Mucus Trails Research Articles

Biochemical differences between trail mucus and adhesive mucus from marsh periwinkle snails.

The composition of the adhesive form of marsh periwinkle mucus was compared to the trail mucus used during locomotion. The trail mucus consists primarily of large, carbohydrate-rich molecules with some relatively small proteins. In contrast, the adhesive mucus has 2.7 times as much protein with no significant difference in carbohydrate concentration. The resulting gel has roughly equal amounts of protein and carbohydrate. This substantial increase in protein content is due to the additional presence of two proteins with molecular weights of 41 and 36 kD. These two proteins are absent from the trail mucus. Both proteins are glycosylated, have similar amino acid compositions, and have isoelectric points of 4.75. This change in composition corresponds to an order of magnitude increase in tenacity with little clear change in overall concentration. The difference between adhesive and non-adhesive mucus suggests that relatively small proteins are important for controlling the mechanics of periwinkle mucus.

Do reproductive strategy and breeding season influence the presence of mate recognition in the intertidal snail Littorina?

Summary To test the assumption that littorinid snails do not discriminate between mates prior to copulation, I studied mate recognition behaviour in two species of Littorina on Swedish rocky shores: L. littorea (which has pelagic development and a distinct reproductive season) and L. saxatilis (non-pelagic development; reproduces throughout the year). Copulating pairs were sampled in five populations of each species to determine the occurrence of maladaptive (male-male or male-juvenile) matings. To complement the field sampling I did laboratory experiments on mucous-trail following, to reveal possible discriminating behaviour among potential mates when following mucous trails. In L. littorea about 5% of copulating pairs were between males, while in L. saxatilis, 33–38% were male-male or male-juvenile pairs. In contrast to L. littorea, this study showed that males of L. saxatilis did not discriminate between sexes from mucous trails, but followed any mucous trail (irrespective of sex of marker snail) for longer than females did. Thus, mate recognition behaviour by trail following can explain the difference in the proportion of maladaptive mating pairs between the two species studied. Among the 19 recognized species of the snail Littorina, nine show pelagic larval development, while 10 have direct, non-pelagic development. From the literature a clear relationship between reproductive strategy and the presence or absence of breeding season in Littorina snails was found. Species with pelagic development always have a distinct reproductive season, while species with non-pelagic development either reproduce throughout the year, or show variation between regions in seasonal or non-seasonal reproduction. The hypothesis that reproductive strategy and breeding season may influence the presence of mate recognition in Littorina snails is discussed.

Interaction of mucus with freshly neutralised aluminium in freshwater

This study examined the interaction of mollusc trail mucus, and its biochemical constituents, with environmentally relevant concentrations of freshly neutralised aluminium (Al) in freshwater. Upon neutralisation Al starts to polymerise. In the presence of mucus the metal is rapidly localised into the hydrated mucus gel resulting in a likely reduction of its overall degree of polymerisation. A simple Al binding assay identified large- M r glycoconjugates as major Al-complexing molecules in mucus. Subsequent isolation and purification of these mucus glycoconjugates showed the metal readily bound to the carbohydrate portion and, in particular, to acidic components such as those containing carboxyl functionality. It is suggested gel-forming extracellular glycoconjugates play a crucial role in preventing the diffusion of Al into biological systems and thus serve to maintain metabolic homeostasis.

The Role of an Organic Slime Matrix in the Formation of Pyritized Burrow Trails and Pyrite Concretions

Abstract Sandstones from the Black Island member of the Winnipeg Formation (Ordovician) contain a variety of early diagenetic iron sulfide morphologies, including elongate concretions of variable length. Examination of sandstone samples with X-radiography reveals that these concretions, now consisting of pyrite, are associated with burrows. Detailed textural examination of the pyrite shows an anomalously loose packing of sand grains within these concretions, and also suggests that iron sulfide nucleation commenced at multiple sites in what must have been a stiff matrix. Compositional data acquired by electron microprobe indicate that the iron sulfides did not replace fecal matter left behind by the burrower. Sulfur isotope data point to bacterial sulfate reduction as a sulfide source, corroborated by fossilized bacterial remains within the concretionary pyrite. Mucus and slime trails of marine benthos were probably important for early diagenetic pyrite production in these sediments; they can be considered...

