Live Gastropods Research Articles

Catatan Biodiversitas Gastropoda pada Ekosistem Mangrove Desa Kramat Kecamatan Mananggu Kabupaten Boalemo, Provinsi Gorontalo

Anthropogenic actions that degrade mangroves in coastal areas are suspected to reduce the biodiversity of gastropod fauna in this region. The purpose of this research, conducted from July to October 2021, was to evaluate the number of species, dominance, and diversity of gastropods and the richness and similarity of gastropod communities in the coastal mangrove ecosystem in Kramat Village, Mananggu-Boalemo District. The survey method carried out by purposive sampling was on a 3-line transect as an observation station based on differences in the width of the mangrove belt. The study results recorded 14 species of gastropod members from 8 families at all stations. The highest presence was recorded in the family Potamidae, with members of Terebralia sulcata being the most abundant species at all stations. The unique environmental conditions in all stations are land conversion in the area behind the mangrove formation, and the substrate tends to be acidic (pH 6). This study indicates the complexity between stations as a habitat for live gastropods as epi and tree fauna in the mangrove community of Kramat Village .

Influence of the technology of processing of meat of snails in anabiosis on the content of toxic elements

An important problem today is the pollution of the territory of Ukraine with heavy metals: lead, cadmium, copper, zinc and others. Relevance of the topic is that nowadays the issues of safety and quality control are not fully resolved in the country, as well as the veterinary and sanitary assessment of the meat of snails of the genus Helix, which are used for food purposes; in particular, there is no data on the content of toxic elements in a meat of different species of snails for different processing modes. The aim of the study was to investigate the meat of snails of the genus Helix for different processing to find heavy metals in it. The meat of snails of genus Helix has been used for the study, sub-species: Helix pomatia, Helix aspersa maxima and Helix aspersa muller. 30 samples of snails of each species grown in snails farm in the Kyiv region have been selected for the study. Meat of snails has been studied after different technological processing: live, chilled, and cooked and frozen (n = 30). The research has been conducted in the winter, when the snails have been in anabiosis. Results of the study show that in accordance with the requirements of DSTU 7821:2016 “Live edible gastropod molluscs. Specifications”, the content of toxic elements in the meat of live snails corresponds to the maximum allowable level. One of the key indicators of safety of meat, in accordance with the requirements of DSTU 7821:2016, is the content of toxic elements in it: lead, cadmium, copper, zinc. It has been found that the meat of snails, in addition to the above mentioned heavy metals, contains also arsenic and iron, which relate to toxic elements as well. Therefore, when developing a complex system of veterinary and sanitary assessment of quality and safety of snails’ meat, we propose to control it on the content of such toxic elements as arsenic and iron. In addition, we recommend to improve the “The Required Minimum List…” (2004) with the studies of the meat of snails of the genus Helix for different technological processing on the content of toxic elements: lead, cadmium, copper, zinc, arsenic and iron.

Evaluation of new approaches to the access of official monitoring results for live bivalves molluscs

BackgroundLive bivalve molluscs, echinoderms, tunicates and marine gastropod are referred in EU food laws, and require member states to implement official controls in classified production areas, with the monitoring and classification of those areas. If, due to contaminant tests results, a production area is closed, any product from there is prohibited to be commercialized. Mobile applications optical character recognition (OCR) functionalities could ease the access to contaminant levels and production area classifications. This study verifies what information is available in live bivalves’ labels, describes an OCR algorithm for those labels and evaluates it.Methods86 labels were selected from four sale points in Lisbon, and photographed using smartphones. Each label was evaluated by a human to determine what data was available (either required or not). An OCR algorithm was developed and applied on the collected labels and validated against the data extracted by the human analysis.ResultsThe analysis shows that all the labels included the required information, and 63% of the labels included the identifier for the production zone. The label-reading algorithm performs with an accuracy of 79.85% for the individual values.ConclusionHigh accuracy of the developed label-reading algorithm shows potential for providing instant automatic access to the date and production area, but is affected by the variability on the label structure. Although not required by food laws, the majority of the sampled labels included complementary information (classified production area) that will allow access to more precise information about the existing biotoxin tests and analysis results.

