Behavioural Rhythms of Land Snails in the Field

Circadian and circannual behavioural rhythms of Helix are described in the field. Laboratory studies demonstrate the existence of an endogenous component for these rhythms. The effects of the environmental factors on the snail activities are multiple: light/dark and cold/warm cycles synchronise the behavioural rhythms; a masking effect is observed when it rains since the animals are active throughout the 24 h day; high temperature and low relative humidity cause a complete cessation of activities. In addition, social interactions between and within species can modulate the shape of the rhythms driven by the biological clock.     

Prospects for Studies of Morphological Variability of Land Pulmonate Snails

The main goal of modern investigations into the morphological variability of land pulmonate snails was defined as designing the patterns of taxa structure on the basis of historical analysis of their taxonomic studies. Transition from the investigation of individual characters to an analysis of the organism as a whole assumes the application of the system approach. Systemic properties of the organism can be revealed through the key characters reflecting the process of evolutionary transformation of the correlation chains. In the case of land pulmonate snails, the relationship between the operative and conservative subsystems of the organism can serve as such a key character. The operative subsystem-cephalopodium-fulfills the function of active contacts with the environment; the conservative subsystem-the shell and its content-exercises protective functions. The subsystems are in conflict, and its resolution establishes the main patterns of the organization of pulmonate snails.     

High Predation Pressure by an Introduced Flatworm on Land Snails on the Oceanic Ogasawara Islands1

The introduction of a predatory flatworm, Platydemus manokwari, has been considered a cause of the decline of endemic land snails on the tropical oceanic islands. To clarify the effect of P. manokwari on land snail survival in the field, we examined survival rates of snails experimentally placed in areas where snails are absent (i.e., P. manokwari is present) on Chichijima, Ogasawara (Bonin) Islands. We found that over 50 and 90 percent of the snails were dead after 3 and 11 d, respectively, and that the main cause of mortality was predation by P. manokwari.     

云南省4种陆生贝类的营养成分分析

报道了云南省4种陆生贝类即褐云玛瑙螺(Achatina fulica)、金平坚螺(Camaena jinpingensis)、勐仑隐带螺(Cryptozona menglunensis)、勐仑环口螺(Cyclophorus menglunensis)的营养成分,并与猪肉、牛肉、鸡肉的营养成分进行比较。结果表明,这4种陆生贝类的蛋白质含量高,脂肪和糖类含量低,含有丰富的维生素和钙、磷、铁等无机元素,可作为优质保健食品进一步开发利用。     

The Fossil Record of Shell Boring by Snails

The predatory boring habit common to many recent snails probablyarose first in the Polinicinae (Naticacea) during Upper Cretaceous(Cenomanian) times (100 million years B.P.) . In the fossilrecord the frequency of bored shells increasesgreatly in rocksof latest Cretaceous age and becomes more widespread duringearly Tertiary times coincident with the major diversificationof the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show thesame characteristics of preference of penetration in one pelecypodvalve rather than the other or in position of the boring siteon the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 millionyears old) that have previously been attributed to gastropodpredation are herein attributed to other but unknown boringorganisms. In part these borings are not accepted as evidence of Paleozoicgastropod predation because it necessitates: (1) Postulationof the separate development of a boring habit ith its concomitantdevelopment of an accessory boring organ in a groupwhose descendantsare all herbivores, and (2) The development of such a habithundreds of millions of years before the appearance of any relativesof present day borers.     

Land Snails as a Diet Diversification Proxy during the Early Upper Palaeolithic in Europe

Despite the ubiquity of terrestrial gastropods in the Late Pleistocene and Holocene archaeological record, it is still unknown when and how this type of invertebrate resource was incorporated into human diets. In this paper, we report the oldest evidence of land snail exploitation as a food resource in Europe dated to 31.3-26.9 ka yr cal BP from the recently discovered site of Cova de la Barriada (eastern Iberian Peninsula). Mono-specific accumulations of large Iberus alonensis land snails (Ferussac 1821) were found in three different archaeological levels in association with combustion structures, along with lithic and faunal assemblages. Using a new analytical protocol based on taphonomic, microX-Ray Diffractometer (DXR) and biometric analyses, we investigated the patterns of selection, consumption and accumulation of land snails at the site. The results display a strong mono-specific gathering of adult individuals, most of them older than 55 weeks, which were roasted in ambers of pine and juniper under 375°C. This case study uncovers new patterns of invertebrate exploitation during the Gravettian in southwestern Europe without known precedents in the Middle Palaeolithic nor the Aurignacian. In the Mediterranean context, such an early occurrence contrasts with the neighbouring areas of Morocco, France, Italy and the Balkans, where the systematic nutritional use of land snails appears approximately 10,000 years later during the Iberomaurisian and the Late Epigravettian. The appearance of this new subsistence activity in the eastern and southern regions of Spain was coeval to other demographically driven transformations in the archaeological record, suggesting different chronological patterns of resource intensification and diet broadening along the Upper Palaeolithic in the Mediterranean basin.     

