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.     

Evolution of sperm morphology in potamid freshwater crabs (Crustacea: Brachyura: Potamoidea)

We investigated sperm cells and spermatophores of four species of Old World freshwater crabs belonging to three different genera of the subfamily Potaminae (family Potamidae). Characters previously believed to be apomorphic for the potamid subfamily Potamiscinae were also found to occur in the Potaminae. To infer the morphological ancestral character state combination of the Potamidae, ancestral character state analysis of four different sperm traits was performed, based on a 16S rDNA phylogeny of the investigated species. Comparing molecular phylogeny and character state distribution, several cases of convergent evolution could be identified. The densely packed, coenospermic spermatophores and the occurrence of a ‘tongue‐and‐groove’ connection between operculum and acrosomal zones are probably apomorphies for the whole Potamidae. The spermatozoa of Socotrapotamon socotrense show several unique characters. We also analysed the evolution of acrosome size. The sperm cells of the Potamidae and their sister‐group Gecarcinucidae only slightly overlap in acrosome size. Within the investigated species, the ‘East Asia’ subclade (subfamily Potamiscinae) developed significantly larger acrosomes than the subfamily Potaminae. Our results suggest that the use of brachyuran acrosome morphology for phylogenetic inference at the family level is strongly affected by small sample size, and by convergent character evolution. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010.     

Morphology and ultrastructure of the adult ovarian cycle in Mithracidae (Crustacea,Decapoda, Brachyura,Majoidea)

The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.     

Comparative spermatozoal ultrastructure and molecular analysis in dromiid crabs and their phylogenetic implications for Dromiidae and Podotremata (Decapoda: Brachyura)

We described the spermatozoal ultrastructure and conducted a molecular analysis of Dromiidae Hypoconcha parasitica, Hypoconcha arcuata, Moreiradromia antillensis and Dromia erythropus. To elucidate the relationship between the different species of this brachyuran group, we also compared the spermatozoal morphologies and phylogenetic positioning among species of Dromiidae, Dromioidea and Podotremata. Specimens were collected from the northern coast of São Paulo, Brazil and were fixed and processed followed by transmission electron microscopy and molecular analysis routines. The Dromiidae spermatozoa studied are characterized by a discoidal acrosome, with three or four concentric zones, which are centrally separated by a bilaterally capitate perforatorial chamber, with a “mushroom”-shaped apex in the Hypoconchinae and a “T-shape” in Dromiinae. Above the perforatorial chamber, there is an apical protuberance, continuous with the subopercular region and the operculum, which forms a low, centrally perforated dome. Under differential interference contrast microscopy, the spermatozoa show 3 to 4 radial arms. The spermatozoal characters in Hypoconchinae and Dromiinae do not separate these subfamilies from the Dromiidae and Dromioidea. Ultrastructural differentiation was only found between representative Dromioidea and other Podotremata. Thus, the spermiotaxonomy of these Hypoconcha, Moreiradromia and Dromia species corroborated previous morphological and molecular studies, supporting the monophyly of Dromiidae and Dynomenidae in relation to Homolidae and Latreilliidae.     

The ultrastructure of the spermatozoon of Lernaeocera branchialis (Copepoda : Pennellidae)

Spermatozoa are produced by males of the fish-parasitic copepod, Lernaeocera branchialis, on the flounder (Platichthys flesus) host and packaged into spermatophores. Mature spermatozoa from spermatophores have been investigated with light microscopy and t.e.m. and s.e.m. techniques. Each is a filiform cell up to 30 µm long and 1 µm in diameter, being symmetrically tapered at each end to produce a javelin-shaped configuration. Surface s.e.m. appearances suggest that the cell is helically twisted. The spermatozoon possesses no flagellum, no nuclear envelope, no mitochondria and no orthodox acrosome. For most of its length the cell has a four-lobed appearance in transverse section and contains little more than a cylindrical sleeve of pseudomembranous material with which is associated finely filamentous or granular material which is assumed to be nuclear chromatin. The spermatozoon is immobile in seawater.The ultrastructure of L. branchialis spermatozoa has been compared with that of eight other copepod species.     

