Within-group spatial position and vigilance: a role also for competition? The case of impalas (<Emphasis Type="Italic">Aepyceros melampus</Emphasis>) with a controlled food supply

Theory predicts that individuals at the periphery of a group should be at higher risk than their more central conspecifics since they would be the first to be encountered by an approaching terrestrial predator. As a result, it is expected that peripheral individuals display higher vigilance levels. However, the role of conspecifics in this “edge effect” may have been previously overlooked, and taking into account the possible role of within-group competition is needed. Vigilance behavior in relation to within-group spatial position was studied in impalas (Aepyceros melampus) feeding on standardized patches. We also controlled for food distribution in order to accurately define a “central” as opposed to a “peripheral” position. Our data clearly supported an edge effect, with peripheral individuals spending more time vigilant than their central conspecifics. Data on social interactions suggest that it was easier for a foraging individual to defend its feeding patch with its head lowered, and that more interactions occurred at the center of the group. Together, these results indicate that central foragers may reduce their vigilance rates in response to increased competition. Disentangling how the effects of competition and predation risk contribute to the edge effect requires further investigations.     

The role of ecological context and predation risk-stimuli in revealing the true picture about the genetic basis of boldness evolution in fish

To showcase the importance of genotype × environment interactions and the presence of predation risk in the experimental assessment of boldness in fish, we investigated boldness in terms of feeding behavior and refuge use in two genetically different populations of juvenile carp (Cyprinus carpio) in two replicated experimental conditions in ponds and laboratory tanks. The populations were expected to exhibit genetic differences in boldness due to differential evolutionary adaptation to low-predation-risk pond aquaculture conditions. Boldness was measured in variants of open-field trials with and without implementation of additional predation risk-stimuli by angling on feeding spots. Without explicit implementation of risk, genotypes adapted to low-risk environments, i.e., domesticated mirror carp behaved consistently bolder than their less domesticated scaled conspecifics in the pond environment, but not in the laboratory environment. When we implemented artificial risk-stimuli by angling on previously safe feeding spots, boldness differences among genotypes also emerged in the laboratory environment, indicating strong genotype × environment effects on boldness behavior of carp. The expected genetic basis of boldness differences among genotypes was clearly supported in the pond environment, while the laboratory study revealed these patterns only under inclusion of explicit risk-stimuli. Our study thus underscores that boldness may involve both a basal component that is expressed independently of obvious predation risk (e.g., in open fields) and a component revealed in relation to explicit predation risk, and both dimensions may respond differently in behavioral tests.     

Feeding habits and phenotypic changes in proboscis length in the southern oyster drill, Stramonita haemastoma (Gastropoda: Muricidae), on Florida sabellariid worm reefs

The southern oyster drill, Stramonita (= Thais, Kool 1987) haemastoma, is a common intertidal and subtidal predator in the southeastern United States. It uses specialized feeding structures and foraging strategies to bore holes through the shell of its bivalve prey. However, on the east coast of Florida, S. haemastoma, is common on sabellariid worm reefs constructed by the polychaete Phragmatopoma lapidosa (Walton Rocks Beach, Florida, 27°17′N, 80°12′W), a habitat where the snail’s typical prey are scarce. From 1999 to 2001, we examined the feeding habits of S. haemastoma on sabellariid reefs and the behavioral and morphological responses of S. haemastoma that accompanied switching from a diet of bivalves to sabellariids. On worm reefs S. haemastoma feeds on P. lapidosa by inserting the proboscis deep into a worm’s tube. Worm-feeding snails had longer proboscises (~3.7 times shell height) than bivalve-feeding conspecifics (~2.0 times shell height). Snails raised on different diets showed significant differences in proboscis length suggesting that the proboscis length is phenotypically plastic. Whereas typical oyster drills must bore holes for days before ingesting prey, S. haemastoma on worm reefs avoids boring and attacks and consumes worms in 15–50 min. In the laboratory, oyster drills consumed 1.7 worms per day, spending <1 h each day feeding. On sabellariid reefs, differences in feeding, handling costs, and prey value, are likely to have a significant effect on the ecology and life history of S. haemastoma in this habitat.     

