Vertical migration byCerithidea decollata(Mollusca, Potamididae): addition but not subtraction (original) (raw)
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Estuarine Coastal and Shelf Science, 2008
The vertical migration on mangrove trunks of the gastropod Cerithidea decollata was followed for 5 weeks, in a Kenyan mangrove. Most of the times, snails forage on the mud surface, during low tide, and climb back on trees well before the incoming tide. As soon as the sea retreats, the downward migration takes place and the snails spread again on the ground. The migratory behaviour of snails can vary widely, depending on the relative tide intensity, and different strategies can be exhibited. Individuals can spend several days on trees without migrating to the ground, around Spring Tides, or else, they might remain on the ground without bothering to migrate upwards, during Neap Tides, when the study area is not reached by the water. These irregular animal behaviours, relating to the complicated tide succession, can hardly be explained by the sole presence of an internal clock, and direct cues seem necessary to switch between different strategies, tuning the snails migratory behaviour to the actual local sea conditions.
Rhythmic vertical migration of the gastropod Cerithidea decollata in a Kenyan mangrove forest
Marine Biology, 2008
In Mida Creek, Kenya (3°20′S, 40°5′E), at high water, the snail Cerithidea decollata dwells on the trunks of mangrove trees (Avicennia marina), while during low water it migrates to the ground, foraging at various distances from the trunk, where it aggregates again well before the incoming tide. Snails from the upper shore level are 150–200 m distant from those living at the lower shore level and they cluster at lower heights on trunks. In any case, sufficient height is usually attained to avoid being submersed. An experiment was designed (February and October 2005), exchanging individuals from different shore levels subject to different tide regimes, in order to test whether snails rely on internal information or on external, direct cues, to adapt their behaviour to local conditions. Results show that C. decollata mostly rely on internal information, presumably based on an internal clock. When individuals from upper and lower shore levels were exchanged, their internal clocks continued to govern when to ascend the home trunk and how high to climb for five to six successive tides, after which the behaviour was reset to the new local conditions.
Cerithidea decollata: a snail that can foresee the future
Animal Behaviour, 2008
Individuals of Cerithidea decollata periodically migrate along mangrove trees, resting on the trunks during high water, and foraging on the surrounding muddy platform during low water. Groups, ranging from tens to hundreds of snails, aggregate on the trunks well before the incoming tide (1–2 h) at a level that will not be reached by the high tide, that is, from a few centimetres (around neap tides) to over 1 m (around spring tides) above the ground. We addressed two questions: (1) how can snails determine when to stop climbing and (2) how do snails determine the length of the path necessary to stop at that level. We used plastic pipes, 2 m long and 20 cm in diameter, along which snails crawled just as on their own trees. Experiments in which the pipes were lowered, raised or tilted indicated that snails were able to perform both tasks. Overloading the snails with lead weights showed that the estimate of the required travelling distance was probably related to the energy used to cover that distance. However, it was not possible to define how snails were able to establish the distance they needed to travel to avoid the incoming tide, although we were able to exclude any role of for visual cues or chemical marks present on substratum.
Migratory behaviour of the mangrove gastropod Cerithidea decollata under unfamiliar conditions
Journal of Experimental Marine Biology and Ecology, 2014
The mangrove gastropod Cerithidea decollata feeds on the ground at low tide and climbs trunks 2-3 h before the arrival of water, settling about 40 cm above the level that the incoming tide will reach at High Water (between 0, at Neap Tide, and 80 cm, at Spring Tide). Biological clocks can explain how snails can foresee the time of the incoming tide, but local environmental signals that are able to inform the snails how high the incoming tide will be are likely to exist. To identify the nature of these possible signals, snails were translocated to three sites within the Mida Creek (Kenya), 0.3-3 km away from the site of snail collection. The study sites had a much wider tidal range than the original site (up to 160 cm), were dominated by Rhizophora mucronata trees and uninhabited by C. decollata. If cueing signals were linked to the upper mangrove belt (site-specific signals), the Avicennia marina area, translocation should affect snail behaviour; conversely, we could conclude that information on the height of the incoming tide should be widely available within the whole creek (widespread signals), independently from cues linked to the home area and home site. Tests were performed by releasing the snails close to vertical plastic pipes (2 m high) following a standardized procedure. Results revealed that snails, even in such unfamiliar surroundings, climbed higher and earlier on pipes where the tide level would be higher, thus allowing rejection of the hypothesis of site specific signals. Where the tide exceeded 80 cm, however, snail effort was not sufficient to avoid submersion and snails had to climb higher. Hypotheses on widespread signals possibly involved in modulating the migratory behaviour of C. decollata are discussed.
