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Achelata (Palinuridae and Scyllaridae) have a flat, transparent, long-lived planktonic larva called phyllosoma, which comprises multiple stages and has a duration from a few weeks (some scyllarids) to &gt, 20 months (some palinurids). The larval development of many Achelata occurs in oceanic waters, where conventional plankton nets usually collect the early- to mid-stages but not the later stages, which remain poorly known. We examined the diversity and distribution of mid- and late-stage phyllosomata in the oceanic waters of the Mexican Caribbean, where the swift Yucatan Current is the dominant feature. The plankton samples were collected at night with a large mid-water trawl in autumn 2012 (55 stations) and spring 2013 (34 stations). In total, we obtained 2599 mid- and late-stage phyllosomata (1742 in autumn, 857 in spring) of five palinurids (Panulirus argus, Panulirus guttatus, Panulirus laevicauda, Palinurellus gundlachi, Justitia longimana) and three scyllarids (Parribacus antarcticus, Scyllarides aequinoctialis, Scyllarus chacei). Overall, the mid-stages were ~2.5 times as abundant as the late stages. The palinurids far outnumbered the scyllarids, and P. argus dominated over all the other species, followed at a distance by P. guttatus. The densities of all the species were generally low, with no clear spatial pattern, and the phyllosomata assemblage composition greatly overlapped between seasons. These results suggest the extensive mixing of the organisms entrained in the strong Yucatan Current, which clearly favors the advection of the phyllosomata in this region despite the presence of some local sub-mesoscale features that may favor short-term retention.

There is little information on the early life history of the spotted spiny lobster Panulirus guttatus (Latreille, 1804), an obligate reef resident, despite its growing importance as a fishery resource in the Caribbean and as a significant predator. We cultured newly-hatched P. guttatus larvae (phyllosomata) in the laboratory for the first time, and the growth, survival, and morphological descriptions are reported through 324 days after hatch (DAH). Phyllosomata were cultured at 25 °C in a flow-through seawater system within a series of custom 80 l plankton-kreisel tanks and provided with ongrown Artemia and mussel gonad. Mean body length (BL) of phyllosomata was 1.70 mm (N = 10) at hatch and increased linearly to 22.20 mm at 226 DAH (N = 3). Morphological characters from a total of 164 sampled phyllosomata were ascribed to nine distinct developmental stages (stages I-IX), and described and illustrated. Although no final stage phyllosomata (stage X) were obtained, the BL in the final stage was extrapolated at 39.6 mm using a Gompertz function, expressing the relationship between phyllosoma stages and BL. The total duration of phyllosomata for P. guttatus was estimated at 410 d, with the 5th and 95th percentiles at 334 and 526 d, respectively. Our data suggest that P. guttatus has a larger body size in the final larval stage and a substantial pelagic larval duration compared with other related panulirid lobsters in its geographic range. The described morphological and biological attributes associated with the early-life history for this species can inform future studies, and add value to models of distribution and population connectivity.

Crustaceans suffer from diseases that can alter their survival and ecology with additional economic consequences for fisheries and aquaculture. Many parasites have been described from crustaceans and with the advent of novel technologies such as next generation sequencing, the discovery of novel parasites has become increasingly efficient. Molecular techniques are beginning to surpass more conventional tools for parasite discovery, but they typically do not provide information on pathology. Histopathology remains one of the least expensive methods for parasite discovery and allows for both detection of parasites and descriptions of the pathology they cause. When used in concert with modern molecular and electron microscopy techniques, the approach is powerful; however, there are few informational tools for the interpretation of histological slides from crustaceans. Those available do not provide comprehensive images of all organs and early works were limited to lower resolution than currently available. More recent texts provide in-depth details of infection in histological section, but few provide images of healthy material or describe a baseline from which to compare. Here, we provide a series of image plates derived from histologically processed tissues from three palinurid lobsters: Panulirus argus, Palinurus elephas and Panulirus guttatus. Histology from these lobsters shows high visual similarity in all tissue types. We provide a histological atlas of healthy tissue that can be used as a baseline resource for pathobiologists working on these common species (and related crustaceans) and we discuss how disease may result in visual aberrations to these tissues.

