Understanding where and why organisms are experiencing thermal and hydric stress is critical for predicting species' responses to climate change. Biophysical models that explicitly link organismal functional traits like morphology, physiology, and behavior to environmental conditions can provide valuable insight into determinants of thermal and hydric stress. Here we use a combination of direct measurements, 3D modeling, and computational fluid dynamics to develop a detailed biophysical model of the sand fiddler crab, Leptuca pugilator. We compare the detailed model's performance to a model using a simpler ellipsoidal approximation of a crab. The detailed model predicted crab body temperatures within 1 °C of observed in both laboratory and field settings; the ellipsoidal approximation model predicted body temperatures within 2 °C of observed body temperatures. Model predictions are meaningfully improved through efforts to incorporate species-specific morphological properties rather than relying on simple geometric approximations. Experimental evaporative water loss (EWL) measurements indicate that L. pugilator can modify its permeability to EWL as a function of vapor density gradients, providing novel insight into physiological thermoregulation in the species. Body temperature and EWL predictions made over the course of a year at a single site demonstrate how such biophysical models can be used to explore mechanistic drivers and spatiotemporal patterns of thermal and hydric stress, providing insight into current and future distributions in the face of climate change.

Estuarine bottoms are comprised mainly of soft sediments, with dense populations of deposit-feeders, suspension-feeders, and benthic predators. These species in the majority have planktonic larvae and a strong potential for short-term environmental responses and population fluctuations. Sea-level rise and warming will combine to rearrange salinity gradients and thermal habitats for different suites of species in response to these changes. Past nutrient instability and input, endemic to many estuarine systems, combined with future rearrangements of nutrient dynamics, will only increase population instability in estuaries owing to thermal and salinity change. Acidification resulting from current eutrophication will combine with future carbon dioxide–based ocean acidification to increase stress in diverse ways on estuarine species. Increased stress will further convert estuarine soft bottoms to domination by volatile populations, and the importance of short-term deposition of particulate organic matter on the sediment surface, selecting for shallow over deeper-burrowing species. This change in bioturbation and burrowing depth will lead to increased benthic population and bioturbation instability. Sea-level rise will also strongly impinge on edge habitats, such as intertidal beaches, coastal marshes, and mangroves. The tidal adaptations of estuarine planktonic larvae will have varying outcomes in the context of regional thermal changes and rearrangement of water flow, owing to climate change. Planktotrophic larvae adapted to export and life in shelf waters may experience disequilibria with new conditions that may reduce synchronization with phytoplankton and zooplankton blooms in shelf waters and with seasonal current changes, leading to population failures owing to failed recruitment. Species with larvae adapted to retention in the estuary may suffer strong physiological stress when they are trapped in warming estuaries. Overall warming will result in an extension of biogeographic ranges to higher latitudes and pinching of ranges at lower latitudes, as is occurring for coastal species. Warming will increase the vulnerability of estuaries to invasion, reducing local endemism and regionalism of estuarine biotas.

The objective of this study is to compare ecologically relevant measures of performance over a broad range of latitude of a species subjected to climate change. Do populations change in relative function over a wide range of latitude? Are populations at the low latitude trailing edge in danger of extinction in the onset of thermal stress? Coastal marine species with planktonic larvae can range over an enormous span of latitude and thermal environments. The fiddler crab Leptuca pugilator extends from high-latitude (41.75°N) winter-frozen Massachusetts tidal flats in the north to subtropical low latitude flats in Florida (24.55°N), where they may be active at the surface over most of the year. We characterized the air environment for males at three sites (New York – latitude 40.0°N, Beaufort, North Carolina – latitude 34.7°N, Panacea Florida, latitude 30.0°N) over the geographic-thermal range, and found major differences in temperature, wind speed, humidity, and vapor pressure deficit. Florida L. pugilator males preferred warmer sand than North Carolina and New York crabs. Local adaptation to latitude-dependent thermal conditions might suggest tradeoffs in performance as a function of temperature. We examined measures of predator escape performance (running speed and righting speed) and overall condition reflecting endurance rivalry success (endurance on a treadmill and major claw closing force) over a wide range of test temperatures. Predator escape rates increase steadily with increasing temperature, but endurance rivalry measures show an intermediate temperature peak of performance. We tested the hypothesis of tradeoffs, with expected local superiority of performance according to regional thermal differences. But instead, the trailing edge Florida males were superior to the higher latitude populations, over a broad range of temperature, but especially at higher temperatures, for all four types of performance measures. The trailing edge population of L. pugilator, in thermal terms, is therefore likely not vulnerable to near future further effects of warming in terms of performance measures related to male reproductive and feeding activities and escape from predators. Fiddler crabs appear to display niche conservatism for stronger performance at tropical temperatures. Such a natural tropical superiority in performance might have to be accommodated in future conceptions of response of marine species to climate change with broad latitudinal distributions in the tropics.

