Christian Lipke - Induzierte Spermiation und Spermienmorphologie bei dem Goldbaumsteigerfrosch, Dendrobates auratus
Die induzierte Spermiation wird bei Amphibien fast ausschließlich durchgeführt, um endokrine Zusammenhänge zu untersuchen, nur selten steht der Artenschutz im Vordergrund. Ein Nachweis der Anwendbarkeit der hormonell induzierten Spermiation bei Baumsteigerfröschen nach Applikation von humanem Choriongonadotropin (hCG) sowie spermatologische Untersuchungen einschließlich lichtmikroskopischer, fluoreszenzmikroskopischer und elektronenmikroskopischer Studien stehen noch aus.
Vor dem Hintergrund des weltweiten Amphibiensterbens wurden zu den Arbeiten, welche Gründe der massiven Verluste zu klären versuchten, alternative reproduktionsbiologische Studien durchgeführt. Es wurden Unterschiede bei der induzierten Spermienabgabe des Goldbaumsteigerfrosches, Dendrobates auratus, zwischen 5 min und 240 min nach der Injektion von hCG in den dorsalen Lymphsack charakterisiert. Darüber hinaus wurden zwei Medien, eine isotonische phosphatfreie Kochsalzlösung sowie ein „Xenopus fertilization“ Medium (XB) hinsichtlich ihrer Fähigkeit, die Motilität abgegebener Spermien zu gewährleisten, untersucht. Die Beschreibung der Spermienmorphologie erfolgte mit licht- sowie transmissionselektronen- und rasterelektronenmikroskopischen Verfahren. Dazu wurde eine Methode zur elektronenmikroskopischen Probenaufarbeitung für niedrig konzentrierte Einzel-Zellen etabliert. Die Membranintegrität der Spermatozoen wurde anhand des Färbeverhaltens mit Propidiumjodid (PI) sowie der Morphologie der äußeren Zellmembran im Lichtmikroskop untersucht. Neben typisch geformten Zellen wurden auch pathologische Spermienformen quantifiziert und in vier Gruppen eingeteilt: (1) großer Zytoplasmatropfen; (2) unreife Rundzelle; (3) Kopfdefekt mit Schädigung der Zytoplasmamembran; (4) Schwanzdefekt.
Die effektivste Gewinnung von Spermien bei D. auratus (96,9 %) konnte nach doppelter Stimulation mit jeweils 100 IE hCG im Abstand von einer Stunde erreicht werden. Unter Verwendung des XB Mediums wurden signifikant höhere absolute (P<0,05) und relative (P<0,001) Anzahlen motiler Spermien aus den Kloaken
hormonell behandelter Frösche gewonnen als unter Verwendung des IPS Mediums.
Die Mehrzahl der Spermatozoen wies eine typische Morphologie und Viabilität auf (79,3 %). Diese Zellen (Gesamtlänge: 56,1 ± 5,5 µm) bestehen aus einem gebogenen, filiformen Kopfstück sowie einem einzelnen Spermienschwanz ohne akzessorische Strukturen. Für die ultrastrukturellen Untersuchungen wurden die Spermienproben auf Objektträger gegeben und mit Karnovksy-Lösung fixiert. Auf diese Weise konnte eine praktische Handhabung für die weiteren Vorbereitungsschritte der Elektronenmikroskopie von Einzelzell-Proben in nur geringer Konzentration erreicht werden. Bei den ultrastrukturellen Studien wurden die für Spermien der Dendrobaten typischen Strukturen (akrosomaler Komplex bestehend aus akrosomalem Vesikel und subakrosomalem Konus, nukleäre Inklusionen aus granulärem Material, kurzes Mittelstück mit proximaler und distaler Zentriole) gefunden. Allerdings konnte mit D. auratus der erste Vertreter der Baumsteigerfrösche beschrieben werden, dessen Spermien-Flagellae lediglich aus einem Axonem ohne undulierende Membran bestehen. Die Ergebnisse deuten außerdem auf eine Korrelation zwischen morphologischen Veränderungen der äußeren Zellmembran gewonnener Spermatozoen und dem PI Färbeverhalten hin.
Zellen, die lichtmikroskopisch zahlreiche blasige Auftreibungen im Kopfbereich besaßen, konnten mit Hilfe der PI Färbung als membrandefekt identifiziert werden.
