Fishery Induces Sperm Depletion and Reduction in Male Reproductive Potential for Crab Species under Male-Biased Harvest Strategy

Sperm depletion in males can occur when polygynous species are intensively exploited under a male-biased management strategy. In fisheries involving crabs species, the effects of this type of management on the reproductive potential is far from being understood. This study tests whether male-biased management of the principal Chilean crab fishery is able to affect the potential capacity of Metacarcinus edwardsii males to transfer sperm to females. Five localities in southern Chile, recording contrasting crab fishery landing, were selected to assess the potential of sperm depletion triggered by fishery. Seasonally, male crabs from each locality were obtained. Dry weight and histological condition of vasa deferentia and the Vaso-Somatic Index (VSI) were determined in order to use them as proxies for sperm depletion and male reproductive condition. A manipulative experiment was performed in the laboratory to estimate vasa deferentia weight and VSI from just-mated males in order to obtain a reference point for the potential effects of the fishery on sperm reserves. Sperm storage capacity is significantly affected by fisheries; during the mating season vasa deferentia from localities with low fishery intensity were heavier than those from high intensity fisheries, and these differences were even more evident in large males. Histological section showed that this disparity in vasa deferentia weight was explained principally by differences in the quantity of spermatophores rather than other seminal material. VSI was always higher in males from localities with low fishery intensity. Males from localities with high fishery intensity showed little capacity to recover sperm reserves and the VSI of these males remained below the values of the just-mated males. Detriment in the capacity of males to transfer sperm is the first step to sperm limitation in an exploited population, thus detection of sperm depletion can be an alert to introduce changes in the current management of crabs.     

Comparative study of the structure of the reproductive system of dwarfish males of Glyphina betulae (Linnaeus, 1758) and Anoecia (Anoecia) corni (Fabricius, 1775) (Hemiptera, Aphididae)

The morphology and ultrastructure of the male reproductive system of dwarfish males of the monoecious aphid species Glyphina betulae (subfamily Thelaxinae) and the heteroecious species Anoecia (Anoecia) corni (subfamily Anoeciinae) are described. The testicular follicle of these species has the form of a single sac, the proximal parts of the vasa deferentia are slightly (G. betulae) or strongly (A. (A.) corni) expanded, the accessory glands are sack-shaped, and in G. betulae asymmetric and strongly elongated, whereas the ejaculatory duct is short.In both species only mature spermatozoa have been found within the testicular follicles, i.e. the consecutive stages of spermatogenesis have not been observed in adult males. Our studies also show that the testicular follicle, vasa deferentia, accessory glands and ejaculatory duct are histologically very simple. They are composed of more-or-less flattened epithelium of a secretory type, and thin muscle fibres. The epithelial cells are rich in rough endoplasmic reticulum, mitochondria and small vacuoles. The vasa deferentia, especially in G. betulae, are filled with an electron-dense secretion which, as was shown by histochemical staining, contains proteins and polysaccharides. We suggest that the maximum secretory activity of these epithelial cells occurs, as does spermatogenesis, during larval stages, so that the short living adult males are immediately ready for copulation as in other aphids with normal-sized males.     

The male reproductive system of <Emphasis Type="Italic">Hippolyte inermis</Emphasis> Leach 1815 (Decapoda,Caridea)

The present work completes a series of studies on the biology of the shrimp Hippolyte inermis Leach 1815, where we suggested the species to be gonochoristic. The morphology of the male reproductive system (testes, vasa deferentia, gonopores) and the different stages of male germ cell development are described for the first time in the genus Hippolyte, using TEM, SEM, and histological methods. All males from 1.70 to 3.42 mm in carapace length had active testes and well-developed vasa deferentia. No case of sex reversal could be found.     