Impacts associated with the recent range shift of the aeolid nudibranch <Emphasis Type="Italic">Phidiana hiltoni</Emphasis> (Mollusca,Opisthobranchia) in California

In 1977, Phidiana hiltoni (O’Donoghue in J. Entomol Zool (Pomona College, Claremont, California) 19:77–119, 1927) began spreading northward from Monterey, California. By 1992, it had reached Duxbury Reef (37° 53′ 23″ N, 122° 41′ 59″ W), 100 km to the north, where other nudibranchs subsequently appeared to decline. The role of P. hiltoni in this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance data. In the wild, P. hiltoni preyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory, P. hiltoni attacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance of nudibranchs vulnerable to attack by P. hiltoni declined an average of two-thirds at Duxbury Reef since its arrival, compared to (1) no change in the non-vulnerable species and (2) no change in either group at two other sites where P. hiltoni was one to two orders of magnitude less abundant. Phidiana hiltoni therefore appears to have caused this decline, likely through a combination of direct predation and competition for prey. A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment of P. hiltoni at Duxbury Reef, as well as hindering further northward spread.     

Alarm signal response in the brittle star Amphiura filiformis

 Flat fishes, such as the dab Limanda limanda, commonly prey on arms of Amphiura filiformis. We demonstrate in flume experiments that A. filiformis showed a more or less simultaneous response to an up-stream predation by dab on conspecifics: the arms, which are stretched up into the water column when filter feeding, responded by bending down to the sediment surface, and some arms submerged, at least partly, into the sediment. We interpret this as an alarm response. A similar, but significantly weaker response in A. filiformis was also recorded when dab ate Amphiura chiajei. Homogenates of the two Amphiura species and arm pinching – to simulate partial predation – elicited a similar response in A. filiformis, the arms bent to the sediment surface. In contrast, however, the behavioural response of the arms to the homogenates was to protrude further out of the sediment and sweep the surface vigorously. We interpret this as a feeding behaviour. Response to arm pinching was less clear. The ecological consequences and origin of alarm signal response in A. filiformis are discussed. Received: 8 February 1999 / Accepted: 16 July 1999     

Social monogamy in the shrimp Pontonia margarita, a symbiont of Pinctada mazatlanica, off the Pacific coast of Panama

A previous study predicted the evolution of monogamy in symbiotic crustaceans inhabiting scarce, relatively small hosts in tropical environments where predation risk away from hosts is high. This prediction was tested in the shrimp Pontonia margarita, which inhabits the pearl oyster Pinctada mazatlanica. A total of 68 oysters were collected from the intertidal and shallow subtidal at two islands (Islas Secas [N 27° 55′, W 82° 03′] and Isla de La Coiba [N 27° 50′, W 97° 03′]) off the eastern tropical Pacific coast on 15 and 17 March 2007, respectively. The population structure, distribution, male-female association pattern, and relative growth of the major claw and pleura of the second abdominal segment of each shrimp retrieved were examined. Shrimps were found as heterosexual pairs in the mantle cavity of hosts more frequently than would be expected by chance alone. Males occurred with females in the same host, independent of the reproductive condition of the female or the stage of development of brooded embryos. This observation, and strong correlations between the host and shrimp body size in both males and females suggest a long-term association between males and females in each host. Sexual dimorphism in body size was minor, with males being just slightly smaller than females. In agreement with predictions for monogamous species, the major claw of males did not display positive allometry, which has been generally reported for polygamous shrimps. In turn, the pleura of the second abdomen presented negative allometry in males but positive allometry in females. All available information suggests that Pontonia margarita has a socially monogamous mating system with males and females forming exclusive pairs in their hosts.     