Intraflagellar Transport 80 Is Required for Cilia Construction and Maintenance in Paramecium tetraurelia

Intraflagellar transport (IFT) represents a bidirectional dynamic process that carries cargo essential for cilia building and the maintenance of ciliary function, which is important for the locomotion of single cells, intracellular and intercellular signalling transduction. Accumulated evidence has revealed that defects in IFT cause several clinical disorders. Here, we determined the role of IFT80, an IFT‐B protein that is mutated in Jeune asphyxiating thoracic dystrophy. Using the RNAi method in the ciliate Paramecium as model, we found that loss of IFT80 prevents cilia biogenesis and causes strong cell lethality. A specific antibody against IFT80 was also prepared in our study, which labelled IFT80 in cilia of Paramecium. GFP fusion experiments were performed to illustrate the dynamic movement of IFT‐A and IFT‐B proteins in cilia of Paramecium; then, we found that the depletion of IFT80 in cells prevents IFT‐A and IFT‐B proteins from entering the cilia. Our results showed the distribution change of other IFT proteins in cells that were depleted of IFT80, and we discuss the possible roles of IFT80 in Paramecium.     

Integrated Control of Snails

Snails are vectors of several important diseases and parasitesof man, especially schistosomiasis. They can be killed withchemicals such as copper chloride, sodium pentachlorophenate,organic tin derivatives, or niclosamide. Biological controlmethods include the use of predators such as crayfish, leeches,other snails, ducks, or geese, and the use of parasites suchas nematodes and certain Protozoa. Management, practices havealso been recommended. These include cleaning ditches, buildingthem with concrete sides or covering them so that plants —the food of snails — will not grow in them, or drainingditches periodically to kill the snails. However, some molluscicidesmay kill the nitrogen-fixing algae which help fertilize ricepaddies, and thermal pollution may raise the temperature ofstreams and estuaries in the temperate zone enough so that tropicaland subtropical schistosomes may be able to propagate. Moreresearch is needed to develop the ideal methods of controllingsnails.     

Irish Cepaea nemoralis Land Snails Have a Cryptic Franco-Iberian Origin That Is Most Easily Explained by the Movements of Mesolithic Humans

The origins of flora and fauna that are only found in Ireland and Iberia, but which are absent from intervening countries, is one of the enduring questions of biogeography. As Southern French, Iberian and Irish populations of the land snail Cepaea nemoralis sometimes have a similar shell character, we used mitochondrial phylogenies to begin to understand if there is a shared “Lusitanian” history. Although much of Europe contains snails with A and D lineages, by far the majority of Irish individuals have a lineage, C, that in mainland Europe was only found in a restricted region of the Eastern Pyrenees. A past extinction of lineage C in the rest of Europe cannot be ruled out, but as there is a more than 8000 year continuous record of Cepaea fossils in Ireland, the species has long been a food source in the Pyrenees, and the Garonne river that flanks the Pyrenees is an ancient human route to the Atlantic, then we suggest that the unusual distribution of the C lineage is most easily explained by the movements of Mesolithic humans. If other Irish species have a similarly cryptic Lusitanian element, then this raises the possibility of a more widespread and significant pattern.     

Transport of Oxygen by the Blood of the Land Crab, Gecarcinus lateralis

Parameters relating to transport of oxygen were measured inthe pericardial blood and venous outflow from the first walkingleg of Gecarcinus lateralis. O₂-equilibrium curves of the hemocyaninof G. lateralis were found to be sigmoid and, at 27°C andpH 7.45, to have a half-saturation pressure of about 17 mm Hgoxygen. Average partial pressures of oxygen as measured by O₂-electrodewere 32 mm Hg in pericardial blood and 9 mm Hg in the venoussamples. Analysis of the O₂-content in corresponding samplesby the Van Slyke technique revealed an average of 2.17 volumes% O₂-capacity for whole blood, 1.45 volumes % for pericardialblood, and 0.61 volumes % for venous blood. Estimates basedon the Van Slyke analyses indicated an average pO₂ of 29 and14 mm Hg in pericardial and venous samples, respectively. Thesefigures agree fairly well with those obtained by means of O₂-electrodes.Of the oxygen carried to the tissues, about 94% is carried asoxyhemocyanin and about 6% is carried in physical solution.As the blood passes through the gills, the hemocyanin, on anaverage, becomes 80–85% saturated with oxygen and returnedfrom the tissues 18–45% saturated with oxygen. These resultsindicate that the blood of G. lateralis has a higher O₂-capacitythan the blood of most other decapod crustaceans for which similarinformation is available. In addition, the blood of G. lateralistransports more oxygen to the tissues per unit volume than doother crustacean bloods.     

