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The Antarctic marine environment, although rich in life, is predicted to experience rapid and significant effects from climate change. Despite a revolution in the approaches used to document biodiversity, less than one percent of Antarctic marine invertebrates are represented by DNA barcodes and we are at risk of losing biodiversity before discovery. The ease of sequencing mitochondrial DNA barcodes has promoted this relatively ‘universal’ species identification system across most metazoan phyla and barcode datasets are currently readily used for exploring questions of species-level taxonomy. Here we present the most well-sampled phylogeny of the direct-developing, Southern Ocean nudibranch mollusc, Doris kerguelenensis to date. This study sampled over 1000 new Doris kerguelenensis specimens spanning the Southern Ocean and sequenced the mitochondrial COI gene. Results of a maximum likelihood phylogeny and multiple subsequent species delimitation analyses identified 27 new species in this complex (now 59 in total). Using rarefaction techniques, we infer more species are yet to be discovered. Some species were only collected from southern South America or the sub-Antarctic islands, while at least four species were found spanning the Polar Front. This is contrary to dispersal predictions for species without a larval stage such as Doris kerguelenensis. Our work demonstrates the value of increasing geographic scope in sampling and highlights what could be lost given the current global biodiversity crisis.

Oxygen bioavailability is declining in aquatic systems worldwide as a result of climate change and other anthropogenic stressors. For aquatic organisms, the consequences are poorly known but are likely to reflect both direct effects of declining oxygen bioavailability and interactions between oxygen and other stressors, including two—warming and acidification— that have received substantial attention in recent decades and that typically accompany oxygen changes. Drawing on the collected papers in this symposium volume (“An Oxygen Perspective on Climate Change”), we outline the causes and consequences of declining oxygen bioavailability. First, we discuss the scope of natural and predicted anthropogenic changes in aquatic oxygen levels. Although modern organisms are the result of long evolutionary histories during which they were exposed to natural oxygen regimes, anthropogenic change is now exposing them to more extreme conditions and novel combinations of low oxygen with other stressors. Second, we identify behavioral and physiological mechanisms that underlie the interactive effects of oxygen with other stressors, and we assess the range of potential organismal responses to oxygen limitation that occur across levels of biological organization and over multiple timescales. We argue that metabolism and energetics provide a powerful and unifying framework for understanding organism-oxygen interactions. Third, we conclude by out-lining a set of approaches for maximizing the effectiveness of future work, including focusing on long-term experiments using biologically realistic variation in experimental factors and taking truly cross-disciplinary and integrative approaches to understanding and predicting future effects.

Antarctic animals share many traits that are attributed to evolution in a stable, extremely cold climate. Among invertebrates, development is exceptionally slow, making observational studies of development logistically challenging, particularly when conducted under natural conditions in the field. Using multiple deployments to McMurdo Station, Antarctica, we characterized the development, in the field, of an unidentified buccinoidean gastropod species with encapsulated development. Thirteen egg capsules collected at Granite Harbor, McMurdo Sound, Ross Sea, were attached to natural rock and outplanted at a depth of ~25 m at the base of the McMurdo Intake Jetty on 2 December 2007, photographed on 5 October 2011 and 6 September 2012 and then returned to the laboratory on 27 November 2015. In 2015, four capsules were open and empty, five were open and contained a single large hatchling and the remaining four capsules were intact but not open, each containing a single large juvenile snail. To identify the developing embryos, we sequenced mitochondrial cytochrome c oxidase subunit I (COI) from two hatchlings and compared those sequences with those from adults collected near the egg mass, as well as with sequences of other buccinoideans from GenBank. Based on the close match between hatchling and adult COI sequences (hatchling sequences differed from those of an adult at only 2 of 658 nucleotide positions), we identified the embryos as Antarctodomus thielei (Powell, 1958)). The egg mass morphology and development of this species have not been previously described. Our study shows that A. thielei has a development time of more than 8 years, which is the longest measured for any gastropod.

Growth anomalies (GAs) are protuberant masses found on many coral species; their presence may be linked to increased ocean temperatures and bleaching stress. In 2014 and 2015, Hawai‘i experienced back-to-back beaching events, after which an increased number of growth anomalies were noted on massive Porites colonies. GAs and normal tissues were sampled from 19 P. evermanni and P. lobata colonies in 2015 and from each of 15 separate P. evermanni colonies on six dates from June 2016 to August 2017, encompassing two annual reproductive cycles. Compared to normal tissue, GAs had significantly larger corallites in all dimensions in both P. evermanni and P. lobata. GAs of P. evermanni also had reduced amounts of lipid and lower functional lipid ratios across all time points. Across tissue types, lipid content was generally higher in winter (December) and spring (April) than in summer months (June/July), but was not correlated with reproductive condition. While GAs are generally non-reproductive in other corals, GA tissues in P. evermanni contained elevated numbers of oocytes in 2017. Compared to normal tissue, GAs in P. evermanni had aberrant corallite morphology and likely committed proportionally more energy to growth and less to energy storage.

Thermal limits of marine ectotherms are influenced by the dynamics of oxygen supply and demand; all else being equal, as temperature increases, metabolic demand eventually outpaces an organism's capacity for oxygen uptake and delivery. We tested the combined effects of oxygen and temperature on an intertidal wave-zone obligate sea urchin , Colobocentrotus atratus, to examine whether oxygen limitation during submersion may limit the lower vertical distribution of this species. We measured survival and attachment strength under both ambient (21%) and enriched (35%) O2 conditions and at a range of temperatures between 25 and 37 °C. Oxygen enrichment increased survival at warmer temperatures, demonstrating oxygen limitation during submergence at high temperatures. Attachment strength declined with increasing temperature, but, unlike survivorship, was not affected by O 2 enrichment. Our data suggest that the lower limit on vertical distributions of C. atratus are set in part by abiotic stresses experienced under immersion, and that hypoxic stress will increase with warming sea temperatures. Thus, warmer oceans may reduce the amount of viable habitat for C. atratus, and other intertidal marine taxa that are specialized for aerial gas exchange, due to increasing abiotic stress at the bottom of their vertical distribution.

Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and 3 nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages. Deutsche Forschungsgemeinschaft BR5039/3-1 National Science Foundation ANT-0551969, ANT-0440577 Ministerio de Economía y Competitividad POL2006-06399/CGL, CTM2012-39350- C02-01 Antarctic Science AA3010 National Science Foundation IOS-1552610

Brown and beige adipose tissue are emerging as distinct endocrine organs. These tissues are functionally associated with skeletal muscle, adipose tissue metabolism and systemic energy expenditure, suggesting an inter-organ signaling network. Using a metabolomic approach we identified 3-methyl-2-oxovaleric acid (MOVA), 5-oxoproline (5OP), and β-hydroxyisobutyric acid (BHIBA) as small molecule metabokines synthesized in browning adipocytes and secreted via monocarboxylate transporters. MOVA, 5OP and BHIBA induce a brown adipocyte-specific phenotype in white adipocytes and mitochondrial oxidative energy metabolism in skeletal myocytes both in vitro and in vivo. MOVA and 5OP signal through cAMP-PKA-p38 MAPK and BHIBA via mTOR. These metabolites reduce adiposity, increase energy expenditure and improve glucose and insulin homeostasis in mouse models of obesity and diabetes. In humans, plasma and adipose tissue MOVA, 5OP and BHIBA concentrations are correlated with markers of adipose browning and inversely associated with BMI. Our findings identify beige adipose-brown adipose-muscle physiological metabokine crosstalk.

Synopsis“Polar gigantism” describes a biogeographic pattern in which many ectotherms in polar seas are larger than their warmer-water relatives. Although many mechanisms have been proposed, one idea—the oxygen–temperature hypothesis—has received significant attention because it emerges from basic biophysical principles and is appealingly straightforward and testable. Low temperatures depress metabolic demand for oxygen more than supply of oxygen from the environment to the organism. This creates a greater ratio of oxygen supply to demand, releasing polar organisms from oxygen-based constraints on body size. Here we review evidence for and against the oxygen–temperature hypothesis. Some data suggest that larger-bodied taxa live closer to an oxygen limit, or that rising temperatures can challenge oxygen delivery systems; other data provide no evidence for interactions between body size, temperature, and oxygen sufficiency. We propose that these findings can be partially reconciled by recognizing that the oxygen–temperature hypothesis focuses primarily on passive movement of oxygen, implicitly ignoring other important processes including ventilation of respiratory surfaces or internal transport of oxygen by distribution systems. Thus, the hypothesis may apply most meaningfully to organisms with poorly developed physiological systems (eggs, embryos, egg masses, juveniles, or adults without mechanisms for ventilating internal or external surfaces). Finally, most tests of the oxygen–temperature hypothesis have involved short-term experiments. Many organisms can mount effective responses to physiological challenges over short time periods; however, the energetic cost of doing so may have impacts that appear only in the longer term. We therefore advocate a renewed focus on long-term studies of oxygen–temperature interactions.

Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and three nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.

Pycnogonids in the genus Colossendeis are found in the deep sea and Southern Ocean. Although the genus contains the largest and most conspicuous species of sea spiders, little is known about their ecology or behavior. We documented two species feeding on a variety of benthic and pelagic invertebrates during three diving field seasons at McMurdo Station, Antarctica. Individuals of one species, Colossendeis megalonyx, fed on a variety of pelagic organisms, particularly the pteropod Clione antarctica. We used video to document rapid capture of individuals of C. antarctica by captive specimens of C. megalonyx in the laboratory, and we suggest that, at least in the nearshore environment, pelagic invertebrates are an important food source for this and potentially other pycnogonid species.

As the earth's climate has warmed, many tropical species have expanded their ranges poleward and encountered high-latitude seasonal temperature regimes, in which further permanent expansion is limited by physiological vulnerability to cold temperatures. The barnacle Megabalanus coccopoma is native to shorelines from Baja California to Peru and has been introduced to many locations worldwide, including the southeastern USA. The ability of larvae to develop successfully at local temperatures can be an important factor limiting the spread of invasive species. To determine if cold temperatures limited larval success near the northern range limit of M. coccopoma along the Atlantic southeastern USA coast, we measured lower temperature limits to larval development, examined the effects of temperature on larval growth and energy accumulation, and calculated a larval energy budget to estimate the extent of potential larval dispersal in this region. Larvae were able to develop through metamorphosis at 16°C, which is much colder than sea surface temperatures during the spawning season in their invasive range, making it unlikely northern range limits are set by a lower temperature limit to larval development. Energy budgets suggest that for larvae produced at the northern end of the invasive range, long distance dispersal to sites far poleward of the current range limit is possible. Similar to the findings of the handful of other studies on cold tolerances of tropical marine invertebrate larvae, larvae should be successful far poleward of current adult distributions.

The extreme and constant cold of the Southern Ocean has led to many unusual features of the Antarctic fauna. One of these, polar gigantism, is thought to have arisen from a combination of cold-driven low metabolic rates and high oxygen availability in the polar oceans (the ‘oxygen–temperature hypothesis'). If the oxygen–temperature hypothesis indeed underlies polar gigantism, then polar giants may be particularly susceptible to warming temperatures. We tested the effects of temperature on performance using two genera of giant Antarctic sea spiders (Pycnogonida), Colossendeis and Ammothea , across a range of body sizes. We tested performance at four temperatures spanning ambient (−1.8°C) to 9°C. Individuals from both genera were highly sensitive to elevated temperature, but we found no evidence that large-bodied pycnogonids were more affected by elevated temperatures than small individuals; thus, these results do not support the predictions of the oxygen–temperature hypothesis. When we compared two species, Colossendeis megalonyx and Ammothea glacialis , C. megalonyx maintained performance at considerably higher temperatures. Analysis of the cuticle showed that as body size increases, porosity increases as well, especially in C. megalonyx , which may compensate for the increasing metabolic demand and longer diffusion distances of larger animals by facilitating diffusive oxygen supply.

Nearly all marine animals harbor epibionts, organisms living on their body surfaces. The positive or negative effects that epibionts have on their hosts depend on many factors, including the size and location of the epibionts on their host. The present study examined the effects of epibionts on gas exchange, locomotion, and drag of three species of Antarctic sea spiders (pycnogonids). Sea spiders are a cosmopolitan group of marine arthropods that lack gills and rely instead on the diffusion of oxygen directly across their cuticle. Encrusting epibionts, such as bryozoans and algae, had only minor effects on surface oxygen levels, but they reduced the functional diffusion coefficient of oxygen through the cuticle by about half. Although these effects are significant locally and may be severe in individuals with high coverage by epibionts, the total coverage on most individuals was not high enough to significantly alter oxygen fluxes into the animal. Macroepibionts, such as barnacles, had no effect on host walking speeds, but they increased by two-to-threefold the drag experienced by host sea spiders. This likely increases the energetic costs of walking and increases the chance of being dislodged by high currents. These results suggest that epibionts can impose diverse costs to their hosts but only in subtle ways that depend on total epibiont coverage of the host and rates of water flow.