Influences of divergent behavioral strategies upon risk allocation in juvenile flatfishes

Animals balance feeding and anti-predator behaviors at various temporal scales. When risk is infrequent or brief, prey can postpone feeding in the short term and temporally allocate feeding behavior to less risky periods. If risk is frequent or lengthy, however, prey must eventually resume feeding to avoid fitness consequences. Species may exhibit different behavioral strategies, depending on the fitness tradeoffs that exist in their environment or across their life histories. North Pacific flatfishes that share juvenile rearing habitat exhibit a variety of responses to predation risk, but their response to risk frequency has not been examined. We observed the feeding and anti-predator behaviors of young-of-the-year English sole (Parophrys vetulus), northern rock sole (Lepidopsetta polyxystra), and Pacific halibut (Hippoglossus stenolepis)—three species that exhibit divergent anti-predator strategies—following exposure to three levels of predation risk: no risk, infrequent (two exposures/day), and frequent (five exposures/day). The English sole responded to the frequent risk treatment with higher feeding rates than during infrequent risk, following a pattern of behavioral response that is predicted by the risk allocation hypothesis; rock sole and halibut did not follow the predicted pattern, but this may be due to the limited range of treatments. Our observations of unique anti-predator strategies, along with differences in foraging and species-specific ecologies, suggest divergent trajectories of risk allocation for the three species.     

Predation risk and foraging behavior of the hoary marmot in Alaska

Summary I observed hoary marmots for three field seasons to determine how the distribution of food and the risk of predation influenced marmots' foraging behavior. I quantified the amount of time Marmota caligata foraged in different patches of alpine meadows and assessed the distribution and abundance of vegetation eaten by marmots in these meadows. Because marmots dig burrows and run to them when attacked by predators, marmot-toburrow distance provided an index of predation risk that could be specified for different meadow patches.Patch use correlated positively with food abundance and negatively with predation risk. However, these significant relationships disappeared when partial correlations were calculated because food abundance and risk were intercorrelated. Using multiple regression, 77.0% of the variance in patch use was explained by a combination of food abundance, refuge burrow density, and a patch's distance from the talus where sleeping burrows were located. Variations in vigilance behavior (look-ups to search for predators while feeding) according to marmots' ages, the presence of other conspecifics, and animals' proximity to their sleeping burrows all indicated that predation risk influenced foraging.In a forage-manipulation experiment, the use of forage-enhanced patches increased six-fold, verifying directly the role of food availability on patch used. Concomitant with increased feeding, however, was the intense construction of refuge burrows in experimental patches that presumably reduced the risk of feeding. Thus, I suggest that food and predation risk jointly influence patch use by hoary marmots and that both factors must be considered when modeling the foraging behavior of species that can be predator and prey simultaneously.     

Effect of sub-lethal damage to juvenile colonies of massive Porites spp. under contrasting regimes of temperature and water flow

In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50′, S 17°30′) were damaged and exposed to contrasting conditions of temperature and flow to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and 29.6°C) and flow (6 and 21 cm s⁻¹), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F _v/F _m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected F _v/F _m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s⁻¹, but a 4% increase at 21 cm s⁻¹. Regardless of damage, F _v/F _m at 21 cm s⁻¹ was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s⁻¹. The lesions declined in area at similar rates (4–5% day⁻¹) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s⁻¹. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions, and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways in which poritid corals respond to biting by certain corallivorous fishes.     

Predation on egg capsules of <Emphasis Type="Italic">Zidona</Emphasis><Emphasis Type="Italic">dufresnei</Emphasis> (Volutidae): ecological implications

Among the diverse patterns of energy allocation to the offspring of gastropods, the presence of egg capsules to protect embryos is common. Females of the edible snail Zidona dufresnei attach egg capsules to hard substrates in shallow Argentine Patagonian waters (40°45′S, 64°56′W) during spring-summer. Embryonic development takes about 30 days at 22°C. In this study, three likely capsule predator species and the marks left by each on egg capsule walls were identified in laboratory experiments in February 2010. Abundances of predators and egg capsules with evidence of predation were assessed in the field in the summers of 2010 and 2011. Under laboratory conditions (N = 10 replicates per treatment and control), the predation rate by the chiton Chaetopleura isabellei was the highest (up to 90%), followed by the gastropod Tegula patagonica and the crab Neohelice granulata (~20% each). Nearly 60% of 41 capsules found in the field showed signs of predation. According to the marks identified in the laboratory, C. isabellei was responsible for 79% of this predation, and T. patagonica for the rest. Predation appears to be important during the encapsulated early life and could be an agent for selecting for resistant capsule walls and a relatively shorter development time.     

