Differential timing of larval starvation effects on filtration rate and growth in juvenile Crepidula onyx

This study demonstrates that the timing of larval starvation did not only determine the larval quality (shell length, lipid content, and RNA:DNA ratio) and the juvenile performance (growth and filtration rates), but also determine how the latent effects of larval starvation were mediated in Crepidula onyx. The juveniles developed from larvae that had experienced starvation in the first two days of larval life had reduced growth and lower filtration rates than those developed from larvae that had not been starved. Lower filtration rates explained the observed latent effects of early larval starvation on reduced juvenile growth. Starvation late in larval life caused a reduction in shell length, lipid content, and RNA:DNA ratio of larvae at metamorphosis; juveniles developed from these larvae performed poorly in terms of growth in shell length and total organic carbon content because of “depletion of energy reserves” at metamorphosis. Results of this study indicate that even exposure to the same kind of larval stress (starvation) for the same period of time (2 days) can cause different juvenile responses through different mechanisms if larvae are exposed to the stress at different stages of the larval life.     

Different antipredator behaviour in two anuran tadpoles: effects of predator diet

Recent investigations have indicated that animals are able to use chemical cues of predators to assess the magnitude of predation risk. One possible source of such cues is predator diet. Chemical cues may also be important in the development of antipredator behaviour, especially in animals that possess chemical alarm substances. Tadpoles of the common toad (Bufo bufo) are unpalatable to most vertebrate predators and have an alarm substance. Tadpoles of the common frog (Rana temporaria) lack both these characters. We experimentally studied how predator diet, previous experience of predators and body size affect antipredator behaviour in these two tadpole species. Late-instar larvae of the dragonfly Aeshna juncea were used as predators. The dragonfly larvae were fed a diet exclusively of insects, R. temporaria tadpoles or B. bufo tadpoles. R. temporaria tadpoles modified their behaviour according to the perceived predation risk. Depending on predator diet, the tadpoles responded with weak antipredatory behaviour (triggered by insect-fed predators) or strong behaviour (triggered by tadpole-fed predators) with distinct spatial avoidance and lowered activity level. The behaviour of B. bufo in predator diet treatments was indistinguishable from that in the control treatment. This lack of antipredator behaviour is probably related to the effective post-encounter defenses and more intense competitive regime experienced by B. bufo. The behaviour of both tadpole species was dependent on body size, but this was not related to predator treatments. Our results also indicate that antipredator behaviour is largely innate in tadpoles of both species and is not modified by a brief exposure to predators. Received: 22 August 1996 / Accepted after revision: 31 January 1997     

Growth and differentiation during delayed metamorphosis of feeding gastropod larvae: signatures of ancestry and innovation

Extent of larval growth among marine invertebrates has potentially profound implications for performance by benthic recruits because body size influences many biological processes. Among gastropods, feeding larvae often attain larger size at metamorphic competence than non-feeding larvae of basal gastropod clades. Delay of metamorphosis can further influence size at recruitment if larvae continue to grow during the delay. Some caenogastopod larvae grow during delayed metamorphosis, but opisthobranch larvae do not. Data on larval growth of neritimorph gastropods are needed to help determine which of these growth patterns for planktotrophic gastropod larvae is more derived. We cultured planktotrophic larvae from all three major gastropod clades with feeding larvae through delays of metamorphosis of 3–10 weeks. Larvae of the caenogastropod Euspira lewisii and the euthyneurans Haminoea vesicula (Opisthobranchia) and Siphonaria denticulata (Pulmonata) conformed to previously described growth patterns for their respective major clades. Furthermore, the caenogastropod continued to lengthen the prototroch (ciliary band for swimming and feeding) and to differentiate prospective post-metamorphic structures (gill filaments and radular teeth) during delayed metamorphosis. Larvae of the neritimorph Nerita atramentosa arrested shell growth during delayed metamorphosis but the radula continued to elongate, a pattern most similar to that of non-feeding larvae of Haliotis, a vetigastropod genus. Character mapping on a phylogenetic hypothesis suggests that large larval size and capacity for continued growth during delayed metamorphosis, as exhibited by some caenogastropods, is a derived innovation among feeding gastropod larvae. This novelty may have facilitated post-metamorphic evolution of predatory feeding using a long proboscis.     

