Seasonal Reproduction in Musky Rat-kangaroos, Hypsiprymnodon moschatus: a Response to Changes in Resource Availability

1997 ◽  
Vol 24 (5) ◽  
pp. 561 ◽  
Author(s):  
Andrew J. Dennis ◽  
Helene Marsh
Keyword(s):  
Resource Availability ◽  
Seasonal Changes ◽  
Reproductive Output ◽  
Selective Pressure ◽  
Seasonal Pattern ◽  
Seasonal Reproduction ◽  
Reproductive Pattern ◽  
High Fecundity ◽  
Male And Female ◽  
Breeding Seasons

Musky rat-kangaroos had a seasonal reproductive pattern. Males underwent a dramatic testicular expansion in October and the testes remained enlarged until April, when they reduced in size again. Females carried 1–3 pouch young from around March until October; juveniles were suckled until late December. Two primary food resources, fruits and litter fauna, underwent regular seasonal changes in abundance. The availability of fruits fluctuated to a greater degree than did that of litter fauna, both within and between years, which probably constituted the main selective pressure for a seasonal pattern of reproduction and high fecundity relative to most other macropodoids. Variation in the availability of fruits between years correlated with changes in the reproductive output of both male and female musky rat-kangaroos during breeding seasons.

Effects of gonadectomy on seasonal changes in plasma LH and prolactin concentrations in male and female starlings (Sturnus vulgaris)

1984 ◽  
Vol 100 (2) ◽  
pp. 213-218 ◽  
Author(s):  
A. Dawson ◽  
A. R. Goldsmith
Keyword(s):  
Seasonal Changes ◽  
Seasonal Pattern ◽  
Maximum Size ◽  
Sturnus Vulgaris ◽  
Prolactin Secretion ◽  
Testis Size ◽  
Gonadal Steroid ◽  
Male And Female ◽  
Males And Females

ABSTRACT Intact and gonadectomized male and female starlings (Sturnus vulgaris) were held in outdoor aviaries for 1 year. Blood samples were taken frequently and assayed for LH and prolactin, and intact males were laparotomized to determine testis size. Changes in testis size in intact males were similar to those in wild starlings with maximum size during April. Hormone levels in intact males and females also followed a similar pattern to those in wild birds although absolute levels were somewhat lower. Levels of LH increased during spring, were highest in early May and then declined rapidly as birds became photorefractory. Prolactin levels did not begin to increase until April, reached a peak in late May and then declined. In gonadectomized males and females, high levels of LH were maintained throughout the early part of the year when birds were photosensitive, but declined rapidly as they became photorefractory. This occurred at the same time as in intact birds. During photorefractoriness, LH levels in gonadectomized birds were similar to those in intact birds. Prolactin showed the same seasonal pattern in gonadectomized birds as that in intact birds. These results demonstrate that gonadal steroid feedback is unimportant in initiating and maintaining photorefractoriness and confirm that increased prolactin secretion coincides with the onset of photorefractoriness. J. Endocr. (1984) 100, 213–218

Life history and population dynamics of the exotic snail Potamopyrgus antipodarum (Prosobranchia : Hydrobiidae) in Lake Purrumbete, Victoria, Australia

1998 ◽  
Vol 49 (1) ◽  
pp. 73 ◽  
Author(s):  
E. S. G. Schreiber ◽  
A. Glaister ◽  
G. P. Quinn ◽  
P. S. Lake
Keyword(s):  
Population Dynamics ◽  
Reproductive Output ◽  
Size Structure ◽  
Seasonal Pattern ◽  
Potamopyrgus Antipodarum ◽  
Seasonal Patterns ◽  
High Fecundity ◽  
Successful Invader ◽  
Density Population ◽  
Different Levels

The density, population size-structure, and fecundity of the exotic snail Potamopyrgus antipodarum are described, for a period of two years, on two shores subject to different levels of disturbance in Lake Purrumbete. The population dynamics of Potamopyrgus antipodarum showed the same seasonal pattern in the numbers of embryos carried per individual female in both years, but seasonal patterns in density and potential reproductive output of the population differed between shores. Densities of Potamopyrgus antipodarum were high, with a trend for highest densities to occur in spring and summer. The population consisted almost entirely of females, which is indicative of a parthenogenic mode of reproduction. Fecundity was high, with the number of embryos carried per female peaking in spring. In summer, the population was dominated by small individuals, but some small snails were present at all times of the year. Potamopyrgus antipodarum was found to be a very successful invader of Lake Purrumbete, with high densities, high fecundity, parthenogenesis and the presence of embryos throughout the year contributing to this success.