Many marine organisms and life stages lack specialized respiratory structures, like gills, and rely instead on cutaneous respiration, which they facilitate by having thin integuments. This respiratory mode may limit body size, especially if the integument also functions in support or locomotion. Pycnogonids, or sea spiders, are marine arthropods that lack gills and rely on cutaneous respiration but still grow to large sizes. Their cuticle contains pores, which may play a role in gas exchange. Here, we examined alternative paths of gas exchange in sea spiders: (1) oxygen diffuses across pores in the cuticle, a common mechanism in terrestrial eggshells, (2) oxygen diffuses directly across the cuticle, a common mechanism in small aquatic insects, or (3) oxygen diffuses across both pores and cuticle. We examined these possibilities by modeling diffusive oxygen fluxes across all pores in the body of sea spiders and asking whether those fluxes differed from measured metabolic rates. We estimated fluxes across pores using Fick9s law parameterized with measurements of pore morphology and oxygen gradients. Modeled oxygen fluxes through pores closely matched oxygen consumption across a range of body sizes, which means the pores facilitate oxygen diffusion. Furthermore, pore volume scaled hypermetrically with body size, which helps larger species facilitate greater diffusive oxygen fluxes across their cuticle. This likely presents a functional trade-off between gas exchange and structural support, in which the cuticle must be thick enough to prevent buckling due to external forces but porous enough to allow sufficient gas exchange.

The size, structure, and ecology of eggs shows extremely broad variation among invertebrates. The classic example of an egg is the female gamete of a sea urchin, but the term ‘egg’ can be applied to oocytes at different stages of maturation as well as embryonated eggs. Much of the composition, structure, and size of eggs can be explained by the ecology and evolutionary history of the species the eggs derive from. However, given the tremendous diversity of invertebrates, much is yet to be learned.

As environmental temperatures increase and become more seasonally variable, the ability of individuals to plastically alter their physiological responses to temperature (=acclimatize) may affect the potential for species persistence. Among marine organisms, the larval stage is often the most physiologically sensitive; larvae are also often the main dispersal stage in the life history. However, studies that address the acclimatization of marine larvae are rare. We investigated whether larvae of the gooseneck barnacle Pollicipes elegans from two temperate populations, one from the Northern Hemisphere (Mexico) and one from the Southern Hemisphere (Peru), show patterns of seasonal acclimatization to temperature. We compared the effects of temperature on swimming activity, oxygen consumption, and mortality of larvae from the two populations in both warm and cold seasons. Larvae from Mexico had higher thermal tolerances when collected in the boreal summer compared to the boreal winter, while no similar indication of seasonal acclimatization was seen in larvae from Peru. The lack of acclimatization in larvae of P. elegans from Peru may be related to recent thermal history, low selection for acclimatization due to irregular patterns of seasonal temperature change during ENSO events, or to different phylogeographic histories of Northern- and Southern-hemisphere populations.

Oxygen stress can result in slowed development or death of embryos in benthic egg masses; one potential mechanism to alleviate hypoxic stress is by photosynthesis of associated macrophytes. We tested whether the presence of macroalgae increased central oxygen saturation and decreased development time of embryos in benthic egg masses of the intertidal gastropod Siphonaria australis. Central oxygen saturation was highest when masses were maintained in the presence of algae and under lit conditions. When masses were kept in the dark or without algae, mass centers were anoxic. Central oxygen saturation was also related to the age of masses; younger masses (2 days old) had 3× higher central oxygen than older ones (6 days old). Similar results were seen in masses in natural tide pools. Almost all (98%) embryos from masses that were cultured with algae had reached late developmental stages at the onset of hatching, whereas in masses without algae, development of central embryos was comparatively delayed. These data support the hypothesis that by increasing oxygen throughout the egg mass, macroalgae (1) mitigate the effects of oxygen gradients that cause developmental asynchrony and (2) increase the proportion of offspring that are developmentally mature at the onset of hatching.

Purpose The optimal chemotherapy regimen to use with radiotherapy in stage III non–small-cell lung cancer is unknown. Here, we compare the outcome of patents treated within the Veterans Health Administration with either etoposide-cisplatin (EP) or carboplatin-paclitaxel (CP). Methods We identified patients treated with EP and CP with concurrent radiotherapy from 2001 to 2010. Survival rates were compared using Cox proportional hazards regression models with adjustments for confounding provided by propensity score methods and an instrumental variables analysis. Comorbidities and treatment complications were identified through administrative data. Results A total of 1,842 patients were included; EP was used in 27% (n = 499). Treatment with EP was not associated with a survival advantage in a Cox proportional hazards model (hazard ratio [HR], 0.97; 95% CI, 0.85 to 1.10), a propensity score matched cohort (HR, 1.07; 95% CI, 0.91 to 1.24), or a propensity score adjusted model (HR, 0.97; 95% CI, 0.85 to 1.10). In an instrumental variables analysis, there was no survival advantage for patients treated in centers where EP was used more than 50% of the time as compared with centers where EP was used in less than 10% of the patients (HR, 1.07; 95% CI, 0.90 to 1.26). Patients treated with EP, compared with patients treated with CP, had more hospitalizations (2.4 v 1.7 hospitalizations, respectively; P < .001), outpatient visits (17.6 v 12.6 visits, respectively; P < .001), infectious complications (47.3% v 39.4%, respectively; P = .0022), acute kidney disease/dehydration (30.5% v 21.2%, respectively; P < .001), and mucositis/esophagitis (18.6% v 14.4%, respectively; P = .0246). Conclusion After accounting for prognostic variables, patients treated with EP versus CP had similar overall survival, but EP was associated with increased morbidity.