Journal of Experimental Marine Biology and Ecology, 2014
In mangrove marshes in Florida, the marine snail, Cerithidea scalariformis, exhibits a tidally-induced climbing behavior in which snails forage on the substrate during low tides, then climb aerial roots of mangrove trees on incoming and high tides. Under field and laboratory conditions, we tested the conventional explanation that snails vertically migrate to avoid predators, and because populations of C. scalariformis are parasitized by a guild of larval trematodes, we quantified the additive effects of parasitism on climbing behavior. We found that snail climbing distance was significantly and positively associated with water height, with snails migrating 2.7 times higher during high tide than low tide. Climbing distance depended on the species of trematode infection, and differences in migration distance between low and high tides were reduced for two of the four trematode species, suggesting that parasitism can affect climbing behavior. In field and laboratory experiments with tethered snails, individuals experienced significant levels of predation 0-8 cm above the substrate surface, which declined substantially at heights above 16 cm. A laboratory experiment showed that in the presence of blue crabs, Callinectes sapidus, unparasitized snails climbed 53% higher than parasitized snails, and 37% higher than they would without the presence of a predator. Surprisingly, infected snails climbed the same distance in the presence or absence of a blue crab, suggesting that parasitism may physiologically affect a snail's ability to respond to predators. Our data show that predation and parasitism are significant driving forces behind the climbing behavior of C. scalariformis whereby parasitic infection may affect their interactions with marsh predators. Reduced climbing distance may be an adaptive benefit for the parasite that keeps snails closer to the mud surface, providing favorable conditions for free-swimming cercariae to find a second intermediate host, since cercariae can only be transmitted to the next host when the snail host is inundated. Thus, the migratory behavior of C. scalariformis is a behavioral adaptation to avoid predation and that body snatchers, such as larval trematodes, can greatly modify this behavior to increase their own evolutionary fitness.
Canadian Journal of Zoology, 2018
Understanding the relationship between the movements of animals and their environment is crucial for fisheries and species management. There is currently a lack of detailed information about the movement of slow-moving benthic species, especially for species of ecological or commercial importance. Here we document the relationship between diel movement and environmental parameters in a groundwater-fed coastal inlet for the queen conch (Lobatus gigas (Linnaeus, 1758)), an important fishery resource of the Caribbean region, using three-dimensional accelerometers and video cameras. Our results show immature queen conch (n = 9) spend most of their active time grazing, exhibiting two main distinct movements that we characterize as a leap and a drift that are mostly used to access new foraging resources. When overturned, they flip, producing a movement with the highest acceleration recorded to limit exposure and restore normal position. Movement patterns appear to be significantly affecte...
The Weierstrassian movement patterns of snails
Royal Society Open Science, 2017
Weierstrassian Lévy walks are the archetypical form of random walk that do not satisfy the central limit theorem and are instead characterized by scale invariance. They were originally regarded as a mathematical abstraction but subsequent theoretical studies showed that they can, in principle, at least, be generated by chaos. Recently, Weierstrassian Lévy walks have been found to provide accurate representations of the movement patterns of mussels (Mytilus edulis) and mud snails (Hydrobia ulvae) recorded in the laboratory under controlled conditions. Here, we tested whether Weierstrassian Lévy walks and chaos are present under natural conditions in intertidal limpetsPatella vulgataandP. rustica,and found that both characteristics are pervasive. We thereby show that Weierstrassian Lévy walks may be fundamental to how molluscs experience and interact with the world across a wide range of ecological contexts. We also show in an easily accessible way how chaos can produce a wide variety...
Estuarine, Coastal and Shelf Science, 2017
The Indo-West Pacific mangrove gastropod Cerithidea decollata feeds on the ground at low tide and climbs the trees (Avicennia marina) two hours before the arrival of water, settling well above the level that the incoming tide will reach at high tide (from 0 to 80 cm, depending on the tidal phase). In addition, it has been shown that these snails climb twice as high when translocated to lower shore sites (dominated by Rhizophora mucronata), where C. decollata is missing and the high water can reach 1.6 m instead of about 80 cm as within the snail home environment. The study assesses the possible role of chemical cues in the afore-mentioned behaviours. The hypothesis that snails may foresee the periodical tide level variation thanks to airborne chemical cues, possibly released by trees or sediments, has been rejected. On the other hand, airborne chemical cues released by R. mucronata may play a role in inducing snails translocated to low shore sites to climb much higher than control, allowing them to avoid submersion.