The reproductive biology, age and growth of the North American cyprinid, Notropis longirostris (Hay)

Notropis longirostris (Hay), the longnose shiner, in Catahoula Creek, Jourdan River drainage, Hancock County, Mississippi, was studied from May 1970 to May 1972. In 1971 reproduction occurred from late March into October, as indicated by gross examination of testes, breeding tubercles and breeding colour in males, and ovarian weights, measurements of ova, and gross examination of ovaries in females. Gross examination of ovaries in 1970 also indicated an extended reproductive season. Generally no significant differences from a 1 : 1 sex ratio or in the size of males and females in collections taken during the reproductive season were indicated. Males and females matured about the same size. Most females were sexually mature when 29–30 mm SL. The smallest female with mature ova was 28 mm; however, the majority of females did not have mature ova until 31–33 mm. The number of mature ova produced prior to spawning ranged from 15 to 129 for females 30.8–44 mm SL. There were significant differences in the number of mature ova with time, two peaks being indicated: the first in late March and April at the beginning of the reproductive period and the second in early July about the middle of the season. This conclusion is also supported by ovarian weight measurements and length frequency histograms. The mean diameters of mature ova ranged from 0.70–1.05 mm, averaging 0.90 mm, and were not significantly correlated with length. Most fish live about 1–1.5 years and do not live through two winters, indicating an annual turnover in the population. Maximum size was about 48 mm SL. Specific characteristics of the life history pattern of N. longirostris are discussed in relation to ecological conditions of the habitat.     

Age, growth and reproductive strategy of the snakehead, Ophicephalus striatus Bloch, from Sri Lanka

A total of 281 snakehead-lula, Ophicephalus striatus , collected between November 1982 and June 1983 from inundated rice fields and swamps in south-western Sri Lanka were analysed. Age determination by length frequencies and scale annuli revealed six age groups. An asymptotic length of 520 mm was estimated by the von Bertalanffy growth model.
The ova were assigned to four developmental stages and a maturity scale was developed for the females. Fast growing 2-year-old fish attain sexual maturity. The ovum size frequencies and occurrence of mature and spent fish indicate that this fish spawns during the south-west monsoon season. Fecundity estimates ranged from 1688 to 7146 ova. Total length and weight are equally useful for predicting fecundity.     

The effects of three different dietary protein levels on the fecundity in the guppy, Poecilia reticulata (Peters)

Experiments were performed to investigate the influences of dietary protein on fecundity in the guppy, Poecilia reticulata . No significant differences in total body length and standard length were found between females given food with different protein levels. A significantly higher total body weight was found both in females fed on 47% and 31% protein compared with females given 15% protein. The frequencies of females with only intrafollicular embryos or with only ova or both embryos and ova in the ovary were not significantly different between populations given different protein amounts. There was a significantly lower frequency of females without embryos and ova but with previtellogenic oocytes in the group given highest protein (47%) compared with the group fed on 31%. Significantly higher values of ovarian length, width and gonad weight were found among females given 47% protein compared with females fed on 15% protein. The ovarian height was significantly higher only in females given the highest protein amount when compared with the group fed on 31% protein. No significant difference of ovarian volume was found between groups given different protein contents. The average gonadosomatic ratio was highest in the groups fed on 47% protein. Significant correlations were found between gonad weight and total body weight of females in each group. Ovarian volume versus total body weight as well as versus gonad weight also yielded significant correlations in all groups. No significant differences of fecundity were found either between females given 47% and 31% protein or between females fed on 47% and 15% protein. A somewhat higher number of ova per individual fish was, however, observed among females given 31% when compared with females fed on 15% protein. The ovum size remained the same between groups given different protein contents. No significant correlation was found between fecundity and ovum diameter in the groups.     

