Gerlach Gabriele

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Gerlach
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Gabriele
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  • Article
    Multiple genetic stocks of longfin squid Loligo pealeii in the NW Atlantic : stocks segregate inshore in summer, but aggregate offshore in winter
    (Inter-Research, 2006-04-03) Buresch, Kendra C. ; Gerlach, Gabriele ; Hanlon, Roger T.
    The longfin squid Loligo pealeii is distributed widely in the NW Atlantic and is the target of a major fishery. A previous electrophoretic study of L. pealeii was unable to prove genetic differentiation, and the fishery has been managed as a single unit stock. We tested for population structure using 5 microsatellite loci. In early summer (June), when the squids had migrated inshore to spawn, we distinguished 4 genetically distinct stocks between Delaware and Cape Cod (ca. 490 km); a 5th genetic stock occurred in Nova Scotia and a 6th in the northern Gulf of Mexico. One of the summer inshore stocks did not show genetic differentiation from 2 of the winter offshore populations. We suggest that squids from summer locations overwinter in offshore canyons and that winter offshore fishing may affect multiple stocks of the inshore fishery. In spring, squids may segregate by genetic stock as they undertake their inshore migration, indicating an underlying mechanism of subpopulation recognition.
  • Preprint
    Characterization of EST derived SSRs from the bay scallop, Argopecten irradians
    ( 2005-03-03) Roberts, Steven B. ; Romano, Christina ; Gerlach, Gabriele
    Interest in bay scallop conservation has resulted in organized stock enhancement efforts and increased attention to fisheries management issues. Genetic markers can facilitate the monitoring of enhancement efforts, characterization of wild populations, and optimize hatchery practices. We have identified eight polymorphic simple sequence repeat markers including one dinucleotide, six trinucleotide and one compound dinucleotide repeats, in expressed sequence tags generated from multiple bay scallop cDNA libraries. The numbers of alleles range from two to five. The expected and observed heterozygosities range from 0.093 to 0.720 and 0.095 to 0.600, respectively.
  • Preprint
    Humic acid interferes with species recognition in zebrafish (Danio rerio)
    ( 2007-10-01) Fabian, Niora J. ; Albright, Lindsey B. ; Gerlach, Gabriele ; Fisher, Heidi S. ; Rosenthal, Gil G.
    Few studies have addressed how chemosensation may be impaired by chemical alterations of the environment and anthropogenic disturbance. Humic acid (HA) is a pervasive, naturally occurring organic derivative found in aquatic and terrestrial environments; human activity, however, can lead to elevated levels of HA. Recent studies suggest that environments that contain high levels of HA may hinder chemical communication. We tested the ability of adult zebrafish (Danio rerio) to discriminate between conspecific and heterospecific urinary chemical cues found in the presence and absence of HA. We show that high humic acid levels (200 mg/l) can impair the ability to differentiate conspecifics from heterospecifics. We also found that zebrafish prefer untreated water over HA-treated water. These findings suggest that, in addition to human-produced synthetic compounds, changes in the abundance of naturally occurring substances may also negatively impact natural behaviors in aquatic species by disturbing the sensory environment.
  • Preprint
    Planktonic Larval Duration, age and growth of Ostorhinchus doederleini (Pisces: Apogonidae) on the southern Great Barrier Reef, Australia
    ( 2013-09-15) Kingsford, Michael J. ; Finn, M. D. ; O’Callaghan, M. D. ; Atema, Jelle ; Gerlach, Gabriele
    Cardinalfishes (Apogonidae) are abundant on corals reefs, but there are few data on demography to understand trophodynamics and population dynamics. Ostorhinchus doederleini is a small and abundant apogonid on the Great Barrier Reef (GBR) and throughout the Western Pacific Ocean. We present key demographic parameters for the entire life history from the southern GBR. Daily deposition of increments in otoliths was validated. Fish had a Planktonic Larval Duration (PLD) of 16 to 26 days. PLD was established from fish collected immediately prior to settlement as no settlement mark was found. Fish grew at about 0.35 mm d-1 for the first 20 d after settlement. Fish reached a maximum standard length at about 200 d and no fish lived longer than 368 d at four reefs separated by kilometers to tens of kilometres. There was no evidence for differences in size at age between sexes. Mortality was very high, for fish greater than 60 days old mortality ratesranged from 2.9 to 4.6% per day. Short lives and high mortality rates makes O. doederleini, and potentially other apogonids, vulnerable to recruitment failure. Here we review data on the demographic characteristics of other reef fishes. Although some taxa live to over 50 years, the short lives of apogonids are most aligned with the Gobiidae and Blenniidae (i.e. typically < 1.5 years). Descriptions of fish size, age, longevity, growth and mortality; from hatching to age maxima are very rare for most taxa, even at the level of family.