What makes a good home for hermits? Assessing gastropod shell density and relative strength

ABSTRACTThe survival and reproductive success of hermit crabs is intrinsically linked to the quality of their domicile shells. Because damaged or eroded shells can result in greater predation, evaluating shell structure may aid our understanding of population dynamics. We assessed the structural attributes of Cerithium atratum shells through assessments of (a) density using a novel approach involving computed tomography and (b) tolerance to compressive force. Our goal was to investigate factors that may influence decision making in hermit crabs, specifically those that balance the degree of protection afforded by a shell (i.e. density and strength) with the energetic costs of carrying such resources. We compared the density and relative strength (i.e. using compression tests) of shells inhabited by live gastropods, hermit crabs (Pagurus criniticornis) and those found empty in the environment. Results failed to show any relationship between density and shell size, but there was a notable effect of shell density among treatment groups (gastropod/empty/hermit crab). There was also a predictable effect of shell size on maximum compressive force, which was consistent among occupants. Our results suggest that hermit crabs integrate multiple sources of information, selecting homes that while less dense (i.e. reducing the energy costs of carrying these resources), still offer sufficient resistance to compressive forces (e.g. such as those inflicted by shell-breaking predators). Lastly, we show that shell size generally reflects shell strength, thus explaining the motivation of hermit crabs to search for and indeed fight over the larger homes.

Ecological relations between hermit crabs and their shell-supplying gastropods: Constrained consumers

Hermit crabs are critically dependent upon gastropod shells for their survival and reproductive fitness. While anecdotal reports have suggested that hermit crabs may be capable of removing live gastropods from their shells to access the essential shell resource, no systematic experiments have been conducted to investigate this possibility. This paper reports experiments on both marine ( Pagurus bernhardus) and terrestrial ( Coenobita compressus) hermit crabs in which crabs were paired in the laboratory with the gastropods whose shells they inhabit in the field. Pairings included both shelled and naked crabs and spanned the full range of the gastropod life cycle. Neither marine nor terrestrial hermit crabs were successful at removing live gastropods from their shells. Furthermore, only a small fraction of the crabs (5.7%) were capable of accessing shells in which the gastropod had been killed in advance, with its body left intact inside the shell. Finally, although hermit crabs readily entered empty shells positioned on the surface, few crabs (14.3%) were able to access empty shells that were buried just centimeters beneath them. These results suggest that hermit crabs are constrained consumers, with the shells they seek only being accessible during a narrow time window, which begins following natural gastropod death and bodily decomposition and which typically ends when the gastropod's remnant shell has been buried by tidal forces. Further experiments are needed on more species of hermit crabs as well as fine-grained measurements of (i) the mechanical force required to pull a gastropod body from its shell and (ii) the maximum corresponding force that can be generated by different hermit crab species' chelipeds.

Epizoanthus spp. Associations Revealed using DNA Markers: A Case Study from Kochi, Japan

Zoanthids (Cnidaria, Hexacorallia) of the genus Epizoanthus are often found in association with other marine invertebrates, including gastropods and hermit crabs. However, little information exists on the specificity and nature of these associations due to a lack of investigation into Epizoanthus species diversity, and the taxonomy of Epizoanthus is therefore confused. In this study, analyses of morphological data (tentacle number, polyp size, etc) and molecular data (mitochondrial cytochrome oxidase subunit 1 = COI, 16S ribosomal DNA = 16S rDNA) were used to examine Epizoanthus specimens from Tosa Bay, Kochi, Japan. The Epizoanthus specimens were found on both live gastropods (Gemmula unedo) and hermit crabs (Paguristes palythophilus) inhabiting G. unedo and G. cosmoi shells. While morphological analyses did not show clear differences between examined specimens, both COI and mt 16S rDNA clearly divided the specimens into two groups, one associated only with hermit crabs (= Epizoanthus sp. C), and another associated only with living gastropods (= Epizoanthus sp. S). Unexpectedly, DNA sequences from both groups did not match with two previously reported Epizoanthus species from Japan (E. indicus, E. ramosus), indicating they both may be undescribed species. These results highlight the utility of DNA "barcoding" of unknown zoanthids, and will provide a foundation for re-examinations of Epizoanthus species diversity and specificity, which will be critical in understanding the evolution of these unique marine invertebrates.