The reproductive system of Hippolyte niezabitowskii (Decapoda, Caridea)

Data on the reproductive biology of the genus Hippolyte are available from studies of Hippolyte inermis. These findings support the idea that these species are protandric hermaphrodites, exhibiting sex reversal. However, recent studies of this and other species, such as Hippolyte obliquimanus and Hippolyte williamsi, have not reported sex reversal and suggest a gonochoric condition. In the present study, histological analyses were conducted of the ovaries, testes, oviducts, vasa deferentia and the development of the male appendage. The results of this study show that the Hippolyte niezabitowskii population from southern Spain should also be viewed as a gonochoric species. The study found no evidence of sex reversals. These conclusions are also supported by information on the structure of the population and by the results of studies of the male appendage. The population structure involves different size distributions of males and of females. Size classes 2-14 exhibit substantial overlap. No evidence of sex reversal was obtained from the study of the male appendage.     

Reproduction in the Giant Isopod,Bathynomus giganteus

Summary

Aspects of the reproductive biology of the giant isopod, Bathynomus giganteus (Edwards) resemble those of other isopods. In females, the gonopores are located on the sternal midline of the eighth thoracic somite and the eggs are brooded in a marsupium. The reproductive tract of the males also resembles those of other isopods. The paired vasa deferentia open into two penes located on the sternal midline of the eighth thoracic somite. The vasa deferentia are formed of columnar epithelial cells with basal nuclei. The lumen is filled with seminal products consisting of aggregrates of spermatozoa surrounded by extracellular tubules. The sperm head consists of an acrosome and subacrosomal rod from which a pendant nucleus extends. The tails are composed of an amorphous core consisting of a dark band, two medium bands, two light bands followed by a dark band again. The tails are attached to the heads by a knob which is an extension of the core     

Morphology of the male reproductive system and spermatophore formation in the freshwater 'red claw' crayfish Cherax quadricarinatus (Von Martens, 1898) (Decapoda, Parastacidae)

The morphology of the male reproductive system was studied in Cherax quadricarinatus. The testes and vasa deferentia were dissected, fixed, cut and stained. Testes appear as two parallel and opalescent strands; they present many testicular lobes, each lobe containing cells in the same stage of the spermatogenic cycle. A vas deferens arises from the external side of each testis and three parts were clearly distinguished: proximal vas deferens (PVD), middle vas deferens (MVD) and distal vas deferens (DVD). The PVD is opalescent and highly convoluted, the MVD is pale white in colour and convoluted, but wider in diameter than the PVD, while the DVD shows the widest diameter, is straight and is white in colour. A single‐layered epithelium is recognized in the vas deferens; with cylindrical cells in the PVD and cuboid cells in the MVD and DVD. The formation of the spermatophore starts at the PVD, while the secondary layer of the spermatophore seems to be added at the MVD. At the DVD, the highly coiled spermatophore is surrounded by the periodic acid Schiff‐positive sticky components of the secondary layer. Many aspects of spermatophore formation in C. quadricarinatus differ from those of other Astacida. The applied aspects of this study for aquaculture purposes are discussed.     

Temporal shift between daily sperm movement and mating (sperm reflux) in the Asian comma butterfly,Polygonia c-aureum

Temporal changes in mating behavior and daily sperm movement were examined in adult males of the butterfly Polygonia c-aureum L. (Lepidoptera: Nymphalidae), reared under L15:D9 photoperiod at 21 °C. In this butterfly, when extra sperm is present in the duplex (storage organ) at mating, sperm reflux occurs: extra sperm are moved from the duplex to the lower and middle portions of the vasa deferentia by peristaltic movement of the lower portion of the vasa deferentia. It is known in several moth species that daily sperm movement from the testis to the upper portion of the vasa deferentia and from the upper vasa deferentia to the duplex occurs in a circadian manner. If sperm reflux and daily sperm movement occur at the same time, it could create confusion, because these sperm movements are directed oppositely. In this study, we examined the temporal changes of sperm movement and mating behavior in P. c-aureum in order to clarify whether the two sperm movements are separated in time. Our results showed that most matings occurred during the second half of the photophase, whereas daily eupyrene (nucleate) sperm movement from the upper to the middle portion of the vasa deferentia occurred immediately after light on (early photophase), indicating the presence of a time lag between mating and daily sperm movement. As sperm reflux occurs during mating, these two oppositely directed sperm movements could be performed without conflict.     

