Seasonal Variation In Reproduction Research Articles

Seasonal Variation in Reproduction of Horseshoe Crabs (Limulus polyphemus) from the Gulf Coast of Florida.

AbstractThe timing of reproduction is often governed by environmental variables, such as temperature or rainfall. Understanding how environmental variables affect mating dynamics is necessary to predict how systems and populations may adapt to changing environmental conditions and is crucial for management of threatened species. The American horseshoe crab (Limulus polyphemus) ranges from the Yucatan to Maine in distinct populations that differ in their timing of reproduction; while most populations have only one breeding period during the spring, some southern populations have two breeding periods. Here we discuss seasonal patterns of reproduction in a Florida Gulf coast population where horseshoe crabs have two periods of breeding: one in the spring and another in the fall. We used environmental measurements, spawning surveys, mark-recapture, and measurements of adult traits and spawning behavior to compare reproductive parameters between the two spawning seasons over three years. We then evaluated whether environmental conditions affect fall and spring horseshoe crab nesting patterns similarly and whether fall and spring horseshoe crabs should be considered two separate populations. We found significant differences in environmental conditions across seasons and in a wide variety of horseshoe crab traits and nesting parameters. Furthermore, environmental conditions affected nesting behaviors of fall and spring horseshoe crabs differently. However, some individuals spawn during both seasons, suggesting that trait differences may be attributable to environmental effects during development or seasonal plasticity, rather than genetic differences, although further study is necessary. Finally, our results suggest that management practices should be tailored to each population, because environmental conditions may have different effects even on genetically similar groups.

High temperatures result in smaller nurseries which lower reproduction of pollinators and parasites in a brood site pollination mutualism.

In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3–5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig–pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change.

Testosterone production and spermatogenesis in free-ranging Eurasian lynx (Lynx lynx) throughout the year

Seasonal variation in reproduction is common in mammals as an adaptation to annual changes in the habitat. In lynx, male reproduction activity is of special interest because female lynxes are monoestric with an unusual narrow (about 1 month) breeding season. In Eurasian lynx, mating occurs between January and April depending on the latitude. To characterize the seasonal pattern of sperm and testosterone production in free-ranging Eurasian lynxes, long-term frozen-stored testis material obtained postmortem from 74 hunted or road-killed lynxes in Sweden was used to analyze annual changes in testis mass, testicular testosterone content, and spermatogenetic activity. Values of most gonadal parameters obtained in subadult lynxes were significantly different from the values observed in adult males. In adult lynxes, a moderate annual fluctuation of gonadal parameters was found which was most profound for testis weight and testicular testosterone concentration reaching highest values in March (median of 2.18 g and 2.67 μg/g tissue respectively). Grouping the data of pre-/breeding (January–April) and postbreeding season (May–September) revealed significant changes in testis weight and testosterone concentration. The relative spermatogenetic activity remained high in postbreeding testes. However, net sperm production decreased according to reduction of testis mass and a tendency to lower cauda epididymal sperm numbers in the postbreeding period was observed. Our results demonstrate that it is possible to analyze the gonadal activity of frozen testis/epididymis tissue postmortem and that male Eurasian lynxes show—opposite to the females—only moderate seasonal changes in their reproductive capacity.

Melatonin‐Dependent Timing of Seasonal Reproduction by the Pars Tuberalis: Pivotal Roles for Long Daylengths and Thyroid Hormones

Most mammals living at temperate latitudes exhibit marked seasonal variations in reproduction. In long-lived species, it is assumed that timely physiological alternations between a breeding season and a period of sexual rest depend upon the ability of day length (photoperiod) to synchronise an endogenous timing mechanism called the circannual clock. The sheep has been extensively used to characterise the time-measurement mechanisms of seasonal reproduction. Melatonin, secreted only during the night, acts as the endocrine transducer of the photoperiodic message. The present review is concerned with the endocrine mechanisms of seasonal reproduction in sheep and the evidence that long day length and thyroid hormones are mandatory to their proper timing. Recent evidence for a circadian-based molecular mechanism within the pars tuberalis of the pituitary, which ties the short duration melatonin signal reflecting long day length to the hypothalamic increase of triiodothyronine (T3) through a thyroid-stimulating hormone/deiodinase2 paracrine mechanism is presented and evaluated in this context. A parallel is also drawn with the golden hamster, a long-day breeder, aiming to demonstrate that features of seasonality appear to be phylogenetically conserved. Finally, potential mechanisms of T3 action within the hypothalamus/median eminence in relationship to seasonal timing are examined.

