Stout Razor Clam Research Articles

Biochemical adaptations of the stout razor clam (Tagelus plebeius) to changes in oxygen availability: resilience in a changing world?

Climate change is producing sea level rise and deoxygenation of the ocean, altering estuaries and coastal areas. Changes in oxygen availability are expected to have consequences on the physiological fitness of intertidal species. In this work we analyze the coping response of the intertidal stout razor clam (Tagelus plebeius (Lightfoot, 1786)) to extreme environmental changes in oxygen concentration. Their biochemical responses to normoxia, hypoxia, and hyperoxia transition at different intertidal level (low–high) were measured through an in situ transplant experiment. The high intertidal level negatively affected the analyzed traits of the T. plebeius populations. The differences in reactive oxygen species production, total oxyradical scavenger capacities, and catalase activity also suggested more stressful conditions at the high level where long-term hypoxia periods occur. Both hypoxia and re-oxygenation provoked re-adjustments in the antioxidant responses and higher lipid oxidative damage (normoxia < hypoxia < re-oxygenation). The observed responses in transplanted clams at the opposite intertidal level suggested the potential acclimation of T. plebeius to cope with new environmental conditions. These findings are discussed within a global changing context where both increasing deoxygenation conditions and sea level rise are predicted to be exacerbated in the area driven by climate change.

Growth changes of the stout razor clam Tagelus plebeius (Lightfoot, 1786) under different salinities in SW Atlantic estuaries

Estuarine abiotic characteristics vary with tidal variations and fresh water input, both driven by climatic conditions and often cyclical climatic events. Estuaries are very productive and bivalves often represent a substantial proportion of the biomass with important ecological role. Salinity fluctuation is often a key environmental factor affecting bivalves shell growth and individual condition index (CI), parameters that in turn can be used to show the quality of the environment for one population. The stout razor clam Tagelus plebeius is an euryhaline filter-feeder species that inhabits sandy-silt tidal flats within a wide salinity range. The objective of this study was to evaluate, by survey sampling and in situ transplant experiments among sites with different salinity, whether shell growth and CI of T. plebeius vary with the salinity regime. We hypothesized a higher growth and CI related to the intermediate salinity. Clams and abiotic parameters were sampled in three estuaries of the northern Argentinian coast with different salinity regimes (Bahía Samborombón (36°19′S), Mar Chiquita coastal lagoon (37°32′S) and Bahía Blanca (38° 47′S)) and in three sites along the salinity gradient of the Mar Chiquita coastal lagoon where the manipulative experiments were also conducted. Shells were more elongated in sites with lower salinity; but the growth rate (k) and the CI were higher in sites with intermediate salinity. Furthermore, clams transplanted from intermediate salinity sites to those with higher or lower salinity showed a disadvantage in shell growth. Considering the scenario of climatic-driven salinity changes in these estuaries and given that T. plebeius is the only native bivalve species in those intertidal zones, having a relevant ecological role and conspicuous fossil presence in Holocene outcrops, our results highlight the relevance of this clam as a valuable target for future studies on conservation biology and paleobiology.

Impacts of habitat, predators, recruitment, and disease on soft-shell clams Mya arenaria and stout razor clams Tagelus plebeius in Chesapeake Bay

Soft-shelled clams, Mya arenaria, and razor clams, Tagelus plebeius, in Chesapeake Bay have been in decline since the 1970s, with severe declines since the early 1990s. These declines are likely caused by multiple factors including warming, predation, habitat loss, recruitment limitation, disease, and harvesting. A bivalve survey was conducted in Chesapeake Bay to examine influential factors on bivalve populations, focusing on predation (crab, fish, and cownose rays), habitat type (mud, sand, gravel, shell, or seagrass), environment (temperature, salinity, and dissolved oxygen), recruitment, and disease. M. arenaria and T. plebeius were found more often in more-complex habitats such as seagrass or shell than any other habitat. Pulses in bivalve density associated with recruitment were attenuated through the summer and fall when predators are most active, indicating that predators likely influence temporal dynamics in these species. Mya arenaria, which is near the southern extent of its range in Chesapeake Bay, was negatively associated with high water temperatures. Recruitment of M. arenaria in Rhode River, MD, declined steadily between 1980 and 2016. Infection by the parasitic protist Perkinsus sp. was associated with stressful environmental conditions, bivalve size, and environmental preferences of Perkinsus sp, but was not associated with bivalve densities. It is likely that habitat loss, low recruitment, and predators are major factors keeping T. plebeius and M. arenaria at low densities in Chesapeake Bay. Persistence at low densities may be facilitated by complex habitats, whereas further reductions in habitats such as seagrass could result in local extinction of these important bivalve species.