As fiddler crabs increase in size, closing force weakens proportionally because claw growth is not isometric. As a result, mechanical advantage decreases at the tip with increasing claw length. Closing force at an interior tubercle is greater at the tip, and a previous study of two species claimed evidence for compensation by relative movement of tubercles toward the hinge as size increases. I reconsidered this hypothesis with a biometric analysis of eight species from five genera and all three major biogeographic regions. I tested test two null hypotheses: 1) as claw length increases, mechanical advantage did not increase at the tubercle, relative to the claw tip, and 2) closing force did not increase at the tubercle, relative to the claw tip, as claw size increased. Both null hypotheses are largely supported, which in turn supports the weakening combatant hypothesis. In all cases, log force as a function of log claw length at an interior tubercle is 1.40, which is less than 2, the slope value expected if there was complete compensation. This is only slightly greater than the slope at the dactyl tip, which is 1.21. Thus, as a fiddler crab gets larger, with an incremental increase of claw length its closing force proportionally decreases, supporting the idea of a weakening combatant. But it gains a large showy claw with relatively narrow pincers and relatively less mass required to swing around while waving. This is indeed a beautiful weapon, but not for sheer closing force.

Using three data sources, we measured claw lengths of the extremely large major claws of 70 species of fiddler crabs, spread over four major biogeographic regions and all 11 genera, as a function of carapace length. Despite a diversity of biogeography, body size, type of sexual signaling and mating behavior, and details of claw morphology, all species groupings follow the same linear relationship. No subgroupings could be determined, by region, among diverse genera, by ancestral-derived status, or by data source. Major claw size is known to be implicated in female selection of mates, which might be expected to diversify claw lengths among species and genera, as might differences in combat might be expected to diversify claw length, as it does in other claw traits. The constancy suggests a possible functional constraint on major claw length across the fiddler crabs, which is to be determined. Efficient folding of the claw as the male rapidly retreats into a burrow, or a protection of the carapace from frontal attack by predators or combatants in an initial aggressive encounter might select for this pervasive relationship. Tests are suggested. The sexually selected major claw is more variable than the naturally selected minor claw, but this difference in variability could be attributed partially to regeneration of the major cheliped and even variation in shape. A surprising similar trend of closing force index for the major claw exists for a large number of species spread throughout the genera and major regions occupied by fiddler crabs, but a considerable variation exists in a variety of functional traits. Thus, the constancy of length relationship stands out distinctly from a considerable background variation in form. As a sexually selected trait, the claw length constancy begs for an explanation.

Male fiddler crabs possess one giant major claw, used for display and intermale combat. Comprising greater than 30% of body mass, the major claw is presumed to interfere with escape from predators by affecting balance during the righting response if the male is upended. We determined cost of the major claw and posterior legs for righting after the crab was upended in a simulated attack. In Leptuca pugilator and Minuca pugnax, males without major claws showed no difference in their righting time compared to individuals bearing major claws, but males lacking rear legs took significantly longer to right relative to intact males. The lack of cost of the major cheliped for righting time reinforces a previously determined lack of cost of the major claw in sprint speed, another measure important for escape. While the rear legs are crucial for righting, the massive claw imposes no cost to this vital response.

Benthic animals profoundly influence the cycling and storage of carbon and other elements in marine systems, particularly in coastal sediments. Recent climate change has altered the distribution and abundance of many seafloor taxa and modified the vertical exchange of materials between ocean and sediment layers. Here, we examine how climate change could alter animal-mediated biogeochemical cycling in ocean sediments. The fossil record shows repeated major responses from the benthos during mass extinctions and global carbon perturbations, including reduced diversity, dominance of simple trace fossils, decreased burrow size and bioturbation intensity, and nonrandom extinction of trophic groups. The broad dispersal capacity of many extant benthic species facilitates poleward shifts corresponding to their environmental niche as overlying water warms. Evidence suggests that locally persistent populations will likely respond to environmental shifts through either failure to respond or genetic adaptation rather than via phenotypic plasticity. Regional and global ocean models insufficiently integrate changes in benthic biological activity and their feedbacks on sedimentary biogeochemical processes. The emergence of bioturbation, ventilation, and seafloor-habitat maps and progress in our mechanistic understanding of organism–sediment interactions enable incorporation of potential effects of climate change on benthic macrofaunal mediation of elemental cycles into regional and global ocean biogeochemical models.

