Land Snail Shells Research Articles

ENVIRONMENTAL STRESS AND ITERATIVE PAEDOMORPHISM IN SHELLS OFPOECILOZONITES(GASTROPODA: GASTRODONTIDAE) FROM BERMUDA

Considerable refinement of the surficial geology and biostratigraphy Bermuda has resulted in the proper ordering of the phylogenetic sequence of Poecilozonites, and thus offers an opportunity to examine evolutionary pathways within this taxon. Paedomorphism, the retention of juvenile ontogenetic characteristics into adulthood, is a recurrent morphological manifestation in fossil land snail shells of the subgenus P. (Poecilozonites) on this isolated oceanic island. The paleontology of this endemic taxon has been examined over the past century and was a key example of “punctuated equilibria” (PE) in the late 1960s and early 1970s. In a previous study, we documented the biostratigraphy and geochronology from the known fossil record of P. (Poecilozonites) representing atleast the past 500 kyr. Here we focus specifically on paedomorphic forms that appeared in shells at the onset of the last interglaciation, marine isotopes stages (MIS) 6/5e and again at the beginning of the Holocene (MIS 2/1). There are many possible mechanisms to explain the occurrence of paedomorphism including PE, but of importance to this discussion is that neither the size nor the fossil record of Poecilozonites show three independent lineages as proposed by Gould (1969). Gould's several named paedomorphic forms supposedly branching from P. bermudensis over the past 300 kyr, occur only during the last interglacial (sensu lato) MIS 5, and the Holocene (MIS 1). Both punctuation and stasis characterize the morphological changes of this taxon over the past 140 ka, but these changes are reversible, and no speciation is evident.

A New capability for 41Ca analysis using [formula omitted] at the Xi’an-AMS

The analysis of 41Ca can be quantified by measuring the ratio 41Ca/40Ca. At present, ratios of 41Ca/40Ca ≤ 10−11 can only be measured by accelerator mass spectrometry (AMS). The sensitivity is mainly limited by the interference of the isobar 41K. With compact AMS (≤1 MV), abundance sensitivities of 10−11 to 10−12 have been demonstrated, but this may necessitate the measurement of 39K to correct for the 41K background. With a 3 MV AMS, the dE/dx method can still be used to partially separate 41Ca from 41K. In this work, a new capability for 41Ca analysis has been tested at the Xi’an-AMS. Ca4+ was chosen to achieve a balanced performance between 41Ca/41K separation and transmission efficiency. A 41Ca/40Ca background level of near 10−13 was achieved without the need for 39K correction. This new analytical capability at our facility was then applied to 41Ca tracer samples from our studies on the “White Jade” land snail shells, in which 41Ca was used as a tracer for studying the absorption rate of calcium.

Equilibrated clumped isotope signatures of land-snail shells observed from laboratory culturing experiments and its environmental implications

This study reports on the clumped isotope values (Δ47) of land-snail shells precipitated at known temperatures ranging from 20 °C to 30 °C. Our observed shell Δ47 values fall into the uncertainties of published Δ47–T calibration line (e.g. Kelson et al., 2017), indicating the shell aragonite of land snails is precipitated at clumped isotopic equilibrium without an obvious Δ47 vital effect. The Δ47 data are neither related to the various bulk isotopic input sources (both for δ13C and δ18O) which result from differences in the supplied food and water; nor are they related to the ingested carbonate composition or snail growth rate. Furthermore, we preliminarily applied the Δ47–T calibration (Kelson et al., 2017) to calculate the mean growth temperatures of the parent snails. Results suggest that the clumped isotope values for land-snail shells can be regarded as a useful tool to reconstruct the mean seasonal temperature of snail activity when the environmental parameters are optimum. Future studies should focus on the applicability of this relationship to snails in natural environments where the self-preservation or acclimatization mechanisms are more complex.

Reliability of shell carbon isotope composition of different land snail species as a climate proxy: A case study in the monsoon region of China

Carbon isotope compositions of land snail shells (δ13Cshell) are shown to be indicative of local climate conditions. However, it is largely unknown how the responses of δ13Cshell to climatic factors changes amongst different species. In this study, we collected 3 species of land snail shells across the East Asian monsoon region of China to explore the overall relationship between δ13Cshell as well as the response of individual species to the regional climate. Results show that, whereas all species collectively can provide a consensus relation between δ13Cshell and local climatic factors such as temperature and precipitation; the response of individual species to the fluctuations of these factors is not uniform. Specifically, while the southerly species Bradybaena similaris exhibits robust δ13Cshell – mean precipitation correlation in both linearity and sensitivity, a common northerly species, Cathaica fasciola, only finds limited utility as a climate indicator, particularly for precipitation. Meanwhile, the south-central species Acusta ravida appears to be able to faithfully record past climate conditions despite showing a wider distribution and a broader habitat. Such species-dependent nature in the relations between δ13Cshell and local climatic factors can be attributed to the effect of ingested carbonate and variations in eco-physiological factors of different species, and is expected to be widespread, suggesting the need to be taken into consideration for future studies.