Caribbean coral reefs are undergoing massive degradation, with local increases of macroalgae and reduction of architectural complexity associated with loss of reef-building corals. We explored whether reef degradation affects the feeding ecology of two co-occurring spiny lobsters: Panulirus guttatus, which is an obligate reef-dweller, and Panulirus argus, which uses various benthic habitats including coral reefs. We collected lobsters of both species from the back-reef zones of two large reefs similar in length (~1.5 km) but differing widely in level of degradation, at the Puerto Morelos Reef National Park (Mexico). We measured the carapace length (CL) and weight (W) of lobsters, estimated three condition indices (hepatosomatic index, HI; blood refractive index, BRI; and W/CL ratio), and analyzed their stomach contents and stable isotope values (15N and 13C). All lobsters tested negative for the presence of the virus PaV1, which can affect nutritional condition. Stomach contents yielded 72 animal taxa, mainly mollusks and crustaceans, with an average of 35 taxa per species per reef, but with much overlap. In P. guttatus, CL, HI, BRI, and W/CL did not vary with reef, but mean isotopic values did. The isotopic niche of P. guttatus showed little overlap between reefs, reflecting differences in local carbon sources and underlining the habitat specialization of P. guttatus, which exhibited a higher trophic position on the more degraded reef. Overall, the trophic position of P. guttatus was higher than that of P. argus. In P. argus, none of the variables differed between reefs and the isotopic niche was wide and with great overlap between reefs, reflecting the broader foraging ranges of P. argus compared to P. guttatus. Additional isotopic values from 16 P. argus caught at a depth of 25 m in the fore reef suggest that these larger lobsters forage over different habitats and have a higher trophic position than their smaller conspecifics and congeners from the back reef. The feeding ecology of P. argus appears to be less influenced by coral reef degradation than that of P. guttatus, but our results suggest a buffering effect of omnivory against habitat degradation for both lobster species.

Throughout the Wider Caribbean Region, the spotted spiny lobster, Panulirus guttatus (Latreille, 1804), dwells and forages exclusively in coral reef habitat after post-larval settlement, whereas its sympatric species, the Caribbean spiny lobster, Panulirus argus (Latreille, 1804), undergoes ontogenetic habitat shifts, with smaller individuals dwelling in reef lagoon habitats and larger individuals dwelling in reef habitats, but exhibiting broad foraging ranges. Stomach content, and carbon and nitrogen stable isotopes analyses were used to examine dietary partitioning between co-occurring P. guttatus and reef-dwelling P. argus in a coral reef system off Mexico. Both species fed on a wide variety of invertebrates, but mollusks contributed more to the diet of P. guttatus and crustaceans to the diet of P. argus. The two species had different ranges of isotopic composition and each filled a unique trophic position within the local food web. A Bayesian mixing model revealed a distinct contribution of different food sources to the diet of these lobsters. Reef herbivores were the primary food source for P. argus and an important food source for P. guttatus, but the latter also consumed more carnivores, resulting in a higher trophic position relative to P. argus. The isotopic niche space, delineated by means of bivariate ellipses, exhibited no overlap between species, and P. argus exhibited a significantly larger niche area than P. guttatus. These results suggest that, in addition to a differential use of habitat resources, a differential use of food resources facilitates the local coexistence of these two congeners.

Panulirus guttatus is a sedentary spiny lobster that exhibits cryptic behaviour and a low degree of gregariousness. Because these lobsters are obligate coral reef-dwellers and avoid sandy expanses, they are potentially distributed in relatively small, discrete populations with variable social contexts, which can strongly influence the expression of aggression. The present study examined the relative importance of sex, size, and the number of missing limbs in the shelter-related aggressive behaviour of replicated groups of four lobsters that differed in social context (i.e. same-sex and mixed-sex groups). Each group was held in a seawater tank with a single artificial cave-like shelter. The interior of the cave was video-recorded for 72 h and the number of aggressions performed by each individual was quantified in a 10-min segment of video per hour. Most aggressions were related to occupancy of the shelter inner space and tended to end when individuals were sufficiently spaced out. In general, per-capita rates of aggression were higher at night and size was an important predictor of aggressiveness among individuals of the same sex. Males were substantially more aggressive than females, but the number of missing limbs significantly impacted the degree of aggressiveness in males. In mixed-sex groups, fewer aggressions occurred when the largest individual was a male than when it was a female, suggesting that it may take longer for smaller males to assert themselves. Our results provide insights into some potential consequences of increase in fishing pressure and loss of habitat complexity in Caribbean reefs for the social behaviour and population dynamics of these lobsters.

