Annual cycle in female Three-spined sticklebacks (Gasterosteus aculeatus L.) from an upland and lowland population

The annual cycles in female Three-spined sticklebacks from an upland (275 m) and a lowland (25 m) population were compared. The average length and weight of the lowland females were greater, but in both populations growth was checked in winter and again in the breeding season. Both populations also showed a winter decline in condition followed by a sharp increase in spring associated with the maturation of the ovaries. The hepato-somatic index of the females also increased during the spring, but the dry matter content of the liver declined during the spring and early summer. Lowland females had larger livers than the upland fish. In both populations average gonadosomatic index increased steadily throughout the winter, then abruptly in spring. The lowland population bred from May to early August, but the upland population bred only in May.
The energy content of the carcases of females was lowest in winter and again during the breeding season whereas the ash content showed maxima at these two periods. Lipid and glycogen analyses of the carcase, liver and ovaries also suggested that winter and the breeding season were periods of depletion from the carcase and liver, but not from the ovaries.
The observations indicate that the ovaries are to some extent insulated from fluctuations in resource availability. This supports experimental studies which indicate that egg production in the female stickleback can be subsidised by depletion from the carcase and liver when necessary.     

Effect of food on the growth of carcase, liver and ovary in female Gasterosteus aculeatus L.

The effect of ration size on the growth of the carcase, liver and ovary in female three-spined sticklebacks, Gasterosteus aculeatus L., was studied experimentally at monthly intervals throughout the annual reproductive cycle. Temperature and photoperiod during each experiment corresponded to the average, natural conditions for that month.
Growth of the carcase was sensitive to ration in all months. At a given ration, the growth rate of the carcase was relatively constant. The water content of the carcase was inversely correlated with ration size. Growth of the liver was also sensitive to ration, but the sensitivity varied in different phases of the reproductive cycle. High rates of weight loss occurred in the liver under starvation, but at maximum rations the liver showed high rates of weight gain particularly in the post-spawning period. Growth of the ovary was relatively insensitive to ration but directly reflected the changes occurring naturally in the reproductive cycle.
It is suggested that the liver acts as a buffer between the carcase and the ovary and this helps to insulate the ovary from the immediate effects of fluctuations in food supply.
The growth rates of the carcase and liver may provide useful indices of the rate of food consumption in natural populations. Although, if the liver is used, its growth has to be interpreted in the context of the annual reproductive cycle.     

Some population dynamics of the Bank vole, Clethrionomys glareolus and the Wood mouse, Apodemus sylvaticus in mixed woodland

The population dynamics of Clethrionomys glareolus Schr.and Apodemus sylvaticus (L.) in mixed woodland in County Durham, were studied from March 1963 to January 1965. Two areas of 0.9 ha (2.25 acres) each were trapped monthly and information was obtained on population size, reproduction, survival and growth from marked animals.
Clethrionomys populations increased from June to an autumn peak; then declined, at first rapidly, but then more slowly in winter, before reaching a spring trough. The breeding season of Clethrionomys was from May to December; juveniles were caught from mid-June to December. Survival was in general poor during the breeding season but good at other times. Survival of young born early in the summer was particularly good on one of the areas and some individuals lived long enough to breed in two successive years. On both areas young born early in the year matured rapidly and bred in the year of their birth. Young born in late summer and early autumn ceased growing at a weight of about 14.5 g, remained immature, and formed the bulk of the overwintering population. Growth was completed at the time of sexual maturation the following spring.
Trapping failed to provide adequate samples of juvenile Apodemus in summer to account for subsequent recruitment. The possibility that a substantial proportion of the adult population of this species was also either trap shy or had emigrated temporarily is discussed. Breeding occurred from April until the following January, but the numbers trapped remained very low throughout the early months of the breeding season. Large scale recruitment of young fecund animals into the trap-revealed population occurred during the autumn. Apodemus males continued to grow rapidly during the winter.     