Seasonal reproductive patterns and effectiveness as teasers (ram effect) of Corriedale and Milchschaf rams

2012 ◽  
Vol 52 (11) ◽  
pp. 1036 ◽  
Author(s):  
R. Ungerfeld
Keyword(s):  
Sexual Behaviour ◽  
Seasonal Changes ◽  
Minimum Distance ◽  
Seasonal Pattern ◽  
Seasonal Patterns ◽  
Reproductive Pattern ◽  
Reproductive Patterns ◽  
Scrotal Circumference ◽  
Semen Characteristics ◽  
Ram Effect

The first objective of this study was to compare the seasonal reproductive pattern of Corriedale and Milchschaf rams. Because seasonal patterns were similar, a second objective was to compare the effectiveness of rams from both breeds to induce oestrus in seasonally anoestrous Corriedale ewes using the ram effect. In the first experiment, the seasonal changes of bodyweight, scrotal circumference, testosterone concentrations, sexual behaviour towards oestrous ewes (ano-genital sniffing, lateral approaches, flehmen, mount attempts, mounts, and copulation), and semen characteristics (total spermatozoa in the ejaculate, mass motility, and percentage of alive and normal spermatozoa) were recorded during 13 months in five Corriedale and seven Milchschaf rams. All recorded variables changed through the year, with maximum reproductive patterns occurring in summer and autumn. Milchschaf rams were heavier than Corriedale rams, but no difference was observed in their reproductive patterns. Experiment 2 was performed during the non-breeding season with 169 Corriedale and Polwarth mulitparous ewes. All ewes were isolated from the rams so that they could not see, hear or smell them (minimum distance: 1000 m) from Day –40. They were primed over 8 days with an intravaginal sponge impregnated with 50 mg of medroxiprogesterone. Four Corriedale rams were introduced to 83 ewes, and four Milchschaf rams to the remaining 86 ewes at sponge withdrawal, and oestrus was recorded for 5 days. On Day 5, no ewe of the group bred with Milchschaf rams was marked. By contrast, 46 out of 83 (55.4%) of the ewes bred with Corriedale rams were marked (P < 0.0001). It was concluded that reproductive seasonal pattern of Corriedale and Milchschaf rams, including scrotal circumference, testosterone concentrations, sexual behaviour and semen characteristics, was similar. However, Corriedale rams were more effective than Milchschaf rams in inducing oestrus in anoestrus ewes (the ram effect).

Seasonal prolactin secretion and its role in seasonal reproduction: a review

1992 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
JD Curlewis
Keyword(s):  
Seasonal Change ◽  
Seasonal Changes ◽  
Seasonal Pattern ◽  
Preliminary Evidence ◽  
Prolactin Secretion ◽  
Seasonal Reproduction ◽  
Target Area ◽  
Gonadotrophin Secretion ◽  
Neuroendocrine Mechanisms ◽  
Prolactin Synthesis

