creators | Theron, Daniel Frederick |
| Contributors | Van Wyk, J. H., Sadie, D., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 123 p. : ill. |
| Rights | Stellenbosch University |
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