Patterns Of Reproductive Activity Research Articles

Annual characteristics of estrous activity in wool and hair ewe lambs under subtropical conditions

The increased emphasis placed on lamb production in Brazil points to the need for a better knowledge of the annual pattern of reproductive activity in ewe lambs. This study evaluates the annual estrous activity pattern of hair and wool ewe lambs raised in southeast Brazil. Estrous characteristics were recorded for 12 months in ten Santa Inês and 21 Romney Marsh and Suffolk ewe lambs. Santa Inês ewe lambs exhibited a greater length of the normal estrous cycle (14 to 19 days) than Romney Marsh and Suffolk ewe lambs (17.0 ± 0.1 days vs. 16.5 ± 0.2 and 15.9 ± 0.2 days). All the ewe lambs presented a greater number of periods of estrus per animal per month for single estrous cycles (up to 26 days) during autumn and winter. During spring and summer there was a reduction of this number but this decline varied according to the breed. For Santa Inês ewe lambs the reduction was only significant in the summer. For wool ewe lambs the reduction was significant in both seasons but was more accentuated for Romney Marsh. The Romney Marsh ewe lambs had a more restricted breeding season than Suffolk and both presented optimal estrus activity in autumn and winter. Santa Inês ewe lambs had a continuous distribution of estrous cycles along the year, although presenting a reduction in the number of estrous periods in the summer. The ewe lambs of three breeds presented characteristics of sexual immaturity, like irregular estrous cycles and silent ovulations.

Reproductive biology of a large, aggregation‐spawning serranid,Epinephelus fuscoguttatus(Forsskål): management implications

The reproductive biology of Great Barrier Reef populations of the long‐lived grouperEpinephelus fuscoguttatus(brown‐marbled grouper or flowery cod) was investigated using histological analyses. Evidence provided by gonad morphology and age‐based demographics suggested monandric protogynous hermaphroditism. Younger age groups contained only immature and mature females, and all males were above the size and age of 100% female maturity, consistent with secondary males derived from mature females by adult sex change. Fishing records confirmed that spawning aggregations of this species and the co‐occurringEpinephelus polyphekadion(camouflage grouper) are sometimes targeted on the Great Barrier Reef. Sampling data revealed strong spawning seasonality forE. fuscoguttatus, with a relatively narrow annual spawning period (November to January). The temporal pattern of reproductive activity within the spawning period, based on occurrence of near spawning ovaries (containing hydrated oocytes), indicated spawning events may occur throughout much of the lunar cycle and only partly coincide with seasonal fishing closure periods on the Great Barrier Reef. The results indicate that protection would be enhanced by a longer seasonal closure.

Reproductive characteristics of free-livingCalomys venustus (Rodentia, Muridae)

Calomys venustus showed a cyclic seasonal pattern of reproductive activity characterized by a period of repose and a variable length of the period of sexual activity between August—September to May—June. The study was done from 1983 to 1999. During this time the population density increased from October—November to the end of autumn and sharply decreased in winter. Three peaks in rate of pregnancy were recognized in the breeding period: spring, summer and late summer. The average litter size was different among the three peaks in rate of pregnancy. The reproductive pattern had a peak at the beginning of the spring produced by overwintering animals, and another peak in summer-autumn caused by the reproductive activity of young born in the same period in which they breed. The spring cohort exhibited the greatest breeding contribution suggesting that this cohort is principally responsible for the yearly peak in abundance.

