Diet Of Crabs Research Articles

Growth and food intake models in Octopus vulgaris Cuvier (1797): influence of body weight, temperature, sex and diet.

Multiple regression analysis was used to develop mathematical models applicable to the growth and food intake of Octopus vulgaris. The variables considered were: body weight (Bw: 175–3,500 g), temperature (T: 13–28 °C), sex (S: male = 0, female = 1) and diet (D: bogue fish = 0, crabs = 1). Growth and food intake may be succesfully expressed by means of the following equations: Ln (AGR + 14) = −2.0135 + 0.0895 Ln Bw + 0.5087 T − 0.0142 T2 + 0.2997 D (R2 = 71.79; ANOVA p < 0.0001) and Ln (AFR) = − 5.6577 + 0.5137 Ln Bw + 0.5266 T − 0.0132 T2 + 1.1135 D (R2 = 78.71; ANOVA p < 0.0001), where AGR: absolute growth rate, AFR: absolute feeding rate, Bw: body weight, T: temperature and D: diet. In our experimental conditions, sex did not affect growth or food intake. The optimum temperature for growth (17.5 °C) and food intake (20 °C) was independent of body weight. Growth and food intake were higher with the crab diet. Nevertheless, food efficiency was better for animals fed on fish (bogue). Maximum food efficiency was reached at 16.5 °C for both diets. When the temperature was above 23 °C, weight losses and mortality were recorded; the temperature at which this occurred depending on body weight and diet, so that smaller and bogue-fed individuals were more sensitive to increasing temperatures. O. vulgaris growth may provide optimum economic performance from 16 to 21 °C. This range is too narrow, considering the wide natural range (12–29 °C) in some Mediterranean areas. Therefore, O. vulgaris growth will be limited by seasonality of temperature or must be carried out with other systems (e.g. recirculation in closed systems with temperature control) for it to be economically viable.

Feeding of the spider crab Maja squinado in rocky subtidal areas of the Ría de Arousa (north-west Spain)

The diet of the spider crab, Maja squinado, was studied in the rocky subtidal areas of the Ría de Arousa (Galicia, north-west Spain), by analysing the gut contents of crabs caught in the summer and winter of 1992. The highly diverse diet was made up primarily of macroalgae and benthic invertebrates that were either sessile or had little mobility. The most important prey were the seaweeds Laminariaceae (43% of the frequency of occurrence and 15% of the food dry weight), Corallina spp. (38% and 3%), molluscs [the chiton Acanthochitona crinitus (15% and 1%), the gastropods Bittium sp. (30% and 2%), Trochiidae and others and the bivalve Mytilus sp. (32% and 12%)], echinoderms [the holothurian Aslia lefevrei (32% and 18%) and the echinoid Paracentrotus lividus (16% and 7%)] and solitary ascidians (18% and 6%). The variability in diet composition was determined by the season (Laminariaceae, Corallina spp., P. lividus, Mytilus sp., gastropods and chitons appeared in greater frequency in winter, while the solitary ascidians and A. lefevrei were consumed to a greater extent in summer) in addition to sexual maturity (prey such as Bittium sp. or Trochiidae were more common in juveniles). Moreover, the changes in the food consumption rate were linked primarily to the moult stage. Feeding activity plummeted during the phases immediately preceding and following ecdysis (stages D0–D3–4 and A), and the diet was less diverse during these phases. No feeding differences were found that could be linked to sex. The composition of the diet of Maja squinado appears to be determined by the seasonal abundance of the different prey in subtidal rocky areas and by their availability (depending on their behavioural and anatomical characteristics, mainly mobility and the presence of hard external structures). Moreover, life history factors have little importance in the variability of the diet composition and only the moult cycle has a considerable effect on feeding rate.