Toward an Ethnoarchaeomalacology of Achatina in East Africa

Land snail shell is a material commonly identified in the Late Holocene archaeological record of eastern Africa. Typically, archaeologists designate land snail shell as a natural occurrence or as debris produced from human subsistence. Ethnographic observations in lowland northeastern Tanzania show that contemporary communities employ the soft parts and shells of land snails, particularly Achatina fulica, for a range of everyday and special purposes. The array of land snail uses by mixed subsistence farmers and agropastoralists in the area documents the significance of A. fulica and other robust land snail species. Present uses of land snails observed in Tanzania offer a set of analogies that, when critically applied, can enrich archaeologists’ interpretations of land snail debris in antiquity.

Oxygen stable isotopic disparities among sympatric small land snail species from northwest Minnesota, USA

The oxygen isotopic composition (δ18O) of land snail shells can be a valuable paleoenvironmental archive if the climatic parameters that influence the isotopic system are fully understood. Previous calibration studies have examined a limited number of species or individuals, and most have focused on larger (>10mm) taxa, which do not represent the dominant shell material in the Quaternary fossil record. In this study, we evaluate the δ18O values of small land snails (<10mm), which are common in modern settings and are often preserved in a wide array of Quaternary geologic and archeologic deposits. Our primary goal was to determine if coexisting species record equivalent isotopic information in their shells, regardless of differences in their ecology, dietary habits, behavior, and/or body size. We collected and analyzed 265 individuals of 11 species from 12 sites in northwest Minnesota (USA), which exhibits extremely abundant and diverse terrestrial malacofauna in North America. We did not observe significant correlations between shell δ18O values and the type of ecosystem (forest/grassland) or hydrologic setting (upland/lowland). However, the majority of species differed significantly in shell δ18O values. Larger taxa (Catinella, Succinea, Discus) consistently yielded higher δ18O values than smaller taxa (Euconulus, Gastrocopta, Hawaiia, Vallonia), by up to ~3‰. These isotopic offsets among sympatric taxa could be attributed to a number of physical, behavioral, and/or evolutionary traits, including the ability of larger species to tolerate drier conditions better than their smaller counterparts, differences in their preferred microhabitats or phylogentic non-independence. Regardless of the reason, our results imply that researchers should not combine isotopic data from different types of land snails without first investigating modern specimens to determine if it is appropriate. Moreover, our data suggest that combining instrumental climate data, a snail flux-balance model, and shell δ18O values can help us to better understand the ecology of land snails.

The Efficiency of Flotation Compared with Other Methods for Recovering Assemblages of Terrestrial and Aquatic Gastropods from Archaeological Deposits, with Reference to the Site of Pico Ramos (Basque Country, Spain)

ABSTRACTWe analysed assemblages of shells of land snails and small aquatic and wetland gastropods from a late Mesolithic-early Neolithic deposit in the cave of Pico Ramos (Basque Country). Shells were recovered by hand during excavation and all excavated deposit was processed by flotation, with a 250 μm mesh to recover floating material and a 1.0 mm mesh to recover the heavy fraction. The total assemblage comprised 5780 individuals (MNI) among 33 taxa, the sieved sub-assemblage having the highest proportions of these (2841 MNI in 31 taxa) and the hand-picked sub-assemblage the lowest (698 MNI in 11 taxa). Eleven taxa were absent from the flotation sub-assemblage, although the recovered MNI (2241; 39% of the total MNI) was high. The palaeoecological implications of the results are considered. Adult and large-sized juvenile shells of the edible land snail Cepaea nemoralis are abundant in the hand-picked sub-assemblage, but it is the absence of small-sized juvenile shells in the flotation and wet-sieved sub-assemblages that permits the inference that the species was collected for consumption. Wet sieving is therefore essential, both for interpreting hand-picked samples and in particular for the recovery of representative assemblages of land molluscs.