Die kontrollierte und schonende Spermiengewinnung beim Baumsteigerfrosch in vivo bietet, verbunden mit der Möglichkeit spermatologischer Untersuchungen, die Voraussetzungen für assistierte Zuchtprogramme, mit denen auf das weltweite Amphibiensterben reagiert werden kann. Assistierte Paarung, künstliche Befruchtung und Konservierung von Gameten und Embryonen stellen mögliche Anwendungen innerhalb solcher Projekte dar. Die Durchführung der induzierten Spermiation im Rahmen der tierärztlichen Praxis kann sich bei der Geschlechtsbestimmung solcher Amphibienarten als sinnvoll herausstellen, die keinen äußerlich erkennbaren Geschlechtsdimorphismus aufweisen. Eine genauere Diagnostik der männlichen Infertilität wird ebenfalls ermöglicht. Die Entdeckung einer bislang einzigartigen Struktur des Spermienschwanzes bei einem Baumsteigerfrosch weist nicht nur auf eine Heterogenität dieses Merkmals auf Familienniveau hin, sondern kann
gemeinsam mit Verhaltensbeobachtungen, Studien zur äußeren Morphologie und molekularbiologischen Methoden dazu beitragen, die Phylogenie der Amphibien zu klären.
Chapter 7 References
AGUIAR-JR., O., A.A. GARDA, A.P. LIMA, G.R. COLLI, S.N. BÁO and S.M. RECCO-PIMENTEL (2003):
Biflagellate spermatozoon of the poison-dart frogs Epipedobates femoralis and Colostethus sp. (Anura, Dendrobatidae).
J. Morphol. 255, 114-121
AGUIAR-JR., O., A.P. LIMA, S.N. BÁO and S.M. RECCO-PIMENTEL (2004):
Sperm ultrastructure of the Brazilian Amazon poison frogs Epipedobates trivittatus and Epipedobates hahneli (Anura, Dendrobatidae).
Acta Zool. 85, 21-28
ALFORD, R.A., P.M. DIXON and J.H.K. PECHMANN (2001):
Global amphibian population declines.
Nature 414, 449-500
ALFORD, R.A. and S.J. RICHARDS (1999):
Global amphibian declines: a problem in applied ecology.
Annu. Rev. Ecol. Syst. 30, 133-165
AMARAL, M.J.L.V., A.P. FERNANDES, S.N. BÁO and S.M. RECCO-PIMENTEL (1999):
An ultrastructural study of spermiogenesis in three species of Physalaemus (Anura, Leptodactylidae).
Biocell 23, 211-221
AMARAL, M.J.L.V., A.P. FERNANDES, S.N. BÁO and S.M. RECCO-PIMENTEL (2000):
The ultrastructure of spermatozoa in Pseudopaludicola falcipes (Anura, Leptodactylidae).
Amphibia-Reptilia 21, 498-502.
ANKLEY, G.T., S.A. DIAMOND, J.E. TIETGE, G.W. HOLCOMB, K.M. JENSEN, D.L.
DEFOE and R. PETERSON (2002):
Assessment of the risk of solar ultraviolet radiation to amphibians. 1. Dose-dependent induction of hindlimb malformations in the northern leopard frog.
Environ. Toxicol. Chem. 17, 2530-2542
BÁO, S.N., G.C. DALTON and S.F. OLIVEIRA (1991):
Spermiogenesis in Odontophrynus cultripes (Amphibia, Anura, Leptodactylidae):
Ultrastructural and cytochemical studies of proteins using E-PTA.
J. Morphol. 297, 303-314
BARTON, H.L. and S.L. GUTTMAN (1972):
Low temperature preservation of toad spermatozoa (Genus Bufo).
Texan. J. Sci. 23, 363-370
BELDEN, L.K., E.L. WILDY and A.R. BLAUSTEIN (2000):
Growth, survival, and behaviour of larval longtoed salamanders (Ambystoma macrodactylum) exposed to ambient levels of UV-B radiation.
J. Zool. London 251, 473-479
BERGER L., R. SPEARE, P. DASZAK, D.E. GREEN, A.A. CUNNINGHAM, C.L.
GOGGIN, R. SLOCOMBE, M.A. RAGAN, A.D. HYATT, K.R. MCDONALD, H.B.
HINES, K.R. LIPS, G. MARANTELLI and H. PARKES (1998):
Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America.
Proc. Natl. Acad. Sci. USA 95(15), 9031-9036
BERNARDINI, G., R. STIPANI and G. MELONE (1986):
The ultrastructure of Xenopus spermatozoon.
