Sex ratio and sex expression in an urban population of the silver moss,Bryum argenteum Hedw.

ABSTRACT

Introduction. A well-supported pattern among dioicous bryophytes is male rarity. However, few assessments of bryophyte sex ratios have been made across environmental gradients to assess the role of environment in shaping population sex ratios.

Methods. We systematically surveyed 200 shoots from a 20?m² urban population of Bryum argenteum, and regenerated each shoot apex until sex expression occurred (up to 315 days).

Key results. Female shoots outnumbered male shoots 132 to 68, giving a sex ratio of 1.94♀: 1♂. The female bias was found in two transects in higher light environments but not in the third transect, which had a lower light level and an equal sex ratio. Female shoots took longer than male shoots to reach gametangial induction (122 vs. 60 days) and longer to produce 5 inflorescences (120 vs. 80 days). Male shoots produced an average of 10× the total number of inflorescences compared to female shoots (34 vs. 3.5 inflorescences). Despite producing more inflorescences, male plants also produced more regenerant shoots, thus contradicting the prediction that a higher prefertilisation reproductive effort in males trades off with vegetative proliferation. Female plants harboured significantly more associated microbes than male plants.

Conclusions. Our results support the role of light in influencing sex ratios in this species, suggest that trade-offs between reproduction and vegetative growth may not be strong for males, and indicate a potential role of a sex-specific microbiome in influencing sex ratios.     

Laboratory and field studies on the reproductive ecology of Parocneria orienta (Lepidoptera: Lymantriidae) in China

To lay a foundation for the monitoring, prevention and control of Parocneria orienta, a pest moth in China, we investigated the reproductive ecology of P. orienta, including the environmental factors affecting reproduction and the effects of pheromones in field traps. The results showed that the mating duration is shorter when the temperature is higher, with the optimal temperature range for P. orienta reproduction being 22–27°C. The sex ratio had an effect on the male mating capacity, which significantly increased when the sex ratio was ♀:♂ ≥ 3:1. The average number of matings was 2.44 for males, while female P. orienta mated only once in a lifetime. Males were more attracted to virgin females than to mated females, and the temperature and light period had an effect on the release of sex pheromones by females. Field trap tests using virgin females supported the results obtained in the laboratory, showing that the release of sex pheromones by P. orienta follows a distinct circadian rhythm.     

SEX-RATIO AND REPRODUCTIVE VARIATION IN THE MISTLETOE PHORADENDRON JUNIPERINUM (VISCACEAE)

Despite the fact that many parasitic and hemiparasitic plant species such as mistletoes are dioecious and occur in both the new and the old world, few data exist on variation in the sex ratio and allocation to reproduction in these taxa. We investigated 1) the sex-ratio of the xylem-tapping mistletoe Phoradendron juniperinum in relation to its age and position within the canopy of its host tree Juniperus osteosperma, and 2) reproductive effort in relation to the gender and age of mistletoe plants. Our surveys showed that P. juniperinum has a male-biased sex ratio. Despite this predominance of male individuals, females lived longer and had a greater reproductive effort than did males. A statistical analysis of the age distribution data indicated that the peak in the frequency of reproductively mature individuals was later in females than in males. These gender-specific distributions may have resulted 1) from sequential hermaphroditism (age-specific sex switching), or 2) because the average age of peak reproduction is later in female individuals. Because sex is genetically determined in a closely related genus of mistletoe and because we have no data to indicate sex switching in this species, we feel that our data support the interpretation that female individuals, on average, show a peak in reproductive vigor at an older age relative to males. While delayed reproduction in females may be favored because reproductive effort and success appear to be age-dependent in females of this species, both sexes can become reproductively mature relatively early in life. Further, because 1) allocation to reproduction as a function of age increases more rapidly for females of this species relative to males, and 2) because there may be a higher resource cost associated with reproduction in females, we hypothesized that female individuals would be more abundant in the best quality locations within the host tree so as to maximize the opportunity to meet those costs. In spite of the association between gender and some host characteristics, there was no indication that female plants were located in sites most favorable to either their carbon or water balance. We discuss reasons why this may be the case.     

