Commensal Crab Research Articles

Molecular phylogeography of Tumidotheres maculatus (Say, 1818) and Zaops ostreus (Say, 1817) (Crustacea: Decapoda: Pinnotheridae) in the western Atlantic, with description of a new species and synonymy of Epulotheres Manning, 1993

ABSTRACTThe commensal crab genus Tumidotheres is reportedly represented along the western Atlantic coast by Tumidotheres maculatus, with populations distributed from temperate to tropical waters in North and South America. Western Atlantic populations of the related genus Zaops have been alternatively separated into the northern species Zaops ostreus and southern Zaops geddesi. We hypothesized that populations of T. maculatus comprised more than one species, much as currently accepted in Zaops. Molecular markers (COI, 16S-NADH1 complex, 12S, and histone 3) were used to infer relationships between sampled populations of Tumidotheres and Zaops. We found that most populations of Tumidotheres belonged to a single species, but that specimens from the western Caribbean Sea represented an undescribed congener, herewith described and named. Remarkably, all sequenced populations of Zaops were inseparable, leading us to question the validity of Z. geddesi as the southern counterpart of Z. ostreus. Though sequence analyses failed, we provisionally reassign Epulotheres angelae to the genus Zaops on the basis of morphological characters. Since Epulotheres is a monotypic genus, this synonymizes the genus with Zaops.

Diversity and abundance of conspicuous macrocrustaceans on coral reefs differing in level of degradation.

Coral reefs sustain abundant and diverse macrocrustaceans that perform multiple ecological roles, but coral reefs are undergoing massive degradation that may be driving changes in the species composition and abundance of reef-associated macrocrustaceans. To provide insight into this issue, we used non-destructive visual census techniques to compare the diversity and abundance of conspicuous macrocrustaceans (i.e., those >1 cm and visible without disturbance) between two shallow Caribbean coral reefs similar in size (∼1.5 km in length) and close to each other, but one (“Limones”) characterized by extensive stands of the branching coral Acropora palmata, and the other (“Bonanza”) dominated by macroalgae and relic coral skeletons and rubble (i.e., degraded). We also assessed the structural complexity of each reef and the percent cover of various benthic community components. Given the type of growth of A. palmata, we expected to find a greater structural complexity, a higher cover of live coral, and a lower cover of macroalgae on Limones, and hence a more diverse and abundant macrocrustacean community on this reef compared with Bonanza. Overall, we identified 63 macrocrustacean species (61 Decapoda and two Stomatopoda). Contrary to our expectations, structural complexity did not differ significantly between the back-reef zones of these reefs but varied more broadly on Limones, and the diversity and abundance of macrocrustaceans were higher on Bonanza than on Limones despite live coral cover being higher on Limones and macroalgal cover higher on Bonanza. However, the use of various types of microhabitats by macrocrustaceans differed substantially between reefs. On both reefs, the dominant species were the clinging crab Mithraculus coryphe and the hermit crab Calcinus tibicen, but the former was more abundant on Bonanza and the latter on Limones. M. coryphe occupied a diverse array of microhabitats but mostly coral rubble and relic skeletons, whereas C. tibicen was often, but not always, found associated with colonies of Millepora spp. A small commensal crab of A. palmata, Domecia acanthophora, was far more abundant on Limones, emerging as the main discriminant species between reefs. Our results suggest that local diversity and abundance of reef-associated macrocrustaceans are partially modulated by habitat degradation, the diversity of microhabitat types, and the establishment of different commensal associations rather than by structural complexity alone.

Host selection, host-use pattern and competition in Dissodactylus crinitichelis and Clypeasterophilus stebbingi (Brachyura: Pinnotheridae)

The genera Dissodactylus and Clypeasterophilus are commensal or parasitic crabs that live in association with irregular sea urchins. Only a single pinnotherid species is expected to occur on a sand dollar; however, during field observations, D. crinitichelis and Clypeasterophilus stebbingi were found co-occurring on a single host (Clypeaster subdepressus). Laboratory experiments and in situ observations were conducted to explore mechanisms of host selection and use by C. stebbingi, as well as the possibility of competition with D. crinitichelis. Analysis of 213 specimens of Encope emarginata and 33 C. subdepressus revealed a high frequency of infestation (90 %) by brachyurans. The number of D. crinitichelis was positively correlated with the size of E. emarginata. During field observations and experiments, D. crinitichelis was able to colonize both echinoids, while C. stebbingi was found mainly on C. subdepressus. No exclusion was reported between individuals of the same sex for both crab species. However, D. crinitichelis may be territorial, since a single male occurred when adult females were added to the host. D. crinitichelis and C. stebbingi co-occurred on the same individual of C. subdepressus on rare occasions during field observations. C. stebbingi may exclude D. crinitichelis from the echinoid to avoid competition, as observed during the experiments. We suggest a species-specific association between C. stebbingi and C. subdepressus, while D. crinitichelis associated mainly with E. emarginata, but also with C. subdepressus. Both crabs may harm the echinoids by consuming their spines, but additional research is necessary to determine whether this is a parasitic association.

