Sand Crab Research Articles

Digging in sand crabs: coordination of joints in individual legs.

Sand crabs use their multi-jointed legs to dig into sand. Combined movement and electromyogram (EMG) analyses showed that the pattern of intra-leg coordination in the legs of two sand crabs of different families (Blepharipoda occidentalis and Emerita analoga) is similar in legs 2 and 3, but very different in leg 4. For example, the sequence of proximal joint movements in legs 2 and 3 is elevation, retraction, depression and protraction (similar to backward walking in most decapods), but the sequence of proximal joint movements in leg 4 is elevation, protraction, retraction and depression (similar to forward walking). The synergies are the same during leg movements in sea water and in sand, suggesting that the same motor programme is used in both situations. At the transition from sea water into sand, however, both the frequency and amplitude of the EMG potentials increase, and the phasing of the motor output to leg 2 (and presumably leg 3) changes from proportional (both power and return strokes co-vary with period) to return stroke constant (power strokes co-vary much more with period than do return strokes). The motor output to leg 4 remains intermediate between proportional and return stroke constant in sea water and in sand. On the basis of the segmental specialisation of the motor patterns for the legs, we hypothesize that sand crab digging may be an evolutionary mosaic of disparate ancestral locomotor behaviours.

Experimental transmission of white spot syndrome virus (WSSV) from black tiger shrimp Penaeus monodon to the sand crab Portunus pelagicus, mud crab Scylla serrata and krill Acetes sp.

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 32:79-85 (1998) - doi:10.3354/dao032079 Experimental transmission of white spot syndrome virus (WSSV) from black tiger shrimp Penaeus monodon to the sand crab Portunus pelagicus, mud crab Scylla serrata and krill Acetes sp. K. Supamattaya1,*, R. W. Hoffmann2, S. Boonyaratpalin3, P. Kanchanaphum4 1Department of Aquatic Science, Faculty of Natural Resources, Prince of Songkla University, Hat Yai 90110, Thailand2Institute of Zoology, Fisheries Biology and Fish Disease, Kaulbachstr. 37, D-80539 Munich, Germany3Department of Fisheries, Kaset Klang, Bangkhen, Jaturjak 10900, Thailand4Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand *E-mail: skidchak@ratree.psu.ac.th White spot syndrome virus (WSSV) is the cause of a widespread epizootic in cultured shrimp in Thailand and many other countries in Asia. A number of crustacean and other arthropod species have been proposed as reservoirs for the virus by feeding trials and PCR assays. However, detailed histological studies are needed to confirm that suspected carriers have active viral infections. This study was carried out to determine whether 3 common crustacean residents of shrimp culture ponds (the sand crab Portunus pelagicus, the mud crab Scylla serrata, and krill Acetes sp.) could be experimentally infected with WSSV and, if so, what the effect of these infections would be. For krill, 3 routes of infection were tested (injection, ingestion and immersion) while for the crab species, only injection and ingestion were tested. WSSV preparations were made from naturally and experimentally infected Penaeus monodon as viral extracts from tissue homogenates (for injection and immersion) and as cut tissues (for ingestion). As determined by normal histology, electron microscopy and in situ DNA hybridization, all of the test species could be infected with WSSV. For krill, injection was the most effective route (100% mortality in 3 d), followed by immersion (100% mortality in 5 d) and ingestion (20% mortality in 9 d). For the crabs, injection was also the most effective route of infection. However, infection did not necessarily lead to mortality. Mortality for injected sand crabs was 100% in 8 d but for mud crabs only 20% in 9 d. By ingestion exposure, there was no mortality for either species over the 9 d experimental period, even though infection was confirmed by histological examination. Based on the results of this study, the crab species and krill can be considered as viral reservoirs, since they are able to carry the infection and may persist for significant periods in the shrimp farming environment. Viral transmission · White spot syndrome virus · Penaeus monodon · Crab · Krill Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 32, No. 2. Publication date: March 05, 1998 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1998 Inter-Research.