Breeding activity patterns, reproductive modes, and habitat use by anurans (Amphibia) in a seasonal environment in the Pantanal, Brazil

AbstractAnnual patterns of breeding activity, reproductive modes, and habitat use are described for a frog community in a seasonal environment, in the southern Pantanal, Mato Grosso do Sul, Brazil. Data were collected monthly between January 1995 and December 1998. A total of 24 species from four families; Bufonidae (3 species), Hylidae (10 species), Leptodactylidae (9 species), and Microhylidae (2 species) were registered. Three reproductive activity patterns are recognized among these species: continuous, explosive, and prolonged; 50% of the species were explosive breeders. Seasonal pattern of reproduction was verified for three analyzed years (1995-1997); most species reproduced during the rainy season (Nov-Jan). The reproduction was aseasonal in 1998; unexpected rains in the dry season lead to an unusual breeding activity. Five reproductive modes were noted — 62.5% of the species have the generalized aquatic mode, and 33.3% deposit eggs embedded in foam nests. Many species used the same sites for reproduction, although temporal partitioning and calling site segregation was observed. The occurrence of many species that exhibit explosive breeding early in the rainy season is common in seasonal and open environments with variable and unpredictable rainfall, as is the case in the Pantanal.

Annual variation of breeding patterns of the toad, Melanophryniscus rubriventris (Vellard, 1947)

AbstractClimate may play a direct role in determining patterns of reproductive activity in anurans. Investigating the responses of males and females attending a breeding site to environmental variation are of particular interest regardless the possible effect of climate change on the decline of populations. I studied annual variation over two years in the breeding population size and breeding phenology of the diurnal toad, Melanophryniscus rubriventris, in a seasonal environment characterized by temporal and spatial uncertainty due to climatic conditions. Breeding activity of this toad was opportunistic throughout a prolonged spring-summer breeding season. Direct influence of rainfall on the onset and extent of breeding activity was detected in both years. Spawning activity showed a clear pattern of two three-day peaks mostly related to heavy rainfall events. Males always significantly outnumbered females at breeding sites. The disparity of rainy season extent between the two breeding seasons studied resulted in different annual patterns of arrival and length of residence of adults. Males and females remained several days longer during the second year than during the first year. Because adults showed highly variable annual patterns of breeding activity studies involving only a few years may yield misleading results concerning the nature and extent of the decline of the species or populations. Future studies on the ecology and conservation of the species should include long-term monitoring.

Metal concentrations in sediments and clams in four Moroccan estuaries.

Metals (Cd, Cu, Ni, Zn, Mn and Fe) were analyzed seasonally over three years in sediments and in tissues of the clam Scrobicularia plana in four Moroccan Atlantic estuaries: Loukkos, Sebou, Bou Regreg and Oum er Rbia. Of these metals, Cd was at the lowest concentrations in sediment. Concentrations of Cu, Zn, and to a lesser extent Ni, in sediments suggest greater contamination in Sebou and Bou Regreg than in the other estuaries. The fluctuations of Mn and Fe concentrations in the fine surface sediments reflect their continental origin and show seasonal variations that indicate soil run-off following rain events. Concentrations of Cu, Zn, and especially Ni in clam tissues in these estuaries were generally higher than in some other common bioindicator bivalve species. The seasonal variations in S. plana's tissue metal concentrations are linked to patterns of reproductive activity for all metals except Cd and possibly Zn, whose tissue concentrations may be regulated. Mn and Fe concentrations in S. plana were positively correlated to sediment levels of these metals.

Assessing Toxicant Effects in a Complex Estuary: A Case Study of Effects of Silver on Reproduction in the Bivalve, Potamocorbula amurensis, in San Francisco Bay

Contaminant exposures in natural systems can be highly variable. This variability is superimposed upon cyclic variability in biological processes. Together, these factors can confound determination of contaminant effects. Long term, multidisciplined studies with high frequency sampling can be effective in overcoming such obstacles. While studying trace metal contamination in the tissues of the clam, Potamocorbula amurensis, in the northern reach of San Francisco Bay, an episode of high Ag concentrations was identified (maximum of 5.5 µg g−1) at two mid-estuary sites. High concentrations were not seen in clams up-estuary (maximum of 1.92 µg g−1) from these sites and were reduced down-estuary (maximum of 2.67 µg g−1). Silver is not common naturally in the environment, so its elevated presence is usually indicative of anthropogenic influences such as municipal and industrial discharge. Monthly sampling of reproductive status of clams characterized the reproductive cycle and differences in the patterns of reproductive activity that corresponded to changes in Ag tissue concentrations. The proportion of reproductive clams was less than 60% during periods when tissue concentrations were high (generally >2 µg g−1). When tissue concentrations of Ag decreased (≤1 µg g−1), the proportion of reproductive clams was 80 to 100%. A comparison between the annual proportion of reproductive clams and annual Ag tissue concentrations showed a significant negative correlation. No other measured environmental variables were correlated with reproductive impairment. The weight-of-evidence approach strongly supports a cause and effect relationship between Ag contamination and reduced reproductive activity in P. amurensis.

