Burrow morphology and dynamics of mudshrimp in Asian soft shores

Mudshrimps are important soft shore bioturbators but research on the ecology of tropical species has received less attention when compared with their temperate counterparts. The mudshrimp Austinogebia edulis is common on Asian soft shores and lives in burrows for its entire adult life. Epoxy resin casting of A. edulis burrows showed that they were approximately Y-shaped, with an upper U-part and the lower central shaft part. The burrows had two openings extending to the surface; the mean distance between the two openings was 11.0 cm in Hong Kong and 26.4 cm in Taiwan. Openings of the burrows had small chimneys. The tunnels of the burrows were circular, narrow and with a smooth surface (tunnel diameter corresponded to shrimp carapace width). Each burrow was inhabited by a single shrimp and burrows were inter-connected during the mating and reproductive season. Each burrow had four to 12 spherical chambers, which were free of detritus. The chambers were thought to be used for suspension feeding, current generation and as turning points. The depth of burrows was up to 1.1 m. Multivariate analysis on various burrow parameters showed that burrows collected on a mud flat in Taiwan were deeper, had a wider distance between the openings and a larger volume than burrows collected from a sandy shore in Hong Kong, suggesting that burrow architecture is variable between shore types. Burrow architecture, however, did not vary between tidal levels, seasons and shrimp density on the shores in Hong Kong, indicating that the burrows were quite stable within the substratum and were not affected by environmental and biological factors.     

Parental care and reproductive behavior of the clown goby, <Emphasis Type="Italic">Microgobius gulosus</Emphasis>, with observations on predator interactions

Describe reproductive behavior and mating system of the clown goby from field observations. Clown gobies exhibit a loosely haremic mating system. Pairs construct burrows at the base of cattails, the roots of which provide structural support and a spawning substrate. Larger males monopolize multiple burrows, each with an individual female. After spawning, males camouflage burrow entrances with sand and females brood developing young for 4 days. Males continue to guard the covered nests in 50% of observed brooding periods. Burrows are also used as shelter from predators. Both sexes confront intruders but only males exhibit a distinct color response to juvenile blue crabs, Callinectes sapidus, the most significant predator. The male color response appeared to mimic the color of adult blue crabs, a known predator of juvenile crabs, perhaps acting as a deterrent. The presence of the predatory blue crab may require one parent to perform deterrent displays, promoting female care in this mating system.     

Comparative Burrow Architectures of Resident Fiddler Crabs (Ocypodidae) in Indian Sundarban Mangroves to Assess Their Suitability as Bioturbating Agents

Excavation of burrows by fiddler crabs (genus Uca) is an important component in mangrove ecosystem functioning. This bioturbation activity can be measured by analysing the burrow architecture of these crabs. The aim of the present study is to describe and evaluate inter specific differences in the burrow morphologies of four species of fiddler crabs (Uca rosea, Uca triangularis, Uca dussumieri and Uca vocans) using polyester resin casts of the burrows. For each of the species, sex and carapace width (CW; mm) were determined for all the individuals. Three burrow morphological characters viz. burrow diameter (BD; mm), total burrow depth (TBD; mm) and burrow volume (BV; cm³) were considered during the study. Density of each species throughout the year was also assessed. For all the species BD and BV were higher in case of males compared to the females and they showed significant positive correlation with the CW of the burrow inhabitants. The amount of sediment excavated by each crab was evaluated in terms of BV. Among all the studied species, U. rosea was established as the most potent bioturbative candidate in the studied mangrove due to their greater density and moderate ability to excavate burrow.     

Burrow structure and use in the sand fiddler crab, Uca pugilator (Bosc)

Uca pugilator, the sand fiddler crab, constructs two kinds of burrows in protected, sandy upper-intertidal and supratidal substrates on the west coast of Florida. Temporary burrows are built and used as a refuge by non-breeding crabs during high tide periods and at night when crabs cease feeding in the intertidal zone. Breeding burrows are constructed and defended by courting males and are the site of mating, oviposition and the incubation of eggs by females. Up to three ovigerous females may be accommodated in a single breeding burrow, each female sequestered in a separate terminal chamber. The construction and defence of burrows specialized for breeding may be an adaptive response by males to the preferences females exhibit when selecting a breeding site.     

