Ultrastructure of the spermatozoon of Myrmecocichla formicivora (Vieillot, 1881) and Philetairus socius (Latham, 1790) (Aves; Passeriformes), with a new interpretation of the passeridan acrosome

Passerine spermatozoa exhibit apomorphies that distinguish them from non-passerine neognaths and palaeognaths. The acrosome is longer than the nucleus (excepting the suboscines, most Corvida, and a few Passerida). A perforatorium and endonuclear canals are absent. The proximal centriole is absent (except in the suboscines). The distal centriole is secondarily short, contrasting with its elongate condition in palaeognaths and Galloanserae. In the Passerida a single mitochondrial strand winds extensively along the axoneme (restricted to the anterior axoneme in suboscines and Corvida). A fibrous, or amorphous, periaxonemal sheath, seen in palaeognaths and many non-passerines, respectively, is absent. The acrosome in Myrmecocichla formicivora and Philetairus socius is bipartite: an acrosome core is surmounted by an acrosome crest; the core is ensheathed by a layer which is a posterior extension of the crest. The acrosome helix is a lateral extension of the crest and the crest layer with (Myrmecocichla) or without (Philetairus) protrusion of material of the acrosome core into it. In M. formicivora, as in other muscicapoids, a fibrous helix is intertwined with at least the more proximal region of the mitochondrial helix. The fibrous helix is absent at maturity in Philetairus and other described passeroid spermatozoa with the possible exception of Passer italiae. In Philetairus a granular helix precedes the mitochondrial helix.

Ultrastructure of the mature spermatozoon of the musky rat-kangaroo, Hypsiprymnodon moschatus (Potoroidae : Marsupialia)

It is currently accepted that Hypsiprymnodon moschatus is a basal macropod, retaining several primitive features from the ancestral phalangeroid that gave rise both to modern possums and macropods. Sperm ultrastructure is frequently found to provide informative characters for phylogenetic analysis as these features are not strongly selected for and are thus unlikely to be confounded by effects such as convergence. Caudal epididymal biopsies were taken from two male H. moschatus and prepared for transmission and scanning electron microscopy in order to study mature spermatozoan ultrastructure. Within the diprotodont group, several features were found to be unique to H. moschatus. These were an unusual acrosome covering nearly 100% of the dorsal nuclear surface, a midpiece fibre network which is loose, indistinct and extends to the anterior-most aspect of the midpiece, a nucleus that is very streamlined, while the principal piece is comparatively short, and a mitochondrial helix and annulus which are similar to those of dasyurids. Also reported is the presence of a fibrous network in die connecting piece, not previously reported for any marsupial.

Ultrastructure of the mature spermatozoa of caecilians (Amphibia : Gymnophiona)

The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta-axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapornorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, an 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Axiura. J. Morphol. 258:179-192, 2003. (C) 2003 Wiley-Liss, Inc.

Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implications

The spermatozoon of Apus apus is typical of non-passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non-passerines. All non-passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non-passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA-DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae.

Ultrastructure of the spermatid of Caprimuigus europaeus Linnaeus 1758, the European Nightjar (Aves; Caprimulgidae), with phylogenetic implications

The sperm of Caprimulgus europaeus is typical of other nonpasserines in many respects. Features shared with Paleognathae and Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a perforatorium and endonuclear canal; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around a central axis (here maximally six mitochondria in similar to 10 tiers); and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. A major (apomorphic) difference from paleognaths and galloanserans is the short distal centriole, the midpiece being penetrated for most of its length by the axoneme and for only a very short proximal portion by the centriole. Nonpasserines differ from paleognaths in that the latter have a transversely ribbed fibrous sheath, whereas in nonpasserines it is amorphous, as in Caprimulgus, or absent. The absence of an annulus is an apomorphic feature of Caprimulgus, apodiform, psittaciform, gruiform, and passerine sperm, homoplastic in at least some of these. In contrast to passerines, in Caprimulgus the cytoplasmic microtubules in the spermatid are restricted to a transient longitudinal manchette. The structure of the spermatid and spermatozoon is consistent with placement of the Caprimulgidae near the Psittacidae, but is less supportive of close proximity to the Apodidae, from DNA-DNA hybridization and some other analyses.

