Seasonality and reproduction in aphids

Aphids are short-lived and occupy habitats which vary in quality in both time and space. They exploit their ephemerally nutritious habitats by rapidly producing many small offspring when conditions are good, and fewer, larger offspring when conditions are poor, at which time they also divert more of their resources into fat storage. Aphids of each of the generations which make up a life cycle have specific reproductive strategies adapted to the conditions they are most likely to encounter, that is they anticipate the predictable seasonal trends in habitat quality.     

Hormones and reproduction in scleractinian corals

Most broadcast spawning scleractinian corals synchronously release gametes during a brief annual spawning period. In southern Taiwan, the mass spawning of scleractinians occurs in lunar mid-March. The exact cues triggering this annual phenomenon remain unclear. A scleractinian coral, Euphyllia ancora has been selected as a model for the hormones and reproduction studies. Testosterone (T) and estradiol (E2) in free and glucuronided forms were identified and consistently detected in coral polyps throughout the year. Peak levels of free E2, glucuronided E2 and T were obtained in the coral tissue just prior to spawning. The presence of specific aromatase activity was demonstrated in coral tissue. Higher concentrations of free E2 than glucuronided E2 were detected in the coral tissue throughout the year. In contrast, higher levels of glucuronided E2 than free E2 and glucuronided T were found in seawater during mass coral spawning. Furthermore, immunoreactivity and biological activity of immunoreactive gonadotropin-releasing hormone (irGnRH) was detected and quantified in coral tissue. Coral extracts (irGnRH) and mammalian (m)GnRH agonist had a similar dose-dependent effect on luteinizing hormone (LH) release in black porgy fish pituitary cells (in vitro). Peak levels of irGnRH were detected during the spawning period. In in vivo experiments, mGnRH agonist time- and dose-dependently stimulated aromatase activity, as well as the levels of T and E2 in free and glucuronided forms in coral. In conclusion, our data suggest that irGnRH and glucuronided E2 may play important roles in the control of reproduction and mass spawning in corals.     

Diurnal periodicity in Daphnia reproduction

The diurnal periodicity of reproduction in a reservoir population of Daphnia galeata Sars was tested by two methods (egg age distribution analyses and direct observation of hatching). No significant diurnal synchronization of reproduction in the natural cladoceran population was found. A conspicuous shortage of older embryonic stages was parallely revealed by analyses of diurnal changes of egg age distribution. Suggested selective feeding of fish on gravid females of Daphnia brooding embryos with black eye pigmentation is discussed.     

Synchronous reproduction of corals in the Red Sea

Multi-species synchronous spawning was first described on reefs off the east and west coast of Australia. In contrast, locally abundant species in the northern Red Sea and the central Pacific have little overlap in the time of reproduction. Consequently, the idea developed that high levels of spawning synchrony both within and among species was largely confined to Australian reefs. Here, we show that gamete maturity in colonies of the genus Acropora was highly synchronous in the Red Sea. In early April 2008, at two locations separated by 300 km, 13 of 24 species sampled had mature colonies, and a further 9 species had immature colonies. In late April–early May 2008, all colonies sampled had no oocytes, indicating colonies had spawned a few days after the full moon of 20 April 2008. Similarly, in 2009, 99% of colonies from 17 species at Hurghada were mature in late April, and all were empty in early May. Spawn slicks suggested many of these colonies had released gametes three night prior to the full moon on 8 May 2009. This level of synchrony in gamete maturity is among the highest ever recorded and similar to that typically recorded in Acropora assemblages on Australian reefs. While further work is required to document the night of gamete release, these data strongly suggest that high levels of spawning synchrony are a regular feature of these Red Sea coral assemblages and that multi-species spawning occurs on or around the full moon in April and/or May.     

Seasonality and reproduction in wild-living cats in Scotland

The definition of the wildcatFelis silvestris Schreber, 1775 in Scotland is contentious, in light of long-term interbreeding with domestic catsF. catus Linnaeus, 1758. Two morphological groupings (Group 1 and Group 2) have previously been proposed to explain the variation found in wild-living cats in Scotland, with Group 1 cats closest to wildcats and Group 2 cats to domestic cats. Data from the reproductive tracts of 185 wild-living cat carcasses and evidence of reproductive activity in 31 live cats were analysed in order to compare reproductive activity between the morphological groups, and in relation to seasonality and existing data on wildcats and domestic cats. For males, Group 2 cats had a greater mean relative testes size than Group 1 cats. Estimated from corpora lutea, there was a suggestion that Group 1 females showed more seasonality in oestrous than Group 2 cats. In all wild-living cats, the mean litter size was 4.3 and estimated birth dates were throughout the year, but least in winter. A high number of pseudopregnancies were recorded. The results were consistent with the hypothesis that Group 2 cats are closer to domestic cats. However, the variation observed in the sample of wild-living cats reported here, suggested that reproduction was neither strictly seasonal nor outside the range observed in some feral cat populations.     

