Gonad morphology and sex succession in the protogynous hermaphrodite Hemanthias vivanus (Jordan and Swain)

Hemanthias vivanus , an anthiine serranid common on deep (70–80 m) reefs off eastcentral Florida, is shown to be a protogynous hermaphrodite with observed size ranges as follows: female, 49–77 mm S.L.; transitional 65–74; male, 65–96. Sexes are distinguishable externally as the dorsal spine filaments elongate and colour pattern changes with sex succession. In females, lamellae extend from the lateral and dorsal walls of the bilobed ovary into the lumen. Ova mature within the lamellae and at ovulation pass centrally into the lumen, posteriorly into a common post-ovarian sinus, and exit through the oviduct. Females possess a discrete tissue band (testicular islets) at the border of the alamellar region, from which testicular tissue proliferates during sex succession and replaces the regressing ovarian tissue. In males, spermatozoa are formed in crypts which drain peripherally into a sperm sinus which forms by rupture of muscular and connective tissue layers surrounding the gonad. The sperm sinus drains posteriorly into the vas deferens which is formed by rupture of collagenous tissue surrounding and posterior to the now vestigial post-ovarian sinus. The vas deferens and mesonephric duct join within the urogenital papilla. Two smooth muscle bands associated with the infracarinalis medius muscle bands, the collagenous tissue surrounding the gonoduct, and the intestinal lining are implicated in the extrusion of gametes, urine and faeces. At sex succession, ova are resorbed in one of at least three pathways depending upon their stage of development at the onset of sex transformation: unovulated mature ova become encysted with fibroblasts and invaded by cells of an unknown origin; non-mature yolky ova are invaded and phagocytized by granulosa cells; non-yolky ova are not invaded but fragment.     

Diplectrum radiale (Quoy & Gaimard, 1824) (Serranidae): A rare case of simultaneous hermaphroditism in a teleost fish

This study generates, for the first time, information on the reproductive traits of the simultaneous hermaphrodite Diplectrum radiale. The specimens were captured bimonthly in two distinct ecosystems along the south‐eastern Brazilian coast. The mature ovotestes were removed, preserved in formalin and examined using histological techniques. The results revealed indeterminate fecundity with asynchronous ovarian organization. All spermatogenesis occurs within cysts, and the spermatogonial distribution indicated an unrestricted testicular type. The testicular and ovarian tissues were separated from each other by different ducts, indicating no possibility of internal self‐fertilization. The hydrated oocytes were stored in the accessory reproductive structure for at least 24 hr. The presence of atretic hydrated oocytes within this structure and the positive periodic acid–Schiff reaction of the villi‐like projections revealed the function of the ovary sinus as absorbing unspawned oocytes. The relative batch fecundity ranged from 62 to 209 oocytes/g (126 ± 42) for specimens from the coast and from 52 to 203 oocytes/g (113 ± 57) for those sampled in the estuary. The potential batch fecundity was linearly related to size, weight, and the gonadosomatic and hepatosomatic indices, revealing that these parameters significantly affect the reproductive potential of D. radiale.     

Structure of the reproductive system of the squid Thysanoteuthis rhombus (Cephalopoda: Oegopsida)

The structure of the reproductive systems of mature males and females of the nektonic, oceanic squid Thysanoteuthis rhombus are described. The main peculiarities of the female system are relatively low capacity oviducts, set in a tight spiral, and hypertrophically developed oviducal glands with a very large second section. The male reproductive system is characterized by a long, narrow Needham's sac containing 10–15 large spermatophores 80–100 mm in length. The mesentery supporting the gonad, and protruding into it dorsally, is a characteristic feature in both sexes. The hectocotylus structure differs markedly from that in other squids and resembles that of sepiids. The reproductive system of T. rhombus possesses primitive features (pattern of gonad attachment and hectocotylus) but mostly secondary characters (small oviducts, very large oviducal glands and ovary). The complex morpho-ecological adaptations of T. rhombus are reflected in the distinctive features of the reproductive system.     