Across metazoa, surfaces for respiratory gas exchange are diverse, and the size of those surfaces scales with body size. In vertebrates with lungs and gills, surface area and thickness of the respiratory barrier set upper limits to rates of metabolism. Conversely, some organisms and life stages rely on cutaneous respiration, where the respiratory surface (skin, cuticle, eggshell) serves two primary functions: gas exchange and structural support. The surface must be thin and porous enough to transport gases but strong enough to withstand external forces. Here, we measured the scaling of surface area and cuticle thickness in Antarctic pycnogonids, a group that relies on cutaneous respiration. Surface area and cuticle thickness scaled isometrically, which may reflect the dual roles of cuticle in gas exchange and structural support. Unlike in vertebrates, the combined scaling of these variables did not match the scaling of metabolism. To resolve this mismatch, larger pycnogonids maintain steeper oxygen gradients and higher effective diffusion coefficients of oxygen in the cuticle. Interactions among scaling components lead to hard upper limits in body size, which pycnogonids could evade only with some other evolutionary innovation in how they exchange gases.

Despite the importance of Nucella as a model system in numerous fields of biology, no phylogenetic analysis of the genus, including every widely recognized species, has been conducted. We have analysed about 4,500 bp of DNA from six different genes (three mitochondrial, three nuclear) from each taxon in the genus. Our results showed western Pacific N. heyseana and N. freycinetii as distinct and distantly related, but found no evidence that N. elongata is distinct from N. heyseana .W e also resolved N. heyseana as the closest living relative of the North Atlantic N. lapillus and, using the fossil record for calibration, inferred a minimum separation time between Atlantic and Pacific lineages of at least 6.2 Ma, slightly pre-dating the opening of the Bering Strait. Comparative analyses showed egg size to be evolutionarily labile, but also revealed a highly significant negative relationship between egg size and the nurse-egg-to-embryo ratio. The negative correlation indicates that evolutionary changes in egg size among species are balanced by changes in the number of nurse eggs allocated to each offspring, indicating that interspecific variation in the nurse-egg-to-embryo ratio has not been driven by divergent selection on hatching size, but may instead be a response to variation in other factors, such as parent-offspring conflict.

Planktotrophic larvae of marine invertebrates develop and grow by utilizing a com- bination of endogenous materials contained in the egg and exogenous food consumed during development. In general, larger eggs contain more reserves for morphogenesis and metabolism than smaller eggs. Interspecific comparisons among planktotrophic echinoderms have generally found that increased maternal provisioning decreases the length of development in the plankton, leading to the widely held idea that large eggs are likely to be selectively favored in low-food or high-mortality environments. Despite long interest in these patterns, however, few studies have examined how exogenous and endogenous supplies interactively affect larval development in phylogenetically controlled and environmentally relevant contexts. We investigated the direct and interactive effects of both endogenous egg materials and exogenous food supply on larval performance of 3 closely related tropical sea urchin species (Echinometra spp.). We found that egg size was positively correlated with egg energy among these 3 species, and that larvae of species with larger (and more energy-rich) eggs developed more rapidly than those from smaller (and lower-energy) eggs. Likewise, across species, larvae fed higher rations grew more rapidly than those fed less. Length of development was most strongly affected by food level in the species with the smallest eggs. Compared to the lowest food treatment, satiating levels shortened development by 9, 7, and 4 d for E. vanbrunti, E. lucunter, and E. viridis, respectively (listed in order of increas- ing egg energy). Our study supports the hypothesis that the growth and development of larvae are more strongly affected by exogenous food availability when they develop from lower-energy eggs than when larvae develop from energy-rich eggs.

Marine organisms exhibit substantial life-history diversity, of which egg size is one fundamental parameter. The size of an egg is generally assumed to reflect the amount of energy it contains and the amount of per-offspring maternal investment. Egg size and energy are thought to scale isometrically. We investigated this relationship by updating published datasets for echinoderms, increasing the number of species over those in previous studies by 62%. When we plotted egg energy versus egg size in the updated dataset we found that planktotrophs have a scaling factor significantly lower than 1, demonstrating an overall trend toward lower energy density in larger planktotrophic eggs. By looking within three genera, Echinometra, Strongylocentrotus, and Arbacia, we also found that the scaling exponent differed among taxa, and that in Echinometra, energy density was significantly lower in species with larger eggs. Theoretical models generally assume a strong tradeoff between egg size and fecundity that limits energetic investment and constrains life-history evolution. These data suggest that the evolution of egg size and egg energy content can be decoupled, possibly facilitating response to selective factors such as sperm limitation which could act on volume alone.

For the antitropical gooseneck barnacle Pollicipes elegans, population-specific physiological temperature tolerance of larvae may serve as a barrier to larval dispersal across the warmest regions of the tropical Pacific Ocean. Thermal tolerance ranges of larvae of three different populations of P. elegans sampled in 2011 and 2012 (Mexico [MX], El Salvador [ES], and Peru [PE]) were investigated by measuring three indicators of physiological performance: swimming activity, oxygen consumption, and lethality or LT50. The thermal tolerance profiles, which include measurable optimum (maximum aerobic performance), pejus (“getting worse”) and pessimum (worst aerobic performance) ranges, of larvae from the three populations were consistent with their characteristic environmental temperatures. In MX, larvae live close to the upper border of their optimum during warm months and so have a limited capacity to tolerate higher-than-normal temperatures. Larvae from the ES population likewise appear to live within their optimum temperature range, but these larvae lack a detectable pessimum range, suggesting they would be unable to cope with temperatures above their pejus range. Larvae from PE have a broad optimum but no pejus range. Different thermal tolerance ranges provide strong evidence for population-dependent physiological adaptations in P. elegans. For the southern (PE) and northern (MX) P. elegans populations, high tropical temperatures are likely to be a strong direct physiological barrier to larval survival and dispersal, which is in contrast to the more thermally tolerant ES population.

Essentially all surfaces of marine plants and animals host epibionts. These organisms may harm their hosts in a number of ways, including impeding gas exchange or increasing the costs of locomotion. Epibionts can also be beneficial. For example, they may camouflage their hosts, and photosynthetic epibionts can produce oxygen. In general, however, the costs of epibionts appear to outweigh their benefits. Many organisms, therefore, shed epibionts by grooming, molting, or preventing them from initially attaching, using surface waxes and cuticular structures. In this study, we examined how epibionts affect local oxygen supply to temperate species of pycnogonids (sea spiders). We also tested the effectiveness of different methods that pycnogonids may use to control epibionts (grooming, cuticle wettability, and cuticular waxes). In two temperate species: Achelia chelata and Achelia gracilipes, epibionts consisted primarily of algae and diatoms, formed layers approximately 0.25-mm thick, and they colonized at least 75% of available surface area. We used microelectrodes to measure oxygen levels in and under the layers of epibionts. In bright light, these organisms produced high levels of oxygen; in the dark, they had no negative effect on local oxygen supply. We tested mechanisms of control of epibionts by pycnogonids in three ways: disabling their ovigers to prevent grooming, extracting wax layers from the cuticle, and measuring the wettability of the cuticle; however, none of these experiments affected epibiont coverage. These findings indicate that in temperate environments, epibionts are not costly to pycnogonids and, in some circumstances, they may be beneficial.