Predation, scramble competition, and the vigilance group size effect in dark-eyed juncos (Junco hyemalis)

In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment and more time to feeding. This vigilance “group size effect” has long been attributed to the anti-predatory benefits of group living, but many investigators have suggested that this effect may be driven by scramble competition for limited food. We addressed this issue of causation by focusing on the way in which the scan durations of free-living dark-eyed juncos (Junco hyemalis) decrease with group size. We were particularly interested in vigilance scanning concomitant with the handling of food items, since a decrease in food handling times (i.e. scan durations) with increasing group size could theoretically be driven by scramble competition for limited food resources. However, we showed that food-handling scan durations decrease with group size in an environment with an effectively unlimited food supply. Furthermore, this food-handling effect was qualitatively similar to that observed in the duration of standard vigilance scans (scanning exclusive of food ingestion), and both responded to changes in the risk of predation (proximity of a refuge) as one might expect based upon anti-predator considerations. The group size effects in both food-handling and standard scan durations may reflect a lesser need for personal information about risk as group size increases. Scramble competition may influence vigilance in some circumstances, but demonstrating an effect of competition beyond that of predation may prove challenging. Received: 22 September 1998 / Received in revised form: 1 February 1999 / Accepted: 14 February 1999     

Mussels flexing their muscles: a new method for quantifying bivalve behaviour

We employed a novel technique to quantify how blue mussels Mytilus edulis react to predation risk in their environment by quantifying mussel gape using a Hall sensor attached to one shell valve reacting to a magnet attached to the other. Change in gape angle per second (CHIGA) versus gape angle plots resulted in a distribution with a boundary, which defined the maximum CHIGA of a mussel at all gape angles. CHIGA boundary plots for all individual mussels were similar in form. However, the CHIGA boundary increased in extent with mussel length (maximum CHIGA for mussel valve closures for mussels 2.98 and 79.6 mm long were −1.5 and −11°s⁻¹, respectively), showing that larger mussels opened and closed most rapidly. Mussel extract added to the seawater, a factor believed to signal predation, caused mussels to close significantly faster than otherwise (P < 0.001). This approach for assessing how mussels react to their environment indicates that mussel response to predation is graded and complex and may well indicate animal-based assessments of the trade-off between effective feeding and the likelihood of predation.     

The effects of zooplankton swimming behavior on prey-capture kinematics of red drum larvae, <Emphasis Type="Italic">Sciaenops ocellatus</Emphasis>

Most marine fishes undergo a pelagic larval phase, the early life history stage that is often associated with a high rate of mortality due to starvation and predation. We present the first study that examines the effects of prey swimming behavior on prey-capture kinematics in marine fish larvae. Using a digital high-speed video camera, we recorded the swimming velocity of zooplankton prey (Artemia franciscana, Brachionus rotundiformis, a ciliate species, and two species of copepods) and the feeding behavior of red drum (Sciaenops ocellatus) larvae. From the video recordings we measured: (1) zooplankton swimming velocity in the absence of a red drum larva; (2) zooplankton swimming velocity in the presence of a red drum larva; and (3) the excursion and timing of key kinematic events during prey capture in red drum larvae. Two-way ANOVA revealed that: (1) swimming velocity varied among zooplankton prey; and (2) all zooplankton prey, except rotifers and ciliates, increased their swimming velocity in the presence of a red drum larva. The kinematics of prey capture differed between two developmental stages in S. ocellatus larvae. Hyoid-stage larvae (3–14 days old) fed on slow swimming B. rotundiformis (rotifers) while hyoid-opercular stage larvae (15 days and older) ate fast moving A. franciscana. Hyoid-opercular stage red drum larvae had a larger gape, hyoid depression and lower jaw angle, and a longer gape cycle duration relative to their hyoid-stage conspecifics. Interestingly, the feeding repertoire within either stage of red drum development was not affected by prey type. Knowledge of the direct relationship between fish larvae and their prey aids in our understanding of optimal foraging strategies and of the sources of mortality in marine fish larvae.     