Comparative ultrastructure of the spermatozoa of the Majoidea (Crustacea,Decapoda, Brachyura) with new data on six species in five genera

Comparative ultrastructure of majoid spermatozoa belonging to 23 species, in 19 genera and five families, is considered, with new data on Schizophrys aspera; S. rufescens (Majidae, Majinae); Camposcia retusa (Inachidae); Pyromaia tuberculata (Inachoididae); and Huenia heraldica and Menaethius monoceros (Epialtidae, Epialtinae). The oregoniid Chionoecetes opilio, and inachids Cyrtomaia furici, Platymaia rebierei, Macropodia longirostris and Inachus phalangium, possibly with Camposcia retusa, but not Podochela riisei, appear to form a group. Within the inachids, Macropodia and Inachus are especially close. A domed central acrosome zone, seen in most inachid sperm, in majines (both Schizophrys species), in pisines (Oxypleurodon orbiculatus and O. stuckiae) and epialtines (Huenia heraldica and Menaethius monoceros), appears to be an autapomorphy of these majoids. A peripheral acrosome zone is seen in the inachid Grypacheus hyalinus, two inachoidids (P. tuberculata and Stenorhynchus seticornis) and the majid Maja squinado. Pyromaia tuberculata differs from other inachoidids in having a slightly dome‐shaped operculum. The mithracine Macrocoeloma trispinosum (Majidae) sperm more closely resembles Inachoididae, than Inachidae. Spermatologically, the family Majidae and the subfamily Majinae are not homogeneous. Spermatozoal ultrastructure does not support a majoid–hymenosomatid relationship and is equivocal with regard to the placement of Cryptochiridae in either the Thoracotremata or Heterotremata, the prominent operculum strongly differentiates cryptochirids from Majoidea.     

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.     

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.     

Spermiogenesis and sperm structure in the crabUca tangeri (Crustacea,Brachyura), with special reference to the acrosome differentiation

Summary Early spermatids of the crabUca tangeri consists of the nucleus of granular chromatin and the cytoplasm, which contains a proacrosomal vesicle in close association with membrane lamellae. In the mid spermatids an invagination of the acrosomal vesicle membrane gives rise to the formation of the perforatorium, a spindle-shaped tubule which encloses tubular membranous structures. The pair of centrioles located at the base of the acrosome is not directly involved in perforatorial differentiation. The acrosomal vesicle shows a heterogeneous content composed of the operculum, the thickened ring, and three layers of different materials concentrically arranged around the perforatorium. During the late spermatid stage the nuclear profile differentiates numerous slender arms and the chromatin arranges into fibers. Membranous tubules from the cytoplasm become incorporated into the tubular structures of the perforatorium. The mature spermatozoon has the typical structure of the branchyuran sperm, with a complex acrosome, cupped by the nucleus, and a thin cytoplasmic band intervening between the former main elements. The centrioles are degenerate. The nuclear arms are unusually numerous (more than 20) and lack microtubules or microtubular derivatives.     

The ultrastructure of the nauplius eye ofSapphirina (Crustacea: Copepoda)

Summary The ultrastructure of the specialized nauplius eye of three species of the copepod genusSapphirina was investigated. The gross morphology described earlier (Elofsson, 1966a) was confirmed. The ventral cup is covered by a red pigment and the lateral cups by a red and a black pigment. The ultrastructural configuration of the pigment granules was found to differ in the two kinds of pigment cells. The black pigment cell, moreover, contains a large number of transversely banded fibrils and is able to produce reflecting crystals. The pigment granules of the black pigment cell show a variation in electron density. An intimate connexion exists between the black pigment cell and large retinula cells in the lateral cups, indicating an exchange of material. The tapetal cells present in all three cups form crystal platelets contained in two sets of membranes. It is suggested that the ventral cup and part of the lateral cups function as thePecten-eye (Land, 1965). The rhabdomeres of the retinula cells are composed of microvilli measuring 400 Å. The orientation of these seems to exclude polarotactic behaviour. The ventral cup and the four small cells of the lateral cups contain some retinula cells with microvilli arranged parallel to the incoming light. The retinula cells further develop an intricate system of membrane-invaginations penetrating deep into the cell and associated with numerous mitochondria. Retinula cells of the ventral cup and part of the lateral cups contain clear portions filled with granular material only. Retinula and other cells contain attenuated mitochondria with parallel tubuli. The proximal lens in front of each lateral cup consists of one cell. A development from the conjunctival cells is suggested. The results are evaluated in terms of function and evolution.This work has been supported by a grant from the Swedish Natural Science Research Council (2760-2).     

