Phases Of Gonadal Development Research Articles

Standard histological techniques systematically under‐estimate the size fish start spawning

AbstractBeverton & Holt's (1957) functional definition of maturity in fish (L50), as being the size class in which 50% of individuals begin producing gametes in some proportion to body weight, is widely used in assessment models to estimate spawning stock biomass, and manage the minimum size of capture. Standardized histological techniques for estimating L50 apply physiological definitions that identify cellular or hormonal markers indicating individuals are capable of producing gametes. Few studies have examined how those phases of gonadal development correlate with reproductive behaviour or reproductive output. We compare histological estimates of L50 for 10 species of reef fish from Palau, with the size composition of catches, surveys and spawning aggregations, and interpret those comparisons with simulation modelling. Our study shows that the histological L50 estimates coincide with the size species begin ontogenetically shifting between juvenile and adult habitat, and with the size the smallest individuals join spawning aggregations, but are ~15% smaller than the length at which we infer 50% of individuals begin joining spawning aggregations. This highlights a mismatch between the functional definition of L50 assumed for assessment and management, and the physiological definitions developed for histological studies, which identify the beginning of a sub‐adult adolescent phase, rather than the end, when functional adulthood starts. This definitional mismatch could be causing stock assessments to systematically over‐estimate the reproductive output of fisheries. By considering fish behaviour, we hope to better align estimates of physiological maturation with the estimation of functional reproductive potential required for assessment and management.

Oogenesis and spermatogenesis in round sardinella (Sardinella aurita Valenciennes, 1847) from the eastern part of the Adriatic Sea

Background and purpose: Small pelagic fish species round sardinella (Sardinella aurita) has expanded its habitat during the last few decades towards colder parts of the Mediterranean Sea. In the Adriatic Sea, this investigation is the first attempt to study its gonad development histologically.Materials and methods: S. aurita specimens were sampled monthly from commercial landings of purse seine catches from the eastern part of the Adriatic Sea from November 2007 to January 2009. After biometric parameters were determined, gonads were removed from the fish and weighed. Sex and gonad development were determined macroscopically by the shape and the structure of gonads and afterwards gonads were analysed histologically.Results: The phases of gonadal development of both sexes of S. aurita were: immature, developing, spawning capable, regressing, and regenerating. An annual reproduction cycle based on gamete development revealed five stages of oocyte development: chromatin nucleolar stage, perinucleolar stage, yolk vesicle (cortical alveoli) formation, vitellogenic (yolk) stage, and ripe (mature) stage. Spermatogenesis was described through three stages: spermatocytogenesis (formation of primary spermatocytes from spermatogonia), meiosis (formation of secondary spermatocytes and spermatids) and spermiogenesis.Conclusions: Gonadal histology analyses of both sex of S. aurita indicated summer spawning manner of this species, with a peak in June-August period.

Sex steroid levels in females and males of Brycon orbignyanus throughout different juvenile and adult ages and during induction hormone in the mature females

The levels of reproductive hormones for fish stocked in fish farming ponds can be varying with respect to age and sex. Piracanjuba is an endangered species and broodstock are raised to be used in stocking programs. Therefore, we aimed to describe the plasma levels of the major sex steroids, 17β-estradiol (E2), 17α-hydroxyprogesterone (17α-OHP), testosterone (T) and 11-ketotestosterone (11-KT), in males and females of Brycon orbignyanus of different ages, juveniles with 12 and 24 months and adults with 48 months, and the changes before and after carp pituitary extract application in mature females. Four males and five adult females (48 months) were collected, identified through the sexual dimorphism of the species. For the other ages (12 and 24 months), 20 fish of each age were collected for sex determination through histology. Blood was collected and centrifuged; plasma was obtained for quantification of the plasma profile of E2, 17α-OHP, T and 11-KT. In B. orbignyanus males three phases of gonadal development were observed: immature, developing (12 and 24) and regressing (48). A higher level of E2 (p < 0.05) was observed in immature males, higher levels of T (p < 0.05) were observed in fish of 24 and 48 months. In females of B. orbignyanus blood pre hormonal induction (PI) and post extrusion of oocytes (PE), were collected and stimulus in the production of T, 11-KT and 17α-OHP observed. In females of different ages (12, 24 and 48 months) the E2 showed a higher level (p < 0.05) in relation to other hormones. The T was not observed in 12 and 24 month females, but in 48 month females T and 11-KT observed (p < 0.05), with respect to the 17α-OHP there was no difference in ages observed. In conclusion, E2, 17α-OHP and 11-KT were described for male and female B. orbignyanus from 12, 24 to 48 months of age in the reproductive period. The T was verified in males at 12, 24 and 48 months of age and in females only at 48 months of age. Although there is more concentration of hormones in the reproductive phase at 48 months, in females it is necessary to apply the hormone induction protocol for spawning that is used for rheophilic fish.

