Source populations in coastal crabs: population parameters affecting egg production (original) (raw)
Related papers
Full of eggs and no place to lay them: hidden cost of benthic development
Marine Ecology Progress Series, 2005
The scarcity of sites suitable for attaching eggs may be a hidden cost to depositing embryos in benthic aggregations. We tested this hypothesis with the bubble-shell snail Haminaea vesicula, which lives on mud or sand but requires firm substrata for attaching its eggs. In pools on a sandflat where firm substrata were scarce, the preferred substrata were but a small fraction of the total available firm substrata. Abundant drifting green algal blades comprised 1 to 11% cover but were rarely used for egg deposition. Substrata commonly used for egg deposition totaled less than 1% cover, and included attached and drifting eelgrass, drifting branched red algae, bivalve shells, and attached green algal blades. In choice experiments, the snails preferred to deposit eggs on branched red algae and eelgrass, with bivalve shells next and green algal blades last. To test the hypothesis that substratum availability limits egg deposition, we added artificial eelgrass made of duct tape to tidepools inhabited by the snails. The mean number of egg ribbons laid m-2 in the experimental areas was 20 to 360 times that in control areas, and the mean number of adult snails present and egg ribbons per adult snail were greater in the experimental areas. Also, more egg ribbons per adult were deposited on artificial eelgrass when it was positioned away from natural eelgrass patches, indicating that distances of a few meters affect availability of substrata for deposition. The results imply that in this habitat the snails travel to scarce substrata for egg deposition, with whatever costs in time, energy, or risk that may be associated with travel. Scarcity of suitable sites for benthic egg masses can limit an apparently safe mode of development. Habitats that regularly support adult populations can differ greatly in suitability for egg deposition, but this limitation may not be apparent without experimental intervention.
2008
Crabs are amongst the most conspicuous and ecologically important organisms inhabiting nearshore environments. Their complex life cycle and bioindicator capacity makes them good models for the study of distribution and abundance patterns of marine fish and benthic invertebrate populations. Such knowledge is essential for explaining species occurrence and demographic patterns, predicting the success of biological indicators and controls, as well as for conservation and management purposes of exploited populations and ecosystems. In this study, the impacts of specific environmental constraints at different life phases of estuarine and coastal crabs on population structure and physiological condition were evaluated and related to habitat quality. During settlement and recruitment events, the patchiness of artificial substrates significantly influenced settlement estimation, and strong water currents might have resulted in a decoupling pattern between supply and settlement. Estuarine sandy habitats presented higher quality for early recruits than seagrass ones. In fact, vegetated habitats were not of higher quality for crab populations than non-vegetated and rocky-shore ones. Adult-juvenile cannibalism showed potential to structure intertidal crab assemblages, especially under shortage of food and refuge. Interestingly, mangrove crabs were more affected by climatic season than by pollution, and coped well with several combinations of vegetation and sewage load. Specific constraints of different life stages, individually and in combination, must be considered for full understanding distribution and abundance patterns of crab populations. Furthermore, the relative importance of a specific constraint is likely to change throughout ontogenesis, and the mechanisms by which it interacts with other environmental variables and processes, sometimes synergistically, have also to be considered. This study constitutes an extension to the knowledge on population structure and physiological condition of coastal and estuarine crabs and other marine invertebrate and fish species, and on their use as indicators of ecological status of habitats and ecosystems.
