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Sex can influence patterns of parasitism because males and females can differ in encounter with, and susceptibility to, parasites. We investigate an isopod parasite (Hemioniscus balani) that consumes ovarian fluid, blocking female function of its barnacle host, a simultaneous hermaphrodite. As a hermaphrodite, sex is fluid, and individuals may allocate energy differentially to male versus female reproduction. We predicted the relationship between barnacle size and female reproductive function influences the distribution of parasites within barnacle populations. We surveyed 12 populations spanning ~400 km of coastline of southern California and found intermediate-sized barnacles where most likely to be actively functioning as females. While it is unclear why larger individuals are less likely to be actively reproducing as females, we suggest this reduced likelihood is driven by increased investment in male reproductive effort at larger sizes. The female function-size relationship was mirrored by the relationship between size and parasitism. We suggest parasitism by Hemioniscus balani imposes a cost to female function, reinforcing the lack of investment in female function by the largest individuals. Within the subset of suitable (=female) hosts, infection probability increased with size. Hence, the distribution of female function, combined with selection for larger hosts, primarily dictated patterns of infection.

Aquaculture is expected to expand significantly in the coming decades to meet growing demand. A key variable for understanding the potential benefit of and impact from this growth is efficiency; yet a comprehensive assessment of on‐farm area use and yield is limited. Much like land‐based agriculture, range and variation in yields across space, species, and practice provide insights into area use and production efficiencies. Current estimates of aquaculture yields (production per area per time) aggregate on‐farm and off‐farm land use into one 'land use' category; in contrast, we disaggregate this category to provide on‐farm yield estimates and account for water area use. We use a quantitative review of scientific literature to synthesize and compare on‐farm area use and yield patterns across countries, taxa, aquatic systems, data source, and production mode (n = 378). Because recirculating aquaculture systems (RAS) have been touted as a particularly efficient production mode, we also found estimates for RAS from industry (n = 4). Median, mean and range in yields among countries and taxa vary by orders of magnitude, with algal production greatly exceeding that of crustaceans, fishes and molluscs. Yields in marine systems were on average roughly 5× greater than yields in freshwater systems. RAS had particularly high yields but sparse data and estimates from private corporations were approximately 3.7× higher than literature estimates, on average. This comprehensive assessment of global aquaculture yields offers critical insight into the production efficiencies of different aquaculture forms and the large amount of variability, which could help guide aquaculture policy and practice. [ABSTRACT FROM AUTHOR]

Abstract Background Cnidocytes, the eponymous cell type of the Cnidaria, facilitate both sensory and secretory functions and are among the most complex animal cell types known. In addition to their structural complexity, cnidocytes display complex sensory attributes, integrating both chemical and mechanical cues from the environment into their discharge behavior. Despite more than a century of work aimed at understanding the sensory biology of cnidocytes, the specific sensory receptor genes that regulate their function remain unknown. Results Here we report that light also regulates cnidocyte function. We show that non-cnidocyte neurons located in battery complexes of the freshwater polyp Hydra magnipapillata specifically express opsin, cyclic nucleotide gated (CNG) ion channel and arrestin, which are all known components of bilaterian phototransduction cascades. We infer from behavioral trials that different light intensities elicit significant effects on cnidocyte discharge propensity. Harpoon-like stenotele cnidocytes show a pronounced diminution of discharge behavior under bright light conditions as compared to dim light. Further, we show that suppression of firing by bright light is ablated by cis-diltiazem, a specific inhibitor of CNG ion channels. Conclusions Our results implicate an ancient opsin-mediated phototransduction pathway and a previously unknown layer of sensory complexity in the control of cnidocyte discharge. These findings also suggest a molecular mechanism for the regulation of other cnidarian behaviors that involve both photosensitivity and cnidocyte function, including diurnal feeding repertoires and/or substrate-based locomotion. More broadly, our findings highlight one novel, non-visual function for opsin-mediated phototransduction in a cnidarian, the origins of which might have preceded the evolution of cnidarian eyes.

Coral reefs are shifting from coral to algal‐dominated ecosystems worldwide. Recently, Turbinaria ornata, a marine alga native to coral reefs of the South Pacific, has spread in both range and habitat usage. Given dense stands of T. ornata can function as an alternative stable state on coral reefs, it is imperative to understand the factors that underlie its success. We tested the hypothesis that T. ornata demonstrates ontogenetic variation in allocation to anti‐herbivore defense, specifically that blade toughness varied nonlinearly with thallus size. We quantified the relationship between T. ornata blade toughness and thallus size for individual thalli within algal stands (N = 345) on seven fringing reefs along the north shore of Moorea, French Polynesia. We found that blade toughness was greatest at intermediate sizes that typically form canopies, with overall reduced toughness in both smaller individuals that refuge within the understory and older reproductive individuals that ultimately detach and form floating rafts. We posit this variation in blade toughness reduces herbivory on the thalli that are most exposed to herbivores and may facilitate reproduction in dispersing stages, both of which may aid the proliferation of T. ornata. [ABSTRACT FROM AUTHOR]