INCIDENCE OF AUTOTOMY IN NEW ENGLAND POPULATIONS OF GREEN CRABS, CARCINUS MAENAS, AND AN EXAMINATION OF THE EFFECT OF CLAW AUTOTOMY ON DIET

ABSTRACT Like other decapod crustaceans, the green crab Carcinus maenas can actively amputate limbs by the process of autotomy. The loss of limbs may have consequences for the future fitness of an individual, since it is likely to impose energetic costs, including a reduced foraging efficiency. This study examined the occurrence of limb loss and the effects of claw autotomy on the diet of green crabs. Green crabs were collected from May-October 1995 from sites in New England. All crabs (N = 1,504) were examined in the field, and 402 adult crabs (>30 mm wide) were included in the analysis of gut contents. Overall, females experienced more injuries (38.4% missing at least I limb, N = 277; 17.89% missing 1 or both claws, N = 129) than males (32.18% missing at least 1 limb, N = 252; 14.8% missing 1 or both claws, N = 116). The overall incidence of autotomy generally increased with increasing crab size. but the incidence of claw autotomy did not. The most common identifiable materials in the guts were the hard parts of molluscs, arthropods, and annelids. The contents of the guts differed between sites, but was not significantly different for crabs missing claws than for intact crabs. Thus, the loss of a single claw does not seem to alter crab diet.

Omnivory in the diet of juvenile dungeness crab, Cancer magister Dana

Juvenile Dungeness crab ( Cancer magister Dana) have always been considered strict carnivores; however, early instars have been observed ingesting filamentous, epiphytic diatoms in the field. To investigate the potential importance of diatoms in the diet of this species, wild-caught megalopae were raised to the third juvenile instar on a variety of dietary treatments. Although the animals that were fed only filamentous diatoms ( Melosira sp. and Grammatophora sp.) had intermolt periods 20–25% longer than those raised on mussel ( Mytilus sp.) flesh or a mix of diatoms and mussels, there was no difference in molt size increment between the treatments. This ability to utilize such alternative food resources at a lower trophic level may be especially important in years of high settlement into coastal estuaries, when large numbers of juvenile crab are known to cause dramatic reductions in prey densities.

Seasonal patterns of food availability: influences on the reproductive output and body condition of the herbivorous crab Grapsus albolineatus.

Rocky shores in Hong Kong experience marked seasonal differences in climate resulting in seasonal changes in macroalgal assemblages. The tropical rocky shore crab, Grapsus albolineatus, feeds selectively on filamentous algae through the year but the abundance of these algae and foliose algae is greatly reduced during the summer when encrusting algae dominate the shores and the crab's diet. This switch in diet may have implications for the reproductive output of this crab. Standing crop of algae varied greatly through the year, peaking in March and April, when the nutritional quality of the algae was also highest. On the shore, available algal protein and energy were both lowest in July. The crab selected an algal diet rich in nutrients than that available to it on the shore for all months of the year except September to December for protein, and July and August for energy. The input of animal matter considerably increased the protein content of the diet, but made little difference to the energy content. Growth and body condition were greatest during March and June, coinciding with the peak in algal biomass. Storage of nutrients in the hepatopancreas of G. albolineatus commenced in November, coinciding with the increase in biomass and quality of algae on the shores, and then, peaking in May and June, these nutrients were utilised by the reproductive organs during the reproductive season which ran from April to November. The middle of the reproductive season coincided with the period when the standing crop of algae on the shore was at its lowest levels and poorest quality. Cycles of growth, reproduction and storage in G. albolineatus appear to be directly influenced by seasonal patterns of algal food availability. Nutrient storage in the hepatopancreas, during periods when food is nutritionally rich and is most abundant, does not guarantee reproductive success of the crab, but appears to be a prerequisite. Selection of an optimal diet (energy- and protein-rich) in a seasonal environment by ingesting abundant nutrient-rich algal species and the opportunistic consumption of animal matter strongly influences growth and reproductive output of G. albolineatus.

