Asynchronous Oocyte Development Research Articles

Influences of gonad developmental stage on ovary selenium concentrations in fish-implications for ovary selenium monitoring.

Monitoring selenium (Se) concentrations in fish ovaries is an important tool for evaluating the ecological risk posed by Se in aquatic systems. Most guidance recommends sampling fish ovaries as closely as possible to when fish spawn on the premise that Se is mobilized from the liver to the ovary during vitellogenesis, and therefore, sampling ovaries during the early phases of oocyte maturation may underestimate egg Se concentrations at the time of spawning. In this study, we evaluated ovary Se data from two species with synchronous oocyte development (Ptychocheilus oregonensis and Prosopium williamsoni), one species with asynchronous oocyte development (Richardsonius balteatus), and one where the mode of development is unclear (Mylocheilus caurinus). A multivariate analysis of ovary Se as a function of fish sampling location, size, and gonado-somatic index (GSI) demonstrated ovary Se was strongly negatively correlated with GSI in fish species with synchronous oocyte development but only weakly correlated in a species with asynchronous development. In R. balteatus, a relationship between expressible (released) egg Se and remaining ovary Se was observed, with egg concentrations ∼54% of ovary concentrations on average. Overall, our findings suggest that current understanding of the mechanisms by which Se is maternally transferred to oocytes is not entirely correct and raises questions regarding how and when during the reproductive cycle Se is mobilized to ovaries. Further, our findings have significant implications for interpretation of ovary Se monitoring data collected from unripe fish. We developed regression-based models to correct ovary Se data that are biased by sampling females not in spawning condition and demonstrate how this bias can impact evaluation of Se risk to fish.

Molecular characterization and stage-dependent gene expression of gonadotropin receptors in Pacific bluefin tuna, Thunnus orientalis, ovarian follicles

To understand the physiological mechanisms by which pituitary-derived gonadotropins (Gths), follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh) regulate asynchronous oocyte development, we investigated the function and expression of Fsh and Lh receptors (Fshr and Lhr, respectively) in Pacific bluefin tuna (PBT, Thunnus orientalis). As a first, we cloned the full-length cDNAs encoding PBT Fshr and Lhr. Recombinant PBT Fsh and Lh single-chain proteins were produced in abundance using stable CHO-DG44 cell lines and were subsequently purified from the culture medium, culminating in their yields being 87.0 and 88.2%, respectively. An in vitro reporter assay using homologous recombinant Gths revealed that PBT Fshr and Lhr responded strongly to their corresponding ligands in a dose-dependent manner, with no cross-activation over a wide range of concentrations. Moreover, quantitative expression analysis of Fshr and Lhr at the follicle level showed that fshr gene expression was highly upregulated in the ovarian follicles through vitellogenesis, while lhr expression was significantly upregulated and peaked in fully vitellogenic ovarian follicles. These findings suggest that asynchronous-type oocyte development is primarily attributed to the differential function and expression of Gthrs, rather than the ligand, in PBT.

Reproductive biology and nuptial coloration of Trachinus draco (Trachinidae) from Atlantic Spanish waters (SW Europe)

Studies focusing on reproductive biology play a key role in deciphering fish population dynamics. We studied the main features of the reproductive biology of the greater weever Trachinus draco based on gonad histology and digital image analysis techniques and the main hypothesis of the study is that males of T. draco exhibit a nuptial colouration. The biological samples of 311 individuals along the Atlantic coast of Spain, covering the twelve months of the year (from 2020 to 2022), in combination with the gonadosomatic index trend revealed a spawning season from May to August, consistent with similar studies in different geographical areas. Length-weight relationship presented differences by sex (females reach higher weight at the same length). The maturity ogive for females indicated that 50 % were mature at a length of 182 mm. Histological analysis confirmed asynchronous development of secondary growth oocytes, pointing to a batch spawning strategy. Digital image analysis of the nuptial coloration showed that the presence of a black spot above the pectoral fin in males was significantly correlated with the spawning capable phase, while blueish coloration was influenced by sex, size and maturity phase, with larger spawning males having the largest areas of blueish coloration. The results of this study represent a significant improvement of our understanding of the reproductive biology of T. draco.