J. Ultrastruct. Mol. Struct. Res. 94, 188-194
BIRKHAHN, H., V. KÜLPMANN and K. WASSMANN (1994):
Zur Variabilität des Goldbaumsteigers.
Aquar. Terrar. Zeitschr. 47 (9), 570-576
BLAUSTEIN, A.R., L.K. BELDEN, A.C. HATCH, L.B. KATS, P.D. HOFFMAN, J.B.
HAYS, A. MARCO, D.P. CHIVERS and J.M. KIESECKER (2001):
Ultraviolet radiation and amphibians. In: C.S. Cockell, A.R Blaustein, (Eds.), Ecosystems, evolution and ultraviolet radiation.
Springer, New York, USA, pp. 63-79
BLAUSTEIN, A.R. and J.M. KIESECKER (2002):
Complexity in conservation: lessons from global decline of amphibian populations.
Ecol. Letters 5, 597-608
BLAUSTEIN, A.R., J.M. KIESECKER, D.P. CHIVERS, D.G. HOKIT, A. MARCO, L.K.
BELDEN and A. HATCH (1998):
Effects of ultraviolet radiation on amphibians: field experiments.
Am. Zool. 38, 799-812
BLAUSTEIN, A.R., J.M. ROMANSIC, J.M. KIESECKER and A.C. HATCH (2003):
Ultraviolet radiation, toxic chemicals and amphibian declines.
Div. Distrib. 9, 123-140
BLAUSTEIN, A.R., D.B. WAKE and W.P. SOUSA (1994):
Amphibian declines: Judging stability, persistence, and susceptibility of populations to local and global extinctions.
Conserv. Biol. 8, 60-71
BOGART, J.P. (1991):
The influence of life history on karyotypic evolution in frogs. In: Green, D.M., Sessions, S.K., (Eds.), Amphibian cytogenetics and evolution.
Academic Press, San Diego, USA, pp. 233-255
BOLÍVAR, W., F. CASTRO, and S. LÖTTERS (2004):
Dendrobates lehmanni. In: IUCN 2007. 2007 IUCN Red List of Threatened Species.
<www.iucnredlist.org>. Downloaded on 14 May 2008.
BOONE, M.D. and C.M. BRIDGES (2003):
The problem of pesticides: implications for amphibian populations. In: Semlitsch, R.D. (ed.), Amphibian conservation.
Smithsonian Institution Press, Washington, D.C., USA
BRADFORD, D.F. (1991):
Mass mortality and extinction in a high-elevation population of Rana muscosa.
J. Herpetol. 25, 174-177
BRADFORD, D.F., D.M. GRABER and F. TABATABAI (1994):
Population declines of the native frog, Rana muscosa, in Sequoia and Kings Canyon National Parks, California.
Southwestern Naturalist 39, 323-327
BRADFORD, D.F., F. TABATABAI and D.M. GRABER (1993):
Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.
Conserv. Biol. 7, 882–888
BRIGGS, R. and T.J. KING (1952):
Transplantation of living nuclei from blastula cells into enucleated frogs’ eggs.
Zoology 38, 455-463
BRIGGS, C.J, V.T. VREDENBURG, R.A. KNAPP and L.J. RACHOWICZ (2005):
Investigating the population-level effects of chytridiomycosis, an emerging infectious disease of amphibians.
Ecology 86, 3149-3159
BRÖNMARK, C. and P. EDENHAMN (1994):
Does the presence of fish affect the distribution of tree frogs (Hyla arborea)?
Conserv. Biol. 8, 841-845
BROWNE, R.K., J. CLULOW and M. MAHONY (2001):
Short-term storage of cane toad (Bufo marinus) gametes.
Reproduction 121, 167-173
BROWNE, R.K., J. CLULOW and M. MAHONY (2002a):
The short-term storage and cryopreservation of spermatozoa from hylid and myobatrachid frogs.
Cryo Letters 23, 129-136
BROWNE, R.K., J. CLULOW, M. MAHONY and A. CLARK (1998):
Successful recovery of motility and fertility of cryopreserved cane toad (Bufo marinus) sperm.
Cryobiology 37(4), 339-345.
BROWNE, R.K., J. DAVIS, M. POMERING and J. CLULOW (2002b):
Storage of cane toad (Bufo marinus) sperm for 6 days at 0°C with subsequent cryopreservation.
Reprod. Fertil. Dev. 14, 267-273
BROWNE, R.K., J. SERATT, C. VANCE and A. KOUBA (2006):
Hormonal priming, induction of ovulation and in-vitro fertilization of the endangered Wyoming toad (Bufo baxteri).