Coexistence of closely related species may be promoted by niche differentiation or result from interspecific trade-offs in life history and ecological traits that influence relative fitness differences and contribute to competitive inequalities. Although insufficient to prove coexistence, trait comparisons provide a first step to identify functional differences between co-occurring congeneric species in relation to mechanisms of coexistence. Here, a comparative review on life history and ecological traits is presented for two pairs of co-occurring species of spiny lobsters in the genus Panulirus: Panulirus gracilis and Panulirus inflatus from the Eastern Central Pacific region, and Panulirus argus and Panulirus guttatus from the Caribbean region. Panulirus gracilis and Panulirus inflatus have similar larval, postlarval, and adult sizes and a similar diet, but differ in degree of habitat specialization, fecundity, and growth rate. However, little is known on behavioral traits of these two species that may influence their competitive abilities and susceptibility to predators. The more abundant information on Panulirus argus and Panulirus guttatus shows that these two species differ more broadly in degree of habitat specialization, larval, postlarval and adult sizes, diet, fecundity, growth rate, degree of sociality, defense mechanisms, susceptibility to predators, and chemical ecology, suggesting a greater degree of niche differentiation between Panulirus argus and Panulirus guttatus than between Panulirus gracilis and Panulirus inflatus. Whether the substantial niche differentiation and apparent interspecific trade-offs between Panulirus argus and Panulirus guttatus relative to Panulirus gracilis and Panulirus inflatus reflect an earlier divergence of the former pair of species in the evolution of the genus constitutes an intriguing hypothesis. However, whether or not post-divergence evolution of each species pair occurred in sympatry remains uncertain.

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 shelte...

Sea urchins, important herbivores in marine ecosystems, are strongly impacted by both the direct and indirect effects of predation, and the long-spined sea urchin Diadema antillarum is no exception. Once abundant on Caribbean coral reefs, D. antillarum populations were decimated by disease in the early 1980s, and only where their natural predators have been over-fished has D. antillarum recovery been observed. Spiny lobsters (Palinuridae) are predators of sea urchins, and although there are several species of spiny lobster in the Caribbean, only the spotted spiny lobster Panulirus guttatus is restricted to coral reefs where D. antillarum dwells. We investigated the direct and indirect impacts of P. guttatus on D. antillarum mortality, foraging, and behavior in a series of laboratory experiments. We found that P. guttatus prey on D. antillarum, especially small urchins. D. antillarum also consumed significantly less algae in the presence of P. guttatus and fled when exposed to the odor of P. guttatus but apparently not the scent of the Caribbean spiny lobster P. argus. The altered foraging and avoidance behaviors displayed by D. antillarum are strong evidence that predation by P. guttatus has played an important, but underappreciated, role in the evolutionary history of D. antillarum and perhaps its recovery on Caribbean coral reefs.

Mate choice by females is influenced by male size, resource provisioning and other proxies for male quality. In decapod crustaceans, mating dynamics are complicated by size-dependent sperm limitation associated with unusually low sperm :egg ratios. We explored how mate size influences mating dynamics in the spotted spiny lobster (Panulirus guttatus), a philopatric species that dwells on shallow and often isolated coral reefs in the Caribbean where choice of mates can be limited. We varied the availability and size of male and female lobsters in a series of laboratory experiments and then quantified courtship behaviour, mate choice and fertilization success of each mating. We found that large males initiated most interactions with other males and won 99% of those encounters. Large males were also more successful in garnering mates, but males of all sizes attempted to mate with all sizes of females. Females nearly always (92% of trials) chose males larger than themselves. However, if large males we...

Abstract Spotted spiny lobsters, Panulirus guttatus, are small, obligate reef-dwellers that exhibit a highly sedentary lifestyle and a low tendency to aggregate with conspecifics, and that reproduce asynchronously year-round. Individual females can produce multiple clutches per year but have a short receptivity per clutch. As in most spiny lobsters, females of P. guttatus mate only once per clutch and resist further mating attempts, features that may favour development of female mate choice but limit the potential for sperm competition. We separately examined mate choice by large and small mature females through laboratory experiments that controlled for effects of male–male competition, quality of shelter, and mere social attraction. Only large females expressed preference for larger males relative to their own size, suggesting that only large females that mate with small males risk sperm limitation on fecundity success. In couples that mated, males deposited rather small, thinly spread spermatophores on the sterna of females. Spermatophore area (considered as a proxy measure of sperm content) increased with male size and showed no relationship with female size, suggesting that males of P. guttatus have a short sperm-recovery period or do not exhibit strategic sperm allocation in a non-competitive context. A comparison of average sperm allocation between P. guttatus and its sympatric species, P. argus (a much larger, highly mobile, and highly social species with more seasonal reproductive periods and a longer receptivity of females per clutch), suggests that males of P. guttatus allocate proportionally less sperm to females, on average, than males of P. argus do. According to predictions of across-species risk models, this result suggests that males of P. guttatus perceive lower average levels of sperm competition risk than males of P. argus do, implying that different Panulirus species may exhibit different mating strategies in accordance with their particular life-history and sociobiological traits.