The morphologically convergent larvae of the echinoderm classes Ophiuroidea and Echinoidea have been suggested to be functionally dissimilar when it comes to their capacities to feed, but little is known about whether these larvae are similar in terms of energetics. Here, we compare the energetics of early development of a tropical ophiuroid, Ophiocoma alexandri, and a temperate to tropical echinoid, Arbacia punctulata, two species with similarly sized eggs. Measurements of respiration and constituent analyses were performed on eggs and unfed larvae of both species. Members of both species showed an increase in oxygen consumption during morphogenesis followed by a lower, static rate once morphogenesis was complete (3 d for O. alexandri and 1.3 d for A. punctulata). Compared to the echinoid larvae, the ophiuroid larvae developed more slowly and had peak respiration rates that were 3.1× lower. Eggs of O. alexandri contained significantly more protein and significantly less triacylglycerol than eggs of A. punctulata. Energy utilization, as calculated via respiration measurements, closely matched decreases in energy content from the eggs to larvae as measured with biochemical constituent assays. Larvae of A. punctulata used 1.4× more energy to reach the pluteus stage than larvae of O. alexandri, and used 4× more energy during the first 9 d of larval life. These data suggest that echinoid larvae require more energy to develop to the feeding stage than ophiuroid larvae, and likewise have higher requirements for maintenance metabolism. Ophiuroid larvae may be more tolerant of low food levels due to their very low metabolic rates, but this advantage may be offset by their slower rate of development.

The fundamental constraint shaping animal systems for internal gas transport is the slow pace of diffusion [1]. In response, most macroscopic animals have evolved systems for driving internal flows using muscular pumps or cilia. In arthropods, aside from terrestrial lineages that exchange gases via tracheal systems, most taxa have a dorsal heart that drives O2-carrying hemolymph through peripheral vessels and an open hemocoel [2], with O2 often bound to respiratory proteins. Here we show that pycnogonids (sea spiders), a basal group of marine arthropods [3], use a previously undescribed mechanism of internal O2 transport: flows of gut fluids and hemolymph driven by peristaltic contractions of a space-filling system of gut diverticula. This observation fundamentally expands the known range of gas-transport systems in extant arthropods.

Morphological examination of several specimens of aeolid nudibranchs collected from the Ross Sea, Antarctica, revealed an unexpectedly high number of species. Based on the collected material the following species are re-described and for the first time their colour, reproductive anatomy and radula are illustrated together: Eubranchus glacialis, Cuthona modesta, Cuthona crinita, Cuthona elioti and Guyvalvoria paradoxa. Additionally, a new species of Cuthona is described from this area. The new species differs from other Antarctic and sub-Antarctic species of Cuthona in its external appearance, radular morphology and reproductive anatomy. Information on the egg mass and embryonic development of several species is provided.

Estradiol (E2) deficiency decreases muscle strength and wheel running in female mice. It is not known if the muscle weakness results directly from the loss of E2 or indirectly from mice becoming relatively inactive with presumably diminished muscle activity. The first aim of this study was to determine if cage activities of ovariectomized mice with and without E2 treatment differ. Ovariectomized mice were 19–46% less active than E2-replaced mice in terms of ambulation, jumping, and time spent being active ( P ≤ 0.033). After E2-deficient mice were found to have low cage activities, the second aim was to determine if E2 is beneficial to muscle contractility, independent of physical activities by the mouse or its hindlimb muscles. Adult, female mice were ovariectomized or sham-operated and randomized to receive E2 or placebo and then subjected to conditions that should maintain physical and muscle activity at a constant low level. After 2 wk of hindlimb suspension or unilateral tibial nerve transection, muscle contractile function was assessed. Soleus muscles of hindlimb-suspended ovariectomized mice generated 31% lower normalized (relative to muscle contractile protein content) maximal isometric force than suspended mice with intact ovaries ( P ≤ 0.049). Irrespective of whether the soleus muscle was innervated, muscles from ovariectomized mice generated ∼20% lower absolute and normalized maximal isometric forces, as well as power, than E2-replaced mice ( P ≤ 0.004). In conclusion, E2 affects muscle force generation, even when muscle activity is equalized.

Recently collected specimens of Armodoris from McMurdo Sound, Antarctica, were morphologically examined and sequenced. Comparison between this new material and literature sources revealed that it belongs to an undescribed species, Armodoris anudeorum. Although this new species is externally very similar to Armodoris antarctica (the only previously known species of Armodoris), these two species differ in several details of their external morphology, and particularly in their reproductive anatomy and radular morphology. This is the second known species of Armodoris; thus, this paper doubles the known diversity of this exclusively Antarctic group.

Aim The rise of the Isthmus of Panama and the formation of ‘geminate’ species pairs serves as an important model of allopatric speciation. However, to function as a model system, hypothesized geminates must first be shown to be each other’s closest living relatives. If the presence of cryptic taxa obscures true relationships, the biogeographical histories of transisthmian taxa are likely to be misinterpreted. We have therefore completed a phylogeographic survey of the transisthmian bivalve subgenus Acar in the genus Barbatia to characterize patterns of tropical American diversity and to place transisthmian taxa in a regional phylogeographic context. Location Tropical America. Methods Mitochondrial cytochrome c oxidase I (COI) and nuclear internal transcribed spacer (ITS) sequences were obtained from 233 specimens of Acar. Sequences were analysed using cladistic and Bayesian methods. Divergence times between species were inferred from net nucleotide divergences and a coalescence-based method. Results The survey revealed 22 COI clades that were also monophyletic at ITS, indicating that the taxonomy of Acar is potentially greater than a fivefold diversity underestimate. The lone previously recognized geminate [Barbatia (Acar) gradata and Barbatia (Acar) domingensis] is composed of 15 clades. Among the four transisthmian lineages identified, two diverged more than 14 Ma; the two other geminates split just prior to the time of final seaway closure. In addition to a fourfold increase in the number of known geminates, our data show that within-basin diversification has been more impressive, with one geminate splitting into five monophyletic clades in the Western Atlantic alone since seaway closure. Electron microscopy of the larval shells of specimens indicates that the transisthmian lineage with the greatest rate of post-Isthmian diversification possesses non-planktonic larvae, a life-history feature linked to high speciation rates. Main conclusions Our analyses revealed that the identities of geminate pairs split by the Isthmus of Panama were obscured by extremely high tropical American cryptic diversity. Although we have identified four geminates, only two appear to have been split by the Isthmus. Our uncovering of extensive post-Isthmian diversification is consistent with the palaeontological perspective that the final closure of the Central American Seaway was followed by high rates of subgeneric diversification, particularly in the tropical Western Atlantic.

