Tropical Reef Environments Research Articles

Prudent sessile feeding by the corallivore snail, Coralliophila violacea on coral energy sinks

Convergence of form and function has accompanied the evolution of modular growth in terrestrial plants and colonial marine invertebrates. Part of this convergence is related to the optimal exploitation of resources (space and light) and the ability to translocate energy products from sources to sink sites. Feeding on the energy pathways and energy sinks of terrestrial plants is a well–known phenomenon. Hermatypic corals, the major organisms constructing tropical reef environments, contain photosynthetic algae (zooxanthellae), energetic products of which are translocated towards sink sites located at the coral's growing tips and regenerating areas. Despite the plant–coral convergence in energy pathways and sinks, there has been no evidence to date that coral energy sinks are exploited by coral predators. Gastropods of the genus Coralliophila are found feeding on coral margins, causing small and localized tissue damage. However, the ability of these snails to continue to feed without moving over a long period remains puzzling. Using a 14C labelling technique, we found that colony margins of the stony coral Porites function as major energy sinks. When snails inhabited these sites they incorporated significant amounts of 14C, indicating that they had fed on photosynthetic products translocated from the interior of the colony. Furthermore, when snails aggregate in the interior of the colony, thereby causing large surface injuries, they induce the development of significant new sink sites. This mode of prudent sessile feeding maximizes the efficiency of energy exploitation by the predatory snail, while minimizing tissue damage to the coral. The fact that energy sink sites occur in many coral species suggests that the strategy of sink exploitation for nutrition could also occur in many other marine host–symbiont relationships.

Daily feeding rates in herbivorous labroid fishes

Estimates of daily feeding rates were obtained for two groups of herbivorous labroid fishes, one confined to cold water and the other to tropical reef environments. These were the family Odacidae, represented by Odax pullus from New Zealand waters, (Goat Island Bay: Latitude 36° South; on the northeastern coast of New Zealand) and the family Scaridae, represented by Scarus rivulatus, S. schlegeli and S. sordidus from the northern Great Barrier Reef (Lizard Island; a mid-shelf reef at 14° South latitude). Observations on the odacid were made in 1984 and in 1992, and on the scarids in 1984 and 1988. O. pullus displayed a diurnal feeding pattern in which the rates (expressed as bites min-1) are greatest early in the day. The mean combined feeding rate for three size groups (juveniles, subadults and adults) peaked (average of 2.9 bites) from 06.00 to 08.00 hrs and declined fourfold to a combined average of 0.7 bites min-1 by midday. The greatest mean feeding rate recorded was 3.7 bites min-1, with an overall mean of 1.8 bites min-1. For subadults and adults there were consistent trends in feeding, with subadults feeding at a greater rate than adults and both groups displaying a decline in feeding rate during the day. The change in feeding rate with time of day was statistically significant in both groups. The pattern for juvenile O. pullus was different from that in the two larger size groups in that juveniles did not show a uniform decline in feeding with time of day. For scarids, the daily feeding rate varied by site, but the pattern was similar for all species, characterised by initial low rates increasing to higher but variable levels by midday. The influence of both site of feeding and time of day on feeding rate was confirmed by analysis. The overall mean values for each species were 20.1 bites min-1 for S. rivulatus, 19.7 bites min-1 for S. schlegeli and 14.9 bites min-1 for S. sordidus. For scarids, the peak feeding rates varied from 19.3 to 32.8 bites min-1, with overall rates from 14.9 to 21.1 bites min-1. Estimates of activity and movement patterns during feeding were obtained for O. pullus. Distance moved per unit time was highly variable, 0.1 to 47.5 m min-1, with a mean of 8.5 m min-1 (SD=9.9). Trends in movement among sexes and size classes were obscured by the variable movement patterns of individual fishes.

Plant defense associations in the marine environment

In contrast to terrestrial systems, few positive plant-plant associations have been recorded in tropical reef environments. This study, conducted at Carrie Bow Cay, Belize during 28 March–10 April 1984, provides the first documentation of herbivore escapes for natural combinations of palatable and unpalatable marine plants. For example, there was a highly significant association of several macrophyte taxa (Laurencia poitei, Dictyota spp., Amphiroa fragilissima, Cladophoropsis macromeres, Galaxaura cylindrica, rhodophycean turf) within a 2.0-cm radius of the herbivore-resistant brown alga Stypopodium zonale. Almost twice as many taxa occurred within 10 cm of S. zonale as within 10 cm of an equal number of random Stypopodium-free points, and there were no algal species negatively associated with S. zonale. The association of A. tribulus, L. poitei, Digenia simplex, rhodophycean turf, and Jania adherens with S. zonale provided them a fourfold greater survivorship per 48 h in the presence of grazing activity by fishes (mainly Acanthuridae and Scaridae). Reduced herbivory by fishes on macroalgae associated with S. zonale was not solely a consequence of its structural aspect. Losses of the palatable alga Acanthophora spicifera were significantly greater for thalli spatially remote (30 and 60 cm) from either a real or simulated Stypopodium; however, losses of A. spicifera adjacent to actual Stypopodium plants were significantly less than the losses next to models. The inter-relationships studied here, where an abundant and well-defended plant provides a significant refuge habitat for at least five relatively edible macroalgae, clearly facilitates the survival of certain taxa in the reef system and concomitantly enhances the within habitat diversity. Our findings also suggest an interaction counter to the process of competitive exclusion, since the single predominant plant has a positive rather than negative net effect on the abundances of other species that utilize the same general resources (e.g., light, space, nutrients).