Regularities of oogenesis and spermatogenesis of commercially valuable fish species in the water bodies of the Dagestan part of the Middle Caspian Sea

Based on our own research and literature data, it was proved that the features of vacuole location, size, and variability in the periods of early and late trophoplasmic growth require the closest attention. There are also certain inconsistencies of gametogenesis between different species of fish within the family. These consist in the fact that for fish species that have a shorter spawning period (roach, pike and perch), the general specificity of the annual cycles of development of the sex glands is characterized by the absolute termination of spermatogenesis by the period of the beginning of spawning, the absence of maturation or new formation of sexual products in this process. Individuals with extended spawning (for gouster and silver carp) are characterized by such features as the presence of an additional wave of spermatogenesis, which begins and ends during the spawning period, the incomplete development of sexual products by the beginning of spawning and the continuation of the process of their maturation in individual cysts of the testes throughout the spawning period (for bream and fish), continuous spermatogenesis,which allows the use of reproductive products at any time from spring to fall of the annual cycle, and under favorable conditions — throughout the year (for carp and catfish). In the experimental aspect, the obtained results can be applied in conducting a large-scale selection of female fish, based on the size of ovulated oocytes and individual selection according to the average statistical size of the latter. In fishery plan the above mentioned is required in connection with obtaining eggs from fish with batch spawning and asynchronous development of oocytes.

Aspectos reprodutivos das fêmeas de Leporinus lacustris Campos, 1945 (Characiformes, Anostomidae) em uma planície de inundação Neotropical

Abstract: Aim This study evaluates the reproduction and fecundity of Leporinus lacustris in upper Paraná River floodplain environments with the objectives to (i) recognize the germ cells of folliculogenesis and oogenesis; (ii) characterize reproductive phases; (iii) investigate oocyte diameter and evaluate if this species has group synchronous or asynchronous oocyte development and if spawning is total or batch; (iv) estimate batch fecundity; (v) establish the relationship between fecundity/ovary weight, standard length, and total weight; (vi) verify the reproductive areas of this species in the upper Paraná River floodplain. Methods Sampling was carried out using gillnets in rivers, and open and closed lagoons, in March, June, September, and December 2013, 2014, 2015, 2016, 2018, and 2019 and March and September 2017. A total of 442 females were sampled and 111 subsampled, each of which had an ovary removed and fixed in Bouin solution. A subsample of 20 ovaries in the spawning capable phase were fixed in a 4% buffered formaldehyde solution to estimate the diameter of the oocytes and fecundity. The ovaries were dehydrated, embedded in historesin, cut, stained, and evaluated as regards folliculogenesis, oogenesis, development phases, and reproduction areas. Results The germ cells recorded were differentiated oogonia, primary and secondary growth oocytes, fully-grown and mature oocytes, and post-ovulatory follicles that permitted the recognition of the reproductive phases. Oocyte diameter information revealed that the species has group synchronous oocyte development, determinate fecundity and batch spawning, and eliminates an average of 38,490 oocytes. Conclusions The fact that Leporinus lacustris is reproductively successful in the Baía River and in the Fechada, Guaraná, Patos, Garças, Ventura and Ressaco do Pau Véio lagoons strengthens the importance of the areas of environmental protection of the islands and lowlands of the Paraná River, Ilha Grande National Park and Ivinheima River State Park.

An insight into the fishery, biology and population dynamics of Auxis rochei (Risso, 1810) along the south-west coast of India

Auxis rochei is one of the coastal tunnies contributing substantially to the tuna landings inIndia, with an average (2014-2019) annual catch of 7210 t. Kerala stood first, with an annualaverage landing of 3176 t. The fishery comprised 14.5 - 39.6 cm fork length (FL) size groupswith a mean length of 27.64 cm and a major mode of 26 cm FL. The Length-weight (L-W)relationship of pooled fishes was expressed as W= 0.000003 L3.22 (r2= 0.91). The size at firstmaturity was estimated at 25.8 cm FL when the fish was 1.5 years old. The number of eggsper spawning ranged from 84,562 to 1,33,698 and the ova diameter ranged between 0.1and 0.6 mm, indicating asynchronous oocyte development with multiple spawning. Highergonadosomatic index (GSI) was recorded during April, May and June and coincided withthe minimum gastrosomatic index (GaSI). The recruitment pattern was bimodal, with variedintensity ranging from 0.79-17.89%. Growth was allometric and the von Bertalanffy growthequation derived was Lt=43.5(1-e-0.8(t+0.0212)). The growth performance index (ɸ) was 3.18 andthe longevity of the fish was estimated at 3.7 years. One-year-old plus fishes sustained thefishery (22 - 32 cm FL). Total mortality (Z), natural mortality (M) and fishing mortality (F)were estimated at 3.70, 1.40 and 2.30, respectively, with an exploitation rate (E) of 0.62and the exploitation ratio (U) of 0.60. Beverton and Holt yield per recruit (Y/R) and Biomassper recruit analysis indicated that the Emax was at 0.87, much higher than the present levelof exploitation, reflecting the sustainable fishery along the coast. Standing stock biomass(SSB) was estimated at 7215.7 t, and the spawning stock biomass formed 55.5% of the SSB.Thompson and Bell analysis indicated the MSY as 8125 t, at F-factor, 2.6. The biologicalreference points FCURR/FMSY (0.4) and BCURR/BMSY (1.5) were at safe levels, signifying the scopefor fishery enhancement. Keywords:Biological reference point, Fecundity, Growth, GSI,L-W relationship, Mean length, Mortality, SSB