Assessment of the Reproductive State in Male Swift Parrots (Lathamus discolor) by Testicular Aspiration and Cytology

This study aimed to develop a technique of testicular aspiration and cytology for assessing the status of reproductive activity in small male birds with the swift parrot (Lathamus discolor) as a model species. To validate this technique, cytology was compared with testicular histology and seasonal variations in testicular volume in both wild and captive birds. The described technique of gonad examination and testicular aspiration and cytology was effective in tracking the seasonal variation in testicular volume and spermatogenesis in swift parrots; all 5 stages of spermatogenesis described histologically were identified. But testicular histology provided more information about the cellular architecture of the testes than was evident from cytology. Testicular aspiration and cytology was a reliable and safe technique for assessing the status of reproductive activity during the breeding season in small male parrots. The normal seasonal patterns of reproductive activity of male birds need to be understood for clinical assessment of the reproductive status.

Seasonal variation in the reproductive activity of the wild rabbit (Oryctolagus cuniculus algirus) in a Mediterranean ecosystem

To establish a successful strategy for managing wild rabbit (Oryctolagus cuniculus algirus) populations it is essential to have a clear understanding of reproductive biology. In Portugal, previous work suggested a seasonal pattern of reproductive activity for this species. In this study we present additional information on the seasonal reproductive activity of the wild rabbit as well as data on the influence that environmental factors have on the onset and length of the breeding season. The study was carried out in Pancas, southern Portugal, from October 1997 to September 1998. Rabbits were collected every two months and post mortem analyses were performed. In the males, circulating concentration of testosterone, gonadal weight, daily sperm production, diameter of the seminiferous tubules and the thickness of epithelial cells were measured. The numbers of corpora lutea, embryos and placental scars were recorded in the females. To assess abundance and quality of food, samples of herbaceous vegetation were collected and analysed for water, fibre and crude protein content. The reproductive season extended from November to June with a peak in March/April, with both sexes showing an annual cycle of gonadal development and subsequent regression. All analysed females were pregnant and/or lactating between March and June. The mean litter size estimated by counting the embryos in the uteri was 3.90 ± 0.50. Daily sperm production was highest between November and April. Testicular function was strongly correlated with environmental temperature and the water content of the vegetation, and both testicular and ovarian development were correlated with vegetation biomass.

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The daily patterns of reproductive activity in the diamondback moth were studied outdoors in Miyazaki, Japan, between June 1998 and January 1999. Mating primarily began within one or two hours after sunset, although it also occurred during the daytime in the winter. Mating time was longer in cool seasons than in warm seasons. In June to October, oviposition occurred mainly at night with a peak at one or two hours after sunset. In November, however, some eggs were laid during the daytime. Daytime oviposition was observed more frequently in colder seasons. It is suggested that a low nighttime temperature suppresses the normal behavior of the diamondback moth, and changes the nocturnal oviposition pattern to a diurnal one. The daily rhythm of mating behavior coincided most closely with that of egg-laying behavior.