Population structure,reproduction and laboratory behavior of the introduced Belonesox belizanus (Poeciliidae) in Florida

Synopsis The pike killifish, Belonesox belizanus, is native to Mexico and Central America and was introduced into Dade County, Florida in 1957. This study reports on the structure and reproduction of the Florida population and compares the species with other members of the family Poeciliidae. The mean standard length (SL) of mature females was about 103 mm. Most females larger than 75 mm SL contained yolked ova, fertilized eggs, or embryos. Mature males averaged about 72 mm SL, and most males larger than 55 mm SL were mature. The sex ratio was significantly skewed in favor of females among adults, but it did not differ significantly from 1:1 among immature fish. Average brood size was about 99, and there was a significant positive correlation of brood size with size of the parent female. There was no evidence of superfetation. Sizes and weights of embryos and neonates were the largest reported for the family. There was a significant decrease in mean embryo weight as development proceeded, indicating that developing embryos received little or no nutrient input from the maternal system after fertilization. The average interbrood interval of aquarium-held females was 42 days, and females stored viable sperm at least 47 days. Reproduction continued year round in the field. Laboratory-born neonates were immediately piscivorous and exhibited distinctive behavior associated with filling the swimbladder and with avoiding detection by predators.     

Maturation and spawning of a gobiid fish, Oligolepis acutipennis (Cuv. & Val.), from the south-west coast of India

The breeding biology of Oligolepis acutipennis (C. & V.), a gobiid fish abundant in the estuaries and brackish water tracts of the south-west coast of India was studied. Data on the intra-ovarian development of ova, the breeding season, spawning frequency, size at first maturity and sex-ratio were based on observations for 1 year. The size distribution of ova showed no significant variation between different regions of the ovary. The gonads were classified into five maturity stages. The sequence of development of ova to maturity indicated two batches of ova developed in a single ovary in a year. The minimum size at first maturity of females was less than that of males. Seasonal variation in gonad weight and the percentage occurrence of various maturity stages of gonads showed that the fish has a protracted breeding period in which two seasons can be recognized. The females dominate over males in numbers except in the non-breeding months.     

The effects of size, age and a cost of early breeding on reproduction in female mountain hares

Both age and size may influence female reproductive performance in mammals, and successful early reproduction may lead to reduced success at later attempts. The effects of age, size and early reproduction on distribution of reproductive effort throughout a single breeding season was examined in female mountains hares Lepus timidus L. Hind foot length was used as an index of body size, because, unlike body weight, it did not fluctuate with reproductive status. Fifty-six female carcasses were collected from March to October 1984, and their litters were assigned to one of three chronologically equal'litter periods'(1–3) of equal length. Whereas number of ova shed was always independent of age, large females shed more ova than did smaller females in litter periods 1 and 2. Prenatal mortality of ova and embryos was highest during litter period 1, when it was independent of age and size. Although prenatal mortality remained high in first year females in litter period 2, there was an overall decline through to the final litter period when it was negligible. Total number of young produced through the season increased with skeletal size in old females (age > 1), but not significantly in first year females. It is concluded that large size, rather than age, favours early reproduction in mountain hares. Every additional offspring produced in litter periods 1 and 2 reduced that female's production in period 3. After correcting for this cost of early reproduction the number of young produced in the final litter period also increased with maternal size.     

Distribution and reproduction of the southern lantern shark from New Zealand

Distribution, population structure and reproduction are described for the southern lantern shark Etmopterus granulosus at the Chatham Rise, New Zealand. Depth of capture for E. granulosus ranged from 744 to 1420 m, with highest catch rates between 800–1200 m. More than twice as many females as males were captured, and the majority of sharks caught were mature, indicating that there may be segregation according to sex and size class. Only 10 of 492 female sharks captured contained ova in uteri, and none contained embryos. The absence of pregnant females suggests that they move to another area or depth prior to pupping. Size of sharks captured ranged from 20·0 to 78·8 cm total length. Females began to mature at 62 cm total length, and males at 52 cm. There was no evidence of a seasonal reproductive cycle. Ovulation appeared to occur when ova reached a diameter of 40–45 mm. The average number of ova in mature females was 12·7. This information is crucial for assessing the impact of fisheries on E. granulosus populations.     

