Sperm storage in male elasmobranchs: A description and survey

Two basic types of spermatozoan aggregates, spermatophores and spermatozeugmata, found in 14 different species of sharks, one species of skate, and one species of chimaera (holocephalan), were investigated using light and scanning electron microscopy. Spermatophores, aggregates (usually 1,000–6,000 μm in diameter and larger) of randomly clumped sperm embedded in and surrounded by an eosinophilic matrix, were found in Alopias superciliosus, Odontaspis taurus, Carcharodon carcharias, Isurus oxyrinchus, and Lamna nasus. Three types of spermatozeugmata, sperm structures without a surrounding capsule or matrix, are described. The first, clumps of 60–200 sperm unbound in a supporting matrix, are found in Squalus acanthias and Hydrolagus colliei. In the second type, single-layered spheres are formed of sperm clumps with the sperm heads bound in a common supporting matrix. These are found in Carcharhinus limbatus and Carcharhinus plumbeus. The third type of spermatozeugmata are large multilayered, compound structures formed by the accretion of several single-layered aggregates. These multilayered structures characteristically are found in Carcharhinus falciformis, C. limbatus, Carcharhinus obscurus, C. plumbeus, Carcharhinus porosus, Prionace gluaca, Rhizoprionodon terraenovae, and Sphyrna lewini. Sperm aggregates of all types are stored between the septa and in the lumen of the terminal ampulla of the epididymis. In their various forms they are the final product of the mature male elasmobranch reproductive tract. In a male with mature claspers, the presence of sperm aggregates is a more reliable indicator of maturity and sexual activity than is clasper condition alone. © 1994 Wiley-Liss, Inc.     

Catch composition and reproductive biology of whaler sharks (Carcharhiniformes: Carcharhinidae) caught by fisheries in Indonesia

The first detailed information on the biological aspects of members of the economically important shark family Carcharhinidae in Indonesian waters is given. Carcharhinids dominated the landings of sharks at sites visited, comprising almost 60% of the total biomass of all sharks recorded, over an intensive 5 year sampling period. A total of 26 species of carcharhinids, representing half of the species in the Carcharhinidae, were recorded. The most abundant species, in terms of numbers recorded, were Scoliodon laticaudus and Carcharhinus falciformis , while the most abundant in terms of biomass were Prionace glauca , C. falciformis and Carcharhinus obscurus . Biological data are presented for 22 of the 26 species. The total length at which males attain maturity ( L ₅₀) was determined for 10 species. The biological aspects of a number of species, most notably Carcharhinus sorrah and Loxodon macrorhinus , were found to differ from those recorded in the literature for other regions.     

Microsatellite Analyses of Blacktip Reef Sharks (Carcharhinus melanopterus) in a Fragmented Environment Show Structured Clusters

The population dynamics of shark species are generally poorly described because highly mobile marine life is challenging to investigate. Here we investigate the genetic population structure of the blacktip reef shark (Carcharhinus melanopterus) in French Polynesia. Five demes were sampled from five islands with different inter-island distances (50–1500 km). Whether dispersal occurs between islands frequently enough to prevent moderate genetic structure is unknown. We used 11 microsatellites loci from 165 individuals and a strong genetic structure was found among demes with both F-statistics and Bayesian approaches. This differentiation is correlated with the geographic distance between islands. It is likely that the genetic structure seen is the result of all or some combination of the following: low gene flow, time since divergence, small effective population sizes, and the standard issues with the extent to which mutation models actually fit reality. We suggest low levels of gene flow as at least a partial explanation of the level of genetic structure seen among the sampled blacktip demes. This explanation is consistent with the ecological traits of blacktip reef sharks, and that the suitable habitat for blacktips in French Polynesia is highly fragmented. Evidence for spatial genetic structure of the blacktip demes we studied highlights that similar species may have populations with as yet undetected or underestimated structure. Shark biology and the market for their fins make them highly vulnerable and many species are in rapid decline. Our results add weight to the case that total bans on shark fishing are a better conservation approach for sharks than marine protected area networks.     