Trace and major elements distribution and transfer within a benthic system: Polychaete Chaetopterus variopedatus, commensal crab Polyonyx gibbesi, worm tube, and sediments

Samples of the polychaete Chaetopterus variopedatus, worm tubes, commensal crab Polyonyx gibbesi and sediments were collected in eight sites in Todos os Santos Bay, Brazil, in order to evaluate the potential use of the polychaetes and crabs as biomonitors and to assess the relationships and accumulation of trace and major elements in different benthic compartments. Trace and major elements were determined by ICP OES. Organic carbon, total nitrogen and sulfur were determined by CNS elemental analyser. Tubes, crabs and polychaetes were important in the retention of trace and major elements. Metals that presented the highest accumulation in polychaetes (i.e. Mg>Al>Fe>Zn>Mn>Co>Cu>Ba>Cr) where the same for crabs (i.e. Mg>Al>Fe>Mn>Co>Zn>Cu>Ba>Cr). High concentrations of Al, Ba, Cr, Mn and Fe, from terrigenous sources, were observed in tubes, which presented accumulation factors up to 81.5 for Mn. Sedentary polychaetes are seen as good biomonitor alternatives for metal contamination studies, because they are one of the most abundant taxon in the benthic system, live in direct contact with sediments, are present in broad distributions and can also handle relatively high concentrations of metals ensuring chronic exposition. The possibility to work with not only the polychaete but also its tube offers advantages compared to bivalves that generally do not accumulate certain metals in very high levels.

New record and biological features of the commensal porcellanid crab Polyonyx gibbesi (Crustacea: Anomura) from the north-eastern Brazilian coast

New record and biological features of the commensal porcellanid crab Polyonyx gibbesi (Crustacea: Anomura) from the north-eastern Brazilian coast

Food webs and fishing affect parasitism of the sea urchinEucidaris galapagensisin the Galápagos

In the Galápagos Islands, two eulimid snails parasitize the common pencil sea urchin, Eucidaris galapagensis. Past work in the Galápagos suggests that fishing reduces lobster and fish densities and, due to this relaxation of predation pressure, indirectly increases urchin densities, creating the potential for complex indirect interactions between fishing and parasitic snails. To measure indirect effects of fishing on these parasitic snails, we investigated the spatial relationships among urchins, parasitic snails, commensal crabs, and large urchin predators (hogfish and lobsters). Parasitic snails had higher densities at sites where urchins were abundant, probably due to increased resource availability. Commensal crabs that shelter under urchin spines, particularly the endemic Mithrax nodosus, preyed on the parasitic snails in aquaria, and snails were less abundant at field sites where these crabs were common. In aquaria, hogfish and lobsters readily ate crabs, but crabs were protected from predation under urchin spines, leading to a facultative mutualism between commensal crabs and urchins. In the field, fishing appeared to indirectly increase the abundance of urchins and their commensal crabs by reducing predation pressure from fish and lobsters. Fished sites had fewer snails per urchin, probably due to increased predation from commensal crabs. However, because fished sites also tended to have more urchins, there was no significant net effect of fishing on the number of snails per square meter. These results suggest that fishing can have complex indirect effects on parasites by altering food webs.

Ectosymbiotic behavior of Cancer gracilis and its trophic relationships with its host Phacellophora camtschatica and the parasitoid Hyperia medusarum