Integrative and Comparative Biology, 2011
Synopsis Most semiterrestrial, intertidal and shallow subtidal brachyuran crabs that live in tropical and warm temperate estuaries, bays and protected coasts worldwide release their planktonic larvae near the times of nocturnal high tides on the larger amplitude tides in the biweekly or monthly cycles of tidal amplitude. Crab larvae usually emigrate quickly to the sea where they develop to return as postlarvae to settle in habitats suitable for their survival. Predators of larvae are more abundant where larvae are released than where they develop, suggesting that this migration from estuaries to the sea reduces predation on larvae. Crabs with larvae that are relatively well-protected by spines and cryptic colors do not emigrate and often lack strong reproductive cycles, lending support to this explanation. Adults control the timing of the release of larvae with respect to the biweekly and monthly cycles of tidal amplitude by controlling when they court and mate and females control when development begins by controlling when they ovulate and allow their eggs to be fertilized by stored sperm. By changing the time they breed, fiddler crabs (Uca terpsichores) compensate for the effects of spatial and temporal variation in incubation temperature on development rates so that embryos are ready to hatch at the appropriate time. Control of the diel and tidal timing of hatching and of release of larvae varies with where adults live. Females of the more terrestrial species often move from protected incubation sites, sometimes far from water, and they largely control the precise time, both, of hatching and of release of larvae. Females of intertidal species also may influence when embryos begin to hatch. Upon hatching, a chemical cue is released that stimulates the female to pump her abdomen, causing rapid hatching and release of all larvae in her clutch. Embryos, rather than females, largely control hatching in subtidal species, perhaps because females incubate their eggs where they release their larvae. Topics for further study include the mechanism whereby adults regulate the timing of breeding, the mechanisms by which females control development rates of embryos, the nature of communication between females and embryos that leads to precise and synchronous hatching by the number (often thousands) of embryos in a clutch, and the causes of selection for such precision. The timing of hatching and of release of larvae by cold-temperate, Arctic, and Antarctic species and by fully terrestrial and freshwater tropical species has received little attention.
Biological Bulletin, 1987
The relationship between egg number, size, and year class was determined for sand crabs (Emerita ana.loga) collected at three California sites, including two differ ent dates for two ofthose sites. Size frequency distributions ofsand crab population samples collected in 1982 from San Clemente, Goleta (2 dates), and Pismo Beach (2 dates) were separated into three modal size/year classes before plotting the size and egg number data and calculating regressions for egg number as a function ofsize. The slope ofthe regressions for within year class data generally decreased with increase in age. Both seasonal and locality differences were found in comparisons of data for individual year classes. The technique can be used to compare egg production be tween female crabs ofsimilar ages between sites and/or dates.
A simple model relating habitat features to a diapause egg bank
Limnology and Oceanography, 2006
As a way to escape from adverse conditions, many zooplankton populations produce diapausing eggs that accumulate in the sediments and hatch when suitable environmental conditions are restored. While buried in the sediment, diapausing eggs may be affected by several processes (i.e., production, hatching, deterioration, and loss). We present a simple mathematical model for the dynamics of diapausing eggs in the sediment. We were mainly inspired by the model organism Brachionus plicatilis, a cyclical parthenogen rotifer, but the model is applicable to other zooplankters. Three diapausing egg categories are used as variables in our model: (1) healthy-looking eggs, assumed to represent the fraction of viable eggs;
PloS one, 2017
Fishing is a major source of human impact, reducing density and size of a wide range of exploited species in comparison to areas exhibiting strong regulations (no-take and partially protected areas, including Territorial Use Rights for Fisheries, TURFs). Since size and density might have important consequences on reproduction, and therefore natural re-seeding, we monitored adult size, density and potential fecundity of the keyhole limpet (Fissurella latimarginata) and the red sea urchin (Loxechinus albus) in areas under two fishing regimes (TURFs and Open Access Areas, OAAs). Analyzing the distribution of suitable habitats, we predict spatial patterns of potential egg production, to identify reproductive hotspots along the central coast of Chile. The current system of TURFs in central Chile showed higher potential egg production of F. latimarginata and of L. albus than expected under a complete OAAs scenario (67 and 52% respectively). Potential egg production showed more than a twof...
Journal of Coastal Research
We used results from a survey of horseshoe crab reproductive activity that was conducted in 1999 throughout Delaware Bay to examine the relationship between estimates of spawning females and egg deposition and analyze how that relationship varies with geography, time within a spawning season, beach morphology, and wave energy. We found that beach morphology and wave energy interacted with density of spawning females to explain variation in the density and distribution of eggs and larvae. For example, the quantity of eggs in surface sediment ii.e., eggs that are potentially available to foraging shorebirds) was associated with the density of spawning females, beach morphology, and wave energy. The association between beach morphology and live eggs in surface sediment was strong especially in late May (Percent Reduction in Error = 860/0 from regression tree model) where egg density was an order of magnitude higher on beaches <15 m wide (3.38*10 5 m :"; 900/0 CI: 2.29*10 5 , 4.47*10 5) compared to wider beaches (1.49* 10 4 rn:"; 90% CI: 4.47* 10 3 , 2.53* 10 4). Results also indicate that, among bay-front beaches, horseshoe crabs prefer to spawn on narrow beaches, possibly because of reduced wave energy. At peak periods of spawning activity, density of spawning females was inversely related to foreshore width on mid-latitude beaches within Delaware Bay (t =-2.68, 7 df, p = 0.03). Because the distribution of eggs across the foreshore varied with beach morphology and widened as the spawning season progressed, methods used to sample eggs need to be robust to variation in beach morphology and applicable regardless of when the samples are taken. Because beach morphology and wave energy were associated with the quantity of eggs in surface sediment, certain beach types may be critical to the conservation of shorebird foraging habitat.