Subsistence shellfish harvesting in the Maputaland Marine Reserve in northern KwaZulu-Natal, South Africa: Sandy beach organisms

When the Maputaland Marine Reserve was proclaimed in 1986, conservation authorities held divergent opinions on whether traditional subsistence harvesting of the intertidal resources should be allowed to continue. A monitoring programme was therefore instituted, with the assistance of the local community, to quantify the intertidal harvest as a first step to assessing its sustainability. Catch and effort data for ghost crabs Ocypode spp. and mole crabs Emerita austroafricana and Hippa ovalis over a 7-year period are discussed here. Total (day and night) harvests declined from 146 000 ghost crabs and 129 000 mole crabs in 1989 to 86 000 ghost crabs and 80 000 mole crabs in 1993. However, effort also declined and the mean annual catch per unit effort for night catches, which comprised 89% of the total catch, changed little, averaging 28·3 ghost crabs and 24·5 mole crabs per harvester per night. About 8% of the ghost crab harvest is sold, generating an annual income of R1700. There are no indications that harvesting of ghost crabs and mole crabs is unsustainable, and harvesting effort appears to be decreasing. No change in management is recommended.

Digging in sand crabs (Decapoda, Anomura, Hippoidea): interleg coordination

Sand crabs (Decapoda, Anomura, Hippoidea) are highly specialised for digging into sand using their thoracic legs. Using video-recording and electromyography, we examined the digging leg movements of three species of sand crabs belonging to two families: Blepharipoda occidentalis (Albuneidae), Lepidopa californica (Albuneidae) and Emerita analoga (Hippidae). The digging patterns of all three species are similar. The ipsilateral legs 2 and 3 are tightly coupled and shovel sand forward from underneath the animal, whereas the movements of leg 4 are more variable, apparently stirring up sand and providing the purchase for rearward descent into the sand. The digging patterns of B. occidentalis and L. californica resemble each other more than either resembles that of E. analoga. In the albuneids, leg 4 cycles at the same frequency as legs 2 and 3, and both albuneid species switch gait from bilateral alternation to synchrony midway through digging. In E. analoga, right and left legs 2 and 3 always alternate. Legs 4 can cycle at about twice the frequency of legs 2 and 3, and they tend to move in bilateral synchrony during high-frequency leg movements (e.g. at the start of digging); their bilateral coupling becomes variable during low-frequency movements. Sand crab digging may have originated as a modified form of walking, but this behavioural innovation subsequently diverged in the sand crab superfamily.

Coordination between the legs and tail during digging and swimming in sand crabs

Rhythmic leg movements and tailflipping are mutually exclusive behaviours in most decapod crustaceans, but sand crabs (Anomura: Hippoidea) combine leg movements with simultaneous tailflipping or uropod beating for both digging and swimming. We examined the coordination between the legs and tail (abdomen and tailfan) of Blepharipoda occidentalis, Lepidopa californica (Albuneidae), and Emerita analoga (Hippidae). When either albuneid swims, the tail cycles at a higher frequency than the legs, and the two rhythms are not coupled. When albuneids begin digging, the tail's frequency drops to that of the legs, and its rhythm becomes phase coupled to the legs. In E. analoga the legs seldom move during swimming by uropod beating. During digging the frequency of the uropods and fourth legs starts at about double that of the second and third legs, but drops to that of the second and third legs as digging progresses. The fourth legs in E. analoga are coupled with the uropods; their outward movement (= power stroke) is concurrent with the uropod return stroke. The familial differences in leg coordination and in the coordination of the legs and tail account for the smooth descent of E. analoga beneath sand compared to the stepwise descent of the albuneids.

A map of distal leg motor neurons in the thoracic ganglia of four decapod crustacean species.

We describe the numbers, central positions, and axonal exit routes of the distal leg motor neurons of four decapod species: squat lobsters (Munida quadrispina), spiny sand crabs (Blepharipoda occidentalis), mole sand crabs (Emerita analoga), and signal crayfish (Pacifastacus leniusculus). As predicted by previous physiological and anatomical identification of axons at the periphery in crayfish and lobsters, cobalt backfills reveal about seventeen cell bodies, which are found in four areas in the ganglion. By comparing their positions and neurite morphologies with the previously identified neurons, functional identifications could be assigned to most of them. The common inhibitor and stretcher inhibitor are located posterior-medial. An anterior-lateral cluster of about twelve somata includes the opener identical to stretcher excitor, one of two bender excitors (bender excitor alpha), four flexor excitors, and two excitors each to the extensor, reductor, and closer muscles. Three cell bodies are posterior-lateral. Of these, the opener inhibitor and the second bender excitor (bender excitor beta) are on about the same dorsoventral plane. The third posterior-lateral cell, the accessory flexor excitor, is noticeably more dorsal than the other two posterior-lateral cell bodies. The reductor muscle is innervated by at least three neurons: the putative common inhibitor and fast and slow excitors. None of the leg motor neurons project into the contralateral hemiganglion. The most variable feature across species is the nerve through which motor axons exit the ganglion: axons leave the ganglia via different routes in each of the four species examined. These differences in the axons' pathway, however, are insufficient to explain the differences in motor output and behaviour of these four species.

