Endocrine correlates of hibernation-independent gonadal recrudescence and the limited late-winter breeding season in woodchucks,Marmota monax

After 15 wk in a short photoperiod (10 h of light/day), adult male voles weighed 25% less and consumed 33% less food than did voles in a long photoperiod (14 h light/day). Neither body weight nor food intake differed among long- and short-day castrated voles. After 19 wk, castrated long-day voles weighed less than did intact animals. Voles reduced their body weight during the first 15 wk in the short photoperiod and increased their body mass during the succeeding 15 wk. Body mass of short-day voles was positively correlated with combined testes weight. Voles in the short photoperiod collected less nesting material than did their long-day counterparts at week 31. Pelage characteristics at week 32 were not affected by castration or by photoperiod. We conclude that the decreased body mass of male voles during the late summer, fall, and early winter reflects a decrease in circulating levels of testicular hormones; gonadal recrudescence and increased circulating androgen levels are in part responsible for the subsequent seasonal increase in body weight. Part of the increased body mass in late winter in field populations or in laboratory voles after 15 wk in the short photoperiod is independent of the resumption of gonadal activity. Fluctuations in neural and endocrine processes, rather than availability of food, are the principal factors underlying seasonal changes in energy balance.

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Pituitary gonadotropin contents and ultrastructure of the gonadotrops in the African catfish Clarias gariepinus during the annual cycle in a natural habitat

Canadian Journal of Zoology ◽

10.1139/z86-259 ◽

1986 ◽

Vol 64 (8) ◽

pp. 1718-1726 ◽

Cited By ~ 22

Author(s):

J. Peute ◽

M. A. Zandbergen ◽

H. J. Th. Goos ◽

R. de Leeuw ◽

R. Pinkas ◽

...

Keyword(s):

Reproductive Cycle ◽

Secretory Granules ◽

Natural Habitat ◽

Clarias Gariepinus ◽

Early Spring ◽

Late Winter ◽

Breeding Period ◽

African Catfish ◽

Pituitary Gonadotropin ◽

Gonadal Recrudescence

Over a period of 1 year, male and female specimens of a natural population of African catfish, Clarias gariepinus, were collected monthly at locations in northern Israel. Both the ultrastructural appearance of the gonadotrops and the pituitary gonadotropin content in males and females showed cyclical changes, which paralleled alterations in the reproductive cycle. In summer, during the breeding period, the gonadotrops were large and fully granulated, and pituitary gonadotropin reached maximum levels. After spawning, the resting period begins, with an increasing number of fusion products of secretory granules and globules in the gonadotrops, probably indicating a breakdown of hormone storage. This was followed by the appearance of residual bodies, cell shrinkage, and a considerable drop in pituitary gonadotropin content. In late winter and early spring, during gonadal recrudescence, the gonadotrops redeveloped, i.e., they increased in size and granulation, and at the same time the pituitary gonadotropin content augmented. This reproductive cycle will permit induced spawning and artificial propagation of African catfish from March till September. However, keeping the catfish at favourable feeding and temperature conditions may also permit the gonadotrops to produce gonadotropin continuously, thus providing the possibility of complete gametogenesis and of obtaining viable eggs and healthy larvae throughout the year.

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Reproduction in Sminthopsis-Longicaudata (Marsupialia, Dasyuridae) - Laboratory Observations

Wildlife Research ◽

10.1071/wr9860007 ◽

1986 ◽

Vol 13 (1) ◽

pp. 7 ◽

Cited By ~ 5

Author(s):

PA Woolley ◽

A Valente

Keyword(s):

Endangered Species ◽

Breeding Season ◽

Early Summer ◽

Oestrous Cycle ◽

Gestation Period ◽

Late Winter ◽

Breeding Condition ◽

Males And Females ◽

The Mean

Observations on the pattern of reproduction in Sminthopsis longicaudata, at present considered to be an endangered species, are presented. S. longicaudata is polyoestrous and in the laboratory females are in breeding condition from late winter (August) to early summer (December). They enter oestrus up to four times during the breeding season. Two litters were born 17 and 19 days post-mating, but the gestation period may be less than 15 days. The mean length of the oestrous cycle is 34.4 days. Both males and females may be able to breed in more than one season.