Marine habitats are naturally patchy and anthropogenic disturbance can further fragment them. Many marine animals are sessile as adults or obligate inhabitants of particular habitats, so populations living in isolated patches of habitat are linked largely by dispersal of planktonic larvae. Theoretically, larvae are more likely to find and settle into large patches of habitat than small patches, thus small habitat patches may experience a more discontinuous supply of recruits resulting in small populations with unusual size- or age-structures or odd sex ratios — conditions where Allee effects on reproductive success are likely. We tested this hypothesis for the Caribbean spotted spiny lobster ( Panulirus guttatus ), an obligate inhabitant of coral patch reefs whose mating dynamics are size-dependent. We found that P. guttatus were less abundant on small reefs where their size structure and per capita reproductive success were significantly more variable, particularly among large females that are susceptible to sperm limitation that diminishes fertilization rates. These results are indicative of Allee effects and provide a mechanistic understanding of how size-dependent mating dynamics influence reproductive success in ways that alter population dynamics in patchy habitats.

Den sharing by conspecific spiny lobsters (aggregation) is modulated by chemical attraction but may confer several, not necessarily mutually exclusive, antipredator byproduct benefits: a “guide effect”, which only benefits the individual attracted to a sheltered conspecific; a “dilution effect”, which reduces per-capita risk of predation simply through aggregation; or active “group defense”. Each potential benefit has a different set of predictors (relationships between aggregation and conspecific or predator densities), but conflicting results could suggest the simultaneous operation of more than one benefit. These predictions were tested for coexisting Panulirus guttatus (a reef-obligate) and Panulirus argus (a temporary reef-dweller) using data collected during 11 surveys on fixed sites over a coral reef in Mexico. P. guttatus greatly outnumbered P. argus, but P. argus showed a greater tendency to aggregate. All three benefits of den sharing operated for the more social P. argus, with “group defense” being of the most benefit for larger individuals, and the “guide” and “dilution” effects for smaller individuals recently immigrating into the reef habitat and sharing dens with larger conspecifics. P. guttatus did not display “group defense” and its aggregations appeared to be modulated by the interplay between attraction and aggressive behaviors. This species relied more on solitary crypticity, especially at larger sizes, but appeared to benefit from a “guide effect” at high conspecific densities. In experimental tanks, each species tended to aggregate when tested separately, but when tested jointly, aggregation among P. guttatus was significantly reduced. The experimental results reflect the differential patterns of aggregation between the fore-reef, where P. guttatus dominated, and the back-reef, where coexistence of both species was greater.

Summary 1 Overfishing has had detrimental impacts on many marine populations. However, measurements of the effect of exploitation are often confounded by intersite differences in habitat quality. 2 To assess the effects of fishing and habitat quality on spotted spiny lobster Panulirus guttatus, the target of a luxury fishery in the Caribbean, lobster populations were assessed on 12 reefs around Anguilla, British West Indies. Habitat quality was measured by the availability of foraging habitat. Fishing intensity was estimated through interviews with fishers. 3 Spotted spiny lobster densities were significantly higher on reefs with good-quality habitat than on poorer-quality reefs. However, mean lobster size remained constant regardless of habitat quality. 4 In contrast, lobsters were on average smaller in heavily fished than in unfished areas because of the removal of the largest size classes by fishers. Changes in densities as a result of fishing could not be detected, and there was no interaction between fishing pressure and habitat quality. 5 The lack of an observable effect of fishing on lobster population densities may be because fishers more intensively target high-quality habitats. Fishing has probably reduced lobster densities on high-quality reefs to a greater extent than on low-quality reefs, but the high productivity of good-quality sites is still sustaining more intense fishing. 6 Synthesis and applications. The importance of habitat quality in sustaining P. guttatus populations in the face of intense exploitation suggests that management efforts should be aimed at enhancing reef health. The latter may be achieved through the establishment of no-take areas on good-quality reefs. Such actions should, however, be expected to generate conflicts with stakeholders because these reefs are currently those most heavily exploited.

The notion, previously generated from laboratory experiments, that the local coexistence of spiny lobsters Panulirus guttatus and Panulirus argus on Caribbean reefs may be promoted by a differential use of shelter resources and/or vulnerability to predators was explored in a coral reef in Mexico. Multiple regressions with data collected on 11 occasions on fixed back-reef and fore-reef sites suggested that the densities of the congener, other crevice-dwellers, and predators did not significantly affect the density of P. argus in either reef zone, or of P. guttatus on the back-reef, where coexistence of both lobster species was greatest. In contrast, there was a significant negative relationship between predators and the density of P. guttatus on the fore-reef, where this species was dominant. Congeneric cohabitation in dens was less than expected by chance, but this pattern may reflect a differential use of shelter resources rather than interspecific competition. P. guttatus was more prevalent in dens over the middle and upper third of the reef profile, and P. argus over the lower and middle third of the reef profile. Whether individuals cohabited with conspecifics, congeners, or resided solitarily, P. guttatus was more prevalent at the walls and/or ceiling and P. argus on the floor of dens. This differential use of shelter resources may be related to the differential vulnerability to predators, which may have promoted local coexistence of these congeners in reef habitats.