The effects of symbiotic state on heterotrophic feeding in the temperate sea anemone <Emphasis Type="Italic">Anthopleura elegantissima</Emphasis>

The temperate sea anemone Anthopleura elegantissima is facultatively symbiotic with unicellular algae. Symbiotic A. elegantissima can supplement heterotrophic feeding with excess photosynthate from their algal partners, while asymbiotic individuals must rely solely on heterotrophy. A. elegantissima individuals were collected from Swirl Rocks, Washington (48°25′6″ N, 122°50′58″ W) in July 2010, and prey capture and feeding characteristics were measured to determine whether asymbiotic individuals are more efficient predators. Feeding abilities were then measured again after a 3-week exposure to full sunlight or shaded conditions. Freshly collected asymbiotic anemones had larger nematocysts, but symbiotic individuals showed greater nematocyte sensitivity. Sunlight enhanced digestion and reduced cnida density in all anemones regardless of symbiotic state. Results suggest that the phototropic potential of A. elegantissima, as influenced by symbiotic condition, has little effect on heterotrophic capacity. The anemones appear to maximize heterotrophic energy input independent of the presence or identity of their algal symbionts.     

Spatiotemporal variation in the population ecology of scaly slipper lobsters <Emphasis Type="Italic">Scyllarides squammosus</Emphasis> in the Northwestern Hawaiian Islands

Scaly slipper lobster (Scyllarides squammosus) population ecology was examined using tag/recapture information at Necker Island (23°30′N; 164°35′W), Gardner Pinnacles (25°00′N; 168°50′W), Maro Reef (25°30′N; 170°45′W), and Laysan Island (25°48′N; 171°45′W) in the Northwestern Hawaiian Islands (NWHI) USA from 2002 to 2008. Although many aspects of S. squammosus life history and population dynamics were similar to those of other scyllarids, somatic growth differed from its congers. Scyllarides squammosus growth abruptly declined at maturity and, because of this, growth at length was better described using the Schnute as opposed to the more commonly von Bertalanffy growth model. Growth varied among locations, and survival varied among years; thereby being the first documentation of variability in the life history of a scyllarid. This study has expanded knowledge of scyllarid biology and documented that spatiotemporal variability in biological characteristics must be considered to understand and describe the population ecology of this species and probably of other scyllarids.     

Scarred limpets at hydrothermal vents: evidence of predation by deep-sea whelks

The chaotic physical and chemical environment at deep-sea hydrothermal vents has been associated with an ecosystem with few predators, arguably allowing the habitat to provide refuge for vulnerable species. The dominance of endemic limpets with thin, open-coiled shells at north Pacific vents may support this view. To test their vulnerability to predation, the incidence of healed repair scars, which are argued to reflect non-lethal encounters with predators, were examined on the shells of over 5,800 vent limpets of Lepetodrilus fucensis McLean (1988) that were collected from 13 to 18 August 1996. Three vent fields on the Juan de Fuca Ridge at ca. 2,200 m depth were sampled, two within 70 m of 47°56.87′N 129°05.91′W, and one at 47°57.85′N 129°05.15′W with the conspicuous potential limpet predators, the zoarcid fish Pachycara gymninium Anderson and Peden (1988), the galatheid crab Munidopsis alvisca Williams (1988), and the buccinid snail Buccinum thermophilum Harasewych and Kantor (2002). Limpets from the predator-rich vent were most often scarred, a significant difference created by the high incidence of scars on small (<4 mm long) limpets in this sample. Collected with the limpets were small (median shell diameter 4.4 mm) buccinids. They, rather than the larger, more conspicuous mobile fishes and crabs are argued to be the shell-damaging predator. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of simulated sublethal predation on the growth and regeneration rates of a spionid polychaete in laboratory flumes

