Antechiniscus in Australia: Description of Antechiniscus moscali sp. n. and Redescription of Antechiniscus parvisentus (Horning & Schuster, 1983) (Heterotardigrada: Echiniscidae)

Two species of the genus Antechiniscus have been found in Nothofagus forests in Australia. The new species A. moscali sp. n. is described. The New Zealand species A. parvisentus (Horning & Schuster, 1983) is redescribed from type material and from the new material from Australia. The taxonomic status of the two species within the genus is discussed.     

Spermiogenesis and spermatozoa ultrastructure of Aonides oxycephala (Annelida: Spionidae) from the Sea of Japan

Adults of Aonides oxycephala, common inhabitants of shallow boreal waters in the Atlantic and Pacific Oceans, release gametes into the water where fertilization and lecithotrophic larval development occur. During spermiogenesis, the acrosomal vesicle migrates from the posterior to the anterior end of the spermatid and the number of mitochondria reduces from six in early spermatids to four in mature spermatozoa. Each spermatozoon has an ovoid head with the acrosome 1.4?±?0.1?µm long and 1.6?±?0.1?µm wide and the nucleus 1.7?±?0.1?µm long and 2.3?±?0.1?µm in diameter, four spherical mitochondria, two centrioles oriented perpendicular to each other, putative glycogen in the shape of dense granules in the midpiece, and a flagellum with 9?×?2?+?2 organization of microtubules. The acrosome is a complex heterogeneous structure with five ordered layers of different electron densities, lying in a shallow depression on the anterior end of the nucleus. The nucleus is barrel-shaped (truncated ovoid) with the centriolar fossa housing the distal and proximal centrioles. Spermiogenesis and ultrastructure of spermatozoa of A. oxycephala are similar to those of another free spawning spionid, Marenzelleria viridis. Aonides and Marenzelleria have not, however, been considered as closely related taxa; thus, similarity in the morphology of their sperm might result from convergence or parallelism.     

Photokinesis of Macrobiotus hufelandi (Tardigrada, Eutardigrada)

Macrobiotus hufelandi Schultze, 1834 was tested for response to light. Size groups of less than 120 m and of 120 m or more were used. It was found that the smaller, younger size group exhibited a statistically significant negative response to light. This is hypothesized to function in conservation of body moisture and be more important to the smaller individuals because of the greater surface area-to-volume ratio. An experiment on response to gravity was done in an effort to determine if the negative photokinesis was the total result of a more complex type of behavior but this experiment did not detect any significant response to gravity in either of the size groups. Observation of the bacterial trails left by the tardigrades indicates that this behavior is not negative phototaxis, but rather negative photokinesis which is a non-directed, random movement in which the animal either increases its speed or changes its direction when exposed to light.     

Ultrastructure of Spermiogenesis in Hyla japonica (Anura,Amphibia)

Spermiogenesis in Hyla japonica was examined using transmission electron microscopy. Features which have not been reported previously during spermiogenesis of anurans include: (1) the neck of pericentriolar material is well developed, (2) the perforatorium contains many microtubules, (3) the tail is composed of axoneme and axial rod, but has no undulating membrane. Such a structure has not been described in amphibians, although it occurs in fish and mammals, and (4) the modified microtubules have one to two long projections. So far they have not been observed in any species except Gerris and Aphyosemion. With the exception of the above characteristics, the spermatozoa of Hyla japonica are remarkably similar to those of Bufo sp.     

Mastophorus muris (Nematoda: Spirurina): Ultrastructure of somatic muscle development

Hamada G. S. and Wertheim G. 1978. Mastophorus muris (Nematoda: Spirurina): ultrastructure of somatic muscle development. International Journal for Parasitology8; 405–414. The ultrastructure of the somatic muscle cells of the adult and six developmental stages of Mastophorus were studied. In all stages the cells consisted of a contractile region containing myofibrils separated by dense bands and a noncontractile region with nuclei, mitochondria, glycogen, lipid droplets and vesicles. Two sizes of myofilaments were present. The dense band contained T tubules and sarcoplasmic reticulum, and, in more advanced stages, support filaments, glycogen and dense bodies. The contractile region of the adult muscle cell consisted of several hundred irregularly shaped myofibrils arranged in a random pattern. This pattern of myofibrils was defined as irregular-coelomyarian. The third stage larva had a shallow-coelomyarian myofibril configuration, which changed to coelomyarian in the late third stage through the addition of new myofibrils at the apical contractile border. In the fourth stage larvae, the subdivision of existing myofibrils changed the pattern to irregular-coelomyarian.     

Cryptobiosis in the Eutardigrade Adorybiotus (Richtersius) coronifer: Tolerance to Alcohols, Temperature and de novo Protein Synthesis

The eutardigrade Adorybiotus (Richtersius) coronifer survives cryptobiosis for years. During entrance into anhydrobiosis this species accumulates the disaccharide trehalose reaching a maximum content of 2.3% d.w.