Significance of Prolonged Copulation Under the Restriction of Daily Reproductive Time in the Stink Bug <I>Megacopta punctatissima</I> (Heteroptera: Plataspidae)

Copulation duration and daily reproductive activity pattern of the stink bug Megacopta punctatissima Montandon were investigated in the laboratory and the field. Mean copulation duration was >10 h regardless of sex ratio and few copulations continued for more than 24 h in the laboratory. In the field, mating aggregations and copulations were found from 1400 to 1000 hours on the next day, but bugs tended not to copulate from 1000 to 1400 hours. This daily reproductive activity pattern seemed to restrict the copulation duration to about 24 h at the longest. Sperm transfer from a male to a female spermatheca was complete within 2–4 h. Thus, it appears that copulations over 4 h serve as postcopulatory mate guarding. However, copulations did not always continue until oviposition because female oviposited after about a 7-d interval. Our findings suggest the possibility that prolonged copulations that do not continue until oviposition may also function as postcopulatory mate guarding within daily reproductive time. Alternative hypotheses, such as copulatory courship, for prolonged copulation of M. punctatissisma are also discussed.

Spring Movements of Paddlefish in a Prairie Reservoir System

ABSTRACT Paddlefish (Polyodon spathula) movements and habitat use were monitored in the Keystone Reservoir System, Oklahoma during 1996–1998 to determine reproductive activity patterns. Paddlefish spring spawning migrations were more dependent on water flows than water temperature or photoperiod. Paddlefish moved up the Cimarron River and Arkansas River in 1997 and 1998 when spring flows increased. However, they did not migrate up the rivers in 1996, a year with extremely low flows. Suitable spawning substrate was found in the Salt Fork River, a major tributary of the Arkansas River, and the tailwaters of Kaw Dam on the Arkansas River. Paddlefish were located over suitable spawning substrate in the Salt Fork River; however, no larvae were collected. Although paddlefish migrate up the Cimarron River in spring, minimal spawning habitat may limit successful spawning in that river. In 1998, paddlefish moved into the Salt Fork River rather than the Kaw Dam tailwaters, presumably because there was limited flow from Kaw Dam that spring. Paddlefish in the Keystone Reservoir system appear to have adapted to the high spring water temperatures and fluctuating flows enabling successful reproduction.

Seasonal patterns in the reproductive activity of barnacle-dwelling littorinids

The reproductive activity of a population of barnacle-dwelling littorinids at Peak Steel, on the north-east coast of England, was investigated. Variation in the number of mature males and females, expressed as a percentage of the whole population, showed a marked difference among the barnacle-dwelling littorinids. Littorina neglecta displayed a distinct seasonal component to its reproductive activity, with a peak in early summer. Littorina arcana B also displayed a distinct seasonal component, with a lull in the summer months. However, L. saxatilis B maintained its reproductive activity all year, but with an increase in output in the summer. The reproductive activity of both L. arcana B and L. saxatilis B follow similar patterns of reproductive activity as their typical non barnacle-dwelling forms, suggesting that these are true barnacle-dwelling ecotypes. The controversy surrounding the specific status of L. neglecta is also discussed.

Overwintering strategies in Calanus finmarchicus

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 193:95-107 (2000) - doi:10.3354/meps193095 Overwintering strategies in Calanus finmarchicus Alasdair Hind1, William S. C. Gurney1,*, M. Heath2, A. D. Bryant2 1Department of Statistics and Modelling Science, University of Strathclyde, Glasgow G1 1XH, Scotland, UK 2Fisheries Research Services, Aberdeen Marine Laboratory, Aberdeen AB9 8DB, Scotland, UK *Corresponding author. E-mail: bill@stams.strath.ac.uk ABSTRACT: The marine copepod Calanus finmarchicus is known to overwinter at depth in a state analogous to diapause in terrestrial insects, but the cues which cause individuals to enter and leave this state are the subject of speculation. In this paper we use a simple demographic model, driven by environmental data from 4 distinct locations in the organism's eastern range, to test the plausibility of a number of candidate mechanisms. We start from Miller et al.'s (1991; Mar Ecol Progr Ser 72:79-91) hypothesis that diapause is controlled by photoperiod, and show that this leads to unrealistic patterns of reproductive activity in northern waters. We extend the model to include the recently reported phenomenon (Hirche 1996a; Ophelia 44:111-128) of delayed gonad maturation in females experiencing low food concentrations. This yields more plausible annual patterns, but fails to reproduce observed geographical variation in the timing of the yearly onset of reproductive activity. Our final model dispenses with photoperiodic control and assumes that diapause duration is controlled by the normal development processes operating at a reduced rate. This model reproduces all the qualitative features of the patterns of reproductive activity observed at our 4 test sites, thus demonstrating that photoperiod cueing is not a necessary prerequisite for the regular re-ascension of C. finmarchicus into surface waters. KEY WORDS: Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 193. Publication date: February 28, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