Characterization of the sexual pattern of Parastacus varicosus (Crustacea: Decapoda: Parastacidae)

Abstract. Freshwater crayfishes of the genus Parastacus are intersex, i.e., show characteristics of both sexes in the same individual; also, intersexuality has been documented in hermaphroditic species. The aim of this study was to analyze the gonads of Parastacus varicosus , characterizing its sexual pattern. The animals were collected at Cova do Touro, Gravataí, Rio Grande do Sul, Brazil. Three sexual forms were identified: intersex females, intersex males, and transitional specimens showing an ovotestes gonad that could only be identified by means of histological analysis. All specimens had two pairs of gonopores and gonoducts. The oviduct had a wider diameter in females, whereas in males the vasa deferentia were more developed. Gonads were composed of two parallel structures located in the cephalothorax. Female gonads were classified into three stages. The presence of transitional specimens may indicate that sex change occurs, with protandric hermaphroditism, as observed in other species of Parastacus . Because previous studies had demonstrated that P. varicosus is a gonochoristic species in a population from Uruguay, the present study addressed the possibility that the sexual pattern depends on differences in environmental factors among populations. To improve understanding of evolution of hermaphroditism in these crustaceans, their reproductive dynamics should be studied, including identification of the factors stimulating male and female functions.     

Ultrasonographic imaging of the testis and epididymis of the bottlenose dolphin, Tursiops truncatus aduncas

Eight male bottlenose dolphins, Tursiops truncatus aduncas, underwent examination of the reproductive organs to investigate the use of real-time B-mode ultrasonography in assessment of reproductive status and to establish normal ultrasonographic appearances. Ultrasonography allowed repeatable examinations which were well tolerated by all animals. Ultrasonography was used to examine the testes, epididymides, vasa deferentia, penis, bulbourethral and bulbocavernosal muscles; the prostate was not convincingly distinguished from surrounding muscles. Testicular echopatterns and size differed among individuals. Three distinct testicular echopatterns were discerned and could be used to differentiate males of different reproductive status. Ultrasonographic appearance of the testes provides useful data in assessing the reproductive status of male dolphins.     

Structure of the male reproductive system of Anoecia (Anoecia) corni Fabricius, 1775 (Hemiptera, Aphidoidea), a representative of the family Anoeciidae

The structure of the male reproductive system of Anoecia (Anoecia) corni Fabricius, 1775, is discussed. On the basis of histological sections and whole mount preparations, the following elements in the structure of the male reproductive system have been examined: the structure of testis and the stage of spermatogenesis; the connection of testis and vasa deferentia; the position and the histological structure of the wall of vasa deferentia; and the development of accessory glands and the ejaculatory duct as well as the structure of the external genitalia. These characters are discussed with reference to the higher classification of Aphidoidea and the taxonomic position of Anoeciidae.     

Sperm reflux and its role in multiple mating in males of a butterfly Polygonia c-aureum Linnaeus (Lepidoptera: Nymphalidae)

The relationship between sperm quantity in the duplex and that in the vasa deferentia was examined in the Asian comma butterfly, Polygonia c-aureum. In virgin males, the number of eupyrene sperm bundles in the duplex increased linearly with age, whereas that in the vasa deferentia was consistently small. However, numerous sperm were found in the vasa deferentia of males immediately after mating. The number of eupyrene sperm bundles in the vasa deferentia after mating significantly increased with age and with increasing the time interval between matings. From these and other results, it was suggested that some sperm in the duplex were moved back to the vasa deferentia during mating, and that such sperm reflux provides a means to save sperm for multiple mating.     

Onset of maturity in male southern rock lobsters Jasus edwardsii in Tasmania,Australia

Summary

The reproductive contribution of male southern rock lobsters Jasus edwardsii has recently become of interest for managing this fishery as changes to the length of seasonal closures have shifted fishing effort towards males. To assess size at onset of maturity, a total of 387 male southern rock lobsters Jasus edwardsii were collected using baited traps from four of the eight fishery regions around the Tasmanian coast during July and August 2000. Sizes at onset of maturity in these samples were estimated by examining the vasa deferentia for evidence of the commencement of spermatid production. In addition, the total combined weight of the vasa deferentia and testis was compared with body size (as a gonad somatic index, GSI). Estimates of size at onset of maturity from the two methods were similar, although estimates from GSI appeared to have broader confidence limits. Although these physiological indices of maturity do not necessarily translate to functional maturity, they indicate that maturity is well below that of the legal minimum size of 110 mm carapace length used for managing the fishery (all estimates by either method for length at 50% sample maturity ≤70 mm carapace length). Production of sperm by males occurs below the size at onset of maturity of females from the same region and spatial patterns in maturity estimated by onset of spermatid production were similar to those of females.     