The deadly effects of "nonlethal" predators

Nonconsumptive predator effects are widespread and include plasticity as well as general stress responses. Caged predators are often used to estimate nonconsumptive effects, and numerous studies have focused on the larval stages of animals with complex life cycles. However, few of these studies test whether nonconsumptive predator effects, including stress responses, are exclusively sublethal. Nor have they assessed whether these effects extend beyond the larval stage, affecting success during stressful life-history transitions such as metamorphosis. We conducted experiments with larvae of a dragonfly (Leucorrhinia intacta) that exhibits predator-induced plasticity to assess whether the mere presence of predators affects larval survivorship, metamorphosis, and adult body size. Larvae exposed to caged predators with no ability to attack them had higher levels of mortality. In the second experiment, larvae reared with caged predators had higher rates of metamorphic failure, but there was no effect on adult body size. Our results suggest that stress responses induced by exposure to predator cues increase the vulnerability of prey to other mortality factors, and that mere exposure to predators can result in significant increases in mortality.     

Availability of dissolved organic matter offsets metabolic costs of a protracted larval period for <Emphasis Type="Italic">Bugula neritina</Emphasis> (Bryozoa)

For nearly a century researchers have investigated the uptake and utilization of dissolved organic matter (DOM) by marine invertebrates, but its contribution to their growth, reproduction, and survival remains unclear. Here, the benefit of DOM uptake was assessed for the marine bryozoan Bugula neritina (Linnaeus 1758) through performance comparisons of individuals in the presence and absence of DOM. The experiments were performed using B. neritina collected from floating docks in Beaufort, NC, USA from July to September 2004. Seawater was subjected to ultraviolet irradiation to reduce naturally occurring DOM, and then enriched with either 1 μM of palmitic acid or a mixture containing 1 μM each of glucose, alanine, aspartic acid and glycine. Larvae in DOM-enriched and DOM-reduced treatments were sampled and induced to metamorphose following 1, 6, 12, and 24 h of continuous swimming at 25°C. Sampled larvae were assessed for initiation of metamorphosis, completion of metamorphosis, and ancestrular lophophore size to determine the extent to which energy acquired from DOM uptake could offset the metabolic costs of prolonged larval swimming. DOM treatment had no significant effect on initiation of metamorphosis, but did have a significant effect on completion of metamorphosis and lophophore size. Larvae swimming in DOM-enriched treatments for 24 h experienced a 20% increase in metamorphic completion rate, compared to larvae swimming for 24 h in the DOM-reduced treatment. In addition, larvae in the amino acid and sugar mixture for 24 h had a significantly larger lophophore surface area and volume (23 and 31%, respectively), compared to larvae in DOM-depleted seawater. To ensure that the increases in performance found in larvae with access to DOM were not due to a decrease in metabolic activity, the respiration rates for these larvae were compared to those of larvae in DOM-depleted seawater. There were no significant differences between these treatments, indicating that the increases in performance were due to the energy acquired from DOM. These results clearly show that for B. neritina, DOM uptake results in increased metamorphic success and in the size of the feeding apparatus following an extended larval swimming duration.     

Ontogeny of predator-sensitive foraging and routine metabolism in larval shorthorn sculpin, <Emphasis Type="Italic">Myoxocephalus scorpius</Emphasis>

Most animals will reduce foraging activity in the presence of a predatory threat. However, little is known about the onset of this decision-making ability during the early life stages of fishes, and how the trade-off between foraging and predator-avoidance may be affected by changes in metabolic demand during ontogeny. To examine these issues, the foraging behaviour of larval shorthorn sculpin Myoxocephalus scorpius was monitored during visual exposure to a predatory threat (juvenile Atlantic cod, Gadus morhua) throughout development at 3°C (March–April, 2004). Larvae did not respond to predatory exposure during the first week post-hatch, but thereafter showed drastic reductions in foraging activity when exposed to predators. During early development, the mass-specific routine metabolism of shorthorn sculpin larvae displayed a triphasic ontogeny and peaked during metamorphosis. This high mass-specific metabolic demand could make reduced foraging under predation threat very costly during this stage of development. To further investigate this possibility, additional experiments were performed (March–April, 2005) where larvae were reared with visual exposure to predators for 6 h day⁻¹ during the feeding period. At 7-week post-hatch, larvae exposed to predators were smaller (wet mass and SL), showed decreased levels of whole-body lipids and certain fatty acids, and experienced higher rates of mortality as compared to control larvae. In environments where abundant predators cause larval fish to reduce their foraging rate, growth and survival of larvae may be negatively affected. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dissolved histamine: a potential habitat marker promoting settlement and metamorphosis in sea urchin larvae

