Gamete ultrastructure in two species of the genus Upeneus (Mullidae) from the South China Sea

Ultrastructure of envelopes of ovulated oocytes and spermatozoon ultrastructure are described in two closely related species of the family Mullidae, Upeneus tragula and U. cf. margarethae. Oocyte envelope is represented by the thin zona radiata and weakly expressed chorion. The spermatozoon is characterized by the presence of elongated head with a pointed bend in its apical part and nuclear fossa reaching approximately 90% of the head length. The centriolar complex and basal part of the flagellum are located inside of the nuclear fossa.     

Ultrastructural study of the spermatozoon of Heterolebes maculosus (Digenea,Opistholebetidae), a parasite of the porcupinefish Diodon hystrix (Pisces,Teleostei)

This paper describes the ultrastructure of the mature spermatozoon of Heterolebes maculosus. It is the first study of this kind concerning the Opistholebetidae (Platyhelminthes, Digenea). The ultrastructural elements observed in the spermatozoon are: two axonemes with 9+“1” pattern of Trepaxonemata and their attachment zones, two mitochondria, a nucleus, cortical microtubules, external ornamentation of the plasma membrane and spine-like bodies. The number and the disposition of cortical microtubules, the organisation of 11 cortical microtubules disposed in semi-circle around the first mitochondrion in the external ornamentation region and the organisation of the posterior part of the spermatozoon are discussed. Three principal types of posterior part of digenean spermatozoa are proposed. The similarity between the spermatozoon of the Opistholebetidae H. maculosus and Opecoelidae enables us to confirm that these two families are closely related.     

Structural features of the spermatozoon of a passeridan bird,the Carib grackle,Quiscalus lugubris

The spermatozoon of the Carib grackle, Quiscalus lugubris, a member of the family Icteridae, is generally similar in organization to the passerine-type of spermatozoon, in being highly elongated and displaying a helical structure of the acrosome, nucleus and principal piece of the tail. There are subtle variations in acrosomal structural features between this organelle in the grackle and that in some of the very few passerine species of birds in which the spermatozoon has been studied. The proximal centriole is present, and, thus, the Carib grackle is the third passeridan bird in which this organelle, hitherto regarded as absent in passerine birds, has been described in the spermatozoon. The spermatozoon of this bird also possesses a granular helix, which feature has been found variably even in the scanty available reports on passerine spermatozoa. It is advocated that the spermatozoon be studied in many more species of this large clade of birds. This report provides a basis for the study of spermiogenesis in the Carib grackle, with the aim of exposing, inter alia, a number of developmental features and processes of certain organelles that have received attention, recently, in the spermatozoa of passerine birds.     

Ultrastructural characteristics of the mature spermatozoon of the digenean Sclerodistomum italicum (Stossich, 1893) (Hemiuroidea,Sclerodistomidae) intestinal parasite of Hypocanthus amia (Teleostei,Carangidae)

The mature spermatozoon of Sclerodistomum italicum is filiform, tapered at both ends and shows the following features: 2 axonemes of the 9 + “1” pattern of the Trepaxonemata, mitochondrion, nucleus and parallel cortical microtubules. The specific features of the spermatozoon of S. italicum include the simultaneous presence of two types of extramembranous ornamentations, the presence of short cortical microtubules in the anterior part of the spermatozoon and the presence of only one bundle of cortical microtubules in the median part of the spermatozoon. Thus far these structures are known only in the Hemiuroidea. The presence of filamentous ornamentation in the anterior extremity of the spermatozoon has not previously been described in the Sclerodistomidae. Similar to spermatozoa of other hemiuroideans, S. italicum lack spine-like bodies described in spermatozoa of many digenean taxa. The posterior extremity of the spermatozoon exhibits the same ultrastructural characteristics typical of the Hemiuroidea.     