Seasonal Effects on Female Fecundity and Male Sperm Availability in a Thermally Stable Temperate Population of Sailfin Mollies (Poecilia latipinna)

Fish species from temperate climates exhibit seasonal variation in reproduction triggered by abiotic variables such as day length and temperature. The sailfin molly Poecilia latipinna occupies habitats in the southern temperate zone in North America, but little is known about seasonal patterns in reproductive parameters such as female egg production and male sperm production, especially in spring-fed habitats. Males and females were collected monthly for 21 mo to: (1) examine the seasonal patterns in egg availability, (2) examine the relationship between female size and fecundity, (3) examine seasonal patterns in male sperm availability and (4) examine the relationship between male size and sperm availability. We found that reproductive investment varied seasonally in both males and females in a population of sailfin mollies occupying a spring-fed habitat. Because both egg and sperm production can be energetically costly, individuals may reduce costs associated with reproduction by reducing the availability of ready gametes during the time of year when mating is infrequent.

Ecology of antifouling resistance in the bladder wrack Fucus vesiculosus: patterns of microfouling and antimicrobial protection

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 411:33-48 (2010) - DOI: https://doi.org/10.3354/meps08644 Ecology of antifouling resistance in the bladder wrack Fucus vesiculosus: patterns of microfouling and antimicrobial protection M. Wahl1,*, L. Shahnaz1,2, S. Dobretsov1,3, M. Saha1, F. Symanowski1, K. David1, T. Lachnit1, M. Vasel1, F. Weinberger1 1Leibniz Institute of Marine Sciences, IFM-GEOMAR, Duesternbrookerweg 20, 24105 Kiel, Germany 2Present address: Department of Botany, University of Karachi, Karachi, Pakistan 3Present address: Department of Marine Science and Fisheries, Sultan Qaboos University, Muscat, Oman *Email: mwahl@ifm-geomar.de ABSTRACT: The impact of moderate environmental stress may be modulated by stress-induced shifts of biotic interactions such as host–epibiont relationships. We studied the stress regime in shallow Western Baltic habitats, the variability of fouling at different temporal and spatial scales, and whether common stressors—low light, high temperature and grazing—affect the abundance and composition of the biofilm on a regionally important macroalga, the bladder wrack Fucus vesiculosus. We further explored the alga’s capacity to chemically modulate the recruitment of microfoulers and analyzed whether this ability is impacted by stress. In laboratory, mesocosm and field experiments, fouling pressure and epibiotic cover on the alga varied strongly with changing environmental conditions such as temperature, irradiance, depth and grazing. The expectation that abiotic stress affects the fouling-modulating ability of the alga and thus indirectly produces the observed variability of epibiosis was not generally confirmed. Indeed, while the strength of chemical antifouling resistance varied seasonally, with a maximum in winter–spring and a minimum in late summer, this could not be related to temporal patterns of environmental stress, fouling pressure, or growth of F. vesiculosus. Only the seasonal variation in reproduction seemed to be in phase with antifouling activity. Controlled experiments confirmed that resistance strength was not affected by temperature or grazing, and only moderately by light. We conclude that the fouling modulation ability of F. vesiculosus may suffer from light reduction (e.g. by eutrophication effects), but is not sensitive to predicted warming or enhanced grazing. KEY WORDS: Marine algae · Stress · Epibiosis · Fouling modulation · Interacting stressors · Fucus vesiculosus Full text in pdf format Supplementary material PreviousNextCite this article as: Wahl M, Shahnaz L, Dobretsov S, Saha M and others (2010) Ecology of antifouling resistance in the bladder wrack Fucus vesiculosus: patterns of microfouling and antimicrobial protection. Mar Ecol Prog Ser 411:33-48. https://doi.org/10.3354/meps08644 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 411. Online publication date: July 29, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Seasonal variation in reproduction and population structure of the bivalve Limopsis tajimae in the upper bathyal zone of Suruga Bay, Japan

Seasonal variation in reproduction and population size structure was investigated for the suspension-feeding bivalve Limopsis tajimae Sowerby inhabiting the upper bathyal zone (300 m deep) of Suruga Bay, central Japan. The bivalve was collected at 1- to 4-month intervals for a period of 22 months, and bottom environment was monitored concurrently to detect factors affecting seasonality in the bivalve. Bottom water temperature, organic carbon and nitrogen contents in the sediments did not exhibit seasonal variation. Size-adjusted soft-tissue weight varied slightly, but statistically significantly between stations and months. However, its seasonal pattern was not obvious, and the pattern of temporal variation was totally different between stations. The sex ratio did not deviate from 1:1, and there was no significant difference between shell lengths of females and males. Females possess both immature small oocytes and large developed oocytes in their ovaries throughout the year, suggesting that they can potentially undergo year-round continuous reproduction. The proportion of developed oocytes in each female varied greatly from month to month, although no seasonal cycle was obvious. Population size structure of L. tajimae was polymodal. A mode of the smallest size class occurred in most months, suggesting long periods of bivalve recruitment. These findings indicate that seasonal variation in reproduction of the bivalve was negligible, probably reflecting constant physical and nutritive conditions of the bottom environment.

Seasonal variation in reproduction, juvenile growth, and adult body mass in golden lion tamarins (Leontopithecus rosalia).