Retinal and lenticular ultrastructure in the aestivating salamanderfish, Lepidogalaxias salamandroides (Galaxiidae, Teleostei) with special reference to a new type of photoreceptor mosaic

The salamanderfish, Lepidogalaxias salamandroides (Galaxiidae, Teleostei) is endemic to southwestern Australia and inhabits shallow, freshwater pools which evaporate during the hot summer months. Burrowing into the substrate in response to falling water levels allows these fish to aestivate for extended periods of time while encapsulated in a mucous cocoon even when the pools contain no water. Only a few minutes after a major rainfall, these fish emerge into relatively clear water which subsequently becomes laden with tannin, turning the water black and reducing the pH to approximately 4.3. As part of a large study of the visual adaptations of this unique species, the retinal and lenticular morphology of the aestivating salamanderfish is examined at the level of the light and electron microscopes. The inner retina is highly vascularised by a complex system of vitreal blood vessels, while the outer retina receives a blood supply by diffusion from a choriocapillaris. This increased retinal blood supply may be an adaptation for reducing the oxygen tension during critical periods of aestivation. Large numbers of Muller cells traverse the thickness of the retina from the inner to the outer limiting membranes. The ganglion cells are arranged in two ill-defined layers, separated from a thick inner nuclear layer containing two layers of horizontal cells by a soma-free inner plexiform layer. The photoreceptors can be divided into three types typical of many early actinopterygian representatives; equal double cones, small single cones and large rods (2:1:1). These photoreceptors are arranged into a unique regular square mosaic comprising a large rod bordered by four equal double cones with a small single cone located at the corner of each repeating unit. The double cones may optimise perception of mobile prey which it tracks by flexion of its head and neck and the large rods may increase sensitivity in the dark tannin-rich waters in which it lives. Each single cone also possesses a dense collection of polysomes and glycogen (a paraboloid) beneath its ellipsoid, the first such finding in teleosts. The retinal pigment epithelium possesses melanosomes, pha,oocytes and a large number of mitochondria. The anatomy of the retina and the photoreceptor mosaic is discussed in relation to the primitive phylogeny of this species and its unique life history.

Isolation and characterization of a Clostridium sp with cinnamoyl esterase activity and unusual cell envelope ultrastructure

Microorganisms that hydrolyse the ester linkages between phenolic acids and polysaccharides in plant cell walls are potential sources of enzymes for the degradation of lignocellulosic waste. An anaerobic, mesophilic, spore-forming, xylanolytic bacterium with high hydroxy cinnamic acid esterase activity was isolated from the gut of the grass-eating termite Tumilitermes pastinator. The bacterium was motile and rod-shaped, stained gram-positive, had an eight-layered cell envelope, and.formed endospores. Phylogenetic analysis based on 16S rRNA indicated that the bacterium is closely related to Clostridium xylanolyticum and is grouped with polysaccharolytic strains of clostridia. A wide range of carbohydrates were fermented, and growth was stimulated by either xylan or cellobiose as substrates. The bacterium hydrolysed and then hydrogenated the hydroxy cinnamic acids (ferulic and p-coumaric acids), which are esterified to arabinoxylan in plant cell walls. Three cytoplasmic enzymes with hydroxy cinnamic acid esterase activity were identified using non-denaturing gel electrophoresis. This bacterium possesses an unusual multilayered cell envelope in which both leaflets of the cytoplasmic membrane, the peptidoglycan layer and the S layer are clearly discernible. The fate of all these components was easily followed throughout the endospore formation process. The peptidoglycan component persisted during the entire morphogenesis. It was seen to enter the septum and to pass with the engulfing membranes to surround the prespore. It eventually expanded to form the cortex, verification for the peptidoglycan origin of the cortex. Sporogenic vesicles, which are derived from the cell wall peptidoglycan, were associated with the engulfment process. Spore coat fragments appeared early, in stage II, though spore coat formation was not complete until after cortex formation.