Gonadal morphology and difference in reproductive development of two isolated populations of Astyanax rivularis (Teleostei, Characidae).

Individuals of the same species may present different reproductive tactics depending on the environment in which they develop and mature. The present study aimed to define the gonadal development phases of males and females of Astyanax rivularis and to carry out a comparative analysis of the reproductive development of specimens captured in two isolated environments of the São Francisco River basin in Serra da Canastra, Brazil (Point 1: low vegetation and river showing calm and crystalline waters with small well formations; Point 2: current waters, and well-established areas of arboreal vegetation). Thus, the gonads of A. rivularis specimens were collected, fixed and processed with techniques for light microscopy. Five maturation phases of the females' reproductive cycle were established: immature, developing, spawning capable, regressing and regenerating. Three maturation phases of the males' reproductive cycle were observed: spawning capable, regressing, and regenerating. There are differences in the phases of gonadal development of A. rivularis between the two sampling points so that, possibly, animals upstream of the waterfall demonstrate a delay in the reproductive cycle in relation to animals downstream.

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.

Biomonitoring the effects of urban-stream waters on the health status of pale chub (Zacco platypus): A comparative analysis of biological indexes and biomarker levels

The objective of this study was to biomonitor the effects of potential environmental pollutants in urban-stream waters, on fish health. Pale chub (Zacco platypus), a dominant species in the Korea urban stream waters, was chosen and biomonitoring indicators for the different spatial characteristics were tailored in an urban watershed. Biological responses including biotic-somatic index as well as gonadal development phase and plasma steroids levels, and the biochemical responses, ethoxyresorufin-o-deethylase (EROD) and acetylcholinesterase (AChE) activities, were measured. No significant difference was observed in the length–weight relationship between the up-stream waters and the down-stream waters. However, changes in the gonad-somatic index (GSI) levels, plasma 17β-estradiol (E2) levels, and mature oocyte frequencies in the female fish collected during the spawning season were observed in the down-stream waters at each monitoring site. Moreover, intersex condition (testis-ova) in the male fish in down-stream waters was recorded, even if it was just one fish. Although no significant difference was observed in the EROD and AChE activities between the up-stream waters and the down-stream waters, changes in the reproductive biomarker levels, including the GSI levels, plasma E2 levels, and gonadal maturation, lead to variable biomonitoring endpoints between the spatial different sites. These results imply that exposure to the down-stream waters can cause reproductive impairment in wild Z. platypus, individual variability in the biological responses further indicate the reproductive health was affected more by the down-stream waters than the up-stream waters. The finding from this study can provide the biomonitoring endpoint on the wild fish health in urban watershed that is crucial to the early risk assessment of its biological impacts. More multi-biomarkers studies reflecting the variation in the biological organization of wild fish and, therefore, the effects of urban-stream waters in the fish health are warranted.

Reproductive Study of Megapitaria aurantiaca (Sowerby, 1831) (Bivalvia: Veneridae) in Puerto Libertad, Sonora, Mexico

Reproductive aspects of the golden clam Megapitaria aurantiaca in Puerto Libertad, Sonora, Mexico, were analyzed from March 2015 to March 2016. Through histological analysis, five phases of gonadal development were defined (cytolytic, preactive, active, emission, and postactive), the sexual portion was obtained, the relationship between environmental variables (temperature and chlorophyll a) and reproduction was determined through the gonadal index, and the diameter of the oocytes was measured. A seasonal reproductive cycle was exhibited by M. aurantiaca with a spawning phase from April to October which coincided with an increase in the temperature. Spawning clams were observed at a shell length of 69 mm. A sex ratio of 1:1 was recorded. Finally, for the first time, the presence of hermaphroditic organisms was reported for this species.