Reprod. Biol. Endocrinol. 4(34): 1-11
BRUN, R. (1975):
Oocyte maturation in vitro: Contribution of the oviduct to total maturation in Xenopus laevis.
Experimentia 31, 1275-1276
BURGOS, M.H. and D.W. FAWCETT (1956):
An electron microscope study of spermatid differentiation in the toad Bufo arenum Hensell.
J. Biophys. Biochem. Cytol. 2, 223-240
BURGOS, M.H. and A.J. LADMAN (1955):
Effect of purified gonadotropins upon release of spermatozoa in the frog, Rana pipiens.
Proc. Soc. Exp. Biol. Med. 88(3), 484-487
BURGOS, M.H. and R. VITALE-CALPE (1967):
The mechanism of spermiation in the toad.
Am. J. Anat. 120, 227-252
CAMPANELLA C., R. CAROTENUTO, V. INFANTE, G. MATURI and U. ATRIPALDI (1997):
Sperm-egg interaction in the painted frog (Discoglossus pictus): an ultrastructural study.
Mol. Reprod. Dev. 47(3), 323-333
CAREY,C.and M.A. ALEXANDER (2003):
Climate change and amphibian declines: is there a link?
Div. Distr. 9(2), 111-121
CAREY, C., D.F. BRADFORD, J.L. BRUNER, J.P.COLLINS, E.W. DAVIDSON, J.E.
LONGCORE, M. OUELLET, A.P. PESSIER and D.M. SCHOCK (2003):
Biotic factors in amphibian population declines. In: C. Linder, S.K. Krest, and D.W.
Sparling (eds.). Amphibian decline: An integrated analysis of multiple stressor effects.
SETAC Press, Boca Raton, Florida, USA
CHATTERJEE, A., S. BHADURI and A.K. BASUMALLIK (1971):
The ability of hCG in the induction of spermiation in toads devoid of an endogenous source of gonadotropin.
Endokrinologie, 58(1), 119-120
CHEN, T.H., J.A. GROSS and W.H. KARASOV (2006):
Sublethal effects of lead on northern leopard frog (Rana pipiens) tadpoles.
Environ. Toxicol. Chem. 25(5), 1383-1389
CLOUGH, M. and K. SUMMERS (2000):
Phylogenetic systematics and biogeography of the poison frogs: evidence from mitochondrial DNA sequences.
Biol. J. Linnean Soc. 70, 515-540
COCKELL, C.S and A.R. BLAUSTEIN (2000):
Ultraviolet spring and the ecological consequences of catastrophic impacts.
Ecology Letters 3, 77-81
COCKELL, C.S and A.R. BLAUSTEIN (2001):
Ecosystems, evolution and ultraviolet radiation.
Springer, New York, USA
COLLINS, J.P., N. COHEN, E.W. DAVIDSON, J.E. LONGCORE and A. STORFER (2003):
Global amphibian declines: an interdisciplinary research challenge for the 21st century. In: M.J. Lannoo (ed.). Status and conservation of U.S. amphibians, Vol. 1.
Conservation essays.
University of California Press, Berkeley, USA, pp. 43-52
COLLINS, J.P., T.R. JONES and H.A. BERNA (1988):
Conserving genetically distinctive populations: the case of the Huachua tiger salamander (Ambystoma tigrinum stebbinsi). In: R.C. Szaro, K.C. Severson, and D.R. Patton (eds.). Management of amphibians, reptiles, and small mammals in North America.
USDA Forest Service GTR-RM-166, Rocky Mountain Forest and Range Experiment Station, Fort Collins, USA, pp. 45-53
COLLINS, J.P. and A. STORFER (2003):
Global amphibian declines: sorting the hypotheses.
Divers. Distrib. 9, 89-98
COLOMA, L.A. and S. Ron (2004):
Dendrobates abditus. In: IUCN 2007. 2007 IUCN Red List of Threatened Species.
<www.iucnredlist.org> Downloaded on 14 May 2008.
CORY, L. (1963):
Effects of introduced trout on the evolution of native frogs in the high Sierra Nevada Mountains.
Proc. Int. Congress Zool. 16, 172
DALY, J. W., S. I. SECUNDA, H. M. GARRAFTO, T. F. SPANDE, A. WISNIEWSKI, C. NISHIHIRA and J. F. COVER JR. (1992):
Variability in alkaloid profiles in neotropical Poison Frogs (Dendrobatidae): Genetic versus environmental determinants.