The majority of seasonally breeding mammals show a seasonal pattern of prolactin secretion with peak concentrations in spring or summer and a nadir in autumn or winter. Photoperiod influences prolactin secretion via its effects on the secretion of the pineal hormone melatonin. Preliminary evidence suggests that the effects of melatonin on both prolactin and gonadotrophin secretion are via a common target area, possibly within the anterior hypothalamus, and that differences in response to photoperiod may be due to differences in the processing and/or interpretation of the melatonin signal. In contrast to seasonal gonadotrophin secretion, the seasonal changes in prolactin are not due to changes in the sensitivity of a feedback loop and so must be due to direct effects on the hypothalamic pathways that control prolactin secretion. Little else can be said with confidence about the neuroendocrine mechanisms that lead to the seasonal changes in prolactin secretion. Dopamine and noradrenaline turnover in the arcuate nucleus and median eminence decrease under short daylength. If catecholamine turnover in these structures is positively correlated with catecholamine concentrations in the long or short hypophysial portal vessels, it is unlikely that the decrease in prolactin concentration in winter is due to the effects of increased concentrations of dopamine or noradrenaline in the portal vessels. There is, however, evidence for increased pituitary sensitivity to dopamine under short daylength, so increased dopamine concentrations may not be required for suppression of prolactin secretion at this time. In addition to the diminished secretion of prolactin under short daylength, rate of prolactin synthesis and pituitary content of prolactin also decline although the mechanisms that regulate these changes are poorly understood. Although all seasonal breeders show a seasonal change in prolactin secretion, there are continuously breeding species in which prolactin secretion is also under photoperiodic control. It is likely therefore that a seasonal pattern of prolactin secretion is only evidence of neuroendocrine sensitivity to changing photoperiod. Depending upon the species, this sensitivity to the seasonal changes in daylength may or may not be accompanied by seasonal changes in a biological endpoint such as seasonal reproduction or indeed other adaptations. Whether the seasonal change in prolactin secretion is an endocrine mediator of such adaptations remains in contention. Certainly in some species this signal does have a role in reproduction. For example, in species with an obligate seasonal embryonic diapause, the seasonal increase in prolactin can act as a luteotrophin (mink and western spotted skunk) or luteostatin (Bennett's and tammar wallabies.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Seasonal feeding plasticity can facilitate coexistence of dominant omnivores in Neotropical streams

2021 ◽  
Author(s):  
Mayara P. Neves ◽  
Pavel Kratina ◽  
Rosilene L. Delariva ◽  
J. Iwan Jones ◽  
Clarice B. Fialho
Keyword(s):  
Seasonal Variation ◽  
Fish Species ◽  
Resource Availability ◽  
Seasonal Changes ◽  
Dry Season ◽  
Diet Overlap ◽  
Isotopic Niche ◽  
Neotropical Streams ◽  
Feeding Plasticity ◽  
The Impact

AbstractCoexistence of ecomorphologically similar species in diverse Neotropical ecosystems has been a focus of long-term debate among ecologists and evolutionary biologists. Such coexistence can be promoted by trophic plasticity and seasonal changes in omnivorous feeding. We combined stomach content and stable isotope analyses to determine how seasonal variation in resource availability influences the consumption and assimilation of resources by two syntopic fish species, Psalidodon aff. gymnodontus and P. bifasciatus, in the Lower Iguaçu basin. We also tested the impact of seasonality on trophic niche breadth and diet overlap of these two dominant omnivores. Seasonal changes in resource availability strongly influenced the consumption and assimilation of resources by the two fish species. Both species exhibited high levels of omnivory, characterized by high diversity of allochthonous resources in the wet season. Terrestrial invertebrates were the main component of diet during this season. However, in the dry season, both species reduced their isotopic niches, indicating diet specialization. High diet overlap was observed in both seasons, but the isotopic niche overlap was smaller in the dry season. Substantial reduction in the isotopic niche of P. bifascistus and a shift toward aquatic invertebrates can facilitate coexistence during this season of resource shortage. Feeding plasticity allows omnivorous fish to adjust their trophic niches according to seasonality, promoting the exploitation of different resources during periods of greater resource diversity. This seasonal variation could be an important mechanism that contributes to the resource partitioning and coexistence of dominant omnivores in Neotropical streams.