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Seasonal changes in serum leptin, food intake, and body weight in photoentrained woodchucks

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.3.r951 ◽

2001 ◽

Vol 281 (3) ◽

pp. R951-R959 ◽

Cited By ~ 51

Author(s):

P. Concannon ◽

K. Levac ◽

R. Rawson ◽

B. Tennant ◽

A. Bensadoun

Keyword(s):

Body Weight ◽

Food Intake ◽

Hormonal Regulation ◽

Serum Testosterone ◽

Late Spring ◽

Late Winter ◽

Serum Concentrations ◽

Serum Leptin ◽

Marmota Monax ◽

Rate Of Decline

Male woodchucks ( Marmota monax) were maintained in northern vs. southern hemisphere photoperiods, provided feed and water ad libitum, and evaluated every 2 wk for 23 mo for body weight, absolute and relative food intake, body temperature, serum testosterone, and serum concentrations of leptin measured using an anti-mouse leptin enzyme-linked immunoassay. During late spring and summer, body weight increased 56 ± 4% above winter nadirs, and during the autumn and early winter weights decreased 27 to 43% below midsummer maxima. Serum leptin initially increased during increases in body weight, in the late spring, reached peak values (490 ± 32 pg/ml) in summer during the initial decline in body weight, and later decreased along with body weight to reach basal values (20 ± 5 pg/ml) in late winter. Spontaneous declines in food intakes in summer began 2–6 wk before resulting declines in body weight and occurred during increases in leptin >100 pg/ml. The rate of decline in food intakes was greatest when serum leptin was at or near peak values. Food intake increased in late winter when leptin was low and 7–10 wk before resulting increases in body weight. Testis recrudescence occurred when leptin was declining to near basal levels. The results suggest that leptin is involved in the hormonal regulation of the circannual cycle in the drive for voluntary food intake in this species.

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Eastern Black Rail (Laterallus jamaicensis jamaicensis) Home Range and Habitat Use in Late Winter and Early Breeding Season in Coastal Texas, USA

Waterbirds ◽

10.1675/063.044.0209 ◽

2021 ◽

Vol 44 (2) ◽

Author(s):

Amanda A. Haverland ◽

M. Clay Green ◽

Floyd Weckerly ◽

Jennifer K. Wilson

Keyword(s):

Home Range ◽

Habitat Use ◽

Breeding Season ◽

Late Winter ◽

Black Rail

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Reproduction , Spawning and Development of the Starfish Patiriella exigua (Lamarck) (Asteroidea : Asterinidae) and Some Comparisons with P. calcar (Lamarck)

Marine and Freshwater Research ◽

10.1071/mf9780045 ◽

1978 ◽

Vol 29 (1) ◽

pp. 45 ◽

Cited By ~ 26

Author(s):

C Lawson-Kerr ◽

DT Anderson

Keyword(s):

Breeding Season ◽

Late Spring ◽

Late Winter ◽

Egg Mass ◽

Lecithotrophic Larva

P. exigua adults are mature throughout the year. The species can breed in any month of the year, though spawning is most active in the late winter and spring. P. calcar has a definite breeding season in the late spring and summer. P. exigua lays an egg mass through oral gonopores. The 400-�m eggs develop directly, through a yolky brachiolaria stage to a juvenile star, before leaving the egg mass at 22-23 days. P. calcar, with eggs of similar size laid through oral gonopores, has a planktonic lecithotrophic larva. The development of P. exigua is compared with that of other yolky asteroid embryos. Modes of development in the genus Patiriella are discussed.

