Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: PELOMEDUSA SUBRUFA is a freshwater turtle widely distributed throughout Africa and
Madagascar, and is described as a Tropical to Sub-tropical species. 1 examined the female and
male reproductive cycles of P. subrufa, over a 20-month period to determine whether they
display a typical Tropical to Sub-tropical type reproductive cycle (pre-nuptial) or a typical
Temperate Zone type reproductive cycle (post-nuptial). Blood and tissue samples were collected
from wild specimens captured in the Western Cape, South Africa and these samples were
supplemented by tissue samples obtained from museum specimens.
In female P. subrufa seasonal variation in related circulating reproductive hormones in
the plasma (estradiol, progesterone, and testosterone) were analyzed using validated ELISA kits.
Plasma vitellogenin (yolk precursor produced in liver) was measured using a newly developed
universal vitellogenin ELISA for vertebrates (UNIVTG). Ovarian follicles were measured (± 0.1
mm) and female ovaries were staged macroscopically (non-active, pre-vitellogenic, vitellogenic,
gravid), and results were confirmed via histological sectioning of ovaries and oviducts.
Females exhibited a cyclic reproductive pattern, with distinct phases of follicular
enlargement (vitellogenesis), ovulation and a gravid period. Seasonal timing of the reproductive
cycle coincided with those of other temperate zone freshwater turtles. Vitellogenic
recrudescence began in summer (late December), and continued unabated through winter with
ovulation occurring in the following spring (September-October). My data suggested that P.
subrufa females mostly lay a single clutch of eggs during the late-spnng summer period
(September through January). Clutch size varied between 7 -3 7 eggs, with the number of eggs
being significantly correlated with maternal body size (r = 0.82, P < 0 001). Plasma estradiol
and plasma vitellogenin concentrations peaked once during the ovarian cycle, typically coinciding with the period of early- to mid-vitellogenesis in late summer. Plasma testosterone
varied throughout the year, but significant increases were measured during the ovulation and
mating period in spring. Plasma progesterone concentrations were significantly elevated during
the gestation period prior to ovi-position in mid-summer (December).
In male P. subrufa spermatogenesis in mature specimens was distinctly seasonal and
timing of the reproductive cycle coincided with those of other temperate zone freshwater turtles.
Spermatogemc recrudescence began in summer, following emergence from a winter hibernation
period (brumation) and spring mating. Peak testicular volume and maximum spermiogemc
activity occurred in late summer and early autumn. Testicular regression commenced in autumn
through winter. Spermatozoa were abundant in the ducti epididymi throughout the year. Plasma
testosterone concentrations peaked once during the testicular cycle, typically coinciding with
spermio genes is in late summer, early autumn. Ducti epididymi diameter showed significant
variation throughout the year, whereas the epithelial cell height showed no significant seasonal
variation. Peak secretory activity coincided with spermiogemc activity and high circulating
testosterone concentrations in late summer, early autumn. Testicular recrudescence was
correlated with increasing ambient air temperatures, photopenod and summer rainfall, whereas
testicular regression, during late autumn, corresponded conversely with decreasing ambient air
temperatures, photopenod and rainfall. Female and male reproductive cycles were asynchronous
in that the peak spermatogenic activity occurred in autumn at the time when most females were
depositing yolk in growing ovarian follicles. Therefore, adult females displayed a typical postnuptial
vitellogemc cycle and adult males displayed a typical post-nuptial spermatogenic cycle.
Differences between sexes in body size are common in many animals, and the African
helmeted turtle is no exception. Sexual size dimorphism (SSD) in P. subrufa was pronounced, and using principal component analysis, it was clear that adult male P. subrufa was significantly
larger than adult females. Using carapace length as the measure of body size (covariate), adult
males, adult females, and juveniles differed significantly in absolute size of the carapace width,
carapace depth, plastron length, plastron width, and head depth. However, there was no
significant difference between adult males, adult females and juveniles in head width and head
length. Therefore, adult males were larger than adult females in the seven traits measured,
except in carapace depth where the females were significantly larger In the occurrence of
ontogenetic growth patterns, the adults grow at a slower rate than juveniles in plastron length.
