Panulirus Guttatus Research Articles

Detection and diagnosis of Panulirus argus virus 1 in captive spiny lobsters using qPCR in conjunction with histopathology and transmission electron microscopy.

Panulirus argus virus 1 (PaV1) is the first and only naturally occurring pathogenic virus described in the Caribbean spiny lobster, Panulirus argus. PaV1 infection in decapod species that commonly co-occur with P. argus, including the spotted spiny lobster Panulirus guttatus, has not been previously described. In 2016, 14 Caribbean and 5 spotted spiny lobsters were collected near Summerland Key, Florida, to supplement the resident population of the Audubon Aquarium of the Americas in New Orleans, Louisiana. After 5 months in quarantine, Caribbean and spotted spiny lobsters began to exhibit clinical signs of lethargy and dying in the molt. Initial histologic evaluation revealed intranuclear inclusion bodies in circulating hemocytes in the spongy connective tissue of the epidermis, suggesting a viral infection. Samples of hepatopancreas and hemolymph from deceased Caribbean and spotted spiny lobsters tested negative for white spot syndrome virus and positive for PaV1 using real-time quantitative polymerase chain reaction (qPCR). Intranuclear, eosinophilic to amphophilic, Cowdry type A inclusion bodies observed primarily within fixed phagocytes and circulating hemocytes in the hepatopancreas of freshly euthanized Caribbean spiny lobsters were consistent with PaV1 infection. Transmission electron microscopy revealed that hemocytes associated with hepatopancreatic tubules contained viral inclusions with location, size, and morphology consistent with previously described PaV1 infection. These findings highlight the significance of using molecular diagnostics in conjunction with histopathology and electron microscopy in the investigation and diagnosis of PaV1 in spiny lobsters. Further study is required to investigate the relationship of PaV1-associated mortality events and microscopic lesions in the spotted spiny lobster.

Diversity and Distribution of Mid- to Late-Stage Phyllosomata of Spiny and Slipper Lobsters (Decapoda: Achelata) in the Mexican Caribbean

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 >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.

Metamorphosis of spiny lobsters (Panulirus argus and Panulirus guttatus) in the Yucatan Current as inferred from the distribution of pueruli and final stage phyllosomata

AbstractFor spiny lobsters (Palinuridae), the co‐occurrence of final‐stage larvae (phyllosomata) and postlarvae (pueruli) in sampling stations over oceanic waters is indicative of metamorphosis zones, some of which have been found in boundary currents. We hypothesized that metamorphosis of Panulirus argus and P. guttatus off the Mexican Caribbean coast, which has a very narrow shelf, occurs in the swift Yucatan Current (YC). During two cruises conducted in autumn 2012 and spring 2013, a mid‐water trawl and a neuston net were simultaneously towed in night samplings along transects up to ~ 100 km across the YC. Hydrographic and current fields were derived from Conductivity, Temperature and Depth, and altimetry data. Metamorphosis occurred mainly within the YC core. However, velocity and distance to the coast of the YC varied with cruise, and features that may favor retention (a persistent coastal eddy and a countercurrent) were detected. Despite differences in size and condition of pueruli between cruises, their energy stores did not appear to decline during the shoreward migration, suggesting that metamorphosing within strong boundary currents may increase the chances of pueruli arriving more quickly to a shore. Based on previously reported current features and swimming speeds, pueruli metamorphosing up to 12 km offshore are more likely to reach the Mexican Caribbean coast without much loss of energetic reserves. This could also occur for some pueruli metamorphosing up to 30 km offshore if encountering the features favoring retention. In contrast, pueruli metamorphosing > 30 km offshore are more likely to be carried into the Gulf of Mexico and elsewhere.

Development in culture of larval spotted spiny lobster Panulirus guttatus (Latreille, 1804) (Decapoda: Achelata: Palinuridae)

AbstractThere 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.

A histological atlas for the Palinuridae (Crustacea: Decapoda: Achelata): A guide to parasite discovery and spotting the abnormal in spiny lobsters.

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.

Coral Reef Degradation Differentially Alters Feeding Ecology of Co-occurring Congeneric Spiny Lobsters

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.