Behaviour and energetics of whelks, Buccinum undatum (L.), feeding on animals killed by beam trawling

Whelks, Buccinum undatum, are potentially important scavengers of animals damaged or killed as a result of beam trawling. In order to assess the ability of whelks to scavenge these moribund animals, and the consequences of this to energy flow, we presented them with four different species that were either damaged on the seabed or died as a result of capture by beam trawling. Whelks ate swimming crabs, Liocarcinus depurator, purple heart urchins, Spatangus purpureus, and a gadoid fish, the pouting, Trisopterus minutus, but not plaice, Pleuronectes platessa. Whelks moved most rapidly towards swimming crabs, suggesting that these were the most preferred prey type. Although the rate of energy intake was highest when whelks fed on sea urchins, when fed to satiation they acquired most energy from swimming crabs. When presented with whole animals, whelks fed preferentially on different body tissues, e.g. they consumed the eyes of pouting first, and never ate the gills or carapace of swimming crabs. Absorption efficiency was highest when fed a diet of swimming crabs (93%) and lowest when fed pouting (83%). Whelks are able to efficiently utilise animals killed by beam trawling, and our results indicate that they prefer the most energetically rich species. In areas of intense beam trawling, such as the southern North Sea, dead or moribund animals which result from these activities could constitute a considerable proportion of whelk diets.

Diet composition influences the fitness of the herbivorous crab Grapsus albolineatus.

The tropical rocky shore crab Grapsus albolineatus feeds primarily on filamentous algae but eats animal matter whenever it is available. During the summer the crab's diet switches to encrusting algae due to a die-off of filamentous algae. As a result of the switch the nutrients in the diet of the crab vary seasonally and may influence the fitness of the crab. Maintenance, growth, reproductive performance and nutrient storage of crabs were examined under four dietary regimes of increasing nutritional value ranging from low organic to high protein content. The nutritional quality of these diets significantly affected crab survival and moulting. Crabs fed on the nutritionally superior diet of algae and meat exhibited enhanced growth, higher levels of energy in the reproductive organs and stored more energy in the hepatopancreas than did individuals on the shore and crabs fed only on algal diets in the laboratory. Filamentous algae were a better food source than other algae, resulting in fewer deaths and superior levels of maintenance and growth. Growth and maintenance can occur on a pure algal diet, but reproductive performance and nutrient storage require some degree of added nutrients in the form of animal matter in the diet. Crabs fed coralline or foliose algae had higher mortality and fewer successful moults than crabs fed the other two diets. The fitness of G. albolineatus appears to be limited by the amount of extra nutrients obtained from animal matter. The opportunistic consumption of animal material in the form of carrion, or of animals associated with dietary algae, could be a key factor in the reproductive success of this crab.

Trophic relationships between polychaetes and brachyuran crabs on the southeastern Brazilian coast

Polychacte annelids constitute an important fecding resouree for several spccics of the benthic and dcmersal marine fauna. Their role in the energetic flow of marine ecosystems has been made evidenced by thcir contribution to the diet of fishes (Amaral & Migotto, 1980;Ben-Elihau et 01.,1983;Ben-Elihau & Golani, 1990;Amaral et al., 1994) and crabs (Schembri, 1981; Le Calvez, 1984; 1987;HalI et ai., 1990). The main difficultywhcn studying the diet of crabs is the identification of stomach contents to specific leveI. Nevertheless, concerning the polychaetes, the presence of certain structures which are more resistant to digestion, such as setae, uncini, hooks, mouthpieces and opercula, allowsthe determination to familyleveI.The analysis at this leveI is justified by the great within-family homogeneity regarding the trophic group, position in the sediment and feeding strategies, alI of whichare in agreement with the conccpt of fceding guilds by Fauchald & Jumars (1979). The feeding guild approach has been demonstrated to be rather useful in trophic ecology studies (Maurer & Leathem, 1981;Bianchi & Morri, 1985;Paiva, 1993). Considering that brachyuran crabs are the main megabenthic group (Sartor, 1989; Pires, 1992) and polychaetes the main macrobenthic group in the studied arca (Paiva, 1990; PiresVanin, 1993), the knowledge of their interrelations are fundamental in arder to understand the local trophic web.