The Fundamental and Realized Niche of a Solitary Population

Previous articleNext article No AccessLetters to the EditorsThe Fundamental and Realized Niche of a Solitary PopulationJonathan RoughgardenJonathan Roughgarden Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 108, Number 960Mar. - Apr., 1974 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/282902 Views: 51Total views on this site Citations: 13Citations are reported from Crossref Copyright 1974 The University of ChicagoPDF download Crossref reports the following articles citing this article:Jason Matthiopoulos Defining, estimating, and understanding the fundamental niches of complex animals in heterogeneous environments, Ecological Monographs 82 (Sep 2022).https://doi.org/10.1002/ecm.1545Paul O’Brien, Eric Vander Wal, Erin L. Koen, Carissa D. Brown, Jenn Guy, Floris M. van Beest, Ryan K. Brook Understanding habitat co-occurrence and the potential for competition between native mammals and invasive wild pigs ( Sus scrofa ) at the northern edge of their range, Canadian Journal of Zoology 97, no.66 (Jun 2019): 537–546.https://doi.org/10.1139/cjz-2018-0156TW Bodey, IR Cleasby, SC Votier, KC Hamer, J Newton, SC Patrick, ED Wakefield, S Bearhop Frequency and consequences of individual dietary specialisation in a wide-ranging marine predator, the northern gannet, Marine Ecology Progress Series 604 (Oct 2018): 251–262.https://doi.org/10.3354/meps12729Shannon L O’Brien, Joseph A Cook, Seth D Newsome Niche differentiation among small mammals of the Alexander Archipelago in southeastern Alaska, Journal of Mammalogy 99, no.11 (Nov 2017): 108–116.https://doi.org/10.1093/jmammal/gyx141Federico Vessella, Javier L?pez-Tirado, Marco Cosimo Simeone, Bartolomeo Schirone, Pablo J. Hidalgo A tree species range in the face of climate change: cork oak as a study case for the Mediterranean biome, European Journal of Forest Research 136, no.33 (May 2017): 555–569.https://doi.org/10.1007/s10342-017-1055-2Richard W. Malizia, Alycia L. Stigall Niche stability in Late Ordovician articulated brachiopod species before, during, and after the Richmondian Invasion, Palaeogeography, Palaeoclimatology, Palaeoecology 311, no.3-43-4 (Nov 2011): 154–170.https://doi.org/10.1016/j.palaeo.2011.08.017Johann Hohenegger, Elza Yordanova Depth-transport functions and erosion-deposition diagrams as indicators of slope inclination and time-averaged traction forces: applications in tropical reef environments, Sedimentology 48, no.55 (Oct 2001): 1025–1046.https://doi.org/10.1046/j.1365-3091.2001.00407.xChristian Wissel Wechselwirkende Arten, (Jan 1989): 62–112.https://doi.org/10.1007/978-3-642-74535-5_3Michael N. Bruton The ecological significance of alternative life-history styles, (Jan 1989): 503–553.https://doi.org/10.1007/978-94-009-2605-9_25Thomas R. Alley Organism-environment mutuality epistemics, and the concept of an ecological niche, Synthese 65, no.33 (Dec 1985): 411–444.https://doi.org/10.1007/BF00869278Edward W. Giering, Abraham Kandel The application of Fuzzy set theory to the modeling of competition in ecological systems, Fuzzy Sets and Systems 9, no.1-31-3 (Jan 1983): 103–127.https://doi.org/10.1016/S0165-0114(83)80012-8Thomas R. Alley Competition theory, evolution, and the concept of an ecological niche, Acta Biotheoretica 31, no.33 (Sep 1982): 165–179.https://doi.org/10.1007/BF01857239R.M. Nisbet, W.S.C. Gurney, M.A. Pettipher Environmental fluctuations and the theory of the ecological niche, Journal of Theoretical Biology 75, no.22 (Nov 1978): 223–237.https://doi.org/10.1016/0022-5193(78)90232-1