Echinobothrium chisholmae n. sp (Cestoda, Diphyllidea) from the giant shovel-nose ray Rhinobatos typus from Australia, with observations on the ultrastructure of its scolex musculature and peduncular spines

Echinobothrium chisholmae n. sp. is described from Rhinobatos typus Bennett (Rhinobatidae), collected from Heron Island, Great Barrier Reef, Australia. E. chisholmae differs from all congeners in possessing 11 hooks in each dorsal and ventral group on the rostellum and groups of 3-6 hooklets on either side of the hooks. A single metacestode of E. chisholmae was collected from the decapod crustacean Penaeus longistylus Kubo. Yellow pigmentation of the cephalic peduncle in immature adults is caused by the accumulation of large vesicles in the distal cytoplasm of the tegument. The vesicles probably provide materials for spine formation. Ultrastructural examination of the rostellar musculature revealed that the muscles are stratified (striated-like), consisting of a periodic repetition of sarcomeres separated by perforated Z-like lines that are oblique to the long axes of the myofilaments.

Ultrastructure and small-subunit ribosomal DNA sequence of Henneguya lesteri n. sp (Myxosporea), a parasite of sand whiting Sillago analis (Sillaginidae) from the coast of Queensland, Australia

Henneguya lesteri n. sp, (Myxosporea) is described from sand whiting, Sillago analis, from the southern Queensland coast of Australia. H. lesteri displays a preference for the pseudobranchs and is typically positioned along the afferent blood vessels, displacing the adjoining lamellae and disrupting their normal array, The plasmodia appeared as whitish-hyaline, elliptical cysts (mean dimensions 230 x 410 mum) attached to the oral mucosa lining of the hyoid arch on the inner surface of the operculum. Infections of the gills were also found, in which the plasmodia were spherical, averaged 240 x 240 mum in size and were located on the inner hemibranch margin. The parasites lodged in the gill filament crypts and generated a mild hyperplastic response of the branchial epithelium, In histological sections, the plasmodium wall and adjoining ectoplasm appeared as a finely granulated, weakly eosinophilic layer, Ultrastructurally, this section of the host-parasite interface contained an intricate complex of pinocytotic channels. H. lesteri is polysporic, disporoblastic and pansporoblast forming. Sporogenesis is asynchronous, with the earliest developmental stages aligned predominantly along the plasmodium periphery, and maturing sporoblasts and spores toward the center. Ultrastructural details of sporoblast and spore development are in agreement with previously described myxosporeans. The mature spore is drop-shaped, length (mean) 9.1 mum, width 4.7 mum, thickness 2.5 mum, and comprises 2 polar capsules positioned closely together, a binucleated sporoplasm and a caudal process of 12.6 mum. The polar capsules are elongated, 3.2 x 1.6 mum, with 4 turns of the polar filament. Mean length of the everted filament is 23.2 mum, Few studies have analyzed the 18S gene-of marine Myxosporea. In fact, H. lesteri is the first marine species of Henneguya to be characterized at the molecular level: we determined 1966 bp of the small-subunit (18S) rDNA, The results indicated that differences between this and the hitherto studied freshwater Henneguya species are greater than differences among the freshwater Henneguya species.

Spermatozoal ultrastructure of spiny oysters (Spondylidae, Bivalvia) including a comparison with other bivalves