Dietary partitioning between sympatric species of spiny lobster in a coral reef system

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.

Distribution and abundance of <I>Panulirus</I> spp. phyllosomas off the Mexican Caribbean coast

We evaluated the abundance and distribution of Panulirus spp. phyllosomas collected during two oceanographic cruises in March 2006 and January 2007 along the Mexican Caribbean coast. In total, 1138 phyllosomas were collected in 2006, and 492 were collected in 2007, comprising three families: Palinuridae; Scyllaridae; and Sinaxidae. The most abundant species of Panulirus for both cruises was Panulirus argus (Latreille, 1804). DNA barcoding methods also confirmed the identity of the phyllosomal stages of Panulirus guttatus (Latreille, 1804). The most abundant phyllosomal stages of P. argus in both years were early (I–III) and mid stages (IV–VIII) mostly found near Banco Chinchorro. The least abundant late stages (IX–X) were widely dispersed offshore. During both cruises, >70% of phyllosomal abundance was concentrated in the surface layers (0–50 m). Statistical models indicated that depth, along with year, geographical area, and time of day, were important for early- and mid-stage phyllosoma stages. The distribution and densities of phyllosomas off Quintana Roo differed among years and areas, likely due to varying environmental conditions and mediated by physical processes and the seasonality of reproductive activity of the local and regional spawning stock. In addition, early-stage phyllosomas appeared to avoid surface waters during periods of increased moonlight.

Isolation and characterization of eight polymorphic microsatellites for the spotted spiny lobster, Panulirus guttatus.

Microsatellite sequences were isolated from enriched genomic libraries of the spotted spiny lobster, Panulirus guttatus using 454 pyrosequencing. Twenty-nine previously developed polymerase chain reaction primer pairs of Panulirus argus microsatellite loci were also tested for cross-species amplification in Panulirus 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 of P. guttatus.

An exception to the rule: top-down control of a coral reef macroinvertebrate community by a tropical spiny lobster

In temperate habitats, predation by lobsters creates trophic cascades that reverberate through benthic communities. However, the influence of lobsters on tropical benthic communities is thought to be minimal due to higher prey diversity and the mobility and broad diet of lobsters. We hypothesized that this would not be the case for the spotted spiny lobster (Panulirus guttatus Latreille, 1804), an obligate, philopatric dweller of Caribbean coral reefs. Our study took place in the Florida Keys (USA), where we examined the gut contents of wild lobsters, conducted laboratory experiments on lobster prey selection and foraging effectiveness in rubble, and manipulated lobster density on isolated patch reefs to examine the effects of lobster predation on macroinvertebrate prey over a 3-yr period. We found P. guttatus to be a generalist carnivore that consumed a suite of macroinvertebrates, including important reef herbivores (e.g., herbivorous crabs, gastropods, and urchins) that comprised >60% of its diet. Higher densities of P. guttatus exerted strong top-down control over the abundance and composition of macroinvertebrate prey in rubble substrates on patch reefs, but not prey living in substrates dominated by macroalgae. Lobster foraging success in rubble also depended on rubble size; lobsters extracted prey from and overturned rubble more easily when rubble was smaller. The abundance and high site fidelity of predatory P. guttatus appears to provide the necessary conditions for top-down control of prey in coral reef rubble zones, an effect similar to the powerful influence of lobster predation observed in temperate ecosystems.

Aggressive behaviour of spotted spiny lobsters (Panulirus guttatus) in different social contexts: the influence of sex, size, and missing limbs

AbstractPanulirus 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.

Differences in life-history and ecological traits between co-occurring Panulirus spiny lobsters (Decapoda, Palinuridae).

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 Influence of Shelter, Conspecifics, and Threat of Predation on the Behavior of the Long-Spined Sea Urchin (Diadema antillarum)

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 shelte...

Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 495:185-191 (2014) - DOI: https://doi.org/10.3354/meps10568 Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus Meredith D. Kintzing1,2, Mark J. Butler IV1,* 1Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529, USA 2Present address: University of North Carolina at Chapel Hill, Department of Marine Sciences, Chapel Hill, North Carolina 27599, USA *Corresponding author: mbutler@odu.edu ABSTRACT: 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 overfished 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. KEY WORDS: Diadema antillarum · Panulirus guttatus · Florida Keys · Predation · Trait-mediated interactions · Coral reefs Full text in pdf format PreviousNextCite this article as: Kintzing MD, Butler IV MJ (2014) Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus. Mar Ecol Prog Ser 495:185-191. https://doi.org/10.3354/meps10568 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 495. Online publication date: January 09, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Mate choice and sperm limitation in the spotted spiny lobster, Panulirus guttatus

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 were unavailable, females mated with smaller males, which resulted in reduced fertilization success. Thus, for species like P. guttatus that dwell in patchy habitats with limited mate availability, the optimal strategy for mate choice is context-dependent, although not without cost to the largest females.

Increased reproductive opportunity: a potential benefit of seasonal aggregation for a little-gregarious and highly sedentary spiny lobster

The spiny lobster Panulirus guttatus is a highly sedentary, obligate reef-dweller that exhibits a low degree of gregariousness yet reproduces year-round. Previous laboratory studies revealed that these lobsters were significantly attracted to scents released by conspecifics during a ‘high reproductive activity’ period (HRA,~60% of ovigerous females on average) but not during a ‘low reproductive activity’ period (LRA,~20%), suggesting that becoming more closely distributed at the right time may increase reproductive opportunities for these lobsters. We tested this hypothesis in the field. We marked all crevices harbouring P. guttatus lobsters (‘dens’) on two isolated coral reef patches over six consecutive sampling periods (three during an LRA and three during the ensuing HRA) and recorded the number, sex and size of lobsters in each den. Dens marked at a given time were considered as harbouring zero lobsters at previous times. For each site, a model selection based on parameters of the negative binomial distribution showed that m (mean lobsters/den) varied little over time but that k (dispersion parameter) decreased across the LRA and remained low (indicating a more clumped distribution) across the HRA. These trends in aggregation were further confirmed by values of Lloyd's ‘patchiness’, supporting the hypothesis that seasonal aggregation increases reproductive opportunities for P. guttatus. However, the tendency to aggregate appeared to be modulated by density and mean size of lobsters, which differed with site. These findings have potential implications for exploited P. guttatus populations and invite further study of the complex behaviours that characterize sedentary lobsters.

Does size always matter? Mate choice and sperm allocation in Panulirus guttatus, a highly sedentary, habitat-specialist spiny lobster

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.

Variable reproductive success in fragmented populations

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.

Assessment of predation risk through conspecific alarm odors by spiny lobsters

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 automize limbs, thus sustaining non-lethal 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.

Influence of Conspecific and Heterospecific Aggregation Cues and Alarm Odors on Shelter Choice by Syntopic Spiny Lobsters

In spiny lobsters, conspecific scents ("aggregation cues") may mediate gregarious diurnal sheltering, but scents from injured conspecifics ("alarm odors") may elicit avoidance behavior. In laboratory experiments, individuals of two coexisting species, Panulirus guttatus (a reef-obligate) and P. argus (a temporary reef-dweller), significantly chose shelters emanating conspecific aggregation cues and responded randomly to shelters emanating heterospecific aggregation cues. However, despite evidence that the two species perceived each other's alarm odors to a similar extent, P. guttatus responded randomly to shelters emanating either conspecific or heterospecific alarm odors, whereas P. argus significantly avoided both. This differential influence of alarm odors likely reflects interspecific differences in life history, sociality, and behavior. The less social, reef-obligate P. guttatus lobsters forage close to their reef dens, into which they retract deeply upon perception of risk. This cryptic behavior may offset the need to avoid conspecific (and heterospecific) alarm odors. In contrast, avoidance of conspecific alarm odors by P. argus is consistent with its ontogenetic habitat shifts and greater sociality. Furthermore, because reef-dwelling P. argus lobsters forage across open areas away from the reef, an ability to avoid alarm odors from P. guttatus upon returning to their reef dens may increase their fitness.