A duration-dependent negative potential in the cichlid electroretinogram.

A negative potential can be evoked in the local electroretinogram of the cichlid fish Cichlasoma octofasciatum by light stimuli of duration longer than 70 msec. This response superficially resembles the proximal negative response, but differs in some waveform components and dependence upon stimulus configuration and duration.     

Enzymatic characterization of nine endoparasite species of small ermine moths (Yponomeutidae)

Summary Eight hymenopterous and 1 dipterous species, all endoparasitic in eggs, larvae, or pupae of small ermine moths (Yponomeuta) were investigated for their allozyme variation at 3–29 loci. The mean heterozygosity level of the hymenopterous species is one-third of that of the dipterous species. Zymogram patterns of the parasite larvae do not interfere with those of the host.     

Inter-locus allozyme mobility correlations and species divergence

Summary An analysis of allozyme data from numerous sets of related vertebrate andDrosophila species shows that species divergence does not generally seem to be accompanied by an overall increase or decrease in enzyme charge. The 2 significant results came from vertebrate inter-generic comparisons.     

Cone mosaic in a teleost retina: No difference between light and dark adapted states

Summary The mosaic arrangement of retinal cones in the eye of the African cichlid fish,Haplochromis burtoni, is the same in both light and dark adapted states. This is in contrast to Kunz' claim² that the retinal mosaic pattern changes from a square to a row type during dark adaptation, in the guppy (Poecelia reticulata). Kunz' histological procedure may account for this difference in results.Acknowledgments. This work was supported by grants from the Whitehall Foundation and NIH EY02284. I thank L. Shelton for expert histological assistance.     

Effects of pressure on oxygen consumption in cottid fish from Lake Baikal

Summary Rates of oxygen consumption in shallow dwelling cottid fish from Lake Baikal were unaffected by a change in pressure from 11 to 51 ata. The metabolic rate of deep cottids decreased by 72% when the pressure was decreased by 50% from that corresponding to habitat depth. Recovery from decreased pressures was incomplete in deep fish, suggesting that measurements of in deep dwelling fish in the literature may underestimate actual rates.Acknowledgments. Thanks are due to the US and USSR Academies of Sciences and the crew of the Titov. Support was provided by grants from The National Geographic Society, The George Baker Trust, The Max and Victoria Dreyfus Foundation, and The Griffis Foundation, Inc.     

Accessibility of host cell lineages to medaka stem cells depends on genetic background and irradiation of recipient embryos

Chimera formation is a powerful tool for analyzing pluripotency in vivo. It has been widely accepted that host cell lineages are generally accessible to embryonic stem (ES) cells with the actual contribution depending solely on the intrinsic pluripotency of transplanted donor cells. Here, we show in the fish medaka (Oryzias latipes) that the host accessibility to ES cell contribution exhibits dramatic differences. Specifically, of three albino host strains tested (i ¹ , i ³ and af), only strain i ¹ generated pigmented chimeras. Strikingly, this accessibility is completely lost in i ¹ but acquired in i ³ after host γ-irradiation. Host irradiation also differentially affected ES cell contribution to somatic organs and gonad. Therefore, the accessibility of various host cell lineages can vary considerably depending on host strains and cell lineages as well as on irradiation. Our findings underscore the importance of host genotypes for interpreting donor cell pluripotency and for improving ES-derived chimera production.     

Differential evolution of signal-responsive RNA elements and upstream factors that control alternative splicing

Cell signal-regulated alternative splicing occurs for many genes but the evolutionary origin of the regulatory components and their relationship remain unclear. This review focuses on the alternative splicing components of several systems based on the available bioinformatics data. Eight mammalian RNA elements for signal-regulated splicing were aligned among corresponding sequences from dozens of representative vertebrate species to allow for assessment of the trends in evolutionary changes. Four distinct trends were observed. Four of the elements are highly conserved in bird, reptile and fish species examined (i); two elements can be found in fish but the sequences have been changing till in marsupials or higher mammals (ii); one element is almost exclusively found in mammals with mostly the same sequence (iii); and one element can be found in birds or lower vertebrates but expanded abruptly to have variable numbers of copies in mammals (iv). All examined prototype trans-acting factors and protein kinases emerged earlier than the RNA elements but additional (paralog) factors emerged in the same or later species. Thus, after their emergence mainly in fish or mammals with pre-existing prototype trans-acting factors/kinases, half of the elements have been highly conserved from fish to humans but the other half have evolved differentially with additional trans-acting factors. Their differential evolution likely contributes to the exon- and species/class-specific control of alternative splicing and its regulation by cell signals. The evolvement of a group of mammal-specific components would help relay signals from extracellular stimuli to the splicing machinery and thus contribute to higher proteomic diversity.     