Gonadal maturity of Crassostrea corteziensis cultivated in the Gulf of California

The gonadal maturation of the pleasure oyster Crassostrea corteziensis during four cultivation cycles (November 2004-June 2005, N4J5; August 2014-February 2016, A14F16; September 2015-December 2016, S15D16; September 2016-August 2017, S16A17) was studied in the southeastern Gulf of California, Mexico. Although C. corteziensis exhibited the typical reproductive phases (undifferentiated or resting, initial gametogenesis, advanced gametogenesis, maturity, spawning and post-spawning), the intensity of reproduction and the timing of the onset of the different phases of gonadal development varied in each cultivation cycle. Reproductive peaks were observed in different months (N4J5 in May, A14F16 in July, S15D16 in May and S16A17 in June) during spring and summer. Spawning correlated with temperature in the N4J5 and A14F16 cultivation cycles but it showed no correlation with chlorophyll-a concentration in any of the cultivation cycles. C. corteziensis presented an opportunistic continuous reproductive strategy with spawning occurring during several months of the year. The modification of the species' reproduction pattern could contribute to the natural settlement of larvae, increasing the natural production of this native oyster resource in the southeast of the Gulf of California, where it has been fished intensively.

Ciclo reproductivo de la almeja roñosa Chione undatella en las costas de la región minera de Santa Rosalía, Baja California Sur, México

Background: The organisms respond to changes in the environment, hence the reproductive process of an organism can be affected as a result of contamination. Chione undatella is a potential resource for fishing and cultivation, which has been intensively exploited for many years on the Mexican Pacific coast. Goals: The main objective of this study was to characterize the reproductive cycle and spawning temporality, estimate the size at first maturity, and determine if there is tissue damage that may have adverse effects on reproduc­tion of C. undatella because of the contamination found in the mining port of Santa Rosalia, Gulf of California. Methods: Through histological analysis, the general condition index (GCI), and environmental parameters, we evaluated aspects of the reproductive biology and health of the frilled venus clam from the coastal area of the port of Santa Rosalia. Results: C. undatella has reproductive activity throughout the year, unrelated to the concentration of chlorophyll-a, or to temperature. An inverse correlation was found between the GCI and the phase of development with higher frequency in females. The size at first maturity is 57 mm LC. In the gonadal tissue (> 80% of the individuals) an infiltration of eosinophilic cells was observed in all phases of gonadal development with an intermediate to abundant intensity (> 60% of the organisms). Conclusions: Although C. undatella has reproductive activity throughout the year, the high prevalence of hemocytic infil­tration in the gonadal tissue suggests a potential deficiency in its reproduction. We recommend more studies be undertaken to confirm this preliminary finding and determine the relationship of the deficiency with the contamination present in the area.

Fecundidad en gónadas maduras de Haliotis fulgens y Haliotis corrugata (Vetigastropoda)

Background: The term fecundity in abalone is defined according to an estimate of its absolute fecundity, which is the number of mature oocytes present in the gonad, or as potential fecundity, i.e., the total number of oocytes present in the gonad. In Mexico, few studies have estimated the fecundity of mollusks and these have been performed on gonads in different phases of gonadal development, obtaining values that are very different or overestimated, for example, values ranging from 80000 to 22 million oocytes in a gonad. Goals: Estimate the fecundity of Haliotis fulgens (blue abalone) and Haliotis corrugata (yellow abalone), using ma­ture gonads and a particle counter (Multisizer 3) to count only mature oocytes. Methods: Each month from October 2011 to February 2013, 30 adult organisms of each species were collected in two localities of Baja California Sur, Mexico (La Bocana and Bahia Tortugas). A histological analysis identified those that were mature females. To obtain the number of eggs per gram, triplicate oocyte counts were performed in a coulter counter Multisizer 3, in a solution of 4 g wet weight of mature oocytes diluted to 50 mL of filtered seawater (μm). Absolute fecundity was calculated by multiplying the total weight of the gonad by the number of mature oocytes present in one gram of oocytes. Results: The fecundity in La Bocana was found to be 2x106 eggs in H. corrugata and H. fulgens, while in Bahia Tortugas it was 4x106 eggs in H. fulgens. Conclusions: This study suggests that estimating absolute fecundity in species with partial spawning, such as H. fulgens and H. corrugata, should be per­formed on all females regardless of the degree of gonadal development. However, only mature oocytes should be considered as an indicator of absolute fecundity. Therefore, the use of an apparatus that counts and measures mature oocytes, such as a particle counter, facilitates and guarantees a good estimate of fecundity.