Chemical response to conspecific scents mediate aggregations in some species of spiny lobsters, but patterns of codenning of adult lobsters in their natural habitats vary widely. This is so for Panulirus guttatus, a small, sedentary, obligate reef‐dwelling species with a protracted, almost year‐round reproductive season. We hypothesised that changes in patterns of aggregation may vary with the intensity of reproductive activity in the population, which in turn may cause changes in responses to conspecific scents. To test this hypothesis, we conducted three laboratory experiments with Y‐mazes to test for seasonal variations in gender‐related and size‐related response to conspecific scents in mature P. guttatus. When reproductive activity (RA) was high (experiment High‐RA, 67.4% reproductive females), males responded significantly to scents of conspecifics of both genders, but females only to the scent of females. When reproductive activity had not yet reached its yearly lowest point (experiment Me...

Panulirus guttatus is a sedentary spiny lobster that dwells in the coral reef habitat. We conducted an exploratory study to describe the within-shelter behaviour of groups of 4–6 individuals of P. guttatus in simulated communal dens deployed in tanks. Lobsters displayed a diel within-shelter activity rhythm, with a peak shortly before dawn due to an increase in agonistic interactions among sheltered individuals. In a single-chamber cave, aggressions resulted in the constant rearrangement of individuals in the den, related to their preference to cling to the walls. In a triple-chamber cave, the largest male often defended one chamber, but the remaining individuals tended to aggregate in one of the other two chambers during the day. These trends suggest that P. guttatus is a gregarious lobster, but that this gregariousness is influenced by the amount of available shelters and by temporary, size-related social hierarchies. This hypothesis should be tested with fully replicated experiments to help understand ...

Palinurid lobsters are being exploited with increasing intensity in coral reef ecosystems, but marine protected areas may play a key role in preventing overfishing and local extinctions. In order to define the spatial requirements for protection, we compared the spatial and temporal patterns in distribution, density, biomass, size structure, and reproductive seasonality of Caribbean spiny lobsters Panulirus argus and the congeneric spotted lobsters P. guttatus on coral patch reef, forereef, and deep reef habitat at Glover's Reef, Belize. The relative impact of fishing on P. argus was also examined in an isolated marine reserve and adjacent fished habitats, in comparison with the relatively unfished distribution of P. guttatus. Over a 5-year period, both species co-occurred in all major reef habitats, but aspects of their population dynamics differed markedly due to both habitat and fishing effects. All size classes of spiny lobsters P. argus occupied shallow patch reefs, but large adults were predominant on the deep wall reef. Panulirus guttatus also occupied patch reefs in the lagoon, but spur-and-groove forereef appeared to be the primary habitat of this species. Density and exploitable (adult) biomass of P. argus increased significantly over time in the protected patch reef habitat of the lagoon but remained stable on deep reef habitat. The biomass of spotted lobsters P. guttatus in all habitats was at least an order of magnitude less than that of exploitable P. argus. Reproductive activity by both species was evident most of the year in all habitats, but breeding P. argus females were concentrated on the deep reef. Commercial fisheries for spotted lobsters P. guttatus are currently being considered for development, but data from this and other studies suggest that such a fishery may be relatively unproductive and may lead to rapid localized extinctions. Spiny lobsters P. argus used a variety of coral reef habitats, but spotted lobsters P. guttatus were habitat specialists restricted to shallow reef habitat. The protection needs of both species are similar in one aspect: large protected areas. However, P. argus required large areas with heterogeneous habitats including coral reefs and seagrass beds, whereas P. guttatus required large areas of coral reef habitat.

Panulirus guttatus (Latreille, 1804) is a sedentary, non-migratory species of spiny lobster that lives in the coral reef habitat throughout its benthic life. Homing and orientation of P. guttatus were investigated through experimental displacements of individual lobsters. Lobsters were caught in fixed traps deployed around three coral patches along a reef tract in northern Quintana Roo, Mexico. A total of 145 adult lobsters were tagged and individually released in one of four compass directions corresponding to the following sites as related to their home reef patches: in the reef lagoon (310?, ~W), along the axis of the reef tract (20?, ~N, or 200?, ~S) and in the fore-reef (100?, ~E). In each direction, individuals were displaced over 50, 100, or 200 m away from their point of capture. Thirty lobsters were recaptured, 29 of which in the same area of the reef patch where they had been initially captured, regardless of the time elapsed (1-146 days). The proportion of recaptured lobsters was independent of the direction and distance of release when lobsters were displaced 50 and 100 m into the reef lagoon or along the axis of the reef, but no lobsters were recaptured from a distance of 200 m along the axis of the reef. Hence, the familiar home range of P. guttatus appears to lie within a radius of 100 m along the reef tract, and within this home range individuals possibly use several crevices as refuges. A tethering experiment showed that lobsters significantly moved towards the reef when released on bare sand 500 m away from the reef. Wave surge may have oriented the lobsters towards the reef. These results indicate that, despite their sedentary, non-migratory nature, adult male and female P. guttatus show homing and orientation abilities.

