Seasonal changes in the ovarian structure ofthe Cape fur seal, Arctocephalus pusillus pusillus

2002 ◽  
Vol 50 (5) ◽  
pp. 491 ◽  
Author(s):  
P. N. Odendaal ◽  
M. N. Bester ◽  
M. van der Merwe ◽  
W. H. Oosthuizen
Keyword(s):  
Corpus Luteum ◽  
Seasonal Changes ◽  
Maximum Size ◽  
Annual Reproductive Cycle ◽  
Histological Changes ◽  
Naked Eye ◽  
Fur Seal ◽  
Ovarian Structure ◽  
Cape Fur Seal ◽  
Follicular Activity

The annual reproductive cycle of the female Cape fur seal (Arctocephalus pusillus pusillus) was described by noting monthly gross changes in ovaries from 159 females, histological changes in 46 females and placental scars in 119 females. The size and weight of an ovary containing a corpus luteum was significantly greater than that of an ovary containing a corpus albicans for most of the year, the latter only approaching, or exceeding the former during the breeding season. Follicular activity initially increased in ovaries containing either a corpus luteum or a corpus albicans; however, it declined in the ovary containing a corpus luteum after implantation, while in that containing a corpus albicans it increased, reaching a maximum in December of 32.0 ± 10.08 follicles, averaging 5.41 ± 0.73 mm. The corpus luteum increased in size following ovulation, attaining a maximum size of 22.28 ± 3.38 mm in August (eight months after ovulation). Thereafter, it gradually decreased in size, generally becoming invisible to the naked eye by 30–32 months after ovulation. Luteal cells increased until seven months after ovulation, reaching a maximum size of 34.36 ± 1.26 μm before regressing, disappearing from the corpus luteum by 18 months after ovulation. Using placental scarring and CA counts in 119 females, a pregnancy rate of 77.4% was calculated, with 6.5% abortions and 16.1% non-implantations making up the remainder.

Spatio-temporal shifts of the dynamic Cape fur seal population in southern Africa, based on aerial censuses (1972-2009)

2012 ◽  
Vol 29 (3) ◽  
pp. 497-524 ◽  
Author(s):  
Steve P. Kirkman ◽  
D. Yemane ◽  
W. H. Oosthuizen ◽  
M. A. Meÿer ◽  
P. G. H. Kotze ◽  
...  
Keyword(s):  
Southern Africa ◽  
Fur Seal ◽  
Seal Population ◽  
Spatio Temporal ◽  
Cape Fur Seal ◽  
Temporal Shifts

Unilateral EEG activation during sleep in the Cape fur seal, Arctocehalus pusillus

1992 ◽  
Vol 143 (1-2) ◽  
pp. 263-266 ◽  
Author(s):  
O.I. Lyamin ◽  
I.S. Chetyrbok
Keyword(s):  
Fur Seal ◽  
Eeg Activation ◽  
Cape Fur Seal

Do inter-colony differences in Cape fur seal foraging behaviour reflect large-scale changes in the northern Benguela ecosystem?

2009 ◽  
Vol 31 (3) ◽  
pp. 399-408 ◽  
Author(s):  
M Skern-Mauritzen ◽  
S P Kirkman ◽  
E Olsen ◽  
A Bjørge ◽  
L Drapeau ◽  
...  
Keyword(s):  
Large Scale ◽  
Foraging Behaviour ◽  
Fur Seal ◽  
Cape Fur Seal

Feel the beat: cape fur seal males encode their arousal state in their bark rate

2021 ◽  
Vol 109 (1) ◽  
Author(s):  
Mathilde Martin ◽  
Tess Gridley ◽  
Simon Harvey Elwen ◽  
Isabelle Charrier
Keyword(s):  
Arousal State ◽  
Fur Seal ◽  
Cape Fur Seal

Pregnancy in a marsupial, the Tasmanian pademelon (Thylogale billardierii)

1999 ◽  
Vol 11 (3) ◽  
pp. 175 ◽  
Author(s):  
R. W. Rose ◽  
J. A. A. Horak ◽  
A. D. Shetewi ◽  
S. M. Jones
Keyword(s):  
Corpus Luteum ◽  
Reproductive Biology ◽  
Plasma Concentrations ◽  
Tammar Wallaby ◽  
Reproductive Organs ◽  
Model Species ◽  
Histological Changes ◽  
Plasma Progesterone ◽  
Embryonic Growth ◽  
Background Data