Diet, food preference, and algal availability for fishes and crabs on intertidal reef communities in southern California

Herbivory by wide-ranging fishes is common over tropical reefs, but rare in temperate latitudes where the effects of herbivorous fishes are thought to be minimal. Along the west coast of North America, herbivory by fishes on nearshore reefs is largely restricted to a few members of the Kyphosidae, distributed south of Pt. Conception. This paper presents information on natural diets and results from feeding choice experiments for two abundant kyphosids from intertidal habitats in San Diego, California —Girella nigricans andHermosilla azurea, and similar data for the lined shore crab,Pachygrapsus crassipes, which also forages over intertidal reefs. These results are compared with the availability of algae in intertidal habitats measured during summer and winter, on both disturbed and undisturbed habitats. The diets of juveniles ofG. nigricans andH. azurea collected from nearshore habitats were dominated by animal prey (mainly amphipods), but adults of these fishes, andP. crassipes, consumed algae nearly exclusively, with 26, 10, and 14 taxa of algae identified fromG. nigricans, H. azurea, andP. crassipes, respectively. Algae with sheet-like morphologies (e.g.Ulva sp.,Enteromorpha sp., members of the Delesseriaceae) were the principal algae in the diets of the fishes, and calcareous algae (e.g.Corallina sp.,Lithothrix aspergillum) and sheet-like algae (Enteromorpha sp.) comprised the greatest identifiable portion of the shore crab's diet. Feeding choice experiments indicated that the fishes preferred filamentous algae (e.g.Centroceras clavulatum, Polysiphonia sp.,Chondria californica) and sheet-like algae (e.g.Enteromorpha sp.,Ulva sp.,Cryptopleura crispa) over other algal morphologies, whereas the shore crab chose jointed calcareous algae (e.g.Lithothrix aspergillum, Corallina vancouveriensis, Jania sp.) most frequently. The diets and preferences for algae by the fishes were generally most similar to the assemblage of algae available in early successional (disturbed) habitats during summer when sheet-like and filamentous algae are abundant. The shore crab exhibited the opposite trend with a diet more similar to late successional (undisturbed) habitats.

Influence of depth, season and moult stage on the diet of the velvet swimming crab Necora puber (brachyura, portunidae)

Over 12 months, stomach contents of Necora puber (L.) from three depth zones [littoral; infralittoral (to the limit of brown algal growth); and circalittoral (below the limit of brown algae)] were examined. In each zone, and for both sexes, brown algae were the most dominant food item by volume throughout the year. The principal animal prey items varied between zones. Crustaceans and molluscs were important in the circalittoral and infralittoral zones respectively, whereas the diet of littoral crabs was generally devoid of animal prey. The percentage occurrence of food items varied significantly between depth zones (P

Replacing Fish Meal with Seafood Processing Wastes in Channel Catfish Diets

Abstract Various seafood processing wastes were collected, analyzed, and evaluated for their use as primary protein sources in catfish diets. Finfish wastes (flounder racks and mixed finfish) were higher in crude protein content (60 versus 40%) than blue crab (Callinectes sapidus) wastes. Practical diets containing menhaden (Brevoortia spp.) fish meal or one of four seafood processing wastes (flounder racks, mixed finfish, blue crab, and blue crab without carapace) amounting to 10% of the diet were fed to fingerling channel catfish (Ictalurus punciatus) for 7 weeks under controlled, laboratory conditions. Weight gain and feed efficiency did not differ among treatments. Similar diets containing Atlantic herring (Clupea harengus) or blue crab meal were compared with a standard production diet containing fish meal in a 139-d field cage culture experiment. Caged channel catfish fed the control or Atlantic herring diets had greater daily gain and net production than those fed the crab diet.

On the distribution, diet and possible impact of the invasive European shore crabCarcinus maenas(L.) along the South African coast

The crab Carcinus maenas (L.) has an endemic distribution along the European Atlantic coastline but has been accidentally introduced into intertidal habitats in several parts of the world. Its discovery at the Cape Peninsula in South Africa is recorded here. The crab is well established in Table Bay harbour and the population is at least seven years old. From here it has spread 117 km north and 10 km south. Populations on the open coast are more recently established. The crab feeds on a wide range of intertidal animals, particularly the isopod Paridotea ungulata, limpets and polychaetes, but it is too early to make quantitative assessments of its impact on local intertidal communities. Initial predation experiments suggest that the barnacle Notomegabalanus algicola and the whelks Oxystele variegata and O. tigrina have no refuge in size or zonation from the crab. O. sinensis, of similar size to O. tigrina, is less vulnerable by virtue of its stronger shell. Its critical size (above which it is too large to be attacked) is correlated with crab size. Larger species, such as the mussels Choromytilus meridionalis and Aulacomya ater and the periwinkle Turbo sarmaticus, clearly achieve a refuge in size, but predation on their recruits may influence their abundance and size structure. C. maenas rejected only the urchin Parechinus angulosus as a source of food. While it is conceivable that shifts in community structure, selection for thicker shells in molluscs and localized extinction of certain species may occur at high crab densities, it is predicted that C. maenas will only have a significant impact in areas protected from wave action.