Many conclusions concerning the functional biology of crab claws rely upon biometrical estimates of closing force, based upon measures of muscle cross-sectional area and mechanical advantage. Fiddler crab closing force patterns show variation with body size, claw size, location of the opposing claw tips, and physiological condition, so we have measured closing force of the sand fiddler crab Leptuca pugilator (Bosc, 1801) as a function of claw size, force exerted at claw tips, and at the commonly well-developed pollex tooth. Leptuca pugilator has an elongated claw with gracile dactyl and pollex. As predicted by biometrical proportions, closing force is greater at the pollex tooth than at the claw tip. The pollex tooth does shift with increasing claw size in relative position toward the claw hinge. Mechanical advantage at the pollex tooth and dactyl tip both decline with increasing claw length. But there is no difference in slope of log closing force as a function of log claw length between the pollex position and terminus of the dactyl, which demonstrates that force exerted at the pollex tooth has no impact on proportional change in closing force with increasing claw size. The log-log slope is similar to 0.9, reflecting the proportionally decreasing muscle cross-sectional area and lowering mechanical advantage with increasing claw size. For both the pollex tooth and the claw tip, mechanical advantage decreases very slightly with increasing claw size, but closing force proportionally decreases with increasing claw size, supporting the weakening combatant hypothesis for this species.

Previous articleNext article No AccessZoologyLife Histories. The Natural History of the Crustacea, Volume 5. Edited by Gary A. Wellborn and Martin Thiel. Oxford and New York: Oxford University Press. $175.00. xiv + 438 p. + 16 pl.; ill.; index. ISBN: 9780190620271. 2018.Jeffrey LevintonJeffrey LevintonEcology & Evolution, Stony Brook University, Stony Brook, New York Search for more articles by this author Ecology & Evolution, Stony Brook University, Stony Brook, New YorkPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 95, Number 2June 2020 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/709037 Views: 33Total views on this site For permission to reuse, please contact [email protected]PDF download Crossref reports no articles citing this article.

1University of Florida, Gainesville, FL USA; tbianchi@ufl.edu, emorrison@ufl.edu 2Stony Brook University, Stony Brook, NY, USA; robert.aller@stonybrook.edu 3Utah State University, Logan, UT, USA; trisha.atwood@usu.edu 4Dalhousie University, Halifax, CA; Craig.Brown@dal.ca 5University of Saskatchewan, Saskatoon, SK, CA; luis.buatois@usask.ca 6Scripps Institution of Oceanography, La Jolla, CA, USA; llevin@ucsd.edu 7Stony Brook University, Stony Brook, NY, USA; jeffrey.levinton@stonybrook.edu 8Utrecht University, Utrecht,NL; J.B.M.Middelburg@uu.nl 9Université Libre de Bruxelles, Brussels, BE; Pierre.Regnier@ulb.ac.be 10Texas A&M University, College Station, TX, USA; mshields@tamu.edu 11Memorial University of Newfoundland, St John’s, CA; psnelgrove@mun.ca 12College of Charleston, Charleston, SC, USA; SotkaE@cofc.edu 13Bedford Institute of Oceanography, Dartmouth, Nova Scotia, CA; Ryan.Stanley@dfo-mpo.gc.ca

Mobile intertidal crabs are often exposed to the sun while displaying outside of moist and cooler breeding burrows, which imposes increased heat stress and water. Individuals of a field population in mid-summer of the fiddler crab Leptuca pugilator had body temperatures that declined with increasing body size. All crabs were cooler than the sediment surface. Laboratory experiments simulated a male leaving its burrow and standing on hot sand heated by the sun. Smaller crabs succumbed to thermal stress sooner than larger crabs. Incapacitation keyed to field sediment temperatures occurred usually in about 30 min. Water loss ranged 1-8% at incapacity Small crabs heated up as fast as large crabs. Males with a major claw gained body heat more than clawless males and succumbed sooner. The major cheliped loses water proportionally more slowly than the body, which is likely explained by the more impervious surface of the claw, suggesting the claw might be a heat sink. I hypothesized that heat may be accumulated in the relatively impermeable major cheliped and transferred to the body, increasing thermal stress in the body where crucial organs must function. Several experiments were done to attempt to demonstrate body part differences in heating or heat transfer between cheliped and body. Thermal images demonstrated a temperature excess in the manus, and a lower temperature of the dactyl, consistent with the impermeability of the manus and its larger surface area intercepting heat, and perhaps radiation from the dactyl. Immersion of major claws in warm and cold water demonstrated heat transfer between cheliped and body. If claws are painted black, they heat up faster than unpainted claws, but there was no evidence of the transfer of increased heat to the body when claws were darkened. Thus the potential for heat transfer between claw and body is probably quite limited, which is further suggested by the very narrow connection at the basal ischium segment of the cheliped.The results suggest that smaller male fiddler crabs may have reduced success in the upper intertidal partially because of their higher vulnerability to thermal stress. Smaller males may choose to avoid the hotter upper intertidal until they become larger. Experimental results show no evidence for the role of the major claw in alleviating thermal stress to the fiddler crab carapace.