Evidence for rapid speciation in African cichlid fishes

Summary Extremely rapid divergence among 7 species of African cichlid fishes is suggested by high estimates of allozymic similarity. Significant differences in gene frequencies among sympatric populations support reproductive isolation of these taxa.A portion of this study was submitted in partial fulfillment of requirments for the Ph. D from the State University of New York, Stony Brook. I thank T. D. Eccles and J. Tarbit for support and expertise, R. H. Gibbs, Jr, and V. G. Springer for review of an earlier draft, and R. K. Koehn for interest in all stages of this work. Supported in part by grants GM-25343 and GB-38662 from NIH and NSF (to RKK) and a grant-in-aid from the Society of Sigma Xi.     

Cytotaxonomy of the Seychelles tree frog,Megalixalus seychellensis (Duméril and Bibron) (Amphibia: Hyperoliidae)

Summary The Seychelles tree frog,Megalixalus seychellensis has 2n=24 chromosomes of gradually decreasing length. Pairs 2, 3, and 4 are submetacentric, and the remaining pairs are metacentric. The karyotype affirms hyperoliid assignment of this species, and indicates a link between the Seychellean fauna and the African-Madagascan faunas.Research supported by the National Geographic Society.     

The role of motile aeromonads in the fish disease, ulcerative disease syndrome (UDS)

Ulcerative Disease Syndrome (UDS) is an epizootic fish disease characterized by the presence of severe, open dermal ulcers on the head, midbody, and dorsal regions of the fish. Aeromonas hydrophila and A. sobria were recovered more often from UDS fish than other bacteria from the genera Vibrio, Alteromonas and Plesiomonas. Representative isolates of A. hydrophila, A. sobria, V. anguillarum, V. vulnificus, Alteromonas putrefaciens, and P. shigelloides taken from UDS and healthy fish were assayed for virulence-associated factors. The aeromonads produced a wide variety of hydrolytic enzymes and expressed cell surface characteristics linked to virulence whereas the other bacterial species rarely produced the same enzymes or cell surface characteristics. The role of aeromonads in UDS is believed to be opportunistic or secondary and these bacteria are thought to play an important role in this degenerative disease.     

Pollution in Lake Leman. Evidence for the accumulation of tin in crustacean plankton: first results obtained by X ray spectrography]

Zooplankton was collected monthly from Leman Lake, from November 1976 to April 1977. Six of the most representative species of freshwater zooplankton were analyzed: Bosmina sp, Daphnia longispina, Bythotrephes longimanus, Leptodora kindtii, Eudiaptomus gracilis and Cyclops prealpinus. All of the samples were shown to accumulate tin in their different organs and tissues where high values were generally found. The consequences of concentration of this toxic element for aquatic food chains are discussed.     

Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken -crystallin gene was expressed in several tissues of transgenic fish. Rainbow trout growth hormone cDNA driven by the Rous sarcoma virus promoter was expressed in transgenic carps leading to a faster growth of these animals. The antifreeze protein gene from flounder was expressed in transgenic salmon. These data indicate that transgenesis in fish is relatively easy but that fish gene sequences must be preferably used to obtain a good expression of the transgenes. Fish is a good biological model, specially for developmental studies and it is an increasing part of human food. For these reasons, transgenesis in fish is most likely to be more and more practised in the coming years.     

Chemical defense of crinoids by polyketide sulphates.

The range of (presumed) polyketide constituents in comatalid crinoids has been extended to include bianthronyls, meso-naphthodianthrones and sulphate esters of various of the polyketides. Several species of fish are deterred from eating food by the inclusion in it of these sulphates at the concentration found in crinoids. Sodium 2-hydroxy-anthraquinone sulphate and anthraquinone-2-suphonate were also active as antifeedants for the species tested.     

