An Ultrastructural Study of Spermatozoa of the Majidae with Particular Reference to the Aberrant Spermatozoon of Macropodia longirostris (Crustacea,Decapoda, Brachyura)

A total of 17 species, in 14 genera of majids have been examined for sperm ultrastructure. The present account describes the sperm of six of these species, in two subfamilies: Pisinae—Sphenocarcinus orbiculatus and Sphenocarcinus stuckiae and Inachinae—Cyrtomaia furici, Grypacheus hyalinus, Platymaia rebierei and Macropodia longirostris. M. longirostris has the only eubrachyuran sperm in which the acrosome is known to depart radically from a subspheroidal form. The acrosome is semilunar in shape and is bordered by a very thin layer of cytoplasm and an unusually uniform, narrow band of chromatin. The apical surface of the acrosome is almost flat, though slightly concave, whereas the posterior surface forms a hemisphere, and is almost completely occupied by the thin, centrally perforate, electron dense operculum. The bulk of the acrosome consists of a homogeneous, moderately electron dense outer acrosome zone. This surrounds a small inner acrosome zone internal to which is an ellipsoidal, pale perforatorium capped by a central acrosome zone. Majid sperm are distinguished by a flattened and/or centrally depressed operculum; a further characteristic is that the pointed perforatorium is relatively short and frequently does not reach the operculum. They vary inter alia with regard to presence or absence of a posterior median process and, apparently, of centrioles and of microtubules in the nuclear arms, and in the number of these arms. Perforation of the operculum, seen in the Pisinae, is not constant in the Inachinae. Spermatozoal ultrastructure offers no certain support for a close relationship of majids with parthenopids or hymenosomatids.     

The ultrastructure of the spermatozoon ofParadynomene tuberculata Sakai, 1963 (Crustacea,Brachyura, Dynomenidae): Synapomorphies with dromiid sperm

The dynomenid spermatozoon, exemplified here byParadynomene tuberculata, resembles the spermatozoa of the Dromiidae, Homolidae and lyreidine raninoids and differs markedly from those of other crabs (the heterotreme, thoracotremes, raninines and raninoidines) in the depressed, discoidal form of the acrosome and the capitate form of the perforatorium. Four or five apparent dynomenid—dromiid sperm synapomorphies are recognizable. (1) Dynomenids (P. tuberculata) and dromiids differ from homolids and lyreidines in the greater depression of the acrosome (ratio of length to width=0.3); (2) the capitate head of the perforatorium is bilaterally prolonged inP. tuberculata as in dromiids though symmetrical in homolids; (3) dynomenid and dromiid sperm lack the—albeit variably developed—posterior median process of the nucleus seen in homolids, anomurans, raninoids and lower heterotremes; (4)P. tuberculata, like dromiids and less distinctly homolids, has an apical protuberance of subopercular material through the opercular perforation, unknown in other crabs, being distinct from the apical button of thoracotreme sperm; (5) a less certain synapomorphy is the anterolateral electron-pale peripheral zone of the acrosome. These synapomorphies endorse a sister-group relationship of dynomenids and dromiids,P. tuberculata sperm differs notably from the sperm of dromiids in the more complex zonation of the acrosome. The perforatorium lacks the radial rays (“spiked wheel”) of homolid sperm and does not show the “amoeboid” form seen in lyreidines. Absence of internal corrugations of the perforatorial chamber is a major difference from all examined raninids. Centrioles are only very tentatively identifiable. Nuclear arms are absent in glutaraldehyde fixed spermatozoa ofP. tuberculata and have not been observed in the dromiidPetalomera lateralis but are present as three small radial vertices in the dromiidDromidiopsis edwardsi and in homolids.P. tuberculata resemblesPetalomera lateralis in the large size of the sperm nucleus relative to the acrosome compared withD. edwardsi and homolids.     