Annual variation in energy reserves in male three-spined stickleback, Gasterosteus aculeatm L. (Pisces, Gasterosteidae)

Wet and dry weights of tissue were measured and concentrations of glycogen, lipid and protein were estimated for the liver, gonad and carcass of male sticklebacks from an annual population collected each month over one complete year. In young-of-the-year there is one period of rapid weight gain, in all three body regions (liver, carcass and gonads) but particularly of the carcass, in the autumn and a second in spring and early summer. This is accompanied by an increase in the water content of all three body regions. The gonadosomatic index also increases sharply in spring and early summer. Young sticklebacks accumulate lipid and glycogen slowly during the autumn and winter of their first year of life and more rapidly from late winter to early summer. Thus, the period of most rapid accumulation of these reserves coincides with the time when body weight and gonad maturation are also increasing sharply. Lipid and glycogen levels fall during the reproductive season in those males that breed, so that by July they are reduced to 43% and 37% (respectively) of their peak values in May. Levels of protein increase throughout the year as the fish grow, but in breeding males by July the concentration of protein in the carcass falls to 70% of pre-breeding levels. Breeding males therefore reach the end of the reproductive season with their total energy reserves severely reduced, and consequently they suffer a very high mortality. In contrast, adult males that fail to reproduce survive beyond the breeding season. They continue to gain weight and to accumulate lipid and glycogen from August to September, but these energy reserves fall (to levels comparable to those of post-breeding fish) in December, when these fish probably die. These results demonstrate that in male sticklebacks, growth and gonad maturation can be sustained in parallel with the accumulation of energy reserves, which are subsequently extensively depleted as a result of reproductive activities.     

Reproductive phenology of the Azorean rock pool blenny a fish with alternative mating tactics

Both male and female Parablennius sanguinolentus parvicornis were ready to mate by the end of May. Seventy-five per cent of the 1-year-old males were mature, but only 25% of the females reached maturity at this age. In females, gonads formed an increasingly greater proportion of the total weight with age, but in males the proportion decreased. A bimodal distribution of gonadosomatic indices classes was observed in 2-year-old males (intermediate size), which reflected the lower opportunity that intermediate size males have to spend the ejaculates than have the younger and older males. The liver played an important role in the storage of energy before the reproductive season and reserves were utilized during the breeding season. Physical condition was at its lowest in July in both sexes, but in May, just before the breeding season began, large maturing females had significantly lower eviscerated condition than males. This could be due to females investing in oocyte development, while the priority for the males was to reserve their energy for the parental activities to come. In both males and females, older and bigger animals had lower hepatosomatic and body conditions than younger ones.     

Gonad development and sperm motility of the diving beetle Cybister brevis Aubé, 1838 (Coleoptera: Dytiscidae) in response to seasonal changes in Japan

Gonad maturation in wild Cybister brevis Aubé, 1838 from Japan was investigated to determine the physiological mating season. Breeding experiments showed that hatching occurred from May to September, and the peak was observed in July. The gonadosomatic index (GSI) in collected females (ovary development) showed the highest value in May. The GSIs were low in other seasons. On the other hand, the GSIs in collected males (testes and accessory glands) remained at constant values during the experimental period. Interestingly, high sperm motility was exhibited in May and September, whereas it was low in December and March. This indicates the maturation difference between females and males. Females mature only at the beginning of the breeding season (May), but males do so from May to September. This result suggests that males have a wide-ranging maturation period and earlier sexual maturation than females, ensuring a successful fertilization.     

Reproductive cycles in littoral populations of Choromytilus meridionalis (Kr.) and Aulacomya ater (Molina) with a quantitative assessment of gamete production in the former

Changes in ovary weight and ovary smears of Choromytilus meridionalis (Kr.) and Aulacomya ater (Molina) showed the breeding season to extend throughout the spring and summer months (Aug.-Feb.). Release of gametes was intermittent with regeneration of the gonad after peak spawning periods. Populations spawned synchronously or asynchronously with an average of 50% of individuals spawning at any one time. The end of the breeding season was marked by gonad depletion and resorption of gametes. Gametogenesis followed rapidly and large quantities of reserve material were not deposited in the mantle during the winter months as in Mytilus edulis.The False Bay population of Choromytilus meridionalis has predominantly synchronous spawning and gamete production for two breeding seasons was calculated. The quantity of gametes released varied annually and was not significantly different in males and females. Mean gamete production was calculated as 1.17 × standing crop expressed as dry flesh weight, or 1.33 × energy value of the standing crop per annum.     