Many species of marine invertebrate larvae settle and metamorphose in response to chemicals produced by organisms associated with the adult habitat, and histamine is a cue for larvae of the sea urchin Holopneustes purpurascens. This study investigated the effect of histamine on larval metamorphosis of six sea urchin species. Histamine induced metamorphosis in larvae of three lecithotrophic species (H. purpurascens, Holopneustes inflatus and Heliocidaris erythrogramma) and in one planktotrophic species (Centrostephanus rodgersii). Direct comparisons of metamorphic rates of lecithotrophic and planktotrophic larvae in assays cannot be made due to different proportions of larvae being competent. Histamine (10 μM) induced metamorphosis in 95% of larvae of H. purpurascens and H. inflatus after 1 h, while the coralline alga Amphiroa anceps induced metamorphosis in 40–50% of these larvae. Histamine (10 μM) and A. anceps induced 40 and 80% metamorphosis, respectively, in the larvae of H. erythrogramma after 24 h. Histamine (10 μM) and the coralline alga Corallina sp. induced 30 and 70% metamorphosis, respectively, in the larvae of C. rodgersii after 24 h. No metamorphosis of any larval species occurred in seawater controls. Larvae of two planktotrophic species (Tripneustes gratilla and Heliocidaris tuberculata) did not metamorphose in response to histamine. Seagrasses, the host plants of H. inflatus, induced rapid metamorphosis in larvae of the two Holopneustes species, and several algae induced metamorphosis in C. rodgersii larvae. Histamine leaching from algae and seagrasses may act as a habitat marker and metamorphic cue for larvae of several ecologically important sea urchin species.     

Correlating gene expression with larval competence,and the effect of age and parentage on metamorphosis in the tropical abalone<Emphasis Type="Italic"> Haliotis asinina</Emphasis>

The non-geniculate crustose coralline alga (CCA) Mastophora pacifica can induce the metamorphosis of competent Haliotis asinina (Vetigastropoda) larvae. The ability to respond to this natural cue varies considerably with larval age, with a higher proportion of older larvae (e.g. 90 h) able to metamorphose in response to M. pacifica than younger larvae (e.g. 66 h). Here we document the variation in time to acquisition of competence within a larval age class. For example, after 18 h of exposure to M. pacifica, approximately 15 and 36% of 84 and 90-h-old H. asinina larvae had initiated metamorphosis, respectively. This age-dependent response to M. pacifica is also observed when different aged larvae are exposed to CCA for varying periods. A higher proportion of older larvae require shorter periods of exposure to CCA than younger larvae in order to initiate metamorphosis. In this experiment, as in the previous, a small proportion of young larvae were able to respond to brief periods of CCA exposure, suggesting that they had developed the same state of competency as the majority of their older counterparts. Comparisons of the proportions of larvae undergoing metamorphosis between families reveals that parentage also has a significant (P<0.05) affect on whether an individual will initiate metamorphosis at a given age. These familial differences are more pronounced when younger, largely pre-competent larvae (i.e. 66 h old) are exposed to M. pacifica, with proportions of larvae undergoing metamorphosis differing by as much as 10 fold between families. As these data suggest that variation in the rate of development of the competent state has a genetic basis, and as a first step towards identifying the molecular basis to this variation, we have identified numerous genes that are differentially expressed later in larval development using a differential display approach. Spatial expression analysis of these genes suggests that they may be directly involved in the acquisition of competence, or may play a functional role in the postlarva following metamorphosis.Communicated by M.S. Johnson, Crawley     

Bacteria on the surface of crustose coralline algae induce metamorphosis of the crown-of-thorns starfish Acanthaster planci

The crustose coralline alga Lithothamnium pseudosorum induces high rates of settlement and metamorphosis of larvae of the coral-eating crown-of-thorns starfish (Acanthaster planci). In cases where crustose coralline algae (CCA) induce metamorphosis of marine invertebrate larvae it is normally assumed that the inductive molecules are produced by the alga, but an alternative is that they originate from bacteria on the plant surface. Bioassays using shards of L. pseudosorum treated with several antibiotics, whereby some shards were reinfected with bacteria from the alga, showed that if bacteria populations are depleted then settlement and metamorphosis of larvae of A. planci are inhibited. This demonstrates that bacteria are necessary for induction and suggests that morphogenic substances are produced by bacteria on the surface of the alga and not directly by the alga itself. However, surface bacteria are not inductive if they are isolated from soluble algal compounds, suggesting either that they require a substrate from the alga to produce the inductive agents or, alternatively but less likely, that compounds from both the alga and bacteria are required. There is no evidence that inductive compounds derive from the alga, since algal cell debris and soluble extracts prepared from the alga do not induce metamorphosis of A. planci. This is the first time that induction of metamorphosis in a marine invertebrate by CCA has been shown to be mediated by bacteria associated with the alga.     