Ultrastructure of the spermatozoa ofCorystes cassivelaunus (Corystidae),Platepistoma nanum (Cancridae) andCancer pagurus (Cancridae) supports recognition of the Corystoidea (Crustacea, Brachyura, Heterotremata)

A combination of characters, not individually unique, possessed by the corystid,Corystes cassivelaunus, and the two cancrids,Platepistoma nanum andCancer pagurus, defines a corystoid-type of spermatozoon: the basally bulbous, anteriorly narrowing perforatorium, the extent of this almost to the plasma membrane through a widely perforate operculum, and the simple inner acrosome zone, lacking an acrosome ray zone. The sperm of the two cancrids are closely similar, that of the corystid differing, for instance, in the less pointed, and less tapered, form of the perforatorium. This relative uniformity of spermatozoal ultrastructure in the cancrid+corystid assemblage so far investigated supports inclusion of the two families in the superfamily Corystoidea by Guinot (1978). The combination of perforation of the operculum and absence of an acrosome ray zone (at least in a clearly recognizable form) are features of the Potamidae which possibly indicate that the latter family, modified for a freshwater existence, is related to the cancrid+corystid assemblage. Some elongation of the centrioles, apparent at least inCorystes, may be a further link with potamids in which they are greatly elongated. The coenospermial spermatophores of cancridoids are a notable difference from the cleistospermia of potamids; but the latter is probably an apomorphic modification for fertilization biology.     

Ultrastructure of spermatozoa of members of Calappidae,Aethridae and Menippidae and discussion of their phylogenetic placement

The families Aethridae and Calappidae were originally considered as part of the same family; however, their morphology and molecular biology separate them into two families. In this context, we describe the ultrastructure of spermatozoa of species of the Calappidae, Aethridae and Menippidae to elucidate the relationships among taxa. The vasa deferentia were submitted to routine protocols for transmission electron microscopy. Our results indicate that the morphology of the spermatozoa of Hepatus pudibundussupports its exclusion from the Superfamily Calappoidea due to the presence of the apical striated layer. The spermatozoa of Menippe nodifrons is very similar to H. pudibundus and corroborates the recent phylogenetic analysis using sequence data of nuclear genes. Moreover, our results evidence two morphological patterns of spermatozoa within Calappidae. Calappa ocellata and C. cinerea show spermatozoa with a wide acrosome vesicle, a thick operculum shaped as a shallow “W” and a large thickened ring. Calappa gallusand C. hepatica show spermatozoa with a longer acrosome vesicle, a pointed operculum and a slender thickened ring. Our ultrastructure results conform with previous molecular proposal and show that spermatozoa ultrastructure can be an effective tool to adjust phylogenetic relationship when used in association with molecular data.     

The zoeal development of Platymaia wyvillethomsoni Miers, 1886 (Crustacea: Decapoda: Majoidea: Inachidae) described from laboratory reared material

The spider crab Platymaia wyvillethomsoni was reared in the laboratory, from hatching to the megalopal stage at 20°C. The larval development comprises two zoeal stages and a megalopa. The zoeal stages are described for the first time and compared with those of the four known species of the family Inachidae from the northern Pacific. The zoeal characters (carapace spines, antenna, mouthpart appendages, pleon and telson fork) of P. wyvillethomsoni are significantly different from those of two Achaeus species from northern Pacific and other inachid genera (Inachus and Macropodia) from the Atlantic. Therefore, this species should not be placed in the family Inachidae based on zoeal morphology. A provisional key for the identification of known zoeae of the family from the northern Pacific is provided.     

The evolution of sperm ultrastructure among Boidae (Serpentes)

