Emergent behavior that arises from a mass effect is one of the most striking aspects of collective animal groups. Investigating such behavior would be important in order to understand how individuals ...interact with their neighbors. Although there are many experiments that have used collective animals to investigate social learning or conflict between individuals and society such as that between a fish and a school, reports on mass effects are rare. In this study, we show that a swarm of soldier crabs could spontaneously enter a water pool, which are usually avoided, by forming densely populated part of a swarm at the edge of the water pool. Moreover, we show that the observed behavior can be explained by the model of collective behavior based on inherent noise that is individuals' different velocities in a directed group. Our results suggest that inherent noise, which is widely seen in collective animals, can contribute to formation and/or maintenance of a swarm and that the dense swarm can enter the pool by means of enhanced inherent noise.
Direct and indirect human impacts on coastal ecosystems have increased over the last several centuries, leading to unprecedented degradation of coastal habitats and loss of ecological services. Here ...we document a two-century temporal disparity between salt marsh accretion and subsequent loss to indirect human impacts. Field surveys, manipulative experiments and GIS analyses reveal that crab burrowing weakens the marsh peat base and facilitates further burrowing, leading to bank calving, disruption of marsh accretion, and a loss of over two centuries of sequestered carbon from the marsh edge in only three decades. Analogous temporal disparities exist in other systems and are a largely unrecognized obstacle in attaining sustainable ecosystem services in an increasingly human impacted world. In light of the growing threat of indirect impacts worldwide and despite uncertainties in the fate of lost carbon, we suggest that estimates of carbon emissions based only on direct human impacts may significantly underestimate total anthropogenic carbon emissions.
Salt marsh die-off is a Western Atlantic conservation problem that has recently spread into Narragansett Bay, Rhode Island, USA. It has been hypothesized to be driven by: 1) eutrophication decreasing ...plant investment into belowground biomass causing plant collapse, 2) boat wakes eroding creek banks, 3) pollution or disease affecting plant health, 4) substrate hardness controlling herbivorous crab distributions and 5) trophic dysfunction releasing herbivorous crabs from predator control. To distinguish between these hypotheses we quantified these variables at 14 Narragansett Bay salt marshes where die-off intensity ranged from <5% to nearly 98%. Nitrogen availability, wave intensity and plant growth did not explain any variation in die-off. Herbivory explained 73% of inter-site variation in die-off and predator control of herbivores and substrate hardness also varied significantly with die-off. This suggests that salt marsh die-off is being largely driven by intense herbivory via the release of herbivorous crabs from predator control. Our results and those from other marsh systems suggest that consumer control may not simply be a factor to consider in marsh conservation, but with widespread predator depletion impacting near shore habitats globally, trophic dysfunction and runaway consumption may be the largest and most urgent management challenge for salt marsh conservation.
We outline a framework for evaluating scientific evidence of sentience, focusing on pain experience. It includes eight neural and cognitive-behavioural criteria, with confidence levels for each ...criterion reflecting the reliability and quality of the evidence. We outline the rationale for each criterion and apply our framework to a controversial sentience candidate: decapod crustaceans. We have either high or very high confidence that true crabs (infraorder Brachyura) satisfy five criteria, amounting to strong evidence of sentience. Moreover, we have high confidence that both anomuran crabs (infraorder Anomura) and astacid lobsters/crayfish (infraorder Astacidea) meet three criteria-substantial evidence of sentience. The case is, as yet, weaker for other infraorders, such as penaeid shrimps, highlighting important research gaps. Having demonstrated our framework's application to decapod crustaceans, we hope that future research will apply it to other taxa.
Shrimp farming has become increasingly important in the aquaculture industry of Peninsular Malaysia. The culture areas for shrimp continue to expand with a view to achieve higher output and ...generating more export earnings. This article uses farm level data gathered from Perak and Johor States of Peninsular Malaysia, to investigate the technical efficiency of brackish water shrimp farms. Stochastic frontier production analysis is applied to examine the determinants of frontier production function and the technical efficiency of pond shrimp farming system. On average, 65% of the sampled shrimp farms are technically efficient. The results suggest high degrees of technical inefficiency exist among the shrimp farmers. This implies that, great potential exists to increase shrimp production through improved efficiency in farm management in Peninsular Malaysia. Initiatives to undertake extension programmes at the farm level are needed to help shrimp farmers, in utilizing their resources more efficiently in order to substantially enhance their shrimp production.