Functional and ecological aspects of the mucus trails of the intertidal prosobranch gastropod Littorina littorea

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 239:129-137 (2002) - doi:10.3354/meps239129 Functional and ecological aspects of the mucus trails of the intertidal prosobranch gastropod Littorina littorea M. Edwards*, Mark S. Davies Ecology Centre, University of Sunderland, Sunderland SR1 3SD, United Kingdom *Present address: CLSM, Porter Building, University of Newcastle, Newcastle-upon-Tyne NE1 7RU, UK. E-mail: m.edwards@ncl.ac.uk ABSTRACT: It has been suggested that some gastropods might utilise pedal mucus trails as a source of nutrition. Despite much work, there has been little attention on the ecological consequences of such a strategy. Here we aimed at determining the value of mucus trails to snails by investigating (1) snail reaction to naturally aged conspecific mucus trails and (2) the effect of starvation on trail-following behaviour. The mucus trails of Littorina littorea (L.) adhered microalgae in the laboratory but this ability began to diminish after the trails had been exposed on-shore for >1 tidal cycle. Natural floral components of trails were greatest for up to 4 tidal cycles of exposure and then began to diminish. If trails are to be used for foraging purposes, snails would gain most benefit by utilising them while relatively fresh. Correspondingly, snails readily responded to fresh mucus trails, but after 20 tidal cycles only 3 of 24 did so. As the mucus was still present we conclude that some unknown cue is present enabling snails to discriminate trails by their age. Despite previous work to the contrary, no evidence of preference for following trails in a particular direction was found and we conclude that trail following in our snails was not related to mate searching or the formation of aggregations. The starvation level of snails (up to 4 d) did not affect their foraging behaviour in the laboratory. However, snails followed the trails of starved snails for significantly shorter distances than those of fed snails, suggesting a coding of starvation level in the trail mucus. Choices about whether to trail follow may be based on how well fed a conspecific is and how old a trail is ‹ following a fresh trail would increase the likelihood of encountering a conspecific and may have a nutritional benefit if the trail is to be grazed. Previous work on trail following should be re-evaluated in the light of these findings. KEY WORDS: Trail following · Foraging · Mucus · Littorina littorea · Behaviour · Microalgae Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 239. Online publication date: August 23, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

A Laboratory study on the visual and chemical orientation of the gastropod Nerita Fulgurans Gmelin, 1791

Behavioural responses of the gastropod Nerita fulgurans Gmelin, 1791 to flat black rectangles and intraspecific mucus trails were measured in a circular arena. Snails were tested in water either in the presence or absence of chemicals generated from a predator gastropod, Chicoreus brevifrons (Lamarck, 1822). The test hypothesis was that this snail has different behavioural responses as result of visual and chemical cue integration. Nerita fulgurans has the capacity to orient to solid targets subtending angles larger than 10° and follow its own mucus trails. In water conditioned by the predator C . brevifrons, snails exhibited an avoidance response when 10°, 20° and 45° sectors were presented, demonstrating an integration of chemical and visual information. The simultaneous presentation of two orienting cues (black sectors and mucus trails) was tested to determine the nature of the interaction. When the two cues were oriented in the same direction there was no effect. When the two cues were presented from directions 180° apart a preference for visual cues over mucus trail cues was evident when the visual angle of the visual cue subtended angles greater than 90°. This result demonstrates a hierarchical usage of the orienting references.

Effects of trematode parasitism on the behaviour and ecology of a common marine snail (Littorina littorea (L.)).