SUMMARYThe Southern Ocean is one of the coldest, most stable marine environments on Earth and represents a unique environment for investigating metabolic consequences of low temperature. Here we test predictions of a new diffusion–reaction model of O2 distributions in egg masses,using egg masses of the Antarctic nudibranch mollusk, Tritonia challengeriana. When warmed from –1.5° to +1.5°C, embryos of T. challengeriana showed large increases in O2consumption (Q10 values of 9.6–30.0). Oxygen electrode measurements in intact masses showed, however, that O2 levels were high throughout and virtually unaffected by temperature. The model suggested that both effects stemmed from very low metabolic densities in egg masses. Detailed morphological measurements of egg masses of T. challengeriana and a temperate congener, T. diomedea, revealed large differences in structure that may be related to O2availability. Egg masses of T. challengeriana were approximately twice as thick. However, the most dramatic effects were observed in embryos:embryos of T. challengeriana were >32 times larger (by volume)than embryos of T. diomedea. Antarctic embryos also were contained singly in large egg capsules (∼500 μm diameter). Consequently,Antarctic embryos occurred at much lower densities, with very low metabolic densities.

SUMMARY We developed a novel diffusion–reaction model to describe spatial and temporal changes in oxygen concentrations in gelatinous egg masses containing live, respiring embryos. We used the model in two ways. First, we constructed artificial egg masses of known metabolic density using embryos of the Antarctic sea urchin Sterechnius neumayeri, measured radial oxygen profiles at two temperatures, and compared our measurements to simulated radial oxygen profiles generated by the model. We parameterized the model by measuring the radius of the artificial masses, metabolic densities (=embryo metabolic rate×embryo density) and oxygen diffusion coefficients at both ambient (–1.5°C) or slightly warmer (+1.5–2°C)temperatures. Simulated and measured radial oxygen profiles were similar,indicating that the model captured the major biological features determining oxygen distributions. Second, we used the model to analyze sources of error in step-change experiments for determining oxygen diffusion coefficients(D), and to determine the suitability of simpler, analytical equations for estimating D. Our analysis indicated that embryo metabolism can lead to large (several-fold) overestimates of D if the analytical equation is fitted to step-down-traces of central oxygen concentration (i.e. external oxygen concentration stepped from some high value to zero). However, good estimates of D were obtained from step-up-traces. We used these findings to estimate D in egg masses of three species of nudibranch molluscs: two Antarctic species (Tritonia challengeriana and Tritoniella belli; –1.5 and +2°C)and one temperate Pacific species (Tritonia diomedea; 12 and 22°C). D for all three species was approximately 8×10–6 cm2 s–1, and there was no detectable effect of temperature on estimated D. For the Antarctic species, D in egg masses was 70–90% of its value in seawater of similar temperature.

The study's objective was to investigate how estrogen deficiency and run training affect the tibial bone-soleus muscle functional relationship in mice. Female mice were assigned into one of two surgical conditions, ovariectomy (OVX) or sham ovariectomy (sham), and one of two activity conditions, voluntary wheel running (Run) or sedentary (Sed). To determine whether differences observed between OVX and sham conditions could be attributed to estradiol (E2), additional OVX mice were supplemented with E2. Tibial bones were analyzed for their functional capacities, ultimate load, and stiffness. Soleus muscles were analyzed for their functional capacities, maximal isometric tetanic force (Po), and peak eccentric force. The ratios of bone functional capacities to those of muscle were calculated. The bone functional capacities were affected by both surgical condition and activity but more strongly by surgical condition. Ultimate load and stiffness for the sham group were 7–12% greater than those for OVX animals ( P = 0.002), whereas only stiffness was greater for Run than for Sed animals (9%; P = 0.015). The muscle functional capacities were affected by both surgical condition and activity; however, in contrast to the bone, the muscle was more affected by activity. Po and peak eccentric force were 10–21% greater for Run than for Sed animals ( P ≤ 0.016), whereas only Po was greater in sham than in OVX animals (9%; P = 0.011). The bone-to-muscle ratios of functional capacities were affected by activity but not by surgical condition or E2 supplementation. Thus a mismatch of bone-muscle function occurred in mice that voluntarily ran on wheels, irrespective of estrogen status.

The consequences of changes in egg size for the development of marine invertebrates have been the subject of much theoretical and experimental work. Models that explore larval developmental modes in the context of ma- ternal investment per offspring are often couched in an energetic framework, but the relationships between egg size and the energetics of larval development are poorly under- stood. We used blastomere separations to examine how experimental reductions in egg size affected (1) larval met- abolic rate and (2) larval resistance to starvation. We found that separating blastomeres at the 2- and 4-cell stage re- sulted in average reductions of 50% and 75%, respectively, in larval metabolic rate. This suggests that, in an experi- mental context, mass-specific metabolic rate does not change with egg size. We also found that a 50% reduction in egg volume did not reduce the resistance of larvae to starvation when particulate food was withheld. This sug- gests that the material supplied to larvae in the egg is used primarily for construction of the larval body, rather than as a buffer against starvation or as a means of reducing reli- ance on exogenous fuel to sustain maintenance metabolism.