Seasonal effects on fertility and ovarian follicular growth and maturation in camels (Camelus dromedarius).

Camels are said to be seasonal breeders, but the extent to which season interferes with food supply to affect ovarian function is not fully documented. Hence, the three aims of this study were: (1) to define the breeding season of camels maintained in semi-arid conditions in southern Morocco; (2) to relate the proportion of females with active ovaries (i.e., with follicles > 5 mm), with ovulatory (11-17 mm) or cystic (> 18 mm) follicles to age and body conditions score; (3) to study the consequences of the interactions between age and body conditions score on the proportion of females ovulating and conceiving; and (4) to compare follicular maturation, using in vitro steroidogenesis by intact follicles as a marker during the transition into the breeding season (October) and peak breeding season (March). There was a clear breeding season in the two flocks studied, since over 80-90% of the matings occurred during the period from mid-November to mid-April. Collection of ovaries at slaughter (n = 238) demonstrated a significant seasonal effect on the proportion of females with active ovaries (increasing from 73.5% in October-December to 89% in January-May), but no changes in the proportion of females with ovulatory follicles. Lean females (BCS < 2.5) had a delayed initiation of ovarian function in October-December. In addition, the proportion of females with cystic follicles was also affected by season (peaking during April-May). Neither age nor body condition modulated the frequency of cysts. Finally, the proportion of females conceiving increased steadily as season progressed (peaking at 57% in April-May). Body condition score did not affect this proportion, but young females (< or = 5 years old) had a low ability to conceive. Morphological features of large follicles were unaffected by season. Ovulatory follicles contained around 10(7) granulosa and theca cells. In vitro testosterone output by intact follicles was unrelated to follicle size and season. In vitro oestradiol output increased with increasing follicle size and was larger in follicles obtained during peak breeding season than at its initiation. This may indicate that early breeding season follicles display a low aromatase activity in their granulosa cells. Whether the low oestradiol output of early breeding season follicles is resulting in the low fertility observed at this period remains to be determined.     

The reproductive biology of Lutjanus fulviflamma (Forsskål,1775) (Pisces: Lutjanidae) in Kenyan inshore marine waters

The testicular and ovarian maturation cycle of thedory snapper, Lutjanus fulviflamma(Forsskål) (Osteichthyes:Lutjanidae), acommercially valuable species in the western IndianOcean, is described macroscopically. The ovary wasalso studied microscopically. L. fulviflammahas one prolonged spawning season which begins fromNovember/December, lasting till April/May. Discontinuous spawning is established by (i) temporalvariation in the relative weight of testis andovaries, (ii) a seasonal occurrence of various maturitystages and, (iii) a seasonal occurrence of developingfish in the samples. Using volumetric andhistological techniques, the fecundity of this specieswas determined at 51,000 to 460,000 (mean: 167,000)oocytes in fish of between 17 to 30 cm total length,respectively. Oocyte recrudescence in the ovary isasyncronous, but the number and size of batches ofeggs released in a single spawning season are yet tobe determined.     