Most spionid polychaetes switch from deposit feeding to suspension feeding as current speed and the flux of suspended food increase. Growth rates of juvenile Polydora cornuta are strongly affected by flow and can be as rapid as 60% day⁻¹ in moderate currents. Feeding palps that extend above the sediment–water interface during suspension feeding are especially vulnerable to sublethal predation, but individuals with damaged posteriors are also common. We performed a series of laboratory flume experiments to test the effects of sublethal tissue damage on the growth and regeneration rates of P. cornuta juveniles. Replicated experiments were conducted at three flow speeds in counter-rotating annular flumes containing field-collected sediment and a nonliving algal slurry as deposited and suspended food. In the first set of experiments, we removed 2, 1, or 0 of worms’ two feeding palps and measured the relative growth rates of worm bodies and palps after 3 days in the flumes. Worms that lost both palps grew significantly slower than the other two groups, but the growth rate of worms that had one undamaged palp was not significantly different from worms that had two undamaged palps. Faster flow speeds significantly increased rates of body growth, and there was a significant interaction between flow and the effect of palp loss. During the 3-day experiments, damaged palps fully regenerated and often grew larger than they were prior to being removed. Damaged palps also grew significantly faster than undamaged palps. The second set of experiments tested the effects of removing a worm’s posterior region (~18% of body volume). The growth rates of these damaged and undamaged worms did not differ significantly. By the end of a 3-day flume experiment, damaged worms had grown 6× larger than they were prior to the posterior damage. The rapid regeneration of damaged palps and posterior tissue in moderate flows that allow suspension feeding suggests that sublethal predation on spionids might be more frequent than previously estimated and will have little impact on the growth of juvenile recruits.     

Facultative lecithotrophy during larval development of the burrowing shrimp Callianassa tyrrhena (Decapoda: Callianassidae)

Survival, developmental and consumption rate (Artemia nauplii ingested per day) as well as predation efficiency (ingested per available Artemia nauplii) were studied during the larval development of the shallow-water burrowing thalassinid Callianassa tyrrhena (Petagna, 1792), which exhibits an abbreviated type of development with only two zoeal stages and a megalopa. The larvae, hatched from berried females from S. Euboikos Bay (Aegean Sea, Greece), were reared at 10 temperature–food density combinations (19 and 24 °C; 0, 2, 4, 8 and 16 Artemia nauplii d⁻¹). Enhanced starvation resistance was evident: 92 and 58% of starved zoeas I molted to zoea II, while metamorphosis to megalopa was achieved by 76 and 42% of the hatched zoeas at 19 and 24 °C, respectively. The duration of both zoeal stages was affected by temperature, food density and their interaction. Nevertheless, starvation showed different effects at the two temperatures: compared to the fed shrimp, the starved zoeae exhibited accelerated development at 19 °C (8.4 d) but delayed metamorphosis at 24 °C (5.9 d). On the other hand, both zoeal stages were able to consume food at an increased rate as food density and temperature increased. Predation efficiency also increased with temperature, but never exceeded 0.6. Facultative lecithotrophy, more pronounced during the first zoeal stage of C.tyrrhena, can be regarded as an adaptation of a species whose larvae can respond physiologically to the different temperature–food density combinations encountered in the wide geographical range of their natural habitat. Received: 28 February 1998 / Accepted: 21 October 1998     

Where are larvae of the vermetid gastropod <Emphasis Type="Italic">Dendropoma maximum</Emphasis> on the continuum of larval nutritional strategies?

This study evaluated whether larvae of the Indo-Pacific vermetid gastropod Dendropoma maximum are obligate planktotrophs, or whether they exhibit an intermediate feeding strategy. Experiments were conducted in Moorea, French Polynesia (149°50′W, 17°30′S), Sep–Oct 2009, to examine D. maximum larval growth and metamorphic responses to different diets and amounts of food. Dendropoma maximum larvae required particulate food to undergo metamorphosis, but were able to survive and grow in the absence of food for up to 20 days. Larvae in Low and Unfed food treatments exhibited phenotypic plasticity by growing a larger velum (the larval feeding structure) compared with those in high food. Unfed D. maximum larvae had a slower initial growth rate; however, by 11-day post-hatch fed and unfed larvae had converged on the same mean shell height (553 μm), which was only 10% larger than the initial size at hatching. Therefore, although the nutritional strategy of D. maximum larvae is best described as obligate planktotrophy, it appears to approach an intermediate feeding strategy.