Distribution,substratum preference and burrowing behaviour of Lovenia elongata (Gray) (Echinoidea: Spatangoida) in the Gulf of Elat ('Aqaba), Red Sea

Lovenia elongata (Gray), the Indo-West Pacific spatangoid, was studied in the Gulf of Elat ('Aqaba) at the northern end of the Red Sea. The occurrence and local distribution of this macrobenthic burrowing species was determined and related to the particle size distribution of the substrata in which it was found. Its habitat preference is for clean, grassless, sandy bottoms in intertidal areas (beaches and sandbars), and on sublittoral level bottoms of protected bays and lagoons sheltered from heavy wave action. The preferred sediments were found to range from medium to fine sand. The population density, size frequency distribution, growth, reproduction, recruitment, and mortality of a sublittoral population of L. elongata (at Wadi Taba, Sinai) were studied.The mode of life of this burrowing heart urchin was observed in situ and in aquaria. Its burrowing and emergence behaviour are described. Experiments were carried out on the effect of particle size on burrowing behaviour. There are significant differences in the ability of L. elongata to manipulate substrata of varying grain size. The burrowing process was found to be most rapid in natural sand of medium-fine composition, corresponding to the normal sediment of the urchin's habitat. Such sediments were also found to be suitable for successful larval settlement; juveniles did not survive in coarser sand.Differences in population density and spatial distribution between various size groups are attributed to differences in their ability to manipulate the substratum. L. elongata is found to be morphologically suited to sand, particularly medium-fine sand; however, it is restricted by its morphology to shallow burrowing, since it lacks specialized mechanisms for deeper burrowing and funnel building.     

Burrowing,feeding, and spatial distribution of the school prawn Metapenaeus macleayi (Haswell) in the Hunter river region,Australia

The influence of the food content and the particle size of the substratum on the distribution and relative abundance of Metapenaeus macleayi (Haswell) has been investigated by periodic trawl sampling for prawns and laboratory studies of their food, feeding, and burrowing behaviour.M. macleayi are opportunistic omnivores; they pick up material from the bottom with their chelipeds and convey it to the mouthparts where edible matter is sorted and ingested. They burrow into the sediment with their pereopods and pleopods, and are usually totally buried beneath the surface. A respiratory water current enters a tube formed by the antennal scales and the antennules, flows over the gills and then out of the carapace; this current is regularly reversed with increased strength, presumably to carry away de-oxygenated water. The results of experiments on substratum preference with adequately nourished juveniles suggest that the particle size of the sediment is more important than the food in the substratum in determining the distribution; the apparent preference of juveniles for a fine sandy substratum both in the laboratory and in the natural habitat may be attributed to the minimum threshold velocity of the sand particles.Adults are most abundant in turbid coastal waters arising from estuarine discharge and here the size of the sediment particles appears to be less important than the food content of the substratum in determining the distribution. The mangrove and reed swamps in the Hunter region play an important rôle in the food requirements of juvenile and adult prawns.     

A Bioassay to Estimate Root Penetration by Nematodes

An in vitro bioassay with a 96-well microtiter plate was used to study the effect of lectins on burrowing nematode penetration of citrus roots. In each well, one 4-mm root segment, excised from the zone of elongation of rough lemon roots, was buried in 0.88 g dry sand. Addition of a Radopholus citrophilus suspension containing ca. 300 nematodes in 50 μ1 test solution completely moistened the sand in each well. The technique assured uniform treatment concentration throughout the medium. Within 16-24 hours, burrowing nematodes penetrated citrus root pieces, primarily through the cut ends. The lectins (100 μg/ml) Concanavalin A (Con A), soybean agglutinin (SBA), wheat germ agglutinin (WGA), and Lotus tetragonolobus agglutinin (LOT) stimulated an increase in penetration of citrus root segments by Radopholus citrophilus. Concentrations as low as 12.5 μg/ml Con A, LOT, and WGA stimulated burrowing nematode penetration of citrus roots. Heat denaturation of the lectins reversed their effect on penetration; however, incubation of nematodes in lectin (25 μg/ml) with 25 mM competitive sugars did not. The reason for enhanced penetration associated with lectins is unclear.     