Marine invertebrate glutathione- S-transferases: purification, characterization and induction

High glutathione- S-transferase (GST) activity was found in hepatopancreas and gill cytosol of the blue crab ( Callinectes sapidus) and the digestive gland cytosol of two marine gastropods ( Nassarius obsoletus and Cerithium floridanum). Purification of GST from crab hepatopancreas by Sephadex G-200, DEAE-Sephacel and chromofocusing resulted in the isolation of two isoenzymes with isoelectric points of 5·9 and 5·7 (GST 5·9 and GST 5·7). Antibodies were prepared to these two isoenzymes and the two forms cross-reacted immunologically. The two transferases had similar molecular weights, amino acid compositions, substrate specifities and kinetic parameters. Crab gill cytosol showed one isoenzyme which reacted with antibodies to GST 5·9 and GST 5·7. The major isoenzyme of N. obsoletus was a basic form while C. floridanum showed a homodimer acidic form. The gastropod GST forms did not react with antibodies to crab GST. The presence of the phenolic antioxidant, butylated hydroxytoluene, in the diet of blue crab or shrimp ( Penaeus aztecus) resulted in high hepatic GST activity.

Effect of shellfish consumption on cholesterol absorption in normolipidemic men

Noncholesterol marine sterols, abundant in molluscan shellfish, could inhibit cholesterol absorption. Eight normolipidemic males were fed for 3 weeks each three natural food diets in which a mixture of oysters and clams, crab, or chicken was served as the primary source of animal protein. The diets were equalized for caloric distribution, cholesterol, and n-3 fatty acids, leaving the noncholesterol marine sterols in the oyster/clam diet ( 444 mg 2,000 kcal ) as the potential lipid-modifying variable. Cholesterol absorption was measured by plasma isotope ratio after doses of oral 14C- and intravenously infused 3H-labeled cholesterol. Cholesterol absorption was lower (42 ± 4%) during the oyster/clam diet than during the chicken (54 ± 3%, P < 0.01) or crab (55 ± 3%, P < 0.01) diet periods. There was no difference between the chicken and crab diet periods. Total plasma cholesterol and triglycerides, very low density lipoprotein cholesterol and triglycerides, and low density and high density lipoprotein (HDL) cholesterol were not significantly different between any of the diets. The ratio of the HDL 2-/HDL 3-cholesterol was higher following the oyster/clam diet (0.46 ± 0.09) than the chicken diet (0.32 ± 0.06, P < 0.05). Plasma and red cell membrane n-3 fatty acids were not significantly different among the three diets, but red cell membrane n-3 fatty acids increased as a function of time regardless of dietary sequence.

Octopus joubini (Mollusca: Cephalopoda): a detailed study of growth through the full life cycle in a closed seawater system

Twenty individual pygmy octopuses, Octopus joubini, were reared at 25°C from hatching to maturity on a quantified diet of live crabs in closed (recirculating) natural seawater systems. At 24 week intervals the animals were narcotized, weighed and measured. There was 85% survival to sexual maturity.Growth rates were highest during the first four weeks of exponential growth. Beyond four weeks, growth rates steadily declined and growth became logarithmic in form. Female octopuses grew slightly faster than males and attained a larger size at maturity. The length‐weight relationship showed male Octopus joubini to weigh more than females at a given mantle length. This species displays slight allometric growth resulting in changing body proportions through the life cycle. Relative food intake is highest at hatching and decreases with age. Mean gross growth efficiency over the life span was approximately 40%.

