Ultrastructure and histochemistry of the male reproductive system of the genus Callinectes Stimpson, 1860 (Brachyura: Portunidae)

We described the ultrastructure and histochemistry of the reproductive system of five Callinectes species, and evaluate the seasonal variation in weight of the reproductive system and hepatopancreas by comparing annual changes of somatic indices. The somatic indices changed little throughout the year. In Callinectes, spermatogenesis occurs inside the lobular testes and, within each lobule, the cells are at the same developmental stage. Spermatogenesis and spermiogenesis follow the same development pattern in all Callinectes studied. Mature spermatozoa are released into the seminiferous ducts through the collecting ducts. Cells of the vas deferens are secretory as evidenced by rough endoplasmic reticulum, Golgi complex, and secretory vesicles that produce the seminal fluid. The anterior vas deferens shows two portions: proximal and distal. In proximal portion (AVDp), spermatozoa are clustered and embedded in an electron-dense, basophilic glycoproteinaceous secretion Type I. In the distal portion (AVDd), the spermatophore wall is formed by incorporation of a less electron-dense glycoproteinaceous secretion Type II. The secretion Type I change to an acid polysaccharide-rich matrix that separates the spermatophores from each other. The median vas deferens (MVD) stores the spermatophores and produces the granular glycoproteinaceous seminal fluid. The posterior vas deferens (PVD) has few spermatophores. Its epithelium has many mitochondria and the PVD seminal fluid changes into a liquid and homogeneous glycoprotein. Many outpocketings in the PVD and MVD help to increase the fluid production. Overall, the reproductive pattern of Callinectes is similar to other species that produce sperm plugs. The secretions of AVD, MVD, and PVD are responsible for the polymerization that forms the solid, waxy plug in the seminal receptacle. The traits identified here are common to all Portunidae species studied so far.     

Biochemistry of seminal secretions of the crab Scylla serrata with reference to sperm metabolism and storage in the female.

Biochemical studies on the male reproductive tissues and seminal secretions have been made with reference to sperm metabolism and different stages of maturity in the crab Scylla serrata. The results reveal that the seminal plasma and spermatophores are rich in protein, carbohydrate, and lipid. In general, organic components of spermatophores are considerably higher than those of seminal plasma. Enzyme studies show that the succinate dehydrogenase (SDH) activity is very low, whereas fumarate reductase (FR) and lactate dehydrogenase (LDH) exhibit high activity. Electrophoretic studies on LDH show that, in addition to the occurrence of a sperm-specific fraction, LDHx, the M-type subunits are predominant in the mature spermatophores. These results from enzyme studies suggest that sperm metabolism is mainly anaerobic, utilizing the carbohydrates as substrates. The results for maturational changes reveal that the male reproductive tissues and their secretions contain lesser quantity of organic components in the immature crabs; as the maturity proceeds, there is not only concentration of organic substances but also an increase in the size of spermatophores. The concentration of biochemical constituents is highest in the proximal vas deferens (PVD), suggesting that the granular seminal plasma as well as the sperm-agglutinating substance and spermatophoric wall are secreted in this region. The spermatheca of the unmated female crabs are poor in organic constituents. After mating, their contents are enriched by organic substances derived from contributions of the seminal substances. During sperm storage in the spermatheca, only the carbohydrates decline steeply. A low activity of SDH, but a moderate level of LDH and a high level of FR activity, is recorded in the spermathecal content of mated crabs, providing further evidence for anaerobic metabolism of sperm during storage in female. A sharp fall in the stored carbohydrates constitutes further evidence in this regard.     

Courtship and sperm transfer in Charinus neocaledonicus Kraepelin, 1895 and Charinus australianus (L. Koch, 1867) (Arachnida, Amblypygi, Charinidae)

The Charinus australianus group is a well-defined species group characterised by rounded, cushion-like female gonopods. Before the present study, the morphology of the gonopods and their function have not been understood. This paper describes courtship behaviour, spermatophore morphology, and the morphology of the female genitalia of Charinus neocaledonicus Kraepelin, 1895 and C. australianus (L. Koch, 1867). Courtship behaviour, though different in details, is similar to that of many other species. The spermatophores are large and soft and carry very small sperm packages, each with a short stalk. After sperm transfer, the spermatophore may be eaten by the female. The spermatophore thus transfers not only spermatozoa but also nutritious paternal investment to the female. Each female gonopod is equipped with a seminal receptacle consisting of an atrium and a spacious inner receptacle. The cover of the atrium can be elevated by high blood pressure and pulled back by a group of muscles attached to the inner part of the receptacle. The female probably picks up the sperm packages with the atria of her receptacles. The observations are compared to those on other amblypygids, and the evolution of different types of spermatophores and of gonopods with seminal receptacles is discussed.     