In the present study we examined the survival of anhydrobiotic A. (R)coronifer during exposure to alcohols of various polarity, and to high temperatures, as well as qualitative changes in protein synthesis during entrance into anhydrobiosis. Results showed that A. (R) coronifer in anhydrobiosis survived exposure to ethanol for less than 10 minutes whereas exposure to 1-butanol only decreased survival to 40% after the first 7 days and 1-hexanol did not change survival from the controls after the first 7 days. A. (R) coronifer survived temperatures up to approximately 70 °C for 60 minutes without any decrease in survival. However, survival decreased rapidly when the exposure temperature was increased to above 70 °C and no animals survived exposure to 100 °C. During the entrance into anhydrobiosis a protein with a molecular weight of approximately 71 kDa appeared on acryl amide gels showing protein bands after the animals had been incubated with ³H-Leucine. This protein may belong to the Heat-shock protein (Hsp) 70 family. The results on the survival of A. (R) coronifer during exposure to alcohols and high temperature are discussed in light of the trehalose content earlier described in this animal during anhydrobiosis.     

Anhydrobiotic Survival in Populations of the Tardigrades Richtersius coronifer and Ramazzottius oberhaeuseri from Italy and Sweden

We report a study on anhydrobiotic survival in the eutardigrades Richtersius coronifer and Ramazzottius oberhaeuseri. In each of these species, we investigated the anhydrobiotic survival of two populations, one from Sweden and one from Italy. We found that anhydrobiotic survival was similar in the Swedish and the Italian populations in both species, indicating no divergence with respect to anhydrobiotic capacity. Body size had a strong effect on the probability to recover from anhydrobiosis, but the effect was in opposite direction in the two tardigrade species. Ramazzottius oberhaeuseri had a considerable higher overall survival (66%) than R. coronifer (40%). This result is in line with earlier studies that found R. oberhaeuseri to have a very high water-retentive capacity.     

Ultrastructure of Spermiogenesis in Acanthocotyle and Myxinidocotyle (Platyhelminthes,Monogenea, Acanthocotylidae)

Abstract Spermiogenesis was studied by transmission electron microscopy in the acanthocotylid monogeneans Myxinidocotyle californica (from Eptatretus stoutii) and Acanthocotyle lobianchi (from Raja clavata). In Myxinidocotyle and Acanthocotyle, the zone of differentiation shows two 9+‘1’ axonemes, the elongating nucleus and mitochondrion, and a single cortical cytoplasmic microtubule. This single microtubule is found in the mature spermatozoon of both species and was also noted in capsalids. This requires a modified definition of ‘pattern 2’ of spermatozoa which becomes: ‘spermatozoa with two axonemes and no cortical microtubules, except one single element much shorter than the spermatozoon’. A very unusual structure was found in Myxinidocotyle, but not in Acanthocotyle: the centriolar derivative of one of the 9+‘1’ axonemes is made up of 18 diverging singlets of unequal length associated with electron-dense cytoplasm. This seems to be the first case of a centriolar derivative without nine-fold symmetry associated with an axoneme with nine-fold symmetry.     

Body wall of juvenile and adult Gastromermis boophthorae (Nematoda: Mermithidae): Ultrastructure and nutritional role

During the life cycle of the mermithid nematode Gastromermis boophthorae the main components of the body wall, namely the cuticle, hypodermis and somatic musculature, undergo radical changes in structure and relative proportions. In the non-feeding, free-living stages the cuticle is a well-defined, multilayered structure which lies upon a generally thin hypodermis; the somatic musculature has the extensive and highly organised appearance typical of motile nematodes. In parasitic juveniles the body wall has a completely different structure which is adapted for the suggested purpose of nutrient uptake from the host insect's haemocoelomic fluid; the cuticle is characteristically thin and rather diffuse, the underlying hypodermis becomes very extensive and metabolically active, and there is a corresponding reduction in the proportion of somatic musculature. The sub-cuticular surface of the enlarged hypodermis has a microvillous configuration and has associated alkaline phosphatase activity.     

Ultrastructure of spermiogenesis and synthesis of enigmatic cytoplasmic inclusions in the spirally shaped spermatozoon of the polychaete Spio setosa (Annelida: Spionidae)

The sperm of Spio setosa (Polychaeta, Spionidae) are known to be very unusual in form; here, spermiogenesis and the structure of the spermatozoon in this species are described by transmission electron microscopy. While spermiogenesis is similar to that described for many other polychaetes, two notable exceptions to this process include the synthesis of abundant ring‐shaped and tubular, membrane‐bounded cytoplasmic inclusions in the midpiece, and the differentiation of a spirally shaped sperm head. Spermatids develop as free‐floating tetrads in the male's coelom. A microtubular manchette does not develop during chromatin condensation and nuclear elongation, and the spiral acrosome forms as a single Golgi‐derived vesicle that migrates anteriorly to become housed in a deep anterior nuclear fossa. Early in spermiogenesis, numerous Golgi‐derived, membrane‐bounded cytoplasmic inclusions appear in the cytoplasm; these ultimately occupy the sperm midpiece only. The mature spermatozoon in the male has a 15‐μm‐long head consisting of a nucleus coiled like a spring and a spiral acrosome with differentiated substructure, the posterior two thirds of which sits in an anterior nuclear fossa. The midpiece is wider than the rest of the spermatozoon and contains 9–10 spherical mitochondria surrounding the two centrioles, as well as numerous membrane‐bounded conoid and tubular cytoplasmic inclusions. The axoneme has a 9 + 2 arrangement of microtubules. By contrast, stored sperm in the female's seminal receptacles have lost the midpiece inclusions but contain an abundance of glycogen. The function of the midpiece inclusions remains unresolved, and the significance of their absence in stored sperm within the seminal receptacle and the appearance of midpiece glycogen stores remains unclear and requires additional investigation.     

