The Influence of Shelter, Conspecifics, and Threat of Predation on the Behavior of the Long-Spined Sea Urchin (Diadema Antillarum)
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Old Dominion University ODU Digital Commons Biological Sciences Faculty Publications Biological Sciences 11-2014 The nflueI nce of Shelter, Conspecifics, and Threat of Predation on the Behavior of the Long-Spined Sea Urchin (Diadema antillarum) Meredith D. Kintzing Old Dominion University Mark J. Butler IV Old Dominion University, [email protected] Follow this and additional works at: https://digitalcommons.odu.edu/biology_fac_pubs Part of the Marine Biology Commons Repository Citation Kintzing, Meredith D. and Butler, Mark J. IV, "The nflueI nce of Shelter, Conspecifics, and Threat of Predation on the Behavior of the Long-Spined Sea Urchin (Diadema antillarum)" (2014). Biological Sciences Faculty Publications. 4. https://digitalcommons.odu.edu/biology_fac_pubs/4 Original Publication Citation Kintzing, M.D., & Butler, M.J. (2014). The influence of shelter, conspecifics, and threat of predation on the behavior of the long-spined sea urchin (Diadema antillarum). Journal of Shellfish Research, 33(3), 781-785. doi: 10.2983/035.033.0312 This Article is brought to you for free and open access by the Biological Sciences at ODU Digital Commons. It has been accepted for inclusion in Biological Sciences Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. The Influence of Shelter, Conspecifics, and Threat of Predation on the Behavior of the Long-Spined Sea Urchin (Diadema antillarum) Author(s): Meredith D. Kintzing and Mark J. Butler IV Source: Journal of Shellfish Research, 33(3):781-785. Published By: National Shellfisheries Association DOI: http://dx.doi.org/10.2983/035.033.0312 URL: http://www.bioone.org/doi/full/10.2983/035.033.0312 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. 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THE INFLUENCE OF SHELTER, CONSPECIFICS, AND THREAT OF PREDATION ON THE BEHAVIOR OF THE LONG-SPINED SEA URCHIN (DIADEMA ANTILLARUM) MEREDITH D. KINTZING AND MARK J. BUTLER IV* Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529 ABSTRACT The interplay of competition and predation often affects prey habitat use, which may concentrate prey in safer areas with indirect consequences on their foraging efficiency and the effects of their foraging on the community. Predation is intense on coral reefs where competition for limited space and food is severe. The sea urchin Diadema antillarum, an inhabitant of Caribbean coral reefs, uses crevice shelters and often aggregates with conspecifics for protection against predators, which appears to reflect a conflicting balance between group defense versus competition for limited shelter. A series of laboratory experiments was used to determine how the availability of shelter, conspecifics, and chemical odors from conspecifics and a predator—the spotted spiny lobster (Panulirus guttatus)—affect D. antillarum shelter use. The long-spined sea urchin D. antillarum responded strongly to the odor of conspecifics and the lobster predator. Absent the threat of predation, D. antillarum compete for shelter and avoid shelters bearing the scent of other urchins. But, D. antillarum readily shared shelters and preferred the scent of conspecifics when exposed to lobster odors. Thus, efforts to enhance the recovery of D. antillarum populations on degraded reefs must strike a balance between minimizing their mortality from predation and increasing habitat complexity, which not only increases shelter for D. antillarum, but also their predators. KEY WORDS: sea urchin, Diadema antillarum, habitat complexity, ideal free distribution, predation threat, coral reefs INTRODUCTION mediating habitat selection and resource use (Heithaus et al. 2007, Heithaus et al. 2009). This ecological trade-off is common Predators can shape the taxonomic structure of animal in tropical marine ecosystems. communities and control the abundance of prey (Hairston Predation is intense in low-latitude, high-diversity ecosys- et al. 1960, Paine 1966). In turn, prey have evolved physical tems such as coral reefs (Bertness et al. 1981, Menge & (Hoverman et al. 2005), chemical (Bolser & Hay 1996), and Lubchenco 1981, Bolser & Hay 1996,) where competition for behavioral adaptations that limit their vulnerability to pre- limited