Ontogenetic shifts in microhabitat preference of the temperate reef fish Forsterygion lapillum: implication for population limitation

Quantitative surveys of habitat associations of New Zealand's common triplefin fish Forsterygion lapillum suggest that young settlers disproportionately occur within the fronds of the large brown algae Cystophora retroflexa and C. torulosa (hereafter collectively referred to as Cystophora). This apparent preference is specific to Cystophora (i.e. fish do not appear to respond to structurally similar macroalgal species) and is not exhibited by older juveniles or adults of the species, which suggests that age-specific microhabitat requirements may act as a bottleneck to recruitment. To determine whether the overuse of Cystophora by newly settled F. lapillum could be attributed to a behavioural preference for this specific habitat, we conducted a lab-based choice experiment. Using a purpose-built 'choice chamber' that facilitated assessments of behavioural responses of focal individuals provided with a choice of 4 common habitat types, we determined that newly settled F. lapillum selected chambers containing Cystophora more frequently than predicted by random assortment. To test the ecological consequences of this behavioural preference, we conducted a field experiment (replicated at 2 sites) that manipulated Cystophora cover and examined subsequent patterns of recruitment by F. lapillum. Experimental additions of Cystophora cover enhanced local recruitment of F. lapillum, and the effects of Cystophora additions were most pronounced at the site where Cystophora was naturally rare. Overall, these results suggest that age-specific behavioural preferences may mediate ontogenetic shifts in microhabitat use and limit recruitment in local populations. © Inter-Research 2006.

Ontogenetic shifts in microhabitat preference of the temperate reef fish Forsterygion lapillum: implication for population limitation

Quantitative surveys of habitat associations of New Zealand's common triplefin fish Forsterygion lapillum suggest that young settlers disproportionately occur within the fronds of the large brown algae Cystophora retroflexa and C. torulosa (hereafter collectively referred to as Cystophora). This apparent preference is specific to Cystophora (i.e. fish do not appear to respond to structurally similar macroalgal species) and is not exhibited by older juveniles or adults of the species, which suggests that age-specific microhabitat requirements may act as a bottleneck to recruitment. To determine whether the overuse of Cystophora by newly settled F. lapillum could be attributed to a behavioural preference for this specific habitat, we conducted a lab-based choice experiment. Using a purpose-built 'choice chamber' that facilitated assessments of behavioural responses of focal individuals provided with a choice of 4 common habitat types, we determined that newly settled F. lapillum selected chambers containing Cystophora more frequently than predicted by random assortment. To test the ecological consequences of this behavioural preference, we conducted a field experiment (replicated at 2 sites) that manipulated Cystophora cover and examined subsequent patterns of recruitment by F. lapillum. Experimental additions of Cystophora cover enhanced local recruitment of F. lapillum, and the effects of Cystophora additions were most pronounced at the site where Cystophora was naturally rare. Overall, these results suggest that age-specific behavioural preferences may mediate ontogenetic shifts in microhabitat use and limit recruitment in local populations. © Inter-Research 2006.

Behavioural responses of the hagfish Eptatretus stoutii to nutrient and noxious stimuli

The suitability of a traditional testing paradigm (e.g. choice chamber) for assessing chemosensory behaviour in the Pacific hagfish, Eptatretus stoutii, was examined. Actively-swimming hagfish, tested at night, showed no preference for any region of a T-maze in the absence of a stimulus, but in the presence of an olfactory food cue, spent significantly more time in the zone where the cue was placed. Conversely, hagfish avoided spending time in the zone the fish anaesthetic 3-amino benzoic acid ethylester (MS-222) was placed, and demonstrated significantly more reversal responses in which the fish moved its body backwards. These data suggest that hagfish are an amenable model species for laboratory testing of behaviour.

Repellent activity of Abroma augusta extracts against Tribolium castaneum (Herbst) adults