Some factors affecting reproduction and sex-ratio of the predacious mite Amblyseius deleoni (Muma and Denmark) (Acari: Phytoseiidae)

Abstract

Several factors were examined to determine their effect on the reproduction and sex ratio in the predacious mite Amblyseius deleoni (Muma and Denmark), in the laboratory. The factors investigated included multiple matings, duration of copulation, capacity of male for mating in excess of females and age of mating females and males. The factors included also, the host plant leaf texture, food deprivation during immature and adult stages, and prey (Tetranychus urticae Koch) density. The results indicated that females of A. deleoni require multiple matings to maximize their reproductive potential, also when copulation was allowed for increasing periods of time, there was a gradual increase in total egg production and oviposition period. A male showed a high reproductive ability for more than 15 days and was able to mate more than once in excess of females. Age of females has an influence on fecundity and sex ratio; old females decreased egg production and produced proportionally more male progeny compared with young females. Similarly, the highest number of eggs deposited per female A. deleoni was reported, when female mated with a young male (0-day old). In addition, males of A. deleoni (at any age) were able to inseminate the females. Results from host plant leaf texture indicated that guava leaf gave the highest reproduction rate, while the fig leaf gave the least female fecundity. Neither the reproductive rate nor the sex ratio of the progeny of females crossed by normal or experimental males had been influenced by the food deprivation during immature stages. A significant lower fecundity was recorded on female's A. deleoni when exposed to different food deprivation programmes during adult stage. The number of eggs laid by the predator female increased with increasing prey density of T. urtice to a maximum of 2.04 eggs deposited per day at a prey density of 30 protonymphs of T. urticae as a prey. As the level of prey density was increased, there was a shift in sex ratio towards an increased proportion of females.     

Patterns of resource allocation in male and female plants of Rumex acetosa and R. acetosella

Summary Patterns of resource allocation in the dioecious Rumex acetosa and R. acetosella were investigated. Males were found to allocate more to reproduction during flower production than females, whereas females invested considerably more in reproduction during seed production. Altogether, females allocated both a higher total amount and a higher proportion of energy to reproduction than did males. By regression analysis, the influence of plant size on reproductive effort was examined separately for males and females. The results indicated that while reproductive effort is sometimes lower for tall plants than for small plants, size-independent effects have a greater influence on reproductive effort than size distribution. An analysis of variance was conducted to investigate the effects of population, season, sex and their interactions on plant size, and an analysis of covariance was used to study differences in resource allocation patterns. Different interaction effects were found to be most important in the two species of Rumex.     

Life history strategy of Leptinaria unilamellata (d'Orbigny, 1835) (Mollusca,Pulmonata, Subulinidae)

Abstract

Life history theory predicts that the patterns of resource allocation in animals are associated with different strategies, selected in the course of evolution. In the present study, the life history of Leptinaria unilamellata was characterized under laboratory conditions. We determined the growth, reproduction, and longevity patterns of this species and elucidated the strategy related to the development of embryos, through direct observations and examination of the morphology of the gravid uterus. Furthermore, we attempted to analyze the glycogen and galactogen contents of the albumen gland, digestive gland and cephalopedal mass in order to understand energy allocation to life history traits, for three life stages. Leptinaria unilamellata's life history is characterized by great longevity, a short juvenile phase, early sexual maturity, and repeated reproductive events, with little reproductive effort at each event and some mortality shortly after the first reproduction. In the terraria, we found juveniles but no eggs. However, the results of the anatomical study showed no morphological connection between the embryos and the parental organism. Thus, this species should be described as ovoviviparous rather than viviparous. Egg retention in the parent organism is the primary cause of the release of juveniles, instead of eggs, enabling the offspring to withstand environmental stress. The higher quantity of galactogen found in the adults' albumen gland, as compared to juveniles and senescent individuals, as well as the ratio of glycogen to galactogen, reveal the allocation of energy to reproduction rather than to growth. The remaining energy is directed to the maintenance of omeostasis. Such pattern was confirmed by the low levels of glycogen and galactogen observed in the senescent stage, compared to the juvenile and adult stages. In the life strategy of L. unilamellata, the distribution of the reproductive effort among many events associated with ovoviviparity indicates a long-term investment in reproductive success.     