Diet, prey narcotization and biochemical composition of salivary glands secretions of the volutid snailOdontocymbiola magellanica

Odontocymbiola magellanicais a neogastropod very common in Patagonian shallow waters. It feeds exclusively on molluscs inhabiting the same benthic community. Field studies showed that prey preferences are live gastropods (54%) and bivalves (46%). When no living prey are available they change their trophic behaviour to carrion or cannibalism. Feeding mechanisms observations showed that prey are not asphyxiated by the snail's foot as suggested before for the Volutidae family; they are narcotized by saliva introduced in a cavity made by the foot where prey are immobilized. Saliva is produced by the salivary (SG) and accessory salivary glands (AG) and has a pH around 10, relaxing prey muscles, which are consumed alive. Secretions from AG and aqueous extracts of SG and AG were mainly composed of proteins and glycoproteins, though SDS-PAGE gels revealed that salivary proteins were richer in higher molecular weight bands. Fractionation of secretions from AG on Bio-Gel P-100 yielded only one peak. SDS-PAGE showed that it consisted of only one band (MW 51.3 kDa). Microanalysis of cations showed a higher concentration of calcium and magnesium in the accessory salivary gland. Hypotheses of function of different glands are given in relation to feeding behaviour and anatomy ofO. magellanica.

Mechanical Devices for Snail-like Locomotion

We have constructed two mechanical snails, Robosnail 1 and Robosnail 2, inspired by the propulsion mechanisms of live gastropods. Each uses a different mechanical strategy to move on a thin layer of viscous fluid. Robosnail 1 uses a flexible flapping sheet to generate lubrication pressures in a viscous Newtonian fluid which in turn propels the snail. Robosnail 2 uses a compressible sliding sheet on a layer of Laponite, a non-Newtonian, finite-yield stress fluid.

Influence of occupant microhabitat on the composition of encrusting communities on gastropod shells

The exploitation of microhabitats is widely considered to increase biodiversity in marine ecosystems. Although intertidal hermit crabs and gastropods may inhabit the same shell type and shore level, their microhabitat may differ depending on the state of the tide. On the south coast of Wales the hermit crab Pagurus bernhardus mainly inhabits the shells of Nucella lapillus (84%). Hermit crab shells had a significantly different encrusting community compared with live N. lapillus shells. At low tide the live gastropods were found on exposed rock surfaces whereas hermit crabs were restricted to tidal pools. Communities encrusting live gastropod shells were characterised by lower species richness and abundance compared with shells inhabited by hermit crabs (12 species found in total). A greater abundance and richness of epibionts was recorded from both shell types during the summer compared with winter. Differences in community composition between shell occupant types were attributed to microhabitats used by gastropods and hermit crabs and the associated desiccation pressures, rather than competitive interactions or shell characteristics. This contradicts earlier studies of subtidal shells where biological processes were considered more important than physical factors in controlling species abundance and richness patterns. The use of rockpool microhabitats by hermit crabs increases the biodiversity of rocky shores, as some species commonly found on hermit-crab-inhabited shells were rare in other local habitats.

Relationships between a hermit crab and its shell resource: spatial patterns within a seagrass-dominated landscape

Abundance patterns of the hermit crab Pagurus maclaughlinae and its gastropod shell resources were compared to one another across the shallow subtidal landscape within Tampa Bay, Florida at a landscape (4.88 ha) and a sub-landscape (1 m 2 ) scale. Specifically, we investigated whether the spatial abundance patterns of P. maclaughlinae over time could be explained by the abundance patterns of either future resources (i.e. live gastropods) or present resources (i.e. empty gastropod shells). The seagrass landscape was sampled for seagrass, hermit crabs, live gastropods and empty gastropod shells during the spring and fall of 1994 and 1995. The distribution of P. mac- laughlinae could be explained by the distribution of its gastropod shell resources when the spatial organization of both P. maclaughlinae and these resources were compared across the landscape. Physical measures of the dominant seagrass Halodule wrightii (i.e. canopy height and shoot density) appeared to be unrelated to the distribution of P. maclaughlinae and either of its shell resources (pre- sent or future) across the landscape. These results suggest that hermit crabs track their 'limited' resources (i.e. gastropod shells) when viewed over the spatial scales examined here. Furthermore, our results suggest that the spatial distribution of future, as well as present resources, adds insight into patterns of hermit crab abundance.

Gastropod mollusks from the continental shelf off Jalisco and Colima, Mexico: species collected with a trawl net

This study examines the distribution and abundance with respect to depth and type of substratum of 86 gastropod species collected from the Pacific continental shelf off Jalisco and Colima, Mexico, in August 1988. Sampling was performed with a trawl net at 22 stations, at depths of 18 to 112 m. A total of 582 individuals pertaining to 42 genera, 25 families, 4 orders and 3 subclasses of gastropods were collected. Abundance of gastropods was similar between 18 and 83 m, but the number of live individuals decreased between 41 and 60 m. Deep (61-83 m) stations registered the lowest diversity; however, the number of species collected alive decreased with depth. No gastropods were collected at stations deeper than 83 m. The number of individuals and species also varied with the type of substratum. Greater heterogeneity of the sediments was found at the shallower stations (18860 m) with medium sand, sandy silt and silty clay substrata. The greatest number of species were collected at stations with sandy silt and medium sand substrata. Total abundance was notably smaller in medium sand, while the abundance of live gastropods was higher in silty clay substratum. The seven most abundant species represented 5 1.2% of all of the individuals. Most of these species are of commercial interest, in particular those of the genera Fusinus, Hexaplex, Ficus, Harpa, Cantharus and Bursa.