Localized defecation by pike: a response to labelling by cyprinid alarm pheromone?

Fathead minnows (Pimephales promelas) that have never encountered a predatory pike (Esox lucius), are able to detect conspecific alarm pheromone in a pike's diet if the pike has recently consumed minnows. It remains unclear how this minnow alarm pheromone is secreted by pike and if a pike is able to avoid being labelled as a potential predator by localizing these cues away from its foraging range. The first experiment determined that minnow alarm pheromone is present in pike feces when pike are fed minnows. Individual fathead minnows exhibited a fright response to a stimulus of pike feces if the pike had been fed minnows, but not if the pike had been fed swordtails, which lack alarm pheromone. Individual minnows also exhibited a fright reaction to alarm pheromone in the water (which contained no feces) housing pike which had been fed minnows, suggesting that alarm pheromone is also released in urine, mucous secretions and/or via respiration. The second experiment determined that test pike spent a significantly greater proportion of time in the home area of the test tanks (i.e. where they were fed) but the majority of feces were deposited in the opposite end of the test tank. By localizing their defecation away from the home or foraging area, pike may be able to counter the effects of being labelled as a predator by the alarm pheromone of the prey species.     

Social feeding in ladybird beetles: adaptive significance and mechanism

Summary. Young larvae of Adalia bipunctata search an area more intensively when exposed to the odour from other larvae feeding on aphids than when exposed only to the odour of aphids. In an olfactometer young larvae were significantly attracted either to the odour of crushed aphids or larvae feeding on aphids, but not to that of aphids, larvae, larvae plus aphids or larvae feeding on an artificial diet. That is, the change in searching behaviour appears in response to a volatile released by aphids when attacked. The odour released by crushed aphids is made up entirely of aphid alarm pheromone, β-farnesene. It is likely that the adaptive significance of this response is that it increases the ability of larvae to locate larvae that have already caught prey. By sharing the aphid kill of another larva it is likely that a first instar ladybird larva greatly increases its probability of surviving to the next instar. It is suggested that this social feeding is facilitated by egg clustering, which also may additionally account for why aphidophagous ladybirds lay their eggs in clusters. Received 28 February 2000; accepted 24 March 2000     

Effects of temporary starvation on larvae of the sea star Asterina miniata

Patchy food distribution may force temporary starvation conditions on planktonic larvae. This potential food limitation may affect survivorship, duration of larval period, and post-metamorphic succes. In this study, larvae of the asteroid Asterina miniata were subjected to temporary food deprivation of several durations and at different stages. Developmental effects were documented by quantification of larval stage, total length, time to metamorphosis, initial juvenile radius, range of settling times, and percent survival to metamorphosis. All starved treatments were significantly affected in settling time and most in percent survival. However, larvae starved later in development demonstrated tremendous tolerance of food deprivation (e.g. the total number of settlers in the treatment starved for 28 d was not significantly different from the fed control). Survival was lower in treatments starved earlier in development than those starved later. Food is apparently required until late in larval development to facilitate metamorphosis. The range of settling times was large; for example, the continuously-fed control treatment produced juveniles from Days 58 through 136. Temporary starvation had no effect on initial juvenile radius.     