Reproductive activity patterns of anurans in two different altitudinal sites within the Brazilian Caatinga

Six different categories of breeding sites were investigated from August 1989 to July 1990 at São José do Bonfim (240 m above sea level) and Maturéia (770 m above sea level), two sites localized in the Brazilian Caatinga (State of Paraíba). A severe drought affected these areas during the study. Even so, calling males, nests and/or tadpoles of 20 species from 5 families were found. Leptodactylidae was the most numerous family, with nine species distributed among five genera. In Maturéia, due to the low evapo-transpiration rates, less variation of water levels was observed. Males of hylids and leptodactylids began their calling activities together, whereas at São José do Bonfim leptodactylids began their calling activities first. Thus, at Maturéia high concentrations of individuals and large choruses were found at the beginning of the rainy season, whereas in São José do Bonfim high concentrations were found later. Although up to eleven synchronously calling species were recorded in São José do Bonfim and up to ten synchronously calling species in Maturéia, egg masses and tadpoles of few species were found at both study sites, suggesting that some species may vocalize but do not reproduce in adverse periods.

Length-based analysis of population dynamics and stock identification in the sardine fisheries around East Java, Indonesia

The biology and population dynamics of Sardinella longiceps and S. fimbriata were studied around East Java, Indonesia. The total catch of Sardinella spp. in East Java was 56 000 tons in 1993, and more than 50% of this catch was landed by purse seiners. Samples of purse seine catches were taken from three landing sites around East Java, at the Madura Strait, the Bali Strait and at the Indian Ocean. Biological data were collected on a monthly basis, during a period of 2 years, from March 1990 to March 1992. Patterns in reproductive activity were determined on the basis of changes in geometric mean gonado-somatic index (GSI) of mature fish. Length-based methods were used to estimate growth and mortality. Peak catches of sardines from the Madura Strait and the Bali Strait were recorded at the beginning of the rainy season around November and December. The Indian Ocean produced peak catches during the dry season, from July through October. Considerable differences exist between monthly catches from peak seasons and monthly catches from off-seasons. Patterns in reproductive activity could be recorded for the fish from the Madura Strait and both species of Sardinella showed peak reproductive activity there around November and December. Both species were estimated to grow to lengths of around 12, 17 and 19 cm in their first, second and third year respectively. Based on the age structures in the catches from different sampling sites, in combination with the migration patterns of the fish, it was concluded that both S. longiceps and S. fimbriata stocks can be divided into northern and southern populations. The northern populations were sampled in the Madura Strait and were assumed to be from the Java Sea, Makassar Strait and/or Flores Sea. These stocks consist of three year classes and do not seem to be under excessive fishing pressure. The southern stocks, well known from the Bali Strait sardine fisheries, are concluded to be under very heavy fishing pressure. These stocks consist of only two year classes and hardly any fish reach the length of maturity. Regulations controlling fishing effort are needed urgently for these fisheries.