Journal of Crustacean Biology, 2012
The reproductive traits of three coastal grapsoid crabs from the southwestern Atlantic, Neohelice granulata (Dana, 1851), Cyrtograpsus angulatus Dana, 1851 and C. altimanus Rathbun, 1914, were compared under the hypothesis that more energy is diverted to maintenance (and less to reproduction) in the upper intertidal and/or in estuaries than in the lower marine intertidal or subtidal, in order to cope with the harsh, and frequently variable, environmental conditions of semiterrestrial and brackish water habitats. Each species occupies a different habitat along intertidal, as well as estuarine gradients: N. granulata lives in the upper and middle intertidal of salt marshes and mud flats, especially in estuarine waters; C. angulatus lives in the low intertidal and subtidal of estuarine and marine habitats, and C. altimanus is predominantly an intertidal and subtidal marine crab. Results suggested that energy demands imposed by the harsh environmental conditions of the estuarine and semiterrestrial habitats resulted in less energy available for reproduction in N. granulata, evidenced by a shorter breeding season, a reduced reproductive output per clutch and an increased clutch interval. The opposite occurred with C. altimanus: less energy was necessary to cope with the stable marine water, allowing the presence of a long breeding season, a higher reproductive output per clutch and a very short clutch interval. Differences observed between marine and estuarine populations of C. angulatus are comparable with differences between C. altimanus, and N. granulata.
Integrative and Comparative Biology, 2006
Synopsis Egg size is a critical life-history trait because it can profoundly influence offspring fitness and the number of offspring that can be produced. Recently, interest has grown in how egg size influences fertilization rate and in turn how sperm availability might influence the evolution of egg size among broadcast-spawning marine invertebrates. In this article I review the empirical evidence on the ways in which egg size and egg accessory structures influence fertilization and theoretical models of the ways sperm availability might influence the evolution of egg size. Evidence suggests that egg size does influence the collision frequency with sperm, and models suggest that sperm availability can influence selection on egg size. Sperm availability appears to be one of the several factors that influence optimal egg size in broadcast-spawning marine invertebrates.
REPRODUCTION ON THE EDGE: LARGE-SCALE PATTERNS OF INDIVIDUAL PERFORMANCE IN A MARINE INVERTEBRATE
Ecology, 2007
Reproductive output is a central attribute of life history, providing a measure of individual and population performance. The fields of ecology, biogeography, and evolutionary biology take disparate approaches in addressing spatial variation in reproduction, and thus we lack clear predictions for how reproductive output should vary geographically. We empirically investigate these contrasting theoretical approaches by determining geographic patterns in reproductive output for intertidal populations of the purple sea urchin, Strongylocentrotus purpuratus, at 15 sites spanning a large geographic distance (98 span of latitude) from central California, USA, to Baja California, Mexico. Contrary to predictions from biogeography, some of the highest values of reproductive output are at sites near the species' southern range boundary. Additionally, sea urchins do not exhibit a latitudinal gradient in reproduction, but rather show considerable mesoscale variation in reproductive output. Spatial analyses reveal that this variation is correlated with coastal topographic features that are known to influence the pattern of nearshore nutrient flux and circulation. We hypothesize that urchins' reproductive output may be driven by the spatial distribution of their food supply, drift macroalgae, the abundance of which is influenced by both nutrient supply and alongshore transport processes that are coupled to topographic features. Large-scale studies such as this provide valuable insight into the causes of species' range limits, population connectivity, habitat reserve design, and forecasting the effects of climate change on species' distributions.