Locomotory rhythms and burrowing habits of Penaeus semisulcatus (de Haan) and P. Monodon (Fabricius) (Crustacea: Penaeidae)

The locomotor activity of adult Penaeus semisulcatus (de Haan) and P. monodon (Fabricius) has been studied. The former was reared entirely, and the latter partly under artificial conditions. Both species display circadian activity rhythms in response to light entrainment. Light appears to be a major synchronizer, although the results indicate that feeding also has a certain synchronizing effect in starved prawns.The expression of endogenous activity rhythms in both species is affected by their substratum requirements and burrowing habits. Choice experiments show that both P. semisulcatus and P. monodon select a fine grade sand for burrowing, although the burrowing frequency of the latter species is always low. In a non-choice situation, P. semisulcatus will readily enter a coarse substratum whereas P. monodon will very seldom do so.The effects of various light regimes on the activity patterns of P. semisulcatus and P. monodon were examined and the results show that for both species an imposed long photoperiod regime (18:6 LD) induced 6-h periods of brief but intense activity, alternating with 18-h periods of almost complete inactivity. This activity pattern is discussed in relation to feeding and energy expenditure.     

Habitat preferences of two estuarine burrowing crabs Helice crassa Dana (Grapsidae) and Macrophthalmus hirtipes (Jacquinot) (Ocypodidae)

The horizontal and vertical distributions of two species of endemic, burrowing mud crabs Helice crassa Dana 1851 (Grapsidae) and Macrophthalmus hirtipes (Jacquinot 1853) (Ocypodidae) are described for the Avon-Heathcote Estuary (43°33′S: 172°44′E), Christchurch, New Zealand. Substratum preference is shown to be the most important factor influencing mud crab distribution, but lack of tolerance to salinities below 4‰ is also a significant factor preventing M. hirtipes from occurring at points close to freshwater input. Both species had similar sediment organic content and particle size requirements. Helice crassa was concentrated in well-drained, compacted sediments above mid-tide level, whilst Macrophthalmus hirtipeswas found in waterlogged areas below mid-tide level. This vertical separation is shown not to be caused by differential desiccation tolerances, but by feeding and burrowing adaptations related to these different substrata.     

Responses of <Emphasis Type="Italic">Venerupis philippinarum</Emphasis> (Mollusca: Bivalvia) to Predators and Changes in Hydrodynamics

The rate of burrowing into sand by the bivalve mollusk Venerupis philippinarum was studied under laboratory conditions. It is found that an increase in the intensity of water flow to an average of 1000 ml/min stimulates the burrowing of the mollusk, while higher values suppress burrowing; the threshold values are somewhat different for the young and adult specimens. It is shown that the presence of the starfish Asterias amurensis in the experimental environment decreases the rate of burrowing of V. philippinarum by 10–20% depending upon the sizes of the predator and the potential victim, but the depth of penetration of the mollusks into the sediment increases. It is supposed that in V. philippinarum and other species of bivalve mollusks related to the same life form and characterized by a moderate capability to burrow into the ground, the adaptive strategy of threat avoiding (great wave activity, an approach of a predator) is expressed as burrowing into a depth uncommon for usual situations and waiting. This behavior, to a significant degree, provides the capability of some species to inhabit shallow water areas with poor hydrodynamics inhabited by numerous predators.     