We investigate the evolution of sperm ultrastructure of three species of Boidae (Epicrates cenchria, Boa constrictor amarali, and Corallus hortulanus). Spermatozoa of these species are filiform consisting of a head region, containing the nucleus and acrosome complex, a midpiece, and a tail region subdivided into principal piece and endpiece. Multilaminar membranes and extracellular microtubules were observed next to the plasma membrane of the spermatozoa. The following differences were observed among the species: ridge on acrosome surface in Boa constrictor amarali (absent in Epicrates cenchria and Corallus hortulanus), stopper-like perforatorium base plate in Boa constrictor amarali and Epicrates cenchria (absent in Corallus hortulanus), rounded mitochondria in transverse section in Epicrates cenchria and Corallus hortulanus (irregular in Boa constrictor amarali). We mapped sperm characters onto two phylogenies based on morphological (Kluge in Misc Publ Mus Zool Univ Michigan 178:1–58, 1991) and molecular (Austin in Copeia 2:341–352, 2000) data, using a number of squamate species as outgroups. We identified 31 unambiguous character transformations in the morphological phylogeny and 30 in the molecular phylogeny, but only 13 and 12 transformations, respectively, are possible synapomorphies. We identified novel sperm synapomorphies, which were common between the morphological and molecular phylogenies: absence of perforatorium base plate and mitochondria arranged as sinuous tubes in oblique section (Serpentes), acrosome vesicle not subdivided and fibers 3 and 8 at the anteriormost region of principal piece (Boidae), and absence of an electron dense structure inside the proximal centriole (Elapidae + Colubridae). Our results suggest greater agreement between sperm ultrastructure and gross anatomical characters. In addition, we found no tendency for more homoplasies in the sperm head than in the flagellum, as recorded in previous studies.     

Ultrastructural comparison of the spermatozoa of Ranina ranina (Oxystomata) and of other crabs exemplified by Portunus pelagicus (Brachygnatha) (Crustacea,Brachyura)

Summary Features shared between the sperm of Ranina ranina and of the so-called higher Brachyura (the Oxyrhyncha — Cancridea — Brachygnatha assemblage, OCB) include: (1) the large subspheroidal acrosome (a synapomorphy of the Raninoidea + the OCB contrasting with the disc-shaped Dromioidea acrosome); (2) enclosure of the acrosome by a thin layer of cytoplasm which is in turn cupped by the nucleus; (3) extension of the nucleus as lateral arms and as a posterior median process (this process is absent in the more advanced families, including portunids); (4) extension of the cytoplasm into the basal region of each nuclear arm; and (5) topographical equivalence and presumed homology of components of the acrosome, viz. the electron dense capsule; inner and outer dense zones surrounding the longitudinal axis; peripheral vesicular contents; a perforate or, in Portunus, an imperforate, apical operculum; subopercular- or subcap-zone; and a basally open subacrosomal chamber enclosing perforatorial material. Significant differences of the Ranina sperm from those of the OCB, including Portunus, are: (1) anterior termination of the subacrosomal space at the equator of the acrosome and its conical form (plesiomorphy?), in the latter assemblage reaching the operculum; (2) differentiation within the subacrosomal material of a coiled, filiform putative perforatorium (plesiomorphy or apomorphic homoplasy with Anaspidacea?) whereas the entire subacrosomal contents in the OCB form a stout perforatorial rod; (3) subdivision from the acrosome vesicle in Ranina of a posterior acrosomal chamber with differentiation of the walls of this, lining the subacrosomal chamber, as longitudinal corrugations (Raninoidea autapomorphies); and (4) plesiomorphic persistence of numerous well developed, simple mitochondria in contrast to their degeneration, with greater development of a myelin-like lamellar complex, in the OCB. Spermatologically, the Raninoidea thus appear to be the plesiomorphic adelphotaxon of the Oxyrhyncha — Cancridea — Brachygnatha assemblage.Abbreviations a acrosome - ar acrosomal rays - asr anterior subacrosomal region - c centriole - ca capsule - cab central acrosomal body - ce cytoplasmic extension into arm - co corrugations - DNA DNA of arm - dt degenerating microtubules - ine disrupted inner nuclear envelope - iz inner dense zone - I part of lamellar complex - la lateral arm - m mitochondrion - npm combined nuclear and plasma membranes - o operculum - oz outer dense zone - p perforatorium - pv peripheral contents of acrosome vesicle - pcv posterior chamber of acrosome vesicle - pmp posterior median process - pp putative perforatorium - psr posterior subacrosomal region - sz subopercular zone - tr thickened ring     

Molecular phylogeny of the brachyuran crab superfamily Majoidea indicates close congruence with trees based on larval morphology