Profil hormon FSH, LH dan estradiol serta kadar glukosa darah sidat, Anguilla bicolor bicolor (Mc Clelland, 1844) yang dirangsang hormon HCG, MT, E2 dan anti dopamin

This study aims to analyze the hormone profile of FSH, LH and E2 to the eel after exogenous hormone stimulation and blood glucose levels. Six formulated treatment applied with combination of dopamine antagonize 10 mg.mL–1 (A), estradiol (E2) 3 mg.mL–1 + A (EA), metyltestosteron (MT) 3 mg.mL–1 + A (MTA), hCG 2 mg.mL–1 + EA (hEA) and hCG 2 mg.mL–1 + MTA (hMTA), with (F) physiologis 0.9% NaCl to control. Six group eel (200±15g) reared in a concrete tank with a capacity of 3,400 liters and filled with sea water of 35 mg L–1 as much as 2000 liters. Eels injected 1 mL.kg–1 hormone by intramusculary, were feed to apparent satiation daily for 10 weeks. The study used Completely Randomized Design with one treatment factor, namely hormonal factor and its combination. Fish blood that ware directly concentration to FSH, LH and E2, the enhanced significantly high in the blood plasma on treatment hMTA and hEA P&lt;0.05. Glucose concentration in the blood palsma is high enough in a row on a formula hMTA 67.33 mg.dL–1 and significantly different to P&lt;0.05. The result indicates that induction of exogenous hormone (hMTA) improve FSH, LH and E2. FSH and LH profiles show permutation patterns during the development of eel gonad, beginning with the increase of FSH in the early phases of gonadal development. LH profile moves in line with the increase in E2 during gonadal maturation process eels (A. bicolor bicolor), with blood glucose levels in the normal range. AbstrakThis study aims to analyze the hormone profile of FSH, LH and E2 to the eel after exogenous hormone stimulation and blood glucose levels. Six formulated treatment applied with combination of dopamine antagonize 10 mg.mL–1 (A), estradiol (E2) 3 mg.mL–1 + A (EA), metyltestosteron (MT) 3 mg.mL–1 + A (MTA), hCG 2 mg.mL–1 + EA (hEA) and hCG 2 mg.mL–1 + MTA (hMTA), with (F) physiologis 0.9% NaCl to control. Six group eel (200±15g) reared in a concrete tank with a capacity of 3,400 liters and filled with sea water of 35 mg L–1 as much as 2000 liters. Eels injected 1 mL.kg–1 hormone by intramusculary, were feed to apparent satiation daily for 10 weeks. The study used Completely Randomized Design with one treatment factor, namely hormonal factor and its combination. Fish blood that ware directly concentration to FSH, LH and E2, the enhanced significantly high in the blood plasma on treatment hMTA and hEA P&lt;0.05. Glucose concentration in the blood palsma is high enough in a row on a formula hMTA 67.33 mg.dL–1 and significantly different to P&lt;0.05. The result indicates that induction of exogenous hormone (hMTA) improve FSH, LH and E2. FSH and LH profiles show permutation patterns during the development of eel gonad, beginning with the increase of FSH in the early phases of gonadal development. LH profile moves in line with the increase in E2 during gonadal maturation process eels (A. bicolor bicolor), with blood glucose levels in the normal range.

Gonadal Maturation and Histological observations of S. curvifrons in River Jhelum Kashmir

The objective of the present study is to describe the phases of gonadal development and determine the spawning season of Schizothorax curvifrons in River Jhelum Kashmir. A total of 298 fish specimen were studied to analyse the gonadosomatic index and maturity stages of S. curvifrons. Five maturity stages namely Immature phase, Preparatory phase, Maturing phase, Ripe/spawning phase and Spent phase were observed in the gonads. Based on GSI values and gonadal conditions, April to June appears to be the spawning season for S. curvifrons

Patterns of reproduction and growth of the catfishIheringichthys labrosus(Lütken, 1874) after a reservoir formation