A crab in the lab that identified high and low tides in the sea two miles away

The author describes his 'choice' of a Ph.D. dissertation topic in the sixties, the interactions with his advisor, the rhythms of the mole crab and the serendipity of success in research, in a candid and humorous fashion.

Divergence and zoogeography of mole crabs, Emerita spp. (Decapoda: Hippidae), in the Americas

Six of the nine described species of the mole crab genus Emerita are distributed in the Americas, two [E. analoga (Stimpson, 1857) and E. rathbunae Schmitt, 1935] on the west coast, and four [E. benedicti Schmitt, 1935, E. brasiliensis Schmitt, 1935, E. portoricensis Schmitt, 1935 and E. talpoida (Say, 1817)] on the east. The presence of an extended planktonic larval stage in all Emerita species suggests high dispersal potential and the possibility of extensive gene flow among conspecific populations. Two taxa were sampled to study the extent of gene flow between widely separated conspecific populations: E. analoga (California and Chile) and E. talpoida (Massachusetts, South Carolina, and the west coast of Florida), while all other taxa were characterized from a single location. Portions of two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA (16S rRNA) were sequenced. For data analysis, approximately 500 bp (COI) and 400 bp (16S rRNA) were examined. Estimated genetic divergence of 5.41% in COI between E. talpoida populations sampled from the Gulf of Mexico and the Atlantic coast, and 3.47% between E. analoga sampled in Chile and California, indicates that in both cases there has been no recent gene flow between disjunct populations. Additional molecular and morphological studies are necessary to decide whether disjunct populations should be accorded specific status. We predict that many marine invertebrates with antitropical distributions similar to E. analoga may consist of sibling species. In contrast to relationships inferred earlier from distribution patterns, parsimony analyses of both COI and 16S rRNA data yield similar phylogenetic trees in which E. analoga is separated from a clade composed of other species in the Americas; a bootstrap value (67%) in the COI inferred tree marginally supports the separation, but the same tree topology with a higher bootstrap value (84%) is obtained with 16S rRNA sequence data. Genetic divergence among the taxa indicates that the Emerita species constitute an old group and that distribution of species has been modified by past climatic and geological events.

Environmental physiology of the mole crab Emerita asiatica, at a power plant discharge area on the east coast of India

Cage experiments at the discharge area of Madras Atomic Power Station (MAPS) facilitated studies of thermal tolerance in Emerita asiatica. At the laboratory, oxygen consumption at various temperatures and varying salinities was also investigated. In the field 100% mortality of crabs was recorded at the Condenser Cooling Water Pumps (CCWP) discharge site compared to no mortality at the Processed Sea Water Pumps (PSWP) site. This observation implicated temperature as a stress factor at the CCWP outfall, because other factors, including residual chlorine and water velocity, were the same at the PSWP and CCWP sites. Laboratory experiments on tolerance revealed that 38·5°C was lethal to mole crabs. The time taken for 100% mortality decreased as the temperature increased from 35 to 40°C. Oxygen metabolism showed a progressive increase with temperature from 29 to 36°C, and declined at 37°C. The influence of salinity on oxygen consumption was marginal at salinities of 20 to 35‰ but, when reduced to 15‰, the oxygen consumption declined. The present study thus indicates that temperature could be the lethal factor, determining the distribution of mole crabs near the power station, where water temperature can exceed 40°C.