Toxicon 30 (8), 887-898
DASZAK, P., A.A. CUNNINGHAM and A.D HYATT (2000):
Emerging infectious diseases of wildlife-threats to biodiversity and human health.
Science 287, 443-449
DASZAK, P., A.A. CUNNINGHAM and A.D HYATT (2003):
Infectious disease and amphibian population declines.
Div. Distrib. 9(2), 141-150
DAVIDSON, C., H.B. SHAFFER and M.R. JENNINGS (2001):
Declines of the California red-legged frog: climate, UV-B, habitat, and pesticides hypotheses.
Ecol. Appl. 11, 464-479
DEL PINO, E.M. (1973):
Interactions between gametes and environment in the toad Xenopus laevis (Daudin) and their relationship to fertilization.
J. Exp. Zool. 185, 121-132
DE SÁ, R.O. and D.M. HILLIS (1990):
Phylogenetic relationships of the pipid frogs Xenopus and Silurana: An integration of ribosomal DNA and morphology.
Mol. Biol. Evol. 7, 365-376
DIBERARDINO , A. (1962):
The karyotype of Rana pipiens and investigation of its stability during embryonic differentiation.
Dev. Biol. 5, 101-126
DIBERARDINO, M.A., N. HOFFNER ORR and R.G. MCKINNELL (1986):
Feeding tadpoles cloned from Rana erythrocyte nuclei.
Proc. Natl. Acad. Sci. USA 83(21), 8231-8234
DICKERSON, K. (1999):
Pesticides and the Wyoming toad. In: Bender, M., Balis-Larsen, M. (Eds.), U.S. Fish
& Wildlife Service Endangered Species Bulletin, vol. 24 USFWS, Washington, USA, pp. 20-21
DUELLMAN, W.E. and L. TRUEB (1986):
Biology of amphibians.
McGraw-Hill, New York, USA
DUNN, E. R. (1941):
Notes on Dendrobates auratus.
Copeia 2, 88-93
EASLEY, K.A., D.D. CULLEY JR., N.D. HORSEMAN and J.E. PENKALA (1979):
Environmental influences on hormonally induced spermiation of the bullfrog, Rana catesbeiana.
J. Exp. Zool. 207, 407-416
EATON, T. H. Jr. (1941):
Notes on the life history of Dendrobates auratus.
Copeia 2, 93-95
EDWARDS, D.L., M.J. MAHONY and J. CLULOW(2004):
Effects of sperm concentration, medium osmolality and oocyte storage on artificial fertilisation success in a myobatrachid frog, Limnodynastes tasmaniensis.
Reprod. Fertil. Dev. 16, 347-354
ELINSON, R.P. (1973):
Fertilization of frog body cavity eggs enhanced by treatments affecting the vitelline coat.
J. Exp. Zool. 183, 291-302
FERNANDEZ, M. and J. L´HARIDON (1992):
Influence of lighting conditions on toxicity and genotoxicity of various PAH in the newt in vitro.
Mutation Research 298, 31-41
FERNANDEZ, M. and J. L´HARIDON (1994):
Effects of light on the cytotoxicity and genotoxicity of benzo(a)pyrene and an oil refinery effluent in the newt.
Environ. Mol. Mutagen 24, 124-136
FILHO, O.P.R., S.L. LIMA, D.R. DE ANDRADE and J.T. DE SEIXAS FILHO (1998):
Study of Bull-Frog spawning, Rana catesbeiana, using induced reproduction.
R. Bras. Zootec 27(2), 216-223
FITE, K.V., A.R. BLAUSTEIN, L. BENGSTON and H.E. HEWITT (1998):
Evidence of retinal light damage in Rana cascadae: a declining amphibian species.
Copeia 1998, 906-914
FORD, L.S. (1993):
The phylogenetic position of the dart-poison frogs (Dendrobatidae) among anurans - An examination of the competing hypotheses and their characters.
Ethol. Ecol. Evol. 5, 219-231
FORD, L.S. and D.C. CANNATELLA (1993):
The major clades of frogs.
Herpetol. Monogr. 7, 94-117
FORTUNE, J.E., P.W. CONCANNON, W. HANSEL (1975):
Ovarian progesterone levels during in vitro oocyte maturation and ovulation in Xenopus laevis.
Biol. Reprod. 13, 561-567
FREDA, J. (1991):
The effects of aluminum and other metals on amphibians.
Environ. Pollut. 71, 305-328.