Behaviour of <Emphasis Type="Italic">Odontomachus chelifer</Emphasis> (Latreille) (Formicidae: Ponerinae) Feeding on Sugary Liquids

Sugary solution intake behavior by Odontomachus chelifer (Latreille), is studied. The feeding mechanism involved is described. Effects of sucrose concentration and solution viscosity on ingested load, feeding time and rate of liquid intake are assessed. Suction was always the feeding mechanism, regardless of concentration or viscosity of the solution. There were no differences in loads ingested for concentrations of up to 30% w/w, but feeding took longer at this concentration. Liquid intake rates were higher at the lowest concentrations. Above 40% w/w, values of all three variables were smaller. O. chelifer’s ability to ingest mildly viscous fluids could be related to its capacity to ingest other viscous fluids present in its diet.     

Phagotrophic Mechanisms and Prey Selection in Free-living Dinoflagellates1

Three types of feeding mechanisms are known in dinoflagellates: pallium feeding, tube feeding, and direct engulfment. Pallium feeding has only been described for heterotrophic thecate species (Protoperidinium, Diplopsalis group). Tube feeding is commonly found among both naked and thecate species of mixotrophic and heterotrophic dinoflagellates (e.g. Amphidinium, Dinophysis, Gyrodinium, Peridiniopsis). Direct engulfment is mainly found among naked species (e.g. Gymnodinium, Gyrodinium, Noctiluca): recently, however, some thecate species have been shown to use this feeding mechanism as well. Feeding behavior in dinoflagellates involves several steps prior to actual ingestion, including precapture, capture, and prey manipulation. As feeding mechanisms allow the ingestion of relatively large prey or parts thereof, dinoflagellates are regarded as raptorial feeders. While prey size plays an important role in the ability of dinoflagellates to ingest food, this alone cannot explain observed prey preferences. Some dinoflagellate species can be very selective in their choice of prey, while others show a remarkable versatility.     

Direct uptake of detrital carbon by the deposit-feeding polychaete Euzonus mucronata (Treadwell)

Bacteria and other microbes colonizing detrital particles are assimilated efficiently by detritivores; in some cases the non-living detrital matter is relatively refractory. This comparison has led to the hypothesis that the bacterial component of detritus, rather than the non-living material, is the principal food resource of detritivores. This hypothesis was tested by feeding radiolabelled detritus to the deposit-feeding polychaete Euzonus mucronata (Treadwell), an abundant inhabitant of Pacific coastal sand beaches. The assimilation of carbon from sterile detritus at a concentration of 0.3 mg ash-free dry weight of detritus per g dry sand (0.03 % organic content) was sufficient to provide about one-half of the carbon requirements of E. mucronata. There was no significant difference in assimilation from chemically-extracted or water-extracted sterile detritus (representing relatively refractory and available material, respectively), or from the same materials after microbial colonization. Thus, the major source of carbon may have been the supposedly refractory component of the detritus. Despite a low estimated assimilation efficiency (0.76–1.72%), the carbon requirements of E. mucronata would be met entirely by direct assimilation of detrital carbon if only 10% of the total organic carbon in the sand is as available as the chemically-extracted detritus in this experiment. Low assimilation efficiency does not preclude the acquisition of nutritionally important quantities of carbon by direct assimilation from detritus.     

Red porgy (Pagrus pagrus) larval feeding performance and behavior at the onset of exogenous feeding

The feeding performance and behavior at the onset of exogenous feeding, 3 to 4 days after hatching (DAH), were studied in red porgy Pagrus pagrus larvae. Similar feeding efficiency and intensity were achieved for two feeding treatments (live or freeze-dried rotifers) suggesting that prey movement is not decisive for their detection and capture and demonstrating that at first feeding red porgy larvae can ingest inert food. Larvae feeding performance was not affected by a diet shift between treatments. Based on maximum rotifers consumption and gut evacuation time at 18 °C, the daily ration was estimated as 14.035 μg, considering 14 h of feeding and a 25% egg:female rotifer ratio. Larval swimming activity measured by video recording showed a close association with gut fullness and similar swimming patterns for 3 and 4 DAH larvae. However, 20.3% larger mouth gape and 54.6% higher swimming speed of the older larvae should provide a better feeding performance and more energy needed for growth.     