Elevated predation risk changes mating behaviour and courtship in a fiddler crab

The fiddler crab, Uca beebei, lives in individually defended burrows, in mixed-sex colonies on intertidal mud flats. Avian predation is common, especially of crabs unable to escape into burrows. Mating pairs form in two ways. Females either mate on the surface at their burrow entrance (''surface mating'') or leave their own burrow and sequentially enter and leave (''sample'') courting males'' burrows, before staying in one to mate underground (''burrow mating''). We tested whether perceived predation risk affects the relative frequency of these mating modes. We first observed mating under natural levels of predation during one biweekly, semi-lunar cycle. We then experimentally increased the perceived predation risk by attracting grackles (Quiscalus mexicanus) to each half of the study site in two successive biweekly cycles. In each experimental cycle, crabs were significantly less likely to mate on the side with more birds. Moreover, on the side with elevated predation risk, the number of females leaving burrows to sample was greatly reduced relative to the number of females that surface-mated. Males waved less and built fewer mud pillars, which attract females, when birds were present. We discuss several plausible proximate explanations for these results and the effect of changes in predation regime on sexual selection.     

Size-dependent Mating Behaviours of Male Sand-bubbler Crab,Scopimera globosa: Alternative Tactics in the Life History

Factors leading to the separation of mating behaviours were investigated in the sand-bubbler crab, Scopimera globosa. The crabs mated on the surface (surface copulation, SC) and underground (UC). UC males were large (old) whilst SC males were small (young). Burrowless females bred in the UC males' burrows. These females accepted UC in exchange for access to a burrow. UC occurred much more frequently than SC in the burrow area in which females oviposited. Most SC occurred in the water-saturated area affording a rich diet. SC was accepted by most large and small females in both areas and most UC by small females in the burrow area. SC was an alternative to UC for males in that there was a size dependence between types of copulation. These two mating behaviours involved different degrees of interaction with neighbouring males. Males attempting to carry a female to their burrows for UC were more often disturbed by other males than were males attempting SC. In the interaction for both UC and SC, larger males were likely to resist the disturbances. UC males needed their own burrows, but these burrows were not enlarged before mating. UC males have a higher paternity of eggs than SC males, because SC males' sperm is often displaced by other males. Thus, UC was a behaviour with relatively higher costs and benefits for male crabs than SC behaviour. Alternative mating behaviours in male S. globosa are conditional, and explained by intrasexual interactions and a male life history strategy with a trade-off between growth and reproduction. It is not likely that the size dependence of male mating behaviour is caused by mate preference of females for UC males in the burrow area.     

Issues to Be Considered in Counting Burrows as a Measure of Atlantic Ghost Crab Populations,an Important Bioindicator of Sandy Beaches

The use of indirect estimates of ghost-crab populations to assess beach disturbance has several advantages, including non-destructiveness, ease and low cost, although this strategy may add some degree of noise to estimates of population parameters. Resolution of these shortcomings may allow wider use of these populations as an indicator of differences in quality among beaches. This study analyzed to what extent the number of crab burrows may diverge from the number of animals, considering beach morphology, burrow depth and signs of occupation as contributing factors or indicators of a higher or lower occupation rate. We estimated the occupation rate of crabs in burrows on nine low-use beaches, which were previously categorized as dissipative, intermediate or reflexive. Three random 2-m-wide transects were laid perpendicular to the shoreline, where burrows were counted and excavated to search for crabs. The depth and signs of recent activity around the burrows were also recorded. The occupation rate differed on the different beaches, but morphodynamics was not identified as a grouping factor. A considerable number of burrows that lacked signs of recent activity proved to be occupied, and the proportions of these burrows also differed among beaches. Virtually all burrows less than 10 cm deep were unoccupied; the occupation rate tended to increase gradually to a burrow depth of 20–35 cm. Other methods (water, smoke, and traps) were applied to measure the effectiveness of excavating as a method for burrow counts. Traps and excavation proved to be the best methods. These observations illustrate the possible degree of unreliability of comparisons of beaches based on indirect measures. Combining burrow depth assessment with surrounding signs of occupation proved to be a useful tool to minimize biases.     