Relationship between size of muscle fibres and body dimensions in a number of teleosts.

In a survey of 17 species of teleosts, a direct relationship was found between the diameter of muscle fibres and estimated volume of the fish. The results also suggested an inverse relationship between muscle fibre diameter and 'streamlinedness' of the fish (as measured by length:height ratio).     

The biology of streams as part of Amazonian forest ecology

Summary Data on long-term research on the ecology of Central Amazonian forest streams are presented and they reveal the following basic features: Firstly, the essential input of nutrients into these waters consists of forest litter and of the fungi that decompose this litter; consequently, the bulk of the fauna is concentrated in accumulations of submerged litter. Secondly, the nutrients released by the decomposition of this litter do not appear in solution in the stream water, but are tied up throughout in the food web of the aquatic fauna. Thirdly, this food web is relatively robust. This is due to the absence of food specialists in the major channels of energy transfer. One of the staple foods for invertebrate predators consists of chironomid larvae. Fourthly, the degree of acidity and/or the content of dissolved humic substances (more or less black water) has a marked effect on the density and to a lesser extent on the species diversity of the invertebrate fauna, black waters being richer in both. Fifthly, the annual inundations of the forest in the middle and lower courses of the smaller rivers lead to drastic periodic changes of animal densities, and in some cases to annual periodicity of breeding, as exemplified by a three-year study of shrimp populations in the river Tarumazinho.     

Chemical defense of crinoids by polyketide sulphates

Summary The range of (presumed) polyketide constituents in comatalid crinoids has been extended to include bianthronyls, meso-naphthodianthrones and sulphate esters of various of the polyketides. Several species of fish are deterred from eating food by the inclusion in it of these sulphates at the concentration found in crinoids. Sodium 2-hydroxy-anthraquinone sulphate and anthraquinone-2-suphonate were also active as antifeedants for the species tested.Acknowledgments. This author is indebted to the Australian Research Grants Commission for financial support, to Miss A. Clark of the British Museum of Natural History, London, and Ms J. Marshall of the Australian Museum, Sydney, for identifications of crinoid specimens and to Mr C. Lee, Director of the Deception Bay Laboratory of the Qld. Fisheries Service for providing facilities, fish and valuable advice.     

A genetic study of intergradation between Mytilus edulis and Mytilus galloprovincialis

A study of geographic variation at 2 diagnostic allozyme loci in the mussels Mytilus edultis and M. galloprovincialis reveals considerable spatial variation, both in allele frequencies and in the extent of intergradation.     

Neozoans in european waters — Exemplifying the worldwide process of invasion and species mixing

The loss of biodiversity — the tendency of the world's fauna to become more and more homogeneous —is widely acknowledged as a problem. Biodiversity is threatened by neozoism and acculturation as much as the extinction of species, but these dangers are less well known. Neozoism and acculturation have an effect on two levels; they lead 1) to an equalisation of the faunal regions and their originally different, specially adapted biocenoses, and 2) to a reduction of genetic diversity below the species level. These processes develop very rapidly in the European waters, particularly in the lowland river systems. The present contribution gives a brief review on neozoans in European inland waters.     

Significant differential gene duplication without ancestral tetraploidy in a genus of mexican fish

Summary A comparison of the protein products of 20–25 structural gene loci among the known species of the goodeid fish genusSkiffia suggests that at least 4 loci (16–20%) have undergone species-specific duplications (or, in 1 case, apparent loss) during the evolution of the genus. The species are clearly diploids, and the data therefore indicate that even a large proportion of differentially duplicated loci within a group of related fish species is not critical evidence of common tetraploid ancestry. Differential duplication of structural gene loci may be an important component of the genetic differences that separate congeneric conventional diploid species.Supported by NSF grants DEB76-20958 (BJT), DEB77-03257 (EMR) and DEB77-17315 (RRM).     

Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken delta-crystallin gene was expressed in several tissues of transgenic fish.(ABSTRACT TRUNCATED AT 400 WORDS)