Sperm ultrastructure in three representative species of the marine bivalve family Spondylidae (spiny or thorny oysters) is examined and compared with available data on other bivalves, especially other families of the subclass Pteriomorphia. Spondylid spermatozoa are of the externally fertilizing aquasperm. type (ect-aquasperm). The acrosomal vesicle is conical with a deep basal invagination extending almost the full length of the vesicle. Vesicle contents are divisible into an inner, highly electron-dense anterior layer and a less dense posterior layer. The anterior layer is folded back on itself posteriorly and exhibits radiating plates (best developed peripherally). The vesicle rests on, and is partially embedded in, an extensive granular deposit of subacrosomal. material at the nuclear apex. This deposit extends partly into acrosomal vesicle invagination and also fills a broad depression in the anterior of the nucleus. No pre-formed axial rod (perforatorium) is present. The nucleus is round-pyriform and its contents coarsely fibrogranular. At the base of the nucleus, four broad depressions partially accommodate the midpiece mitochondria. The midpiece consists the four spherical mitochondria and the proximal and distal centrioles. The centrioles are arranged at approximately 90degrees to each other, and each consists of nine, angularly-oriented, microtubular triplets embedded in a granular matrix. A short, periodically banded rootlet connects the proximal centriole to the nuclear fossa, whereas the distal centriole, which forms the basal body to the flagellar axoneme, is anchored to the plasma membrane by nine terminally forked satellite fibres. Extensive deposits of putative glycogen rosettes surround the centrioles and mitochondria. The flagellum consists of a 9+2 axoneme sheathed by the plasma membrane. Spondylid spermatozoa strongly resemble those of the Pectinidae, further confirming the traditional view (based on comparative anatomy and shell morphology) of a close relationship between the Spondylidae and the Pectinidae. Differences in acrosomal shape and dimensions were noted between the three species examined, indicating potential taxonomic utility for comparative sperm ultrastructure within the Spondylidae.

Descriptions of the mature spermatozoa of the lizards Crotaphytus bicinctores, Gambelia wislizenii (Crotaphytidae), and Anolis carolinensis (Polychrotidae) (Reptilia, Squamata, Iguania)

The spermatozoa of Crotaphytus bicinctores and Gambelia wislizenii (Crotaphytidae), and Anolis carolinensis (Polychrotidae) exhibit the squamate autapomorphies of a single perforatorium extending anteriorly from the apical tip of the paracrystalline subacrosomal cone, the presence of an epinuclear electron-lucent region, and extension of the fibrous sheath into the midpiece. Crotaphytid sperm differ from those of polychrotids in several respects, including: the structure of the perforatorium, the size of the epinuclear electron-lucent region, aspects of the acrosome complex, the arrangement and structure of intermitochondrial dense bodies, and in the distance the fibrous sheath extends into the midpiece. The sperm of C. bicinctores, G. wislizenii, and A. carolinensis are most similar to those of the agamids and phrynosomatids examined to date. No spermatozoal autapomorphies for Crotaphytidae or Polychrotidae were found. The condition of having the intermitochondrial dense bodies arranged in regular incomplete rings is tentatively defined as a synapomorphy of Iguania (although modified in Chamaeleonidae). Spermatozoal ultrastructure offers no characters that justify the separation of Iguanidae (sensu late) into several separate families. (C) 2001 Wiley-Liss, Inc.

Ecology, shell morphology, anatomy and sperm ultrastructure of the caenogastropod Pyrgula annulata, with a discussion of the relationship between the 'Pyrgulidae' and Caspian and Baikalian rissooideans

The composition of the Pyrgulidae and its relationships to other member families of the caenogastropod superfamily Rissooidea are examined after a consideration of new anatomical (including gross anatomy, sperm ultrastructure), conchological (including protoconch features), ecological, biogeographical and palaeontological data and a re-evaluation of existing literature. Pyrgulidae can be distinguished from hydrobiids unequivocally only with the aid of the radula. Sperm ultrastructural features suggest a very close relationship between the Pyrgulidae, the Hydrobiidae and the Bithyniidae (in fact no family-diagnostic sperm characters can be found to separate these three taxa). Based upon neontological and fossil evidence it is likely that pyrgulids represent a Miocene offshoot from a paratethyal hydrobiid lineage. Pyrgulids may also represent the stock from which the baicaliids arose, in which case the Pyrgulidae must be considered a paraphyletic group. The huge biogeographic gap between the Caspian Sea and Lake Baikal is to some extent bridged by the finding of a Neogene pyrgulid from the Altai Mountains. An alternative scenario for the origin of baicaliids is presented.