Morphology and gonad development of normal soldiers and reproductive soldiers of the termite Zootermopsis nevadensis nevadensis (Isoptera, Archotermopsidae)

Reproductive or neotenic soldiers of the Archotermopsid Zootermopsis nevadensisnevadensis (Hagen) are compared to sterile soldiers and primary male reproductives. Several head capsule morphometrics correlate significantly with gonad size across all forms and both sexes of soldiers. The easily observed field character of ratio of mandible length to labrum length is a consistent and reliable feature of head capsule external morphology for predicting gonad development and reproductive potential of soldier forms regardless of age, sex, or live weight.     

Seasonal variations in biochemical composition during the reproductive cycle of the veined rapa whelk Rapana venosa (Valenciennes, 1846) from the northern coast of China

Seasonal variations in the biochemical composition of Rapana venosa in relation to reproductive cycle and environment on the northern coast of China were investigated from March 2012 to February 2013. The results indicated that R. venosa has an annual reproductive cycle with synchronized gonad development in both females and males. Gametogenesis was initiated in September and gametes developed slowly during the winter, followed by rapid gonad development during spring and summer. Most individuals from this study were sexually mature between May and June, and gamete release occurred mainly between May and August. The peak of spawning was found in July and the recovery of the gonad was observed between August and November. The key biochemical components including glycogen, protein and lipid were analysed in four tissues, specifically the gonad, digestive gland, mantle and foot. The declining glycogen content in the gonad, digestive gland and mantle during maturation suggested that glycogen was consumed during the development of the gonad. Lipids and protein can be stored in the digestive gland and used during the winter in a period of food shortage. The protein and lipid contents in the ovaries increased during gonad development, which suggested that the protein and lipid had been accumulated as vitellin in oocytes.     

Ultrastructure of the gametogenesis of the common Mediterranean starfish,Echinaster (Echinaster) sepositus

Echinaster (Echinaster) sepositus is one of the most abundant sea stars in western Mediterranean rocky bottoms, yet its reproductive biology remains virtually unknown. Here we report the ultrastructure of its gametogenesis over 2 consecutive years. It is a gonochoric species with an annual reproductive cycle spawning gametes in late summer and early autumn. Each arm of every individual contained two gonads (dark red in females and yellow in males). In both sexes, the gonad was a single, large sac composed of several smaller sacs. The gonad wall consisted of two multilayered sacs, outer and inner, separated by the genital haemal sinus. The histology of the gonad wall was consistent with that found in other asteroids. Oogenesis was continuous during the year, but eggs were spawned only in late summer. Oocytes were in close relationship with follicular cells that are suggested to transfer nutrients to the oocytes. Spermatogenesis was restricted to 5–6 months in spring-summer. It occurred in columns with an axial interstitial cell supporting each column, and producing processes towards the lumen that remained connected to spermatogenic cells by intercellular junctions. Developing sperm cells were found along the length of the column, while spermatozoa were found free in the testis lumen. Spermatogenesis followed the pattern described for echinoderms, to give rise to an acrosome-bearing, round-shaped spermatozoon. The histology and cytology of the reproductive process in E. sepositus followed the general pattern found for asteroids.     

Reproduction and lipids in the sub-Antarctic limpet Nacella (Patinigera) macquariensis Finlay, 1927

The reproductive cycle of the sub-Antarctic limpet, Nacella (Patinigera) macquariensis Finlay, 1927 is described from monthly gonad indices and slide smears of gonadal tissue. Two populations were sampled, from the eulittoral zone and at ≈4 m depth into the sublittoral zone. Gametogenesis started 2 months earlier in the eulittoral zone population; the breeding period, however, was sufficiently long to overlap in the two populations. This phase difference in reproductive cycles is discussed with respect to possible genetic divergence and correlation between timing within the reproductive cycle and environmental factors. Lipid was a prominent component of both the digestive gland and the gonad, but not of the foot. Changes in lipid levels during the reproductive cycle indicated that the digestive gland stored lipids which were transferred to the gonad during gametogenesis.     