Reproduction in males of the feathertail glider Acrobates pygmaeus (Marsupialia)

Between 1984 and 1986, reproductive tracts were collected from 17 male Acrobates pygmaeus (Shaw) from south-eastern Australia and the anatomy of these tracts is described. The prostate is heart-shaped and the arrangement of its three segments, anterior, central and posterior, is different to the patterns described for other marsupials. The testes are large in proportion to the body size but their structure and that of the remainder of the tract is typical of other marsupials. The sperm morphology is similar to that of the Phalangeridae and Burramyidae.
Seasonal cycles were found in the sizes of testes and prostates. Increases in testes sizes, starting in April or May, were associated with increases in seminiferous tubule diameter and Leydig cell size. The weight of the prostate increased rapidly to a short peak in June when the testes also reached maximum weight. The first births occurred approximately one month later in this population. Following this peak, both the testes and the prostate decreased in size and had returned to the original weights by January. The beginning of this period when the testes and prostate were small coincided with the cessation of births in the population and was marked by an interruption in spermatogenesis.
Males born early in a breeding season mature before the start of the next breeding season, but males born at the end of a breeding season may not mature until the second season after their birth, at which time they are approximately 18 months of age.     

Sexual cycle properties and changes in carotenoid levels in ovary of Japanese mitten crab <Emphasis Type="Italic">Eriocheir japonica</Emphasis> from rivers of Primorye

The sexual cycle of Japanese mitten crab Eriocheir japonica (de Haan, 1835) in its northern range in water bodies of the Primorye proved to have specific properties including changed seasonal dynamics of gonad maturity stages, delayed spawning period, and reduced breeding season. The ovary color regularly changed during the gonad growth in females, which was accompanied by an increase in total carotenoid content from 1.4 to 22.2 mg/100 g tissue and by changes in the proportion of major pigments. The relative content of the carotene fraction notably decreased and that of astaxanthin slightly decreased during gonad maturation. The revealed changes in carotenoid levels in the ovary point to the activity and significance of pigment metabolism in the reproductive cycle of E. japonica.     

Biochemical composition of ovary, embryo, and hepatopancreas in the grapsoid crabs Armases cinereum and Sesarma nr. reticulatum (Crustacea, Decapoda)

Biochemical composition of ovary, embryo, and hepatopancreas tissues in wild populations of Armases cinereum and Sesarma nr. reticulatum were monitored during the reproductive season. Total lipid, carbon, nitrogen, C:N ratio, and water concentration of the ovary, hepatopancreas and embryos were quantified over the course of ovarian maturation. Ovary nitrogen concentration decreased as ovaries matured. Ovary lipid and carbon concentration differed significantly over the course of ovarian maturation for both species, but there was no relationship between the concentration or total content of hepatopancreas lipid and the stage of ovarian development in females. Neither species showed a relationship between measures of hepatopancreas lipid and the gonadosomatic index. There was also no simultaneously measurable net decrease in mass of the females' hepatopancreas. Lipid demands of ovarian maturation thus appear to be met in large part by increased dietary intake rather than by substantial draw down of pre-existing lipid stores from the hepatopancreas. While these temperate grapsoid crabs live with putatively fluctuating quality and quantity of food resources, no evidence could be found to demonstrate depletion of lipid concentrations in the hepatopancreas concomitant with ovarian maturation.     

Temporal changes in fat and protein levels in the tropical Anabantid Trichogaster pectoralis (Regan)

Samples of a wild population of the Anabantid Trichogaster pectoralis (Regan) were taken during and after one of the two main breeding periods of the year. Carcasses of both sexes and female gonads were analysed for fat, protein and carbohydrate. Carbohydrates were present in insignificant amounts in all tissues. The fat content of the ovary proved to be high (over 30% of wet weight) and, as a result, ovarian energy in a ripe female formed a substantial proportion of the total energy content of the fish. However, it did appear possible for females to develop large ovaries without depleting the carcass fat stores.
Although protein levels in the carcass were significantly higher in 1 month, relative to fat levels, protein levels remained fairly constant during the period of study. Conversely fat levels showed marked fluctuations throughout the breeding period, being high at the start of the breeding period, low towards the end, finally rising again 1 month after most fish had terminated breeding. The range of fat levels appeared to be independent of the gonadal state of the fish at capture and seemed more closely related to month of capture. Two explanations are suggested; (1) changes in food availability over the period in question and/or (2) if repeated spawnings occur this could deplete fat reserves in the carcass.
In this species fat is stored largely in the muscle but some is stored around the coiled intestine. A visual scoring system was used to assess the extent of this fat deposition and it was found that the fat score was correlated with the level of fat in the carcass. Thus the level of fat around the intestine, although insignificant relative to carcass fat, could be used as a method of assessing the fatness of a fish.     