Skeletal muscle contractility and myosin function decline following ovariectomy in mature female mice. In the present study we tested the hypothesis that estradiol replacement can reverse those declines. Four-month-old female C57BL/6 mice ( n = 69) were ovariectomized (OVX) or sham operated. Some mice were treated immediately with placebo or 17β-estradiol (OVX + E2) while other mice were treated 30 days postsurgery. Thirty or sixty days postsurgery, soleus muscles were assessed in vitro for contractile function and susceptibility to eccentric contraction-induced injury. Myosin structural dynamics was analyzed in extensor digitorum longus (EDL) muscles by electron paramagnetic resonance spectroscopy. Maximal isometric tetanic force was affected by estradiol status ( P < 0.001) being ∼10% less in soleus muscles from OVX compared with sham-operated mice [168 mN (SD 16.7) vs. 180 mN (SD 14.4)] and was restored in OVX + E2 mice [187 mN (SD 17.6)]. The fraction of strong-binding myosin during contraction was also affected ( P = 0.045) and was ∼15% lower in EDL muscles from OVX compared with OVX + E2 mice [0.263 (SD 0.034) vs. 0.311 (SD 0.022)]. Plasma estradiol levels were correlated with maximal isometric tetanic force ( r = 0.458; P < 0.001) and active stiffness ( r = 0.329; P = 0.044), indicating that circulating estradiol influenced muscle and myosin function. Estradiol was not effective in protecting muscle against an acute eccentric contraction-induced injury ( P ≥ 0.401) but did restore ovariectomy-induced increases in muscle wet mass caused by fluid accumulation. Collectively, estradiol had a beneficial effect on female mouse skeletal muscle.

Complex life cycles involve a set of discrete stages that can differ dramatically in form and function. Transitions between different stages vary in nature and magnitude; likewise, the degree of autonomy among stages enabled by these transitions can vary as well. Because the selective value of traits is likely to shift over ontogeny, the degree of autonomy among stages is important for understanding how processes at one life-history stage alter the conditions for performance and selection at others. We pose 3 questions that help to define a research focus on processes that integrate function across life cycles. First, to what extent do particular transitions between life-history stages allow those stages to function as autonomous units? We identify the roles that stages play in the life history, types of transitions between stages, and 3 forces (structural, genetic/epigenetic, and experiential) that can contribute to integration among stages. Second, what are the potential implications of integration across life cycles for assumptions and predictions of life-history theory? We provide 3 examples where theory has traditionally focused on processes acting within stages in isolation from others. Third, what are the long-term consequences of carryover of experience from one life cycle stage to the next? We distinguish 3 scenarios: persistence (effects of prior experience persist through subsequent stages), amplification (effects persist and are magnified at subsequent stages), and compensation (effects are compensated for and diminish at subsequent stages). We use these scenarios to differentiate between effects of a carryover of state and carryover into subsequent processes. The symposium introduced by our discussion is meant to highlight how discrete stages can be functionally coupled, such that life cycle evolution becomes a more highly integrated response to selection than can be deduced from the study of individual stages.

The identification of effective, nontoxic means for physically marking and tracking marine invertebrate larvae is a necessary step towards meeting a major goal of modern marine population biology, the direct measurement of larval dispersal. An inexpensive, rapid and effective means for marking bivalve larvae would be particularly useful because, as a taxonomic group, bivalves contain many commercially important and exploited species. Likewise, bivalves produce large numbers of propagules for experimental procedures and, for many species, methods for rearing larvae have been well established. Calcein has been used as a marker in numerous studies of adults and juveniles of calcium-carbonate-containing marine organisms, but its effects on small and sensitive life history stages such as embryos and larvae can be detrimental. We show that calcein can be used to rapidly and effectively mark large numbers of larvae from two bivalve species, Argopecten irradians concentricus (Say, 1822) (the Bay Scallop)...

Previous studies of energy metabolism in larvae have described a developmental “point of no return” (PNR), a time by which larvae of planktotrophic marine species must feed in order to survive and grow. This study investigated the effects of long-term food deprivation on developing larvae of the oyster Crassostrea gigas with the goal of providing a biochemical and metabolic description of larvae at the PNR in this species. Mortality of unfed larvae was low for the first 14 days without the addition of phytoplankton foods. Even after 33 days without food, larvae were still swimming. Unfed larvae did not lose their ability to capture and digest algal cells when provided with food after 33 days. Growth, metabolic rate and biochemical constituents all increased at the same or greater rates in larvae whose feeding was delayed for 5, 8, 11, 14 or 17 days compared to larvae fed at 2 days old, when feeding was possible. These results show that larvae of C . gigas can survive long feeding delays while maintaining a constant rate of metabolism. These results suggest that oyster larvae have the capacity to survive ‘starvation’ using alternative sources of energy. If there is a “point of no return” beyond which larvae of C . gigas must feed on microalgae to survive, our findings suggest this point may be set by the availability of detrital material or dissolved organic carbon that can fuel maintenance metabolism for extended periods equivalent to over four times the predicted lifespan.

Background Polyandry is a common mating strategy in animals, increasing female fitness through direct (material) and indirect (genetic) benefits. Most theories about the benefits of polyandry come from studies of terrestrial animals, which have relatively complex mating systems and behaviors; less is known about the potential benefits of polyandry in sessile marine animals, for which potential mates may be scarce and females have less control over pre-copulatory mate choice. Here, we used microsatellite markers to examine multiple paternity in natural aggregations of the Pacific gooseneck barnacle Pollicipes elegans, testing the effect of density on paternity and mate relatedness on male reproductive success. Results We found that multiple paternity was very common (79% of broods), with up to five fathers contributing to a brood, though power was relatively low to detect more than four fathers. Density had a significant and positive linear effect on the number of fathers siring a brood, though this relationship leveled off at high numbers of fathers, which may reflect a lack of power and/or an upper limit to polyandry in this species. Significant skew in male reproductive contribution in multiply-sired broods was observed and we found a positive and significant relationship between the proportion of offspring sired and the genetic similarity between mates, suggesting that genetic compatibility may influence reproductive success in this species. Conclusions To our knowledge, this is the first study to show high levels of multiple paternity in a barnacle, and overall, patterns of paternity in P. elegans appear to be driven primarily by mate availability. Evidence of paternity bias for males with higher relatedness suggests some form of post-copulatory sexual selection is taking place, but more work is needed to determine whether it operates during or post-fertilization. Overall, our results suggest that while polyandry in P. elegans is driven by mate availability, it may also provide a mechanism for females to ensure fertilization by compatible gametes and increase reproductive success in this sessile species.