Isolation and characterization of high molecular weight glycoproteins from embryonated eggs of Emerita asiatica

The main yolk protein of Emerita asiatica is comprised of glycolipoprotein conjugated to carotenoid pigment. In the present study the embroynated eggs of the mole crab, Emerita asiatica, were tested for the presence of O-linked glycoproteins. The high molecular weight glycoprotein was extracted in 0.2 M phosphate buffer, pH 6.0 with 8 M urea and fractionated by size exclusion chromatography on Sephorase CL 4B column using the same buffer system. The high molecular weight glycoprotein was excluded and the included peak contained low molecular weight glycoproteins. The rechromatographed void fraction from the delipidated egg homogenate was free of low molecular weight components as confirmed by SDS-PAGE. 125I wheat germ agglutinin and peanut agglutinin overlay and the recently developed modified Morgan-Elson assay confirm that the egg contains mucin-type glycoproteins. Monosaccharide analysis of the void fraction was performed. High performance anionic exchange chromatography (HPAEC) shows the presence of GaINAc, GIcNAc, galactose, fucose, mannose and glucose. The identified and characterized high molecular weight glycoprotein is a new class which may play a role in the receptor mediated uptake of vitellogenin, a yolk precursor protein synthesized elsewhere.

Replacement of an inherited stretch receptor by a newly evolved stretch receptor in hippid sand crabs

Primary sensory neurons that are motoneuron-like in morphology and often nonspiking (transmit afferent signals as graded depolarizations) characterize an unusual type of stretch receptor in decapod crustaceans. Nonspiking and spiking receptors occur in similar positions at homologous joints in different species and have been presumed to be homologous, the spiking one considered "primitive". To better understand the evolutionary origin of these stretch receptors and why some are nonspiking, we examined the spiking telson-uropod stretch receptors in the spiny sand crab Blepharipoda occidentalis (Albuneidae) and the squat lobster Munida quadrispina (Galatheidae) and compared them with the nonspking telson-uropod stretch receptor of the mole sand crab Emerita analoga (Hippidae). The position, morphology and responses to stretch of the sensory neurons, and the ultrastructure of the elastic strand portion of the receptor are similar in M. quadrispina and B. occidentalis, except that in B. occidentalis the receptor muscles are substantially smaller and the extracellular matrix of the elastic receptor strand is both more extensive and more organized, reminiscent of the ultrastructure of E. analoga's nonspiking receptor. We conclude that the spiking telson-uropod stretch receptors of albuneids and galatheids are homologous. The differences in the ultrastructure of their receptor strands imply that the efficiency of coupling receptor length change to deformation of the dendritic termini increases in the order M. quadrispina < B. occidentalis < E. analoga. The spiking and nonspiking telson-uropod stretch receptors differ anatomically in three major respects that appear to preclude their homology. (1) The receptor strands are on opposite sides of a conserved muscle. (2) The sensory somata are in different regions of the sixth abdominal ganglion: a lateral cluster of somata for the spiking sensory neurons and two medial clusters, one anterior, one posterior, for the nonspiking sensory neurons. (3) The neuropil projections of the sensory neurons are different. We conclude that the hippid's nonspiking telson-uropod stretch receptor evolved de novo and not by modification of the ancestral anomuran telson-uropod stretch receptor (which Hippidae have lost).

Reproduction and Growth of the Commercial Sand Crab, Portunus pelagicus (L.) in Moreton Bay, Queensland

The biology of the commercial sand crab Portunus pelagicus is described in subtropical Moreton Bay, Queensland, Australia. The population samples were characterized by more males than females. Recruitment of O+ yr individuals occurred throughout the year, although it was greatest during spring. Crabs attained sexual maturity in their first year of life. After rapid growth of juveniles in shallow inshore habitats during summer and autumn, molting and growth slowed during winter. Von Bertalanffy 613 growth 19 functions were derived as follows 1 1 = 175 (1-e·l.597(t-0,203)) for males, and 1 1 = 170 (1-e-l.C-0.1a)) for females. Crabs moved further offshore as they in­creased in size. Ovigerous females were present throughout the year, although their proportion peaked during August-October. Maximum gonad development or male P. pelagicus was during May, whereas the peak period or female gonad activity occurred in July. The presence or many postmolt mature females with spermatophores in their spermathecae during May-June, confirmed those months as the major mating period.