Effects of the Razor Clam Tagelus plebeius on the Fate of Petroleum Hydrocarbons: A Mesocosm Experiment.

The relationship between organisms and contaminants may be a two-way interaction: contaminants affecting the biota and the biota affecting the environmental fate and distribution of the contaminants. This may be especially so for sediment-dwelling organisms, because their burrowing and feeding can drastically influence sediment characteristics. The present study looked at the influence of the suspension-feeding stout razor clam Tagelus plebeius on the distribution of crude oil and pyrene in greenhouse mesocosm experiments. Water column turbidity and sediment redox also were monitored during the 15- to 30-day exposures to provide information on the influence of hydrocarbons and the razor clams on environmental conditions. For the experiment with crude oil, sediment was taken from the mesocosms at the end of the experiment, and the hydrocarbon-degradation potential was assessed in incubations with 14C-naphthalene. The experiments used four treatments: hydrocarbons present/absent and razor clams present/absent. Hydrocarbon dosing levels were relatively low (1mL of oil or 30mg of pyrene per mesocosm with 22L of natural sediment and 11L of seawater). The presence of the razor clams resulted in hydrocarbon concentrations at the sediment surface being 25% lower than in mesocosms without clams. No consistent effects were noted for polycyclic aromatic hydrocarbon (PAH) concentrations in the water column or in subsurface sediment. The naphthalene-degradation potential was elevated for sediment from mesocosms dosed with oil, but the presence of the clams did not affect this potential. The presence of the razor clams resulted in a lowering of water column turbidity, but no effect on sediment redox. The hydrocarbon addition had no effect on turbidity, but sediment redox was lowered. While results show that the presence of the razor clams resulted in a loss of hydrocarbons from the surface sediment, the other results do not provide a clear picture of the underlying mechanisms and the fate of the PAHs lost from the sediment surface. We hypothesize that the loss of surface sediment PAHs was due to burial of surface sediment and possibly bioaccumulation by the clams. While additional research is needed for further insights into underlying mechanisms, the present work demonstrates that the presence of sediment-burrowing suspension feeders decreases hydrocarbon levels in surface sediment. This means that assessments of the impact of an oil spill should pay attention to effects on these organisms and to their influence on the fate and distribution of the spilled oil.

Distribution pattern, density and growth of the stout razor clam Tagelus plebeius in a South-west Atlantic estuarine system

The population biology of the stout razor clam Tagelus plebeius is poorly understood, despite the species' current wide distribution, and the potential use of its Holocene shell deposits to infer past environmental and ecological conditions. This study investigates distribution and growth pattern of T. plebeius in the south-western Atlantic Mar Chiquita Coastal lagoon (37°32′S 57°19′W), Argentina. The population includes the oldest individuals (up to 27 years) reported so far with shell length up to 77.9 mm. A von Bertalanffy model with L∞ = 67.60 mm (95% CI = 64.55; 70.64), k = 0.181 year−1 (CI = 0.142; 0.218), and t0 = −0.77 (CI = −1.46; −0.08) best described their individual growth for the whole population. The higher density, growth rate k, t0 and maximum age and lower L∞ were in the low intertidal rather than in the medium intertidal, but there were no differences in density and age between medium and high intertidal. Given the results and the current knowledge on the effects of different factors influencing this species, we conclude that the distribution pattern and shell growth observed in our study reflect a response to metabolic necessities in combination with a strong influence of biological interactions.