Spermatological characteristics of the Trypanorhyncha inferred from new ultrastructural data on species of Tentaculariidae,Eutetrarhynchidae, and Progrillotiidae

The present study focuses on the ultrastructural characteristics of both spermiogenesis and the spermatozoon in the order Trypanorhyncha. New ultrastructural data are presented for two species of the unexplored superfamily Tentacularioidea, Nybelinia queenslandensis, and Kotorella pronosoma. The present study also provides supplementary data on the superfamily Eutetrarhynchoidea, with the analysis of spermiogenesis and spermatozoon of two progrillotiids, Progrillotia dasyatidis and Pro. pastinacae, and new ultrastructural data concerning spermiogenesis in the eutetrarhynchids Dollfusiella spinulifera and Parachristianella trygonis. Spermiogenesis in trypanorhynchs follows the Bâ and Marchand's type I and the ultrastructural organisation of the mature spermatozoon corresponds to the Levron et al.’s type I. The most remarkable characters concerns the number of electron-dense plates constituting the intercentriolar body during spermiogenesis and in the variability of the arc-like row of thick cortical microtubules present in the anterior areas of the spermatozoon because of its variability according to the species.     

The use of poly-L-lysine to facilitate examination of sperm entry into pelagic, non-adhesive fish eggs

The fish egg is surrounded by a thick envelope called the chorion. The fertilizing spermatozoon enters the egg through a canal-like structure in the chorion, the micropyle. Examination of micropyle at fertilization is difficult if eggs are large and have no distinct landmarks surrounding the micropyle, or if they are positively buoyant in water. Eggs of many commercially important fishes (e.g., flounder, sea bream and eel) are buoyant in water or only slightly adhere to solid objects (e.g., sands, rock and water plants), which makes observation of spermatozoa at fertilization difficult. Here, we report that such eggs can be firmly attached to plastic and glass dishes that have been previously coated with poly-L-lysine. These adhering eggs can be fertilized and develop normally on the dishes. Observations of micropyles of three fish species, before and after sperm entry are presented.     

Egg chorion tanning in Aedes aegypti mosquito

The biochemical pathway of egg chorion tanning in the mosquito, Aedes aegypti, is described and compared with chorion protein crosslinking in Drosophila and silkmoths and the biochemical pathways of cuticular tanning in insects. Phenol oxidase, dopa decarboxylase and tyrosine are critical components involved in egg chorion tanning in A. aegypti. Tanning of the mosquito egg chorion is initiated following activation of phenol oxidase, which then catalyzes the hydroxylation of tyrosine to dopa and further oxidizes dopa and dopamine to their respective o-quinones. Because intramolecular cyclization is much slower in dopaminequinone than dopaquinone, the chance to react with external nucleophiles to participate in protein crosslinking reactions also is much greater in dopaminequinone than dopaquinone. This might partly explain the necessity for the involvement of dopa decarboxylase in mosquito chorion tanning. Intramolecular cyclization of dopaquinone and dopaminequinone to form dopachrome and dopaminechrome, respectively, the structural rearrangement of these aminochromes to produce 5,6-dihydroxyindole, and the subsequent oxidation of 5,6-dihydroxyindole by phenol oxidase also lead to melanin formation during egg chorion tanning.     

Ultrastructural study of the male gamete of Glossobothrium sp. (Cestoda: Bothriocephalidea: Triaenophoridae) a parasite of Schedophilus velaini (Perciformes: Centrolophidae) in Senegal

This paper describes the ultrastructure of the male gamete of Glossobothrium sp. (Bothriocephalidea: Triaenophoridae). The mature spermatozoon of Glossobothrium sp. is filiform and possesses two axonemes, a single helicoidal crested body, a parallel nucleus, parallel cortical microtubules and granules of glycogen. In Glossobothrium sp. we describe for first time a 200-250 nm thick crest-like body in the Bothriocephalidean. The anterior part of the spermatozoon exhibits a ring of 27 electron-dense cortical microtubules encircling the first axoneme. This structure persists until the appearance of the second axoneme. When the ring of electron-dense cortical microtubules disappears, the spermatozoon exhibits two bundles of thin cortical microtubules. The posterior part of the spermatozoon contains the posterior extremity of the second axoneme, the posterior extremity of the nucleus and few cortical microtubules. Soon nucleus disappears and the axoneme is disorganized. Thus the posterior extremity of the spermatozoon of Glossobothrium sp. exhibits only singlets produced by the disorganization of the doublets of the second axoneme and few cortical microtubules. This type of posterior extremity of the mature spermatozoon has never been described previously in the Triaenophoridae.     