Availability, morphometrics, feeding and breeding activity in a multi-species, demersal fish stock of the Western Indian Ocean

A multi-species demersal fish stock was studied from April 1969 to July 1970. The common species are described in this paper and consist of Carcharhinus sealei, Rhynchobatus djeddensis, Dasyatis kuhlii, Rachycentron canadum, Psettodes erumei and Arius sp. With the exception of Rachycentron canadum , these fish were available throughout the year and some coincidence of increased availability was noted in August/September. Psettodes erumei , the commonest fish caught, was most available in August/September, February/ March and June. The size and weight distribution of each of these fish is described. Morphometric results indicate that two fish, Dasyatis kuhlii and Psettodes erumei , exhibit sexual dimorphism, the females being larger and heavier than the males. Carcharhinus sealei, Rhynchobatus djeddensis and Rachycentron canadum have a nearly isometric growth exponent whereas Dasyatis kuhlii, Psettodes erumei and Arius sp. have an allometric growth exponent. All fish were carnivores, Rhynchobatus djeddensis, Rachycentron canadum and Arius sp. being primarily crustacean feeders, Dasyatis kuhlii feeding on polychaetes and crustaceans and Carcharhinus sealei and Psettodes erumei feeding mainly on fish. The increased number of all three bony fish noted in August/September (immediately prior to the short rains in October/November) is discussed in relation to feeding activity and the initiation of spawning activity. It is suggested that spawning in Psettodes erumei and Arius sp. is initiated in September, continuing possibly to February and then during the long rains (March/May) and the South East Monsoon the fish recover. It is also suggested that pregnant elasmobranchs may come inshore in greater numbers during the rains to give birth.     

The occurrence of black spots in the tongue sole, Cynoglossus browni Chabanaud, due to nematode eggs (Capillaria spinosa) previously described in the shark Carcharhinus mttberti Müller & Henle

The occurrence of black spots in fillets of the tongue sole, Cynoglossus browni , due to the occurrence of nematode eggs is reported. The eggs were found to be identical with Capillaria spinosa egg type previously described from the shark, Carcharhinus milberti . The presence of the capillarid eggs in the tongue sole is discussed as a new observation in relation to gaps in knowledge of the adult nematode and the biology of the shark.     

Ovarian and Uterine Grafts: (Section of Obstetrics and Gynæcology)

Recent experience has convinced the author of the value of ovarian grafting. He gives the histories of a number of women upon whom he made implants of their own ovarian tissue in the course of operations for double o?phorectomy. The subsequent state of these patients is contrasted with that of women after castration without grafting. When the uterus was left in position menstruation was re-established in over 80% of the grafted cases.The author and his co-workers maintain that the vitality of autogenous grafts of ovarian substance is enhanced by hormones produced by the uterine mucosa. He therefore advocates that grafts of uterus be made in conjunction with ovarian implants whenever possible. Experiments carried out on animals have proved the correctness of this opinion.The results of a series of cases of combined ovarian and uterine graftings are recorded, and the technique of uterine mucosa implants is described.     

Do sharks exhibit heterodonty by tooth position and over ontogeny? A comparison using elliptic Fourier analysis

Tooth morphology is often used to inform the feeding ecology of an organism as these structures are important to procure and process dietary resources. In sharks, differences in morphology may facilitate the capture and handling of prey with different physical properties. However, few studies have investigated differences in tooth morphology over ontogeny, throughout the jaws of a single species, or among species at multiple tooth positions. Bull (Carcharhinus leucas), blacktip (Carcharhinus limbatus), and bonnethead sharks (Sphyrna tiburo) are coastal predators that exhibit ontogenetic dietary shifts, but differ in their feeding ecologies. This study measured tooth morphology at six positions along the upper and lower jaws of each species using elliptic Fourier analysis to make comparisons within and among species over their ontogeny. Significant ontogenetic differences were detected at four of the six tooth positions in bull sharks, but only the posterior position on the lower jaw appeared to exhibit a functionally relevant shift in morphology. No ontogenetic changes in morphology were detected in blacktip or bonnethead sharks. Intraspecific comparisons found that most tooth positions significantly differed from one another across all species, but heterodonty was greatest in bull sharks. Additionally, interspecific comparisons found differences among all species at each tooth position except between bull and blacktip sharks at two positions. These morphological patterns within and among species may have implications for prey handling efficiency, as well as in providing insight for paleoichthyology studies and reevaluating heterodonty in sharks.     