The Vas Deferens of the Spanish Lobster,Scyllarus chacei

Summary

The male reproductive tract of Scyllarus chacei consists of paired testes and vasa deferentia that conduct sperm containing spermatophores to the genital pores at the base of each fifth walking leg. The testis is joined to the vas deferens which can be divided into four regions: (1) the anterior vas deferens can be further divided into three regions. It is highly convoluted and is the region in which the sperm become encapsulated in ovoid spermatophores of approximately 100 sperm as well as produces seminal fluids. (2) The middle vas deferens is the primary site of sperm storage and adds to seminal fluids which formed in the anterior region. (3) The posterior region is highly muscularized and may serve for limited sperm storage. (4) The most distal portion is the ejaculatory duct which is highly muscularized for extruding the spermatophoric mass for transfer to the female. A final seminar product is added here.     

Morphological analysis of the female reproductive system of Stenorhynchus seticornis (Brachyura: Inachoididae) and comparisons with other Majoidea

We examined the female reproductive system of the yellowline arrow crab Stenorhynchus seticornis by means of histological and histochemical techniques. Mature specimens obtained in the field were kept in the laboratory for mating experiments. After 24 h, newly mated females were dissected, and their reproductive trait routinely processed for embedding in historesin. The specimens examined each possessed a pair of kidney‐shaped seminal receptacles (SR), and these we classified as ventral type, based on the location of the oviduct opening. The mesodermal dorsal region (DR) of SR consisted of a stratified epithelium with scaly cells, while the ectodermal ventral region (VR) was composed of a simple epithelium covered by a cuticle. The oviduct opened at the transition region (TR) between DR and VR and had no velum. The simple epithelium of TR had more folds on the face of the oviduct opening. The vagina exhibited the same features as the TR epithelium and was contiguous to VR, anchored by muscles. In the lumen, from one to three strata of sperm packets were observed, the dorsal one containing free sperm, and the most ventral stratum, spermatophores. An acidophilic glycoprotein layer enclosed the strata. Spermatophores in the ventral stratum were enclosed in a voluminous secretion, composed by acid polysaccharides most likely from the last male mated. The ventral‐type receptacle, stratified sperm packets, and polyandry, usually observed in females of Majoidea, suggest the occurrence of sperm competition in S. seticornis, favoring the sperm of the last male mated, as its sperm mass is located near the opening of the female oviduct.     

Morphology and function of the reproductive tract of the spider crab Libinia spinosa (Crustacea, Brachyura, Majoidea): pattern of sperm storage

Morphology and function of the male reproductive tract, female spermatheca and patterns of sperm storage were assessed in the crab Libinia spinosa using histological methods. Testes are characterized by the presence of peripheral spermatogonia and different sequences of sperm maturity. Spermatophores begin to be packed in the last portion. The vas deferens consists of three sections: anterior, with undeveloped spermatophores and free sperm; median, with well-developed spermatophores; and posterior with granular secretions. Female spermathecae are of the ventral type, with a velum separating dorsal and ventral chambers. Live individuals were kept in the laboratory and arranged in pairs. An experiment was conducted toward the end of the reproductive season, in which males with the right gonopod excised were placed with receptive females. After mating, females were killed and the spermathecae dissected for histological study and observation of the pattern of sperm storage. Spermatozoa were found forming discrete sperm packages. New ejaculates can fill the entire spermatheca or be restricted to the ventral chamber; sperm are rounded, with a distinguishable acrosomal core. Old ejaculates are restricted to the dorsal chamber and are of irregular shape and larger size; an acrosomal core was not distinguishable. The secretions produced by the glandular epithelium of the dorsal chamber of the spermathecae are likely to have a role in the removal of dead sperm.     