Abdominally entrained periodicities of testis and vas deferens activity in the Mediterranean flour moth

In a light-dark (LD) regimen, sperm, first apyrene and then eupyrene, start moving out of the fused testes of the Mediterranean flour moth, Anagasta kuehniella, toward the beginning of the scotophase. At 27° ± 2°C, the sperm mass remains in the proximal part of the vasa deferentia for 10 to 12 hr and then passes rapidly into the seminal vesicles, remains in these organs for about 5 hr, and is then transported to the ductus ejaculatoris duplex where it becomes available for ejaculation. The phases of sperm movement appear to be closely related to sperm development, and the reproductive activity of the moths. In isolated abdomens there is a significant reduction in the amount of sperm released from the testes, but normal periodicity of sperm release and movement continues in either LD or continuous dark (DD) regimens, and rapid phase shifting occurs when a LD regimen is reversed. All stages of sperm movement are disrupted in continuous light (LL), but normal periodicity is usually resumed when isolated abdomens of the LL moths are placed in LD or DD regimens. Normal periodicity also occurs in moths paralyzed with tetrodotoxin or procaine. Removal of any one of the four abdominal ganglia from LL moths does not prevent increased sperm release when the moths are placed in LD, though with each ganglion there is some disruption of the normal pattern of movement down the vasa deferentia. It is thought that the testes and vasa deferentia down to at least the seminal vesicles represent a semiautonomous complex in which periodicity is maintained by endogenous circadian activity in cells of the testes (and possibly the vasa deferentia) or more probably in a peripheral control center.     

FUNCTIONAL REDUCTION OF THE SOUTHERN MINKE WHALE (BALAENOPTERA ACUTOROSTRATA) TESTIS DURING THE FEEDING SEASON

Seasonal variation in reproductive activity in the male southern minke whales was investigated. The animals were killed and collected during the feeding season (December-March) in the Antarctic Ocean in the eastern part of Area III (35°E-70°E, south of 60°S) and Area IV (70°E-130°E, south of 60°S). Blood samples, testes, epididymides, and vasa deferentia were collected from 62 males, which had testes weighing over 400 g each. Changes in testicular morphology and plasma testosterone, estradiol-17β and LH concentrations measured by enzyme immunoassay were investigated. Reduction of testicular function associated with different capture periods was found in the summer season. From December to March, body length and body weight remained steady, but decreases in testicular weight, epididymal weight, and testicular volume were found in February. During the same period, plasma testosterone concentration also declined. A significant decrease in the number of germ cells continued during the period of feeding season. An increase in area of seminiferous tubule tended to proceed in a number of germ cells. These changes reflected the percentage of spermatozoa in the vasa deferentia ; in particular, motile spermatozoa were observed in December. Based on morphological observation, spermatogenesis had also declined. These results indicate regulation of testicular function by testosterone, as in terrestrial mammals. A gradual decrease of testicular function occurred during December-January.     

Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.     

The SW Atlantic burrowing crab Chasmagnathus granulatus Dana affects the distribution and survival of the fiddler crab Uca uruguayensis Nobili

In this paper, we address the question of whether the presence of the burrowing crab Chasmagnathus granulatus affects the habitat use of the fiddler crab Uca uruguayensis. Field samples showed that the species have a disjoint spatial distribution. Male fiddler crab density decreased in zones with C. granulatus, however, female density increased. Male fiddler crabs avoided feeding on sediment affected by C. granulatus and were more preyed. Predation was higher during the fiddler crab reproductive season and, probably due to predation risk, males showed lower reproductive display in shared zones. Field experiments shows that when C. granulatus were excluded, densities of U. uruguayensis increased mainly due to an increase in density of males. Habitat differentiation of these species may be because C. granulatus affects U. uruguayensis in several ways, including direct predation, disturbance and behavioural changes associated to predation risk. Males and females are affected differentially probably because of the extreme sexual dimorphism of this crab species. Coloration on enlarged claw and waving activities are all factors that increase predation risk for male and the presence of only one feeding claw may increase sediment-mediated effects.     