Interaction between a mobile and a sessile species in SW Atlantic mudflats: Lack of negative effects of the mud crab Cyrtograpsus angulatus Dana, 1851 on filtration rate and growth of the infaunal clam Tagelus plebeius (Lightfoot, 1786)

Biogenic modifications of benthic environment by organism's activities like feeding, burrowing or excretion have in general negative implications for cohabiting sessile infauna, especially for suspension-feeders. However, the outcome of these interactions depends on several biological and physical characteristics and thus, it is not easily predictable in soft bottom environments. The stout razor clam Tagelus plebeius, an estuarine, infaunal and sessile filter feeder species, coexists in Mar Chiquita coastal lagoon (Argentina, 37° 32′S, 57° 19′W) with the mud crab Cyrtograpsus angulatus, a very mobile benthic consumer. Due to the intense crab activity and consequent habitat transformation, we predicted negative effects on clams' filtration rate and their growth. However, an inclusion experiment showed that T. plebeius filtration rate was higher in enclosures when crabs were present responding to enhanced turbidity and chlorophyll a. Additionally, another experiment showed that mean condition index as well as mean shell growth increment of clams was not negatively affected by crabs, although maximum values of shell growth increments (mm) were smaller in crab inclusions. Our findings suggest that the clams can exploit the increased food availability (i.e., Chl a) generated by resuspension and are also not affected by the disturbance that crabs can make over sediment surface. In conclusion, contrary to the generalized outcome proposed for this kind of interaction, crabs do not have a negative effect on T. plebeius.

Combined engineering effects of clams and crabs on infaunal assemblages and food availability in intertidal systems

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 540:57-71 (2015) - DOI: https://doi.org/10.3354/meps11478 Combined engineering effects of clams and crabs on infaunal assemblages and food availability in intertidal systems M. Fernanda Alvarez1,2,*, Mariana Addino1,3, Oscar Iribarne1, Florencia Botto1 1Laboratorio de Ecología, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Mar del Plata (UNMdP), Dean Funes 3350 - CP 7600, Argentina 2Present address: Laboratorio Cuenca del Salado, Instituto de Limnología “Dr. Raúl A. Ringuelet” (ILPLA-CONICET), Universidad Nacional de La Plata (UNLP), Boulevar 120 no. 1460- CP 1900, Argentina 3Present address: Grupo de Ecología y Paleoecología de Ambientes Acuáticos Continentales (IIMyC-CONICET-UNMdP), Dean Funes 3350 - CP 7600, Argentina *Corresponding author: feralvarez@ilpla.edu.ar ABSTRACT: In soft sediments, ecosystem engineers (EEs) may play key roles in modifying habitats and therefore affecting bottom-assemblage species. In the southwestern Atlantic mud flats, 2 EEs coexist: the stout razor clam Tagelus plebeius and the burrowing crab Neohelice (Chasmagnathus) granulata. Clams create small depressions (i.e. millimeters), while crabs build large burrows (i.e. centimeters) generating crab beds covering many hectares. We hypothesized that these differences in the bioturbation scale may have different consequences for infaunal assemblages. We found that (1) microscale sediment-surface heterogeneities created by clams (e.g. holes and surrounding depressions) were related to higher organic-matter content and microphytobenthic biomass (measured as chlorophyll a), (2) abundances of meiofaunal groups (copepods, ostracods, and nematodes) were higher in clam holes than outside at all tidal levels, and (3) habitats with a more heterogeneous structure—such as clam holes inside a crab bed—had a higher food availability and an abundance of several meiofaunal groups (e.g. ostracods, and principally nematodes). Large-scale bioturbation (crab-bed formation) also affected primary producers, infaunal assemblages, and clam distribution, because at the highest intertidal levels clams were absent outside the crab beds. Our results thus demonstrate the differential effects of 2 contrasting EEs on the organization of soft-bottom communities and the key role of microheterogeneities in adding specific structures to already modified systems on a larger scale. KEY WORDS: Ecosystem engineers · Habitat structure · Infaunal assemblages · Clams · Crabs Full text in pdf format PreviousNextCite this article as: Alvarez MF, Addino M, Iribarne O, Botto F (2015) Combined engineering effects of clams and crabs on infaunal assemblages and food availability in intertidal systems. Mar Ecol Prog Ser 540:57-71. https://doi.org/10.3354/meps11478 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 540. Online publication date: November 26, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Effect of Spartina alterniflora Loisel, 1807 on growth of the stout razor clam Tagelus plebeius (Lightfoot, 1786) in a SW Atlantic estuary