Ultrastructure of the spermatozoon of the American Alligator,Alligator mississippiensis (Reptilia: Alligatoridae)

This study details the ultrastructure of the spermatozoa of the American Alligator, Alligator mississippiensis. American Alligator spermatozoa are filiform and slightly curved. The acrosome is tapered at its anterior end and surrounded by the acrosome vesicle and an underlying subacrosomal cone, which rests just cephalic to the nuclear rostrum. One endonuclear canal extends from the subacrosomal cone through the rostral nucleus and deep into the nuclear body. The neck region separates the nucleus and midpiece and houses the proximal centriole and pericentriolar material. The distal centriole extends through the midpiece and has 9 × 3 sets of peripheral microtubules with a central doublet pair within the axoneme that is surrounded by a dense sheath. The midpiece is composed of seven to nine rings of mitochondria, which have combinations of concentrically and septate cristae. The principal piece has a dense fibrous sheath that surrounds an axoneme with a 9 + 2 microtubule arrangement. The sheath becomes significantly reduced in size caudally within the principal piece and is completely missing from the endpiece. Dense peripheral fibers, especially those associated with microtubule doublets 3 and 8, penetrate into the anterior portion of the principal piece axoneme. The data reported here hypothesize that sperm morphology is highly conserved in Crocodylia; however, specific morphological differences can exist between species. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Ultrastructure of spermiogenesis in the American alligator,Alligator mississippiensis (Reptilia,Crocodylia, Alligatoridae)

Testicular samples were collected to describe the ultrastructure of spermiogenisis in Alligator mississipiensis (American Alligator). Spermiogenesis commences with an acrosome vesicle forming from Golgi transport vesicles. An acrosome granule forms during vesicle contact with the nucleus, and remains posterior until mid to late elongation when it diffuses uniformly throughout the acrosomal lumen. The nucleus has uniform diffuse chromatin with small indices of heterochromatin, and the condensation of DNA is granular. The subacrosome space develops early, enlarges during elongation, and accumulates a thick layer of dark staining granules. Once the acrosome has completed its development, the nucleus of the early elongating spermatid becomes associated with the cell membrane flattening the acrosome vesicle on the apical surface of the nucleus, which aids in the migration of the acrosomal shoulders laterally. One endonuclear canal is present where the perforatorium resides. A prominent longitudinal manchette is associated with the nuclei of late elongating spermatids, and less numerous circular microtubules are observed close to the acrosome complex. The microtubule doublets of the midpiece axoneme are surrounded by a layer of dense staining granular material. The mitochondria of the midpiece abut the proximal centriole resulting in a very short neck region, and possess tubular cristae internally and concentric layers of cristae superficially. A fibrous sheath surrounds only the axoneme of the principal piece. Characters not previously described during spermiogenesis in any other amniote are observed and include (1) an endoplasmic reticulum cap during early acrosome development, (2) a concentric ring of endoplasmic reticulum around the nucleus of early to middle elongating spermatids, (3) a band of endoplasmic reticulum around the acrosome complex of late developing elongate spermatids, and (4) midpiece mitochondria that have both tubular and concentric layers of cristae. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

芬兰贝氏藻(硅藻门)的超微结构研究

以采集于青海湖的石附生硅藻(芬兰贝氏藻)为样品,用10%的HCl溶液溶解样品中含钙的固体化合物,再加入30% H₂O₂溶液氧化去掉硅藻细胞的有机物质,获得干净的硅藻标本。利用Naphrax^ 封装剂制成永久装片,在光学和电子显微镜下对其形态特征进行了详细研究。结果表明：(1) 在光学显微镜下芬兰贝氏藻具有披针形的壳瓣外形、尖圆的壳面末端和明显伸长的中轴区三个特征。(2) 在扫描电子显微镜下芬兰贝氏藻紧邻中央区的孔纹明显伸长,其长度为2～4个正常孔纹的长度。(3) 通过文献查阅和相似种类的比较发现,同时具有尖圆的末端和明显伸长的紧邻中央区的孔纹是芬兰贝氏藻鉴定的独特性状组合,故芬兰贝氏藻的身份可由此确定。该研究首次报道了芬兰贝氏藻在中国的分布。