Performance in poikilotherms is known to be sensitive to temperature, often with a low-sloping increase with temperature to a peak, and a steep decline with increasing temperature past the peak. We complemented past measures of performance by measuring heartbeat rates of the fiddler crab Leptuca pugilator in water and in air as a function of a range of temperatures previously shown to affect other measures of performance. In water over a range of 20-50 degrees C, heartbeat increased steadily to a peak at 40 degrees C and then steeply declined to near zero at 50 degrees C. In air, heartbeat also increased, but to a peak at 35 degrees C and then with a gentler decline than was found in water. Part of this different response may be due to evaporative water loss, which reduced body temperature in air, and therefore thermal stress, relative to body temperature when crabs were immersed in water. Increased availability of oxygen from air, according to the oxygen and capacity-limited thermal tolerance hypothesis, likely increased aerobic scope past the thermal peak, relative to within water, where oxygen delivery at higher temperatures may have been curtailed. We compared the heart rate performance relations to two previous measures of performance - endurance on a treadmill and sprint speed, both done in air. The peak performance temperature increased in the order: treadmill endurance time, sprint speed, heart rate in air, and heart rate in water, which demonstrates that different performance measures give different perspectives on the relation of thermal tolerance and fitness to temperature. Endurance may therefore be the limiting upper thermal stress factor in male fiddler crabs, when on hot sand flats. Temperature preference, found to be for temperatures <30 degrees C in air, could be a bet-hedging evolutionary strategy to avoid aerobic scope affecting endurance.

The filtering capacity of dense bivalve populations can exert strong controls on phytoplankton biomass. leading to increased water clarity and reduced hypoxia. Bivalves, particularly oysters, therefore are the focus of many restoration efforts and ecosystem-based management plans. The hypothesis is tested that oysters have feeding access to the classic major phytoplankton bloom of the year in winter spring. Jamaica Bay is a highly eutrophic urban estuary where oyster restoration is being considered as a means to improve water quality. Strong winter-spring and summer phytoplankton blooms occur in Jamaica Bay, and oyster feeding rates and oxygen consumption were examined to see if oysters would be able to feed during both seasonal pulses of phytoplankton. Temperature-related feeding rates were found to vary to the degree that feeding did not occur at the cold temperatures that exist during the winter-spring blooms. Indeed, feeding rate and proportion feeding were found to be zero at 10 degrees C, which corresponds to March-April. But feeding would be vigorous in late spring and summer. Oysters, therefore, do not have the ability to regulate a major fraction of phytoplankton during the year in Jamaica Bay and likely in the rest of the mid-Atlantic states region and New England. Feeding rates are much higher during the time of the summer blooms, and oysters in shallow well-mixed waters would, therefore, have access to feeding and possibly control of phytoplankton biomass at this time.

Previous articleNext article FreeEcologyA Sea of Glass: Searching for the Blaschkas’ Fragile Legacy in an Ocean at Risk. Organisms and Environments, Volume 13. By Drew Harvell; Foreword by Harry W. Greene. Oakland (California): University of California Press. $29.95. xii + 215 p.; ill.; index. ISBN: 978-0-520-28568-2 (hc); 978-0-520-96111-1 (eb). 2016.Jeffrey LevintonJeffrey LevintonEcology & Evolution, Stony Brook University, Stony Brook, New York Search for more articles by this author Ecology & Evolution, Stony Brook University, Stony Brook, New YorkPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreThis delightful volume is meant to be a physical paper book. You simply have to start by thumbing through its pages, marveling at the color plates. And will you notice that most of them are photographs of delicate glass representations of marine animals instead of real live creatures? It will take a while, for the Blaschkas (father and son) were great and accurate artists, even if they were scrupulous collectors and observers. Okay, now you have finished thumbing … now read the volume from front to back. It is filled with everything from the wonderful story of the creators of these glass wonders (also fabricators of the amazing glass flowers on display at the Museum of Comparative Zoology at Harvard) to the story of Harvell’s first encounter with Cornell University’s stellar collection to her many adventures, natural history and diving anecdotes, and a sense of wonder of an ocean that is more and more at risk. As you read, you will learn how observational skill can merge with great art. These exquisite worms, starfish, sea slugs, and so much more were meant to educate. Many of them (once restored) are lovely and colorful visual pieces, but often as not they have enough anatomical detail to use in a college laboratory for invertebrate zoology. Harvell’s story of the glass is balanced in a lovely way with excursions on the history of the collection, ecology of many fascinating and consequential marine creatures (you must linger on the sea slugs), and the dangerous slide that our world ocean is taking. You will want this book and then you will want to give it to one and all for a delightful and stimulating introduction to our wonderful ocean creatures. Previous articleNext article DetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 92, Number 1March 2017 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/690858 For permission to reuse, please contact [email protected]PDF download Crossref reports no articles citing this article.