Radiocarbon dating of the Pleistocene/Holocene climatic transition across the Chinese Loess Plateau

Abstract The magnetic susceptibility (MS) of Chinese loess deposits is extensively used to reconstruct climate changes from centennial to earth orbital time scales. The approach assumes that the MS is sensitive to the variations of the Asian Summer Monsoon (ASM), and thus that changes in MS are synchronous across the Chinese Loess Plateau. However, this inference has not been fully confirmed due to the limitations of both chronological control of Chinese loess sequences and the climatic proxies of the ASM. Here, we present the results of radiocarbon dating of the shifts in the oxygen isotopic composition of fossil land snail shells (δ 18 O s ) and in MS during the Pleistocene/Holocene transition at various sites in Chinese Loess Plateau. The results show that the age of shift in MS at Pleistocene/Holocene transition at Mangshan, Heshui, and Huanxian sections is 10.43 ka, 8.55 ka, and 7.13 ka BP, respectively. Thus, the shift is time-transgressive with age decreasing from southeast to northwest across the plateau. However, the δ 18 O s record, which is directly related to the precipitation delivered by the ASM, is not significantly time-transgressive, indicating that the ASM strengthened almost simultaneously across the plateau. We suggest that the time-transgressive nature of the shifts in MS may result from the low amplitude of the ASM strengthening during the Pleistocene/Holocene transition. Overall, our results demonstrate a regional difference in the insensitivity of MS to low amplitude climatic changes, and they challenge the previously-held assumption that the ages of climatic boundary based on MS stratigraphy are time-equivalent in Chinese loess.

Middle Pleistocene (MIS 14) environmental conditions in the central Mediterranean derived from terrestrial molluscs and carbonate stable isotopes from Sulmona Basin (Italy)

A paleosol from the Middle Pleistocene lacustrine-fluvial succession of Sulmona Basin, central Italy, was analysed for the land snail shell content, and the stable isotope composition of the shells and associated pedogenic carbonates. The paleosol – known as Fiorata Paleosol – is covered by a thick tephra layer dated to ca. 527ka allowing the pedogenetic horizons to be correlated to the marine isotope stage (MIS) 14-early MIS 13 interval. The terrestrial mollusc assemblage contained few individuals and was characterized by a low number of species which predominantly indicate open and dry habitats, thus suggesting that Fiorata Paleosol likely developed during glacial conditions of the MIS 14. The δ13C values of pedogenic carbonates and terrestrial shells indicate prevailing C3-type vegetation, probably marked by some degree of water stress. Calculation of the δ18O precipitation values, derived from pedogenic carbonates and shell δ18O values, indicate that the average temperature was 3–5°C lower than present day. This study highlights how paleosols, despite offering only snapshots of past climate and environments, provide valuable complementary information to paleoclimatic data obtained in the adjacent lacustrine intervals, specifically for the Sulmona successions.

An incised shell object from Baradostian (Early Upper Palaeolithic) layers in Shanidar Cave, Iraqi Kurdistan

Shanidar Cave contains one of the most important Palaeolithic archaeological sequences in West Asia. During renewed excavations of Baradostian (Upper Palaeolithic) layers in the cave, an incised land-snail shell fragment was recovered. A natural cause seems unlikely and it does not appear likely to reflect palaeoeconomic functions. It is suggested tentatively that this may have been made during manufacture of a composite artefact designed for visual display. Although Upper Palaeolithic ornaments are often reported, composite ornaments of this period are rather unusual.

Beads, pigments and early Holocene ornamental traditions at Bushman Rock Shelter, South Africa

Beads and pigments represent compelling evidence that humans decorated their bodies and used them to convey complex social messages. While the manufacturing process of ostrich eggshell and marine shell beads is firmly established, their common association with pigment residues still remains poorly understood. Here, we focus on various types of beads from the early Holocene of Bushman Rock Shelter (Limpopo, South Africa), namely ostrich eggshell, giant land snail (Achatina sp.) shell and marine shell (Nassarius kraussianus) beads. We propose a new approach combining a technological and use-wear study of the beads with chemical analyses (SEM-EDS and Raman analyses) of the coloured residues they bear. Together with the discovery of marine beads, of particular interest since they originate more than 240km away from the site, our detailed study of the beads and associated pigment residues demonstrates a complex system of ornamental representation. We identified a minimum of two types of red compound ‘recipes’, with evidence that one was employed as adhesive while the other one might be consistent with the production of a pigment. Non-local minerals were recognised in adhesive recipes, namely chromite and ilmenite in one case, and graphite in the other. We further discuss ornamental traditions, their social implications and their increasing importance at the onset of the Holocene in southern Africa.