Differential nectar production between male and female flowers in a wild cucurbit: Cucurbita maxima ssp. andreana (Cucurbitaceae)

2002 ◽  
Vol 80 (11) ◽  
pp. 1203-1208 ◽  
Author(s):  
Lorena Ashworth ◽  
Leonardo Galetto
Keyword(s):  
Reproductive Output ◽  
Male Flower ◽  
Female Flower ◽  
Cucurbita Maxima ◽  
Nectar Production ◽  
Male And Female ◽  
Nectar Sugar Composition ◽  
Nectar Sugar ◽  
Male Flowers ◽  
Female Flowers

In dioecious and monoecious plants that depend on animal vectors for reproduction, pollinators have to be attracted to male and female flowers for pollination to be effective. In the monoecious Cucurbita maxima ssp. andreana, male flowers are produced in greater quantity, are spatially more exposed to pollinators and offer pollen in addition to nectar as floral rewards. Nectar traits were compared between male and female flowers to determine any differences in the characteristics of the main reward offered to pollinators. Nectar chemical composition and sugar proportions were similar between flower types. Total nectar sugar production per female flower was threefold higher than per male flower, and nectar removal did not have any effect on total nectar production in both flower morphs. Pollinators reduced nectar standing crops to similar and very scarce amounts in both flower types. Results indicate indirectly that pollinators are consuming more nectar from female flowers, suggesting that the higher nectar production in female flowers may be a reward-based strategy to achieve the high female reproductive output observed in this species.Key words: Cucurbitaceae, Cucurbita maxima ssp. andreana, nectar production, nectar sugar composition, removal effects, standing crop.

scholarly journals Reproductive phenology in a riparian rainforest in the south of Santa Catarina state, Brazil

2013 ◽  
Vol 85 (4) ◽  
pp. 1449-1460 ◽  
Author(s):  
MAINARA F. CASCAES ◽  
VANILDE CITADINI-ZANETTE ◽  
BIRGIT HARTER-MARQUES
Keyword(s):  
Plant Species ◽  
Resource Availability ◽  
Forest Ecosystems ◽  
Seasonal Pattern ◽  
Riparian Forests ◽  
Reproductive Phenology ◽  
Environmental Restoration ◽  
Fruit Availability ◽  
One Year ◽  
Riparian Plant

Phenological studies assist in forest ecosystems comprehension and evaluation of resource availability for wildlife, as well as in improving the understanding of relationships between plants and their pollinators and dispersers. This study aims to describe the reproductive phenophases of riparian plant species and correlate them with climatic variables. The reproductive phenology was analyzed biweekly throughout one year, recording the absence or presence of flowers/fruits. The flowering phenophase occurred throughout the year, with an increase in number of species in blossom in October, November, and December. The flowering peak of the community was observed in November. The fruiting phenophase also occurred throughout the year and showed an increase of species fruiting in June with a slight decrease in August and September. The data obtained in this study, when compared with other studies in different Atlantic Rainforest areas, indicates a seasonal pattern for the flowering phenophase and a variation in fruit availability throughout the year as well as in the fruiting peaks. Therefore, studies that observe flowering and fruiting events in loco are of main importance because they provide information on reproductive seasons of species for use in environmental restoration projects and thus alleviate the situation of degradation of riparian forests.

Female and male costs of reproduction must be equal in dioecious Cape plant genus Leucadendron (Proteaceae)

2019 ◽  
Vol 67 (7) ◽  
pp. 517
Author(s):  
Jeremy J. Midgley ◽  
Adam G. West ◽  
Michael D. Cramer
Keyword(s):  
Sexual Dimorphism ◽  
Reproductive Output ◽  
Sex Ratios ◽  
Reproductive Allocation ◽  
Costs Of Reproduction ◽  
Male And Female

The Cape Leucadendron genus is dioecious, with extreme vegetative dimorphism displayed in some species – females having much larger leaves and fewer branches than males – whereas other species are monomorphic. Leucadendron is ecologically diverse, with some species with canopy stored seeds (serotiny) and others with soil stored seeds. These features mean that the Cape Leucadendron is an ideal genus to study the costs of reproduction for the different sexes in plants, and to determine whether vegetative dimorphism could be due to unequal costs. Here we use the unique aspects of the fire-prone Cape environment in which leucadendrons occur to show that the costs of sex must be equal between the sexes. Leucadendron populations are single aged because they only recruit after fires that kill all adults. Therefore, because the sexes have the same lifespans, they must have the same lifetime extent of vegetative versus reproductive allocation. Also, ecologically similar hermaphrodite Proteaceae co-exist with dioecious taxa. To co-occur, dioecious and hermaphrodite taxa must have the same mean post-fire fitness. This implies that dioecious females must have double the reproductive output that a co-occurring hermaphrodite has. This is only possible if the costs of reproduction are the same for the sexes and that the sexes use the same resources for reproduction. Finally, because males and female co-occur, they must be competitively equivalent to maintain natal sex ratios. These three factors suggest male and female allocate equivalently and therefore that vegetative sexual dimorphism is unlikely to be due to differences in allocation.