What lies beneath? Population dynamics conceal pace‐of‐life and sex ratio variation,with implications for resilience to environmental change

Life‐history and pace‐of‐life syndrome theory predict that populations are comprised of individuals exhibiting different reproductive schedules and associated behavioural and physiological traits, optimized to prevailing social and environmental factors. Changing weather and social conditions provide in situ cues altering this life‐history optimality; nevertheless, few studies have considered how tactical, sex‐specific plasticity over an individual's lifespan varies in wild populations and influences population resilience. We examined the drivers of individual life‐history schedules using 31 years of trapping data and 28 years of pedigree for the European badger (Meles meles L.), a long‐lived, iteroparous, polygynandrous mammal that exhibits heterochrony in the timing of endocrinological puberty in male cubs. Our top model for the effects of environmental (social and weather) conditions during a badger's first year on pace‐of‐life explained <10% of variance in the ratio of fertility to age at first reproduction (F/α) and lifetime reproductive success. Conversely, sex ratio (SR) and sex‐specific density explained 52.8% (males) and 91.0% (females) of variance in adult F/α ratios relative to the long‐term population median F/α. Weather primarily affected the sexes at different life‐history stages, with energy constraints limiting the onset of male reproduction but playing a large role in female strategic energy allocation, particularly in relation to ongoing mean temperature increases. Furthermore, the effects of social factors on age of first reproduction and year‐to‐year reproductive success covaried differently with sex, likely due to sex‐specific responses to potential mate availability. For females, low same‐sex densities favoured early primiparity; for males, instead, up to 10% of yearlings successfully mated at high same‐sex densities. We observed substantial SR dynamism relating to differential mortality of life‐history strategists within the population, and propose that shifting ratios of ‘fast’ and ‘slow’ life‐history strategists contribute substantially to population dynamics and resilience to changing conditions.     

Life-history evolution in Anodonta piscinalis (Mollusca,Pelecypoda)

Summary The correlations between certain life-history parameters (reproductive effort, reproductive life-span, age of first reproduction, general growth index, variation in juvenile survival, availability of resources) were studied in 13 populations of the mussel Anodonta piscinalis in south-western Finland in 1975 and 1976Reproductive life-span correlated positively (r _s=0,823, P<0.001) with variation in juvenile survival. The average availability of resources correlated negatively both with the reproductive life-span (r _s=-0.841, P<0.001 after the variation by juvenile survival had been deleted) and variation in juvenile survival (r _s=-0.676, P<0.05).The reproductive effort for female mussels at each site was computed by comparing body weight of reproductive females with body weights of non-reproductive individuals. Availability of resources was much higher in 1976 than in 1975. Consequently, the reproductive effort, an index of the strain of reproduction, was higher in 1975 than in 1976. In 1975 there was a significant correlation between reproductive effort and the length of the reproductive life-span (-0.727, -0.806) and also with the reproductive effort and the variation in juvenile survival (-0.718, -0.758) in females of the length of 60 mm and 70 mm respectively. In 1976, when availability of resources was better, such correlations were not found.Spatial and temporal change in the intake of resources complicates applicability of the principle of resource allocation in the theory of life-history evolution. Studying the mere allocation is not enough if the intake of resources varies in the groups studied. The ratio ovary weight/body weight is a dubious measure of reproductive effort in comparative studies when the input of resources can vary, and this possibility can be ruled out only exceptionally.Correlation between growth and reproductive effort was positive, obviously because both are important components in creating high reproductive capacity. In 1975 reproductive effort increased with size (age). Change in reproductive effort correlated with reproductive life-span (r _s=-0.633, P<0.05).The following parameters occurred together: short reproductive life-span, low age of first reproduction, high reproductive effort, rapid growth and high clutch size. They were realized at sites where the availability of resources was good and variation in juvenile survival was low-i.e. the environment was stable. The results conflict with the prediction of the theory of r and K-selection.     