A maturity index for holothurians exhibiting asynchronous development of gonad tubules

The gonad morphology of the sea cucumber Isostichopus badionotus, collected during the months of May to November 1996 in Morrocoy Bay on the northwestern Venezuelan coast, was analyzed. The gonadal cycle was characterized by five stages of development: post-spawning, recovery, growth, advanced growth and maturity. Maturation did not proceed at the same pace in all gonad tubules of any one animal. Due to this asynchronous gonad development an Individual Weighted Maturity Index (IWMI) was devised to determine reproductive state. It was calculated from the proportion of the different tubule stages observed in each specimen. The maximum value attainable is 5 if all tubules are in the mature stage. Towards the months of July and August, most, but not all, of the ovarian and testicular tubules had reached maturity as indicated by IWMI values of 4.32 and 4, respectively. IWMI represents a quantitative estimation of gonad maturation in holothurians exhibiting asynchronous development as it revealed the maturation pattern underlying gonadal chronological development.     

Karyotype differentiation in Chromaphyosemion killifishes (Cyprinodontiformes, Nothobranchiidae). III: extensive karyotypic variability associated with low mitochondrial haplotype differentiation in C. bivittatum

We investigated chromosomal evolution in the African killifish species Chromaphyosemion bivittatum using a combination of cytogenetic and phylogenetic methods. Specimens from five populations were examined by conventional Giemsa staining as well as sequential chromosome banding with 4',6-diamidino-2-phenylindole (DAPI), chromomycin A(3) (CMA(3)), AgNO(3)-staining and C-banding. The cytogenetic analysis revealed variability in 2n ranging from 2n = 29 to 2n = 36 and in NF ranging from NF = 38 to NF = 44. Two populations showed an extensive chromosomal polymorphism (2n = 29-34, NF = 44 and 2n = 32-34, NF = 38-42, respectively). Karyotypic variability within and among populations was mainly due to Robertsonian translocations and heterochromatin additions, and chromosome banding patterns suggested that both types of chromosomal rearrangements were related to the presence of AT-rich heterochromatin. A phylogenetic analysis of the partial mitochondrial (mt) cytochrome b gene, using specimens from eleven populations, revealed a low degree of haplotype differentiation, which suggested a relatively recent divergence of the populations examined. This finding conformed to the low degree of morphological differentiation observed among C. bivittatum populations and might indicate fast chromosomal evolution. The high karyotypic variability may be caused by an elevated chromosomal mutation rate as well as certain aspects of the mating system and population dynamics of C. bivittatum facilitating the fixation of new chromosomal variants.     

The gonad maturation and size structure of the population of abundant planktonic predator <Emphasis Type="Italic">Eukrohnia hamata</Emphasis> (Möbius, 1875) (Chaetognatha) in the Eurasian basin of the Arctic Ocean in summer

The size structure of the population, morphology of the reproductive system, and gonad maturation of the chaetognath Eukrohnia hamata (Möbius, 1875) (Chaetognatha) were studied for the first time from zooplankton samples collected in Fram Strait and the deep Eurasian basin of the Arctic Ocean north of the Kara and Laptev seas in the summers of 1995 and 1997. We describe the gonad morphology and the progress of gonad maturation in male and female specimens and propose a system for classification of gonad maturity stages. During the Arctic summer, the population was represented by individuals ranging in size from 2 to 37 mm. The newly hatched young (2.0–3.5 mm long) and juveniles (4.0–12.5 mm long) dominated numerically (30 and 50% of the population, respectively). Our results indicate that E. hamata successfully matures and reproduces in the Arctic basin, but mature individuals make up less than 1% of the population in the summer against the background of juvenile abundance.     

The analysis of data in studies of invertebrate reproduction. I. Introduction and statistical analysis of gonad indices and maturity indices

As studies of invertebrate reproduction are expensive in time and money, there is a need to make the maximum use of the resultant data. It is also important to ensure that the conclusions of a study can be legitimately drawn from the data. Both of these factors necessitate the development of appropriate statistical methodology in reproductive biology.

The structure of data in reproductive biology is detailed, and methods of analysing gonad indices and maturity indices are reviewed. Although gonad indices have been widely used, they are only really satisfactory in species with strong seasonality of reproduction. There is, however, considerable scope for extracting more information from gonad indices than is usually obtained. The value of periodic regression as a tool to aid the understanding of reproductive cycles deserves further investigation.