This work contributes to the knowledge of the reproduction, growth parameters and mortality rates of Iheringichthys labrosus in a newly-formed reservoir. A total of 554 males and 1227 females were collected over 12 consecutive months, 1998–1999, from sites in the Corumbá Reservoir, Brazil, using gillnets (meshes: 2.4–16 cm). Information on each individual, i.e. standard length (cm), weight (g), sex, and gonadal development phase was recorded. The pectoral spines were removed to estimate age. The number of juveniles and adults, males and females, reproductive sites and seasons were estimated. First maturation length was estimated using a likelihood function fitted by binomial distribution. Growth parameters were estimated using the von Bertalanffy equation. Total instantaneous mortality was obtained through a linearized catch curve method. Standard length varied from 6.0 to 20.5 cm. Growth showed negative allometry for both sexes. The reproduction period was August to December in all environments sampled and first maturation length was 11.5 cm. All individuals were adults with 17.0 cm standard length. Ages varied from zero to 7 years. Asymptotic length, growth coefficient and t0 for the entire population were 27.79 cm, 0.12 and −2.64, respectively. Instantaneous and annual mortality rates were 0.90 and 0.59, respectively.

Reproductive traits of the pompano, Trachinotus ovatus (Linnaeus, 1758), in the north-western Mediterranean

This study describes for the first time the reproductive traits of the warm-water pompano, Trachinotus ovatus. Specimens were sampled from landings by artisanal fishing vessels in the NW Mediterranean. Monthly collections, from July 2010 through to September 2012, yielded 226 individuals (118 females and 108 males). The size at 50% maturity (L50) was estimated at 30.9 and 29.1 cm TL for females and males, respectively. Specific reproductive traits, such as oocyte size-frequency distributions, presence of recent post-ovulatory follicles along with oocytes in the final phases of gonadal development, and massive atresia in post-spawning individuals, indicated that pompanos are multiple batch spawners with asynchronous oocyte development and indeterminate fecundity. Monthly variations in the gonadosomatic index and in the phases of gonadal development indicated July and August as the spawning season. There were also noticeable inter-annual variations in spawning phenology, mean diameters of the oocytes, relative batch fecundity and eggs quality, all of which corresponded to changes in sea surface temperatures. This study enhances our understanding of the need for research into the reproduction of warm-water species, which are currently expanding into the increasingly warmer waters of the world's more northerly seas and oceans.

Juvenile fish use of the shallow zone of beaches of the Cananéia-Iguape coastal system, southeastern Brazil

Abstract The purpose of the present study is to describe the juvenile fish use of the shallow zone of beaches of the Cananéia-Iguape coastal system, São Paulo, Brazil, analyzing its occurrence period and the patterns of utilization for the most abundant species. Using a beach seine monthly for one year, we sampled 13861 individuals, of 57 species and 24 families. The fish species used the study area for different proposes: Atherinella brasiliensis was sampled in all phases of gonadal development and considered as resident, juveniles of Trachinotus goodei used the beaches for growth and juveniles of Mugil curema and Mugil liza used the beaches as a route from the ocean to the estuary. Our results showed the importance of the sandy beaches for juvenile fish, especially in spring and summer when most juveniles occur and recruit. Unfortunately, this is the period of the most intense tourist activity. As many of the species studied are commercially important, this study highlighted the necessity of coastal habitat preservation for better fishery management.

Sex determination and disorders of sex development according to the revised nomenclature and classification in 46,XX individuals

There have been considerable advances concerning understanding of the early and later stages of ovarian development; a number of genes have been implicated and their mutations have been associated with developmental abnormalities. The most important genes controlling the initial phase of gonadal development, identical in females and males, are Wilms' tumor suppressor 1 (WT1) and steroidogenic factor 1 (SF1). Four genes are likely to be involved in the subsequent stages of ovarian development (WNT4, DAX1, FOXL2 and RSPO1), but none is yet proven to be the ovarian determining factor. Changes in nomenclature and classification were recently proposed in order to incorporate genetic advances and substitute gender-based diagnostic labels in terminology. The term "disorders of sex development" (DSD) is proposed to substitute the previous term "intersex disorders". Three main categories have been used to describe DSD in the 46,XX individual: 1) disorders of gonadal (ovarian) development: ovotesticular DSD, previously named true hermaphroditism, testicular DSD, previously named XX males, and gonadal dysgenesis; 2) disorders related to androgen excess (congenital adrenal hyperplasia, aromatase deficiency and P450 oxidoreductase deficiency); and 3) other rare disorders. In this mini-review, recent advances concerning development of the genital system in 46,XX individuals and related abnormalities are discussed. Basic embryology of the ovary and molecular pathways determining ovarian development are reviewed, focusing on mutations disrupting normal ovarian development. Disorders of sex development according to the revised nomenclature and classification in 46,XX individuals are summarized, including genetic progress in the field.