Receptivity of female Neohelice granulata (Brachyura, Varunidae): different strategies to maximize their reproductive success in contrasting habitats

The extent of the receptive period may determine the mating strategies employed by female crabs to obtain mates. Here, we studied the receptivity of female Neohelice granulata (Dana, 1851) in the laboratory, including the form of the vulvae and the anatomy of the seminal receptacle (SR). We examined the factors that influence the duration of receptivity by comparing two populations inhabiting contrasting habitats: Mar Chiquita Coastal lagoon (MCL), which is an oligo-polyhaline estuary, and San Antonio Oeste (SAO), which is an eu-hyperhaline marine bay. Non-receptive females have immobile vulva opercula, while receptive females have mobile opercula. Histological sections of the SR showed that the degree of epithelium secretions was associated with the receptive stage of females, and they may be involved in the maintenance of viable sperm and in the dehiscence of spermatophores. The existence of a special tissue at the junction of the oviduct and the SR was described and proposed as an internal mechanism influencing the timing of ovulation. The duration of receptivity was dependent on the SR load and the capacity to lay eggs. Thus, females with empty SR exhibited longer receptivity and did not lay eggs, while those with full SR exhibited shorter receptivity and always laid eggs. Interpopulation differences showed that females from SAO had shorter receptivity and heavier SR and laid eggs more frequently than females from MCL. Based on our results, we suggest that N. granulata females can adjust the duration of their receptivity and control the moment of fertilization according to different internal mechanisms related to the morphology of the vulvae, the fullness of the SR and anatomical attributes of the SR. An important consequence of this control is greater sperm competition. The extent of the receptive period and the number of times that a female could become receptive in a single reproductive season may also depend on the habitat characteristics.     

Ejaculate esterase 6 and initial sperm use by female Drosophila melanogaster

The period of initial sperm storage and use by Drosophila melanogaster females is examined for effects of the seminal fluid enzyme esterase 6. Females mated to males differing in their level of esterase 6 activity were dissected from 5 min to 50 hr after the start of copulation and numbers of sperm contained in the uterus, ventral receptacle and paired spermathecae were counted. Of the 4000–6000 sperm transferred at copulation, about 700 are stored in the receptacle by 4 hr post mating and 400 in the spermathecae by 7 hr. However, sperm are released rapidly from storage organs following these peaks and may be found again in the uterus in numbers up to 100 or more. The rate of sperm release is closely related to the level of esterase 6 activity, suggesting that this seminal fluid enzyme is involved in sperm motility.     

日本沼虾雄性生殖系统的研究：Ⅱ.精子的形态及超微结构

运用电镜和细胞化学技术研究了日本沼虾精子的形态结构,结果表明：日本沼虾精子属无鞭毛精子,为单一棘突型,呈图钉样,由主体和棘突构成;主体部分为帽状体,精核和细胞质带。帽状体由约２０根辐射状纤丝组成,纤丝上具横纹,并汇合帽状基部,由此向后延伸形成棘突。     

Female reproductive morphology of coral‐inhabiting gall crabs (Crustacea: Decapoda: Brachyura: Cryptochiridae)

Gall crabs are obligate associates of stony corals in which they induce skeletal modifications. In some cryptochirid species, females live in open depressions accessible to males; while in others, females are rather isolated in semiclosed galls, which necessitates elaborate sperm storage capabilities by the female. In this study we investigate the female gross morphology and reproductive systems of Fungicola syzygia lodged in semiclosed flattened pits, Opecarcinus cathyae with semiopen pits and Pseudocryptochirus viridis from shallow open depressions using line drawings and histological methods. The general morphology of the cryptochirids' reproductive systems is uniform and conforms to other thoracotreme brachyurans: paired muscular vaginae of the concave pattern lead from the sternal gonopores into paired seminal receptacles where sperm is stored. The seminal receptacle is internally lined by distinct types of epithelia: a cuticle underlined by a columnar epithelium ventrally, a monolayered secretory epithelium dorsally and a multilayered transfer tissue where the oviducts enter the seminal receptacle. In all studied specimens, the seminal receptacle contained free spermatozoa; however, in specimens of Pseudocryptochirus viridis it also contained spermatophores, indicating a recent insemination. In contrast to most other brachyurans ovaries of the investigated cryptochirids extend into the pleon. The specific degree of ovary extension differs between the studied species and is closely related to female body shape.     

Switchover to the mated state by spermathecal activation in female Anopheles gambiae mosquitoes

Both Aedes aegypti and Anopheles gambiae mosquitoes undergo physiological and behavioral changes after the females mate, but unlike Ae. aegypti, the mated state in An. gambiae is not attained through the action of male accessory gland substances. Experiments in which the spermathecae of mated females were manipulated suggest that a spermatheca filled with sperm is responsible for triggering oviposition behavior. An estimated 48% of the previously mated An. gambiae females mated again when the interval between encounters with males was less than 24h. Unlike male Ae. aegypti that can inseminate up to seven females after their testes are removed, An. gambiae do not store sperm in the vas deferens and without testes would be unable to inseminate any females.     