Cell-free translation of silkmoth chorion mRNAs: Identification of protein precursors and characterization of cloned DNAs by hybrid-selected translation

The secretory silkmoth chorion proteins are synthesized as precursors bearing signal peptides. Precursors are detected upon cell-free translation of chorion mRNAs in the wheat germ system; they are processed into products identical in size to authentic chorion proteins when translation is performed in the presence of microsomal membranes from dog pancreas. Precursors corresponding to specific protein size classes and subclasses are identified by three approaches: comparison of precursors and products encoded by stage-specific mRNAs, comparison of precursors and products encoded by mRNAs specifically hybridizing to individual chorion cDNA clones, and comparison of relative amino acid compositions of precursors and authentic chorion proteins. Translation of stage-specific mRNA preparations indicates that, in general, the developmental changes of in vivo chorion protein synthesis are based on changes in concentrations of the corresponding mRNAs. Characterization of the precursors makes it possible to identify, for any chorion DNA clone, the protein subclass, a member of which is encoded by the clone sequence.     

Ultrastructural diversity in the egg chorion of Hawaiian Drosophila and Scaptomyza: ecological and phylogenetic considerations

Formation of the egg shell (chorion) inDrosophila and Scaptomyza (Diptera : Drosophilidae) is a complex developmental process involving coordinated synthesis and secretion of multiple proteins by the monolayer of follicle cells surrounding the egg. Using scanning electron microscopy, the ultrastructure of the chorion in 37 endemic Hawaiian drosophilids, representing the genera Drosophila and Scaptomyza, were analyzed and compared with 7 representative species of continental Drosophila. The detailed structure of the chorion was described for 8 chorionic regions: the respiratory filaments, follicle imprints, operculum, micropyle, dorsal ridge, ventral rim, posterior pole, and the chorion cross-section. The morphology of each region is similar among related species, but strikingly different among groups. The main functions of the chorion are to protect the developing embryo from the vicissitudes of the environment and to provide channels for gas exchange during embryogenesis. Adaptation to the diverse ovipositional substrates used by Drosophila in general, and the Hawaiian species in particular, has resulted in extraordinary diversity in the various chorionic structures. The respiratory filaments differ in number and have evolved to different lengths and degrees of porosity. Furthermore, other regions also involved in respiratory exchange (the operculum, follicle imprints, the pole region, and the dorsal ridge) have diverged in parallel to the ecological divergence. The thickness and complexity of the outer endochorion are dramatically different in various groups, providing varying degrees of mechanical strength to the eggshell, which promotes embryonic survival in the diverse microenvironments. These varied chorionic structures have been found to provide useful morphological characters for phylogenetic analyses of the drosophilids.     

Ultrastructure of the spermatozoon of Anomotaenia quelea (Mettrick, 1961) (Cestoda,Cyclophyllidea, Dilepididae), an intestinal parasite of Quelea quelea (Aves,Ploceidae) in Senegal

The mature spermatozoon of Anomotaenia quelea exhibits an apical cone of electron-dense material and two helicoidal crest-like bodies. The apical cone near its base is surrounded by a lucent cytoplasm and a spiraled layer of cortical microtubules. The crest-like bodies are of different lengths, spiraled and make an angle of 30–40° to the hypothetical spermatozoon axis. The axoneme is of the 9 + ‘1’ trepaxonematan pattern and is surrounded by a periaxonemal sheath of electron-dense material. The cytoplasm contains in regions III and IV numerous electron-dense granules situated between the periaxonemal sheath and the cortical microtubules. The posterior extremity of the spermatozoon of A. quelea exhibits a nucleus and a disorganized axoneme and cortical microtubules. This type of posterior extremity of the mature spermatozoon has never been described previously in a Dilepididae. Similarly, two crest-like bodies have not been observed before in a dilepidid cestode.     