Aquatic organisms that produce epibenthic structures such as saltmarsh plants play key roles in habitat functioning through their ecosystem engineering effects. Intertidal Spartina species are well known for modifying tidal hydrodynamic and sediment processes, affecting cohabiting infaunal organisms. The stout razor clam Tagelus plebeius is an infaunal filter-feeding species that inhabits a broad range of mudflats (MF) and Spartina saltmarshes (SM) along the American Atlantic coast. Through descriptive and experimental approaches conducted at the Bahía Blanca estuary (Argentina, 38°47′S, 62° 20′W), we evaluated ecosystem engineer effects of Spartina alterniflora (due to changes in sediment and water characteristics) on somatic and shell growth of T. plebeius. Comparison of bulk sediment parameters indicated that the sediment is more easily eroded in the SM than in the MF, but softer in the latest. In addition, food supply for clams (i.e., total particulate organic matter) was higher in the MF although food quality (i.e., percentage of organic matter in the water column) was in general higher in SM. Shell growth was higher but clam condition index (CI) was lower in the MF, and the opposite pattern was found in the SM. These results represent an uncoupling between shell and somatic growth with a positive effect of S. alterniflora on the CI of clams. Nevertheless, results of field experiments manipulating stems and roots of plants separately suggested that the effect of Spartina on clam's CI was not due to the structural changes generated by plant presence itself, although a better food quality in the SM may be related to the larger clams CI.

Growth, mortality, and reproduction of Tagelus plebeius (Bivalvia: Solecurtidae) in Southeast Brazil

Tagelus plebeius (Lightfoot, 1786) is a stout razor clam that is economically exploited in several countries, including several local fisheries along the Brazilian coast. Despite its wide distribution and economic importance, there are few studies that have examined the population biology of this species. This study aimed to improve the current knowledge about the biology of T. plebeius by investigating its growth and mortality on a subtropical sandy beach in Southeast Brazil over a 1-year period. In addition, the reproduction of T. plebeius was analyzed through qualitative and quantitative histological analyses during the last 7 months of the study. The parameters of the von Bertalanffy growth function were estimated to be L ∞ = 74.14 mm, K = 0.52 year−1, C = 0.47, and WP = 0.94. The instantaneous mortality rate (Z) was 2.16 year−1, and the life span was 2.58 years. We confirmed variations (H = 651.35; P < 0.05) in the shell length over the months of the study, and the recruitment was higher—but still low—in summer. Four cohorts were observed in the distribution of shell length frequencies. The sex ratio of the population was 1:1 during the study period, and a synchronism in gonadal development and spawning was found between males and females. The high mortality (Z) and low recruitment rates can be interpreted as reflecting that the population of T. plebeius is under a low restoration process and could be an indication that this species has an endangered status in the study area.

Reproductive cycle of Tagelus plebeius (Mollusca: Bivalvia) in the estuary of the Cachoeira River, Ilhéus, Bahia, Brazil

This study characterized the reproductive cycle of the stout razor clam Tagelus plebeius in the estuary of the Cachoeira River, Ilhéus, Bahia, northeastern Brazil. Samples of 20 animals per collection were taken biweekly from August 2005 to August 2006. The 480 specimens were measured on the antero-posterior axis (length) and then removed from the shell. After macroscopic analysis, the gonads were fixed in Davidson's solution, processed by routine histology and stained by Harris hematoxylin and eosin. The gonads of both males and females appeared milky white, without sexual dimorphism. Microscopic analyses indicated a M: F ratio of 1.06: 1 and continuous reproduction of T. plebeius in the region. The period from August to October showed the most intense spawning. This study provides another example of continuous reproduction of bivalves in tropical waters, and because this species is a heavily exploited fishery resource in the region, it draws attention to the need for a management plan aimed at reducing harvests.

