John M. Lawrence

Level, content, and caloric equivalents of the lipid, carbohydrate, and protein in the body components of Luidia clathrata (echinodermata: asteroidea: platyasterida) in Tampa bay

Abstract The body components of the primitive platyasterid starfish, Luidia clathrata (Say) have been characterized according to season, reproductive, and nutritional condition. The animal has been ‘reconstructed’ in terms of the wet and dry weights, the weight of organic matter, and the caloric equivalents of the body components in early summer (when there are no gonads and the pyloric caeca are small), in autumn (just prior to initiation of gonadal development and at maximal caeca size), and in early spring (at maximal gonad size). The body wall is always the most significant component in terms of wet and dry weights. In terms of organic matter and calories, the pyloric caeca are the most significant compartment in the fall and, together with the gonads, in the spring. On starvation for one month, the decrease in the size of the pyloric caeca is calculated to have produced 2.048 kcal. The energy requirement over the period, calculated from Q o 2 values, is 2.112 kcal. There was no change in biochemical composition of the pyloric caeca with starvation, suggesting that energy production came about through cell destruction rather than preferential utilization of cellular nutrient stores. Lack of extreme change in the composition of the pyloric caeca with size through the year also suggests that energy deposition in the organ is primarily by change in cell number and not by cell size.

Absorption efficiencies of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea) for selected marine plants

Abstract The absorption efficiencies of the sea urchin Lytechinus variegatus (Lamarck) were calculated by an indicator method. Absorption efficiencies for total organic material, protein, lipid, and carbohydrate were highest with Halimeda incrassata Ellis as food (43 %, 65 %, 71 % and 35 %, respectively), and lowest with Eucheuma isiforme C. Agardh as food (−35%, −42%, −56%and −34%, respectively). Moderately positive absorption efficiencies for total organic material were found with Thalassia testudinum Konig & Sims and Ulva lactuca L. as food, and low positive absorption efficiencies for total organic material are found with Syringodium filiformis Kutzing and Sargassum sp. as food. Absorption efficiencies of the sea urchin Strongylocentrotus purpuratus (Stimpson) (calculated from the literature) were much greater than those of Lytechinus for carbohydrate, but less for protein and lipid. Both sea urchins showed negative efficiencies for some nutrient fractions of their foods. The absorption index (mg nutrient fraction absorbed/g dry wt ingested) showed that Thalassia supplied the most protein and total organic material (43 mg/g dry wt ingested and 142 mg/g dry wt ingested, respectively). In general, the absorption indices indicate that Lytechinus obtains more protein and lipid, but less carbohydrate from its food than does Strongylocentrotus . In the field Lytechinus has primarily a detrital diet.

Seasonal changes in the proximate constituents of the seagrasses Thalassia testudinum, Halodule wrightii. and Syringodium filiforme

Abstract Levels of soluble carbohydrate in the rhizome of Thalassia testudinum Banks ex Konig, Syringodium filiforme Kutzing, and Halodule wrightii (Aschers) Aschers. are highest in the fall and lowest in the spring. This suggests that soluble carbohydrate is a nutrient reserve used to sustain the plants during the period of decreased productivity in the winter. Ash and dry weight levels for three plant-parts (leaf blades, photosynthetically inactive parts of short shoots, and rhizomes) were generally highest in the fall. Protein levels were highest in the summer in all plant parts in T. testudinum and S. filiforme suggesting highest cellular activity. Calorific levels were similar for all three species, the rhizomes having the highest levels, although no seasonal pattern was evident. The organic biomass of an average-sized plant of T. testudinum is 8–12 times greater than that of the other two species in the fall and the short-shoot biomass may account for half of the entire plant. The rhizome of T. testudinum has the highest level of organic matter of the three, for most of the year. The blades of H. wrightii and S. filiforme account for the largest amount of organic material in the fall when compared with the photosynthetically inactive parts of short shoots and rhizomes of the same plant.

Organic level and caloric content of eggs of brooding asteroids and an echinoid (Echinodermata) from Kerguelen (South Indian Ocean)

Summary Egg diameters (mm) of the asteroids Diplasterias meridionalis, Anas ferias perrieri, and Anasterias rupicola and of the echinoid Abatus cordatus were 2.79, 1.75, 1.37 and 1.34, respectively. The levels (% dry wt) of soluble protein/insoluble protein/lipid/carbohydrate were 44: 15: 36: 0.4, 29: 31: 35: 0.9, 37: 28: 26:1.0, and 33:29: 35:2.1, respectively. The calories/egg were 38, 9.45 ± 1.75, 4.69, 3.70 ± 0.98, respectively. Brooded, A. perrieri (1.46 mg dry wt/individual, R = 1.47 mm) had 7.85 ± 1.5 cal/ind. Brooded, A. cordatus (1.76 mg dry wt/ind, length = 2.02 mm) had 4.17 ± 0.06 cal/ind. There was little change in the amount of organic material during development in either species, but the amount of ash increased 5-fold in A. perrieri and 13-fold in A. cordatus. The significance of the large eggs may be in the production of a large juvenile, and not in the provision of a large amount of energy for development.