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Conditional daily and seasonal movement strategies of male Columbia black-tailed deer (Odocoileus hemionus columbianus)

Canadian Journal of Zoology ◽

10.1139/cjz-2013-0034 ◽

2013 ◽

Vol 91 (10) ◽

pp. 679-688 ◽

Cited By ~ 8

Author(s):

E.S. Long ◽

T.C. Jacobsen ◽

B.J. Nelson ◽

K.M.M. Steensma

Keyword(s):

Breeding Season ◽

Odocoileus Hemionus ◽

Time Of Day ◽

Resource Acquisition ◽

Late Winter ◽

Odocoileus Hemionus Columbianus ◽

Seasonal Movement ◽

Trade Offs ◽

Movement Strategies ◽

Diel Movement

Animals move to maximize fitness via resource acquisition, predator avoidance, thermoregulation, or mate access. Variations in movement strategies among and within populations often reflect habitat- or demographic-specific variations in fitness trade-offs. To examine these conditional movement strategies, we modeled seasonal and diel movement patterns of radio-collared adult male Columbia black-tailed deer (Odocoileus hemionus columbianus (Richardson, 1829)) on a temperate, predator-free island. Linear 10 h displacement and home-range areas reached annual maxima during autumn and minima during late winter, corresponding with known dates for breeding season and lowest quality forage, respectively. For all males in all years, initiation of increased movements began during spring and again, abruptly, in late September, immediately prior to peak breeding season. Larger antlered males continued increased movements longer into December, suggesting increased breeding effort relative to smaller antlered males. Time of day predicted movements during all seasons; however, we observed no strong evidence of the crepuscular or nocturnal movement bias typically noted in deer, likely relating to the lack of predators in our study area. In this way, male black-tailed deer adopted conditional, seasonally specific movement strategies to balance fitness trade-offs in resource acquisition, thermoregulation, and mate access.

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The European Rabbit in South- Western Australia II. Reproduction

Wildlife Research ◽

10.1071/wr9850197 ◽

1985 ◽

Vol 12 (2) ◽

pp. 197 ◽

Cited By ~ 12

Author(s):

SH Wheeler ◽

DR King

Keyword(s):

Breeding Season ◽

Western Australia ◽

Coastal Areas ◽

European Rabbit ◽

Female Reproduction ◽

Early Peak ◽

Study Sites ◽

Second Peak ◽

Winter Breeding ◽

Coastal District

'The reproduction of the European rabbit, Oryctolagus cuniculus (L.), at two intensive study sites in south-western Australia is compared with reproductive data from rabbits taken throughout the coastal and inland districts of the south-west region. South-western Australia has hot, arid summers and cool wet winters. Rabbit breeding in the region is characteristic of that in Mediterranean climates, with a winter breeding season which begins when pastures germinate with the initial winter rainfall (April-May) and ceases when the pastures dry out at the end of the year. Unseasonal cyclonic rain can promote pasture growth in summer, leading to limited breeding. At all times of year there were some fertile males, with fewest at the height of summer, followed by an increase before the winter breeding season. Near the coast, male fertility increased more rapidly than further inland. At our two study sites at Cape Naturaliste (on the coast) and Chidlow (55 km inland) the pattern was similar to that in the coastal district. Production of kittens was greater near the coast than further inland, because near the coast there was a high early peak in incidence of pregnancy, a second peak late in the year, and litters remained large throughout the breeding season. In the inland district, the early incidence of pregnancy was lower, there was no second peak, and litter sizes fell at the end of the year. Female reproduction at Cape Naturaliste was typical of that in the coastal district, but that at Chidlow was typical of the inland. The second peak of pregnancy at Cape Naturaliste was due to intensive breeding by subadults born earlier in the year. The differences in female reproduction and productivity between the coastal and inland districts are probably because pasture growth begins earlier and is better in the more fertile coastal areas than in the inland. That nutrition is better for rabbits in the coastal areas than in the inland is reflected in higher growth rates of kittens at Cape Naturaliste than at Chidlow. It is postulated, on the basis of the literature and the results of our studies, that the factor which determines whether rabbits will breed is the presence of growing vegetation, and that the intensity of breeding is influenced by a seasonal cycle in fertility.

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