Enterococcus seriolicida sp. nov., a fish pathogen

The properties and taxonomic position of bacterial strains isolated from diseased specimens of cultured yellowtail and eels were examined. The isolates were gram-positive, short-chain-forming, catalase-negative, facultatively anaerobic cocci. Growth at 10 and 45 degrees C in 6.5% NaCl (pH 9.6) with 40% bile and in 0.1% methylene blue-milk were both positive. The isolates could be distinguished from other species of the genus Enterococcus by several biochemical characteristics and by Lancefield's group antigen. Guanine-plus-cytosine content of DNA was 44 mol% as determined by the thermal melting temperature. The value for DNA-DNA hybridization was sufficiently low to warrant distinguishing this species from reported. Enterococcus species. The name Enterococcus seriolicida is proposed. The type strain is YT-3 (=ATCC 49156).     

Inhibition of CRF- and urotensin I-stimulated ACTH release from goldfish pituitary cell columns by the CRF analogue alpha-helical CRF-(9-41)

alpha-Helical CRF-(9-41) is an analogue of corticotropin-releasing factor (CRF) that antagonizes CRF-stimulated ACTH release in rats. In the present study, alpha-helical CRF-(9-41) was tested to determine whether it would antagonize the ACTH-releasing activity of CRF or urotensin I (UI) observed with superfused, dispersed goldfish anterior pituitary cells. At a concentration of 4 microM, alpha-helical CRF-(9-41) completely blocked the ACTH-releasing activity of 100 nM CRF or 100 nM UI. The inhibitor by itself showed little intrinsic ACTH-releasing activity. This investigation reveals similarities in the CRF-antagonism of alpha-helical CRF-(9-41) in the teleost and mammalian pituitary in vitro. It also provides are similar and suggests that alpha-helical CRF-(9-41) may be useful as a tool to investigate the effects of CRF-like and UI-like peptides in teleost fishes.     

Speciation rates in lakes and the enigma of Lake Victoria

Hydrobiologia - Rates of evolutionary change in Lake Victoria continue to stimulate debate. If, as some have claimed, the present fauna is &;lt;15 000 years old, speciation must have...     

The copepod Salmincola edwardsii as a parasite of Salvelinus alpinus in Britain, and a consideration of the so-called relict fauna of Ennerdale Water

The lernaeopodid copepod Salmincola edwardsii is recorded for the first time in the British Isles as a parasite of the salmonid fish Salvelinus alpinus . Material from Ennerdale Water in the English Lake District is described and illustrated and evidence of the occurrence of the same species in four Scottish lochs is presented. An interesting biological feature of the Ennerdale population is that egg size varies almost three-fold in terms of volume in different individuals. Ennerdale's fauna is unique among those of British lakes in that it includes two crustaceans, Mysis relicta (known also from Ireland) and Limnocalanus macrurus (known nowhere else in the British Isles), both of which have been claimed as "ice-age" or "marine-glacial relicts". No satisfactory explanation of how Ennerdale could have acquired these animals has hitherto been put forward. A hypothesis which attempts to do so and which also accounts for the presence of Salmincola on the char of Ennerdale and of certain Scottish lochs, but not on populations of this fish in other Lake District lakes, is put forward. This utilizes knowledge of the biology of the animals in question, such information as is available concerning the disposition of the ice in the area at the time of its retreat, and the record of the post-glacial history of the Cumbrian lakes as preserved in their sediments.     

A new value for mol percent guanine + cytosine of DNA for the salmonid fish pathogen Renibacterium salmoninarum

The mol% G + C of DNA extracted from seven different isolates of Renibacterium salmoninarum was determined. Organisms studied were from selected geographical areas (U.S.A., Canada, England and France) and were isolated from five different species of salmonid fish. The mol% G + C was determined to be 55.5, higher than the currently reported value of 53.     

ACTH-releasing activity of urotensin I and ovine CRF: interactions with arginine vasotocin, isotocin and arginine vasopressin

The release of ACTH from superfused dispersed goldfish anterior pituitary cells was examined to determine if the neurohypophyseal peptides arginine vasotocin (AVT), isotocin (IST) or arginine vasopressin (AVP) potentiate the ACTH-releasing activities of the structurally homologous peptides urotensin I (UI) or ovine corticotropin-releasing factor (CRF). The ACTH-releasing activities of the neurohypophyseal peptides and UI or CRF were additive. AVT, IST or AVP failed to potentiate the ACTH-releasing activity of UI or CRF. These results suggest that in teleost fishes neurohypophyseal peptides have intrinsic ACTH-releasing activity but, unlike mammals, do not potentiate the release of ACTH evoked by CRF, or by the piscian CRF-like peptide, UI.