Larval feeding structure plasticity during pre-feeding stages of echinoids: Not all species respond to the same cues

Much of the work on phenotypic plasticity has focused on inducible defenses. As a result, little is known about induced phenotypes that improve the acquisition of resources (i.e. inducible offenses). Feeding larvae of several marine invertebrate species, gastropods and echinoderms, have inducible offenses, and produce larger feeding structures when given less food. To better understand inducible offenses, I investigated when in development sea urchin and sand dollar larvae can first alter their feeding morphology in response to different concentrations of food. Food induced feeding structure changes in both sea urchin and sand dollar larvae before larvae were able to ingest food. This suggests that the nervous system and a regulator gene, orthopedia, play a mechanistic role. In addition, larvae of the two species, Strongylocentrotus purpuratus and Dendraster excentricus, responded to different cues. Pre-feeding larvae of both species developed relatively shorter arms when given algal cells (i.e. chemical and physical stimuli), whereas only pre-feeding larvae of D. excentricus developed shorter arms when exposed to algal exudates (i.e. chemical stimuli). Larvae of neither species responded morphologically to the presence of polystyrene beads (i.e. physical stimuli).     

Water relations of the burrowing sandhill frog, Arenophryne rotunda (Myobatrachidae)

Arenophryne rotunda is a small (2–8 g) terrestrial frog that inhabits the coastal sand dunes of central Western Australia. While sand burrowing is a strategy employed by many frog species inhabiting Australia’s semi-arid and arid zones, A. rotunda is unique among burrowing species because it lives independently of free water and can be found nocturnally active on the dune surface for relatively extended periods. Consequently, we examined the physiological factors that enable this unique frog to maintain water balance. A. rotunda was not found to have any special adaptation to reduce EWL (being equivalent to a free water surface) or rehydrate from water (having the lowest rehydration rate measured for 15 Western Australian frog species), but it was able to maintain water balance in sand of very low moisture (1–2%). Frogs excavated in the field were in dune sand of 4.4% moisture content, as a consequence of recent rain, which was more than adequate for these frogs to maintain water balance as reflected by their low plasma and urine osmotic concentrations. We suggest that in dry periods of the year, A. rotunda can achieve positive water balance by cutaneous water uptake by burrowing deeper into the substrate to where the percent water content is greater than 1.5%.     

Organization of protein digestion in adult Calosoma calidum (Coleoptera: Carabidae)

Organization of protein digestion was examined in adult male Calosoma calidum (Carabidae) fed either ground-beef or waxmoth larvae (Galleria mellonella). Although trypsin activities in the foregut are consistently higher than those in the midgut, the luminal contents of each region are in equilibrium. Movement of fluids between the midgut and foregut is brought about by muscular contractions of the proventriculus. A 42% fall in trypsin activity of the foregut after feeding on ground-beef is due largely to disgorged enzymes being left on the food. A far higher proportion of disgorged trypsin is recovered when C. calidum feed on waxmoth larvae; beetles ingest about 74% prey protein and yet avoid ingesting digestively refractory solids. The retention of undigested macromolecules in the midgut and foregut lumen was determined using [¹⁴C]inulin labelled waxmoth larvae. Nine per cent and 25% of the radiolabel was passed in the faeces in 2 and 4 days respectively, whilst 59 and 91% of the weight gained at feeding was lost in the same intervals. The role that the peritrophic membrane and pyloric valve play in this process, as well as its implications for enzyme conservation, is discussed.     