Somatic and gametic resources in male rock shrimp, Rhynchocinetes typus: effect of mating potential and ontogenetic male stage

Investment in somatic and gametic resources may vary during the ontogeny of an organism. In the rock shrimp, Rhynchocinetes typus, males pass through several stages during ontogeny, and a dominance order reflects this developmental order (typus<intermedius<robustus). During mating in a competitive environment, subordinate males use a sneaking tactic characterized by rapid placement of many spermatophores, but dominant males transfer few spermatophores during matings. We therefore hypothesized that males in the different ontogenetic stages (1) invest differently in somatic and gametic growth and (2) differ in their ability to engage in multiple matings. The relative weight of the hepatopancreas (adjusted for total body weight), an organ related to somatic growth, was significantly lower in robustus males than in all other ontogenetic stages examined. The relative weight of the vas deferens (Vd), a measure of sperm reserves, was significantly higher in robustus males than in males in the other stages. In typus males that had mated once, the total weight of Vd was significantly lower than in unmated typus males, but no such difference was found in robustus males. All robustus males mated successfully with five females during 5 consecutive days, but many typus males failed to mate after the second or third day. Typus males that mated successfully with females placed significantly more spermatophores than did robustus males during the first mating but not in subsequent matings. The results suggest that robustus males, in contrast to typus males, can invest more in sperm production and due to their ability to defend a female, can use spermatic resources economically allowing them to mate with subsequent females. We conclude that, during ontogeny, R. typus males invest simultaneously in somatic and gametic growth in accordance with their mating behaviour and chance to mate. In this and other crustacean species, male resource investment during ontogeny thus may depend on their probabilities at different ontogenetic stages for obtaining mating opportunities. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

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.     

The vas deferens of the spider crab,Libinia emarginata

Sperm enter the anterior vas deferens individually in the spider crab male. There they become surrounded by secretion products from the cells of the vas deferens, and are compartmentalized into spermatophores of varying size. The anterior vas deferens can be divided into three regions. The epithelium of the anterior vas deferens varies regionally from low to high columnar. The cytoplasm contains vast arrays of rough endoplasmic reticulum and Golgi complexes but few mitochondria. Intercellular spaces contain septate junctions, gap junctions and vesicles. Once the spermatophores have been formed in the anterior vas deferens, they are moved posteriorly to the middle vas deferens where they are stored and surrounded by seminal fluids. The epithelial cells of the middle vas deferens contain large amounts of rough endoplasmic reticulum and Golgi complexes. Numerous micropinocytotic vesicles appear, forming at the cell surface and within the apical cytoplasm. Their suggested function is the resorption of secretion products of the anterior vas deferens which initiated compartmentalization of the spermatozoa into spermatophores. The posterior vas deferens functions primarily as a storage center for spermatophores until they are released at the time of copulation. Seminal fluid surrounding the spermatophores is produced in this region as well as in the middle vas deferens. The cells of this region contain vast arrays of vesicular rough endoplasmic reticulum and Golgi complexes. The cells are multinucleate. Microtubules are numerous throughout the length of the cells and appear to insert on the plasma membrane.     

Influence of developmental environment on male- and female-mediated sperm precedence in Drosophila melanogaster

Length of the sperm flagellum and of the female's primary sperm-storage organ, the seminal receptacle (SR), exhibit a pattern of rapid correlated evolution in Drosophila and other lineages. Experimental evolution studies with Drosophila melanogaster indicate that these traits have coevolved through sexual selection, with length of the SR representing the proximal basis of female sire discrimination, biasing paternity according to sperm length. Here, we examine the impact of experimentally varying the developmental environment, including larval density and larval and adult nutrition, on sperm length, SR length and on the pattern of sperm precedence. Expression of SR length was far more sensitive to variation among developmental environments than was sperm length. Nevertheless, there was striking co-variation in sperm and SR length. The developmental environment of both females and second males, but not first males, significantly contributed to variation in male competitive fertilization success.     