Geographic variation in life history of the sand crab, Emerita analoga (Stimpson) on the California coast: Relationships to environmental variables

Geographic variation and the influence of environmental factors on life history characteristics of populations of a sandy intertidal decapod, Emerita analoga, Stimpson, inhabiting beaches along 8° of latitude on the California coast in midsummer were investigated for 5 yr. Female size at maturity, largest and smallest ovigerous crab size, and largest male crab size, expressed as carapace lengths, increased from south to north and were 1.5 to 3 times greater in northern than in southern populations. The observed trends in life history were associated with environmental factors that varied on regional (water temperature) and local scales (food availability and physical characteristics related to beach morphodynamics) using simple and multiple linear regression analyses. Incorporating regionally and locally varying environmental factors into a multiple linear regression model provided a better predictor of life history characteristics than any single factor. In every year, the four life history characteristics were negatively correlated with surf zone water temperature, which varied regionally and was correlated with coastline distance. Female size at maturity and the largest and smallest ovigerous crab sizes were positively correlated with food availability, estimated by chlorophyll a concentration, which was not correlated with coastline distance. Life history characteristics were not correlated with any of the beach morphodynamic variables in simple regressions. Removal of variation associated with water temperature and chlorophyll a in multiple linear regression analyses yielded positive correlations between the sizes of the largest and smallest ovigerous crabs and the size of the largest male crab, and a beach characteristic, an index of sediment size and sorting, which was not correlated with coastline distance. Female size at maturity, largest and smallest ovigerous crab sizes and largest male crab size were correlated in each year, implying that these life history traits are influenced by similar mechanisms. Little interannual variation occurred in the geographic patterns observed in life history traits. Life history traits examined in our study were correlated between years, suggesting that interactions between settlement, growth, survival, and enviroment variables were relatively consistent during our study.

Evaluation of the Morrison soft turtle excluder device: prawn and bycatch variation in Moreton Bay, Queensland

The present study assesses the effects of a Morrison soft turtle excluder device (TED) upon catch rates of commercial prawn, fish and non-commercial bycatch species at an essentially oceanic site and an estuarine site. Effects of the TED upon catch rates were highly variable. Reductions in prawn catch ( Penaeus plebejus, Penaeus esculentus, Metapenaeus bennettae) in the TED-equipped net varied between no significant reduction to a 29% reduction, by weight, depending on location and season. Reductions in prawn catch could not be attributed to the loss of prawns by species or solely to the selective loss of prawns on the basis of size. Fish catches ( Sillago sp., Platycephalus sp., suggrundus sp.) were highly variable and showed no significant difference between control and TED-equipped nets. Catches of marketable sand crabs ( Portunus pelagicus) were reduced by more than 50% in the TED-equipped net. Large bycatch animals, such as shovelnose rays ( Rhinobatus batillum), sand rays ( Amphotistius kuhlii) and turtles ( Caretta caretta), were caught occasionally in the control net but were absent from the TED-equipped net. Non-commercial bycatch, composed of fish and crustaceans, was reduced by up to 32% by weight in the TED-equipped net. Results from this study suggest that it is difficult to predict accurately the effect of the Morrison soft TED upon catches of prawns and bycatch for all trawl locations and seasons.

Low Dose Irradiation Affects Microbiological and Sensory Quality of Sub‐Tropical Seafood

ABSTRACTSweetlip (Lethrinus miniatus), red emperor (Lutjanus sebae), mackerel (Scomberomorus commerson), whiting (Sillago ciliata), mullet (Mugil cephalus), barramundi (Lutes culcarifer), sand crab (Portunus pelagicus), Moreton Bay prawns (Metapenaeus spp.) and king prawns (Penaeus plubujus) were irradiated at doses of 0, 1, 3 and 5 kGy. A dose of 1 kGy resulted in a 1.5 to 4 log reduction in total bacterial numbers. Sensory quality decreased with increasing radiation dose except for Moreton Bay prawns and cooked king prawns, which were acceptable after a 5 kGy dose. Doses higher than 3 kGy caused adverse odor and flavor changes in Moreton Bay and cooked king prawns. A dose of 1 kGy could extend storage life of any of the species without adversely affecting sensory quality.