Behavior of Four Species of Fiddler Crabs,Genus Uca,in Southeast Sulawesi,Indonesia

We studied the behaviors of four species of sympatric fiddler crabs on Kaledupa Island, Indonesia. Species differences in activity level, grooming, burrowing and feeding were related to their habitat and food. Uca chlorophthalmus, living in muddy mangrove areas, were inactive and spent most of the time feeding in place. Females fed 50% faster than males and spent more time feeding. U. vocans was the dominant species at the beach in silty sand and was very active. Its feeding rate was about twice that of the former species, females fed more rapidly than males, and many crabs of both sexes fed in droves at the water’s edge during ebb tides. During ebb tides, they spent most of their time feeding, while at flood tide they engaged in a greater variety of activities, including burrow maintenance. They frequently walked while feeding and interacted aggressively. U. tetragonon lived in a pebbly band along one edge of the beach, by a quay. Their feeding rate was comparable in both sexes and slower than that of U. vocans; they fed largely on filamentous algae growing on the quay, which provides better food, and fed faster during flood tide than ebb tide. They spent more time in waving and other sex-related activities, and were seldom aggressive, except during the week of the full moon. Burrowing activities included placing excavated mud balls some distance away from their burrows and re-arranging them. U. dussumieri inhabited the other end of the beach in muddier substrate. They did not have sex differences in feeding rates and their rate of scooping food into their mouths was slow, but feeding claws made multiple pinches of the substrate, thus accumulating more material in each clawful of food.     

In Vitro Sensitivity of Torulopsis glabrata to Amphotericin B, 5-Fluorocytosine, and Clotrimazole (Bay 5097)

Thirty-five strains of Torulopsis glabrata were tested by a tube dilution method for their susceptibility to amphotericin B, 5-fluorocytosine, and clotrimazole (Bay 5097). Amphotericin B was the most active in vitro, inhibiting all strains at a concentration of 1 μg/ml and killing all strains at 2 μg/ml. 5-Fluorocytosine inhibited over 80% of strains at 0.24 μg/ml, but three strains required ≥7.8 μg/ml for killing. A concentration of 2 μg of clotrimazole per ml inhibited less than 50% of strains, and 8 μg/ml killed only 10% of strains. Most strains of T. glabrata were killed by therapeutically achievable concentrations of amphotericin B and 5-fluorocytosine, but not clotrimazole.     

Evolution of feeding structure plasticity in marine invertebrate larvae: a possible trade-off between arm length and stomach size

The ability of an organism to alter its morphology in response to environmental conditions (phenotypic plasticity) occurs in several species of marine invertebrates. Examples are sea urchin and sand dollar larvae (plutei). When food is scarce, plutei produce longer food-gathering structures (larval arms and a ciliary band) and smaller stomachs than when food is abundant. However, it is unclear whether stomach size is actually induced through changes in morphogenesis or simply by food distending the stomach. Distinguishing between these two hypotheses is possible because plutei morphologically respond to food concentrations and change the length of their food-gathering structures before they are capable of feeding. More importantly, these two hypotheses provide insights to whether a trade-off exists between the response in food-gathering structures and the response in stomach size—a possible explanation for the evolution of feeding-structure plasticity in marine invertebrate larvae. In this study, I investigated whether sea urchin larvae (Strongylocentrotus purpuratus and S. franciscanus) reared in different amounts of food produced stomachs of different sizes before they were capable of feeding. Prior to having the ability to ingest food, larvae produced larger stomachs and shorter arms when food was abundant than when food was scarce, consistent with the hypothesis that food induced changes in morphogenesis. In addition, there was a strong negative correlation between the magnitude of plasticity in larval arm length and the magnitude of plasticity in stomach size. These results are consistent with the idea that a trade-off exists between the response in arm length and the response in stomach size, and at least in part, explains the evolution of feeding structure plasticity in plutei. This may also explain why feeding-structure plasticity has evolved in larvae of other taxa (e.g. other echinoderms and gastropods).     