Body weight, gonad development and moult in the Tawny owl (Strix alum)

Gonad development, moult and seasonal changes in body weight and composition in the Tawny owl Strix aluco were studied by examining the carcasses of 369 owls (mostly road casualties) supplemented by 112 weights of live birds. In breeding females laying was preceded by the accumulation of fat and to a lesser extent protein which meant that they weighed more at this time (February/March) than at any other. Females declined in weight after laying but were still heavy during incubation. In contrast, males and non-breeding females did not increase in weight before the start of the breeding season. Juveniles reached or even exceeded adult weight well before independence due to the deposition of fat. Even after the exclusion of diseased or contaminated individuals, 9·4% of the birds examined were identified as starving; most of these were in the autumn and were probably newly-independent young wandering in search of territories. In both sexes gonad maturation was of brief duration coinciding with the period (mid-March to mid-April) in which eggs are normally laid. Ovarian growth was biphasic. In the three months prior to the breeding season ovarian condition in different birds was positively correlated with body weight and it appeared that the largest ovarian follicles of females in poor condition failed to attain the size from which rapid growth to final ovulation occurs. in males testis size in the breeding season was correlated with pectoral muscle weight (an index to protein condition) but not body weight. The majority of adults commenced wing moult in June. The average duration of primary moult was estimated to be 77 days. Healthy birds replaced the primaries of both wings at the same rate but most diseased birds moulted asymmetrically and/or out of season. First-year birds renewed their body feathers between September and November. In the Tawny owl territory establishment, breeding and moult are temporally separated.     

Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia

Labeo horie Heckel is increasingly becoming commercially important in Lake Chamo but its reproductive biology in the lake is not well enough to guide its management. Sex ratio, breeding season, length at first maturity and fecundity of L. horie were studied from 1197 fish samples collected between August 1998 and October 1999 in Lake Chamo, Ethiopia. The sex ratio was significantly different (χ ² = 12.12, P < 0.001). The peak‐breeding period was during the rainy months of March to May, during which time more than 90% of both sexes had ripe gonads. The size at maturity ( L _m50 ) of males was 52 cm while the L _m50 of females was 62 cm. The smallest ripe male in the catch was 46.7 cm and weighed 890 g while the smallest ripe female caught was 49.5 cm and weighed 1145 g. The weight of ripe ovaries ranged from 54.3 g to 991.8 g and contained between 68,400 and 1,320,400 eggs. Relative fecundity ranged between 60 and 290 eggs per g of body weight. The relationships between fecundity and total length and between fecundity and total weight were curvilinear, while the relationship between fecundity and ovary weight was linear. L. horie conformed to the general pattern of reproduction in a tropical environment where peak‐breeding activity occurred during the rainy season. In order to protect the spawning population, fishing pressure should be minimized during breeding time at the shallower littoral regions.     

Reproductive effort and efficiency in the female common goby, Pomatoschistus microps (Krøyer) (Teleostei: Gobioidei)

Reproductive effort and efficiency are terms which together help to describe the reproductive investment of spawning fish. In this paper they are applied to a small and abundant inshore fish, the common goby, Pomatoschistus microps (Kroyer), based on data collected from the wild, and by modelling likely breeding patterns. Wet calorimetry was used to determine the energy content offish tissue, and this allowed reproductive effort to be expressed as both an energy and a weight ratio of gonad to somatic body. The gonadosomatic index (GSI) calculated as an energy ratio was greater than that calculated as a dry "weight ratio". For ripe females the GSI (dry weight) at the onset of breeding was 67.5%. Theoretical and observed values of the maximum number of egg batches laid by a single female during a 16-week breeding season are 9-10, and this corresponds to a total caloric investment of almost 12 kJ. Estimates of the reproductive efficiency, using the dietary energy content during the breeding season, range from 28.2% to a maximum of 44.0%. These values are among the highest calculated for a fish species, and are in keeping with the long and intensive breeding strategy observed in the wild population.     