Habitat partitioning between prey soldier crab Mictyris brevidactylus and predator fiddler crab Uca perplexa

Interaction and habitat partition between the soldier crab Mictyris brevidactylus (prey) and the fiddler crab Uca perplexa (predator) were examined at a sandy tidal flat on Okinawa Island, Japan, where they co-occur. Both live in dense colonies. When the soldier crabs were released in the densely populated habitat of the fiddler crab, male fiddler crabs, which maintain permanent burrows in hard sediment, preyed on small soldier crabs and repelled large ones. Thus, the fiddler crabs prevented the soldier crabs from trespassing. It was also observed whether soldier crabs burrowed successfully when they were released 1) where soldier crab burrows just under the sand were abundant, 2) in a transition area between the two species, 3) an area without either species, and 4) where artificial tunnels simulated soldier crabs' feeding tunnels were made by piling up sand in the area lacking either species. In contrast to the non-habitat area, many soldier crabs burrowed in the sediment near the release point in the tunnel, transition and artificial tunnel areas. This indicates that the feeding tunnels on the surface attracted other crabs after emergence. When the large male fiddler crabs were transplanted into the artificial burrows made in soft sediment of the soldier crab habitat, all left their artificial burrows by 2 days. In the fiddler crab habitat, however, about one-third of the transplanted male fiddler crabs remained in the artificial burrows after 3 days. The soldier crabs regularly disturb the sediment by the up and down movement of their burrow (small air chamber) between tides. This disturbance probably prevents the fiddler crab from making and occupying permanent burrows. Thus, it appears that these crabs divide the sandy intertidal zone by sediment hardness and exclude each other by different means.     

Density affects mating mode and large male mating advantage in a fiddler crab

Fiddler crabs show two different mating modes: either females search and crabs mate underground in male burrows, or males search and crabs mate on the surface near female burrows. We explored the relationship between crab density, body size, the searching behavior of both sexes, and the occurrence of both mating modes in the fiddler crab Uca uruguayensis. We found that crabs change their mating mode depending on their size and crab density. Crabs mated mostly on the surface at low densities, and underground at high densities. The proportion of wandering receptive females but not courting males accounted for the variation in mating modes. This suggests that whether crabs mate underground (or on the surface) is determined by the presence (or absence) of searching females. We found that the change in the mating mode affected the level of assortative mating; males mating underground were bigger than those mating on the surface, suggesting active female choice. Given that fiddler crabs experience multiple reproductive cycles, they are prone to showing behavioral plasticity in their mating strategy whenever the payoffs of using different mating modes differ between reproductive events. Our results suggest that the incorporation of different levels of environmental variability may be important in theoretical models aimed at improving our understanding of the evolution of alternative mating tactics and strategies.     

Evidence for a permanent establishment of the snow crab (Chionoecetes opilio) in the Barents Sea

In the Atlantic the snow crab (Chionoecetes opilio) is naturally distributed on the northwestern side, i.e. eastern Canada and west Greenland. Until recently, there have been no observations of snow crab in eastern Atlantic. However, in 1990s single and occasional reports were made of crabs captured in the eastern part of the Barents Sea, presumably introduced through ballast water. Special attention during the annual bottom-trawl surveys in the Barents Sea during February 2004–2006 were given to include recordings of snow crab to evaluate if the introduced species has succeeded to establish a self-sustaining population in this region. Recordings of snow crabs were systematically noted and biological measurements carried out. The results confirm previous Russian observations of snow crabs in the northern region of Gåsebanken. In addition, a significant number of crabs were also found in the central region of the Barents Sea, mainly in deeper waters from 180 to 350 m depth. The sizes ranged from 14 to 136 mm carapace width. All females above 70 mm were berried with fertilised eggs. A major fraction (31% in 2005; 76% in 2006) of the crabs consisted of juveniles below 50 mm CW, providing evidence for successful recruitment. The small-sized crabs were exclusively found in Gåsebanken, identifying the main recruiting area at present for snow crab in the Barents Sea. The results obtained show that the snow crab is now adapted to the northeast Atlantic.     

Orientation of crustacean burrows in the Bay of Panzano (Gulf of Trieste, Northern Adriatic Sea)