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 315:221-236 (2006) - doi:10.3354/meps315221 Ectosymbiotic behavior of Cancer gracilis and its trophic relationships with its host Phacellophora camtschatica and the parasitoid Hyperia medusarum Trisha Towanda*, Erik V. Thuesen Laboratory I, Evergreen State College, Olympia, Washington 98505, USA *Email: trisha@towanda.com ABSTRACT: In southern Puget Sound, large numbers of megalopae and juveniles of the brachyuran crab Cancer gracilis and the hyperiid amphipod Hyperia medusarum were found riding the scyphozoan Phacellophora camtschatica. C. gracilis megalopae numbered up to 326 individuals per medusa, instars reached 13 individuals per host and H. medusarum numbered up to 446 amphipods per host. Although C. gracilis megalopae and instars are not seen riding Aurelia labiata in the field, instars readily clung to A. labiata, as well as an artificial medusa, when confined in a planktonkreisel. In the laboratory, C. gracilis was observed to consume H. medusarum, P. camtschatica, Artemia franciscana and A. labiata. Crab fecal pellets contained mixed crustacean exoskeletons (70%), nematocysts (20%), and diatom frustules (8%). Nematocysts predominated in the fecal pellets of all stages and sexes of H. medusarum. In stable isotope studies, the δ13C and δ15N values for the megalopae (–19.9 and 11.4, respectively) fell closely in the range of those for H. medusarum (–19.6 and 12.5, respectively) and indicate a similar trophic reliance on the host. The broad range of δ13C (–25.2 to –19.6) and δ15N (10.9 to 17.5) values among crab instars reflects an increased diversity of diet as crabs develop. The association between C. gracilis and P. camtschatica is unusual because of the ontogenic switch of the symbiont from a primarily kleptoparasitic association to a facultative cleaning association. It is suggested that P. camtschatica incidentially concentrates H. medusarum in its oral arms as the symbionts transfer from its gelatinous prey. Metabolic studies suggest that by riding medusae, crabs may be able to develop faster through transport into warmer surface waters while reducing the energetic costs associated with locomotion. KEY WORDS: Symbiosis · Scyphozoa · Commensal crab · Hyperiid amphipod · Cleaning behavior · Stable isotope · Metabolic rate · Fecal pellet Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 315. Online publication date: June 13, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Notes on Rare Pinnixa Crabs (Decapoda, Brachyura, Pinnotheridae) of Japan

A rare commensal crab, Pinnixa penultipedalis Stimpson, 1858, was collected from the Oki Islands, Shimane Prefecture, Japan. The present specimen is not only the third record of this rare species from Japanese waters but also represents an extension of its known range further northeast. We also examined the type specimen of another rare congener, Pinnixa haematosticta Sakai, 1934, and an updated key to the genus Pinnixa in Japan is given.

Latitudinal variation in the reproductive biology of the commensal crab Pinnaxodes chilensis (Decapoda: Pinnotheridae) along the Chilean coast

The pinnotherid crab Pinnaxodes chilensis is a common commensal of the edible sea urchin Loxechinus albus along the Chilean coast. Several aspects of the reproductive biology of P. chilensis were examined between April and June 1999, along temperature and salinity gradients, at three sampling sites along the Chilean coast (23°45′S–39°24′S). Results demonstrated significant differences in egg number, egg volume, dry egg weight, and reproductive output of ovigerous females, between the studied populations of northern and central-southern Chile. Egg volume, egg dry weight, and reproductive output of females decreased from high to low latitudes, while egg number increased from high to low latitudes, exhibiting a clear trade-off with egg volume. It has been shown that changes in environmental conditions (e.g. temperature, salinity) along a latitudinal gradient, can generate clines in reproductive characteristics in both free-living and parasitic species.

Host-use pattern and host-selection during ontogeny of the commensal crab Allopetrolisthes spinifrons (H. Milne Edwards, 1837) (Decapoda: Anomura: Porcellanidae)

Allopetrolisthes spinifrons has been reported as a commensal crab of sea anemones, sea stars, and gastropods. Previous studies had shown that small crabs (carapace length, CL<4.0 mm) inhabit various hosts, while adults only dwell on sea anemones. This last observation suggests that these commensal crabs may change their host-use pattern during ontogeny. We examined the host-use pattern of A. spinifrons in the field and the host selection behaviour in the laboratory to examine if different hosts are used during ontogeny. Allopetrolisthes spinifrons was found on 77% and 58% of collected sea anemones and sea stars, respectively. On gastropod hosts, frequency of occurrence of A. spinifrons was low (<20%). The occurrence of the association was affected by the size of the host, large hosts being more frequently inhabited by commensal crabs. In general, one or two crabs were observed per host. Usually no more than five crabs were found on a single host, with the exception of one large sea star that hosted a maximum of 12 crabs. The analysis of the host-use pattern demonstrated that all the life stages (including mature crabs) of A. spinifrons inhabit sea anemones while on the remaining hosts only megalopa larvae and small juveniles (crabs<4.3 mm CL) were found. In laboratory experiments, crabs of all sizes preferred sea anemones over limpets (Fissurella spp.). Most of the small commensal crabs (2.0<CL<4.0mm) migrated from limpets to sea anemones during a 10 experiment day. These results indicate that the non-anthozoan invertebrates studied herein are used as alternative hosts by A. spinifrons during larval settlement possibly as a result of the limited availability of sea anemones. When crabs attain a size between 2.0-4.0 mm CL they abandon these alternative hosts in order to find their preferred hosts, sea anemones. Thus, habitat restrictions during the settlement process may explain the existence of various alternative hosts utilized by recruits compared to the high host-specificity shown by adult crabs of A. spinifrons.