Population biology and secondary production of the stout razor clam Tagelus plebeius (Bivalvia, Solecurtidae) on a sandflat in southeastern Brazil

The population biology and production of the stout razor clam Tagelus plebeius Lightfoot, 1786 were investigated on an intertidal sandflat on the southeast coast of Brazil (Enseada Beach, Sao Sebastiao, state of Sao Paulo) between April 1997 and April 1998. Two rectangular sites of 50 X 10 m parallel to the waterline were established, site A (upper intertidal level) and site B (middle intertidal level), where the samples were taken in an 0.5 x 0.5 m quadrat. High abundances were recorded in winter and spring, with no significant differences between the sites. The high bivalve abundances were related to the presence of very fine homogeneous sediment with low salinities. Tagelus plebeius had negative allometric growth, characteristic of deep burrowers for the relationships DM/SL and AFDM/SL. Parameters of the modified von Bertalanffy growth function were: L∞ = 67.01 mm, K = 1.73 year-1, t0 = -0.11 year, C = 0.43, WP = 0.96. The instantaneous mortality (Z) was 3.12 year-1, relatively high in comparison to other tropical bivalve populations. Secondary production was 1.53 g AFDM m-2 year-1, with a P/B ratio reaching 1.37 year-1. This high turnover ratio (P/B) was related to a rapid population replacement, connected with the short life span and high mortality of the species.

Presence and histopathological effects of the Parvatrema sp. (Digenea, Gymnophallidae) in the stout razor clam Tagelus plebeius (Bivalvia, Psammobiidae)

The stout razor clam Tagelus plebeius (Bivalvia, Psammobiidae) has a wide geographic distribution range, including the Brazilian coasts from the northeast (Alagoas) to the south (Santa Catarina). In March 2008, an episode of mass T. plebeius mortality (70%) occurred in an intertidal bed at The Pontal da Daniela, State of Santa Catarina, Brazil. We report here high prevalences (to 100%) of the trematode parasite Parvatrema sp. Cable, 1953 (Digenea, Gymnophallidae) infecting T. plebeius at high intensities. We describe the gymnophalid, echinostomatid and unidentified metacercariae parasites infecting the clam and the host reactions elicited by them. The use of special diagnostic techniques such as Ray’s fluid thioglycollate medium (RFTM) and PCR assays to detect Perkinsus sp. pathogens, hemolymph cytology, and histopathological examinations did not show Perkinsus sp. infections, microcell infections, or neoplastic conditions. However, neither infections or pathology caused by trematode parasites; nor any other pathological condition could be uniquely correlated with the mortality event. A coincident flash flood might have contributed to cause the mortality episode. This is the first report of the Parvatrema sp. metacercariae larvae infecting the stout razor clam T. plebeius from Brazil.

Tissue reaction of Tagelus plebeius (Bivalvia: Psammobiidae) against larval digeneans in mixohaline habitats connected to the south-western Atlantic

This paper describes the organism–organism relationship between a bivalve host and larval digeneans. The studied population of the stout razor clam Tagelus plebeius from the mixohaline Mar Chiquita lagoon (37° 32′S 57° 19′W) showed 100% of prevalence of infection by a larval digenean (metacercaria) of the family Gymnophallidae. The larvae occupied the extrapallial space just below the hinge of the bivalve. The tissue reaction against larval digeneans by T. plebeius consisted of hyperplasia and metaplasia of the outer layer of the mantle epithelium adjacent to parasites, forming an invagination to generate a sac that surrounded gymnophallid larvae. According to the intensity of infection, each sac progressively enlarged to harbour a variable number of larvae. In highly infected clams, a great number of sacs are formed. Eventually, the older sacs containing larvae may become closed, losing their communication with the extrapallial space and sinking into the dorsal part of the visceral mass. Larvae within sacs grow and remain alive until they reach an appropriate definitive bird vertebrate host. Older lesions commonly showed remains of dead larvae which had undergone resorption. As a result, an orange to brownish amorphous material accumulated in the space once occupied by the larvae leaving conspicuous orange marks on the inner surface of the valves. In some cases, calcifications in the form of pearls or blisters were observed.