Reproductive traits, dynamics of oogenesis and embryonic developments in the deep-sea shrimp Plesionika semilaevis from the southeastern Arabian sea

Reproductive traits are a crucial biological indicator of a population's resistance to anthropogenic and environmental pressures. The reproductive biology of Plesionika species from temperate and sub-tropical regions is relatively well known. However, a knowledge gap exists regarding the species' reproduction and life strategies in tropical waters like the Indian Ocean. This paper covers the reproductive period, ovarian and embryonic development, embryo size, brood size and size at sexual maturity of Plesionika semilaevis, a commercially important species from the tropical waters of the southeastern Arabian Sea. Histological analysis revealed asynchronous oocyte development with multiple oocyte stages present in each ovary sample, although with varying proportions. Maturation of the ovary was seen during the embryo incubation phase, which indicates that females are able to spawn several times during a reproductive cycle. A total of 1802 females of P. semilaevis were examined and sorted into ovigerous and non-ovigerous stages, and the embryos were divided into four stages of development. Although ovigerous females were present in every month's samples, the main reproductive season is from November to February, as evidenced by the larger percentage of ovigerous females during this time. Based on the percentage of embryos in various stages, the spawning and hatching periods were estimated to be December to February and March to May, respectively. Embryo size increased with the developmental stage (p = 0) but was independent of body size (p > 0.05). A positive correlation was observed between brood size and female body size in all four stages of embryo development but, as the embryos developed a significant decrease in brood size was noticed. Based on the size at which 50% of the females had matured ovaries and 50% were ovigerous, the size at sexual maturity, CL50ov and CL50em, was calculated to be 15.51 mm and 15.07 mm in carapace length, respectively. The brood size ranged from 2093 to 12887 embryos with a mean size of 0.51 × 0.40 mm following spawning and 0.66 × 0.50 mm prior to hatching.

Determining Sexual Development and Size at Sexual Maturity of Sardinella tawilis and its Implications on Management

Reproductive biology is important in formulating management interventions for fish stocks. Limits on catch size are established based on the identified size at first sexual maturity of the target fish species, which can be accurately determined through histological analysis of gonads. The study investigated the reproductive characteristics of the endangered Sardinella tawilis and determined the size at first sexual maturity based on histological analysis. Between 2017 and 2018, 312 fish samples with different lengths were collected in Taal Lake's northern and southern basins. The length-weight relationship of S. tawilis shows that the species exhibits negative allometric growth. Female S. tawilis, characterized by larger sizes, are significantly more abundant in our catches than male individuals (mean sex ratio p<0.05) and exhibit an asynchronous oocyte development. Histological analysis of gonads showed that the size at sexual maturity for both male and female S. tawilis were at 75 to 79 mm FL, which was smaller than the reported size at sexual maturity based on morphological analysis. Smaller average and maximum lengths, as well as the size at first sexual maturity, could suggest that S. tawilis has experienced growth overfishing and a slowly degrading lake environment through time. Results highlighted the importance of ensuring that immature S. tawilis can enter sexual maturity and contribute to the population through reproduction. It is also highly recommended that the size of S. tawilis to be targeted by fisheries are individuals above 100 mm FL, which exhibited the highest proportion of spawning capable individuals.

Spawning and maturity traits of coexisting Platycephalidae (Platycephalus caeruleopunctatus, Platycephalus grandispinis, Platycephalus richardsoni) from southeast Australia.