Strong “alarm odors” emanating from lethally injured conspecifics may indicate an imminent risk of predation to spiny lobsters. In laboratory trials,1 strong conspecific alarm odors elicited avoidance in Panulirus argus, a highly gregarious species that displays collective defense behavior, but not in Panulirus guttatus, a species that tends to aggregate when reproductive activity is high (spring) but not when it is low (late summer) and does not display collective defensive behavior. To reduce predation risk, however, lobsters may autotomize limbs, thus sustaining nonlethal injuries. I tested the response of these lobsters to scents emanating from intact, lethally-injured and non-lethally injured conspecifics. In P. argus, these scents elicited, respectively, attraction, avoidance and a random response, suggesting that, in P. argus, avoidance of conspecific alarm odors depends on their strength. In contrast, P. guttatus lobsters responded at random to scents of lethally injured conspecifics and showed a similar response to scents of intact and non-lethally injured conspecifics in the spring (attraction) and in the summer (random), reflecting the more cryptic defensive behavior of this species. Therefore, both species use conspecific alarm odors for risk-assessment, but each responds to these cues in the most effective way to reduce its risk of predation.

The reproductive biology of Panulirus guttatus from northern Quintana Roo, Mexico, was studied as part of a large research program on the biology and ecology of this poorly studied species. Lobsters were caught with baited traps deployed on the coral reef throughout 17 months (May 1988-September 1989). A total of 870 lobsters (558 males and 312 females) were obtained. The strongly biased sex ratio may have been an artifact of the sampling method, but differential movements of males and females related to reproductive activity were not excluded as possible causes. Ovigerous females (40% of total females, i.e., 125) occurred throughout the year, but were more prevalent during the spring of 1988, and the spring and summer of 1989. The size range of ovigerous females was 40.0-73.5 mm in carapace length (CL). Brood size was determined for the 125 ovigerous females plus an additional 41 sampled during 1987. After excluding the data of females with eggs about to hatch (of smaller sizes than eggs in previous stages), seasonal log brood size-log CL relationships were examined. No significant differences were found either seasonally or interannually, indicating that the average brood size of females of equal CL remained fairly similar throughout the study period. Females between 55 and 65 mm CL had the highest indices of reproductive potential, and accounted for 54% of the total egg production of the population. These results were compared with others obtained from populations of P. guttatus in Florida and other parts of the Caribbean.

Caribbean spiny lobsters, Panulirus argus, reside solitarily during the first months postsettlement, but shift to gregarious shelter use in later juvenile stages, at sizes as small as 15 mm in carapace length. To determine whether receptivity to or production of a chemical attractant among spiny lobster conspecifics is dependent upon body size or spatial scale, we conducted a series of overnight Y-maze shelter choice experiments. We placed a test lobster in an experimental arena and allowed it to choose between two shelters, which differed only in that water flowing by one shelter contained sea water that had passed through a header tank containing a conspecific. We varied the size of the lobster in the arena, the size and number of lobsters in the header tank, and the size of the experimental arena. Lobsters of all sizes tested released odours that attracted conspecifics; however, a single small lobster could attract other conspecifics only in the small arena. Lobsters greater than 15 mm in carapace length were attracted to shelters from which conspecific odours were emanating, while smaller lobsters were not. The results of this study suggest that: (1) the earliest benthic stages (less than 15 mm in carapace length) are unresponsive to conspecific odours, but lobsters greater than 15 mm in carapace length are attracted by conspecific odours; and (2) large lobsters produce a sufficient quantity of scent to attract conspecifics over distances of at least a few metres, whereas small lobsters (15-30 mm in carapace length) cannot. Body size- and spatial scale-dependent attraction could contribute to the shift from solitary to gregarious shelter use among Caribbean spiny lobsters. Copyright 1998 The Association for the Study of Animal Behaviour.