Macroinvertebrate shredders may have been overlooked in tropical streams due to the geographical bias of early studies, methodological limitations, and the complex influences of local-scale factors. ...While shredders seem to be scarce in most oceanic island streams, we here test if they are abundant in a continental island. Gut content analyses of benthic macroinvertebrates were used to identify shredding taxa in streams located in different types of forest in Gorgona Island (Tropical Eastern Pacific). General dietary overlap (GO) was quantified and relative biomass, relative frequency and the leaf litter percentage in the guts were used to establish the relative importance of each taxon in the shredding guild. Although crabs, shrimps, aquatic insects and semiaquatic-cockroaches coexisted in Gorgona Island, the latter were the most important leaf litter shredders in terms of biomass.Original Abstract: Existe la posibilidad de que los macroinvertebrados fragmentadores hayan sido subvalorados en las quebradas tropicales debido al sesgo geografico de los estudios realizados, a limitaciones metodicas y a la influencia de factores de escala local. A pesar de que los fragmentadores son escasos en las quebradas de islas oceanicas, hipotetizamos que son abundantes en Isla Gorgona. Los analisis de contenidos estomacales de estos organismos se usaron para identificar los taxones fragmentadores colectados en quebradas con diferentes tipos de bosque. Se cuantificaron el indice general de sobreposicion dietaria (GO por su siglas en ingles), y el indice de valor de importancia de cada taxon en el gremio (con base en biomasa relativa, frecuencia relativa y proporcion de tejido vegetal en los contenidos estomacales). El arreglo espacial de cada taxon y el del gremio entre quebradas (i.e., contagioso o aleatorio) se determino a partir de varios indices. Se identificaron 31 fragmentadores, los cuales se dividieron en especialistas (14 taxones), generalistas (10) y colectores-fragmentadores (7). Hubo un GO completo del gremio (0.75, p<0.001). Debido a su alta contribucion de biomasa y de abundancia al gremio, y a la elevada proporcion de tejido vegetal consumido, las cucarachas (Epilampra) fueron los fragmentadores-especialistas mas representativos, superiores incluso a camarones y cangrejos. El camaron Potimirin fue el segundo taxon mas importante seguido por el diptero Stenochironomus. Entre los insectos acuaticos, otros taxones de importancia secundaria fueron Leptohyphes(Ephemeroptera), Macrelmis, Anchytarsus y Tetraglosa(Coleoptera). Diez taxones mostraron un patron espacial de contagio, y 21 se organizaron aleatoriamente, al igual que los recursos (i.e., "paquetes" de hojarasca). Aunque el gremio se organizo contagiosamente, estos resultados pudieron estar altamente influenciados por los taxones con distribucion del mismo tipo. No se encontraron correlaciones significantes entre la abundancia media, la riqueza y la biomasa media con ninguna de las variables ambientales. Tres factores explicaron la alta riqueza y la abundancia de los fragmentadores en Isla Gorgona: (1) el origen continental, (2) su proximidad al continente (35km), y (3) la alta diversidad y disponibilidad de hojarasca y de desechos de madera dentro de las quebradas. Aunque cangrejos, camarones, insectos acuaticos y cucarachas-semiacuaticas coexistieron en la isla, estas ultimas fueron, en terminos de biomasa, los fragmentadores mas importantes.
This research was conducted to evaluate the efficiency level of shrimp poly-culture farms by using Data Envelopment Analysis. It also identified factors affecting the inefficiencies of shrimp ...poly-culture farms using Tobit regression model. The empirical results indicated that, the mean of Technical, Allocative and Economic Efficiency were at 84.01%, 64.16%, 55.32%, respectively, hence, there is a substantial room for improving the efficiency. DEA results recommended that, inefficient farms need to minimize overfeeding of stocks in order to avoid the accumulation of uneaten feeds that further contributes to water pollution. The optimal stocking density ratio should be 8.15 for shrimps, 1.59 for crabs and 2.46 for fish per square meter of pond. The results also showed the presence of scale inefficiency. Smaller farms tend to be more efficient than larger farms. The optimal farm size should be less than 0.5 hectares. The results of Tobit regression model suggested that, farm personal characteristics, farm ability to access to institutions, and water environment have significant effect on the efficiency of farms.