In this study, we constructed the first molecular phylogeny of the diverse crab superfamily Majoidea (Decapoda: Pleocyemata: Brachyura), using three loci (16S, COI, and 28S) from 37 majoid species. We used this molecular phylogeny to evaluate evidence for phylogenetic hypotheses based on larval and adult morphology. Our study supports several relationships predicted from larval morphology. These include a monophyletic Oregoniidae family branching close to the base of the tree; a close phylogenetic association among the Epialtidae, Pisidae, Tychidae, and Mithracidae families; and some support for the monophyly of the Inachidae and Majidae families. However, not all majoid families were monophyletic in our molecular tree, providing weaker support for phylogenetic hypotheses inferred strictly from adult morphology (i.e., monophyly of individual families). This suggests the adult morphological characters traditionally used to classify majoids into different families may be subject to convergence. Furthermore, trees constructed with data from any single locus were more poorly resolved than trees constructed from the combined dataset, suggesting that utilization of multiple loci are necessary to reconstruct relationships in this group.     

The ultrastructure of the spermatozoon of Haplotaxis ornamentus (Annelida,Oligochaeta, Haplotaxidae) and its phylogenetic significance

Summary The spermatozoon of Haplotaxis ornamentus has characteristics common to all oligochaete sperm: filiform; primary acrosome vesicle carried on an acrosome tube and containing an axial rod (perforatorium) in an invagination (subvesicular space or secondary acrosomal invagination); an elongate, highly condensed cylindrical nucleus followed by a cylindrical midpiece of radially adpressed mitochondria not penetrated by the axoneme; a single (distal) centriole persistent, though modified, at maturity; axoneme with 9 doublets, each with two outer glycogen granules, and centrally two singlets accompanied by two solid fibres. A peculiar haplotaxid combination of characters (none unique) is slight withdrawal of the primary vesicle into the acrosome tube with a strongly emergent capitulate axial rod and moderately short midpiece. This ultrastructure is consistent with location of the Haplotaxidae at the base of the Haplotaxida (Haplotaxina — Alluroidina — Moniligastrina — Lumbricina). Tubificida sperm, although also plesiomorph for the Oligochaeta, have the autapomorphy elongate periaxial sheath (secondary tube), excepting the Phreodrilidae whose sperm show convergent resemblances to the Lumbricina. The term annuloid has been introduced for annulus-like structures of varied origins.     

Ultrastructure of spermatozoa and spermatophores of old world freshwater crabs (Brachyura: Potamoidea: Gecarcinucidae,Potamidae, and Potamonautidae)

We investigated the ultrastructure of spermatozoa and spermatophores of 19 palaeotropical freshwater crab species [12 species of the Gecarcinucidae, 6 of the Potamidae (Potamiscinae), and 1 species of the Potamonautidae (Deckeniinae: Hydrothelphusini)]. The investigated Potamiscinae have densely packed coenospermic spermatophores with the exception of Thaiphusa sirikit and Johora singaporensis that exhibit cleistospermia. In contrast, in the Gecarcinucidae the spermatozoa are loosely embedded in a mucous matrix. The gecarcinucid and potamiscine sperm differ, furthermore, in acrosomal structure and size. The acrosome in the Gecarcinucidae is much smaller and spherical, while the larger acrosome in the Potamiscinae has the tendency to be depressed. In the Potamiscinae, an additional middle acrosomal zone evolved between the acrosome ray zone and the outer acrosomal zone. Within the Gecarcinucidae, a differentiation into two groups (Gecarcinucinae and Parathelphusinae) is not supported by the present spermatological data. The sperm morphology of Hydrothelphusa aff. madagascariensis (Potamonautidae: Deckeniinae) differs from Potamonautes sidneyi (Potamonautidae: Potamonautinae) in acrosomal size and shape, and in the absence of a periopercular rim. A closer relationship of Deckeniinae and Gecarcinucidae cannot be confirmed by spermatology. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.     