FREDA, J., V. CAVDEK and D. MCDONALDS (1990):
Role of organic complexation in the toxicity of aluminium to Rana pipiens embryos and Bufo americanus tadpoles.
Can. J. Fisheries Aquatic Sci. 47, 217-224
FROST, D.R. (2007):
Amphibian species of the world: an online reference. Version 5.1 (10 October, 2007).
Electronic database accessible at
http://research.amnh.org/herpetology/amphibia/index.php.
Am. Mus. Nat. Hist., New York, USA.
GAMRADT, S.C. and L.B. KATS (1996):
Effect of introduced crayfish and mosquitofish on California newts.
Conserv. Biol. 10, 1155-1162
GALLANT, A.L., R.W. KLAVER, G.S. CASPER and M.J. LANNOO (2007):
Global rates of habitat loss and implications for amphibian conservation.
Copeia 4, 967-979
GALLI-MAININI, C. (1947):
Pregnancy test using the male toad.
J. Clin. Endocrinol. 7, 653-658
GARDA, A.A., G.R. COLLI, O., AGUIAR-JR., S.M. RECCO-PIMENTEL and S.N.
BÁO (2002):
The ultrastructure of the spermatozoa of Epipedobates flavopictus (Amphibia, Anura, Dendrobatidae), with comments on its evolutionary significance.
Tissue Cell 34, 356-364
GARRIDO, O., E. PUGIN and B. JORQUERA (1989):
Sperm morphology of Batrachyla (Anura: Leptodactylidae).
Amphibia-Reptilia 10, 141-149
GILLESPIE, G.R. (2001):
The role of introduced trout in the decline of the spotted tree frog (Litoria spenceri) in southeastern Australia.
Biol. Conserv. 100, 187-198
GIRARD, C. (1855):
Abstract of a report to Lieut. J.M. Gillis, U.S.N., upon the reptiles collected during U.S.N. astronomical expedition to Chili.
Proc. Acad. Nat. Sci. Phil 7, 226-227.
GOODSELL, J.A. and L.B. KATS (1999):
Effect of introduced mosquitofish on Pacific treefrogs and the role of alternative prey.
Conserv. Biol. 13, 921-924
GRANT, T., D.R. FROST, J.P. CALDWELL, R. GAGLIARDO, C.F.B. HADDAD, P.J.R. KOK, D.B. MEANS, B.P. NOONAN, W.E. SCHARGEL and W.C. WHEELER (2006):
Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia:
Athesphatanura: Dendrobatidae).
Bull. Am. Mus. Nat. Hist. 299, 1-262
GURDON, J.B. and J.A. BYRNE (2003):
The first half-century of nuclear transplantation.
Proc. Natl. Acad. Sci. USA 100(14), 8048-8052
GURDON, J.B. and V. UEHLINGER (1966):
"Fertile" intestine nuclei.
Nature 210, 1240-1241
HALL, R.J. and B.M. MULHERN (1984):
Are anuran amphibians heavy metal accumulators? In: Seigel, R.A., Hunt, L.E., Knight, J.L., Malaret, L.,Zuschlag, N.L. (Eds.), Vertebrate Ecology and Systematics - A Tribute to Henry S. Fitch
Mus. Nat. Hist. University of Kansas, Lawrence, pp. 123-133
HANSEN, K.L. and D.E. SWEAT(1962):
Spermiation in Rana P. pipiens in response to heteroplasmatic pituitary materials.
Quart. J. Fla. Acad. Sci., 25(2), 109-120
HATCH, A.C., L.K. BELDEN, E. SCHEESSELE and A.R. BLAUSTEIN (2001):
Juvenile amphibians do not avoid potential lethal levels of urea on soil substrate.
Environ. Toxicol. Chem. 20, 2328-2335
HAY, J.M., I. RUVINSKY, S.B. HEDGES and L.R. MAXSON (1995):
Phylogenetic relationships of amphibian families inferred from DNA sequences of mitochondrial 12S and 16S ribosomal RNA genes.
Mol. Biol. Evol. 12, 928-937
HAYES, T.B. (1998):
Sex determination and primary sex differentiation in amphibians: Genetic and developmental mechanism.
J. Exp. Zool. 281, 373-399.
HAYES, T.B. (2000):
Endocrine disruption in amphibians. In: Sparling, D.W., G. Linder, and C. Bishop, (Eds.), Ecotoxicolology of amphibians and reptiles.
SETAC Press, Pensacola, USA. Pp. 573-593
HAYES, T.B. (2005):
Welcome to the revolution: integrative biology and assessing the impact of endocrine disruptors on environmental and public health.