If microscopic preparations of the gonads are being produced to estimate maturity indices, it is definitely worthwhile measuring oocyte sizes in the females, as the amount of information gained is considerable.     

Life history of a simultaneously hermaphroditic fish,Diplectrum formosum

Sand perch Diplectrum formosum were collected in the Atlantic Ocean waters off the south‐eastern U.S. for life history analyses between April 2001 and July 2004 and ranged in size from 63 to 236 mm standard length (L_S) and 0–8 years of age. Diplectrum formosum are simultaneous hermaphrodites that reach 50% sexual maturity at 12·2 months and 122·8 mm L_S for testicular tissue and 13·6 months and 129·3 mm L_S for ovarian tissue. The gonad contains ovarian and testicular tissue separated by a thin basement membrane, with no means of internal self‐fertilization. Spawning females were found between March and January with a peak of spawning activity in May and a realized spawning periodicity of 2 days, equivalent to a maximum of 168 spawning events per year. Fish with testicular tissue in spawning condition were obtained throughout the year in every month sampled with a maximum frequency between June and September. There were also trends indicating that testicular tissue was more likely to be in spawning condition in the presence of hydrated oocytes within the accessory structure. This may indicate the use of the accessory structure as a storage site for hydrated oocytes until a mate can be located.     

Observation and establishment of gonad development stages in polyplacophorans (Mollusca): Chiton (Chiton) articulatus a case study

Gonad development stages (GDS) and, subsequently, the reproductive cycle are described by performing histology of some gonad portions. In polyplacophorans, gametogenesis is not enough to define GDS; further anatomical gonad features are relevant. In most adult polyplacophorans, the gonad is a simple anatomical structure that resembles and operates as one single gonadal acinus without glandular structure. These features have gone unnoticed causing inaccurate GDS assignment and, consequently, imprecise reproductive season in polyplacophorans. Here, dissection protocols that allow extracting a compact gonad are established. Emphasizing the anatomical structure of the whole gonad and the displacement of gametes, five GDS were assigned to both sexes of Chiton (Chiton) articulatus: I‐goniogenesis, II‐development, III‐ripe, IV‐spawning, V‐rest. Tissue platelets contribute importantly to GDS assignment and even help distinguishing between males and females. Neither a randomly selected portion of gonad nor a longitudinal section are recommended because it leads to misinterpretation higher than 50% in determining GDS and besides ignores displacement of gametes. A panoramic sweep across a complete transverse‐section of each gonad was validated as the best option for establishing GDS. This new methodology was tested on several polyplacophorans species, and seems generally applicable for histological assessment of reproductive cycle and reproductive season in polyplacophorans.     

Delayed gametogenesis of Mya arenaria in the Saguenay fjord (Canada): a consequence of endocrine disruptors?

The Saguenay fjord located in Canada on the north coast of the Saint-Lawrence Estuary, is well known for its multiple contaminations following a linear distribution upstream to downstream. Mya arenaria is well established in the fjord and potentially exposed to persistent sediment contamination as an endobenthic bivalve. From May to October 1997, clams energy storage and utilization in the gonad was shown to be closely linked with reproduction. Wherever the sampling site location in the fjord, a seasonal pattern is evident for lipid and glycogen levels in the gonad, this, reflecting the vitellogenic process. Nevertheless, in comparison with energy status and gametogenesis of clams collected on the north coast of the Saint-Lawrence Estuary, clams located in the fjord have to face limited nutritive conditions resulting in a single and shorter reproductive period. Although environmental factors could explain differences in physiological condition and reproductive status observed between clams from the fjord and the estuary, our results can discriminate clams from the upper part of the fjord, according to a delayed gametogenesis, concomitant with significant higher gonad glycogen concentrations observed in June 1996 and 1997. A persistent dysfunction of a vitellogenic process is suspected to be due to the exposure to anti-estrogenic contaminants.     