Appearances and chronological changes of mummichog Fundulus heteroclitus FSH cells and LH cells during ontogeny, sexual differentiation, and gonadal development

To examine relationships between gonadal stages and the initial appearance and subsequent development of gonadotrophs, hatched larvae of the mummichog Fundulus heteroclitus were reared until first maturity under suitable conditions for maturation (20°C–16L). Evident FSH cells generally appeared 1–2 weeks after hatching (wah), around or slightly before the morphological sex differentiation which occurred at 2wah. During this period, 3β-hydroxysteroid dehydrogenase positive cells also appeared in the gonads. While FSH cells existed throughout the early phases of gonadal development such as cortical alveoli formation and basic spermatogenesis, LH cells appeared later (6–12wah), after the commencement of the early gonadal development. Both FSH cells and LH cells were abundant at 36wah when the fish had attained full maturity. These results indicate the possibility that FSH is responsible for gonadal differentiation by inducing steroidogenesis in the gonads, implying the importance of FSH on the early phases of gonadal development. These results also suggest cooperation of FSH and LH in later phases of gonadal development such as yolk globule accumulation and active spermatogenesis. The mode of changes in the abundances of the gonadotrophs according to the gonadal development was somewhat different from previously observed changes during the annual reproductive cycle in adult mummichog. Possible complementary roles of the two GTHs in vitellogenesis and spermatogenesis may be involved in the difference by providing flexibility to the controlling mechanism.

Adrenal–kidney–gonad complex measurements may not predict gonad‐specific changes in gene expression patterns during temperature‐dependent sex determination in the red‐eared slider turtle (Trachemys scripta elegans)

Many turtles, including the red-eared slider turtle (Trachemys scripta elegans) have temperature-dependent sex determination in which gonadal sex is determined by temperature during the middle third of incubation. The gonad develops as part of a heterogenous tissue complex that comprises the developing adrenal, kidney, and gonad (AKG complex). Owing to the difficulty in excising the gonad from the adjacent tissues, the AKG complex is often used as tissue source in assays examining gene expression in the developing gonad. However, the gonad is a relatively small component of the AKG, and gene expression in the adrenal-kidney (AK) compartment may interfere with the detection of gonad-specific changes in gene expression, particularly during early key phases of gonadal development and sex determination. In this study, we examine transcript levels as measured by quantitative real-time polymerase chain reaction for five genes important in slider turtle sex determination and differentiation (AR, ERalpha, ERbeta, aromatase, and Sf1) in AKG, AK, and isolated gonad tissues. In all cases, gonad-specific gene expression patterns were attenuated in AKG versus gonad tissue. All five genes were expressed in the AK in addition to the gonad at all stages/temperatures. Inclusion of the AK compartment masked important changes in gonadal gene expression. In addition, AK and gonad expression patterns are not additive, and gonadal gene expression cannot be predicted from intact AKG measurements.

Evidence of gonochorism in a grouper, Mycteroperca rosacea, from the Gulf of California, Mexico

The sexual pattern and sexual development of the leopard grouper, Mycteroperca rosacea, were investigated from 483 specimens collected from the Gulf of California, Mexico. Histological and population data indicated a gonochoric sexual pattern. Some juveniles passed through an immature bisexual phase of gonadal development, but no evidence of post-maturational sex change was found. The immature bisexual phase is believed to be associated only with male development. The size distribution and size at sexual maturity were similar for both males and females. In accordance with predictions of the size-advantage model, the gonochoric sexual pattern of M. rosacea is likely influenced by its group-spawning mating system.

Cloning of European eel ( Anguilla anguilla) FSH-β subunit, and expression of FSH-β and LH-β in males and females after sex determination

The European eel ( Anguilla anguilla) is a catadromic teleost species with a complex life cycle, both in sea and freshwater environments. The sex determination phase of gonadal development occurs in a freshwater environment. Polymorphism occurs in increasing rates with respect to gender. While males stop growing at approximately 150 g, females continue to grow to being much larger. In this study, we cloned the cDNA FSH-β subunit of the European eel ( A. anguilla), and measured the mRNA levels of FSH-β and LH-β in males and females after sex determination. The FSH-β subunit cDNA consisted of 1068 bp, encoding a 127 amino acid peptide. A comparison between European and Japanese eels of the FSH-β amino acid sequence showed 98% similarity.