There was no significant difference between adults and juveniles in shell width, however in
depth, the adults grow at a faster rate when compared to the juveniles. Adults significantly grow
at a faster rate than juveniles in absolute head size as well. However, when these traits were used
as a whole data set (eight traits measured), there was no difference in growth rate between adults
of either sex. Similarly, there was no significant difference in adults compared to juveniles in
shell size, however, adults grow at a faster rate than juveniles in absolute body size and head
size. Differences in body size, and in the size of traits such as shell measurements and head
measurements relative to absolute body size, were assessed to clarify SSD of P. subrufa in South Africa. / AFRIKAANSE OPSOMMING: PELOMEDUSA SUBRUFA is ‘n varswaterskilpad wat wyd verspreid oor Afrika en
Madagascar voorkom en word beskryf as ‘n Tropiese tot Sub-tropiese spesies. Die manlike en
vroulike voortplantingspatroon van P. subrufa is oor ‘n tydperk van 20 maande bestudeer om vas
te stel of hul voortplanting ooreenstem met ‘n tipiese tropiesie tot sub-tropiese
voortplantingspatroon of ‘n tipiese gematigde-sone voortplantingspatroon. Waterskilpaaie is uit
damme in die Wes-Kaap, Suid-Afnka gevang en bloed- en weefselmonsters is versamel.
Materiaal en data is aangevul deur weefselmonsters van waterskilpaaie wat in
museumversamelings gehuisves word.
Ovarium follikels in P. subrufa wyfies is gemeet en die wyfies se ovanums is
makroskopies gegradeer (onaktief, pre-vitellogenies, vitellogemes, dragtig) en resultate is deur
histologiese snitte van die ovaria en ovidukte bevestig. Wyfies vertoon ‘n sikliese
voortplantingspatroon, met duidelike fases van follikulere groei (vetllogenese), ovulasie en
dragtigheid. Sirkulerende voortplantingshormone in die bloedplasma (estradiol, progesteroon en
testosteroon) is ook geanaliseer met behulp van gevalideerde hormoonspesifieke ELISA
bepalings. Plasma vitellogeen (‘n dooiervoorloper wat in die lewer vervaardig word)
konsentrasies is ook bepaal met ‘n nuut ontwikkelde, universele (spesifiek vir werweldiere)
vitellogeen ELISA (UNIVTG). Seisoenale tydsberekemng van die voortplantingsiklus het
ooreengestem met die van ander varswaterskilpaaie vanuit die Gemagtigde-sone. Vitellogenese
het in die somer begin en duur voort deur die grootste gedeelte van die somer, herfs en winter
gevolg deur ovulasie in die daaropvolgende lente (September - Oktober). Die data ingewin stel
voor d a t/5. subrufa wyfies meestal een broeisel eiers tydens laat lente-somer le (September tot
Januane). Broeiselgrootte het gewissel tussen 7-37 eiers, met die hoeveelheid eiers wat beduidend met moederlike liggaamsgrootte gekorreleer was (r = 0.82, P < 0.001). Plasma
estradiol en vitellogeen konsentrasies het een keer tydens die ovariumsiklus gepiek, en
gewoonlik saamgeval met vroee tot middel vitellogenese in die laat somer. Plasma testosteroon
het dwarsdeur die jaar gevarieer, maar beduidende toenames is gemeet tydens ovulasie en die
paartydperk in die lente. Plasma progesteroon konsentrasies was beduidend hoer tydens
dragtigheid kort voor eierlegging in die middel van die somer (Desember).
In volwasse P. subrufa mannetjies was spermatogenese sterk seisoenaal en het die
voortplantingsiklus ooreengestem met die van ander varswaterskilpadspesies wat in die
gematigde streke voorkom. Na ‘n oorwinteringsperiode (brumasie), volg die panngstydperk
gedurende die lente. ‘n Nuwe spermatogemese siklus het in die somer begin. Maksimale
spermatogeniese aktiwiteit en testis-volume word in die laat somer en vroee herfs bereik.
Testikulere regressie neem in aanvang in die herfs en duur voort tot na paringstyd in die lente.
