James B. McClintock

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.

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.

An optimization study on the feeding behavior of Luldia clathrata say (Echinodermata: Asteroidea)

The rates of feeding, behavioral responses to changes in prey density, selection for different sizes of prey, and field activity patterns of the starfish Luidia clathrata lend support to the predictions of optimal feeding theory. Rates of location, ingestion, and digestion of prey were high. Individuals offered different densities of prey showed a strong functional response. Individuals presented with different sizes of prey chose the smaller sizes. This selective behavior may be related to ease of manipulation, available stomach area, or maximal food intake per unit time. In the field Luidia clathrata exhibited one peak of activity at dusk, although there was never one hundred percent activity or inactivity at any time. It is not known if this diurnal pattern is caused by patterns in prey or predator, although the former is unlikely as L. clathrata feeds on infauna. The “time buried” during the inactive period in L. clathrata may be related to the period of digestion.

Ingestive conditioning in Luidia clathrata (Say) (Echinodermata: Asteroidea): Effect of nutritional condition on selectivity, teloreception, and rates of ingestion

Luidia clathrata showed no initial preference (as evidenced by contact‐chemoreception and teloreception) between bivalve (Donax variabilis) and shrimp (Penaeus duorarum) foods. Individuals fed 0.5 g wet wt shrimp/day over a 21‐day period showed significant preferences for shrimp over bivalve food. Individuals fed 0.5 g wet wt bivalve/day over a 21‐day period showed no teloreceptive preferences, but significant contact‐chemoreceptive preference for bivalve over shrimp food. Individuals not fed for 21 days showed no preference for either food. Similar ingestive conditioning is exhibited among individuals which were starved for a 3‐month period prior to conditioning. However, nutritional condition may influence selectivity as starved individuals showed a preference for shrimp over bivalve food following the starvation period. Teloreceptive‐response times were significantly lower and ingestion rates significantly higher in starved individuals than in fed individuals. The effects of ingestive conditioning and ...

Avoidance and escape responses of the sub-antarctic limpet Nacella edgari (Powell) (Mollusca: Gastropoda) to the sea star Anasterias perrieri (Smith) (Echinodermata: Asteroidea)

SummaryThe sub-antarctic limpet Nacella edgari (Powell) (Patellidae) has avoidance and escape responses to the sea star Anasterias perrieri (Smith) (Asteriidae) in a kelp forest and in the laboratory. Nacella edgari was preyed upon in the field by A. perrieri, but frequency of capture was low, suggesting the effectiveness of defensive behaviors. Both avoidance and escape responses by the limpet consisted of extension and waving of the pallial tentacles, mushrooming and rotation of the shell and flight. However, escape responses were characterized by greatly intensified rotation of the shell through a horizontal plane. This study extends the evaluation of defensive responses in gastropods to a species which occurs in the southern Indian Ocean.

Photoresponse and associative learning in Luidia clathrata say (Echinodermata: Asteroidea)

The starfish Luidia clathrata Say demonstrated a negative photoresponse and an ability to associate darkness with a food stimulus (the bivalve, Donax variabilis Say). Individuals exposed to continual light and fed at the beginning of a 15 min period of darkness every 24 h for a period of 10, 20, and 30 days, developed an association between darkness and food. This association was characterized by significantly increased levels of emergence of buried individuals during dark periods. Following the 30‐day conditioning period, individuals continued to exhibit this activity response to darkness for 72 h. The ability to learn to associate darkness with food may be related to increased infaunal prey availability at dusk.

Movement patterns of the sub-Antarctic pulmonate limpet Kerguelenella lateralis (Gould) (Mollusca : Gastropoda)

SummaryKerguelenella lateralis produces distinct spots on microalgal-coated rocks in the high intertidal zone at Kerguelen. Spots are the result of microalgal removal, corresponding in outline to the limpets shell. Although limpet spots could be associated with homing behavior, K. lateralis does not exhibit this behavior. Limpets in low-and high-intertidal areas show high levels of sitespecific emigration and immigration. Rates of site-emigration (No. limpets leaving/day) are positively related with limpet density indicating that local limpet densities may influence population movements. Distances of displacement and rates of emigration and immigration are highly variable and do not differ in low-and high-intertidal sites. Lack of homing in K. lateralis may reflect characteristics of its sub-Antarctic environment: low levels of predation, few competitors, and protection from desiccation and wave action through occupation of cracks in the rocky substratum.

Biomass plasticity of the leaves and inflorescences of Acaena magellanica (Lam.) Vahl (Rosaceae) on subantarctic Iles Kerguelen

SummaryThe relative allocation of biomass within monospecific stands of Acaena magellanica that vary in level of wind and water stress differ greatly. Populations in January 1983 varied in leaf biomass from 192 to 2373 g wet wt m-2 (1105 to 10023 kJ m-2) Inflorescences were not produced at either of these extremes of leaf biomass. In two populations with intermediate levels of leaf biomass (597 and 640 g wet wt m-2, 3185 and 2664 kJ m-2), inflorescent biomass was 104 and 273 g wet wt m-2 (385 and 1127 kJ m-2). The relative allocation to sexual reproduction is thus not constant in A. magellanica. The levels of energy in the leaves and inflorescences did not differ greatly despite differences in proximate composition.