The seasonal partitioning of energy in an estuarine fish, the common goby, Pomatoschistus microps Krøyer

The common goby, Pomatoschistus microps , is an abundant brackish water species which has an appreciable role, both as predator and prey, in the ecosystems of British estuaries. The partitioning of energy within each sex is described and discussed, and energy values are provided for the gonad, liver and carcass throughout almost the entire life of one year class. Partitioning of resources within the body at different times of the year shows considerable variation, not only with time but also between the sexes. In particular, the energy content of the male gonad during the spawning season is never more than 3.7% of that of the female. Important aspects of the biology of the species which relate to energy partitioning are maturation at an early age, high reproductive investment, high stochastic mortality, and death usually after a single breeding season.     

Seasonal changes in condition, reproduction and fecundity in the wild European rabbit (Oryctolagus cuniculus)

A total of 1248 rabbits ( Oryctolagus amiculus ) were shot on farmland in Cambridgeshire, UK over a period of three years. This provided pooled estimates of changes in reproductive and body condition and of fecundity during the annual cycle. Both males and females showed a significant annual cycle in reproductive condition as indicated by changes in the size of the gonads and accessory glands of reproduction. No females were pregnant during October, November and December, but males with active spermatogenesis were found during every month of the year. The distribution of pregnancies through the year showed that the reproductive season varied greatly between individuals. Peak fecundity occurred during April, May and June. On average, each female conceived 23.9 and suckled 17.2 young per breeding season. Proportionately more young died during the early stages of the reproductive season. The body weight of adult males, but not of females, varied seasonally. Body condition (kidney fat index) in adults was maximal at the start of the breeding season and minimal at the end.     

Sexual Maturation, Annual Reproductive Cycle, and Spawning Periodicity of the Shore Scorpionfish, Scorpaenodes littoralis

The ovarian structure, sexual maturation, annual reproductive cycle, and spawning periodicity of the shore scorpionfish, Scorpaenodes littoralis, in Uchiura Bay, central Japan, were examined using specimens collected between May 1995 and March 1998 and fishes reared in laboratory. The ovarian stroma and blood vessels run longitudinally through the center of each ovarian lobe. The ovarian peduncles radiate from the central stroma. During the spawning season, gelatinous material is secreted from the epithelia of both the ovarian peduncle and ovarian wall, and the epithelia show morphological changes accompanying the ovarian maturation cycle. The minimum standard length at maturity was 55.2mm for males and 40.2mm for females. Males with mature testes were collected from March to November. Females in the mature or post spawning stages were collected between May and October, when the mean gonadosomatic indices were also high. This indicates that the spawning season of this species occurs between May and October. Four successive types of oocytes were grouped in the mature ovary, comprised of mature, late and early vitellogenic and previtellogenic oocytes respectively, suggesting that this species is a multiple spawner. Four captive females spawned repeatedly at intervals of 2–8 days over a prolonged period (4–8 months); a 2-day spawning interval was the most common for all females. This suggests that female S. littoralis have a 48-h spawning cycle in captivity.     

Ovarian growth,induced by eyestalk ablation during the prebreeding season,is not normal in the crab,Paratelphusa hydrodromous (Herbst)

In Calicut populations of P. hydrodromous, the ovary is not refractory during September—November of the prebreeding season; it is inhibited from developing apparently by a gonad-inhibiting hormone(s) contained in the eyestalks. The prevalent tendency in Paratelphusa during the prebreeding season is to reproduce, and not to moult. The precocious ovarian growth induced by eyestalk removal during this season is biochemically impoverished, possibly due to uneven oocyte development, which in turn may be caused by the unpreparedness of a section of the population of oocytes for vitellogenesis. The ovary appears to have to pass through a period of oogonial proliferation under the influence of the moult-precipitating hormones during the moulting season, and subsequently through a period of oocyte differentiation during the prebreeding season, for normal vitellogenesis during the breeding season.