Ovarian cycles and microhabitat use in two species of topminnow, Fundulus olivaceus and F. euryzonus, from the southeastern United States

Differences in spawning seasonality, inferred from ovarian cycles, and microhabitat use for two closely related Fundulus species were not effective as potential reproductive isolating mechanisms. Seasonal spawning periodicity of F. olivaceus and F. euryzonus as shown by changes in mean egg diameter and mean number of mature eggs recovered from ovaries showed nearly identical temporal patterns in reproductive activity. Peak egg development was between April and May and was lowest by the end of August. Univariate comparisons of 11 environmental variables associated with aggregations of Fundulus spp. revealed highly significant differences in several of these variables. However, individuals of both species were frequently collected together, and microhabitat differences did not remove the potential for mismating.

Species composition and seasonal capture rates of terrestrial amphipods in a lowland and highland forest in Tasmania

Composition of the amphipod fauna and seasonal changes in captures in pitfall traps were compared at a lowland forest in northeastern Tasmania and three sites in highland forest in central Tasmania. The number of species at the highland sites (five) was greater than for the lowland area (two), possibly due to the greater development of the litter habitat and the moister, more humid conditions at the highland sites. Capture rates were correlated with temperature, but not rainfall, at both the lowland and highland areas. However, minium temperature was most significant for the highland sites, and maximum temperature was most significant at the lowland area. Captures at the highland sites were proportionally greater in autumn and lower in summer and showed a peak in October which was not present at the lowland area. Capture rates are most likely influenced by both activity levels and population size, as determined by seasonal reproductive patterns. It is, therefore, possible that the differences in the seasonality of captures at the highland and lowland areas may be related to different patterns of reproductive activity at the different altitudes.

Effect of yohimbine on the reproductive behavior of the male nile crocodile Crocodylus niloticus

The effect of yohimbine, an α2-adrenergic blocker, on the reproductive activity of 12-year-old male, captive Nile crocodiles was tested on 18 animals equally divided into 3 ponds. In each pond, there were 6 males and 30 females. In the first group, six of six males received yohimbine capsules of 30 mg, twice a day, for 1 week. In the second group, two males of a group of six were administered a similar dose of yohimbine. Another group of six males in a separate pond were used as control group. The yohimbine treatment had a significant (p < 0.05) effect on the frequency of headslap display (the main behavioral pattern of reproductive activity) in all treated animals but did not result in a significant increase in copulation frequency. In the two treated groups, the reproductive period was prolonged by 3 weeks, 8–11 weeks. We found a significant increase in the fertility percentage of eggs laid by females in the male-treated groups (30.5% in control group females, 34.1% in the partly treated, and 39.0% in the pond where all six males were treated), even though no increase in mating frequencies was noted. This might be due to more successful copulations. During the treatment period, the daily activity peak, when the male's headslap performance was the most frequent, was shifted from 5:00–6:00 p.m. in the treated group. This effect caused females to enter the water earlier than in the control group.

Large male mating advantage in natterjack toads, Bufo calamita: sexual selection or energetic constraints?

Variation in the effect of male body size on mating success was studied in natterjack toads during two breeding seasons with different temporal patterns of reproductive activity. Larger males were more likely to mate than small males in the season with a single peak and continuous breeding activity, whereas random mating by size was found when reproduction occurred during several peaks separated by periods of inactivity. Playback tests did not reveal any consistent preference by females for call variables related to male body size other than call intensity. Moreover, direct observation of pair formation resulting from capture of females by non-calling males (searchers and satellites) suggested that most females did not have the opportunity to make any choice. Direct male-male competition for females already in amplexus was negligible as suggested by the low rate of take-over success. Body size advantage occurred indirectly through a positive correlation with chorus attendance. One hypothesis is that smaller males may attend the breeding site less frequently because of energy limitations. Energetic constraints may arise in the long term, affecting the energy that should be allocated to growth, which is higher in small males, or in the short term, affecting the capacity for sustained chorus attendance. Growth rate was not correlated with chorus attendance. However, smaller males lost weight more rapidly in both seasons. This might explain why they had a lower attendance rate than larger males, giving rise to a higher mating success in the latter.