Experimental studies on the foraging behavior of the sand fiddler crab Uca pugilator (Bosc, 1802)

The purpose of this study was to test the hypothesis that foraging sand fiddler crabs. Uca pugilator (Bosc), move through the habitat in response to low substratum food levels even though these movements may take the crabs considerable distances from the safety of the burrow area. Chl a and ATP concentrations were used as measures of food density in foraged and unforaged substratum. Field and laboratory feeding experiments showed that crab foraging intensity in a habitat patch was directly correlated with food density in the patch either in the presence or absence of alternative food patches. Other experiments showed that sand fiddlers can respond to differences in food level on a scale of millimeters and do this by probing the substratum with minor chelae. Food levels in aggregations of non-ingested particles harvested by sand fiddlers, feeding pellets, correspond to low foraging intensities predicted from foraging experiments and crabs exhibit low foraging intensities on substratum patches derived from feeding pellets. Substratum food levels in two distinct areas corresponded to high predicted foraging intensities and there was no consistent trend in the level of food in the burrow vs. the nonburrow microhabitats. These results suggest that the movements of foraging sand fiddlers are to some extent controlled by the reduction in substratum food levels due to feeding during a single foraging episode. Sand fiddlers can extract over 70% of the food from harvested substratum over a broad range of substratum food densities but harvest only 42% of the available substratum.     

Observations on the clypeasteroid Echinocyamus pusillus (O. F. Müller)

The tiny echinoid Echinocyamus pusillus (O. F. Müller) is equipped with specialized external structures that suit it for a wide variety of environments. Special features include the ability to burrow in sediments of fine sand to shell gravel and to climb vertically.Specimens dredged off the west coast of Scotland were observed in aquaria and with the SEM. E. pusillus is characterized by three kinds of spines, and by two of pedicellariae. In contrast to sand dollars, the spines play a passive rôle in the feeding and burrowing operation, probably retaining a defensive nature as in the regular urchins. It is the podia that are chiefly involved in climbing, burrowing, righting, and probably feeding. Surface ciliary currents transport particles, but not to the mouth; they may have a respiratory or cleansing function. Experimental animals did not burrow in either very fine or very coarse sand, probably because a certain relationship exists between particle weight and podia size.E. pusillus shares behavioural and structural characteristics with regular and irregular urchins. It is not a true sand dollar, but may illustrate an evolutionary stage towards such a form.     

Feeding behaviour of the Japanese loach,Misgurnus anguillicaudatus (Cobitididae)

The feeding behaviour of a Japanese loach,Misgurnus anguillicaudatus was experimentally analyzed. From observations the behaviour patterns were described. The adult fish responded to a piece of thread soaked with filteredTubifex homogenate (Tubifex solution) and showed feeding behaviour. But they ignored an unsoaked piece of thread. LivingTubifex kept in a glass cell failed to elicit feeding behaviour in the fish. A gauze-covered vessel withTubifex solution buried in the sand substrate released feeding behaviour in fish in its vicinity. It follows that the feeding behaviour of this fish is induced by some chemical stimuli. WhenTubifex solution was introduced at the central area of the plastic vessel with a fish, the fish suddenly started the Feeding-crawl and showed Gulp which was composed of Dig and Twist. Using sand particles, it was shown that intake of materials into the digestive tract occurs only at the moment of Twist and not any other time. The standard feeding patterns ofMisgurnus anguillicaudatus are thus quick inhalation of organic matter together with substrate, occurring at the moment of Twist, which is released at the place where the fish received the appropriate chemical stimuli.Misgurnus anguillicaudatus is regarded as a typical “detritus feeder”.     

Feeding of grey gurnard Eutrigla gurnardus (Triglidae) in the area of the Rockall Seamount

Specific features of feeding of grey gurnard Eutrigla gurnardus depending on vertical distribution and habitat conditions in the area of the Rockall Seamount in 2000 were considered. The intensity of feeding of grey gurnard from April to September decreased by several times. The main food of this species in spring are euphausiids and that in autumn are fish. Males feed slightly more intensively than females. The intensity of feeding, distribution, and behavior of grey gurnard in different seasons and at different depths near bottom and in the pelagial noticeably differ and depend on the composition of distribution and numbers of dominant food items (euphausiids, sand eel Ammodytes marinus, fish juveniles).