Three burrow systems produced by Jaxea nocturna and one cluster of burrows produced by Upogebia pusilla where investigated in the Bay of Panzano, Northern Adriatic Sea, to determine preferred orientations. The distributions of dip directions differ between both producers. Steep shafts into the consolidated mud followed by large, shallowly inclined tunnels oriented in a manner similar to a spiral are characteristic for Jaxea nocturna burrows. In contrast, the Y-shaped burrows of Upogebia pusilla have entrance shafts that are less steep which are connected by a near-horizontal section, where a blind ending tunnel branches. Orientations of the dominating, shallowly inclined burrow parts are not randomly distributed in either Jaxea or in Upogebia burrows. Three preferred axial orientations with almost equal proportions in each direction are characteristic for the Jaxea burrow from the centre of the bay. This system transforms to a squared structure near the coast, where one direction parallels the shoreline and the other is oriented at right angles to the coast. The latter orientation demonstrates significant constancy in all investigated burrows. Upogebia burrow clusters coincide with the three preferred orientations of the Jaxea burrow from the bay centre, but the proportions of the directions are unequal. Burrow segments connecting the steep entrance shafts in Upogebia are oriented almost parallel to the shoreline, whereas at right angles to the coast the flat blind-ending tunnels incline towards the open sea. The study shows a strong coincidence between empirical and theoretical distributions of the dominating orientations in both species.     

Activity patterns, feeding and burrowing behaviour of the crab Ucides cordatus (Ucididae) in a high intertidal mangrove forest in North Brazil

Activity patterns, feeding and burrowing behaviour of the economically important semi-terrestrial mangrove crab Ucides cordatus (Ucididae, L. 1763) was studied in a high intertidal Rhizophora mangle forest stand in Bragança, North Brazil. Video observations in the rainy and dry season were conducted over 24 h cycles at different lunar phases to investigate the behaviour of these litter-feeding crabs outside their burrows. During the rainy season, crabs stayed inside their burrows for 79% and 92% of the time during day and night, respectively. Time spent for feeding, burrowing and other activities outside their burrows was significantly longer during the day with 9.9% (night: 1.7%) and at waning and waxing moon with 9% (full and new moon: 0.9%). At neap tides (no tidal inundation) foraging and feeding activities outside burrows were clearly light-dependent, increasing at dawn and decreasing at dusk. Highest activities during daytime relate to the visual localisation of food. During the dry season, crabs spent less time inside burrows at neap tides than during the rainy season (80% and 91%, respectively). However, time spent for feeding activities was similar during both seasons. During almost all observation periods crabs collected leaf litter, but rarely fed on it outside burrows. At neap tides nearly all available litter was collected, suggesting that the U. cordatus population is litter-limited during these times. At spring tides (regular tidal inundation) the surface activity of U. cordatus was tide-dependent. Crabs closed their burrow entrances 2-3 h before flooding and re-emerged as soon as the tide retreated. During the day, burrow maintenance was the second most frequent behaviour after feeding. Agonistic interactions were regularly observed and were mainly related to burrow defence. The mean foraging radius of the crabs was only 19 cm (max: 1 m) underneath high Rhizophora mangle trees where crab densities were high. The results point to a high competition for burrows and show that U. cordatus is territorial. It is concluded that several exogenous factors, in particular light, leaf litter availability, flooding of burrows and the presence of conspecifics are important in controlling the crabs' activity patterns.     

长江口芦苇和互花米草盐沼湿地蟹类洞穴分布特征及主要影响因子

蟹类洞穴是蟹类在潮间带盐沼生存、繁衍的特征性结构,具有重要的生态功能。洞穴分布特征及其影响因子的分析,是深入探讨蟹类及其洞穴的生态系统功能的重要基础。2015年10月,在崇明北滩单一芦苇(Phragmites australis)群落,单一互花米草(Spartina alterniflora)群落和芦苇-互花米草混合群落3种典型生境中,对蟹类洞穴的分布特征及其相关的大型底栖动物、植被、沉积物等的特征参数进行了调研与分析。结果表明,生境类型差异对蟹类洞穴分布特征及相关生境因子具有重要影响。蟹类洞穴的分布密度和开口直径在不同生境间存在显著差异(P0.05),且单一芦苇群落生境内洞穴密度要显著高于单一互花米草群落生境(P0.05),洞穴开口直径在单一互花米草生境要显著高于单一芦苇生境(P0.05);大型底栖动物生物量、密度、植物地下部分生物量在不同生境间差异不显著(P0.05),而植株密度、活植株高度、植物地上部分生物量以及沉积物含水率、p H、氧化还原电位在不同生境间存在显著差异(P0.05)。沉积物中值粒径,总氮含量和总碳含量在不同生境间的差异随深度不同会发生变化。不同生境主要生境因子的差异是导致蟹类洞穴分布特征不同的根本原因;蟹类洞穴分布特征受多个生境因子的综合作用。筛选的生境因子的组合虽然与洞穴分布特征具有显著相关性,但相关系数较小。未来研究中需要拓展生境因子涵盖范围,加强多因子综合作用分析。     