Life history of Allopetrolisthes spinifrons, a crab associate of the sea anemone Phymactis clematis

Allopetrolisthes spinifrons is an ectocommensal crab of the sea anemone Phymactis clematis. The population biology of A. spinifrons in north central Chile was examined between January and December 1996. During 1996, 74% of P. clematis in the rocky intertidal zone hosted at least one commensal crab. In most cases, one sea anemone was inhabited by a single adult crab, either male or female. A few sea anemones hosted two or more crabs, one usually being an adult and the others juveniles or small crabs that just had recruited to the host. The sex ratio of adult crabs was ∼1:1 during most months. Reproduction occurred with similar intensity throughout the year as indicated by the continuous presence of reproductive females. Similarly, recruitment of A. spinifrons occurred throughout the year with the exception of late winter when no megalopae and small juveniles were found on sea anemones. Fecundity of female crabs varied between 121 and 5661 eggs per female (6·9–19·2 mm carapace length) and was significantly higher during the austral winter (July) than during the summer (December). The fact that most sea anemones were inhabited by a single adult crab indicates that hosts may be monopolized by individual crabs. Resource requirements may prohibit adult crabs from sharing a host individual with another large crab, while adult tolerance towards juveniles may facilitate the maintenance of local populations.

Host use pattern and life history of Liopetrolisthes mitra, a crab associate of the black sea urchin Tetrapygus niger

The porcellanid crab Liopetrolisthes mitra is a common associate of the black sea urchin, Tetrapygus niger in north central Chile. The host-use pattern, population dynamics and reproductive pattern of L. mitra on sea urchins were examined between January 1996 and February 1997. Each month, between 60 and 95 per cent of all collected urchins hosted crabs, with the highest frequency of cohabitation occurring during the austral summer (January to March). Group sizes of crabs on individual urchins ranged from 1 to 25 crabs per host. The average density of crabs on the urchins ranged from 2 to 5.5 crabs per host. Large urchins were inhabited by crabs more frequently than small urchins but urchin size had no effect on the number or size of crabs. The sex ratio of adult crabs was ˜1:1 during most months. Reproduction occurred throughout the year but was most intense during the austral spring and summer (October to March), when the highest percentage of ovigerous females were found. Similarly, recruitment of L. mitra occurred throughout the year but reached a peak during austral summer and early autumn (January to May). All life stages of L. mitra including recently settled megalopae and reproductive adults were found on urchins. Size–frequency analysis indicated that many crabs live &gt;1.5 years. The results of this study confirm that the association between L. mitra and T. niger is strong and persists throughout the benthic life of the commensal crab.

A New Commensal Crab of the Family Pinnotheridae from Okinawa, the Ryukyu Islands

A New Commensal Crab of the Family Pinnotheridae from Okinawa, the Ryukyu Islands

Morphometric and electrophoretic evidences for two species of the genus Liopetrolisthes (crustacea: decapoda: porcellanidae) and some aspects of their variability

1. 1. Four colour forms of the porcellanid commensal crab Liopetrolisthes from Chilean coastal waters were compared by canonical discriminant analysis (DCA) over 10 morphological variables and by horizontal starch gel electrophoresis of 16 enzymes and total proteins with the aim of determining whether they correspond to the single species L. mitra or to different species. 2. 2. The morphometric analysis showed the existence of two morphological groups which were principally discriminated by the dactylus and propodus dimensions of the chelipods. 3. 3. Nine enzymatic systems were successfully tested: α-glycerophosphate dehydrogenase (α-GPDH), malic enzyme (ME), alkaline phosphatase (ALP), phosphoglucose isomerse (PGI), phosphoglucomutase (PGM), glutamate-oxalacetate transaminase (GOT), isocitrate dehydrogenase (IDH), lactae dehydrogenase (LDH), malate dehydrogenase (MDH) and total proteins (PT), which gave a total of 16 loci analyzed. 4. 4. The biochemical analysis demonstrated that there were no electrophoretic differences within the two morphological groups discriminated by the DCA. However there was great genetic divergence among them, expressed by eight diagnostic loci and by an unbiased estimate of Nei's [ Gentics, Austin, Texas 89, 583–590 (1978)] genetic distance of 0.979. 5. 5. The magnitude of this divergence and the lack of evidence of gene flow between the two morphological groups, allows us to conclude that Liopetrolisthes shows two valid species. 6. 6. A following study [Weber, Gayana Zool. (in press, 1991)] demonstrated that these two species are L. mitra [Dana, United States Exploring Expedition during the years 1838–1842, under the command of Charles Wilkes, U.S.N., Vol. 13, Crustacea, Part 1, p. 685 (1852)] and L. patagonicus [Cunningham, Trans. Linn. Soc. London 27, 465–502 (1871)]. 7. 7. Liopetrolisthes mitra showed a polymorphism of 0.200 and an unbiased observed heterozygosity of 0.089 which are nearly values given for anomurans. Liopetrolisthes patagonicus, which lives on the overexploited sea-urchin Loxechinus albus, showed much reduced variability with a polymorphism of 0.066 and an unbiased mean observed heterozygosity of 0.008, which may be related to the fishing pressure-bottleneck hypothesis.