Reproductive effort,fecundity and energy allocation in two species of the genus Perinereis (Polychaeta: Nereididae)

Summary

The reproductive effort in terms of fecundity and energy allocation was studied in two species of semelparous polychaetes belonging to the genus Perinereis, living in the same environment, with different reproductive modalities. There is a great individual variability both in terms of reproductive effort and fecundity. Fecundity varied from 4080 to 15000 oocytes in P. rullieri and from 7000 to 26000 in P. cultrifera; no linear relationship was found between oocyte number and total jaw length utilised as size index. The energy content of germinal and somatic tissues was determined by Differential Scanning Calorimeter (DSC). The reproductive effort was calculated as RE = E_G/(E_G + E_S) where E_G is the total energy in germinal tissues and E_S is the total energy in somatic tissues. Reproductive effort is very high with mean values of 0.62 for P. rullieri and 0.79 for P. cultrifera. The different amounts of energy allocated in germinal tissues can be attributed to the different reproductive modalities—P. rullieri reproduces in the atokous phase whereas P. cultrifera has conserved epitoky in its life-cycle. The lack of correlation between reproductive effort and size index strongly suggests that reproductive allocation does not increase with age. In semelparous species the variability in fecundity and reproductive effort observed cannot be interpreted in terms of a trade-off between fecundity and survival as in iteroparous species. In fact, in semelparous an individual allocates all available resources to reproduction and then dies.     

Reproductive modes in the epixylic hepatic Anastrophyllum hellerianum

The frequency and dynamics of sexual and asexual reproduction were investigated in a dioecious epixylic hepatic, Anastrophyllum hellerianum, which has declined in recent decades in Finland as a consequence of forestry practices. In our investigation asexual reproduction by gemmae was the dominant mode of reproduction and specialised gemmiparous shoots were present in all colonies studied. The proportions of dead shoots were considerably higher among sex-expressing than among non-sexexpressing shoots. Our results suggest that lower reproductive investment is required for asexual than for sexual reproduction. For instance, no trade-off is detected between asexual reproduction and survival of the gemmiparous shoots in A. hellerianum. Sexual reproduction occurred only in 12% of the colonies and it was promoted by the following factors: medium shoot density, high proportion of sex-expressing shoots, an even sex ratio and very short distances between individuals representing opposite sexes. The ratio of dead males to dead females was significantly female-biased, which suggests higher mortality among female shoots. At the level of individual shoots, more spores than gemmae were produced. However, as a consequence of the low frequency of sporophyte-bearing shoots, gemma production highly exceeded spore production at the colony level. Furthermore, cultivation tests of the propagules showed that gemmae germinate faster than spores.     

Testing generalizations about latitudinal variation in reproduction and recruitment patterns with sicyoniid and caridean shrimp species