Spermatozoal ultrastructure in four genera of Homolidae (crustacea,decapoda): Exemplified byHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolosis boasi

The spermatozoa ofHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolopsis boasi confirm characteristics of a distinctive homolid spermatozoon previously established forHomola sp.,Paromola sp. andParomola petterdi. Homolid features are (1) moderate anteroposterior depression of the acrosome (ratio of length: width 0.4–0.6) as in lyreidine raninids (0.5), depression being greater in dromiids and dynomenids (both 0.3); (2) the capitate form of the perforatorium, shared with dromiids, dynomenids and lyreidine raninids; (3)the autapomorphic spiked-wheel form of the anterior expansion of the perforatorium; (4) horizontal zonation of the acrosome is possibly a unique synapomorphy of homolids with dromiids and dynomenids, and therefore an autapomorphy of the dromioid-homolid assemblage. In dromiids the posterior zone is proportionately the larger, while in homolids the anterior zone is the larger. The anterior zone is complexly subdivided in dynomenids; (5) the autapomorphic presence of numerous radial arranged extension of the acrosomal operculum into the perforatorium; (6) presence of nuclear arms, a symplesiomorphy of all investigated crabs, but small or questionably sometimes absent in Dromiidae; (7) absence of microtubules from the nuclear arms, as in dromiids, raninids, higher heterotremes and thoracotremes; (8) transient presence of a posterior median process of the nucleus. The process is not seen in dromiids but occurs in anomurans and lower heterotremes; (9) apical perforation of the operculum, also seen, apparently symplesiomorphically, in dromiids, raninids, and lower heterotreme families; (10) absence of an acrosome ray zone, probably homoplasic with absence in raninids; (11) location of most of the cytoplasm, including tortuous membranes and degenerating mitochondria, below the acrosome, also seen inLyreidus; (12) presence, in at least some species, of centrioles, unknown in dromiids and raninids and variable in occurrence in heterotremes.     

Characteristics and fate of the spermatozoa of Inachus phalangium (Decapoda, Majidae): description of novel sperm structures and evidence for an additional mechanism of sperm competition in Brachyura

Various aspects of the reproductive anatomy of the spider crab Inachus phalangium are investigated utilizing light and electron microscopy. Spermatozoal ultrastructure reveals the presence of a glycocalyx in the peripheral region of the periopercular rim, never recorded before in crustacean sperm cells. Sperm cell morphological traits such as semi-lunar acrosome shape, centrally perforate and flat operculum, and absence of a thickened ring, are shared only with Macropodia longirostris, confirming a close phylogenetic relationship of these species and their separation from the other members of the family Majidae. Spermatozoa are transferred to females inside spermatophores of different sizes, but during ejaculate transfer, larger spermatophores might be ruptured by tooth-like structures present on the ejaculatory canal of the male first gonopod, releasing free sperm cells. Such a mechanism could represent the first evidence of a second form of sperm competition in conflict with sperm displacement, the only mechanism of sperm competition known among Brachyura, enabling paternity for both dominant and smaller, non-dominant, males. In addition, we propose several hypotheses concerning the remote and proximal causes of the existence of large seminal receptacles in females of I. phalangium. Among these, genetically diverse progeny, reduction of sexual harassment and phylogenetic retention seem the most plausible, while acquisition of nutrients from seminal fluids, demonstrated in other arthropods, and suggested by previous studies, could be discarded on the basis of the presented data.     

Interaction between the intermediate host of Fascioliasis in Tunisia,Galba truncatula and a possible competitor,Melanoides tuberculata (Muller, 1774): a field study

The snail Melanoides tuberculata has been used successfully in the control of some snails, intermediate host of parasitosis. Melanoides tuberculata has been found in Tunisia, but its effects on populations of native snail have not yet been evaluated in the field. Our objective is to determine whether M. tuberculata competed with Galba truncatula, using a field study. Twelve monthly investigations were carried out along an irrigation system in Ain Soltane's oasis (southwest of Tunisia). Here, we describe the population dynamics of G. truncatula with and without M. tuberculata in two stations: a witness pilot station (S1), in which the snail lives alone, and an experimental station (S2), where two species live together. The abundance of G. truncatula varied according to subsistence or not of M. tuberculata. The number of annual generations is higher in S1 (four generations) than S2 (two generations). In the absence of other molluscs or predators that can influence the density of G. truncatula and assuming that climatic factors are mitigated by the presence of an oasean microclimate, these results show that the mollusc M. tuberculata has a competition with the vector species of fluke.     