Seasonality of reproduction in sheep and its control by photoperiod

Seasonality of the reproductive cycle in sheep is a general phenomenon for mid-latitude breeds. The proximal part (breeding season) and also partially distal part (end of gestation and beginning of lactation) of this cycle is controlled by photoperiod, whatever the form of light regimens. Data are presented which indicate that male and female do not necessarily have the same photoperiodic sensitivity. Gonadal stimulation in the ram starts 1.5-2 months earlier than in the ewe under annual variations. Photoperiod controls the reproductive cycle by the intermediary of the hypothalamo-pituitary axis. There are both a steroid-independent and a steroid-dependent effect of light, depending on both decreasing and increasing daylength in mid-latitudes. Data are also presented which support Bunning's hypothesis on photoperiodic time measurement in mammals. Sheep measure photoperiodic time by using a circadian rhythm of photosensitivity. Daylength is not measured by the total duration of exposure to light but by the illumination of two special set points during the day, one of them entraining the circadian rhythm of photosensitivity and the other inducing or not inducing a physiological response if it is coincident, or not coincident, with photoinducible phase of that rhythm. A photoinducible phase has been found for prolactin secretion, and perhaps also for LH secretion. Melatonin secretion is used by sheep for measuring daylength. However, that secretion disappears during two set points during the day, thus raising the possibility of using alternatively melatonin and light pulse for controlling the reproductive cycle in sheep.     

Cathemerality and lunar periodicity of activity rhythms in owl monkeys of the Argentinian Chaco

Although most South American owl monkeys are mainly nocturnal, Aotus azarai azarai of the Argentinean Chaco regularly shows diurnal activity. In this study we examined the strong influence of moonlight on its diurnal and nocturnal activity, as well as the interaction of moonlight effects with other exogenous factors. We analyzed long-term automated activity recordings obtained with accelerometer collars from 7 owl monkeys during 2003 and 2004. Our data show marked lunar periodic and seasonal modulations of the owl monkeys' activity pattern. On full moon days they were active throughout the whole night and displayed reduced activity during the day. With a new moon, activity decreased during the dark portion of the night, peaked during dawn and dusk and extended over the bright morning hours. Waxing and waning moons induced a significant increase in activity during the first and the second half of the night, respectively. During the cold winter months the monkeys displayed twice as much activity throughout the warmer bright part of the day than during the rest of the year. These findings indicate that A. a. azarai is mainly a dark-active species, but is still able to shift a considerable portion of activity into the bright part of the day if unfavourable lighting and/or temperature conditions prevail during the night.     

Sexual reproduction,development and larval biology in scleractinian corals

This paper brings together widely scattered information on sexual reproduction in scleractinian corals. It includes a review of information and ideas on sex determination, gametogenesis, gametogenic cycles, fertilization and embryonic development, spawning and planula release, larval behavior, settlement and metamorphosis. The review deals with corals from different habitats and organismic assemblages, including tropical reef corals, temperate water corals, solitary and colonial forms. A summary table of coral species and their known reproductive characteristics is presented.     

Search for lunar periodicity in the bannertail kangaroo rat (Dipodomys spectabilis)

Abstract

The endogenous activity cycle of the nocturnal bannertail kangaroo rat was investigated. Although bannertail activity is a function of the lunar day as well as the solar day, all ten subjects exhibited free‐running activity periods of solar‐day length; there was no evidence of an endogenous lunar‐day cycle. Animals were provided with a burrow system and a small pseudo‐desert, a laboratory facility in which animal activity data closely resembled measurements taken in the field. Several analytical techniques for quantifying the data were utilized, and one, the mean interval of activity, is recommended to other investigators.     

Seasonality of reproduction in the European badger Meles meles in south-west England

The reproductive cycle of male and female badgers in the south-west of England was studied by post-mortem examination of 1875 badgers collected in 1973–80. The sample was obtained by several methods and showed that animals obtained as road casualties were not representative of the total population samples. Active spermatogenesis was present throughout the year, and in some males aged 8–9 months. A few females first ovulated as yearlings but most primiparous females were adults. Births were in general confined to the early part of the year, but ovulations and matings also occurred at other times. Almost all (97%) adult females possessed corpora lutea. Unimplanted blastocysts were found in females for 11 months of the year (over 80% of adult females in July-November). Implanted embryos were found in only 32% of adults in January and February: the number of blastocysts per female and the number of implanted embryos per female were not significantly different, indicating that sows implanted all blastocysts or none. Foetal mortality was 36% and post-natal losses were estimated at 42% from the proportion of lactating females.     