Distribution of sponges on the Mauritanian continental shelf

Transect sampling on the continental shelf off the Banc d’Arguin, Mauritania, revealed a patchy distribution of sponge species and populations. Major sponge habitats are inshore coastal sandstone flats harbouring a diverse infaunal sponge fauna, and the moving substrate of shells of live gastropods or empty shells occupied by hermit crabs which harbour a numerically important but species-poor incrusting sponge fauna. The latter forms occur over most of the depth profile. Horizontal distribution of the sponges shows a distinct gap in species and numbers associated with a muddy bottom area where the sediment-rich Banc d’Arguin run-off is found. North and south of this gap the specific composition of the infaunal sponges is considerably different and this is explained as evidence for limitation of range extensions, notably of the southern sponge fauna, by the muddy area.

Sandstream on the northeast Brazilian shelf

A preliminary characterization of seabed morphology and mapping of algal patches within a sandstream on the northeast Brazilian continental shelf off Cape Calcanhar (where the South American coast turns sharply to the west) is presented. The study area (30 km × 30 km) is swept by unidirectional, wind-driven, tidally rectified currents, under the influence of the North Brazil Current. The study was made by use of Landsat Thematic Mapper (TM) data of the seafloor down to 40 m depth, digital bathymetric data from smooth sheets furnished by the Brazilian Navy, echo-sounder profiling and underwater surveying by SCUBA diving. A mesoscale shore-parallel natural zonation of the sandstream was observable on the TM-images: (a) an inner zone dominated by sediment resuspension caused by wave-driven turbulence and tidal currents; (b) an intermediate zone dominated by sand ribbons and other longitudinal bedforms; (c) an outer zone dominated by large-scale sand waves (underwater sand dunes) limited offshore by shore-parallel sandbanks. Image-assisted in situ work, carried out on the latter zone, gave the following results: (1) Morphology and sand composition—the asymmetric sand waves are made of medium quartz sand, with almost straight crests of lengths up to 4 km, heights between 3 and 7 m, and avalanche lee slopes of 30°; on the stoss sides we recorded the presence of ripples and absence of megaripples and benthic ecosystems; on interdune areas, benthic ecosystem patches dominated by foliaceous and calcareous algae were found. (2) Sediment transport—active bedload transport was observable only during the winter season, when the strongest wind-forced currents induce flow separation at the crests and avalanche streams on the lee slope. Within the interdune areas, under the influence of the lee vortices, benthic community data confirms no appreciable abrasion due to sand transport. (3) Biology—species composition and biomass estimates from the algal patches in the first upstream trough are presented, and species composition of bryozoa observed as epibionts on live gastropod shells are analysed. This sandstream shows some similarities to one described from the southeast African continental shelf, which is also under the influence of unidirectional currents.

Stomatopod predation on fossil gastropods from the Plio-Pleistocene of Florida

Stomatopods (mantis shrimps) are important predators in Recent tropical shallow-water communities. Despite a long geological history, they are poorly preserved as fossils, and traces of their predation have never been identified from the fossil record. Here we report on Plio-Pleistocene gastropods (mostly Strombus) from Florida with distinctive holes “punched” into their body whorls. The similarity of these holes to holes punched into live gastropods by Gonadactylus implicates gonodactyloid stomatopods as the predators that made them. Recent gonodactyloids break gastropod shells as thick and thicker than those of the Plio-Pleistocene strombids that were punched. Because our data underestimate the incidence of stomatopod predation, the frequency of holes in these strombids (8–13 percent) suggests that stomatopod predation may be of considerable importance in the ecological and evolutionary history of tropical benthic assemblages.