Examination of the spawning and maturity traits of coexisting Platycephalus caeruleopunctatus, Platycephalus grandispinis and Platycephalus richardsoni (Pisces: Platycephalidae) in coastal waters of southeastern Australia identified many commonalities. Each species was gonochoristic, reproductively active for a prolonged period each year, displayed asynchronous oocyte development with indeterminate fecundity and thus likely spawned multiple times throughout each spawning season. Males of all three species matured at smaller total lengths and younger ages than females, with skewed sex ratios reflecting divergent growth characteristics between sexes. Reproductive isolation among species is likely maintained through behavioural and morphological factors as well as species-specific depth-related separation of reproductively active individuals. General similarities in the reproductive strategies of each species and with other sympatric coastal teleosts suggest similar ecological adaptations to a variable coastal environment.

Asynchronous embryonic germ cell development leads to a heterogeneity of postnatal ovarian follicle activation and may influence the timing of puberty onset in mice

BackgroundOvarian follicles, which are the basic units of female reproduction, are composed of oocytes and surrounding somatic (pre) granulosa cells (GCs). A recent study revealed that signaling in somatic preGCs controlled the activation (initial recruitment) of follicles in the adult ovaries, but it is also known that there are two waves of follicle with age-related heterogeneity in their developmental dynamics in mammals. Although this heterogeneity was proposed to be crucial for female reproduction, our understanding of how it arises and its significance is still elusive.ResultsIn the current study, by deleting the key secreted factor KIT ligand from preGCs and analyzing the follicle cell developmental dynamics, we revealed distinct patterns of activation and growth associated with the two waves of follicles in mouse ovary. Our results confirmed that activation of adult wave follicles is initiated by somatic preGCs and dependent on the KIT ligand. By contrast, activation of first wave follicles, which are awakened from germ cells before follicle formation, can occur in the absence of preGC-secreted KIT ligand in postnatal ovaries and appears to be oocyte-initiated. We also found that the asynchronous activity of phosphatidylinositol 3 kinases (PI3K) signaling and meiotic process in embryonic germ cells lead to the follicle heterogeneity in postnatal ovaries. In addition, we supplied evidence that the time sequence of embryonic germ cell development and its related first wave follicle growth are correlated to the time of puberty onset in females.ConclusionTaken together, our study provides evidence that asynchronous development of embryonic oocytes leads to the heterogeneity of postnatal ovarian follicle activation and development, and affects the timing of onset of puberty in females.

Life History of Swordfish, Xiphias gladius, Caught in the Northern Gulf of Mexico

The current study examined 93 Swordfish, Xiphias gladius, (64 females, 27 males, 2 unknown) ranging in size from 77.6–246.3 cm lower jaw fork length (LJFL) from the northern Gulf of Mexico (GOM). Samples were collected between March and August in 2005–2007, 2017–2019 and 2021. Age estimates of 51 Swordfish resulted in a maximum observed age of 11 years (205.0 cm LJFL) and 7 years (190.4 cm LJFL) for females and males, respectively. Observed and back—calculated length—at—age data were fitted to 4 growth models (2— and 3— parameter von Bertalanffy, Gompertz, and logistic). The 2—parameter von Bertalanffy was the model that best fit the data (Linf = 210.2 cm LJFL, k = 0.25). Histological examination of gonadal tissue from 91 fish indicated that females reached 50% and 95% physiological maturity at 116 ± 6 cm LJFL and 143 ± 8 cm LJFL, respectively, corresponding to ages 2—3 years. All males >82 cm LJFL were physiologically sexually mature. Only 10% of females were reproductively active, with spawning capable females captured in June. Reproductively active females exhibited asynchronous oocyte development indicating batch spawning. Most males (96%) were spawning capable from April–August. Philometra sp. infection was found in all ovaries examined (n = 16) but with low abundance (2.25 ± 0.42); male philometrids were more prevalent than females (91.7% and 66.7%, respectively). Swordfish in the northern GOM appear to achieve sexual maturity at a younger age, grow faster, and have shorter theoretical longevity than previous reports from other regions world—wide.