A new and aberrant species of Dugesia (Platyhelminthes,Tricladida, Dugesiidae) from Madagascar

In this paper we report a new species of Dugesia of the family Dugesiidae from Madagascar, representing the fourth species of freshwater planarian known from this global biodiversity hotspot. In some respects the new species is aberrant, when compared with its congeners, being characterized by a head with smoothly rounded auricles, a peculiar course of the oviducts, including the presence of a common posterior extension, and by the asymmetrical openings of the vasa deferentia at about halfway along the seminal vesicle. Further, it is characterized by a ventral course of the ejaculatory duct with a terminal opening, very long spermiducal vesicles and unstalked cocoons. Its diploid chromosome complement with 18 chromosomes represents an uncommon feature among fissiparous species of Dugesia.     

Morphology of the male reproductive system of freshwater prawn Macrobrachium carcinus (Decapoda,Caridea): Functional and comparative aspects

Testes and vasa deferentia are parts of the male reproductive system of decapod crustaceans. Both organs show morphological differences among decapod species in terms of anatomical and histological patterns reflecting the diversity of this group. Describing these features may assist in systematics, phylogenetics, and studies of reproductive behavior, especially for species of commercial interest, such as Macrobrachium carcinus, a native American species that, unusually for this genus, has no precopulation courting behavior. This study aims to describe the reproductive morphology and spermatogenesis of the male freshwater prawn M. carcinus. The male reproductive system of this species consisted of lobed testes connected to the vasa deferentia. The testis of M. carcinus was divided into several lobules. Each lobule was formed by a cluster of germ cells surrounded by connective tissue and nurse cells. This microscopic anatomy and histology of the testicular histoarchitecture has been described for many species of Decapoda and may represent a derived design of the testes. Unlike that in other decapod species, spermatogenesis proceeds in short transitory phases that produce spermatozoa at high concentrations and frequencies, corroborating the uncommon male reproductive behavior of this species. In the spermatic pathway, the lobules develop and fuse before releasing spermatozoa from the testes; however, this process has not been observed in decapods, yet. The neutral compounds secreted by the vas deferens are important for sperm nutrition as females secrete a substance for spermatophore adhesion during reproduction. This study presents different features and dynamics of the spermatogenic process in the male reproductive system of M. carcinus that have not yet been presented in the literature for decapods.     

New insights in the male anatomy,spermatophore formation,and sperm structure in Atyidae: The red cherry shrimp Neocaridina davidi

This study aims to analyze the functional anatomy of the male reproductive system in Neocaridina davidi, a very popular ornamental species of caridean shrimp. Mature males were cold‐anaesthetized and their reproductive systems were dissected for histological and histochemical analysis, while the spermatozoa and spermatophore wall ultrastructure were analyzed under transmission electron microscopy. The male reproductive system consisted of two coiled testes, which were continuous with the vasa deferentia. Testes were positioned on the dorsal side of the cephalothorax above the hepatopancreas, and comprised seminiferous tubules where spermatogenesis occurred. Each vas deferens (VD) was a long tube dorsolaterally positioned with respect to the hepatopancreas, and increased in diameter at the distal end. Three regions could be recognized in the VD: proximal, middle, and distal. The proximal region had a cylindrical epithelium with secretory cells. The middle region (or typhlosole) had a dorsal fold (or typhlosole) with a thick columnar epithelium and high secretory activity. The spermatophore was a continuous cord with three acellular layers, which were mainly characterized by the presence of neutral glycoconjugates and proteins. The sperm morphology was distinct from the inverted cup‐shaped spermatozoa observed in the majority of caridean shrimps. The spermatozoa in specimens of N. davidi were spherical in shape, with a cross‐striated, single, short spike, and arranged in clusters of three or four sperm cells. The composition of the spermatophore, and the arrangement and form of the spermatozoa, seem to be unique in comparison to other species of Caridea.