Ampullary organs and electroreception in freshwater Carcharhinus leucas.

The ampulla of Lorenzini of juvenile Carcharhlinus leucas differ histologically from those previously described for other elasmobranchs. The wall of the ampullary canal consists of protruding hillock-shaped epidermal cells that appear to secrete large quantities of a mucopolysaccharide gel. The ampullary organs comprise a long canal sheathed in collagen terminating in an ampulla. Each ampulla contains six alveolar sacs, with each sac containing hundreds of receptor cells. The receptor cells are characteristic of others described for elasmobranchs being pear-shaped cells with a central nucleus and bearing a single kinocilium in the exposed apical region of the cell. The supportive cells differ from general elasmobranch ampullary histology in that some have an apical nucleus. These ampullary structures allow Carcharhinus leucas to detect and respond to artificial electrical fields. Carcharhinus leucas from freshwater habitats respond to electrical signals supplied in freshwater aquaria by abruptly turning towards low voltage stimuli (< or = 10 microA) and either swimming over or biting at the origin of the stimulus.     

Developing embryo and cyclic changes in the uterus of Peripatus (Macroperipatus) acacioi (Onychophora,Peripatidae)

Female reproductive tracts of the viviparous neo-tropical onychophoran Peripatus acacioi have been examined at different times throughout the year, and the altering relationship between the developing embryo and the uterus is described. Depending on her age and time of year, the female may have one or two generations of embryos within her uterus. The uterine wall consists of a thin outer epithelium and basal lamina, three layers of muscles, and a thick basal lamina beneath an inner epithelium lining the uterus lumen. These layers are consistent along the length of the uterus apart from the inner epithelial lining, which varies according to position in the uterus and the developmental stage of embryos contained in the uterus. Early embryos are positioned along the length of the uterus and therefore have space in which to grow. During cleavage and segment formation, each embryo is contained within a fluid-filled embryo cavity that increases in size as the embryo grows. Morulae and blastulae are separated by lengths of empty uterus in which the epithelial lining appears vacuolated. Until the process of segment formation is complete, the embryos are attached to a placenta by a stalk and remain in the same part of the upper region of the uterus. As these embryos grow, the lengths of vacuolated cell-lined uterus between them decrease. Each embryo cavity is surrounded by the epithelial sac, the maternal uterine epithelium, which becomes overlaid by a thin layer of cells, the embryo sac, which is believed to be of embryonic origin. The placenta is a syncytial modification of the epithelial sac located at the ovarian end of each embryo cavity covered by the embryo sac and is analogous to the mammalian noninvasive epitheliochorial placenta. Segment-forming embryos have their heads directed toward the ovary. As the embryo gets longer during segment formation, its posture changes from coiled to flexed. Once segment formation is complete, the embryo loses contact with its stalk, an embryonic cuticle forms, and the embryo turns around so that its head is directed toward the vagina. The embryo escapes from its embryo sac and moves to the lower part of the uterus. In the lower part of the uterus, the straightened fetuses are first unpigmented but subsequently become pigmented as the secondary papillae on the body surface form and an adult-type cuticle forms beneath the embryonic cuticle. While the embryos are contained within their embryo cavities, nutrients are supplied by the placenta. Throughout development the mouth is open and in the mature fetus the gut is lined by peritrophic membrane and material is present in the gut lumen. Trachea have been observed only in fetuses that were ready for birth. Insemination, cyclical changes in the uterine epithelium, and the nature of the cuticle shed at parturition are discussed. © 1995 Wiley-Liss, Inc.     