Karyotypic study of some species of family Mochokidae (Pisces, Siluriformes): evidence of female heterogamety

The relationship between the specific anatomy of tilapia gametes and their function was studied in the sequence of events which follow artifical fertilization. Scanning electron microscopic observations showed that some events of the fertilization process, involving spermatozoon migration through the micropylar canal until reaching the villous plasma membrane of the eggs and its penetration into the egg cytoplasm, occur very rapidly (fractions of a second). However, the spermatozoon tail remains outside for about 1–2 min. Then, following the zygote formation and the elevation of the chorion after its separation from the plasma membrane, numerous sperm cells could be found in the vicinity of the micropyle. This cell mass, which seemed to be trapped by a network of microfilaments, was suggested to be the result of the evacuation of excess sperm cells throughout the micropylar canal. The significance of these results for sperm and egg plasma membrane interaction and for prevention of polyspermy are discussed.     

Ultrastructure of the spermatozoon of the digenean Cricocephalus albus (Kuhl & van Hasselt, 1822) Looss, 1899 (Platyhelminthes, Pronocephaloidea, Pronocephalidae), parasite of “the hawksbill sea turtle” Eretmochelys imbricata (Linnaeus, 1766) in Senegal

The mature spermatozoon of Cricocephalus albus is filiform, tapered at both ends and shows the following features: 2 axonemes of different lengths presenting the 9 + “1” trepaxonematan pattern, 2 bundles of parallel cortical microtubules, a mitochondrion and a nucleus. Nevertheless, the particularity of the spermatozoon of C. albus is its anterior extremity with an apical electron-dense material associated with extramembranar ornamentation, a cytoplasmic dorsolateral expansion and spine-like bodies. To our knowledge, such an anterior extremity of the spermatozoon has not previously been described from a species of the superfamily Pronocephaloidea. Our study provides new data on the mature gamete of C. albus in order to improve our understanding of the pronocephaloidean phylogenetic relationships.     

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9 + “1” trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.     

Ultrastructure of the spermatozoon of Anomotaenia quelea (Mettrick, 1961) (Cestoda,Cyclophyllidea, Dilepididae), an intestinal parasite of Quelea quelea (Aves,Ploceidae) in Senegal

The mature spermatozoon of Anomotaenia quelea exhibits an apical cone of electron-dense material and two helicoidal crest-like bodies. The apical cone near its base is surrounded by a lucent cytoplasm and a spiraled layer of cortical microtubules. The crest-like bodies are of different lengths, spiraled and make an angle of 30–40° to the hypothetical spermatozoon axis. The axoneme is of the 9 + ‘1’ trepaxonematan pattern and is surrounded by a periaxonemal sheath of electron-dense material. The cytoplasm contains in regions III and IV numerous electron-dense granules situated between the periaxonemal sheath and the cortical microtubules. The posterior extremity of the spermatozoon of A. quelea exhibits a nucleus and a disorganized axoneme and cortical microtubules. This type of posterior extremity of the mature spermatozoon has never been described previously in a Dilepididae. Similarly, two crest-like bodies have not been observed before in a dilepidid cestode.     

Specific protein synthesis in cellular differentiation: VI. Temporal expression of chorion gene families in Bombyx mori strain C108

Detailed patterns of expression for putative members of 5 major chorion gene families have been obtained by separating labeled proteins using two-dimensional polyacrylamide gel electrophoresis. Proteins fall into 4 temporal cohorts called early, early middle, middle, and late on the basis of when they initiate and terminate synthesis. Proteins synthesized during the early, early middle, and late periods are highly synchronous, exhibiting abrupt onset times and relatively uniform termination times. Middle proteins begin synthesis in small groups at staggered times over a relatively long period, but most cease translation as the late proteins turn on. This data is correlated with a previous follicle staging system based on separation of newly synthesized chorion proteins by isoelectric focusing alone. The absolute timing of choriogenesis was determined in vivo, using trypan blue dye to mark vitellogenic follicles. The relative age difference between chorionating follicles was 2.2–2.6 hr; chorion biosynthesis took 4 days in all. These data are discussed in terms of patterns of activity of chorion gene families, the functions of the temporal cohorts, and regulation of the chorion multigene system.     

