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Zvuloni A.,Israel Nature and Parks Authority | Armoza-Zvuloni R.,Tel Aviv University | Armoza-Zvuloni R.,Interuniversity Institute for Marine science of Eilat | Shaked Y.,Interuniversity Institute for Marine science of Eilat
Marine Ecology Progress Series | Year: 2012

We previously reported the sudden emergence of a disease-like syndrome in which numerous circular white spots were observed in Millepora dichotoma colonies in the Gulf of Aqaba (Zvuloni et al. 2011; Mar Ecol Prog Ser 441:25-32) and termed this phenomenon Multifocal Bleaching (MFB). Carlson (2012; Mar Ecol Prog Ser 463:297-299), based on his observations from Hawaiian coral reefs, suggests that the MFB is caused through foraging by the blenny Exallias brevis. Carlson's suggestion led us to perform new field and laboratory studies to confirm or discount this possibility. We were unable to document biting of the hydrocorals by E. brevis in the field, but our aquarium experiment demonstrated that the white spots are indeed a direct result of the blenny's biting. In addition, we found a strong linkage between the presence of E. brevis and the presence of MFB in M. dichotoma colonies. We accept Carlson's suggestion, which leads to the following questions: (1) Is the sudden emergence of MFB in the Red Sea caused by a sudden surge in the population of E. brevis? (2) Has a change in environmental conditions prompted E. brevis to suddenly begin feeding on M. dichotoma? (3) What will be the long-term impact of E. brevis on populations of M. dichotoma, an important component of shallow reefs in the Red Sea?. © Inter-Research 2012 · www.int-res.com. Source

Berenshtein I.,Ben - Gurion University of the Negev | Berenshtein I.,Interuniversity Institute for Marine science of Eilat | Kiflawi M.,Ben - Gurion University of the Negev | Kiflawi M.,Interuniversity Institute for Marine science of Eilat | And 4 more authors.
PLoS ONE | Year: 2014

Recent studies of the larvae of coral-reef fishes reveal that these tiny vertebrates possess remarkable swimming capabilities, as well as the ability to orient to olfactory, auditory, and visual cues. While navigation according to reef-generated chemicals and sounds can significantly affect dispersal, the effect is limited to the vicinity of the reef. Effective long-distance navigation requires at least one other capacity-the ability to maintain a bearing using, for example, a sun compass. Directional information in the sun's position can take the form of polarized-light related cues (i.e., e-vector orientation and percent polarization) and/or non-polarized-light related cues (i.e., the direct image of the sun, and the brightness and spectral gradients). We examined the response to both types of cues using commercially-reared post-larvae of the spine-cheeked anemonefish Premnas biaculeatus. Initial optomotor trials indicated that the post-larval stages are sensitive to linearly polarized light. Swimming directionality was then tested using a Drifting In-Situ Chamber (DISC), which allowed us to examine the response of the post-larvae to natural variation in light conditions and to manipulated levels of light polarization. Under natural light conditions, 28 of 29 post-larvae showed significant directional swimming (Rayleigh's test p<0.05, R = 0.74±0.23), but to no particular direction. Swimming directionality was positively affected by sky clarity (absence of clouds and haze), which explained 38% of the observed variation. Moreover, post-larvae swimming under fully polarized light exhibited a distinct behavior of tracking the polarization axis, as it rotated along with the DISC. This behavior was not observed under partially-polarized illumination. We view these findings as an indication for the use of sun-related cues, and polarized light signal in specific, by orienting coral-reef fish larvae. © 2014 Berenshtein et al. Source

Zvuloni A.,Tel Aviv University | Zvuloni A.,Interuniversity Institute for Marine science of Eilat | van Woesik R.,Florida Institute of Technology | Loya Y.,Tel Aviv University
PLoS ONE | Year: 2010

Background: The coral reefs of Zanzibar Island (Unguja, Tanzania) encompass a considerable proportion of the global coralreef diversity and are representative of the western Indian Ocean region. Unfortunately, these reefs have been recently subjected to local and regional disturbances. The objectives of this study were to determine whether there are potentially non-random processes forcing the observed coral diversity patterns, and highlight where and at which spatial scales these processes might be most influential. Methodology/Principal Findings: A hierarchical (nested) sampling design was employed across three spatial scales, ranging from transects (≤20 m), stations (<100 m), to sites (<1000 m), to examine coral diversity patterns. Two of the four sites, Chumbe and Mnemba, were located within Marine Protected Areas (MPAs), while the other two sites, Changuu and Bawe, were not protected. Additive partitioning of coral diversity was used to separate regional (total) diversity (γ) into local a diversity and among-sample β diversity components. Individual-based null models were used to identify deviations from random distribution across the three spatial scales. We found that Chumbe and Mnemba had similar diversity components to those predicted by the null models. However, the diversity at Changuu and Bawe was lower than expected at all three spatial scales tested. Consequently, the relative contribution of the among-site diversity component was significantly greater than expected. Applying partitioning analysis for each site separately revealed that the within-transect diversity component in Changuu was significantly lower than the null expectation. Conclusions/Significance: The non-random outcome of the partitioning analyses helped to identify the among-sites scale (i.e., 10's of kilometers) and the within-transects scale (i.e., a few meters; especially at Changuu) as spatial boundaries within which to examine the processes that may interact and disproportionately differentiate coral diversity. In light of coral community compositions and diversity patterns we strongly recommend that Bawe be declared a MPA. © 2010 Rutledge, Stewart. Source