The population density of post-recruit spiny lobsters Panulirus argus in the reef-system of Bermuda during May through October was studied using a combined transect and capture-recapture approach in the northeastern reef-system. Population density was greatest near the reef-crest (6.0 ± 2.0 post-recruits ha −1 ; 95% confidence limits) and second greatest on the reef-front terrace (4.1 ± 1.4 post-recruits ha −1 ). The density of undersized P. argus lobsters on the outermost slopes and terraces of the Platform edge to the south of the island in September was estimated at approximately 97 lobsters ha −1 , indicating that aggregation of young post-recruit lobsters in deep water to the south of the island occurs at the close of the breeding season. The standing stock of P. argus post-recruits on the Bermuda island shelf was estimated at 1.3 × 10 5 lobsters from the combined transect and capture-recapture technique, and the mean density at 2.9 post-recruits ha −1 . An estimate of the annual fishing mortality coefficient ( F ) in the 1986/1987 season (0.42) was derived from the total biomass estimate. The technique has potential for assessment of standing stock biomass in the spiny lobster fisheries of island nations. The ratio of the catchability coefficient ( q ) to the effective area fished ( E ) was approximately the same (0.059 and 0.058), with baited Antillean arrowhead traps, for trappable P. argus and Panulirus guttatus lobsters of different size composition in the northeastern reefs at Bermuda. An average estimate of the parameter q/E for P. guttatus was used to derive a first approximation of the population density of sublegal P. argus (from the catchability coefficient, q ) on the outer shelf edge associated with the South Shore. The mean sampling-area and sampling-radius of baited Antillean arrowhead traps at Bermuda were estimated to be approximately 0.36 ha and 34 m.

The maximum sustainable yield (MSY) of legal-size spiny lobsters Panulirus argus (Latreille) was estimated at 37 (±SE 7.7) × 10 3 animals by regression of catch per unit effort (CPUE) on total effort. A graphical plot of P. argus fishery catch and effort data for lobster seasons from 1975/76 to 1986/87 resulted in a second estimate of the P. argus MSY of 30 × 10 3 lobsters per season by a quadratic regression of catch on total effort. A graphical plot of catch on total fishing effort data for the Guinea chick Lobster Panulirus guttatus (Latreille), with a quadratic curve fit ( R 2 = 0.612), resulted in an estimate of MSY of approximately 33 × 10 3 lobsters per calendar year. The 1985 and 1986 fishery catches of Guinea chick lobsters were close to the MSY. There was an overall increase in the CPUE of P. argus lobsters (1975/76–1986/87), whereas there was an overall decline in the CPUE of P. guttatus spiny lobsters over the same time period. The two species interannual patterns of change of CPUE followed that of sea temperature change on the Bermuda Platform; superimposed was a 5-year cycle of CPUE, which was particularly noticeable with P. guttatus lobsters, suggesting a causal relationship with a 5-year cycle in the annual mean temperature of sea surface waters, averaged from six temperature stations on the Platform. Annual yield of P. argus lobsters was correlated with Platform average sea temperature at the 10% level (Spearman rank test). Both P. guttatus and P. argus yields on Platform sea temperature were parabolic in form. Platform CPUE of Guinea chicks on Hamilton Harbour temperature also suggested a parabolic relationship in the range 22–26 °C (coefficient of determination R 2 = 0.43). There was clearly a parabolic association between P. argus CPUE and Hamilton Harbour temperature over the same temperature range ( R 2 = 0.93). It is suggested that the Lellis and Russell quadratic model for survival and growth of P. argus postlarvae may be extended to juvenile P. argus to explain these findings.

Microsatellite sequences were isolated from enriched genomic libraries of the spotted spiny lobster,Panulirus guttatususing 454 pyrosequencing. Twenty-nine previously developed polymerase chain reaction primer pairs ofPanulirus argusmicrosatellite loci were also tested for cross-species amplification inPanulirus guttatus.In total, eight consistently amplifying, and polymorphic loci were characterized for 57 individuals collected in the Florida Keys and Bermuda. The number of alleles per locus ranged from 8 to 20 and observed heterozygosities ranged from 0.409 to 0.958. Significant deviations from Hardy–Weinberg equilibrium were found in one locus from Florida and three loci from Bermuda. Quality control testing indicated that all loci were easy to score, highly polymorphic and showed no evidence of linkage disequilibrium. Null alleles were detected in three loci with moderate frequencies ranging from (20% to 22%). These eight microsatellites provide novel molecular markers for future conservation genetics research ofP. guttatus.

The Venezuelan lobster-management plan is based on information collected from the Panulirus argus fishery in Los Roques Archipelago National Park. Panulirus guttatus are harvested illegally, as this species does not reach the minimum landing size (120 mm carapace length; CL). Fishers consider enforcement of a 120 mm minimum CL unjust and request a new regulation. The purpose of this study was to determine the basic population characteristics of P. guttatus at the Morrocoy National Park, to provide information for managers, and to establish a population monitoring program. Interviews with fishers were conducted from September to December 1999, and their catch was counted, measured, and sexed. Of the 163 lobsters surveyed, 93.3% wereP. guttatus, 6.1% P. argus, and 0.6% P. laevicauda. The size range for P. guttatus was 42.1 to 75.6 mm CL (average: 60.9 6.9 mm CL). Sex ratio favoured males (1.45:1), and 48.4% of the 62 females examined bore eggs. The smallest reproductive female measured 42.1 mm CL; the largest measured 67.7 mm CL. Fishing is carried out in shallow waters of the outer reefs; lobsters are harvested by hand during nocturnal skin diving.