Orientation of crustacean burrows in the Bay of Panzano (Gulf of Trieste, Northern Adriatic Sea)

Three burrow systems produced by Jaxea nocturna and one cluster of burrows produced by Upogebia pusilla where investigated in the Bay of Panzano, Northern Adriatic Sea, to determine preferred orientations. The distributions of dip directions differ between both producers. Steep shafts into the consolidated mud followed by large, shallowly inclined tunnels oriented in a manner similar to a spiral are characteristic for Jaxea nocturna burrows. In contrast, the Y-shaped burrows of Upogebia pusilla have entrance shafts that are less steep which are connected by a near-horizontal section, where a blind ending tunnel branches. Orientations of the dominating, shallowly inclined burrow parts are not randomly distributed in either Jaxea or in Upogebia burrows. Three preferred axial orientations with almost equal proportions in each direction are characteristic for the Jaxea burrow from the centre of the bay. This system transforms to a squared structure near the coast, where one direction parallels the shoreline and the other is oriented at right angles to the coast. The latter orientation demonstrates significant constancy in all investigated burrows. Upogebia burrow clusters coincide with the three preferred orientations of the Jaxea burrow from the bay centre, but the proportions of the directions are unequal. Burrow segments connecting the steep entrance shafts in Upogebia are oriented almost parallel to the shoreline, whereas at right angles to the coast the flat blind-ending tunnels incline towards the open sea. The study shows a strong coincidence between empirical and theoretical distributions of the dominating orientations in both species.     

Small- and large-scale effect of the SW Atlantic burrowing crab Chasmagnathus granulatus on habitat use by migratory shorebirds

Here we address the question of whether the presence of the burrowing crabs Chasmagnathus granulatus affects small- and large-scale habitat use by migrant shorebirds. This crab is the dominant species in soft bare sediments and vegetated intertidal areas along the SW Atlantic estuaries (southern Brazil 28°S to the northern Argentinean Patagonia 42°S). They generate very extensive burrow beds in soft bottom intertidal areas. Our information shows that this burrowing crab affects the small-scale habitat use by shorebirds, given that shorebirds never walk through the funnel-shaped entrances of burrows. Given that crab burrow entrances occupy up to 40% of the intertidal area, there is a large decrease of available shorebird habitat in crab beds, restricting their activity to the spaces between the burrows. The southern migratory shorebird Charadrius falklandicus maximize the use of these areas by foraging closer to the burrows than the other bird species. Neotropical migrants, such as Calidris fuscicollis, Pluvialis squatarola and Tringa melanoleuca, used foraging paths that tended to maximize the distance from burrows, especially the distance to larger burrows. A field experiment showed that this was not necessarily due to a decrease in the availability of polychaetes near the crab burrows. A combination of landscape measurements and satellite images showed that crab beds covered up to 40% of the intertidal area of the Mar Chiquita coastal lagoon (37°40′S, Argentina), and nearly 100% of the intertidal area of the Bahia Blanca estuary (38°48′-39°25′S, Argentina). These two estuaries are located along the migratory flyway of Neotropical migratory shorebirds, but the Bahia Blanca estuary (area∼110,000 ha) shows a much lower shorebird diversity than Mar Chiquita (area∼4500 ha). The most common species in Bahia Blanca is the two-banded plover C. falklandicus, the species least affected by crabs at Mar Chiquita and which prefers to use high-density crab areas as foraging sites. The oystercatcher Haematopus palliatus was also most abundant in high-density crab areas, but they used these areas for resting. The abundances of preys varied during the study period and between the crab density areas, indicating that the use of these areas by birds is independent of crab density. However, burrowing crabs affect the depth distribution of polychaete and thus their availability to shorebirds. We suggest that this shorebirds-burrowing organism interaction could be generalized for other intertidal estuarine habitats.     

