Habitat associations of juvenile versus adult butterflyfishes

Author Posting. © Springer-Verlag, 2008. This is the author's version of the work. It is posted here by permission of Springer-Verlag for personal use, not for redistribution. The definitive version was published in Coral Reefs 27 (2008): 541-551, doi:10.1007/s00338-008-0357-8.Many coral reef fishes exhibit distinct ontogenetic shifts in habitat use while some species settle directly in adult habitats, but there is not any general explanation to account for these differences in settlement strategies among coral reef fishes. This study compared distribution patterns and habitat associations of juvenile (young of the year) butterflyfishes to those of adult conspecifics. Three species, Chaetodon auriga, Chaetodon melannotus, and Chaetodon vagabundus, all of which have limited reliance on coral for food, exhibited marked differences in habitat association of juvenile versus adult individuals. Juveniles of these species were consistently found in shallow-water habitats, whereas adult conspecifics were widely distributed throughout a range of habitats. Juveniles of seven other species (Chaetodon aureofasciatus, Chaetodon baronessa, Chaetodon citrinellus, Chaetodon lunulatus, Chaetodon plebeius, Chaetodon rainfordi, and Chaetodon trifascialis), all of which feed predominantly on live corals, settled directly into habitat occupied by adult conspecifics. Butterflyfishes with strong reliance on corals appear to be constrained to settle in habitats that provide access to essential prey resources, precluding their use of distinct juvenile habitats. More generalist butterflyfishes, however, appear to utilise distinct juvenile habitats and exhibit marked differences in the distribution of juveniles versus adults.This research was funded by a JCU Program Grant to MSP, while MLB was supported by an NSF (USA) Graduate Research Fellowship

High-quality habitat and facilitation ameliorate competitive effects of prior residents on new settlers

Many species disperse during their lifetime. Two factors that can affect the performance of individuals following dispersal are the presence of conspecifics and intrinsic habitat quality at the settlement site. Detecting the influence of these factors can be difficult for at least two reasons: (1) the outcomes of interactions with conspecifics are often variable including both competition and facilitation, and (2) selection of high quality habitats often leads to positive covariance between habitat quality and density. In this study, I investigate positive and negative effects of resident blue streak cleaner wrasse (Labroides dimidiatus) on the growth and survival of recently settled conspecifics while accounting for habitat quality. Juvenile L. dimidiatus settle near adult conspecifics, but likely have to compete with resident adults for access to food. However, field experiments indicate that settlers have access to more resources at occupied sites, and as a result, grow faster despite evidence for competition with residents. This result is a direct consequence of two factors: (1) resident conspecifics facilitate settlers by attracting client fish, and (2) resident conspecifics are strongly associated with high quality habitat. These results highlight the need to simultaneously consider habitat quality and competitive and facilitative interactions between conspecifics when making inferences about ecological processes from spatial patterns of individual performance

Habitat Associations of Juvenile Fish at Ningaloo Reef, Western Australia: The Importance of Coral and Algae

Habitat specificity plays a pivotal role in forming community patterns in coral reef fishes, yet considerable uncertainty remains as to the extent of this selectivity, particularly among newly settled recruits. Here we quantified habitat specificity of juvenile coral reef fish at three ecological levels; algal meadows vs. coral reefs, live vs. dead coral and among different coral morphologies. In total, 6979 individuals from 11 families and 56 species were censused along Ningaloo Reef, Western Australia. Juvenile fishes exhibited divergence in habitat use and specialization among species and at all study scales. Despite the close proximity of coral reef and algal meadows (10's of metres) 25 species were unique to coral reef habitats, and seven to algal meadows. Of the seven unique to algal meadows, several species are known to occupy coral reef habitat as adults, suggesting possible ontogenetic shifts in habitat use. Selectivity between live and dead coral was found to be species-specific. In particular, juvenile scarids were found predominantly on the skeletons of dead coral whereas many damsel and butterfly fishes were closely associated with live coral habitat. Among the coral dependent species, coral morphology played a key role in juvenile distribution. Corymbose corals supported a disproportionate number of coral species and individuals relative to their availability, whereas less complex shapes (i.e. massive & encrusting) were rarely used by juvenile fish. Habitat specialisation by juvenile species of ecological and fisheries importance, for a variety of habitat types, argues strongly for the careful conservation and management of multiple habitat types within marine parks, and indicates that the current emphasis on planning conservation using representative habitat areas is warranted. Furthermore, the close association of many juvenile fish with corals susceptible to climate change related disturbances suggests that identifying and protecting reefs resilient to this should be a conservation priority