Annual Cycle in the Size of the Gut of the Purple Sea Urchin, Strongylocentrotus purpuratus (Stimpson)

SEVERAL species of sea urchins undergo an annual reproductive cycle with a seasonal enlargement and shrinkage of the gonads1. In connexion with investigations on the annual reproductive cycle of the purple sea urchin, Strongylocentrotus purpuratus, it was found that the gut of the urchin also undergoes a seasonal cycle in size.

Role of the Gut as a Nutrient-Storage Organ in the Purple Sea Urchin (Strongylocentrotus purpuratus)

S EA urchins may receive only sporadic food in some habitats, for example, when imprisoned in holes they have bored into soft rock (Otter, 1932). Seasonal variations in amount and quality of food available are also possible. In addition, there may be seasonal feeding rhythms as suggested by Moore (1937) for Echinus esculentus. Even in the presence of abundant food, Fuji (1962) demonstrated seasorpl feeding rhythms for Strongylocentrotus intermedius. It is therefore important that nutrients be stored for use during periods when food is not being ingested. Nutrients might be stored in any one of the components of the sea-urchin body, for example, the gonad, the gut, or body wall. The gonad has been considered the major site of nutrient storage in the sea urchin Echinus esculentus (Moore,

Characteristics of foraging in the soft-bottom benthic starfish Luidia clathrata (echinodermata: Asteroidea): prey selectivity, switching behavior, functional responses and movement patterns

SummaryLuidia clathrata show a strong preference for the infaunal bivalve Mulinia lateralis in Tampa Bay, Florida. Quantitative and qualitative changes in diet occurred over a 7-month period. Individuals may shift from intraoral macrofaunal feeding to intra- and extraoral detrital feeding during periods of low macrofaunal availability. In the laboratory L. clathrata showed switching behavior, feeding disproportionately on the most abundant of two simulataneously presented food models. This switching mechanism may be related to either contact-chemoreceptive rejection of lowdensity food or enhanced distance-chemoreception of high density food. The use of standardized food models eliminated the possibility that handling time was important in switching behavior. Both fed and starved individuals showed functional responses to changes in prey density. However starved individuals ingested greater numbers of prey and spent more time foraging than did fed individuals. Switching and functional response behaviors may be important in promoting nutritional uptake and in causing density-dependent mortality of prey populations. Movement patterns of L. clathrata are directional in the absence of bivalve prey, but become non-directional once patches of prey are encountered. This allows individuals to remain in areas of high prey density. Luidia clathrata has characteristics of an optimal forager, where energy is maximized per unit feeding time.

Effects of blade removal on the proximate composition of the rhizome of the seagrass Thalassia testudinum banks ex könig

Abstract Chemical analyses (ash, protein, lipid, soluble and insoluble carbohydrate) indicated that the rhizome of Thalassia testudinum Banks ex Konig functions as a storage organ in supporting blade regeneration after defoliation in the field and laboratory, and in seasonal growth. Soluble carbohydrate is the primary reserve mobilized in the rhizome after defoliation and shows the largest decrease in level and amount during the non-growing season. Protein showed no change in the rhizome of clipped or unclipped plants. The short shoot also contributes to blade regrowth as indicated by depletion of protein and soluble carbohydrate after defoliation. The lipid content was low in all organs with no seasonal pattern or effect of defoliation. Protein levels were high in regenerated blades of clipped plants while ash levels were low. Caloric levels were lower in short shoots and rhizomes and in the regenerated blades of clipped plants due to lower levels of organic constituents.

The effect of temperature-salinity combinations on the functional well-being of adult Lytechinus variegatus (Lamarck) (Echlnodermata, Echinoldea)

The activity coefficient (1000/righting time in sec) was measured to indicate the functional state of Lytechinus variegatus (Lamarck) after exposure to combinations of temperature (22°, 28°, and 34°C) and salinity (25, 30, 35, and 40 ‰). Environmental levels of these variables were 30–33°C and 34–35 ‰. The results indicate that the species lives closer to the upper than lower lethal limits of temperature and salinity. The maximal activity coefficient (18 ± 8) was at 28°C and 35 ‰. A reduction in salinity was probably responsible for a recent mass mortality of the echinoid reported in the eastern Gulf of Mexico.

Utilization of marine plants and their constituents by bacteria isolated from the gut of echinoids echinodermata

Utilization of marine plants and their constituents by bacteria isolated from the guts of echinoids was investigated to determine the potential role bacteria may have in carbohydrate digestion in echinoids. Bacteria from the guts of the regular echinoids Lytechinus variegatus (Lamarck) and Arbacia punctulata (Lamarck) could physically degrade the marine plants Ulva lactuca and Eucheuma nudum, but not Caulerpa prolifera. Diplanthera wrightii and Thalassia testudinum were only slightly degraded by the gut bacteria. Bacteria from the guts of the irregular echinoids Mellita quinquiesperforata (Leske) and Encope aberrans (Martens) could not physically degrade any of these marine plants. Mixed and some isolated bacteria from the gut of L. variegatus could utilize xylose, rhamnose, glucose, galactose, laminarin, carageenan, starch and agar, but not cellulose or chitin. The results with isolates suggest that the bacteria of the echinoid gut are fairly non-selective. The bacteria of the guts of the two regular echinoids could utilize certain marine plants that the echinoids eat and certain of the plant constituents. The bacteria could not utilize plant fibers.