Molecular systematics of the Asian mitten crabs,genus Eriocheir (Crustacea: Brachyura)

To help resolve phylogenetic relationships among the mitten crabs, complete sequences of the nuclear DNA internal transcribed spacer (ITS) and portions of the mitochondrial genome corresponding to the cytochrome oxidase I (COI), were sequenced for all Asian mitten crabs of the genus Eriocheir and seven species of the Grapsoidea. The resulting phylogeny supports the establishment of a separate genus Neoeriocheir, but does not provide justification for the recognition of Platyeriocheir. A female mitten crab specimen from the Zhujiang River, China, was considered to be Eriocheir recta (), a species previously synonymized with Eriocheir japonica (de Haan, 1835). In the ITS analysis, a sequence from Eriocheir formosa (from Taiwan) falls within a well-supported E. recta group, which indicates that E. formosa may have to be synonymized with E. recta. Three previously recognized members of the genus, E. japonica, Eriocheir sinensis, and Eriocheir hepuensis constitute a monophyletic sister group to E. recta in all phylogenetic trees. We provide evidence for the conspecific status of these taxa. Phylogenetic trees based on COI and combined COI and ITS sequences indicate that E. japonica consists of three subgroups. Since the name E. japonica (de Haan, 1835) takes precedence over E. sinensis (H. Milne Edwards, 1853) and E. hepuensis, we suggest that these three subgroups correspond to three subspecies of E. japonica: E. j. japonica, E. j. sinensis, and E. j. hepuensis.     

Description of the male of Sclerocypris tuberculata (Methuen, 1910) (Crustacea,Ostracoda, Megalocypridinae)

The male of Sclerocypris tuberculata (Methuen), thus far unknown, is here described. Relying on the morphology of the copulatory appendages and of the prehensile palps, it appears that this taxon belongs to a separate species group, together with S. zelaznyi and perhaps also S. sarsi. There are some interesting sexual dimorphic characters in the valve morphology: males have shorter valves with a dorsal margin which runs nearly parallel to the ventral one (more elongated valves with sloping dorsal margin in females) and there is lobe-like projection of the valve margin on the ventro-caudal corner of the LV in females which is lacking in the male. Furthermore, the female genital region has a very aberrant morphology, and all specimens from the present collection possess the tuberculated and noded valves.     

Notes on the behaviour of Ocypode ryderi Kingsley (Crustacea,Brachyura)

The main aggressive patterns of Ocypode ryderi are described: the claws can be pointed downwards in a shield‐like position against a facing opponent or out stretched against an opponent coming from behind. While the first pattern often induces an analogous reaction in the opponent and can easily be followed by a fight consisting in reciprocal claws hitting, the latter always leads to avoidance of a further attack. A waving display occurs in courtship. The main defensive patterns against predators or men consists of a zig‐zag flight towards the sea or the burrow and a “terrifying” sound emitted by striking the claws together. Running and cleaning are executed as in the majority of the Ocypode. An attempt to compare these patterns with those of other species of Ocypode has been made.     