Seasonality of reproduction by liverbearing fishes in tropical rainforest streams

Reproductive ecology, population structure, and diets of three common livebearing poeciliid fishes (Alfaro cultratus, Phallichthys amates, Poecilia gilli) from rainforest streams in Costa Rica were investigated over ten continuous months. The region experiences little annual temperature variation, and although monthly rainfall is continuous each year, two brief dry seasons typically occur. Monthly changes in indices of ovarian condition, percentages of females with developing embryos, and population size structure revealed that reproductive output by females of all three species varied seasonally. Based on testicular condition, males were reproductively active year-round, however the mean gonadal index for males of two algivorous species showed low levels of seasonal cycling that largely coincided with female variation in reproductive effort. All three species had seasonal differences in the female size-brood size relationship, whereby larger females tended to carry more embryos during the wet season. Several important adult and neonate food resources are more available in the flooded forest during the wet season, which is also the period when conspecifics and predators are at their lowest per-area densities. Three hypotheses are discussed: (1) brood size in relation to conspecific density-mating frequency, (2) reproductive allocation in response to variation in adult food resources, and (3) selection for greater reproductive effort during conditions optimal for juvenile growth and survival. Data for Alfaro were consistent with the latter two hypotheses. In Phallichthys and Poecilia, diets were poorer during wet seasons, indicating that reproductive effort does not coincide with availability of adult food resources, and that selection probably favors greater reproductive effort during periods optimal for juvenile growth and survival.     

Seasonality of reproduction and the length of gestation in southern right whales Eubalaena australis

From the seasonal occurrence of 11 stranded nconates, the earliest and latest observations of possible calving behaviour, and the seasonal incidence of calves in shore-based counts, the extent of the calving season for southern right whales off South Africa can be characterized as from late June to late October, with a peak in August. The occurrence of 89 'new' calves located during monthly photogrammetric flights between July or August and November indicated that 50% were born by 1 September in 1988 and by 15 August in 1989, and that the effective calving season (in which 95.5% of calves are estimated to have been born) lasted 118 days in each year. From regression analysis of the lengths of 221 foetuses and their dates of death, and assuming a mean date of birth of 24 August, the duration of the linear phase of foetal growth is estimated to be 325 days, and the mean size at birth 6-1 m. Uncertainty over the duration of the initial, non-linear phase of foetal growth results in alternative estimates of 357 or 396 days for the total length of gestation. Foetuses of smaller females seem to be conceived later (or experience a longer initial, non-linear phase of foetal growth) than those of larger females. The apparent rarity of adult females in coastal waters in the year in which they are presumed to conceive is attributed to either a brief residence time or the possibility that conceptions may occur well outside coastal waters.     

Seasonality and spatial variability in the reproduction of two Antarctic holothurians (Echinodermata)

Summary Seasonality in the reproduction of Ekmocucumis steineni and Psolus dubiosus (Holothuroidea) from the Antarctic shelf was investigated. The material was collected in spring (October/November) and autumn (mainly February) in the southeastern Weddell Sea. For E. steineni differences between both seasons in relative female fecundity and relative gonad weight were found in both sexes. Large yolky oocytes (0.3–1.0 mm in diameter) forming 1–3 cohorts were present in spring, nearly none in autumn. A delayed or prolonged spawning is possible, depending on the locality. No seasonal differences were found in P. dubiosus, a brood-protecting species with a lower fecundity and larger eggs (1.5 mm in diameter). A longer spawning phase in P. dubiosus than in E. steineni (October to January) is suggested. Both species are suspension feeders and their intestines were more filled with organic material in autumn than in spring. However, the occurrence of mature oocytes was not directly linked with the seasonal availability of food. The size-frequency distribution of the entire material in the study area was heterogeneous, indicating differences in long-term environmental conditions. The data show an evolutionarily more evolved high Antarctic mode of reproduction in P. dubiosus with a prolonged reproductive period than in E. steineni which has a distinct annual spawning cycle.     