The Decimation of Endemic Hawai'ian Tree Snails by Alien Predators

Endemic terrestrial tree snails of the Hawai'ian Islands, likethose of other oceanic islands and even some continental areas,are extremely sensitive to disturbance because of their lowpopulation numbers and small geographic ranges. Like many otherplants and animals of oceanic islands, they have evolved nodefenses against introduced predators and competitors. The rangeof Achatinella mustelina, a tree-snail species found only ina short mountain range on the island of O'ahu, typifies thisproblem. Mark-recapture studies at two field locations revealthat the snails exhibit slow growth andlate maturity (3–5years). Fecundity is estimated at about 7 offspring per adultper year. The young are born live at about 4.6 mm. Populationgrowth typically depends on considerable longevity (> 10years). Demographic effects of the depredations by alien predators,rats and a North American predatory snail, Euglandina rosea,were documented in two long-term study sites. The predatorysnail eats all sizes of A. mustelina and can rapidly drive populationsto extinction (less than one year). Rats tend to select largersnails as prey and may leave an area before destroying all ofthe prey snails present; while reproductive output is temporarilydestroyed, populations may survive. Actions necessary to conserveHawai;ian tree snails, or indeed any group of relatively sedentaryinvertebrates with small species ranges, must include predatorabatement, but also preservation and restoration of sufficientlyarge and complex forest habitats that the invertebrates mayfind refuge from alien predators.     

RNA interference by feeding in Paramecium.

RNA interference can be induced very efficiently by feeding the ciliate Paramecium with bacteria engineered to express double-stranded RNA, opening the possibility of large-scale functional screening in this unicell.     

Calcium current activated by cooling in Paramecium

The cooling of deciliated Paramecium cells induced a transient Ca current and its amplitude depended on the rate of the temperature drop. The amplitude of the Ca current was increased by the addition of Ca²⁺ to the bath solution in a concentration-dependent manner, whereas Ni²⁺, Co²⁺, Mn²⁺ and Mg²⁺ each reversibly inhibited the Ca current in a concentration-dependent manner with apparent dissociation constants of 0.52, 0.66, 0.67 and 2.17 mmol · l⁻¹, respectively. The Ca current was also inhibited reversibly by amiloride, with a dissociation constant of 0.32 mmol · l⁻¹. The Ca current was desensitized by repetitive cooling. The amplitude of the Ca current at the second cooling was smaller than that at the first cooling when the interval was short, but recovered as the interval increased. Replacing extracellular Ca²⁺ with equimolar Sr²⁺ or Ba²⁺ did not significantly affect the amplitude of the current response to cooling, but it accelerated the rate of recovery from desensitization and slowed the decay of the current response. These results suggest that the desensitization and the inactivation of the Ca current may involve a Ca²⁺-dependent pathway. Accepted: 8 March 1998     

Binding of Ca ions by Paramecium caudatum

Binding of ⁴⁵Ca by live Paramecium caudatum was determined under various external ionic conditions. It was found that calcium uptake was separable into at least two components, a rapid and a slow one. The rapid component was influenced by the presence of certain other ions in a manner which agrees with the law of mass action. It appears that an ion exchange system may be involved in a binding equilibrium established between Paramecium, Ca⁺⁺, and certain other ions. K⁺, Rb⁺, and Ba⁺⁺ in the equilibrium medium are among those ions which inhibit calcium uptake. It is proposed that liberation of Ca⁺⁺ from binding sites on Paramecium by an exchange reaction with competing ions is the first step in the mechanism of ciliary reversal in the response to external application of these ions.     

Boring of Shell by Caobangia in Freshwater Snails of Southeast Asia

Giard (1893) described Caobangia billeti, a freshwater sabellidpolychaete, based on material collected in what is now northernNorth Vietnam. Up to the present time it had not been re-collectedand Giard's observations that it is hermaphroditic, that itseggs undergo internal development, and that, rather than havinga posterior terminal anal opening, the anus opens far forward,have been questioned from time to time. Recently collected material, as well as older material in thecollections of the Division of Molluscs, Museum of Natural History,Smithsonian Institution, has allowed the confirmation ofGiard'sfindings and the observation of the burrows of Caobangia in22 species of molluscs from fast-moving streams in Ceylon, northernIndia, Assam, Burma, Thailand, Laos, Java, Sabah, and variousof the Philippine Islands. Burrowing in snail shells appears to take place subsequent tolarval metamorphosis as youngindividuals grow posteriorly froma capsule-like structure through the periostracum and into thecalcium carbonate of the snail shell. There appears to be nodifferentiated area of the worm which can be implicated as thesite of acidic secretions, and the setae of the worms seem notto be unusually worn, as would be the case if they were usedto wear away the shell material.