Perkinsus chesapeaki in stout razor clams Tagelus plebeius from Delaware Bay

Perkinsus chesapeaki is reported from stout razor clams Tagelus plebeius in Delaware Bay, extending the known range of P. chesapeaki north of Chesapeake Bay. P. marinus, which causes dermo disease, is prevalent in cultured and wild oysters at this site, but was not detected in T. plebeius. Evidence for the presence of disseminated neoplasia, also reported from Chesapeake Bay, was equivocal. Although P. chesapeaki infections were associated with mortality events, light infection intensities and a general lack of histopathological evidence of disease limit inferences about a causal relationship. A comparison of Ray's fluid thioglycollate medium (RFTM)-based and PCR-based detection assays highlight differences in detection capabilities related to the quantity and type of tissue processed rather than assay sensitivity per se, a point that should be considered when surveying populations for disease prevalence. Investigators are further cautioned to use care when applying and interpreting diagnostic assays when used with novel species.

PARASITES OF THE STOUT RAZOR CLAM TAGELUS PLEBEIUS (PSAMMOBIIDAE) FROM THE SOUTHWESTERN ATLANTIC OCEAN

This work describes the parasites and their respective pathologies in the stout razor clam, Tagelus plebeius (Lightfoot, 1786) (Psammobiidae) from Argentinean coasts. It represents the first report about a histopathological survey for these species in the Southwestern Atlantic. Specimens of T. plebeius were collected at Mar Chiquita coastal lagoon (37°46′S, 57°27′W) (n = 104 dissected under stereomicroscope, n = 28 histologically sectioned and microscopically examined) and from the mouth of the Quequén Salado River (38°56′S, 60°33′W) (n = 14 dissected under stereomicroscope). Tagelus plebeius was found housing two ciliate species without apparent host reaction and acting as first intermediate host for two digenetic trematode species of the families Fellodistomidae and Gymnophallidae, by hosting sporocysts (mainly in gonad and digestive gland that results in the replacement of host tissues) and as second intermediate host by housing a gymnophallid metacercaria. Likewise, T. plebeius was found parasitized by a larval spirurinae nematode encapsulated by hemocytes. The finding of two ciliate species, the gymnophallid cercaria and metacercaria, and the larval nematode represents the first record for the host. The Southwestern Atlantic populations of this clam seem to be devoid of serious pathogens in the study area.

Identifying repaired shell damage and abnormal calcification in the stout razor clam Tagelus plebeius as a tool to investigate its ecological interactions

Analysis of acetate peels of shell sections of the stout razor clam Tagelus plebeius from the Mar Chiquita coastal lagoon (37° 32′S, 57°19′W, Argentina) revealed the presence of a series of repaired shell margin breaks and different types of abnormal calcifications on the inner surface of their valves. Shell damage and subsequent repair was observed in 73% of the specimens analysed (70.3% of them with scars in both valves around the shell margin, 54.5% with the posterior shell area damaged in one or both valves, 30% with more than one damage). There were only few sediment grains incorporated in the shell matrix when scars occurred around the shell margin. A field experiment suggests that this pattern of shell damage results from natural re-burrowing (vertical movement) activities. However, 10% of the individuals showed an inner shell alteration forming a blister full of sediment grains in the area of the shell pallial sinus. These blisters were associated with repaired shell breaks in the posterior part of the valve, which was confirmed with a field experiment. The development of such blisters could be an indirect consequence of sub-lethal predatory attacks by the American oystercatcher Haematopus palliatus, given that this species breaks the posterior part of the shells of stout razor clams when extracting them from the sediments. The third type of shell alteration (94.3% of the shells) was an orange to brown coloration on the inner shell surface concurrently with irregular carbonate deposition that, in some cases, results in the formation of localised calcium carbonate concretions. This pattern is associated with the presence of metacercariae of gymnophallid parasites. In conclusion, Tagelus plebeius is able to repair its shell after damage produced by different agents. These repairs are very distinctive and, thus, they can be used as evidence of interactions between this clam and its environment (e.g. sediment characteristics) and the associated community (e.g., predators, parasites).

