In Caribbean coral reefs, many crustacean species associate with sea anemones, but only a few are anemone symbionts. We examined several ecological traits of 3 anemone species (Bartholomea annulata, Condylactis gigantea, Lebrunia danae) and their crustacean symbionts (6 species) on a coral reef at Puerto Morelos, Mexico. On average, C. gigantea was the largest and B. annulata the most abundant of the 3 anemone species. Season did not affect the density distribution of any species, whereas reef zone (back reef, fore reef, reef channels) significantly affected density and mean size of B. annulata and C. gigantea, but only density of L. danae. The probability of harboring crusta ceans increased with anemone size in all species, but varied with reef zone and season in B. annulata only. These patterns may be due to different microhabitat requirements, reproductive strategies, or photosynthetic plasticity of dinoflagellate endosymbionts among hosts, and different flow regimes among reef zones. Alpheus armatus and Ancylomenes pedersoni were strongly associated with B. annulata, and Periclimenes rathbunae with L. danae. Thor amboinensis and Mithraculus cinctimanus occurred more often in C. gigantea, while P. yucatanicus was more evenly associated with the 3 hosts. Only Ancylomenes pedersoni and T. amboinensis occurred in conspecific groups more often than expected by chance. Commensal complexes of up to 3 symbiont species occurred in all host species, with symbionts that typically used different parts of the host coexisting more frequently. These results provide a baseline to assess the potential influence of local and global anthropogenic stressors on anemone−crustacean symbioses.

Shortage of natural crevice shelters may produce population bottlenecks in juvenile Caribbean spiny lobsters (Panulirus argus), a socially gregarious species. We conducted a field experiment to test enhancement of a local population of juvenile P. argus with the addition of artificial shelters ("casitas") that mimic large crevices (1.1 m(2) in surface area and 3.8 cm in height). Changes in density and biomass of juvenile lobsters 15-50 mm carapace length (CL) were assessed with a multiple before-after control-impact (MBACI) analysis. Separate analyses were also conducted on small (15-35 mm CL) and large (35.1-50 mm CL) juveniles to assess size-related effects. First, we carried out 13 lobster surveys on nine fixed 1-ha sites over a shallow reef lagoon ("before" period). Then, we deployed ten casitas in each of five sites and left four sites as controls, and conducted 22 further surveys ("after" period). Deployment of casitas resulted in a sixfold increase in juvenile density (76% contributed by small and 24% by large juveniles) and a sevenfold increase in biomass (40 and 60%, respectively). Capture-recapture results revealed that enhancement was achieved not by promoting individual growth but by increasing survival, persistence, and foraging ranges of small and large juveniles. Casitas both mitigated shortage of natural shelter and increased sociality, allowing for cohabitation of smaller, more vulnerable juveniles with larger conspecifics that have greater defensive abilities. Casitas may help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, typically poor in natural crevice shelters. The use of MBACI and the simultaneous assessment of multiple interrelated response variables may be a powerful analytical approach to test shelter limitation in other species and to examine the function of structural habitat in other systems.

In Bahía de la Ascensión, Mexico, 'casitas' (large artificial shelters) are extensively used to harvest Caribbean spiny lobsters Panulirus argus. After the discovery of a pathogenic virus, Panulirus argus virus 1 (PaV1), in these lobsters, laboratory experiments revealed that PaV1 could be transmitted by contact and through water, and that lobsters avoided shelters harboring diseased conspecifics. To examine these issues in the context of casitas, which typically harbor multiple lobsters of all sizes, we examined the distribution and aggregation patterns of lobsters in the absence/presence of diseased conspecifics (i.e. visibly infected with PaV1) in 531 casitas distributed over 3 bay zones, 1 poorly vegetated ('Vigía Chico', average depth: 1.5 m) and 2 more extensively vegetated ('Punta Allen': 2.5 m; 'Los Cayos': 2.4 m). All zones had relatively high indices of predation risk. Using several statistical approaches, we found that distribution parameters of lobsters were generally not affected by the presence of diseased conspecifics in casitas. Interestingly, however, in the shallower and less vegetated zone (Vigía Chico), individual casitas harbored more lobsters and lobsters were actually more crowded in casitas containing diseased conspecifics, yet disease prevalence was the lowest in lobsters of all sizes. These results suggest that (1) investment in disease avoidance by lobsters is partially modulated by local habitat features, (2) contact transmission rates of PaV1 may be lower in nature than in the laboratory, and (3) water-borne transmission rates may be lower in shallow, poorly vegetated habitats more exposed to solar ultraviolet radiation, which can damage viral particles.

Social behaviour in Caribbean spiny lobsters (Panulirus argus) is mediated by conspecific chemical cues. These lobsters can be attracted to shelters emanating chemical cues from conspecifics but tend to avoid shelters emanating chemical cues from injured conspecifics, dead conspecifics, and conspecifics with visible signs of a potentially lethal disease caused by the pathogenic Panulirus argus virus 1 (PaV1). However, previous studies have not controlled for the presence of PaV1 (i.e. subclinical infection) in grossly “healthy” lobsters, although visible signs of disease do not appear until several weeks after infection. We conducted a controlled experiment using a set of 2 m-long Y-mazes to examine and contrast the response of P. argus lobsters to shelters emanating chemical cues from conspecifics in four different conditions: uninfected, subclinically PaV1-infected (i.e. infected but not diseased), clinically PaV1-infected (i.e. infected and diseased), and dead. Using polymerase chain reaction, we tested for PaV1 in all grossly healthy lobsters and used exclusively uninfected lobsters in intermolt as focal lobsters. Focal lobsters similarly avoided shelters emanating chemical cues from clinically infected (80% avoidance) and from dead conspecifics (85% avoidance), but their response to chemical cues from uninfected and from subclinically infected conspecifics did not differ significantly from random. These results indicate that PaV1-diseased lobsters produce chemical cues that are as repellent to conspecifics as are chemicals emanating from dead conspecifics, and that subclinically infected lobsters either do not emit the repellent chemicals or they do so at sub-threshold levels. However, the nature of the repellent chemicals and whether they originate from the pathogen or the host remains to be determined.

In Bahía de la Ascensión, Mexico, the fishery for spiny lobsters Panulirus argus is based on the extensive use of casitas, large artificial shelters that can harbor the full size range of these highly gregarious lobsters. The discovery of a pathogenic virus in these lobsters (Panulirus argus virus 1, or PaV1) has raised concern about its potential effects on casita-based fisheries. Because in Bahía de la Ascensión visibly infected lobsters represent an immediate loss of revenue, we examined variability in clinical prevalence of PaV1 (percentage of lobsters visibly infected) in thousands of lobsters sampled from the commercial catch at the onset of 3 consecutive fishing years, and from 530 casitas distributed over 3 zones within the bay during 2 fishing and 2 closed seasons. In the commercial catch (lobsters 67 to 147 mm carapace length [CL]), clinical prevalence of PaV1 was low and was not affected by year or sex. In lobsters (9.2 to 115.0 mm CL) that occupied casitas, clinical prevalence of PaV1 varied with sampling season and was always higher in juveniles than in subadults or adults, but was consistently lower in one zone relative to the other 2 zones. The average clinical prevalence of PaV1 in this bay was statistically similar to the average clinical prevalence reported in Cuba, where casitas are also used, and in Florida Bay, USA, where casitas are not used. To date, PaV1 has had no discernible impact on the lobster fishery in Bahía de la Ascensión, suggesting that clinical prevalence is not influenced by the use of casitas per se.