The Tasmanian pademelon, Thylogale billardierii, is a medium-sized wallaby that adapts well to captivity and, unlike the well-studied tammar wallaby, is capable of breeding all year round. It may, there-fore, be a useful model species for research into the reproductive biology of macropod marsupials. This paper presents necessary background data on histological changes in the reproductive organs and the rate of embryonic growth during gestation in T. billardierii. After Day 4 RPY (removal of young from the pouch) the gravid and non-gravid uteri differ significantly in some histological parameters. The corpus luteum becomes active by Day 6 RPY and is fully developed by Day 14 RPY; it begins to degenerate from Day 19 RPY. Plasma progesterone concentrations through gestation follow a pattern similar to that in the tammar wallaby. There is an early, smaller, peak at Day 5 RPY, with plasma concentrations of progesterone then falling until the larger pre-partum peak occurs several days before birth.

scholarly journals Anatomical and histological changes during the oestrous cycle in the mare

1941 ◽  
Vol 130 (858) ◽  
pp. 1-23 ◽  
Keyword(s):  
Corpus Luteum ◽  
Reproductive Organs ◽  
Oestrous Cycle ◽  
Maximum Diameter ◽  
Histological Changes ◽  
Graafian Follicle ◽  
Heat Period ◽  
To Come ◽  
Time Required ◽  
Dominant Part

The mares chosen for the investigation of the changes in the reproductive organs during the oestrous cycle were kept under observation for some time before they were killed. The duration of the heat period in these animals was 7 days and the length of the dioestrus was 16 days. Ovulation takes place at about a day before the end of oestrus. The size of the ovary during the oestrous cycle is chiefly influenced by the growing Graafian follicle. The number of follicles present at different stages varies greatly. The numerous small follicles present at the beginning of oestrus disappear later in the cycle; it is suggested that this may be due to the lack of follicle-stimulating hormone. The colour of the corpus luteum varies greatly at different stages of the cycle. The rupture of the follicle is associated with some bleeding. The active stage of the corpus luteum is very short, and the maximum diameter of the corpus luteum seems to be always below that of the Graafian follicle. The greater development of the Graafian follicle, with its secretion of oestrin, in the mare leads to its playing a more important role than in the cow and the sow, in which species the corpus luteum takes a m ore dominant part in the cycle. It appears that the much longer oestrus in the mare than in the cow is due to the longer time required by the follicle to come to the surface and to break through. This is probably due to the peculiar structure of the ovary in the mare, since the ovulation, which is spontaneous, can only occur in the small ovulation fossa. No pronounced secretion stage occurs during oestrus in the Fallopian tubes.

scholarly journals Ammonia emissions from a Cape fur seal colony, Cape Cross, Namibia

2006 ◽  
Vol 33 (3) ◽  
Author(s):  
M. R. Theobald ◽  
P. D. Crittenden ◽  
A. P. Hunt ◽  
Y. S. Tang ◽  
U. Dragosits ◽  
...  
Keyword(s):  
Ammonia Emissions ◽  
Fur Seal ◽  
Cape Fur Seal

scholarly journals Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys

2009 ◽  
Vol 6 (1) ◽  
pp. 48-50 ◽  
Author(s):  
Alta De Vos ◽  
M. Justin O'Riain
Keyword(s):  
Experimental Evidence ◽  
Predation Risk ◽  
Prey Species ◽  
Group Formation ◽  
Predator Prey ◽  
Selfish Herd ◽  
Fur Seal ◽  
Cape Fur Seal ◽  
Shark Attacks ◽  
Proportional Reduction

Many animals respond to predation risk by forming groups. Evolutionary explanations for group formation in previously ungrouped, but loosely associated prey have typically evoked the selfish herd hypothesis. However, despite over 600 studies across a diverse array of taxa, the critical assumptions of this hypothesis have remained collectively untested, owing to several confounding problems in real predator–prey systems. To solve this, we manipulated the domains of danger of Cape fur seal ( Arctocephalus pusillus pusillus ) decoys to provide evidence that a selfish reduction in a seals' domain of danger results in a proportional reduction in its predation risk from ambush shark attacks. This behaviour confers a survival advantage to individual seals within a group and explains the evolution of selfish herds in a prey species. These findings empirically elevate Hamilton's selfish herd hypothesis to more than a ‘theoretical curiosity’.

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