Seasonality of reproduction in male rock elephant shrews, Elephantulus myurus

Male rock elephant shrews, Elephantulus myurus , showed active spermatogenesis throughout the year but had significant reductions in testis and prostate size, the proportion of interstitial cells and sperm numbers and viability from April to June, when no pregnant females were recorded. Rock elephant shrews have relatively small testes and extragonadal sperm reserves compared to many similar–sized mammals     

Seasonality of reproduction in the three largest terrestrial rodents of French Guiana forest

We investigated the main life history of the three largest terrestrial rodents of French Guiana forest: the acouchy (Myoprocta exilis), the agouti (Dasyprocta leporina) and the paca (Agouti paca), using data collected during several years. There were noticeable differences among the species in sexual maturation and degree of seasonality in reproduction. Percentage of pregnant females, births and juveniles, and body weight of juveniles decreased progressively from the acouchy, through the agouti to the paca. The acouchy was by far the most seasonal: no births occur in the period August–October, 56% of births were encountered in November–January; consequently, young form an unique cohort in the population. The agouti was also seasonal, but to a lesser degree. Newborns appeared in every period of the year in paca, without any formation of cohort of young. These differences tended to be linked to the seasonal importance of fruits in diets, the most aseasonal species having the most diversified diet during the poor fruit season.

Zusammenfassung

Jahreszeitliche Fortpflanzung von den drei größten terrestrischen Nagern im Regenwald von Französisch GuayanaDie Untersuchungen beziehen sich auf die wichtigsten Merkmale der Lebenszyklen der drei größten terrestrischen Nager, Acouchi, Aguti und Tieflandpaka, im Regenwald von Französisch Guayana, unter Verwendung von über mehrere Jahre währenden Beobachtungen, die beachtenswerte Unterschiede in bezug auf Geschlechtsreife und Fortpflanzung aufzeigen. Fortpflanzung und Populationsstruktur, wie Prozentsatz trächtiger Weibchen, Geburten, Auftreten von Jungen sowie deren Körpergewicht verringern sich kontinuierlich von Acouchis über Agutis hin zu Tieflandpakas. Während Acouchis die bei weitem am stärksten ausgeprägte jahreszeitlich gebundene Fortpflanzung mit 56% der Geburten in den Monaten November bis Januar zeigen, konnten von August bis Oktober keine Geburten beobachtet werden. Demzufolge treten die Jungen in der Population als eine einheitliche Altersklasse auf. Eine periodische Fortpflanzung zeigen auch Agutis, wenn auch weniger ausgeprägt, wohingegen bei Tieflandpakas über das gesamte Jahr hinweg Junge geboren werden, ohne jegliche Bildung von einer Altersklasse. Diese Unterschiede scheinen an die jahreszeitlich bedingte Produktion von für die Ernährung wichtigen Früchten gebunden zu sein, wobei die am wenigsten periodische Art in der früchtearmen Zeit das breiteste Nahrungsspektrum aufweist.     

Effect of lunar periodicity on the locomotor activity of silver-stage Japanese eel,Anguilla japonica

Lunar periodicity has been thought to influence the onset of the spawning migration of anguillid eels. In this study, we measured daily locomotor activity of 8 silver-phase Japanese eels Anguilla japonica in outdoor tanks to examine the effect of lunar periodicity on their activity and the following seaward migration. The activity of silver eels was highest around the new moon during the early part of the experiment, which is the ordinary season of seaward migration in Japan. The observed patterns of activity may reflect the importance of the lunar cycle for the onset of the spawning migration in anguillid eels.     

Locomotion,asexual reproduction,and killing of corals by the corallimorpharian Corynactis californica

The rates at which some sedentary coelenterates move across substrates, spread by asexual reproduction, and competitively damage their neighbors may greatly affect their ability to survive on hard marine substrates. However, almost nothing is known about these processes in the Corallimorpharia. In this study, locomotory rates varied widely between members of a single clone of the corallimorpharian Corynactis californica. Polyp movement rates (0–14 mm month^–1) were slower than those of many Actiniaria, possibly due to the lack of basilar muscles in corallimorpharians. Rates of asexual reproduction by C. californica polyps in the laboratory varied 10-fold among 8 clones. The minimal time to double the number of polyps per clone (2 months) was intermediate to doubling times known for Actiniaria and Scleractinia. The rate at which polyps killed individuals of the scleractinian Astrangia lajollaensis also varied widely within and between clones. Asexual reproductive rate correlated positively with coral killing rate.     

Sexual reproduction of Acropora reef corals at Moorea, French Polynesia

Little information is available on reproductive processes among corals in isolated central Pacific reef regions, including French Polynesia. This study examined the timing and mode of sexual reproduction for Acropora reef corals at Moorea. Spawning was observed and/or inferred in 110 Acropora colonies, representing 12 species, following full moon periods in September through November 2002. Gamete release was observed and inferred in four species of Acropora between 9 and 13 nights after the full moon (nAFM) in September 2002. Twelve Acropora spp. spawned gametes between 5 and 10 nAFM in October 2002, with six species spawning 7 nAFM and four species spawning 9 nAFM. In November 2002, spawning of egg and sperm bundles was observed and inferred in 27 colonies of Acropora austera, 6 nAFM. These are the first detailed records of spawning by Acropora corals in French Polynesia.