Diet reconstruction of monks at St. Peter’s monastery in Osor: the role of molluscs in following the Rule of St. Benedict

A significant amount of land and marine malacofauna remains have been uncovered during the perennial excavations of St. Peter’s monastery in Osor, Croatia. This paper examines the dietary significance of edible land snail and marine shell based on extensive taphonomical analyses. In the theoretical part of the paper the interpretation of dietary restrictions in regard to the Rule of St. Benedict and specifically its interpretation by the monks of St. Peter’s monastery is given. Filtering the results of taphonomical analyses of this indirect evidence for subsistence through theoretical frameworks socially mediated food acquisition and consumption choices of Benedictine monks at St. Peter’s monastery are explored.

Distribution records of ant species nesting in empty land snail shells in Japan

Distribution records of ant species nesting in empty land snail shells in Japan

Novel Bioceramic Production via Mechanochemical Conversion from Plate Limpet (&lt;i&gt;Tectura&lt;/i&gt; &lt;i&gt;scutum&lt;/i&gt;) - Shells

Calcium phosphates are very important biomaterials for orthopaedic and dental applications. Hydroxyapatite (HA) is one of the important phases used for grafting. Those are produced from synthetic and natural sources with various methods. Especially nano-bioceramics can be produced through calcitic and aragonitic structures (i.e. mussel shells, sea snail shells, land snail shells and sea urchin shells). The plate limpet shells were used. The plate limpet is a gastropod, a soft-bodied invertebrate (an animal without a backbone) that is protected by a very hard, flattened conical shell. In this study the Plate Limpet (Tectura scutum) shells were obtained from a local gift store in Istanbul. The habitation of these limpets broadens from south Alaska down to California - Mexico. First the exact CaCO3 content was measured with thermal analysis (DTA/TGA). Here in this study agitation was carried out on a hot-plate (i.e. mechano-chemical processing). First the temperature was set at 80 °C for 15 min. Then equivalent amount to CaO H3PO4 was added dropwise for HA phase formation and the reaction was set on a hotplate for 8 hours. The dried sediments HA part was divided into 2 groups. One group was sintered to 835 °C and second group to 855 °C. Here x-ray diffraction and scanning electron microscope (SEM) studies were performed. From the study various HA phases and TCP phases were obtained. A previous study done with Atlantic Deer Cowrie encourages nanobioceramic production from natural sources. This study proposes that mechanochemical agitation with very simple way for producing nano-sized calcium phosphates for future bioengineering scaffold applications.

A late Pleistocene refugium in Mediterranean North Africa? Palaeoenvironmental reconstruction from stable isotope analyses of land snail shells (Haua Fteah, Libya)

The late Pleistocene to Holocene archaeological record of North Africa is key to understanding the emergence of anatomically modern humans into West Asia and Europe, and the broadening of subsistence strategies in the shift from hunter-gatherer to pastoral-agricultural lifeways. Some contend that these developments were modulated by major shifts in climate and environment. Evaluation of this hypothesis requires the pairing of local and regional climate records with well-dated archaeological sequences. The Haua Fteah archaeological site in the Gebel Akhdar region of Libya provides a key site to test this hypothesis as the cave contains one of the longest and most complete sequences of human occupation in North Africa as well as abundant material for palaeoenvironmental reconstruction. This study uses stable isotope analyses (δ18O and δ13C) of the terrestrial mollusc Helix melanostoma to construct a palaeoenvironmental framework for interpreting North African human-environment interactions from the Upper Palaeolithic to the Neolithic (∼30,000 to 5000 years ago).The land snail stable isotope records from Haua Fteah suggests that cool arid conditions in the cave peaked during marine isotope stage (MIS) 2. This stage was, however, only marginally drier than previous and subsequent stages and coincided with an increase in occupation density in the cave. This suggests that the Gebel Akhdar may have served as an environmental refugium from the more extreme aridity in the surrounding Sahara and arid coastal plains for Late Stone Age (LSA) populations in North Africa. Conditions became progressively wetter towards the Holocene. However, generally wetter conditions were interrupted by two arid episodes at c. 8.0 ka and 7.3 ka that appear to coincide with regional changes reflected elsewhere in the Mediterranean basin.

Effect of biogenic and synthetic starting materials on the structure of hydroxyapatite bioceramics

In this study, a synthesis of hydroxyapatite by wet-chemical precipitation route was conducted, using a number of calcium oxide sources. Two biogenic calcium carbonates, which are common in nature, i.e. bird eggshells (Gallus gallus domesticus) and land snail shells (from Arianta arbustorum), as well as commercially available synthetic calcium oxides were used as calcium oxide sources. Calcium oxide starting materials and synthesised calcium phosphate products were investigated. Hydroxyapatite bioceramics obtained from the calcium oxides of different origins had significant differences in microstructure after thermal treatment. Microelement analysis of hydroxyapatite products by inductively coupled plasma mass spectroscopy (ICP-MS) showed that they incorporate different amounts of microelements. The microstructure parameters of the obtained bioceramics were influenced by the presence of multiple trace elements in the structure of hydroxyapatite, which also significantly influenced the crystal lattice parameters. The origin of the calcium oxide starting material has a significant impact on the physicochemical properties and quality of bioceramic implants and, therefore, could also affect the biological properties of these materials.