J. Integr. Comp. Biol. 45, 321-329
HAYES, T.B., P. CASE, S. CHUI, D. CHUNG, C. HAEFFELE, K. HASTON, M. LEE, V.P. MAI, Y. MARJUOA, J. PARKER and M. TSUI (2006):
Pesticide mixtures, endocrine disruption, and amphibian declines: are we underestimating the impact?
Environ. Health Perspect. 114(Suppl. 1), 40-50
HAYES, T.B., A. COLLINS, M. LEE, M. MENDOZA, N. NORIEGA, A.A. STUART and A. VONK (2002):
Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses.
Proc. National Acad. Sci. USA 99, 5476-5480
HAYES, T.B., K. HASTON, M. TSUI, A. HOANG, C. HAEFFELE and A. VONK (2002a):
Atrazine-induced hermaphroditism at 0.1 ppb in American leopard frogs (Rana pipiens): laboratory and field evidence.
Environ. Health Perspect. 111, 568-575
HAYES, T.B., K. HASTON, M. TSUI, A. HOANG, C. HAEFFELE and A. VONK (2002b):
Feminization of male frogs in the wild.
Nature 419, 895-896
HAYS, J.B., A.R. BLAUSTEIN, J.M. KIESECKER, P.D. HOFFMAN, I. PANDELOVA, A. COYLE and T. RICHARDSSON (1996):
Developmental responses of amphibians to solar and artificial UV-B sources: a comparative study.
Photochem. Photobiol. 64, 449-456
HEASMAN, J., S. HOLWILL and C.C. WYLIE (1991):
Fertilization of cultured Xenopus oocytes and use in studies of maternally inherited molecules. In: Kay, B., Peng, K., Benjamin, H., (Eds.), Methods in cell biology, vol.
36, Xenopus laevis: Practical uses in cell and molecular biology.
Academic Press, New York, USA. pp. 213-229
HELFRICH, L.A, R.J. NEVES and J. PARKHURST (2001):
Commercial frog farming.
Virginia Cooperative Extension, Publication 420-255
HILLIS, D.M., L.K. AMMERMAN, M.T. DIXON and O. DE SÁO (1993):
Ribosomal DNA and the phylogeny of frogs.
Herpetol. Monogr. 7, 118-131
HOLLINGER, T.G. and G.L. CORTON (1980):
Artificial fertilization of gametes from the South African clawed frog, Xenopus laevis.
Gamete Res. 3, 45-57
HOULAHAN, J.E., C.S. FINDLEY, B.R. SCHMIDY, A.J. MEYER and S.L. KUZMIN (2000):
Quantitative evidence for global amphibian declines.
Nature 404, 752-755
IIMORI, E., M.J. D’OCCHIO, A.T. LISLE and S.D. JOHNSTON (2005):
Testosterone secretion and pharmacological spermatozoal recovery in the cane toad (Bufo marinus).
Anim. Reprod. Sci. 90, 163-173
INGER, R.F. (1967):
The development of a phylogeny of frogs.
Evolution 21, 369-384.
ITURRA, P. and A. VELOSO (1981):
Evidence for heteromorphic sex chromosomes in male amphibians (Anura:
Leptodactylidae).
Cytogenet. Cell. Genet. 31, 108-110
IUCN (2007):
2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 21 December 2007.
JAFFE, L.A., R.T. KADO and L. MUNCY (1985):
Propagating potassium and chloride conductances during activation and fertilization of the egg of the frog, Rana pipiens.
J. Physiol. 368, 227-242
JAMIESON, B.G.M. (1999):
Spermatozoal phylogeny of the vertebrata. In: Gagnon, C., (Ed.), The male gamete:
From basic science to clinical applications.
Cache River Press, Vienna, USA. pp. 303-331
JANCOVICH J.K.,E.W. DAVIDSON, N. PARAMESWARAN, J. MAO, V.G.
CHINCHAR, J.P. COLLINS, B.L. JACOBS and A. STORFER (2005):
Evidence for emergence of an amphibian iridoviral disease because of human-enhanced spread.
Mol. Ecol. 14(1), 213-224
JOHNSON, P.T.J., J.M. CHASE, K.L. DOSCH, R.B. HARTSON, J.A. GROSS, D.J.
LARSON, D.R. SUTHERLAND and S.R. CARPENTER (2007):
Aquatic eutrophication promotes pathogenic infection in amphibians.