锌离子慢性暴露对中华大蟾蜍蝌蚪生长发育的影响

为评价水域环境中Zn~(2+)对两栖动物的毒性影响,本研究以中华大蟾蜍(Bufo gargarizans)蝌蚪为试验材料,对G26期蝌蚪进行了0、10、50、100和500μg·L~(-1)Zn~(2+)的慢性水体暴露直至蝌蚪发育至变态高峰期(G42期)。分别于暴露15 d和30 d后取样测定蝌蚪全长、体长、体重和发育分期各指标;此外,分析了Zn~(2+)慢性水体暴露对变态率、变态高峰期(G42)蝌蚪的全长、体长、体重、后肢长和骨骼发育的影响。结果表明:暴露15 d时,各浓度Zn~(2+)对中华大蟾蜍蝌蚪的生长发育均未造成显著影响,而持续暴露30 d后,500μg·L~(-1)Zn~(2+)处理组蝌蚪的生长发育受到显著抑制;各浓度Zn~(2+)慢性暴露均导致中华大蟾蜍蝌蚪变态率的下降,其中500μg·L~(-1)Zn~(2+)处理组的变态率最低;500μg·L~(-1)Zn~(2+)慢性暴露导致G42期中华大蟾蜍蝌蚪的形态指标(全长、体长、后肢长)和骨化程度均受到显著抑制。研究表明,水环境中高浓度锌对中华大蟾蜍幼体的生长发育和变态具有潜在的危害,水域锌污染所引发的毒理效应予以重视。     

Food limitation stimulates metamorphosis of competent larvae and alters postmetamorphic growth rate in the marine prosobranch gastropodCrepidula fornicata

The effects of food limitation on growth rates and survival of marine invertebrate larvae have been studied for many years. Far less is known about how food limitation during the larval stage influences length of larval life or postmetamorphic performance. This paper documents the effects of food limitation during larval development (1) on how long the larvae ofCrepidula fornicata (L.) can delay metamorphosis in the laboratory after they have become competent to metamorphose and (2) on postmetamorphic growth rate. To assess the magnitude of nutritional stress imposed by different food concentrations, we measured growth rates (as changes in shell length and ash-free dry weight) for larvae reared in either 0.45-m filtered seawater or at phytoplankton concentrations (Isoehrysis galbana, clone T-ISO) of 1 × l0³, 1 × 10⁴, or 1.8 × 10⁵ cells ml^–1. Larvae increased both shell length and biomass at 1 × 10⁴ cells ml^–1, although significantly more slowly than at the highest food concentration. Larvae did not significantly increase (p > 0.10) mean shell length in filtered seawater or at a phytoplankton concentration of only 1 × 10³ cells ml^–1, and in fact lost weight under these conditions. To assess the influence of food limitation on the ability of competent individuals to postpone metamorphosis, larvae were first reared to metamorphic competence on a high food concentration ofI. galbana (1.8 × 10⁵ cells ml^–1). When at least 80% of subsampled larvae were competent to metamorphose, as assessed by the numbers of indlviduals metamorphosing in response to elevated K⁺ concentration in seawater, remaining larvae were transferred either to 0.45-m filtered seawater or to suspensions of reduced phytoplankton concentration (1 × 10³, 1 × 10⁴, or 5 × 10⁴ cells ml^–1), or were maintained at 1.8 × 10⁵ cells ml^–1. All larvae were monitored daily for metamorphosis. Individuals that metamorphosed in each food treatment were transferred to high ration conditions (1.8 × 10⁵ tells ml^–1) for four additional days to monitor postmetamorphic growth. Competent larvae responded to all food-limiting conditions by metamorphosing precociously, typically 1 wk or more before larvae metamorphosed when maintained at the highest food ration. Surprisingly, juveniles reared at full ration grew more slowly if they had spent 2 or 3 d under food-limiting conditions as competent larvae. The data show that a rapid decline in phytoplankton concentration during the larval development ofC. fornicata stimulates metamorphosis, foreshortening the larval dispersal period, and may also reduce the ability of postmetamorphic individuals to grow rapidly even when food concentrations increase.     

Delayed growth of mussel (Mytilus edulis) and scallop (Pecten maximus) veligers at low temperatures

Veliger larvae of Mytilus edulis (L.) from Menai Straits, North Wales, were maintained for up to 2 mo during 1981 at 5°C and then grown on to metamorphosis at 17°C. Larvae so treated showed similar low mortality and equivalent spat production to control larvae. Growth rate at 17°C was less in treated larvae than in controls, but treated larvae grew a little during the period at low temperature. Larvae of Pecten maximus (L.) from the Irish Sea suffered high mortality at low temperature but larvae surviving 2 wk at 8°C could be grown on to spat at 17°C. The longevity of M. edulis larvae is discussed in relation to the genetic homogeneity of adult populations around the UK.     