Synthesis and Characterization of Biopolymeric Chitosan Derived from Land Snail Shells and Its Potential for Pb2+ Removal from Aqueous Solution.

Pb2+ is considered to be a very toxic pollutant in the aquatic environmental media. Biopolymeric chitosan synthesized from snail shell has been studied for its potential to remove heavy metals from aqueous solution. The experiments were conducted in the range of 1–50 mg/L initial Pb2+ concentration at 298 K. The effects of pH, adsorbent dosage and contact time on the adsorptive property of the adsorbent were investigated and optimized. The derived chitosan was characterized using Fourier transform infrared spectrometer (FT-IR) and X-ray florescence (XRF). The experimental data obtained were analysed using the Langmuir and Freundlich adsorption isotherm models. The Langmuir model and pseudo second order kinetic model suitably described the adsorption and kinetics of the process with regression coefficients of 0.99 and 1.00, respectively. Sodium hydroxide was a better desorbing agent than hydrochloric acid and de-ionized water. From the results obtained, it is concluded that synthesized biopolymers from land snail shells has the potential for the removal of Pb2+ from aqueous solutions.

Land gastropod piercing during the Late Pleistocene and Early Holocene in the Haua Fteah, Libya

Land snail shell is a frequent constituent of archaeological sites, but it is rarely clear whether it represents food refuse, the remains of scavengers, or evidence for natural processes. Piercing of land snail shells enables the animal to be extracted from the shell and thus provides direct evidence for human consumption. We report pierced land snails from the Haua Fteah, Libya. The earliest pierced land snail shell in the Haua Fteah pre-dates the Last Interglacial, while the most recent is Late-Classical in age, but the largest quantities are in layers of Late-Glacial and earliest Holocene age, where they are associated with atypical microliths which may have been used to pierce shells to enable easy extraction of the animal.

Harorepupu aotearoa (Onygenales) gen. sp. nov.; a threatened fungus from shells of Powelliphanta and Paryphanta snails (Rhytididae).

A cleistothecial fungus, known only from the shells of giant land snails of the family Rhytidae, is described as a new genus and species within Onygenales, Harorepupu aotearoa gen. sp. nov. Known only from the sexual morph, this fungus is characterized morphologically by a membranous ascoma with no appendages and ascospores with a sparse network of ridges. Ribosomal DNA sequences place the new species within Onygenales, but comparison with the known genetic diversity within the order linked it to no existing genus or family. It is the first species of Onygenales reported from the shells of terrestrial snails. This fungus has been listed as Critically Endangered in New Zealand and has been previously referred to as 'Trichocomaceae gen. nov.' in those threat lists.

Oxygen isotope signatures from land snail (Helix melanostoma) shells and body fluid: Proxies for reconstructing Mediterranean and North African rainfall

In this paper, we show that oxygen isotope ratios from the shell carbonate of the land snail Helix melanostoma reflect local rainfall parameters. Stable oxygen isotopes were measured in the body fluid (δ18Obody) and shells (δ18Oshell) of live-collected H. melanostoma along a north–south transect across the Gebel Akhdar in northeast Libya. δ18Obody ranged between −8.1‰ and 13.0‰ whilst δ18Oshell ranged between −1.0‰ and +2.8‰. To investigate the relationship between snail oxygen isotope composition and climate, these measurements were correlated with ambient air temperature, relative humidity, rainfall amount, and the δ18O composition of rainwater (δ18Orain). Strong and significant correlations were found between δ18Oshell and δ18Orain, and between δ18Oshell and rainfall amount (R2=0.79 and 0.85 respectively) suggesting that H. melanostoma shells can be used as a proxy for past rainfall conditions. When combined in multiple linear regressions, δ18Orain and rainfall amount explained 90% of the variance in δ18Oshell (R2=0.90). Simple and multiple linear regressions were used to develop predictive models for these climate parameters. As H. melanostoma shells are commonly found in Mediterranean and North African archaeological and geological deposits, the predictive equations developed in this study hold great potential for reconstructing Pleistocene to Holocene rainfall and aridity patterns in the Gebel Akhdar and for assessing the relationship between environmental changes and human behavioural changes.