Identification and cytochemical study of an extranuclear basic protein in the spermatozoa of decapod crustaceans

Extranuclear basic proteins have been detected in the capsule of the spermatozoa of three species of decapod crustaceans (Nephrops norvegicus L., Macrura; Eupagurus bernhardus L., Anomura; Carcinus maenas Penn., Brachyura). Their properties have been studied by cytochemical methods. Their position inside the capsule of the spermatozoon has been specified with the aid of the electron microscope. Present in a constant fashion in the three species cited, their relative importance is very variable. In contrast to the refringent cone of the spermatozoon of Ascaris, which contains an acid protein, ascaradine, the capsule of the spermatozoon of the three decapod crustaceans studied contains basic proteins which we propose to designate by the general term "decapodine".     

Ultrastructure of the spermatozoon of Centroderma spinosissima (Stossich, 1886) (Digenea: Mesometridae) and its phylogenetic potential

The Mesometridae includes only five genera and eight species. The available data on the ultrastructure of sperm cells of mesometrid species referred to two species only, Elstia stossichianum and Wardula capitellata. The present study revealed the ultrastructure of the spermatozoon of a third genus and third species of Mesometridae, Centroderma spinosissima. The mature spermatozoon of C. spinosissima presents two axonemes with different lengths of the Ehlers’ 9 + ‘1’ trepaxonematan pattern, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, a lateral expansion, spine-like bodies, cytoplasmic ornamented buttons and granules of glycogen. The spermatozoon of C. spinosissima is similar to those of the previously studied mesometrids. However, some peculiarities such as the presence of two mitochondria, the disposition of the external ornamentation of the plasma membrane and the morphology of the posterior spermatozoon extremity, characterize the male gamete of C. spinosissima. Moreover, the presence of cytoplasmic ornamented buttons is a characteristic found only in the mature spermatozoon of mesometrids and it probably represents an autapomorphy for this family.     

Secondary structure of chorion proteins of the Lepidoptera Pericallia ricini and Ariadne merione by ATR FT-IR and micro-Raman spectroscopy

The gross morphological features of the eggs and eggshells (chorions) of two Lepidoptera species, Pericallia ricini and Ariadne merione were revealed for the first time by scanning and transmission electron microscopy. These two insect pests are extremely serious threats for many crops, mainly in India, but also in several other regions of the world. Micro-Raman and ATR FT-IR spectroscopy were also applied to study in detail the secondary structure of the eggshell (chorion) proteins of these Lepidoptera species. Both techniques indicate that the two species have nearly identical conformations of their chorion proteins with abundant antiparallel β-pleated sheet. These results are in support of our previous findings that the helicoidal architecture of the proteinaceous chorion of Lepidoptera and fishes is dictated by a common molecular denominator, the antiparallel β-pleated sheet secondary structure.     

Specific protein synthesis in cellular differentiation: V. A secretory defect of chorion formation in the Grcol mutant of Bombyx mori

When homozygous, the Gr^col mutation of Bombyx mori causes the production of an eggshell in which most proteins are underrepresented to varying degrees. Neither the relative rates nor the timing of chorion protein synthesis appear to be affected; instead, the mutant phenotype results from the post-translational loss of normally synthesized proteins. The extent of loss of each protein correlates with its developmental timing, being maximal at early to middle stages. At the same stages, secretion appears to be deficient: chorion proteins overaccumulate within mutant cells, and slowly disappear. A preliminary electron microscopic examination has revealed the presence of mutant-specific cytoplasmic vesicles. The deficient complement of secreted proteins fails to form the highly ordered structure characteristic of normal chorion.