Growth and reproduction of Mesidotea entomon (Isopoda) in the northern Bothnian Sea

The life cycle of Mesidotea entomon sampled near the shore of Norrbyn in the northern Bothnian Sea, has been investigated. The species, a predacious brackish water isopod, had a three year life cycle. In May – June the juveniles were released from the female marsupium at a size of 3 mm. During the second summer size dimorphism became apparent, where the males were larger than the females. During the third summer and autumn the development of ova started in females. Maturation mostly occurred during late winter. Males matured before, and at larger sizes, than the females, 36.0 and 29.1 mm, respectively. The average fecundity was 153.2 and the females carried the eggs and embryos for several months before the release. Calculation of the survival rate for each year during the life-span revealed 0.05, 0.66 and 0.43, respectively.     

Spawning performance in North American minnows: direct evidence of the occurrence of multiple clutches in the genus Notropis

Pairs of laboratory–reared F₁, and F₂ males and females of Notropis leedsi were observed in aquaria. Analyses of spawning histories and ovum diameter histograms showing the pattern of ovum development demonstrated that females produced multiple clutches of eggs. Each clutch is comprised of oocytes which undergo synchronous development and are oviposited within a relatively short period of time. Examinations of collections from streams in Florida and Georgia showed that N. leedsi has a spawning season which lasts at least from May to September. Because the pattern of ovum development in wild-caught females was the same as that observed in laboratory females, we believe that our laboratory observations demonstrate processes which occur in the natural environment. A total of 193 spawning intervals was observed in 34 pairs kept at 22–26°C in the laboratory. The interspawning intervals ranged from 3 to 10 days, with a mean of 4.6 days and a mode of 4 days. The clutches ranged in size from 26 to 28 ova for females of 36.7–52.5 mm standard length.     

The pattern of reproduction in female Columbian black-tailed deer, Odocoileus hemionus columbianus.

Ovarian cycles and the pattern of reproduction in female black-tailed deer in British Columbia were ascertained largely through examination of the ovaries from 444 females. Cyclic development and degeneration of single follicles of ovulatory size occurred several weeks before first ovulation. As the breeding season approached, a second or third large follicle developed in each cycle but in 48% of adult females the follicles were at different stages of maturation. Those failing to rupture at first ovulation luteinized 1 to 2 days thereafter. The first ovulation of the season, in November, never resulted in a lasting pregnancy even though some ova were penetrated by spermatozoa and began to cleave. First ovulation was apparently 'silent' in five of seven females for their ova lacked spermatozoa. Of sixty-one pregnant females, fifty-nine conceived at second ovulation; the other two conceived at subsequent ovulations more widely spaced than the 8- to 9-day interval between first and second ovulations. The synchrony of ovulatory cycles among adult females was such that half of them ovulated for the second time in a span of 7 or 8 days. Primary CL that formed after first ovulation grew to an average maximum volume of only about 45 mm3, whereas those originating at second ovulation grew to twice that size within 5 to 8 days. First generation CL shrank from 35 mm3 to 10 mm3 within 2 days. They disappeared within 18 months but corpora albicantia persisted for the life of the female. The possible ecological significance of the reproductive pattern is discussed.     

Reproductive biology of the fanray, <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

The reproductive biology of the fanray, Platyrhina sinensis, was examined in Ariake Bay, Japan, from May 2002 until December 2006. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: male, 393 mm; female, 421 mm]. The present data support a distinct annual reproductive cycle for P. sinensis. The gonadosomatic index (GSI) for mature males showed a clear seasonal trend, declining from August to November. Histological observations showed that mature sperm in the testes occurred from August to November when monthly GSI declined. Concomitantly, pre-ovulatory ova were observed in females collected from August to November. These data indicate that mating, ovulation and fertilization occurred from August to November. Near-term embryos, neonates and recent post-partum females also occurred from August to November. Additionally, all post-partum females possessed large pre-ovulatory ova. Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Mature females become pregnant every year, and the gestation period is almost 1 year. Fertilized uterine eggs without macroscopic embryonic development were present throughout the annual reproductive cycle, indicating that P. sinensis utilizes embryonic diapause as its reproductive strategy. Both reproductive tracts of females were functional, and fecundity ranged from 1 to 12 with a mean of 6.0, increasing with TL.     