Interactions of an Insecticide with Larval Density and Predation in Experimental Amphibian Communities

Abstract: This study examines the effects of the short-lived insecticide carbaryl, a neurotoxin, on amphibian communities experiencing natural stresses of competition and predation. Tadpoles of three species (  Woodhouse's toad [ Bufo woodhousii ], gray treefrog [ Hyla versicolor ], and green frog [ Rana clamitans ]), representing a commonly encountered assemblage in Missouri, were reared in outdoor polyethylene pond mesocosms. We determined the effects of initial tadpole density ( low or high), predation (newts [  Notophthalmus viridescens ] absent or present), chemical exposure (0, 3.5, or 7.0 mg /L carbaryl), and their interactions on body mass, larval period, and survival to metamorphosis. Green frogs in high-density ponds did not reach metamorphosis, but metamorphs in low-density ponds and tadpoles in high-density ponds were not significantly affected by treatments or their interaction. Carbaryl reduced survival to metamorphosis in toads and treefrogs and increased mass at metamorphosis in treefrogs. Effects of carbaryl varied with predator environment and initial larval density. Interactions of carbaryl with predator and with density may result in an indirect effect of carbaryl causing increased food resources through the elimination of zooplankton populations that may compete for similar resources. Our results indicate that differences in biotic conditions influenced the potency of carbaryl and that even low concentrations induce changes that may alter community dynamics in ways not predicted from single-factor, laboratory-based studies.     

Influence of delayed metamorphosis on survival and growth of juvenile barnacles Balanus amphitrite

Competent cyprid larvae of the barnacle Balanus amphitrite Darwin were prevented from metamorphosing in the laboratory for 3 or 5 d using three different techniques (holding at low temperature, crowding, and detaining on a silanized surface). We then assessed the effects of prolonging larval life on post-metamorphic growth and survival, in comparison with control individuals that metamorphosed soon after they were competent to do so. Seven experiments were conducted over 2 yr (July 1987 to September 1989). In all experiments (each with six replicates per treatment), postponing larval metamorphosis for 3 or 5 d dramatically depressed postmetamorphic growth rate (P<0.05), although metamorphic success and post-metamorphic survival were not affected (P>0.10). The results suggest that B. amphitrite cyprids deferring their metamorphosis in the field may be less successful in competing for space, at least during the first few weeks of postlarval life.     

Relationship between larval and juvenile growth rates in two marine gastropods,Crepidula plana and C. fornicata

Previous studies on various marine mollusc species have shown that both larval and juvenile growth rates are substantially heritable, but few workers have examined the extent to which larval and juvenile growth rates covary. We examined the relationship between larval and juvenile growth rates in seven laboratory experiments conducted between 1986 and 1993, using the prosobranch gastropods Crepidula plana Say and C. fornicata (L.). In most experiments larvae were reared individually, measured twice nondestructively to determine larval grwoth rate, allowed or stimulated (daily 5-h exposure to 20 mM excess K⁺ in seawater) to metamophose, and then measured at least twice after metamorphosis to determine juvenile growth rates. Generally, there was no significant (p >0.10) relationship between larval and juvenile growth rates, suggesting that in these two species selection can act independently on the two stages of development. A positive correlation (p=0.007) between larval and juvenile growth rates was observed for C. fornicata in one experiment, but only for offspring from females maturing the most rapidly in laboratory culture. Even for these larvae, however, variation in larval growth rate explained<2% of the variation in juvenile growth rate, so that larval and juvenile growth rates are at most only weakly associated in this species.     

Effects of temperature and salinity acclimation of adults on larval survival,physiology, and early development of Lytechinus variegatus (Echinodermata: Echinoidea)

Larval survival and developmental rates of Lytechinus variegatus (Lamarck) were determined as a function of temperature and salinity in two experiments by: (1) directly transferring fertilized eggs to 35, 30, 27.5, 25, 20, 15, and 10S seawater at 18 and 23°C, and (2) acclimation of adult sea urchins to the conditions described above for 1 to 4 wk prior to spawning. Developmental rates and percent survival of larvae prior to metamorphosis decreased at salinities below 35 (Q₁₀ values for metamorphosis=0.380 to 0.384). Temperature and salinity significantly (P<0.05) affected metabolic rates of L. variegatus plutei. These results show that L. variegatus larvae are stenohaline when compared to larvae of other echinoderm species. LC₅₀ values (S), developmental rates, and survival to metamorphosis indicate that acclimation of adult sea urchins to lower salinity prior to spawing and fertilization does not enhance development or survival of embryos exposed to low salinity.