An ultrastructural study of relationships between the ovarian haemal system,follicle cells,and primary oocytes in the sea star,Asterias rubens

Summary The genital haemal sinus, present throughout the gonad wall of sea stars, is supposed to be the site of ultimate accumulation of nutrients for the germinal epithelium. Early vitellogenic pear-shaped oocytes are attached to this sinus by stalk-like processes. The ultrastructure of this association and of the oocyte-follicle cell complex is described with emphasis on mechanisms involved in oocyte nutrition.The genital haemal sinus, and sometimes portions of the surrounding genital coelomic sinus, contain a fine granular ground substance and amoeboid cells. Material similar to the haemal ground substance also fills vacuities in the inner basal laminae of the haemal sinus and intervenes between this layer and adjacent germinal and follicle cells in the ovarian lumen.Vitellogenesis is first detectable as numerous vacuoles accumulate within the oocyte-stalk near the haemal sinus; they contain flocculent material and often fuse with adjacent lysosome-like vacuoles. As vitellogenesis proceeds, oocytes develop complex and tenuous connections with the haemal sinus. These consist of a network of pseudopodia that interdigitate with thin sheet-like extensions of follicle cells. These cells are attached to the oolemma by microfilamentous processes and contain regularly arranged concentrations of glycogen granules and well developed rough endoplasmic reticulum.It is concluded, (1) that follicle cells provide each oocyte with a compartmentalized microenvironment within the ovarian lumen, (2) that such compartments are intimately associated with the nutrient laden haemal sinus, and (3) that nutritive and vitellogenic substances, derived extragonadally and stored temporarily in the ovarian wall, can pass through the oocyte-stalk.     

Comparative morphology and sex identification of the reproductive system in formalin-preserved sea turtle specimens

Sex identification in young sea turtles is challenging. Sea turtle neonates lack external dimorphic characteristics and heteromorphic sex chromosomes. We compared the morphology of the gonads and reproductive ducts of dead formalin-preserved hatchling and post-hatchling Caretta caretta, Dermochelys coriacea, and Chelonia mydas and identified sex-specific differences in these structures that are useful in assigning sex. We tested 11 gross gonadal and reproductive duct characteristics in 57 neonate sea turtles and verified the sex by histological examination. A suite of four characters was found to reliably indicate sex in the three species considered: paramesonephric duct size, mobility of the duct, presence of a complete lumen and gonad mobility. Additionally, gonad shape and edge form were dependable sex-specific characters in cheloniids but not in D. coriacea. Together, these morphological characteristics provide new and reliable methods to quickly distinguish sex in preserved neonate sea turtles without using more extensive histological methods.     

Reproductive patterns of the Pacific oyster Crassostrea gigas in France

Summary

In France, national management programs focus research on understanding reproductive factors in Crassostrea gigas to confront problems of the oyster industry. However, little information has been documented in which reproductive patterns include sexual changes. The reproductive cycle of oysters at three sites of the Atlantic coast of France was examined from 1996 to 1998, and the seasonal variations in oocyte size-frequencies, and sex ratio were described. The results showed a synchronism within the population concerning reproductive behavior. Young oocytes are generated after spawning and show no apparent changes during winter. Growth of oocytes begins in spring and cells reach maturity in April-May and are ready for a single spawning season in June-July. Oocytes that were not released during spawning are reabsorbed within the gonad. The significant difference between sites is that spawning occurred 1 month later in the southern area. A modal analysis showed that oocyte populations in the sample individuals are primordially bimodal, but with polymodal occurrences in June-July, in some cases. Irregular alternative sexuality was detected at all sites, and hermaphrodites appear to be a transition phase that allows changes from male to female during early spring. Previous observations, together with the study of the development of oocyte cohorts over time, permit a hypothetical model concerning the kinetics of gametogenesis in C. gigas. The model suggests that primary oocytes are generated from energy supplied from degenerating, as well as young oocytes that do not reach the mature stage within the gonad during autumn-winter. It seems that, during vitellogenesis, there is disintegration of smaller cells coupled with transfer of energy to the larger oocytes, which continue to grow and mature.     