Reproductive strategies of a temperate Australian sciaenid (teraglin, Atractoscion atelodus )

Worldwide there have been declines in stocks of exploited sciaenids. Despite a long history of exploitation, there has been no study of the life history characteristics of the fishery-important sciaenid, teraglin, Atractoscion atelodus. This study describes the reproductive characteristics of A. atelodus within the major area of its distribution and fishery, New South Wales (NSW) Australia. Characteristics studied included the size and age at maturity, fecundity, spawning mode and season, and these are compared to congeneric species. Atractoscion atelodus displays year-round batch spawning behaviour with asynchronous oocyte development and indeterminate fecundity. This is unusual for sciaenids, which typically display spring-summer spawning and only over a few months. The length and age at which 50% of the population matures for both males and females is 36 cm fork length (FL) and 1 year, a smaller size compared to other closely related sciaenids. While the species displays resilient reproductive characteristics such as protracted year-round spawning, constant supply of vitellogenic oocytes and relatively small/young age at maturity, there are also characteristics that make it susceptible to over-exploitation. These include highly female skewed sex ratios, as well as their schooling and voracious feeding behaviour leading to the potential for high catch rates.

Reproductive biology of the white grunt, Haemulon plumierii, in the coastal waters of the northern Yucatán Peninsula

White grunt ( Haemulon plumierii ) has gained relevance as an alternative resource to fisheries off the northern coast of the Yucatan Peninsula, however, knowledge of its biology in the region is scarce. Thus, in order to explore the reproductive biology of H. plumierii , a total of 355 specimens were caught with a hand line and bait, from September 2015 to November 2016 to conduct histological analysis of the gonads. The sample was represented by 233 males and 122 females, differing from the 1:1 sex ratio (1 female per 2.1 males). The reproductive season occurred from February to August with a maximum peak in May. The 50% maturity size (L50) was estimated at 15.15 and 15.22 cm TL for males and females, respectively. The batch fecundity ranged from 9,363 to 42,371 eggs per batch, with an average of 26,558 eggs. Several reproductive biology features were observed in H. plumierii , such as spring spawning seasonality, length at sexual maturity, asynchronous oocyte development with an indeterminate fecundity, and batch spawning. This kind of information can guide proposals for further sustainable fishery management measures that may guarantee the continuity of this economically important species in the region.

Reproductive characteristics of Ratabulus diversidens and Ambiserrula jugosa (Pisces: Platycephalidae) from continental shelf waters of south-eastern Australia

AbstractThe reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and mud flathead, Ambiserrula jugosa, that interact with fisheries across continental shelf waters of eastern Australia were examined. Samples were collected across three depth strata and two locations on a monthly basis over two years. Males of both species matured younger and at smaller total lengths (TL) than females. Estimated TL and age (years) at maturity (L50 and A50, respectively) of R. diversidens also varied between locations, but differences were not related to differential growth. Although some mature individuals of both species occurred year-round, they were most prevalent and gonadosomatic indices greatest, between the austral spring and autumn. Mature R. diversidens almost exclusively occurred in deeper offshore waters, whereas the opposite was evident for A. jugosa. Both species displayed asynchronous oocyte development, and were thus considered capable of spawning more than once throughout each spawning season. Potential batch fecundity was positively related to TL for R. diversidens, but not A. jugosa, possibly due to the small size of the latter species. The sex ratios for R. diversidens varied between locations and length categories, and like A. jugosa the larger categories were skewed towards females, a result of divergent growth between sexes. Macroscopic and microscopic evidence indicated both species were gonochoristic. The data provide new information for fisheries management consideration and contribute to the data-poor international knowledge base of platycephalid biology.

Fishing gear selectivity on sub-adults and spawning stock of the Tarpon Megalops atlanticus (Actinopterygii: Megalopidae) in Northeast Brazil

The Tarpon (Megalops atlanticus) is a species with economic importance as a food fish and a source of income for artisanal fishers. Research regarding the reproductive biology of this species is scarce or incomplete, especially for this species in northeastern Brazil. Tarpon were caught each month near the Bitupitá district using longline fishing and arrowhead fixed traps, from October 2017 to September 2018. The Tarpon specimens were weighed, measured, and the type of fishing equipment used for the capture was noted. Gonads were obtained and evaluated macroscopically, and fixed and preserved for future microscopic analyses. The present study observed 150 females and 102 males for a total of 252 individuals. The sex ratio was 1:1.5 (M:F) and females showed a dominance in the longer length classes. Both sexes presented negative allometry (b < 3). The gonadosomatic index (GSI), Fulton’s condition (K) values and sexual maturity indicate that the reproductive period occurs between August and November, which is during the dry season. The length at first maturity (L50) presented values of 101.7 cm total length (TL) for females, 99.4 cm TL for males and 101 cm TL for both sexes grouped together. The mean fecundity was 7.5 million oocytes and the species present asynchronous oocyte development, multiple spawning periods, and continuous recruitment of oocytes from the reserve stock indicating indeterminate fecundity.