Male internal reproductive structures of european pea crabs (Crustacea,Decapoda, Brachyura,Pinnotheridae): Vas deferens morphology and spermatozoal ultrastructure

Pea crabs of the subfamily Pinnotherinae (Pinnotheridae) have a high investment in reproduction and an outstanding reproductive output, probably as an adaptation to the required increase in reproductive rate due to the pinnotherids small size and their parasitic, host‐dependant way of life. In the present study, we investigate the male internal reproductive structures and the ultrastructure of spermatozoa of Pinnotheres pisum and Nepinnotheres pinnotheres by histological methods and both scanning‐ and transmission electron microscopy. In the Brachyura, the male internal reproductive systems generally consist of paired testes and corresponding vasa deferentia where spermatozoa develop and mature. Spermatozoal ultrastructure of the investigated pinnotherids conforms to the thoracotreme type, however, N. pinnotheres has an accessory opercular ring and a periopercular rim, neither of which are present in spermatozoa of P. pisum. Spermatozoa are enclosed within spermatophores in the secretory proximal vas deferens. Two types of secretions were observed in P. pisum and N. pinnotheres: an electron dense substance secreted in the proximal vas deferens involved in spermatophore formation, and large electron‐luscent vesicles constituting the seminal plasma in the medial and distal vas deferens. The medial vas deferens is strongly widened compared to other brachyurans to purpose storing spermatophores embedded in seminal plasma. Tubular appendices, which produce and store large amounts of seminal plasma, arise from the distal region of the vas deferens. The appendices extend into the ventral cephalothorax and also in the first pleomere. The latter being an exceptional location for reproductive structures among male brachyurans. J. Morphol. 274:1312–1322, 2013. © 2013 Wiley Periodicals, Inc.     

Spermatophore formation and sperm ultrastructure of Sundathelphusa philippina (Crustacea: Brachyura: Gecarcinucidae)

We investigated the morphology of spermatozoa, spermatophores and the anterior vas deferens (AVD) of the gecarcinucid freshwater crab Sundathelphusa philippina. The morphology of the acrosome (proportions, structure and arrangement of acrosomal layers) and the spermatophores complies with the known sperm and spermatophore morphology of the brachyuran family Gecarcinucidae. The sperm cells are packed within coenospermic spermatophores that are of a mucous type, lacking a complex spermatophore wall. Spermatophore formation takes place in the distal part of the AVD. The strongly proliferated inner epithelium of the vas deferens releases vesicles via apocrine secretion. These vesicles fuse with the incipient spermatophores that subsequently coalesce, thus forming the coenospermic aggregates that represent the mature spermatophores.     

Ultrastructure and function of the seminal vesicle of Bittacidae (Insecta: Mecoptera)

The fine structure of the seminal vesicle and reproductive accessory glands was investigated in Bittacidae of Mecoptera using light and transmission electron microscopy. The male reproductive system of Bittacidae mainly consists of a pair of testes, a pair of vasa deferentia, and an ejaculatory sac. The vas deferens is greatly expanded for its middle and medio-posterior parts to form a well-developed seminal vesicle. The seminal vesicle is composed of layers of developed muscles and a mono-layered epithelium surrounding the small central lumen. The epithelium is rich in rough endoplasmic reticulum and mitochondria, and secretes vesicles and granules into the central lumen by merocrine mechanisms. A pair of elongate mesodermal accessory glands opens into the lateral side of the seminal vesicles. The accessory glands are similar to the seminal vesicle in structure, also consisting of layers of muscle fibres and a mono-layered elongated epithelium, the cells of which contain numerous cisterns of rough endoplasmic reticulum and mitochondria, and a few Golgi complexes. The epithelial cells of accessory glands extrude secretions via apocrine and merocrine processes. The seminal vesicles mainly serve the function of secretion rather than temporarily storing spermatozoa. The sperm instead are temporarily stored in the epididymis, the greatly coiled distal portion of the vas deferens.     

Functional morphology of the male reproductive system in Callichirus major (Crustacea: Decapoda: Axiidea): Evidence of oocytes in the gonad

Callichirus major inhabits the intertidal region of marine ecosystems and it is frequently used as live bait for fishing. This study aimed to describe the functional anatomy of the male reproductive system by microscopic techniques. The animals were collected along the Corujão beach, Piuma—ES, Brazil, and, in laboratory, the males were classified into two phases: immature (IM) and developed (DE) based on the macroscopic characteristics of the gonads. The gonad and vas deferens were dissected for histological routine and histochemical tests. Histologically, it was noted that in both phases, the more distal region of gonads has ovarian characteristics, showing developing oocytes. Also, different male germ cells were identified: spermatogonium (SPG), spermatocytes I and II (SPTCI, SPTCII), initial and final spermatid (IS, FS) and sperm (SPZ). Accessory cells with spherical or pyramidal nuclei were also present inside the testicular lobules. According to the vas deferens structure, three regions can be characterized: proximal (PVD), middle (MVD) and distal (DVD). In the lumen of the vas deferens, a spermatophoric matrix highly reactive for histochemical tests was observed. The presence of female germ cells in males suggests the occurrence of intersexuality or hermaphroditism in this species.