Reproduction of the blacktip sawtail catshark,Galeus sauteri,in the waters off northeastern Taiwan

The reproductive biology of blacktip sawtail catsharks,Galeus sauteri, in northeastern Taiwan waters was investigated. Male catsharks possessed paired testes producing spermatozoa, which were then stored in the epididymides all year round. No spermatophores were observed in the lower ductus deferens. Only the right ovary was functional in females, oogonia being formed in the ovarian cortex and then developing into mature ova. Ova exceeding 17 mm in diameter were ovulated. Pregnant individuals contained one eggcase only, in each side of the uterus. No hatched embryos were observed in such eggcases. The size at which 50% of blacktip sawtail catshark specimens were mature was 410–420 mm and 350–360 mm for females and males, respectively. The species does not have a well-defined reproductive season.     

Quantitative studies on Heterakis gallinarum infections in the common fowl, Gallus gallus L.

The fertility, mortality, and migration patterns of Hetarakis gallinarum were studied in chickens with concomitant Parahistomonas wenrichi infections. H. gallinarum females were found to produce approximately 936 ova per day, when 50 days of age, and a total of 34,000 to 86,000 ova in a lifetime. There was no evidence of differential mortality between the sexes, nor of a preference for either the left or the right caecal organ of chickens. Both male and female worms are capable of migrating between caeca, and are expecially prone to do so when in the absence of individuals of the opposite sex.     

Female reproductive pattern of Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) in Iskenderun Bay,Eastern Mediterranean

We studied the female reproductive pattern of Callinectes sapidus, which was introduced to the Mediterranean in the 20^th century. We assessed female size at first maturity, fecundity, and fecundity relationship to size in Iskenderun Bay, eastern Mediterranean, Turkey. Samples were collected between July 2014 and June 2015 using bottom trawling at depths ranging from 1 to 50 m. A total of 322 crabs were caught of which 308 (95.7%) were females including 116 ovigerous ones. The minimum carapace width of the mature females was 39.1 mm and the mean carapace width 123.8 mm. The carapace width of ovigerous females varied between 95.1 and 144.5 mm, with a mean of 120.3 mm. The highest number of ovigerous females was observed in July and August. Mean fecundity was 1.91 million (667,950–4,669,853) eggs per female. A weak positive linear relationship between fecundity and carapace width was noted, as well as a high correlation with total egg weight. In the eastern Mediterranean, maturity sizes of females were smaller than those in the native region of the species.     

Effects of delayed fertilization on embryo viability in walleye Sander vitreus (Mitchill): the role of maternal effects

The effects of delayed fertilization on embryonic viability in walleye Sander vitreus were examined using laboratory fertilization and incubation trials. Both fertilization success (survival to 10 h post-fertilization) and embryonic survival (from 10 to 168 h post-fertilization) generally declined with increasing ova storage time but trends varied significantly among females. Embryonic survival of individual egg batches was positively related to fertilization success. The slope of the relationship between fertilization success and ova storage time was negatively related to maternal fork length indicating that ova quality declined more rapidly with storage time for larger females than for smaller females. In contrast, the slope of the early embryonic survival v. ova storage time relationship was not significantly related to maternal size.     

Reduction in egg hatch after a sublethal dose of chlorfluazuron to larvae of the common cutworm, Spodoptera litura

Abstract.  The effects of a sublethal dose of chlorfluazuron on egg hatching in Spodoptera litura are examined under laboratory conditions. When LD₁₀ of chlorfluazuron is topically applied to newly moulted fifth-instar larvae of either sex, a significant reduction in both the number of eggs laid and subsequent hatching is observed after mating but no significant differences in daily of oviposition are observed when compared with the controls. In addition, examination of the unhatched eggs reveals that the number of unfertilized eggs is greater than those that were fertilized but there are significantly more unfertilized eggs laid by treated insects. Interference by chlorfluazuron, transferred by copulation through sperm fluids or ova, appears improbable. All the fertilized unhatched eggs in the treated crosses die at an earlier stage than those of the controls. In the female-treated crosses, the egg size is significantly reduced compared with the control or male-treated crosses. During mating, the treated-males transferred significantly lower-weight spermatophores into the females. The weight of spermatophores transferred by untreated males is the same to both treated and untreated females. The duration of mating is not affected by chlorfluazuron treatment.     