Summary

Study of latitudinal variation in seasonality of reproduction and recruitment of benthic marine invertebrates is useful in generating and testing hypotheses about causal factors acting on reproduction such as temperature and larval food supply that might be altered by changes in world climate. Analysis of latitudinal variation in reproductive patterns might be made with comparisons (a) among species with a common phylogenetic history from different latitudes and habitats and (b) among phylogenetically different taxa from the same location. Hypotheses on variation of reproductive seasonality with latitude are tested here with results of a study on nine species of caridean and two species of sicyoniid shrimp sampled from a tropical seagrass meadow in Puerto Rico. Breeding condition was determined by the presence or absence of incubated embryos (carideans) and the state of ovarian development in both carideans and sicyoniids. Recruitment was estimated from the percentage of individuals of monthly population samples in the juvenile size classes. Comparison of reproductive patterns among tropical, subtropical, and cool temperate Sicyonia spp. supports the paradigm of continuous reproduction in the tropics with increased restriction of breeding season with an increase in latitude. A greater intensity of breeding effort appears to accompany the shorter breeding period associated with an increase in latitude. At the tropical site most females of all caridean species carried embryos during all months of the year. With the onset of sexual maturity, caridean females produced consecutive broods for the rest of their relatively short (< 6 month) life span. In both sicyoniid and caridean species, recruitment occurred throughout the year but was highly variable, i.e., episodic rather than truly continuous or seasonal. Patterns of recruitment were highly concordant among but not between sicyoniid and caridean species, indicating that different sets of environmental factors controlled recruitment in the two groups. It is suggested that simultaneous study of adult reproduction and larval ecology is necessary to understand patterns of reproduction and recruitment. Coordinated effort on a global scale in studying latitudinal variation in reproduction and recruitment is suggested in order to predict the consequences of climate change on commercially and ecologically important marine invertebrate species.     

Reproductive features and gonad development cycle of the soft bottom-gravel gorgonian Leptogorgia sarmentosa (Esper, 1791) in the NW Mediterranean Sea

Abstract

Leptogorgia sarmentosa (Cnidaria: Octocorallia) is a common soft bottom-gravel gorgonian in the northwestern Mediterranean Sea. This study examined the annual reproductive cycle of a L. sarmentosa. population at a depth of 30 m, and further determined the sex ratio, the intra-colonial gonadal output variability and the age at first reproduction. L. sarmentosa was gonochoric and the population studied was characterized by a sex ratio slightly biased towards female colonies (1 male:1.6 female). Secondary branches had higher polyp fertility (number of gonads per polyp) compared to primary branches, but because of the number of polyps on the former, most of the sexual effort was actually contributed by the primary branches, as in other gorgonian species. Male colonies became fertile above a height of 21 cm, but female colonies had gonads even in the 1–10 cm height class. Spawning occurred between late August and early September, although there was no direct observation of broadcast spawning or surface brooder strategy. The maximum gonad size was 550 μm in males and 500 μm in females, with a mean diameter of 270 μm for spermaries, and 190 μm for eggs. The number of gonads per polyp prior to spawning reached 4–5 spermaries polyp!1 in male colonies, and 3–4 eggs polyp!1 in female colonies. Spawning did not appear to be synchronized with the full moon. L. sarmentosa appeared to have a different reproductive strategy to other Mediterranean gorgonians (living on hard bottom substrata), probably because of its different habitat preferences and biological (morphology, diet, prey capture rates, growth, biochemical levels) features.     

Differential niche modification by males and females of a dioecious herb: extending the Jack Sprat effect

Males and females of dioecious plants often differ in morphological, physiological and life‐history traits, probably as a result of their different requirements for reproduction. We found that the growth and reproductive effort of individuals of the dioecious herb Mercurialis annua depended on whether males or females had been growing in the soil previously. This suggests that males and females of M. annua differentially modify the soil in which they are growing. Our study indicates that sexual dimorphism in dioecious plants can give rise to increased environmental heterogeneity as a consequence of sex‐specific niche modification.     

Resource allocation in the red ant Myrmica ruginodis– an interplay of genetics and ecology

Worker‐queen conflicts over reproductive allocation (colony maintenance vs. reproduction) and sex allocation (females vs. males) were examined in two populations of the facultatively polygynous ant Myrmica ruginodis. Plasticity of social organization in the form of two co‐existing social types (microgyna and macrogyna) has a profound effect on reproductive allocation. Workers control sex allocation by biasing sex ratios towards their own interest, but local resource competition (LRC) because of restricted dispersal of microgyna females resulted in male bias in one study population. Colony sex ratios were split and followed the predictions of the split sex ratio theory: single queen colonies with higher relatedness asymmetry (RA) produced more females than multiple queen colonies with lower RA. Single and multiple queen colonies showed similar patterns in most aspects of their reproduction, and reproductive allocation could not be explained by the hypothesis tested. This suggests that reproductive allocation conflict is of minor importance in M. ruginodis.     