Context: Repellency test can play an important role in special environmental conditions. Objectives: The main objective of this study was to make a standard protocol to control the pest by screening the test materials using adult beetles by repellency test to see whether or not the extracts contain any potential to repel the stored grain pest. Materials and Methods: The experiment was conducted in choice chamber, which was divided by half filter paper discs (Whatman No. 40, diameter 9 cm). One half of the filter paper was loaded with untreated (control) and the other half was loaded with the extract of A. augusta. All the CHCl3 extracts were separately applied onto each of the half-discs and allowed to dry out in the air for 10 mins. Each treated half-disc was then attached lengthwise, edge-to-edge, to a control half-disc with adhesive tape and placed in petri dishes. The orientation of the same was changed in the replicates to avoid the effects of any external directional stimulus affecting the distribution of the test insects Tribolium castaneum (Herbst). Ten adult insects were released in the middle of each of the filter-paper circles and each test was replicated five times. Results: All the test extracts of seed, leaves, root wood, stem bark and stem wood of A. augusta collected in chloroform showed repellent activity against adult beetles of T. castaneum at dose levels of 314.540, 157.270, 78.635, 39.318, 19.659 and, 9.831 ?g/cm2 on filter paper. According to the intensity of repellency the results could be arranged in the order: stem bark >seed> root wood > leaf > stem wood and in all the cases significant differences were obtained. Conclusion: The present results revealed that A. augusta extracts can be used as a reduced risk repellent compound in the grain and cereal stores to manage the population of T. castaneum. The results also seen to be encouraging when there is a greater need for environment-friendly pesticides then ever before. DOI: http://dx.doi.org/10.3329/jbs.v20i0.17655 J. bio-sci. 20: 49-55, 2012

Ocean acidification erodes crucial auditory behaviour in a marine fish

Ocean acidification is predicted to affect marine ecosystems in many ways, including modification of fish behaviour. Previous studies have identified effects of CO 2 -enriched conditions on the sensory behaviour of fishes, including the loss of natural responses to odours resulting in ecologically deleterious decisions. Many fishes also rely on hearing for orientation, habitat selection, predator avoidance and communication. We used an auditory choice chamber to study the influence of CO 2 -enriched conditions on directional responses of juvenile clownfish ( Amphiprion percula ) to daytime reef noise. Rearing and test conditions were based on Intergovernmental Panel on Climate Change predictions for the twenty-first century: current-day ambient, 600, 700 and 900 µatm p CO 2 . Juveniles from ambient CO 2 -conditions significantly avoided the reef noise, as expected, but this behaviour was absent in juveniles from CO 2 -enriched conditions. This study provides, to our knowledge, the first evidence that ocean acidification affects the auditory response of fishes, with potentially detrimental impacts on early survival.

Host choice and penetration bySchistosoma haematobiummiracidia

Schistosome parasites commonly show specificity to their intermediate mollusc hosts and the degree of specificity can vary between parasite strains and geographical location. Here the role of miracidial behaviour in host specificity ofSchistosoma haematobiumon the islands of Zanzibar is investigated. In choice-chamber experiments,S. haematobiummiracidia moved towardsBulinus globosussnail hosts in preference to empty chambers. In addition, miracidia preferred uninfected over patentB. globosus. This preference should benefit the parasite as patent snails are likely to have mounted an immune response toS. haematobiumas well as providing poorer resources than uninfected snails. Miracidia also discriminated between the hostB. globosusand the sympatric, non-host speciesCleopatra ferruginea. In contrast,S. haematobiumdid not discriminate against the allopatricBulinus nasutus. Penetration of the host by miracidia was investigated by screening snails 24 h after exposure using polymerase chain reaction (PCR) withS. haematobiumspecificDraI repeat primers. There was no difference in the frequency of penetration ofB. globosusversusB. nasutus. These responses to different snail species may reflect selection pressure to avoid sympatric non-hosts which represent a transmission dead end. The distribution ofB. nasutuson Unguja is outside the endemic zone and so there is less chance of exposure toS. haematobium, hence there will be little selection pressure to avoid this non-host snail.

Quantitative genetics and behavioural correlates of digit ratio in the zebra finch

A recent study on a captive zebra finch population suggested that variation in digit ratio (i.e. the relative length of the second to the fourth toe) might be an indicator of the action of sex steroids during embryo development, as is widely assumed for human digits. Zebra finch digit ratio was found to vary with offspring sex, laying order of eggs within a clutch, and to predict aspects of female mating behaviour. Hence, it was proposed that the measurement of digit ratio would give insights into how an individual's behaviour is shaped by its maternal environment. Studying 500 individuals of a different zebra finch population I set out to: (1) determine the proximate causes of variation in digit ratio by means of quantitative genetics and (2) to search for phenotypic and genetic correlations between digit ratio, sexual behaviour and aspects of fitness. In contrast to the earlier study, I found no sexual dimorphism in digit ratio and no effect of either laying order or experimentally altered hatching order on digit ratio. Instead, I found that variation in digit ratio was almost entirely additive genetic, with heritability estimates ranging from 71 to 84%. The rearing environment (from egg deposition to independence) explained an additional 5–6% of the variation in digit ratio, but there was no indication of any maternal effects transmitted through the egg. I found highly significant phenotypic correlations (and genetic correlations of similar size) between digit ratio and male song rate (positive correlation) as well as between digit ratio and female hopping activity in a choice chamber (negative correlation). Rather surprisingly, the strength of these correlations differed significantly between subsequent generations of the same population, illustrating how quickly such correlations can appear and disappear probably due to genotype–environment interactions.