Panulirus argus and P. guttatus are sympatric and commonly share dens. We studied their den-related behaviour in 3 m-diameter tanks, each holding a casita (low den) and a cave (high den) (1) separately (2) together (3) together with a triggerfish predator (Balistes vetula), and (4) separately with the predator. Most P. argus left shelter at night, and some during the day, and showed no den preference in any treatment. In caves, individual P. argus occupied all parts of caves in treatments 1 and 2 and mostly the vault (walls and ceiling) in treatments 3 and 4. Not all P. guttatus left shelters at night, and none during the day. Individual P. guttatus showed no den preference in treatments 1 and 2, preferred the cave in 3 and 4, and always preferred the cave vault. Presence of congeners did not affect den choice or cave position for either species, whereas the predator affected den choice (P. guttatus only) and position in caves (both species). Videotapes showed aggression between individual P. guttatus but not between individual P. argus or between species. The fish cohabited with lobsters in the casita but attacked them in caves and in the open. Unlike P. argus, P. guttatus exhibited no communal defence.

Population dynamics of the spotted spiny lobster, Panulirus guttatus, were examined at Looe Key Reef, Florida, USA, from April 1987 to August 1989. The 347 lobsters captured (including recaptures), ranged from 9 mm (puerulus) to 75 mm carapace length (X = 54 mm CL). Pueruli settled all year round into small holes along the underside of the reef. All lobsters recaptured were found at the site of their initial capture; one was captured four times, all on the same reef spur, over 762 days. Adults sheltered within the reef during the day and foraged on top of the reef at night. Males and females were captured in equal proportions (1.2 M:1 F) from den entrances during the day; females were numerically dominant on foraging grounds at night (3 F:1 M). Reproduction occurred all year round but peaked between March and June; minimum size at maturity was 38 mm CL for females and 48 mm CL for males. The sheltering behaviour of P. guttatus, typically found on the ceiling of dens, contrasted markedly with that of the sympatric P. argus, typically found on the floor; both species used many of the same dens, but simultaneous co-occupancy was rare.

The puerulus of Panulirus guttatus is described and compared with that of P. argus, a sympatric species. Comparative morphological data show that the former has a more specialized form than the latter and hence is more recent in evolutionary terms. Features characterizing the puerulus of P. guttatus are its relatively large size, long spatulate antennae, and well developed sternal spines. The possible adaptive value of the long spatulate antennae for selection of specific substrata and/or navigation through inshore waters is discussed in relation to the ecology of the juvenile and adult phases. Pueruli of P. guttatus are not found in the surface collectors, resembling marine vegetation, used to monitor the influx of pueruli of P. argus into coastal waters on the Caribbean coast of Mexico. Moreover, small juveniles of P. guttatus are never found in the natural habitat of those of P. argus, and large juveniles and adults of P. guttatus seem restricted to the shallow coral reef habitat, in contrast to similar phases of P. argus, which occupy a vast array of habitats and depths throughout their benthic life. It is hypothesized that the pueruli of both species settle in different habitats, which would partly explain their sharing of the same geographic distribution.

The puerulus of Panulirus guttatus is described from specimens collected at Florida reefs. Preliminary examination by scanning electron microscopy of the spatulate antennal tip of a P. guttatus puerulus revealed no qualitative features different than those previously described for the tapered antennal tip of P. cygnus. The unique combination of morphological characters of the P. guttatus puerulus requires minor adjustment to a recently proposed evolutionary classification of Panulirus based on pueruli.

Results of graphical analyses of annual records of catch, effort and sea temperature indicate empirical quadratic associations between industry catch per unit of fishing effort (CPUE) in Bermudan spiny lobster (Panulirus argus and P. guttatus) fisheries and the annual average sea temperature at Hamilton Harbour, Bermuda. CPUE and yield of P. argus and of P. guttatus were each associated by quadratic expressions with the annual average sea temperature of the Bermuda Platform. Annual growth and survival of late juvenile P. argus and P. guttatus into the fishable stock at Bermuda is controlled in a quadratic fashion chiefly by sea temperature with a six-month lag. The optimum annual average sea temperature for the survival and growth of late benthic juvenile P. argus into the fishery stock was 23.6 � 0.2�C (mean � s.e.), and the comparable optimum for P. guttatus juvenile recruitment was 24.1 � 0.1�C. The maximum equilibrium catch of P. guttatus lobsters on Bermuda Platform was estimated at approximately 33 000 lobsters from quadratic regression of yield on fishing effort.