Ecological and behavioral studies of the decorator crab, Microphrys bicornutus Latreille (Decapoda : Brachyura): A test of optimum foraging theory

The food and camouflage selectivity of the decorator crab, Microphrys bicornutus Latreille, was studied in relation to resource availability on a Caribbean fringing reef in the Republic of Panama. We attempted to test the hypothesis that resource availability affects niche breadth. Seasonal aerial exposures of the reef-flat devastated plant-animal assemblages, facilitating foraging comparisons in high and low reef biomass. Resource availability altered niche breadth. As predicted, M. bicornutus consumed a wider variety of species, when resources were scarce, and fewer species, when resources were abundant. Decorating behavior served as a control for resource availability while measurements of potential resources controlled for the choice in sampling periods. The prediction that predators may consume less preferred food items with greater frequency than more preferred food items, if there is a greater abundance of the less preferred food, was confirmed. Also, food preference did not readily change in response to changes in the environment. While highly predictable resources appeared to comprise the bulk of the crab's annual diet, unpredictable resources dominated the crab's diet over shorter periods. This suggests that the predictability of a resource in promoting resource specialization or generalization may not be as important as the number or types of food necessary for the growth and reproduction of the organism. High “within-phenotype components” of niche breadth for feeding and for decorating showed that the population of M. bicornutus has one generalist phenotype. The diet and camouflage compositions consisted mainly of the seaweeds, Acanthophora spicifera (Vahl) Borgesen and Laurencia papillosa (Forsskal) Greville, with animal taxa comprising not > 10% of either assemblages.

Mechanical and behavioral aspects of blue crab, Callinectes sapidus (Rathbun), predation on Chesapeake Bay bivalves

Forces required to crack shells of eight bivalve species were determined and compared to the crushing strength of blue crab ( Callinectes sapidus Rathbun) chelae. Only large (>40 mm) wedge clams, Rangia cuneata (Gray), had shells strong enough to resist the crushing capabilities of large blue crabs as measured in the laboratory. Shell strengths of the other seven bivalve species were within or below the range of maximum forces generated by blue crabs of the sizes tested. Failure loads of four regions of the shell of the soft clam, Mya arenaria L., showed that the umbo region was significantly stronger than any other shell region. In laboratory feeding studies, blue crabs generally showed no size-selective or species-selective feeding behavior. We propose that, with regard to infaunal bivalves, actual crab diet is a function both of prey shell strength relative to predator strength and of prey availability.

Increasing turtle strandings in the southeast United States: A complicating factor

Increased strandings of dead loggerhead sea turtles Caretta caretta on southeast US shores may be the result of increased fishing efficiency and improved recruitment of young turtles to the population. Possibly, the practice of discarding overboard large amounts of unwanted fish and biological material may provide a major energy resource for loggerhead sea turtles and crabs, which are also loggerhead food items. Our observations show that many dead loggerheads stranded on Cumberland Island had eaten man-caught food in addition to the expected diet of crabs and other bottom-dwelling animals. Consideration of alternative methods of handling the incidental fish catch while trawling for shrimp may be useful in reducing the problem of killing of sea turtles in shrimp trawls.

Growth and life‐span of Octopus cyanea (Mollusca: Cephalopoda)*

The growth of Octopus cyanea was followed from 67 to 6500 g in captivity on an ad libitum diet of live crabs. Females spawning in captivity always die after the eggs hatch. Males may mate many times with several different females but do not appear to outlive females. The species spawns throughout the year; the time of spawning is probably determined by the age of the female. Males stop growing after suckers at the edge of the web enlarge and gradually lose weight until their death, about two or three months after maximum sucker enlargement. The life‐span of O. cyanea appears to be between 12 and 15 months from settlement.A growth curve is presented for the species from settling to maximum size and compared with experimental data on captive and marked, free‐living animals. Free octopuses grew at rates similar to captives fed ad libitum, indicating that food was not limiting to growth in the field, and that a reasonable estimate of age could be obtained from the weight at capture.A method of marking animals by branding is described which gives lifetime scars making it possible to study the growth of individual animals released in the field.

The diet of freshwater crabs associated withSimulium neaveiin East Africa

The diet of freshwater crabs associated with<i>Simulium neavei</i>in East Africa