Proc. Nat. Acad. Sci. U.S.A. 104(40), 15781-15786
KAMIMURA M., K. IKENISHI, M. KOTANI and T. MATSUNO (1976):
Observations on the migration and proliferation of gonocytes in Xenopus laevis.
J. Embryol. Exp. Morphol. 36, 197-207
KATAGIRI, C. (1974):
A high frequency of fertilization in premature and mature coelomic toad eggs after enzymic removal of vitelline membrane.
J. Embryol. Exp. Morphol. 31, 573-587
KATS, L.B., J.M. KIESECKER, D.P. CHIVERS and A.R. BLAUSTEIN (2000):
Effects of UV-B radiation on antipredator behavior in three species of amphibians.
Ethology 106, 921-932
KISHIGAMI, S., E. MIZUTANI, H. OHTA, T. HIKICHI, N. VAN THUAN, S.
WAKAYAMA, H. BUI and T. TERUHIKO (2006):
Significant improvement of mouse cloning technique by treatment with trichostatin A after somatic nuclear transfer.
Biochem. Biophys. Res. Commun. 340(1), 183-189
KNAPP, R.A. (1996): Nonnative trout in natural lakes of the Sierra Nevada: An analysis of their distribution and impacts on native aquatic biota.
Sierra Nevada ecosystem project: final report to Congress. University of California, USA. Vol. III, pp. 363-407
KNAPP, R.A., D.M. BOIANO and V.T. VREDENBURG (2007):
Removal of nonnative fish results in population expansion of a declining amphibian (mountain yellow-legged frog, Rana muscosa)
Biol. Conserv. 135(1), 11–20
KNUTSON, M.G, W.B. RICHARDSON, D.M. REINEKE, B.R. GRAY, J.R.
PARMELEE and S.E. WEICK (2004):
Agricultural ponds support amphibian populations.
Ecol. Appl. 14(3), 669-684
KUES, W.A. and H. NIEMANN (2004):
The contribution of farm animals to human health.
Trends Biotechnol. 22, 286-294
KWON, H.B., K.J. CHANG, Y.R. YOO, C.C. LEE and A.W. SCHUETZ (1992):
Induction of ovulation and oocyte maturation of Amphibian (Rana dybowskii) ovarian follicles by protein kinase C activation in vitro.
Biol. Reprod. 47, 169-176
LAHNSTEINER, F., T. WEISMANN and R.A. PATZNER (1997):
Aging processes of rainbow trout semen during storage.
The Progressive Fish-culturist 59, 272-279
LA MARCA, E., K.R. LIPS, S. LÖTTERS, R. PUSCHENDORF, R. IBAÑEZ and S.
RON (2005):
Catastrophic population declines and extinctions in neotropical harlequin frogs (Bufonidae: Atelopus).
Biotropica 37, 190-201
LA MARCA, E. and C. SEÑARIS (2004):
Dendrobates steyermarki. In: IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 14 May 2008.
LANGE, J. (1981):
Beitrag zur Zucht von Smaragd-Baumsteigerfröschen (Dendrobates auratus).
Z. Kölner Zoo 24(1), 6-8
LANNOO, M.J., K. LANG, T. WALTZ and G.S. PHILLIPS (1994):
An altered amphibian assemblage: Dickinson County, Iowa, 70 years after Frank Blanchard’s survey.
Am. Midland Naturalist 131, 311-319
LEE, M.S.Y. and B.G.M. JAMIESON (1993):
The ultrastructure of the spermatozoa of bufonid and hylid frogs (Anura, Amphibia) - Implications for phylogeny and fertilization biology.
Zool. Scripta 22, 309-323
LEFCORT, H., R.A. MEGUIRE, L.H. WILSON and W.F. ETTINGER (1998):
Heavy metals alter the survival, growth, metamorphosis, and antipredatory behavior of Columbia spotted frog (Rana luteiventris) tadpoles.
Arch. Environ. Contam. Toxicol. 35, 447-456
LICHT, P. (1973):
Induction of spermiation in anurans by mammalian pituitary gonadotropins and their subunits.
Gen. Comp. Endocrinol. 20, 2-529
LIPS, K.R, F. BREM, R. BRENES, J.D. REEVE, R.A. ALFORD, J. VOYLES, C.
CAREY, L. LIVO, A.P. PESSIER and J.P. COLLINS (2006):
Emerging infectious disease and the loss of biodiversity in a neotropical amphibian
Emerging infectious disease and the loss of biodiversity in a neotropical amphibian