The reconstruction of quaternary freshwater lakes from the chemical and isotopic composition of gastropod shells: The dead sea rift, Israel

Sr/Ca, Ba/Ca and 87Sr/ 86Sr ratios in fossil freshwater aragonitic gastropods ( Melanopsis praemorsum and Melanoides tuberculata) have been used to reconstruct the water sources of Quaternary lakes in the Jordan River Rift Valley. The reconstruction is based on the assumption that the same waurces which supply freshwater into the Rift Valley in the present (i.e. carbonate water, basaltic water and Rift brines), were active throughout the Quaternary. The distribution coefficients for Sr and Ba were obtained from live gastropods which were collected from modern water bodies in the region. By using these distribution coefficients, the composition of the ancient waters could be derived from the fossil shells' chemistry. Altogether, four ancient sites were sampled of which Mishmar ha'Yarden and Gesher Benot Ya'akov Formations are located in the Upper Jordan Valley and Erq el-Ahmar and Ubeidiya Formations are in its central part. Low salinity carbonate waters (≈300 mg/l) comprised the main H 2O source into the Hula basin in the Upper Jordan Valley. These solutions display a 87Sr/ 86Sr ratio of 0.7082±0.0002, which is significantly higher than the corresponding modern ratio (0.7070), suggesting that the ancient drainage system was initially fed by Upper Eocene carbonate aquifers and shifted later to a Jurassic carbonate system. The Erq el-Ahmar lake in the Central Jordan Valley was supplied by approximately equal proportions of carbonate and basaltic waters, resulting in a water body of low salinity (≈300 mg/l). The water source of Lake Ubeidiya, also in the Central Jordan Valley, was predominantly basaltic, yet its chemistry bears a strong Rift brine signature resulting in a salinity of about 1000–1300 mg/l. The values obtained are in good accord with the biological evaluation of the fossil biota.

Population Structure of Live and Dead Gastropods from Bahia la Choya

Size-frequency distributions and size-survivorship curves were constructed for the following seven species of living gastropods from Bahia la Choya: Cerithideamazatlanica, Cerithideaalbonodosa, Cerithiumstercusmuscarum, Nassariusiodes, Nassariusbrunneostoma, Theodoxusluteofasciatus and Tegularugosa. Size-frequency distributions and size-survivorship curves of empty shells of Cerithideamazatlanica and Cerithiumstercusmuscarum were constructed to evaluate the effects of taphonomic processes on survivorship curves.All size-survivorship curves are convex-up in shape: small size classes show low mortality and mortality increases with increasing size. Despite post-mortem processes, survivorship curves for empty shells mimic the shape of curves based on live individuals.

Epifaunal abundance, association, and overgrowth patterns on large hermit crab shells

Epifaunal abundance, association, and overgrowth patterns are described for seven species occurring on live, empty, and hermit crab-occupied shells of Busycon carica (Gmelin). Alcyonidium polyoum (Hassall) and Membranipora tenuis Desor were significantly more common on live gastropod shells while Hydractinia echinata Fleming and Crepidula fornicata (L.) were more common on hermit crab-occupied shells. A significant negative association was determined between Alcyonidium and Hydractinia on hermit crab-occupied shells; Hydractinia and Sabellaria vulgaris Verrill had a significant positive association. Alcyonidium had the highest mean abundance and highest win-loss ratio in overgrowth observations on hermit crab-occupied shells. Overgrowth interactions between colonial and solitary species were highly intransitive and in many cases not a probable source of mortality.

Substrate specificity in the Devonian tabulate coral Pleurodictyum

The tabulate coral Pleurodictyum americanum Roemer has been cited as an example of a host-specific organism occurring exclusively on the shells of gastropods, particularly Palaeozygopieura hamiltoniae (Hall). Examination of over 1600 specimens of P. americanum, from the Middle Devonian Hamilton Group of western New York, reveals additional complexities which require reinterpretation. While substrate selectivity for Palaeozygopieura shells is evident in all 42 subsamples, a variety of other substrates were also utilized by Pleurodictyum including corals, brachiopods, other molluscs and pebbles. Recent scleractinian corals inhabiting soft bottoms show similar substrate preference, selecting for the tubes of live serpulids, or gastropod shells (invariably with a secondary sipunculid host), but also occasionally settling on unoccupied shells or pebbles. Shell surfaces of P. hamiltoniae, preserved as external molds on the Pleurodictyum epitheca, exhibit encrustation by worm tubes and bryozoans as well as borings and mechanical shell damage, suggesting that these were not the shells of live gastropods. However, the invariant aperture-downward orientation and the high degree of selectivity of P. americanum strongly suggest that the shells were occupied by secondary hosts. □Substrate specificity, commen-salism, tabulate coral, gastropod, sipunculid, Devonian, Hamilton Group, New York.