Armoza-Zvuloni R.,Israel Oceanographic And Limnological Research | Armoza-Zvuloni R.,Tel Aviv University | Armoza-Zvuloni R.,Interuniversity Institute for Marine science of Eilat | Kramarsky-Winter E.,Tel Aviv University | And 3 more authors.
Biology of Reproduction | Year: 2014

Reproductive development of anthozoans reveals wide range of breeding strategies. Here, we report the occurrence of trioecy in the sea anemone Aiptasia diaphana (co-occurrence of males, females, and hermaphrodites), which so far was well documented only in plants. Age-homogeneous populations were obtained from pedal lacerates (asexual propagules) and cultured under control conditions. Careful documentation of growth, gamete morphology, and vertebrate-like steroid (i.e., progesterone, testosterone, and estradiol) levels were carried out over a 9-wk period between 4 and 12 wk postlaceration (wpl). First phenotypic signs of gametes development were observed in 6-wk-old anemones, pointing to the differentiation of males and hermaphrodites. While the males exhibited cellular progression of spermatogenesis, the hermaphrodites underwent a process of sex allocation, giving rise to male, female, and hermaphrodite phenotypes. Testosterone levels were relatively high prior to gamete appearance (4 wpl) and later on during gamete maturation (10 wpl). Conversely, estradiol levels steadily increased from 6 to 10 wpl, reaching their peak concomitant with oocyte maturation. Interestingly, increased oocyte atresia incidences were recorded during 9-12 wpl, coinciding with declining levels of steroid hormones. These results point to a strong similarity between the activity of sex steroids in vertebrates and that of vertebrate-like sex steroids on critical stages of A. diaphana's sexual differentiation and gametogenic cycle. The reproductive characteristics of A. diaphana make this anthozoan an important model species for the study of evolutionary drivers and processes underlying sexual development. © 2014 by the Society for the Study of Reproduction, Inc. Source

Barth P.,CNRS Insular Research Center and Environment Observatory | Barth P.,CNRS Lyon Institute of Functional Genomics | Berenshtein I.,Ben - Gurion University of the Negev | Berenshtein I.,Interuniversity Institute for Marine science of Eilat | And 8 more authors.
Vie et Milieu | Year: 2015

As it is unlikely that successful settlement is solely a matter of chance (i.e. to find a suitable habitat), one of the greatest challenges facing the fish larvae is how to locate the relatively rare patches of coral reef habitat on which they settle and ultimately reside as adults. The answer must lie partly in the sensory modalities of fishes at settlement. Habitat selection is only possible if fish larvae could detect some environmental cues to select a suitable reef habitat at settlement. The present review aims at providing the latest works dealing with information perception in coral reef fish larvae at settlement. Two decades ago, it was generally assumed that larval behaviors and sensory abilities at settlement were considered too feeble to significantly affect dispersal outcomes. Several recent studies showed that recognition of suitable reef habitats by fish larvae at settlement is based on a combination of visual, chemical and acoustic cues. The first part of our review shows the main advances in the knowledge of visual, chemical and acoustic cues used by fish larvae to detect an island, a reef, a micro-habitat, a conspecific or some predators. The second part of our review deals with the effect of imprinting and/or innate capabilities. The third part focuses on the different cues used at different scales and underlines some contradictory results about the distance of transmission and detection of chemical and acoustic cues in coral reefs. Finally, as global and regional environmental changes have stressed coral reefs to such an extent that they are either destroyed or in decline, the fourth part presents the effects of both anthropogenic and environmental stressors on information perception and response capacities in coral reef fish larvae. If polluted seawater disrupts the larval abilities to find a suitable reef habitat, fish larvae may spend more time in the planktonic environment, resulting in increased energetic costs and prédation risk, and consequently a lower larval settlement. We hypothesise that as the stability offish communities is dependent, in part, on the stability of social interactions, the disruption of "larvae-habitat relationships" can have major consequences for larval settlement into adult population with further repercussions for the ecosystem as a whole. Overall, larval settlement of coral reef fish is an excellent example of the complexity of interactions between an organism and its environment as without perceiving environmental cues, fish larva would have very little chance of selecting a suitable reef habitat. Moreover, understanding the relationship between reef state and settlement potential will allow management planning for the maintenance of coral reefs that are increasingly degraded. Source

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