The differentiation of the decidua and the distribution of metrial gland cells in the pregnant mouse uterus

Summary A study was made with the light microscope of the cellular changes involved in the formation of the decidua in the pregnant mouse uterus up to day 11 of pregnancy. The differentiation sequence was similar to that found by previous workers but the morphology and development of the basal zone is described in more detail. In addition, the morphology of glycogen rich cells in an area termed the lateral decidual zone is described. The distribution of granulated metrial gland cells and their precursors is described. These cells are first found in the uterine stroma before the blastocyst has implanted. Later they occur in the decidua and in the circular smooth muscle zone beneath the mesometrial triangle prior to the formation of the metrial gland. Granulated metrial gland cells are also found in the maternal blood spaces of the implantation site.     

Binding Proteins from Animals with Possible Transport Function

Several proteins from various animal tissues with possible transport function have been briefly described, with emphasis given to a vitamin D-induced calcium-binding protein (CaBP) implicated in calcium translocation across epithelial membranes. The latter protein was shown to be present in the small intestine, colon, kidney, and the uterus (shell gland) of the chicken. CaBP was also found in the small intestine of the rat, dog, bovine, and monkey. This protein has been isolated in high purity from chick intestinal mucosa and some of its properties determined. Its molecular weight is about 28,000, its formation constant, about 2.6 x 10⁵ M^-1, and its binding capacity, 1 calcium atom per protein molecule. Correlative studies have shown that CaBP concentration in intestinal mucosa varies with the calcium absorptive capacity of the gut, thereby suggesting that CaBP is intimately involved in the process of calcium absorption. CaBP has been localized in the brush border region of the intestinal absorptive cell and within goblet cells. Among other proteins mentioned were the intrinsic factor required for vitamin B₁₂ absorption and the protein(s) associated with iron translocation.     

The storage of spermatozoa in the oviducal glands of western North Atlantic sharks

Synopsis Spermatozoa stored in oviducal glands of sharks sampled off the North American east coast were revealed by viewing stained tissue sections using light microscopy. Of eleven species surveyed, sperm were found in nine:Alopias vulpinus, Lamna nasus, Carcharhinus obscurus, Carcharhinus plumbeus, Galeocerdo cuvieri, Prionace glauca, Rhizoprionodon terraenovae, Sphyrna lewini andSphyrna tiburo. Three insemination patterns are proposed to account for differences noted in these findings: (1) non-storage/immediate insemination for sharks such asLamna nasus; (2) short-term storage/delayed insemination as found in sharks in which ovulation is prolonged over weeks or months such asRhizoprionodon terraenovae, and (3) long-term storage/repeated insemination, a characteristic of nomadic sharks such asPrionace glauca andCarcharhinus obscurus which can store sperm in specialized tubules for months to years.     

Morphological characteristics of the uterus and uterine cervix of the plains viscacha (Lagostomus maximus)

The plains viscacha is a hystricognathi rodent with special reproductive characteristics. Despite poly-ovulation of 800 oocytes, it generates a high embryonic mortality since from 10 to 12 implantations only one or two offspring are born. The present work analyses the morphological, morphometrical, histochemical and lectinhistochemical characteristics of the uterus and uterine cervix of pregnant and non-pregnant viscacha. Anatomically, the uterus has two horns each one continued with a short cervix devoid of glands. The structure of the uterus is like that of other species; however, the proportion and size of its glands varies according to the physiological state. In viscacha, there is no uterine body and cervices cannot be differentiated externally. The formation of two sack bottoms is determined by the presence of a middle raphe in the cranial portion of the vagina. The so-described anatomy is different from that described in other hystricognathi such as guinea pig and coypu. The cervix presents two microscopically differentiable regions: the endocervix and the ectocervix lined by epithelia with different characteristics. The general characteristics of the uterus of L. maximus do not show specific differences with those of other mammals that might explain its peculiar gestation.     