Environmental heterogeneity and species responses to fishing disturbance: are the effects of clam harvesting spatially consistent?

Small-scale artisanal fisheries of the stout razor clam Tagelus plebeius are currently developing in intertidal habitats of several southwestern Atlantic estuaries (36–39°S) in many cases conflicting with habitat conservation. We evaluated the effects of this harvesting on non-target benthic species with replicated experiments conducted simultaneously at six different locations. Given the tendency of burrowing crabs Chasmagnathus granulata to rapidly colonize disturbed plots and excavate new burrows, our a priori prediction was that local effects of clam harvesting would vary depending on the local density of burrowing crabs because it may determine contrasting levels of burrowing disturbance after clam harvesting. To test this hypothesis, experimental plots were distributed equally between habitats characterized by contrasting levels of burrowing crab density. Contrary to our expectation, burrowing crabs recolonized all the disturbed plots at similar rates. The effects of clam harvesting on burrowing crabs, however, varied temporally from positive at low-density mosaics to negative at high-density mosaics, probably due to temporal variations in crab wandering behavior. Juveniles of the crab Cyrtograpsus angulatus showed location-dependent positive responses to the clam harvesting treatment associated with increases in the amount of shell material exposed at the surface during harvesting. Harvesting significantly affects the density of the polychaete Laeonereis acuta in a few particular locations and sampling dates. Location-dependent increases of this species in disturbed plots were observed after recruitment events, suggesting recruitment enhancement by bottom roughness interacting with differences among locations in larval supply. These results demonstrate that extrapolation of results from a single location may be inaccurate even for nearby areas. We strongly advocate that the occurrence and nature of location-dependency should be integrated in the design of management programs.

Kleptoparasitism by Brown-hooded Gulls and Grey-hooded Gulls on American Oystercatchers

Abstract This study describes qualitatively and quantitatively the kleptoparasitic behavior of the Brown-hooded Gull (Larus maculipennis) and Grey-hooded Gull (Larus cirrocephalus) on the American Oystercatcher (Haematopus palliatus), and considers the influence of environmental variables on the occurrence and success of the kleptoparasitism. Focal and scan samplings were performed, recording a total of 358 kleptoparasitic attempts. The overall occurrence rate was 1.2 ± 1.3 attempts per 5 min., of which 42% of attempts were successful. All kleptoparasitic attempts were performed when oystercatchers were feeding on Stout Razor Clams (Tagellus plebeius). Gulls stole food from Oystercatchers by two kleptoparasitic tactics; running (used in 40% of cases) and flying (used in 60% of cases). A significant difference in the rate of success of kleptoparasitism and an increase in the use of flying kleptoparasitism were observed under windy conditions. Gulls showed limited ability to open clams by themselves, and ne...