The effects of population density on fecundity and fertility in the guppy, Poecilia reticulata (Peters)

Experiments were performed to examine the influence of population density on the fecundity and fertility in the guppy, Poecilia reticulata . The frequency of females with only ova or with different combinations of reproductive units and developmental stages in the ovary was significantly different between different densities but not between females with one and two gestations from the same population density. The ovarian width of females with one gestation from the lowest density was significantly larger than in the highest population density. Gonad length and height and ovarian volume of females with two gestation periods were larger in the lowest compared with the highest density. After one gestation, females at the lowest population level had greater ovarian length, height, gonad weight, width and volume compared with those from the higher density. Ovarian length, height and volume and gonad weight were also significantly greater among females of two gestation periods in the lowest than in the second lowest density. The average gonadosomatic ratio was highest in the lowest population density. A significant correlation was found between gonad volume and total body weight and between gonad volume and ovarian weight of females at every population level. This was also the case when ovarian weight vs. total body weight was examined in each population density. Only at the lowest population level was there a significant correlation between fecundity and total body length and between fertility and body length. A significant relationship was also found between gonad volume and total body length and between gonad weight and body length at the same population level. No significant difference of fecundity and ovum size was found between females of one and two gestation periods from the same density. Fecundity and fertility were significantly higher among females of one and two gestation periods from the lowest than from the highest density.     

Reproductive biology of the guitarfish <Emphasis Type="Italic">Rhinobatos hynnicephalus</Emphasis> (Batoidea: Rhinobatidae) in Ariake Bay,Japan

Size at sexual maturity, reproductive cycle, and fecundity of the guitarfish, Rhinobatos hynnicephalus, were examined in Ariake Bay, Japan. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: males, 431 mm; females, 476 mm]. Monthly gonadosomatic indices of males decreased abruptly from July to August. Histological examinations confirmed the presence of mature spermatozoa in the testes in July, with semen in seminal vesicles in July and August. Preovulatory ova were observed in females with near-term embryos in August. Parturition occurred in August, immediately followed by mating, ovulation, and fertilization. Gestation period is approximately 1 year. Fertilized uterine eggs without embryonic development were present throughout the annual reproductive cycle. Embryonic development began in June and ended in August, indicating that R. hynnicephalus undergoes embryonic diapause (9 months). Fecundity increased with TL and ranged from 1 to 9 (mean, 4.4) embryos per litter.     

Sexual selection drives the coevolution of male and female reproductive traits in Peromyscus mice

When females mate with multiple partners within a single reproductive cycle, sperm from rival males may compete for fertilization of a limited number of ova, and females may bias the fertilization of their ova by particular sperm. Over evolutionary timescales, these two forms of selection shape both male and female reproductive physiology when females mate multiply, yet in monogamous systems, post-copulatory sexual selection is weak or absent. Here, we examine how divergent mating strategies within a genus of closely related mice, Peromyscus, have shaped the evolution of reproductive traits. We show that in promiscuous species, males exhibit traits associated with increased sperm production and sperm swimming performance, and females exhibit traits that are predicted to limit sperm access to their ova including increased oviduct length and a larger cumulus cell mass surrounding the ova, compared to monogamous species. Importantly, we found that across species, oviduct length and cumulus cell density are significantly correlated with sperm velocity, but not sperm count or relative testes size, suggesting that these female traits may have coevolved with increased sperm quality rather than quantity. Taken together, our results highlight how male and female traits evolve in concert and respond to changes in the level of post-copulatory sexual selection.     

Costs of parental care in the gastropod Conus pennaceus: Age-specific changes and physical constraints

Summary Age-specific changes in the allocation of reproductive energy to protective capsules, ova and intracapsular fluid are documented for the marine gastropod Conus pennaceus. As female snails grow in shell length they produce larger capsules with thicker and stronger walls. Because large capsules contain lower densities of ova than do small ones, growing females must increase the number, as well as the size, of egg capsules they produce. As a result of this pattern of ova packaging, per ovum costs of encapsulation (parental care) increase with increasing female size and age. The data suggest that the number of embryos a capusle can support may be limited by respiratory constraints related to capsule surface area or wall thickness. As capsule size increases, surface/volume ratios decline and capsule wall thickness increases. Either of these processes should result in a reduction in net gas transport per unit of capsule contents.