This study links offspring size and energetic content to offspring performance (measured as growth and survivorship) in the intertidal gastropod Nucella ostrina and examines the effect of hatching size on performance at different times of year and in contrasting environments. The relationships between individual hatchling size and organic content were compared both within and among clutches of N. ostrina. Hatchling size was positively, significantly, and predictively correlated with hatchling organic content both within and among clutches, demonstrating that hatching size could be reliably used as an indicator of maternal investment. The slope of the relationship between hatchling size and organic content varied between clutches, suggesting intrapopulation variation in embryonic growth geometry. In field outplants, hatching size always had a positive and significant effect on growth, and small hatchlings took approximately one month to reach the initial size of their larger siblings. More large hatchlings than small hatchlings were recovered in every experimental outplant. The effect of hatching size on recovery was not significant in short (9 d) outplants, but recovery of large hatchlings was significantly greater than recovery of small hatchlings in two out of three long-term (36 or 54 d) outplants. Overall recovery was lower in the summer, the long-term outplant in which size did not significantly affect recovery. In experiments testing the relationship between hatching size and survi- vorship in two environments that differed in degree of sun exposure, size significantly and positively affected recovery in the more shaded habitat (with higher overall recovery) but not in the sun-exposed environment. Thus, larger hatching size in N. ostrina results in (1) increased hatchling growth, (2) considerably shortened time to maturity, and (3) higher survivorship. However, the advantage of large hatching size was decreased under more severe environmental conditions, those which resulted in higher overall hatchling mortality. Contrary to predictions, poor environmental conditions may not be more likely to select for large offspring size in intertidal habitats: during periods of high heat stress, mortality may be largely random with respect to size.

A nontoxic method of marking juvenile animals is a prerequisite for many field studies investigating growth and survivorship in marine invertebrates. This study investigates the effectiveness of low concentrations of calcein in marking hatchling snails (Nucella ostrina), the durability of the calcein mark, and the effects of marking on survivorship and growth. I also describe an inexpensive means of visualizing the calcein mark under a dissecting microscope. Results demonstrate that calcein provides a long-lasting, readily detected fluorescent shell mark that can be used to measure shell growth accurately. In addition, marking with calcein did not affect survivorship or growth, and had no size-dependent effects on growth or survivorship.

Many gastropod species develop within egg capsules within which larvae are provided with extraembryonic nutrients. Species with encapsulated development frequently have transitory embryonic organs, such as "larval kidneys," that may represent specializations for consumption of intracapsular nutrition. Larvae of Littorina species with nonplanktonic, encapsulated development consume intracapsular albumen, but they lack obvious morphological modifications for albumen consumption. To determine the mechanism and location of protein uptake, larvae of seven species of Littorina (L. keenae, L. littorea, L. plena, L. saxatilis, L. scutulata, L. sitkana, L. subrotundata) were exposed to solutions of either fluorescently labeled protein (FITC-bovine serum albumen) or ferritin. Under fluorescence microscopy, larvae of all species with encapsulated, nonplanktonic development displayed strong regional affinity for FITC in the ciliated cells of the velum, whereas hatched larvae of planktotrophic Littorina species did not. Transmission electron microscopy of epithelial cells of nonplanktotrophic veligers exposed to ferritin supported the interpretation that localized affinity for labeled protein indicated endocytotic protein uptake. Planktotrophic Littorina and Littorina with encapsulated, nonplanktonic development were shown to share equivalent velar width/larval length ratios during early embryonic development, whereas a literature search suggested that in other nonplanktotrophic prosobranchs the velum is relatively smaller than in planktotrophs. Retention of a large velum in Littorina that develop entirely within egg capsules may facilitate feeding on intracapsular protein, in the absence of specialized assimilative organs found in other species with encapsulated development.

Newly settled or hatched juveniles of marine benthic invertebrates generally experience very high mortality. Juvenile mortality can profoundly affect adult populations, but little is known about how individual variation in juvenile quality affects performance. Several recent studies have demonstrated that differences in size, larval nutrient stores, or larval feeding history can strongly affect the performance (measured as growth and survivorship) of juveniles. Additional research suggests that the strength of the effect of juvenile size on performance may be mediated by variation in environmental stress in the intertidal, a habitat characterized by strong fluctuations in abiotic factors. The major sources of juvenile snail mortality are likely to differ in intertidal and subtidal habitats; abiotic stresses related to exposure, such as desiccation, are important in the intertidal but far less severe in subtidal environments. Previously observed trends in hatching or settlement size between intertidal and subtidal species from three gastropod taxa may be due to differing selective regimes acting on initial juvenile size.

An understanding of spawning and larval development can be fundamental to interpreting the abundance, distribution, and population structure of marine invertebrate taxa. Tegula funebralis (A. Adams, 1855), the black turban snail, has been the focus of numerous ecological studies on the Pacific coast of North America. To date, there are only conflicting and anecdotal reports of spawning, and there is no information on larval or juvenile development for this conspicuous and abundant species. On 19 September 1995, two individuals of T. funebralis were observed free-spawning gametes into seawater in tanks at the Oregon Institute of Marine Biology. Embryos and larvae were subsequently reared to metamorphosis and beyond. Development was pelagic and similar to development described for other trochids, and larvae were observed not to feed at any stage. Larvae began to metamorphose at 5.7 to 6.7 d and settled at 260 μm shell length. Juveniles grew ≃ 10 μm in shell length per day and appeared to feed on detritus. Juveniles lacked some adult diagnostic shell characters, including two columellar nodes and a closed umbilicus. In the field, small (

The barnacle Megabalanus coccopoma is native to shorelines from Baja California to Peru and has been introduced to a number of other locations including the Atlantic US SE coast, where it was first recorded in 2006. In 2009, the range of M. coccopoma in the SE US extended from Ft. Pierce, FL north to Cape Hatteras, NC with seasonal populations found as far north as Kitty Hawk, NC. During the exceptionally cold winter of 2009/2010, the range of M. coccopoma shifted dramatically due to the dieback of all monitored populations north of Florida. We examined body size, distribution, and density of M. coccopoma during the summers of 2010, 2011, and 2012 to describe the extent of the range retraction and the rate of range re-expansion. In 2010, recruits were found as far north as Tybee Island, Ga, but no established populations were found north of Florida. In 2011 recruits were found at Rodanthe, NC but established populations were still limited to Florida. By 2012 populations were established in Rodanthe, NC, slightly north of its previously known range limit. Estimated rates of range re-expansion were 255.8 km/yr in 2010 and 794.1 km/yr in 2011. Rates of re-expansion to the north in 2010 and 2011 were faster than have previously been reported for any marine species, and are one of the few rates published for any tropical marine invertebrate.