Food preferences of a fungal-feeding Aphelenchoides species

The growth of Aphelenchoides sp. populations was investigated in vitro with 17 different fungal species as food source. Nematode mass cultures were obtained with saprophytic (Agrocybe, Chaetomium) and especially with mycorrhizal fungi (Cenococcum, Hymenoscyphus, Laccaria). Mitosporic species, like Alternaria, Monocillium or Penicillium, were generally meagre or non-hosts. This poor host suitability is likely due to the release of toxic metabolites (e.g. antibiotics) and/or to morphological differences (e.g., forming of conidiophores) by the fungi. Frequent grazing of nematodes on mycorrhizal mycelia may be of major significance for the establishment and maintenance of mycorrhizal associations in the field. Food preference of Aphelenchoides sp. was tested in choice chamber experiments. Nematodes showed a marked preference for particular fungal species. They changed food source with time, indicating a “mixed diet” selection, probably a strategy to avoid the concentration of toxic metabolites. The attractiveness of a fungus was not necessarily correlated with its suitability as a host. That a poor fungal host can be a strong nematode attractant and influence their spatial distribution in the soil has implications for nematode populations in the field. In Laborexperimenten wurde die Vermehrung des Nematoden Aphelenchoides sp. mit 17 verschiedenen Pilzspezies als Nahrungsgrundlage untersucht. Neben saprophytischen Arten (Agrocybe, Chaetomium) eigneten sich insbesondere Mykorrhizapilze (Cenococcum, Hymenoscyphus, Laccaria) für eine Massenvermehrung. Eine schlechte Nahrungsquelle stellten mitosporische Arten, wie Alternaria, Monocillium oder Penicillium, dar. Dies dürfte auf toxische Stoffwechselprodukte (z.B., Antibiotika) und/oder auf morphologische Unterschiede (z.B., Sporenbildung) zurückzuführen sein. Die gute Vermehrung der Nematoden an Mykorrhizapilzen ist von weitreichender Bedeutung für das Freiland. Negative Auswirkungen auf die Ausbildung und Funktion von Mykorrhiza im Boden sind zu erwarten. In Nahrungswahlexperimenten zeigte Aphelenchoides sp. eine ausgeprägte Präferenz für bestimmte Pilzarten. Das Wechseln zwischen den einzelnen Pilzspezies weist auf die Bevorzugung von “Mischnahrung” hin. Dies dürfte eine Strategie zur Vermeidung von hohen Konzentrationen toxischer Nahrungsbestandteile sein. Präferenz und Nahrungsqualität standen nur in geringem Zusammenhang. Somit können auch Pilze, die eine schlechte Nahrungsquelle darstellen, attraktiv auf Nematoden wirken und deren Verbreitung in Boden und Rhizosphäre beeinflussen.

Phototactic responses of the cercaria of Echinoparyphium recurvatum during phases of sub-maximal and maximal infectivity

Phototactic responses of cercariae of the echinostome Echinoparyphium recurvatum (Digenea: Echinostomatidae) were investigated during phases of sub-maximal and maximal infectivity using a simple light/dark choice chamber. The phototactic responses of a total of 400 cercariae were examined in 20 replicate experiments during their sub-maxinal infectivity dispersal phase (0.5 h post-emergence from the first intermediate host Lymnaea peregra) and during their maximal infectivity phase (2.5 h post-emergence). Cercariae in the sub-maximal infectivity dispersal phase were found to be positively phototactic, significantly larger numbers of them occurring on the light side of a light/dark choice chamber P < 0.001. Cercariae in the maximal infectivity phase were found to be negatively phototactic, significantly larger numbers of them being found on the dark side of the choice chamber, P < 0.001. This report of ‘phototactic switching’ demonstrated by the cercariae of E. recurvatum from a positively phototactic dispersal phase to a negatively phototactic infection phase constitutes the first record of such behaviour in the cercaria of an echinostome.