SEX ALLOCATION AND OUTCROSSING RATE: A TEST OF THEORETICAL PREDICTIONS USING BROMEGRASSES (BROMUS)

Predictions of sex-allocation theory were tested by comparisons among hermaphroditic bromegrass (Bromus) species that differed in outcrossing rate. Relative maternal and paternal investment were calculated using both the ratio of pollen to seed production, and absolute allocations in units of energy, nitrogen, phosphorus, potassium, magnesium, and calcium. Outcrossing rate had a large effect on sex allocation; species having greater outcrossing rates had relatively more paternal reproductive effort. Bromus inermis was obligately outcrossing, and nearly half of its reproductive effort was devoted to pollen production. Three partially outcrossed species, B. kalmii, B. ciliatus, and B. latiglumis, invested between 5% and 11% of reproductive effort in pollen production. Paternal investment was less than 2% in the selling species B. tectorum. Estimates of sex allocation were relatively unaffected by the resource currency used in calculation. The differences among species in sex allocation were mostly due to differences in anther size and seed set.>     

云南高原湖泊水葱克隆生长与有性繁殖特征及影响因子

为掌握挺水植物克隆生长与有性繁殖参数的空间分布格局特征及环境因子对植物繁殖的影响路径,该文利用云南高原的立体地形,通过空间替代时间的方法,探讨6个湖泊共有挺水植物水葱(Schoenoplectus tabernaemontani)的克隆生长、有性繁殖的地理差异和变化规律以及对环境变化的响应。结果表明：(1)密度、株高、基径等克隆生长参数,以及结实率、穗生物量及其投资比、种子产量、活性种子数等繁殖参数在不同地理空间上存在显著差异(P<0.05),而地上生物量无显著差异。(2)密度、株高、结实率、穗生物量及其投资比等参数具有显著的经纬度、海拔地带性分布特征,其中密度随纬度和海拔的增加而增加、随经度的增加而减小,而株高、结实率、穗生物量及其投资比随纬度和海拔的增加而减小、随经度的增加逐渐增大。(3)暖月和冷月均温,土壤全氮、全磷是影响水葱克隆生长(密度、株高)的关键因子,其中暖月均温影响最大,年均降水、土壤有机碳是影响水葱有性繁殖的关键因子,其中年均降水影响最大。综上认为,气候因子(暖月均温、冷月均温和年均降水)是影响云南高原湖泊湖滨带植物水葱生长和繁殖的主要因子。     

Influence of temperature and food availability on the ecological energetics of the giant scallop Placopecten magellanicus

Summary Gonad output, reproductive effort and residual reproductive value are greater in scallops (Placopecten magellanicus) from shallow water, where conditions are more favourable, than in scallops from deep water. Variation between years in these fitness correlates is also greater in shallow water scallops. High reproductive effort is associated with a greater reproductive cost, although in general reproduction in this species appears to be restrained, and only in older individuals from shallow water is there evidence of reckless reproductive behaviour. Reproductive effort increases as the animal grows older, but residual reproductive value is a maximum at age 4 years, after which it decreases with age owing to greater mortality. Localities vary in their suitability for scallop growth and reproduction, and at one Newfoundland site conditions in shallow water (10 m) are better than those in deep water (31 m). Scallops from the former have a greater fitness than those from the latter. The energy costs of reproduction have implications for life history variability in P. magellanicus, although for a considerable part of its lifetime the scallop is able to maximise gamete production in response to environmental factors (especially the food supply) without trading off reproduction against growth or maintenance.     