Scanning electron microscopy of post-ejaculatory spermiogenesis in the tick Ornithodoros moubata

The final stages of spermiogenesis in ticks occur in the female genital tract. Scanning electron microscopy was used to follow the morphologic changes that occur in the sperm during this post-ejaculatory spermiogenesis in the African soft tick, Ornithodoros moubata, and to determine a time sequence for its occurrence in vivo. Characteristic features of the maturing and mature cell described include (1) differentiation and detachment of the operculum, (2) changes in cell shape corresponding to different developmental stages, (3) passive migration of the nucleus and acrosome from an anterior to a posterior position, and (4) eversion of that portion of the acrosomal canal containing the nucleus and acrosome. A possible fate for the remainder of the acrosomal canal is suggested by extrusion and detachment of spherical structures, the ‘posterior bubbles’, from the posterior end of the mature supermatozoon. A mechanism for cellular elongation resulting from contractions of the outer sheath is proposed.     

Sperm ultrastructure in representatives of six bivalve families from Peter the Great Bay, Sea of Japan

The ultrastructure of sperm in seven species of bivalves, the representatives of six families, Arcidae (Anadara broughtonii, Arca boucardi), Anomiidae (Pododesmus macrochisma), Tellinidae (Macoma tokyoensis), Ostreidae (Crassostrea gigas), Myidae (Mya japonica) and Trapezidae (Trapezium liratum) is described. All the studied sperm were typical tail sperm, adapted to external insemination, which, however, had a specific structure. Differences were revealed in the form of head, acrosome structure and number of mitochondria. The studied species of the above families had their specific morphology, the Arcidae species had a bullet- or barrel-shaped head with four or five mitochondria in the middle part; the Anomiidae had conic head, the acrosome with periacrosome material and four mitochondria (a basic feature of sperm is the axial core entering periacrosome material and consisting of bundle of actin filaments); the Myidae had a curved conic head and four mitochondria; in the Tellinidae the head was bullet-shaped, the periacrosome material contained a fibril component and four mitochondria; the Trapezidae had sperm of a conic form with spherical acrosome. The spherical sperm of C. gigas were similar to sperm of Saccostrea commercialis and Crassostrea virginica, but with some distinctions in the acrosome substructure. The morphology of sperm testified to the correct attribution of the Crassostreidae family as a synonym to the Ostreidae family.     

Spermatozoon ultrastructure of Aponurus laguncula (Digenea: Lecithasteridae), a parasite of Aluterus monoceros (Pisces: Teleostei)

The mature spermatozoon of Aponurus laguncula, a parasite of the unicorn leatherjacket Aluterus monoceros, was studied by transmission electron microscopy. The spermatozoon possesses 2 axonemes of the 9 + “1” trepaxonematan pattern, attachment zones, a nucleus, a mitochondrion, external ornamentation of the plasma membrane and cortical microtubules. The major features are the presence of: 1) external ornamentation in the anterior part of the spermatozoon not associated with cortical microtubules; 2) one mitochondrion; and 3) cortical microtubules arranged as a single field in the ventral side. The maximum number of microtubules is in the nuclear region. The extremities of the axonemes are characterized by the disappearance of the central core and the presence of microtubule doublets or singlets. This study is the first undertaken with a member of the Lecithasteridae and exemplifies the sperm ultrastructure for the superfamily Hemiuroidea.     

Ultrastructure of the Geogarypus nigrimanus Spermatozoon (Arachnida,Pseudoscorpionida)

The ultrastructure of the spermatozoon of Geogarypus nigrimanus (Arachnida, Pseudoscorpionida) is described. The spermatozoon is composed of a small elliptic nucleus, a short flagellum and a very long and complex acrosome. In the male genital ducts, as in other studied species of pseudoscorpions, the sperm components are rolled up to form a globular structure enclosed in a cyst wall. The Geogarypus spermatozoon with a reduced flagellum and a giant acrosome seems to be evolutionary more advanced than spermatozoa from other pseudoscorpions.