scholarly journals Fish assemblages in a tidal flat

2003 ◽  
Vol 46 (2) ◽  
pp. 233-242 ◽  
Author(s):  
Ana Lúcia Vendel ◽  
Sabine Granado Lopes ◽  
César Santos ◽  
Henry Louis Spach
Keyword(s):  
Cluster Analysis ◽  
Community Structure ◽  
Tidal Flat ◽  
Seasonal Changes ◽  
Dominant Species ◽  
Fish Assemblages ◽  
Seasonal Pattern ◽  
Abundant Species ◽  
Structure Index ◽  
Total Capture

Studies were carried out on fish assemblages in a tidal flat. Samples were obtained monthly at low tide of the half moon in the tidal flat of Paranaguá Bay, Brazil, with two seine nets, one with a 1 mm mesh, 30 m in length and 3 m in height and another with a 10 mm mesh, 65 m in length and 2 m in height. A total of 8,890 fish were captured, comprising 24 families and 53 species. The most abundant species were Harengula clupeola and Atherinella brasiliensis, which represented 63.4% of the total, capture. A seasonal tendency was observed in the abundance of fishes, with less fishes being captured during winter and part of spring. The number of species showed a seasonal pattern, with the gradual decrease through winter and a marked increase in summer. The community structure index indicated seasonal changes in the assemblage. The faunistic similarities between months separated the 12 months into four major groups. The seasonal pattern was apparent in the numerically dominant species and the Cluster Analysis revealed five main groups.

scholarly journals Seasonal Changes in Sleep Duration in African American and African College Students Living In Washington, D.C.

2007 ◽  
Vol 7 ◽  
pp. 880-887 ◽  
Author(s):  
Janna Volkov ◽  
Kelly J. Rohan ◽  
Samina M. Yousufi ◽  
Minh-Chau Nguyen ◽  
Michael A. Jackson ◽  
...  
Keyword(s):  
College Students ◽  
African American ◽  
Sleep Duration ◽  
Seasonal Changes ◽  
African American Students ◽  
Seasonal Affective Disorder ◽  
Seasonal Pattern ◽  
Diagnosis Group ◽  
American Students ◽  
Sleep Length

Duration of nocturnal melatonin secretion, a marker of “biological night” that relates to sleep duration, is longer in winter than in summer in patients with seasonal affective disorder (SAD), but not in healthy controls. In this study of African and African American college students, we hypothesized that students who met criteria for winter SAD or subsyndromal SAD (S-SAD) would report sleeping longer in winter than in summer. In addition, based on our previous observation that Africans report more “problems” with change in seasons than African Americans, we expected that the seasonal changes in sleep duration would be greater in African students than in African American students. Based on Seasonal Pattern Assessment Questionnaire (SPAQ) responses, African American and African college students in Washington, D.C. (N = 575) were grouped into a winter SAD/S-SAD group or a no winter diagnosis group, and winter and summer sleep length were determined. We conducted a 2 (season) × 2 (sex) × 2 (ethnicity) × 2 (winter diagnosis group) ANCOVA on reported sleep duration, controlling for age. Contrary to our hypothesis, we found that African and African American students with winter SAD/S-SAD report sleeping longer in the summer than in the winter. No differences in seasonality of sleep were found between African and African American students. Students with winter SAD or S-SAD may need to sacrifice sleep duration in the winter, when their academic functioning/efficiency may be impaired by syndromal or subsyndromal depression, in order to meet seasonally increased academic demands.

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