space and food is also severe (Jackson & Buss 1975, dation (Trussell et al. 2003, Smee & Weissburg 2008) and, in Williams 1981, Connell et al. 2004). The sea urchin Diadema some cases, combine these strategies to reduce predation risk. antillarum, which inhabits the coral reefs of the tropical For example, the sharp, sometimes toxic spines of sea urchins Caribbean, offers a case in point. It uses crevice shelters and provide both physical and chemical deterrence to predation, but often aggregates with conspecifics for protection against pred- urchins have also evolved a number of defensive behaviors to ators (Carpenter 1984, Lee 2006, Miller et al. 2007). This may avoid predators (Vadas & Elner 2003). Sea urchins have well reflect the conflicting balance between group defense for pro- developed olfactory senses, and many species flee or curtail tection versus competition for limited quality habitats. The sea feeding in response to chemical cues produced by predators and urchin D. antillarum was used as a model organism in a series of injured conspecifics (Snyder & Snyder 1970, Freeman 2006, laboratory experiments to examine how the availability of Matassa 2010). Antipredatory adaptations such as these pro- shelter and conspecifics affect D. antillarum behavior in the vide obvious evolutionary advantages to prey, but often come presence and absence of a common predator, the spotted spiny at a cost, such as reduced foraging or restriction to suboptimal lobster (Panulirus guttatus). habitats where their growth or fecundity is compromised by overcrowding (Katz & Dill 1998). This Faustian dilemma—enhanced competition in resource- MATERIALS AND METHODS poor habitats versus greater risk of predation—is embodied in All the experiments described were conducted at the Goshen FretwellÕs ideal free distribution theory (Fretwell & Lucas College Marine Laboratory on Long Key, Florida, from July 1970), an outgrowth of optimal foraging theory first developed 2008 through October 2009. Unless otherwise noted, experi- to explore how trade-offs in competitive ability and predation ments were conducted in 200-L flow-through seawater tanks risk impact resource use (MacArthur & Pianka 1966). Although and ran for approximately 24 h under natural photoperiod and FretwellÕs original theory examined how organism density, ambient seawater temperatures (range, 27–31°C) and salinity a proxy for competition, affects habitat quality, others have (range, 32–36 ppt). Experimental setups that included head extended the idea to examine how the threat of predation tanks had natural, sand-filtered seawater flowing to a 20-L head concentrates prey in safer areas and thus indirectly impacts tank. Seawater then flowed from each head tank at approxi- habitat quality (Grand & Dill 1999, Heithaus et al. 2007, mately 1 L/min through plastic airline tubing to a shelter below. Heithaus et al. 2009). Many of these studies confirm ConnellÕs All experimental shelters were constructed with 3 stacked idea (Connell 1975) that the threat of predation usually trumps masonry bricks soaked previously in seawater. Sea urchins the disadvantages of increased interspecific competition in (Diadema antillarum) and lobsters (Panulirus guttatus) used in the experiments were collected from nearby reef habitats by *Corresponding author. E-mail: [email protected] divers and returned to those reefs at the conclusion of these DOI: 10.2983/035.033.0312 studies. 781 782 KINTZING AND BUTLER Effect of Conspecifics on Diadema Shelter Choice The sea urchin Diadema antillarum also avoided shelters from which flowed a conspecific odor only (n ¼ 21, P ¼ 0.034; Three separate experiments were conducted to investigate Fig. 1B). The size of D. antillarum did not affect these results; the effects of conspecifics on shelter use by Diadema antillarum; the 5 individuals that chose the shelter with a conspecific odor specifically, shelter choice was tested with (1) conspecifics present spanned the size range of the D. antillarum tested. This result is and shelter not limited, (2) conspecific odors present and shelter consistent with the outcome of the previous experiment (see Fig. not limited, and (3) conspecific odors present and shelter lim- 1A) and demonstrates that D. antillarum use olfaction to detect ited. To determine whether the presence of a conspecific affects and avoid conspecifics. shelter selection