  • Preprint
    The behaviour and ecology of the zebrafish, Danio rerio
    ( 2007-03-07) Spence, Rowena ; Gerlach, Gabriele ; Lawrence, Christian ; Smith, Carl
    The zebrafish is an important model organism in developmental genetics, neurophysiology and biomedicine, but little is known about its natural ecology and behaviour. It is a small, shoaling cyprinid, native to the flood-plains of the Indian subcontinent, where it is found in shallow, slow-flowing waters. Zebrafish are group spawners and egg scatterers, although females are choosy with respect to sites for oviposition and males defend territories around such sites. Laboratory studies of zebrafish behaviour have encompassed shoaling, foraging, reproduction, sensory perception and learning. These studies are reviewed in relation to the suitability of the zebrafish as a model for studies on cognition and learning, development, behavioural and evolutionary ecology, and behavioural genetics.
  • Article
    Tactical release of a sexually-selected pheromone in a swordtail fish
    (Public Library of Science, 2011-02-09) Rosenthal, Gil G. ; Fitzsimmons, Jessica N. ; Woods, Kristina U. ; Gerlach, Gabriele ; Fisher, Heidi S.
    Chemical communication plays a critical role in sexual selection and speciation in fishes; however, it is generally assumed that most fish pheromones are passively released since most fishes lack specialized scent glands or scent-marking behavior. Swordtails (genus Xiphophorus) are widely used in studies of female mate choice, and female response to male chemical cues is important to sexual selection, reproductive isolation, and hybridization. However, it is unclear whether females are attending to passively produced cues, or to pheromones produced in the context of communication. We used fluorescein dye injections to visualize pulsed urine release in male sheepshead swordtails, Xiphophorus birchmanni. Simultaneous-choice assays of mating preference showed that females attend to species- and sex-specific chemical cues emitted in male urine. Males urinated more frequently in the presence and proximity of an audience (conspecific females). In the wild, males preferentially courted upstream of females, facilitating transmission of pheromone cues. Males in a teleost fish have evolved sophisticated temporal and spatial control of pheromone release, comparable to that found in terrestrial animals. Pheromones are released specifically in a communicative context, and the timing and positioning of release favors efficient signal transmission.
  • Preprint
    Kin and population recognition in sympatric Lake Constance perch (Perca fluviatilis L.) : can assortative shoaling drive population divergence?
    ( 2005-08-02) Behrmann-Godel, Jasminca ; Gerlach, Gabriele ; Eckmann, Reiner
    Prior studies have shown that perch (Perca fluviatilis L.) of Lake Constance belong to two genetically different but sympatric populations, and that local aggregations of juveniles and adults contain closely related kin. In this study we analysed the genetic structure of pelagic perch larvae to investigate, if kin structured shoals already exist during early ontogenetic development or might be the result of homing to natal sites. Analysis of the gene frequencies at five microsatellite loci revealed that 3 out of 5 pelagic aggregations of larvae showed significant accumulation of kin. To investigate possible mechanisms of shoal formation, we tested if perch use olfactory cues to recognize their kin. Choice tests in a fluviarium showed preference for odours of unfamiliar kin versus unfamiliar non-kin. Additionally, we showed that perch could differentiate between the odours of the two sympatric populations and significantly preferred unfamiliar and unrelated conspecifics of their own over the foreign population. Our results present a behavioural mechanism that could lead to the observed formation of kin structured shoals in perch. We further discuss if the ability to discriminate between the own and the foreign population could result in assortative mating within populations and thus form the basis of “socially mediated speciation” in perch.