Data on the ecology, demography, and morphology of 465 golden lion tamarins in 22 wild groups suggest that avoidance of reproduction and weaning of infants during the dry season shaped the pattern of female reproduction. Post-partum estrus may have evolved to allow females to produce and wean two successive litters during the 7-month season of abundant food resources. Support for these hypotheses includes observations that nearly all births, lactation, and weaning of infants occurred during the wet season, a period of relatively abundant trophic resources. Litter sizes in the wild were smaller than for the captive population. Evidence that food limitation may have a greater negative impact on young juveniles than lactating females includes observations that female weight did not decrease with lactation, and that many births occurred during the transition between dry and wet seasons. Juveniles gained less weight during the dry season than during the wet season; however, there was no significant difference between weights of adults born early vs. late in the wet season. For females producing two litters/year, litter size and infant mortality did not differ for litters born early and late in the wet season. Adult males gained weight before and lost weight during the month of highest probability of female estrus, suggesting that competition for mates is energetically expensive for males. Although resources were abundant, adult males did not gain weight during months when most infant carrying took place, suggesting that this activity is also energetically expensive. © 1994 Wiley-Liss, Inc.

Natural history of small mammals of subtropical montane areas in central Taiwan

Based on samples collected in 1989–90, I report on several aspects of the natural history of species of small mammals from seasonal montane areas in subtropical central Taiwan, including their reproduction, demography, sex ratio and body size. The climatic seasonality in the areas is striking. The wet season lasts from May through September and the dry season from October through April. The phenology of plant life is related to this seasonality: vegetative growth occurs primarily in the wet season, but fruit and seed production is concentrated in the dry season. Variation in the reproduction and demography are analysed between the wet and the dry season for six species, Apodemus semotus, Niviventer culturatus. Eothenomys melanogaster, Microtus Kikuchii, Anourosorex syuamipes and Soriculus fumidus. Two murid rodents. A semotus and N. culturatus. are capable of breeding year‐round, whereas the microtine rodents, E. melanogaster and M. Kikuchii, have discrete breeding seasons. The shrews, A. squamipes and S. fumidus are both seasonal breeders. but they differ in the timing of their breeding cycles. While S. fumidus breeds primarily in the late dry season, A. syuamipes reproduces in the wet season. Finally, seasonal variation in reproduction is discussed in relation to phylogenetic and physio‐ecological characteristics of these six species.

Experimental taphonomy of embryo preservation in a Cenozoic brooding bivalve

To distinguish between alternative explanations for the presence of synchronous broods in the Miocene-Pliocene bivalve, Transenriella species. we performed in situ burial experiments of the Recent species T. corfusa. All Recent Transennella species are asynchronous brooders; a single brood contains all or most developmental stages. Specimens from Miocene—Pliocene deposits of California suggest that some members of this taxon were synchronous brooders, i.e., all the embryos of a brood develop simultaneously with only one developmental stage represented at any time. The presence of synchronous Transennella broods in the Miocene—Pliocene could indicate that an evolutionary change in mode of reproduction has occurred in this genus. Alternatively, asynchronous brooding in this taxon may he conservative and preferential preservation of later stages of development, or seasonal variation in reproduction, could result in a taphonomic overprint. Our burial experiments indicate that the earliest stages of development are almost entirely lost; however. there is enough preservation of the later stages of development to distinguish the two modes of reproduction. Additionally. we discovered a single fossil specimen with an asynchronous brood. Based primarily on this specimen, and observations from the burial experiments, we conclude that the fossil synchronous broods are an artifact of preservation and asynchronous brooding in Transenella is conservative.

Reproductive Biology of Ord's Kangaroo Rat (Dipodomys ordii) in Oklahoma

Orel's kangaroo rat ( Dipodomys ordii ) was studied to determine age and seasonal variation in reproduction and the relationship between reproduction and environmental parameters. The 423 specimens collected in central Oklahoma during the 13-month study were classified into three age groups based upon cranial characters. Testes 6.8 mm or longer and weighing 0.07 g or more had mature spermatozoa. Adult males were reproductively capable throughout the year. Peak breeding periods in adult females occurred in January through March and in September. The average number of embryos per pregnant female was 2.8. There was a significant correlation ( r = 0.681) between the number of corpora lutea and the greatest daily precipitation during the month.

Food Habits, Energetics, and the Population Biology of Mammals

Data presented in this paper suggest that a complex interaction occurs between the physiological parameters of mammals and the growth and fluctuation of their populations: The Malthusian parameter rm increases with rate of metabolism, which in turn varies with body size and food habits. It can be concluded that it behooves all mammals to have as high a rate of metabolism as can be sustained by the quantity and quality of their food resources in space and time, because this adjustment will permit them to maximize their reproductive efforts. These interactions raise many questions, one of which concerns the temporal variation in reproductive strategies. Thus, Coady (1975) showed that the basal rate in the brown lemming (Lemmus trimucronatus) may be especially high during a winter in which the snow cover is reduced. Does a seasonal variation in the rate of metabolism therefore have a significant influence on seasonal variation in reproduction and therefore in population size? Whatever the correct answer to t...