Parasitism of the commercial sand crab Portunus pelagicus (L.) by the rhizocephalan Sacculina granifera Boschma, 1973 in Moreton Bay, Queensland, Australia

In Moreton Bay, Queensland, externae of Sacculina granifera Boschma were found in 7.0% of adult males and 123% of adult females of Portunus pelagicus. Infection rates were seasonal for both sexes and higher in the adult female population, with more than 20% of adult females carrying externae during some summer months. Infection rates were less than 3% in areas outside the bay and generally highest in the southern and central bay. Nineteen males and 15 females had abdominal scars where externae had become dislodged. The gonads of most parasitized crabs were underdeveloped, but 5.6% of externa-bearing females and 10% of externa-bearing males also had well developed gonads. Two female sand crabs were found with both a small egg mass and a mature externa (a condition not previously reported). Size distributions of infected and uninfected adult crabs were similar, suggesting that large crabs as well as juvenile crabs were likely to be infected.

Susceptibility of larval and juvenile instars of the sand crab, Portunus pelagicus (L.), to sea water contaminated by chromium, nickel or copper

The acute toxicities of Cu2+, Ni2+ and Cr(V1) in sea water to larval life stages of the sand crab, Portunus pelagicus, were determined in a laboratory study and compared with published data for the toxicity of heavy metal cations to this species. This showed the relative acute toxicities to be in the order Cu2+ &gt; Cd2+ ≥ Zn2+ &gt; Ni2+&gt; Cr(V1). Sublethal effects attributable to exposure to sea water contaminated by some of these cations were investigated for both larval and juvenile crab life stages. The effects quantified were inhibition of larval moulting, increase in the duration of development period, and reduced size achieved by successive juvenile crab instars. In each case, the chronic levels of cation contamination in seawater associated with these effects exceeded the Australian guidelines for the protection of marine aquatic ecosystems, but in some cases the safety margin was less than an order of magnitude. In addition, bioconcentration relationships for Cr were determined on a whole-animal and an exoskeleton basis.

Larval settlement and metamorphosis in the sand crab Emerita talpoida (Crustacea: Decapoda: Anomura)

The effects of various potential cues on the survival and time to metamorphosis of larvae of the sand crab Emerita talpoida (Say) were examined. Zoeal duration, which ranged from 25 to 43 d, was not correlated with subsequent megalopal survival but had a weak, negative correlation with the duration of the megalopal stage. Neither food, sand nor water from containers with adults directly affected megalopal survival or duration. In a second experiment, the presence of sand both increased the probability of survival and shortened the duration of late zoeal stages. This is the first experimental evidence for delayed zoeal metamorphosis in a decapod. Settlement of E. talpoida appears to occur primarily during the zoeal phase, not at the megalopal stage.

Trypsin‐like Enzyme from Sand Crab (Portunus pelagicus): Purification and characterization

ABSTRACTStudies with synthetic substrates and specific inhibitors indicated that a protcinase from the hepatopancreas of the sand crab (Portunus pelngicus) was a trypsin‐like serine proteinase. The molecular weight of the enzyme estimated by gel filtration and mass spectrometry was ∼ 25,000, whereas SDS‐PAGE indicated a molecular weight of 34,800. The optimum temperature for hydrolysis of azocasein was 60°C, while inactivation of 50% enzymic activity occurred at 68°C. The enzyme, optimally active at pH 8.0 towards p‐tosyl‐L‐arginine methyl ester and unstable at acid pH, was high in acidic amino acid residues. Under some conditions ihe knzyme readily autodigested. Our results can help understand and avoid problems of meat softening during storage of seafood products.

Impact of parasites on the reproduction and fecundity of the blue sand crab Portunus pelagicus from Moreton Bay, Australia

The rhizocephalan Sacculina granifera had a marked effect on the gonad development and growth of its host Portunus pelagicus. Crabs were frequently castrated by the parasite but, in some cases, castration was incomplete, ie the reproductive potential of the infected host is not necessarily zero. Crabs were susceptible to infection by the parasite at any size/age, but juvenile crabs were more frequently infected. The abundance of the egg predator Carcinonemertes mitsukurii was correlated with salinity and temperature, but not with egg mortality on the host. Hence, the worms had little impact on host fecundity. The nicothoid copepod Choniosphaera indica was the major source of egg mortality on P. pelagicus. Mean mortality due to the copepod was 2.4% (range 0-19.6%). While the copepod may be capable of rapid development and infection of crab clutches, it had a negligible effect on host fecundity because it occurred at relatively low intensities (1-1821 copepods host). The parasite and egg predators exhibited seasonal patterns in their infections of the host population. Seasonal patterns were found in the molting, mating, gonad development, breeding, and sex ratios of crabs. -from Authors