Functional groups are widely used to reduce complexity and generalize across ecological communities. These models assume that shared traits among species correspond to some ecological role, process or function, and that these traits can be leveraged to generate meaningful and distinct functional groups so that intergroup trait variation exceeds intragroup variation.We sought to validate the assumptions of the widely used functional group model (FGM) for marine macroalgae, which groups species based on morphological complexity, by testing the predictions of the FGM for several traits assumed to correspond with morphological complexity. The FGM predicts increased resistance to disturbance and herbivory as morphological complexity (tensile strength and thallus toughness, respectively) increases. The FGM also predicts a trade‐off between complexity and growth rate. To test predictions, we measured (a) thallus toughness (force to penetrate), (b) tensile strength (force to break) and (c) relative growth for both tropical and temperate macroalgae from different functional groups.Thallus toughness followed model predictions at the functional group level, though there was significant variability among species. However, the model did not predict tensile strength at any level for either tropical or temperate macroalgae. Furthermore, relative growth did not follow predictions; rather it was highly variable among species and functional groups.Synthesis. The assumptions of the FGM that differences in morphological complexity can be used to generate distinct functional groups and that intergroup trait variation outweighs intragroup variation were violated, providing strong evidence that individual species responses need to be considered. Furthermore, violations of assumptions indicate that functional groups should not be used to predict community responses to ecological drivers and/or species contributions to ecosystem function. Our study challenges the usefulness of functional form groups for marine macroalgae and emphasizes the need for a different conceptual framework. [ABSTRACT FROM AUTHOR]

Enteromorpha intestinalis was subject to nitrogen (N) and phosphorus (P) enrichment supplied in four weekly pulses in a 10:1 molar ratio with six concentrations ranging from no addition to 1000 μM NO3+100 μM PO4. The alga reduced inorganic N to very low concentrations (<3.5 μM) across all nutrient additions while a larger proportion of the added P remained in the water at the end of the experiment (up to 20 μM in highest addition). Growth of E. intestinalis increased in proportion to enrichment across the lower four of the six treatments; range of growth was −6 to 60% change from initial wet wt. N concentration in the tissue decreased at the four lower loading rates due to dilution by growth, but increased greatly (from an initial of 2.7–5% dry wt.) in the highest loading rate partially due to lack of growth in this treatment. In contrast, the mass of N in the tissue increased linearly (slope=0.012, r2=0.779, P=0.0001) over all treatments, showing that uptake and storage were not always coupled to growth. Patterns of tissue P concentration and accumulation were similar to N. Significant amounts of dissolved organic N accumulated in the water, especially in the highest N pulses. Net retention of N in algal tissue ranged from 73 to 98% while retention of P ranged from 79 to 88%; the % lowest retention occurred when nutrient pulses were either very high or low. We hypothesize that this opportunistic, bloom-forming alga is adapted to pulses of nutrients, such that, when pulses are of very high concentration, E. intestinalis can delay growth in favor of saving energy to maximize nutrient uptake and storage. [Copyright &y& Elsevier]

Coral-dominated reefs typically have abundant refuges and limited resources for herbivores; conversely, algal-dominated reefs have abundant resources but often have limited refuges. This difference results in a trade-off between risk and reward for herbivorous fishes. However, disturbances that kill coral but retain topographic complexity can decouple this tradeoff, challenging this paradigm. Many fringing reefs in Moorea, French Polynesia are algal-dominated with heterogeneous structural complexity likely driven by disturbances associated with crown-of-thorns predation and typhoons, which occurred between 2006 and 2010. Short turfs are a good recruitment surface for coral larvae, and thus has a greater potential to recover to coral dominance than long turfs. To explore how variation in complexity impacts the behavior of herbivorous fishes, we compared abundance, residence time, and time budgets of Acanthurus nigrofuscus , a common herbivore species, in paired high versus low complexity areas. We chose areas in close proximity to maximize the likelihood fish could choose between complexity types. We also measured turf height in high versus low complexity plots. Fish were ~3× more abundant, spent roughly double the time in, and budgeted more than 4× as much time to hiding in high complexity reef areas. Although, on average, individual herbivores spent the same proportion of time foraging in both areas, their greater abundance and longer residence time suggests their local herbivory rates could be 7.5 times higher in high complexity areas. We also found turfs in high complexity plots were roughly 75% the height of turfs in low complexity plots. This provides some evidence for stronger overall herbivory pressure in high complexity areas, albeit differences in absolute turf height were modest (~0.5 mm). Combined, these results suggest reefs that retain structural complexity following disturbance may be more likely to recover due to the higher localized herbivory rates resulting from uncoupling of the tradeoff between structural complexity and resource limitation. • Disturbances are shifting tropical reefs from coral to algal dominance worldwide. • Some disturbances retain reef structural complexity, potentially affecting herbivores. • We compare fish behavior and herbivory in high vs. low complexity patches of reef. • High complexity patches had shorter turf and more fish that spent more time hiding. • Co-occurrence of structural complexity and food resources may enhance reef recovery. [ABSTRACT FROM AUTHOR]

Herbivory assays are a valuable tool used by ecologists to understand many of the patterns and processes affecting herbivory, a widely recognized driving force in marine communities. However, methods vary substantially among studies in both design and operation, and the effect of these differences has yet to be evaluated. We assessed the effects of several key components of assay design on estimates of herbivory to offer four recommendations. First, we found assays out-planted on sequential days in both predictable and random locations within a 60m 2 site experienced temporal increases in herbivory by an increasingly diverse assemblage of fishes. Thus, we strongly advise against placing herbivory assays in the same site over a series of days. Second, we found while the amount of biomass consumed in assays was density dependent, the percent loss was not. Thus, we recommend researchers report percent consumption because this metric is robust to differences in biomass offered and will facilitate comparisons across studies. Third, we found associational effects, where proximity of species of differing palatabilities impacted estimates of herbivory rate on one or both species, but these impacts were not consistent across species or sites. Thus, we recommend the effect of association be directly tested for multi specie herbivory assays. Fourth, we found no effect of attachment method on estimates of herbivory rate and recommend researchers continue to use the attachment method in which they are most confident. We hope our experimental results prove useful in the future when designing, conducting, and interpreting herbivory assays., Competing Interests: CONFLICT OF INTEREST On behalf of all authors, the corresponding author states that there is no conflict of interest