The validity of burrow counting in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat at Yangtze Estuary

It has been confirmed that the crabs play significant roles in the structure and function of coastal wetland ecosystems, such as mangroves and salt marshes. However it is not easy to estimate the abundance and density of burrowing crabs effectively, thus a further understanding of roles of crabs in these ecosystems has been lagged. Some studies have discussed the suitability of several census techniques, such as burrow counting method in estimating crab density in mangroves. The validities of burrow counting method and other census techniques in estimating crab density, however, has not been tested in salt marshes, especially where vegetation are dense. In this study, we tested the validity of burrow counting method in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat with dense vegetation of Phragmites australis and Zizania aquatica at Yangtze Estuary through comparing densities estimated by the burrow counting method and the excavation. Burrow counting averagely underestimated the density of C. dehaani by 15% and the degree of underestimation varied among vegetations and habitats (from an overestimate by 23% to underestimate by 41%). Burrow counting averagely overestimated the density of I. deschampsi by 43% and the degree of overestimate varied from 0% to 133% depending on the vegetations and habitats. The percentage of occupied burrows and the number of crabs sharing one burrow were important factors influencing the validity of estimating crab density through burrow counting method.     

The validity of burrow counting in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat at Yangtze Estuary

It has been confirmed that the crabs play significant roles in the structure and function of coastal wetland ecosystems, such as mangroves and salt marshes. However it is not easy to estimate the abundance and density of burrowing crabs effectively, thus a further understanding of roles of crabs in these ecosystems has been lagged. Some studies have discussed the suitability of several census techniques, such as burrow counting method in estimating crab density in mangroves. The validities of burrow counting method and other census techniques in estimating crab density, however, has not been tested in salt marshes, especially where vegetation are dense. In this study, we tested the validity of burrow counting method in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat with dense vegetation of Phragmites australis and Zizania aquatica at Yangtze Estuary through comparing densities estimated by the burrow counting method and the excavation. Burrow counting averagely underestimated the density of C. dehaani by 15% and the degree of underestimation varied among vegetations and habitats (from an overestimate by 23% to underestimate by 41%). Burrow counting averagely overestimated the density of I. deschampsi by 43% and the degree of overestimate varied from 0% to 133% depending on the vegetations and habitats. The percentage of occupied burrows and the number of crabs sharing one burrow were important factors influencing the validity of estimating crab density through burrow counting method.     

Impact of fiddler crabs (Uca spp.) on rates and pathways of benthic mineralization in deposited mangrove shrimp pond waste

The impact of fiddler crabs (Uca spp.) on benthic mineralization rates and pathways in deposits of shrimp pond waste (SPW) with planted mangrove trees (Rhizophora apiculata) were determined in the Ranong mangrove forest, Thailand. Sediment metabolism, measured as CO₂ flux, increased by 2- to 3-fold when either fiddler crabs or mangrove trees were present compared to control plots. Sulfate reduction rates (SRR) were always high and partitioning of various electron acceptors to total carbon oxidation revealed that sulfate reduction contributed by >90%, with iron reduction being important only near the sediment-water interface. However, significant iron reduction appeared down to 7 cm when bioturbation and plant roots were combined in the easily oxidizable mangrove sediment (MS), indicating that infaunal activity and plant roots were able to alter the substratum. Microprofiles around individual Uca burrows showed 46% lower SRRs in a 15-mm-thick oxidized layer around the burrows compared to the surrounding sediment. The burrow wall environment appears to be a zone of intense reoxidation of reduced compounds as indicated by low pools of reduced sulfide compounds and a high Fe(III) content. Despite the decreased SRRs near the burrow, and the introduction of Fe(III) to deeper sediment layers, fiddler crabs and mangrove trees have only limited impact on rates and partitioning of anaerobic carbon mineralization in the SPW. This lack of response was attributed to the relative small volume of sediment affected by crab activities.     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

Distribution and abundance of a nemertean egg predator ( Carcinonemertes sp.) on a leucosiid crab,Randallia ornata

The purple globe crab, Randallia ornata (Randall, 1839) (Decapoda: Leucosiidae) is a common crustacean found on sandy beaches from Northern California to Baja California, Mexico. An undescribed species of Carcinonemertes, which shares biological features with a partially described worm from Tasmania was recovered from R. ornata. The worm reaches 10 mm in length and secretes a sturdy tube with a distinctive spiral shape. The total prevalence of the worm on R. ornatawas 70% (85% for ovigerous female crabs, 67% for post-ovigerous female crabs, and 45% for male crabs). Intensities reached 32 worms per crab. Adult worms were found in crab egg masses, regressed adults were recovered from under the abdomen of post-ovigerous females, and encysted juveniles were found on the gill lamellae of non-ovigerous female crabs and occasionally from the gill lamellae of male crabs.