耳鲍精子的超微结构

本文利用透射电子显微镜对耳鲍(Haliotis asinina Linnaeus)精子的形态及超微结构进行了研究.研究结果表明:耳鲍的精子由头部、中段和尾部三部分组成,全长 41.6 μm.精子头部长 1.8 μm,头部由顶体、顶体下腔和细胞核组成,顶体电子密度比较均匀,呈圆锥形,长 0.6 μm,基部宽度为 0.65 μm,占头部长的 1/3;顶体下腔长 0.03 μm,宽为 0.65 μm,腔中含有中等电子密度物质;细胞核圆棒状,长 1.17 μm,核中部的宽度为 1.0 μm.精子中段较短,长 0.51 μm,宽 1.2 μm,主要由 5 个线粒体包围一对中心粒构成.尾部是一根鞭毛,从前到后逐渐变细,鞭毛是由细胞质膜包被的轴丝组成,轴丝为典型的"9 2"微管结构,即轴丝是由两个中心微管及均匀分布在中心微管周围的 9 对双联体微管组成.因此,耳鲍与其它鲍类精子的基本结构相似,形态结构的主要差异表现在三个方面:一是耳鲍精子的头部似圆锥形,长 1.8 μm,是目前已研究的鲍类中头部最短的种类;二是耳鲍精子顶体长比其基部宽要小,顶体电子密度比较均匀,顶体与核的电子密度差异不明显;三是耳鲍精子中段线粒体的数量为 5 个,没有发现 6 个线粒体现象的存在[动物学报 53(3):552-556,2007].     

Aspects of the biology of the deep-sea spider crab, Dorhynchus thomsoni (Crustacea: Brachyura)

Pelagic first crab stages of the deep-sea spider crab, Dorhynchus thomsoni , are reported from mid-water samples taken at a variety of localities in the Porcupine Seabight and the Rockall Trough. Some of these samples were from hauls made near the surface over depths of 3000 m or more.
An analysis of these pelagic samples, and of benthic catches of D. thomsoni held by the Institute of Oceanographic Sciences and the British Museum (Natural History), indicate that most females and at least some males undergo the puberty prior to the third crab instar, these individuals therefore probably pass through a total of only three larval and three post-laval instars. There is at least a possibility that some individuals moult after the moult of puberty, unlike any other spider crabs.     

Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater

An assessment of the global freshwater crab diversity is presented. A total of 1,476 species in 14 families are currently known from all zoogeographical regions (except Antarctica), including 1,306 species in eight exclusively freshwater families (Pseudothelphusidae, Trichodactylidae, Potamonautidae, Deckeniidae, Platythelphusidae, Potamidae, Gecarcinucidae and Parathelphusidae). Estimates of true freshwater crab diversity including likely numbers of undescribed taxa suggest that the field remains largely in a “discovery” phase. Main ideas on the origins, diversification, and phylogeny of true freshwater crabs are briefly discussed. The economic importance of freshwater crabs is also highlighted. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Earthen Structures Built by Ilyoplax dentimerosa (Crustacea,Brachyura, Ocypodidae)

Under observation, the small ocypodid crab Ilyoplax dentimerosa was found to commonly build three types of earthen structures: a barricade near its neighbour's burrow, a fence at an intermediate position between the burrows of the builder and its neighbour, and a minishelter near the builder's burrow. The sex ratio of barricade builders was found to be close to 1:1, whereas most of the fence builders were found to be female. Crabs against which barricades and fences were built, were usually smaller than the builders. Both barricade builders and fence builders had, in most cases, minishelters at the side, facing the barricade or the fence. Removal and rebuilding experiments for barricades and fences demonstrated that both structures functioned to deter the approach of the builder's neighbour to the builder's activity site. Fences also had the effect of restraining the movement of the builder toward the fence site.     

The morphology of the male reproductive system,spermatogenesis and the spermatozoon of Daphnia magna (Crustacea: Branchiopoda)

This study analyses the histological and cellular morphology of the testis and sperm development in the male Daphnia magna Straus 1820. Due to the rarity of males and predominately parthenogenetic lifecycle of Daphnia , there has been limited detailed information on males in contrast to the well‐studied female. Using light and electron microscopy approaches, we describe the morphology of the testis during the progression from an immature to mature testis. The testis has an encasing muscular mesh sheath outside the basal lamina, beneath which is a thin somatic epithelial cell layer. Internal to the epithelium are the spermatogonial stem cells and subsequent syncytial clusters of the germ cells as they progress through spermatogenesis; spermatozoa occupy the entire testis in sexually mature D. magna . We describe the structure of developing and mature spermatozoa; mature spermatozoa are non‐flagellated, ovoid in shape with plasmalemma filapodia and are encased in an extracellular capsule.