Tydens testikulere regressie word spermatosoe in die ducti epididymi gestoor. Plasma
testosteroon konsentrasies het in die laat somer en vroee herfs gedurende die testikulere siklus,
spermiogenese (sperm produksie fase), gepiek. Die grootte (omtrek) van die ducti epididymi het
beduidende vanasie dwarsdeur die jaar getoon, terwyl epiteel selhoogtes geen beduidende
seisoenale vanasie getoon het nie. Piek sekretonese aktiwiteit het saamgeval met
spermiogeniese aktiwiteit en hoe vlakke van sirkulerende testosteroon tydens laat somer en vroee
herfs. Testikulere groei het goed gekorreleer met toenemende omgewingstemperatuur,
fotopenode en reenval, terwyl testikulere regressie in herfs met ‘n daling in
omgewingstemperature, fotopenode en reenval gekorrespondeer het. Die vroulike en manlike
voortplantingspatrone was nie goed ge-sinkroniseerd nie, deurdat piek spermatogeniese
aktiwiteit tydens herfs voorgekom het, gedurende die tyd waann meeste wyfies besig was om dooier in groeiende ovarium follikels neer te le. Daarteenoor vertoon die mannetjies testikulere
regressie tydens die pre-ovulatoriese fase en ovulasie penode van die wyfies. Dus toon volwasse
wyfies ‘n tipiese gematigde sone vitellogeniese patron en volwasse mannetjies ‘n tipiese
gematigde sone spermatogeniese patroon.
‘n Verskil in liggaamsgrootte tussen die geslagte is 'n algemene verskynsel by baie diere
en P. subrufa is geen uitsondering me. Daar was wesenlike geslagtelike grootteverskille (SSD)
in P. subrufa en ‘n hoofkomponent analise (PC A) het getoon dat daar beduidende morfometnese
verskille tussen volwasse mannetjies en wyfies was. Deur karapakslengte as 'n maatstaf vir
liggaamsgrootte te gebruik (mede-veranderlike), het volwasse mannetjies, volwasse wyfies en
onvolwassenes beduidend verskil ten opsigte van absolute grootte van hul karapaksbreedte,
karapaksdiepte, plastronlengte, plastronbreedte en kopdiepte. Geen beduidende verskil in
kopbreedte en koplengte in volwasse mannetjies, volwasse wyfies en onvolwassenes is gevind
nie. Derhalwe was volwasse mannetjies groter as volwasse wyfies in sewe van die
liggaamseienskappe wat gemeet is, buiten vir karapaksdiepte waar die wyfies beduidend groter
was. In terme van die voorkoms van ontogenetiese groeipatrone het volwassenes teen ‘n stadiger
tempo as onvolwassenes in plastronlengte toegeneem. Daar was geen beduidende verskil in die
groeitempo van dopbreedte tussen volwassenes en onvolwassenes nie, alhoewel dopdiepte van
volwassenes teen ‘n vinniger tempo gegroei het as die van onvolwassenes. Absolute kopgrootte
van volwassenes het ook teen ‘n vinniger tempo gegroei as in onvolwassenes. Wanneer hierdie
eienskappe as ‘n volledige datastel gebruik word (al agt gemete eienskappe), wil dit voorkom
asof daar geen verskil in groeitempo van volwassenes van die onderskeidelike geslagte is me.
Daar was geen beduidende verskil tussen volwassenes en onvolwassenes, ten opsigte van
dopgrootte nie, alhoewel volwassenes klaarblyklik teen ‘n vinniger tempo in liggaamsgrootte en kopgrootte toeneem. Verskille in liggaamsgrootte en grootte van ander veranderlikes, soos
byvoorbeeld dop- en kop-eienskappe, relatief tot absolute liggaamsgrootte, word aangebied om geslagsdimorfisme in P. subrufa vir die eerste keer te beskryf.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52444 |
| Date | 12 1900 |
| Creators | Strydom, Aliki V. |
| Contributors | Van Wyk, J. H., Leslie, A. J., 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 | English |
| Type | Thesis |
| Format | 156 p. : ill. |
| Rights | Stellenbosch University |
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