Behaviourally Mediated Phenotypic Selection in a Disturbed Coral Reef Environment

Natural and anthropogenic disturbances are leading to changes in the nature of many habitats globally, and the magnitude and frequency of these perturbations are predicted to increase under climate change. Globally coral reefs are one of the most vulnerable ecosystems to climate change. Fishes often show relatively rapid declines in abundance when corals become stressed and die, but the processes responsible are largely unknown. This study explored the mechanism by which coral bleaching may influence the levels and selective nature of mortality on a juvenile damselfish, Pomacentrus amboinensis, which associates with hard coral. Recently settled fish had a low propensity to migrate small distances (40 cm) between habitat patches, even when densities were elevated to their natural maximum. Intraspecific interactions and space use differ among three habitats: live hard coral, bleached coral and dead algal-covered coral. Large fish pushed smaller fish further from the shelter of bleached and dead coral thereby exposing smaller fish to higher mortality than experienced on healthy coral. Small recruits suffered higher mortality than large recruits on bleached and dead coral. Mortality was not size selective on live coral. Survival was 3 times as high on live coral as on either bleached or dead coral. Subtle behavioural interactions between fish and their habitats influence the fundamental link between life history stages, the distribution of phenotypic traits in the local population and potentially the evolution of life history strategies

Transcriptomic analysis of the temporal host response to skin infestation with the ectoparasitic mite Psoroptes ovis

<p>Abstract</p> <p>Background</p> <p>Infestation of ovine skin with the ectoparasitic mite <it>Psoroptes ovis </it>results in a rapid cutaneous immune response, leading to the crusted skin lesions characteristic of sheep scab. Little is known regarding the mechanisms by which such a profound inflammatory response is instigated and to identify novel vaccine and drug targets a better understanding of the host-parasite relationship is essential. The main objective of this study was to perform a combined network and pathway analysis of the <it>in vivo </it>skin response to infestation with <it>P. ovis </it>to gain a clearer understanding of the mechanisms and signalling pathways involved.</p> <p>Results</p> <p>Infestation with <it>P. </it>ovis resulted in differential expression of 1,552 genes over a 24 hour time course. Clustering by peak gene expression enabled classification of genes into temporally related groupings. Network and pathway analysis of clusters identified key signalling pathways involved in the host response to infestation. The analysis implicated a number of genes with roles in allergy and inflammation, including pro-inflammatory cytokines (<it>IL1A, IL1B, IL6, IL8 </it>and <it>TNF</it>) and factors involved in immune cell activation and recruitment (<it>SELE, SELL, SELP, ICAM1, CSF2, CSF3, CCL2 </it>and <it>CXCL2</it>). The analysis also highlighted the influence of the transcription factors NF-kB and AP-1 in the early pro-inflammatory response, and demonstrated a bias towards a Th2 type immune response.</p> <p>Conclusions</p> <p>This study has provided novel insights into the signalling mechanisms leading to the development of a pro-inflammatory response in sheep scab, whilst providing crucial information regarding the nature of mite factors that may trigger this response. It has enabled the elucidation of the temporal patterns by which the immune system is regulated following exposure to <it>P. ovis</it>, providing novel insights into the mechanisms underlying lesion development. This study has improved our existing knowledge of the host response to <it>P. ovis</it>, including the identification of key parallels between sheep scab and other inflammatory skin disorders and the identification of potential targets for disease control.</p

Dietary shift in juvenile coral trout (Plectropomus maculatus) following coral reef degradation from a flood plume disturbance

Acute environmental disturbances impact on habitat quality and resource availability, which can reverberate through trophic levels and become apparent in species' dietary composition. In this study, we observed a distinct dietary shift of newly settled and juvenile coral trout (Plectropomus maculatus) following severe coral reef habitat degradation after a river flood plume affected the Keppel Islands, Australia. Hard coral cover declined by similar to 28 % in the 2 yr following the 2010-2011 floods, as did the abundance of young coral trout. Gut contents analysis revealed that diets had shifted from largely crustacean-based to non-preferred prey fishes following the disturbances. These results suggest that newly settled and juvenile coral trout modify their diet and foraging strategy in response to coral habitat degradation. This bottom-up effect of habitat degradation on the diet of a top coral reef predator may incur a metabolic cost, with subsequent effects on growth and survival