Timing of avian reproduction in unpredictable environments

Organisms living in periodically varying environments adjust their life history events to the changes in food availability. When these changes are not entirely predictable animals face a trade-off between maintaining physiological preparedness (which can be costly) and being unprepared (which decreases the chances of successful reproduction). To investigate this problem, we developed an optimal annual routine model of gonad regulation in birds. Most birds regress their reproductive organs during non-breeding periods, but to start breeding again they need to have functional gonads. Maintaining the gonads in this state is costly, but because it takes time to achieve this state, if gonads are not functional the bird may miss a possible breeding opportunity. We explore the resolution of this trade-off in environments where favorable periods can occur at any time of the year and variability in the length of good and bad periods can be altered. Consistent with empirical studies of reproductive behavior in unpredictable environments, we find that birds maintain the gonads partially activated during unfavorable conditions in many cases. However, gonad regulation may differ strikingly depending on the consistency of the good and bad periods. Furthermore, seasonal changes in food availability lead to the entrainment of reproduction and the segregation of the breeding and non-breeding season, even if the magnitude of seasonality is small compared to the degree of environmental fluctuations. These results indicate that several aspects of the environment need to be taken into account to understand reproductive behavior in unpredictable environments. Given that the trade-off between the costs and benefits of maintaining physiological preparedness is not limited to birds, our results have implications for understanding behavioral flexibility in other organisms as well.     

Identification of mutations that delay somatic or reproductive aging of Caenorhabditis elegans

Aging is an important feature of animal biology characterized by progressive, degenerative changes in somatic and reproductive tissues. The rate of age-related degeneration is genetically controlled, since genes that influence lifespan have been identified. However, little is known about genes that affect reproductive aging or aging of specific somatic tissues. To identify genes that are important for controlling these degenerative changes, we used chemical mutagenesis to perform forward genetic screens in Caenorhabditis elegans. By conducting a screen focused on somatic aging, we identified mutant hermaphrodites that displayed extended periods of pharyngeal pumping, body movement, or survival. One of these mutations is a novel allele of the age-1 gene. age-1 encodes a phosphatidylinositol-3-kinase (PI3K) that functions in the insulin/insulin-like growth factor-1 (IGF-1) signaling pathway. age-1(am88) creates a missense change in the conserved PIK domain and causes dramatic extensions of the pharyngeal pumping and body movement spans, as well as a twofold extension of the lifespan. By conducting screens focused on reproductive aging in mated hermaphrodites, we identified mutants that displayed increased progeny production late in life. To characterize these mutations, we developed quantitative measurements of age-related morphological changes in the gonad. The am117 mutation delayed age-related declines in progeny production and morphological changes in the gonad. These studies provide new insights into the genetic regulation of age-related degenerative changes in somatic and reproductive tissues.     

Estimation of gonad volume, fecundity, and reproductive stage of shovelnose sturgeon using sonography and endoscopy with application to the endangered pallid sturgeon

Most species of sturgeon are declining in the Mississippi River Basin of North America including pallid (Scaphirhynchus albus F. and R.) and shovelnose sturgeons (S. platorynchus R.). Understanding the reproductive cycle of sturgeon in the Mississippi River Basin is important in evaluating the status and viability of sturgeon populations. We used non‐invasive, non‐lethal methods for examining internal reproductive organs of shovelnose and pallid sturgeon. We used an ultrasound to measure egg diameter, fecundity, and gonad volume; endoscope was used to visually examine the gonad. We found the ultrasound to accurately measure the gonad volume, but it underestimated egg diameter by 52%. After correcting for the measurement error, the ultrasound accurately measured the gonad volume but it was higher than the true gonad volume for stages I and II. The ultrasound underestimated the fecundity of shovelnose sturgeon by 5%. The ultrasound fecundity was lower than the true fecundity for stage III and during August. Using the endoscope, we viewed seven different egg color categories. Using a model selection procedure, the presence of four egg categories correctly predicted the reproductive stage ± one reproductive stage of shovelnose sturgeon 95% of the time. For pallid sturgeon, the ultrasound overestimated the density of eggs by 49% and the endoscope was able to view eggs in 50% of the pallid sturgeon. Individually, the ultrasound and endoscope can be used to assess certain reproductive characteristics in sturgeon. The use of both methods at the same time can be complementary depending on the parameter measured. These methods can be used to track gonad characteristics, including measuring Gonadosomatic Index in individuals and/or populations through time, which can be very useful when associating gonad characteristics with environmental spawning triggers or with repeated examinations of individual fish throughout the reproductive cycle.