Reproductive biology and recruitment of bluefish Pomatomus saltatrix (Perciformes: Pomatomidae) in the southwestern Atlantic

The bluefish, Pomatomus saltatrix (Linneus 1766) is captured by industrial, artisanal, and recreational fisheries throughout its distribution range. The reproductive biology of P. saltatrix in the southwestern Atlantic was studied using 1,102 specimens captured by the Brazilian commercial fleet between March 2014 and December 2015. The recruitment period was identified from records of juveniles in experimental beach seine hauls carried out on sandy beaches in the external sector of Guanabara Bay for four years (2012–2015). Based on the reproductive indices and on the macro- and microscopic analyses of the gonads, spawning peaks were identified in autumn and spring. The size at first maturity was estimated at 35.5, 38.3, and 37.4 cm for females, males, and general, respectively. Ovary analyses and measurements of the oocyte diameters indicated that bluefish are multiple spawners with asynchronous oocyte development. The batch fecundity estimate was 202,752.5 eggs and ranged from 9,800.9 to 426,787.0 eggs. The species reproduces throughout the entire study area, but it is more active in the south of Arraial do Cabo. The young-of-the-year were recorded on shallow water in all seasons, with modal peaks in the summer months. The parameters estimated in this study expand and update information on this species, providing important data for the evaluation and fisheries management of the stock of P. saltatrix in the southwestern Atlantic.

Assessing effects of aromatase inhibition on fishes with group-synchronous oocyte development using western mosquitofish (Gambusia affinis) as a model

Exposure to certain anthropogenic chemicals can inhibit the activity to cytochrome P450 aromatase (CYP19) in fishes leading to decreased plasma 17β-estradiol (E2), plasma vitellogenin (VTG), and egg production. Reproductive dysfunction resulting from exposure to aromatase inhibitors has been extensively investigated in several laboratory model species of fish. These model species have ovaries that undergo asynchronous oocyte development, but many fishes have ovaries with group-synchronous oocyte development. Fishes with group-synchronous oocyte development have dynamic reproductive cycles which typically occur annually and are often triggered by complex environmental cues. This has resulted in a lack of test data and uncertainty regarding sensitivities to and adverse effects of aromatase inhibition. The present study used the western mosquitofish (Gambusia affinis) as a laboratory model to investigate adverse effects of chemical aromatase inhibition on group-synchronous oocyte development. Adult female western mosquitofish were exposed to either 0, 2, or 30 μg/L of the model nonsteroidal aromatase inhibiting chemical, fadrozole, for a complete reproductive cycle. Fish were sampled at four time-points representing pre-vitellogenic resting, early vitellogenesis, late vitellogenesis/early ovarian recrudescence, and late ovarian recrudescence. Temporal changes in numerous reproductive parameters were measured, including gonadosomatic index (GSI), plasma sex steroids, and expression of selected genes in the brain, liver, and gonad that are important for reproduction. In contrast to fish from the control treatment, fish exposed to 2 and 30 μg/L of fadrozole had persistent elevated expression of cyp19 in the ovary, depressed expression of vtg in the liver, and a low GSI. These responses suggest that completion of a group-synchronous reproductive cycle was unsuccessful during the assay in fish from either fadrozole treatment. These adverse effects data show that exposure to aromatase inhibitors has the potential to cause reproductive dysfunction in a wide range of fishes with both asynchronous and group-synchronous reproductive strategies.