Kommensalische Porzellaniden Aus Der Karibik (Decapoda, Anomura)

Five species of Porcellanidae from the Caribbean Sea have been found to establish commensal relationships with other animals. In four of the described cases, comparable relationships were found to exist also in the Eastern Pacific. Therefore the origins of the discussed commensalisms are assumed to date prior to the final formation of the Central American land-bridge. In all cases the host provides protection to the commensal crab. In the species Minyocerus angustus (Dana), Polyonyx gibbesi Haig, and Porcellana sayana (Leach) the host serves as an auxiliary substrate which enables the porcellanid crab to colonize soft bottom habitats, normally not suitable for porcellanids. This interpretation is supported by P. sayana whose different hosts are not characterized by systematic relationship but by having the same habitat and by the requirements of the commensal as to the external structure and the habits of the host. The present observations show, that species which are found to live as obligate commensals in a definite geographical region, may be free-living elsewhere under different ecological conditions. As regulating factors, competition and predation are considered.

Fabia Tellinae, a New Species of Commensal Crab (Decapoda, Pinnotheridae) From the Northeastern Gulf of Mexico

Fabia tellinae, espece nouvelle de la famille des Pinnotheridae, provenant de l'Atlantique occidental, est decrite. Cette espece est apparentee a F. subquadrata Dana et a F. byssomiae (Say) ; les caracteres distinctifs de ces trois especes sont enumeres.

Larval Stages of the Crab, Pinnotheres maculatus, under Laboratory Conditions

The larvae ofPinnotheres maculatus, say, a small commensal crab commonly found in the scallopAequipecten irradians, have been reared from hatching to the crab stage under laboratory conditions. The zoeae were reared at 30%. 25°C and fed recently hatchedArtemia, nauplii and fertilizedArbacia eggs. The five zoeal stages and one megalops stage are described and figured. The larvae ofP. maculatus can be distinguished from all others which have been described on the basis of general morphological features.

INFLUENCE OF HOSTS ON THE BEHAVIOR OF THE COMMENSAL CRAB PINNOTHERES MACULATUS SAY

1. Experiments using a circular choice apparatus showed a statistically significant attraction of commensal crabs, Pinnotheres maculatus, to bay scallops, Aequipecten irradians concentricus, and penshells, Atrina rigida.2. The adult males of P. maculatus removed from bay scallops showed a significant attraction to the host.3. When tested for preference between the two hosts, crabs removed from bay scallops showed no preference for one host over the other. The attraction of crabs to both the hosts was statistically significant. Experiments suggested that the crabs removed from scallops are not host-specific.

CHANGES IN ABUNDANCE OF THE COMMENSAL CRABS OF CHAETOPTERUS

1. The relative abundance of two species of commensal crabs of Chaetopterus, Pinnixa chaetopterana and Polyonyx macrocheles, has been determined in the regions of Clearwater, Florida; Beaufort, North Carolina; and Woods Hole, Massachusetts. The marked changes in relative abundance of the two crabs that have occurred during the last half century at Beaufort and Woods Hole are discussed.2. Comparative observations on the life-history and ecology of the two crabs are recorded.3. Pinnixa is considered a facultative commensal and Polyonyx an obligate commensal of Chaetopterus.

The Demonstration of a "Host-Factor" in Commensal Crabs

union. For his survey, Davenport turned to the almost infinite possibilities for such study which exist in the marine fauna. In this paper the author is reporting the results of investigations concerning the commensal relationships of four marine decapod Crustacea occurring in large populations in the Beaufort, N. C., area. The problem was to ascertain if these crabs, commensal with members of three other phyla, exhibited any evidence of a chemical basis for the establishment or maintenance of the commensal union.