The use of indirect estimates of ghost-crab populations to assess beach disturbance has several advantages, including non-destructiveness, ease and low cost, although this strategy may add some ...degree of noise to estimates of population parameters. Resolution of these shortcomings may allow wider use of these populations as an indicator of differences in quality among beaches. This study analyzed to what extent the number of crab burrows may diverge from the number of animals, considering beach morphology, burrow depth and signs of occupation as contributing factors or indicators of a higher or lower occupation rate. We estimated the occupation rate of crabs in burrows on nine low-use beaches, which were previously categorized as dissipative, intermediate or reflexive. Three random 2-m-wide transects were laid perpendicular to the shoreline, where burrows were counted and excavated to search for crabs. The depth and signs of recent activity around the burrows were also recorded. The occupation rate differed on the different beaches, but morphodynamics was not identified as a grouping factor. A considerable number of burrows that lacked signs of recent activity proved to be occupied, and the proportions of these burrows also differed among beaches. Virtually all burrows less than 10 cm deep were unoccupied; the occupation rate tended to increase gradually to a burrow depth of 20-35 cm. Other methods (water, smoke, and traps) were applied to measure the effectiveness of excavating as a method for burrow counts. Traps and excavation proved to be the best methods. These observations illustrate the possible degree of unreliability of comparisons of beaches based on indirect measures. Combining burrow depth assessment with surrounding signs of occupation proved to be a useful tool to minimize biases.
Cave shrimps of the Typhlatya genus are common and widespread in fresh, brackish and marine groundwater throughout the Yucatan Peninsula (Mexico). These species are ideal models to test niche ...partitioning within sympatric species in oligotrophic systems. Nevertheless, their food sources remain unidentified, and despite their frequency and functional importance, distribution and abundance patterns of these species within caves have not been fully recognized. Here, we describe the abundance of three Typhlatya species in different temporal and spatial scales, investigate changes in water conditions, and potential sources of carbon as an indication of food origin. Species composition and abundance varied markedly in space and time revealing patterns that differed from one system to another and in relation to environmental parameters. Isotope analysis showed that each species reflects a particular δ
C and Δ
C fingerprint, suggesting they feed in different proportions from the available carbon sources. Overall, our findings suggest a niche partitioning of habitat and feeding sources amongst the three Typhlatya species investigated, where environmental characteristics and physiological differences could play an important role governing their distribution patterns.
The paper addresses the phylogeny and classification of the hydrothermal vent shrimp family Alvinocarididae. Two morphological cladistic analyses were carried out, which use all 31 recognized species ...of Alvinocarididae as terminal taxa. As outgroups, two species were included, both representing major caridean clades: Acanthephyra purpurea (Acanthephyridae) and Alpheus echiurophilus (Alpheidae). For additional support of the clades we utilised available data on mitochondrial Cytochrome c Oxidase I gene (CO1) and 16S ribosomal markers. Both morphological and molecular methods resulted in similar tree topologies and nearly identical clades. We consider these clades as evolutionary units and thus erect two new subfamilies: Rimicaridinae (Alvinocaridinides, Manuscaris, Opaepele, Shinkaicaris, Rimicaris), Alvinocaridinae (Alvinocaris), whilst recognising Mirocaridinae (with genera Mirocaris and Nautilocaris) at subfamily level. One genus, Keldyshicaris could not be assigned to any subfamily and is thus left as incertae sedis. The monophyly of Alvinocardinae was supported by morphological data, but not supported by molecular data (two analyses); the monophyly of all subfamilies was supported both by morphological and molecular data. Chorocaris is herein synonymized with Rimicaris, whilst Opaepele vavilovi is herein transferred to a new genus Keldyshicaris. Morphological trends within Alvinocarididae are discussed and short biogeographical remarks are given. We provide emended diagnoses for all subfamilies and genera along with keys to all recognized species.
PDF