Biología reproductiva del pez vela Istiophorus platypterus en la Bahía de Acapulco, Méxic

Background. The sailfish Istiophorus platypterus is a viviparous billfish species, it is caught by trolling in the sports fishery in Mexico. However, to date, there has been no reproductive biology studies of sailfish in Acapulco Bay, although the reproductive aspects of any species represent essential information for the design of management plans. Goals. Estimate the spawning frequency and batch fecundity to quantify reproductive characteristics of sailfish in waters off Acapulco, Bay. Methods. During the period 2008–2019, a total of 581 fish were sampled. Macroscopy analysis and quantitative histology was used to describe reproductive characteristics of the sailfish gonads. Results. 55.8% of the organisms analyzed were males, the remaining 44.2% were females, the sex ratio (1.26 M: 1 H) was different from the expected theoretical ratio (X2 = 7.53). The ovaries of 155 females were classified into five ovarian development phases based on histological analysis of the most advanced group of oocytes. Sailfish are multiple spawners with asynchronous oocyte development. Batch fecundity for 14 females with the presence of hydrated oocytes but without postovulatory follicles ranged 0.330 to 2.092 × 106 eggs with an average of 1.07 × 106 eggs. Gonadosomatic indices (GSI) indicated that sailfish have a reproductive period with peaks in August and October (mean monthly GSI= 4.3% and 5.4%). Conclusions. Population sailfish in Acapulco Bay is composed of males and females in similar proportions, with a gonadal development by groups that can be described in five development phases, a reproductive maximum during the warm months of the year and a relatively high fecundity.

Comparison of responses to artificial spawning of ruffe (Gymnocephalus cernua) specimens captured from their natural habitat to those produced in cultured conditions

Although ruffe (Gymnocephalus cernua) are widely distributed in Eurasia, in some regions (i.e., North America) ruffe are considered an invasive species. There have been no reports on artificial reproduction of this species. A study, therefore, was conducted to evaluate reproduction of ruffe with results of specimens captured from their natural habitat and cultured (F1 generation) specimens being compared. Spawning specimens from both stocks were treated with hormonal preparations: carp pituitary homogenate (CPH), Ovopel, Ovaprim and human chorionic gonadotropin (hCG) and results were analyzed by comparing response to the specimens of control groups. Spermiation outcomes and sperm motility of the captured and cultured ruffe were similar and with all hormonal treatments, there was a slightly greater sperm motility (55.6 %–57.1 %) in comparison to specimens of control groups (46.7 %–47.1 %). For captured specimens, there was no asynchronous development of oocytes, whereas in cultured specimens 32 % of females had asynchronous development of oocytes. The ovulation rate in specimens of all treated groups was 100 %, whereas specimens in the control groups did not reproductively mature and have ovulations. The latency time from time of hormonal treatments to initiation of reproductive functions depended on the spawning agent used and oocyte maturation stage and there was the shortest latency after using CPH and the longest with hCG treatment. The embryo survival and hatching rates varied with use of different hormonal preparations to induce reproduction: greatest hatching rates with hCG treatment (86.4 %–88.9 %), followed by Ovaprim (78.2 %–80.2 %) and least hatching rate with Ovopel and CPH treatments (66.0 %–67.1 % and 64.0 %–66.0 %, respectively).

Equilibrium reproductive strategy of the peacock bass Cichla kelberi facilitates invasion into a Neotropical reservoir.

The reproductive strategy of the non-native predator cichlid Cichla kelberi was determined to explain its success after more than 60 years of being introduced into an isolated reservoir in southeastern Brazil. This was one of the first-known translocations of the genus Cichla out of its natural range. Macro- and microscopy characteristics of the gonadal development stages and the maturation phases, along with the reproductive features (size at first maturation size, gonado-somatic index and sex ratio), were described. It was hypothesized that the stable conditions of the reservoir, with low connectivity, weakly defined spatial gradient and slight seasonal changes in environmental variables, favour the equilibrium strategy that enables predators to have high offspring survivorship because of great parental investment in individual progeny. Sex ratio was well balanced, with males and females reaching first maturity between 30.0 and 28.6 cm total length (LT ), respectively. The stages of oocyte (primary and secondary growth, vitellogenic and atresia) and spermatocyte (spermatogonia, spermatocytes, spermatids and spermatozoa) development were identified. Five phases of gonadal development (immature, developing, spawning capable, regressing and regenerating) were described for both sexes. A long reproductive season was found, with spawning peaks in August/September and, to a lesser extent, in April/May. Parental care and spawns in parcels (batch spawns) corroborated the raised equilibrium strategy that was effective in this isolated reservoir. This species developed reproductive mechanisms that fit to different environmental conditions, with multiple spawning being associated with lentic environments and asynchronous development of oocytes, which are released over long periods. The reproductive plasticity in reservoirs may be one of the main factors inherent to the successful of colonization and establishment of the peacock bass in the environments in which they were introduced.