Condition Dependent Effects on Sex Allocation and Reproductive Effort in Sequential Hermaphrodites

Theory predicts the optimal timing of sex change will be the age or size at which half of an individual''s expected fitness comes through reproduction as a male and half through reproduction as a female. In this way, sex allocation across the lifetime of a sequential hermaphrodite parallels the sex allocation of an outbreeding species exhibiting a 1∶1 ratio of sons to daughters. However, the expectation of a 1∶1 sex ratio is sensitive to variation in individual condition. If individuals within a population vary in condition, high-condition individuals are predicted to make increased allocations to the sex with the higher variance in reproductive success. An oft-cited example of this effect is seen in red deer, Cervus elaphus, in which mothers of high condition are more likely to produce sons, while those in low condition are more likely to produce daughters. Here, we show that individual condition is predicted to similarly affect the pattern of sex allocation, and thus the allocation of reproductive effort, in sequential hermaphrodites. High-condition sex-changers are expected to obtain more than half of their fitness in the high-payoff second sex and, as a result, are expected to reduce the allocation of reproductive effort in the initial sex. While the sex ratio in populations of sequential hermaphrodites is always skewed towards an excess of the initial sex, condition dependence is predicted to increase this effect.     

Investment in survival and reproduction along a semelparity–iteroparity gradient in the Beta species complex

The Beta species complex shows a gradient of life histories from pronounced semelparity (big‐bang reproduction) to pronounced iteroparity (repeated reproduction). Models assume a trade‐off between investment in reproduction and survival. Reproductive effort is thought to increase with decreasing life span, and to be invariable in semelparous plants and susceptible to environmental conditions in iteroparous plants. These assumptions and hypotheses were verified by a greenhouse experiment testing six different life cycles at three contrasting nutrient levels. This study suggests that reproductive effort is negatively correlated with mean life span along the life‐cycle gradient. Unlike semelparous beets, reproductive effort in iteroparous beets is extremely sensitive to nutrient level. Phenotypic correlation between allocation to reproduction and allocation to survival generally appeared significantly negative in the longest‐lived iteroparous beets, nonsignificant in intermediate life histories and obviously positive in semelparous beets (no trade‐off control).     

Reproductive traits of the “ocellated killifish” Floridichthys polyommus Hubbs, 1936 (Pisces: Cyprinodontidae) inhabiting estuary of the Champotón River (Campeche,Mexico)

This study explores the reproductive biology and the influence of environmental factors on the reproductive traits of Floridichthys polyommus inhabiting the estuary of the Champoton River. The analysis included population structure, gonadal developmental stages, reproductive period, size at first sexual maturity, fecundity, sex ratio, and somatic indexes. A spatio‐temporal pattern in the distribution of the seven size classes was detected. The species showed a positive allometric growth. Sex ratio was 1.21:1 (females:males). Size at first maturity was 42.23 mm (females) and 47.8 mm (males). A higher absolute and relative fecundity was detected in Puente Champotón estuary (PCH) with lower salinities than those detected in the Delta (DE). The adaptive significance of this trait could be in response to the heavy osmotic constraint imposed by extreme salinities in the DE. Floridichthys polyommus prefers PCH for spawning, and as a result a higher number of ripe individuals was observed in this site, characterized by the highest nutrient levels, which can boost productivity and food availability for fish. Hepatosomatic index was negatively correlated with gonadosomatic index, suggesting energy transfer from the liver towards gamete production. Floridichthys polyommus exhibits an opportunistic strategy (early maturity, small oocytes, small clutches) suggesting that energy is allocated towards reproduction to compensate for the unpredictable hydrological conditions imposed by the estuary (particularly during the hurricane season). Floridichthys polyommus shows a reproductive strategy exhibited by fish living in unstable systems. A seasonal divergence was observed in the reproductive traits of F. polyommus, while differences between study sites were for fecundity.