Role of Holocene beds of the stout razor clam Tagelus plebeius in structuring present benthic communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 185:213-228 (1999) - doi:10.3354/meps185213 Role of Holocene beds of the stout razor clam Tagelus plebeius in structuring present benthic communities Jorge Gutiérrez*, Oscar Iribarne Departamento de Biología (FCEyN), Universidad Nacional de Mar del Plata, CC 573 Correo Argentino Central, (7600) Mar del Plata, Argentina *E-mail: jlgutie@mdp.edu.ar ABSTRACT: Shell beds of the stout razor clam Tagelus plebeius in life position are common in the intertidal areas of several SW Atlantic estuaries (36° to 39° S). In this study we investigate the effect of this habitat structure on the benthic community, focusing on: (1) species which use this habitat as a refuge, (2) characteristics of the internal and external shell sediment and the abundance of macroinfauna and meiofauna in each one, (3) the effect of removing or introducing life-position shells on the abundance of macroinfaunal and meiofaunal organisms, (4) the effectiveness of shells as predator excluders and (5) sedimentary balance in shell beds and the role of superficial life-position shells. Eighteen macrofaunal species were encountered inhabiting the shell cavities; the amphipod Corophium insidiosum, the gastropod Heleobia australis and the polychaete Laeonereis acuta were the most abundant. Water and organic matter content were higher in the inner shell sediment than in the sediment sampled outside, but the distribution of phi-grain size values did not differ significantly between them. Except for nematodes, all the meiofaunal taxa and C. insidiosum showed higher abundance in the inner shell sediment. Removal of life-position shells in a shell bed negatively affected the abundance of C. insidiosum and the polychaete Heteromastus similis. Shell introduction in a mud flat had a positive effect on the abundance of almost all the taxa encountered. Two predator exclusion experiments indicate that these shells protect the fauna living within the shells and the underlying shell infauna from motile surface predators. Observations of shorebird feeding behavior showed that they rarely peck into the shell cavities. Daily measurements of the protruding length of shells demonstrated that these beds are exposed to erosive regimes, and shell removal in a shell assemblage destabilizes the sediment. The evidence suggests that superficial shells positively affect the diversity and abundance of organisms. KEY WORDS: Habitat structure · Shell beds · Physical ecosystem engineers · Positive effects · Taphonomic feedback · Benthos · Tagelus plebeius Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 185. Publication date: August 20, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Shorebird predation may explain the origin of Holocene beds of stout razor clams in life position

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 167:301-306 (1998) - doi:10.3354/meps167301 Shorebird predation may explain the origin of Holocene beds of stout razor clams in life position Oscar Iribarne*, Juan Valero, Mariano M. Martinez, Luis Lucifora, Silvina Bachmann Departamento de Biología (FCEyN), Universidad Nacional de Mar del Plata, CC 573 Correo Central (7600), Mar del Plata, Argentina *E-mail: osiriba@mdp.edu.ar Several hypotheses have been proposed to explain the origin of death assemblages of stout razor clams Tagelus plebeius buried in life position found in Holocene sediments in coastal Argentina and Uruguay: (1) a rapid decrease of sea level, (2) obstruction of the mouth of a coastal lagoon and episodic deposition of fluvial sediments in the mouth of a creek, and (3) a 'taphonomic feedback' process. Hypothesis 1 has been discarded, Hypothesis 2 only has a local explanation, while based on current information Hypothesis 3 is unlikely. A bird predation hypothesis is proposed here on the basis of a study of an extant population. The density of an extant population at the Mar Chiquita coastal lagoon, Argentina (37°46'S, 57°27'W), is higher in the lower intertidal (up to 200 clams m-2) and decreases towards the upper intertidal, and clam size is correlated with burial depth. However, live individuals there coexist with large densities (up to 1500 clams m-2) of dead clams in life position, with densities peaking at the middle-upper intertidal. These shells showed no size-depth of burial correlation. Stout razor clams in fossil deposits (1500 yr BP) also showed large densities of shells in life position (528 clams m-2, SD = 16, n = 20) with no clam size-burial depth relationship. Predation by the American oystercatcher Haematopus palliatus is an important cause of mortality year-round, taking 28 clam h-1 during 3:43 h d-1. Half of the successful attacks left shells in life position buried in the sediment. A computer simulation based on this information showed that predation by 1 oystercatcher produces 9.2 life-position shells m-2 yr-1 (SD = 3.7 life-position shells m-2 yr-1, n = 10000). Thus, 89.5 yr (95% CL = 50-422 yr) are required to generate a mean shell density similar to the one found on our study site (824 clams m-2). Thus, predation by oystercatchers generates a pattern similar to fossil assemblages and is the most likely explanation for the Holocene shell assemblages of the stout razor clams. Intertidal · Predation · Paleoecology · Stout razor clams · Oystercatchers Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 167. Publication date: June 18, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.