Comparison of the reproductive ecology of two sympatric blacktip sharks (Carcharhinus limbatus and Carcharhinus tilstoni) off north-eastern Australia with species identification inferred from vertebral counts

Precaudal vertebral counts were used to distinguish between 237 morphologically similar Carcharhinus limbatus and Carcharhinus tilstoni and were congruent with differences in reproductive ecology between the species. In addition to differing lengths at maturity and adult body size, the two species had asynchronous parturition, were born at different sizes and the relative frequencies of neonates differed in two coastal nursery areas. Despite evidence that hybridization can occur, these differences suggest the species are largely reproductively isolated.     

Isolation and characterization of five dinucleotide microsatellite loci in the sandbar shark,Carcharhinus plumbeus

Five dinucleotide markers were isolated and optimized from a microsatellite‐enriched genomic library obtained from the sandbar shark, Carcharhinus plumbeus. Genotypic distributions of all markers were found to be in conformance with the expectations of Hardy–Weinberg equilibrium with four to 39 alleles present per locus. We amplified these loci in two female sharks and their litters. A maternal allele was recovered at each locus in all progeny indicating reliable amplification. More than two paternal alleles were recovered across both litters indicating genetic polyandry. Additionally, these markers were amplified across 10 carcharhiniform species to examine their utility in other studies.     

A high-affinity cytosol binding protein for 1 alpha,25-dihydroxycholecalciferol in the uterus of Japanese quail.

Cytosol fractions prepared from the uterine mucosa of egg-laying Japanese Quail were analysed for binding of the metabolites of cholecalciferol. When the uterus was incubated at 37 degrees C with various radioactive metabolites of cholecalciferol, the nuclear fraction incorporated only 1 alpha,25-dihydroxy[3H]cholecalciferol. When the uterus was incubated at 0 degree C with 1 alpha,25-dihydroxy[3H]cholecalciferol, most of the radioactivity was found in the cytosol. Translocation of 1 alpha,25-dihydroxy[3H]cholecalciferol from the cytosol to the nucleus was temperature-dependent. The addition of 100-fold excess amounts of unlabelled 1 alpha-25-dihydroxycholecalciferol significantly diminished the nuclear binding of 1 alpha,25-dihydroxy[3H]cholecalciferol. The cytosol fraction contained a 3.5 S macromolecule that specifically binds 1 alpha,25-dihydroxy[3H]cholecalciferol. The dissociation constant was 0.39 nM and the maximal binding was 55 fmol/mg of protein. These results strongly suggest that the uterus in egg-laying birds is a target organ or 1 alpha,25-dihydroxycholecalciferol.     

Ecological Drivers of Shark Distributions along a Tropical Coastline

As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience.     

Enzymatic and immunological evidence for two forms of carnosinase in the mouse.

Carnosinase (aminoacyl-L-histidine hydrolase, EC 3.4.13.3) hydrolyzes the dipeptide carnosine (beta-alanyl-L-histidine), which is thought to play a role in cerebral and skeletal muscular function and has been implicated as a neuroaffector in the olfactory bulb. Carnosinase activity is present in many tissues of the mouse including heart, liver and lung, but it is most active in kidney, uterus and nasal olfactory mucosa. Kinetic measurements with 1H-NMR spectroscopy indicate that the enzyme is stereospecific and can hydrolyze L-but not D-carnosine. Anserine is a poorer substrate, while homocarnosine is essentially a non-substrate. However, these two dipeptides are effective inhibitors of the hydrolysis of L-carnosine. Carnosinase activity is unaffected when assayed in 2H2O at 99% isotopic purity. From considerations of the effect of Mn2+ on (1) substrate concentration velocity curves; (2) thermostability, and (3) inhibitor behavior, tissues with carnosinase can be divided into two groups. Kidney, uterus and olfactory mucosa represent one group, while central nervous system, muscle, spleen, etc. represent the second. The validity of this classification is confirmed by immunological evidence. Antiserum prepared against carnosinase purified from kidney cross-reacts with and inhibits the activity of olfactory mucosa, kidney and uterus but not that from central nervous system, heart or liver.