In this study, the subject of whether investment in one bilateral structure was linked to investment in the homologous bilateral opposite structure was investigated. Male fiddler crabs (genus Uca, family Ocypodidae) displayed strong bilateral claw differentiation of function and size, which are used for feeding (minor claw) or display/combat (major claw). Females had similar-sized feeding claws. Linkage between claw size was investigated by estimating the deviations from an overall fitted regression of claw length to body size. The positive correlations of the deviations of claw size for major and minor claws of males and between right and left claws of females, relative to body size, suggested a linkage in investment between one claw and the corresponding claw on the other side of the body, for both monomorphic females and dimorphic males. A signal to send resources may be effectively gated to the claw complex, suggesting that positively correlated resources are allocated to both claws. Positive correlations were also found at the interspecific level. The fiddler crab model, described here, gives access to study the linkage in symmetric and asymmetric bilateral structures in the same species with a connection to the macroevolutionary level.

Theory predicts that genetic variation should be reduced at range margins, but empirical support is equivocal. Here, we used genotyping-by-sequencing technology to investigate genetic variation in central and marginal populations of two species in the marine gastropod genus Crepidula. These two species have different development and dispersal types and might therefore show different spatial patterns of genetic variation. Both allelic richness and the proportion of private alleles were highest in the most central populations of both species, and lower at the margin. The species with low dispersal, Crepidula convexa, showed high degrees of structure throughout the range that conform to the pattern found in previous studies using other molecular markers. The northernmost populations of the high-dispersing species, Crepidula fornicata, are distinct from more central populations, although this species has been previously observed to have little genetic structure over much of its range. Although genetic diversity was significantly lower at the range margin, the absolute reduction in diversity observed with these genomewide markers was slight, and it is not yet known whether there are functional consequences for the marginal populations.

Previous articleNext article No AccessConservation BiologyDDT Wars: Rescuing Our National Bird, Preventing Cancer, and Creating the Environmental Defense Fund. By Charles F. Wurster. Oxford and New York: Oxford University Press. $24.95. xxiii + 231 p.; ill.; index. ISBN: 978-0-19-021941-3. 2015.Jeffrey LevintonJeffrey LevintonEcology & Evolution, Stony Brook University, Stony Brook, New York Search for more articles by this author Ecology & Evolution, Stony Brook University, Stony Brook, New YorkPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 91, Number 2June 2016 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/686834 Views: 73Total views on this site For permission to reuse, please contact [email protected]PDF download Crossref reports no articles citing this article.

Field measures of stress are needed to understand the role of behavior in stress and how behavior trades off with overall fitness. Along Atlantic shores, displaying and reproductive burrow-occupying males of the fiddler crab Uca pugilator live in high intertidal dry sandy sediments, whereas Uca pugnax live in lower intertidal wetter muddy substrata. Water loss was examined in the lab for both species. Water loss of U. pugilator males was approximately linear with time and crabs regained water completely after 2h of rehydration. Percent water loss was inversely correlated with body mass, irrespective of sex. Males of the higher intertidal U. pugilator lost proportionally less water over time than U. pugnax, which occupies muddier and wetter sediments. A field test of water state on a hot day demonstrated that males of either species seen at the surface next to mating burrows were not stressed for water, suggesting that behavior compensated adequately for water loss when displaying in the sun on the surface. Behavior can therefore compensate for what appears to be a stressful environment. However, such compensation likely comes at the cost of reproductive success, which depends upon remaining on the sediment surface in open stressful conditions. Large-sized males may be more successful in breeding territories owing to their proportionately lower water loss.