Cryptocotyle lingua (Creplin) is a digenean trematode parasite of the littoral prosobranch gastropod Littorina littorea (L.). The literature suggests the snails become infected by grazing guano of the final host, the herring gull, Larus argentatus Pontoppidan. The parasite emerges from the snail as free-swimming cercariae. Interactions between the snail and the parasite at cellular and life-history levels are well established, but little is known of the influences the interaction has on the behaviour and the ecology of the snail. We tested the response of the snail to encounters with cercariae, examined the longevity of the guano on-shore and tested the responses of the snail to encounters with guano. Over half the L. littorea tested were able to detect both cercariae and a filtered homogenate of cercariae in conspecific mucus trails, approximately one-third of animals refusing to cross the treatments. Chemoreception by the mouth or foot is considered the most likely means of detection. Guano samples (mean weight 3.22 g) naturally deposited at approximately mid-tide level were completely washed away by one tidal inundation. We consider this period too brief to allow for ingestion of eggs in guano by the snail. Further, snails would not cross guano placed in conspecific trails. Most snails would not cross guano diluted by 10(3)x(10 mg ml(-1)) and some snails could still detect guano diluted by 10(6)x(10 &mgr;g ml(-1)), though all were prepared to cross it. Detection of guano is again believed to be by chemoreception by the mouth or foot. These results are discussed in terms of the mating and aggregating behaviour of L. littorea. Ingestion of the parasite by L. littorea is likely to take place once the guano has washed away as the eggs are negatively buoyant in seawater and may adhere to rock (biofilm) or algal fronds which may be grazed by the snail.

Aeromonas Infection After Medicinal Leech Therapy: Case Reports and Review of the Literature

Aeromonas Infection After Medicinal Leech Therapy: Case Reports and Review of the Literature

Mating system and alternative male mating tactics in the grass goby Zosterisessor ophiocephalus (Teleostei: Gobiidae)

Peculiar fertilization dynamics, with males releasing sperm in mucous trails lasting several hours, characterize some demersal spawning fish. The mating system was investigated in a natural population of one of these species: the grass goby Zosterisessor ophiocephalus (Pallas, 1814), a large coastal goby inhabiting seagrass meadows in shallow brackish water. Adult males ranged in size from 7.4 to 23 cm total length, but only larger ones were observed to dig and defend a burrow, where they performed parental care on eggs laid by one to several females. Field observations together with analyses of age, sperm production, trail sperm content and sperm competition tests indicated the occurrence of alternative male mating tactics, likely the expression of an ontogenetic gradient. Larger males are older than smaller ones, and while the former are territorial, the latter “sneak” territorial male spawns. The ejaculate characteristics indicate that grass goby males have functionally polymorphic spawns: in fact sperm trails of larger males last longer and release fewer sperm than those of smaller males. Sperm production over several days is more constant in larger than in smaller males, but the total number of sperm released is higher in the latter. The influence of seminal fluid in the functional intraspecific variability in sperm release in this species is discussed.

Sperm delivery and egg production of the simultaneously hermaphroditic land snail Arianta arbustorum exposed to an increased sperm competition risk

Summary Sperm competition theory predicts that males exposed to an increased risk of sperm competition should maximize fertilization prospects by inseminating more sperm per ejaculate. We designed a laboratory experiment to examine the effect of increased sperm competition risk on male and female reproductive traits in individuals of the simultaneously hermaphroditic land snail Arianta arbustorum. Courtship behaviour, spermatophore size and number of sperm delivered were not influenced by a higher sperm competition risk. However, snails constantly exposed to mucous trails of conspecifics deposited more egg batches than snails denied any cues from conspecific mucous trails. On the individual level, the number of sperm delivered was positively correlated with the number of eggs produced. This finding contradicts the basic prediction of sex allocation theory that there is a trade-off between resources allocated to male and female function in simultaneous hermaphrodites. Most probably this trade-off may only occur if resources are limited.

Modern mucociliary creeping trails and the bodyplans of Neoproterozoic trace-makers

The bulk of Neoproterozoic trace fossils can be interpreted as horizontal creeping trails produced by minute vermiform organisms moving on or just beneath the seafloor or under algal mats. We have investigated the formation of trails by living cnidarians and platyhelminths that creep by cilia on mucus ribbons. These relatively simple metazoans produce trails that are similar in size and morphology to some Neoproterozoic traces, owing to the entrainment of sediment within their mucus trails. Thus a mucociliary locomotory system provides sufficient means to form some types of Neoproterozoic traces. It follows that the body architectures of the Neoproterozoic trace-makers may have been quite simple, though complex bodyplans are, of course, not ruled out. Thus, the use of Neoproterozoic trace fossils to constrain the time of origin of bilaterians or of any crown-group bilaterian taxon remains questionable.

Role of mucus trails and trail-following in the behaviour and nutrition of the periwinkle Littorina littorea

Gastropod locomotion typically involves the deposition of a mucus trail. This trail can be energetically costly, and its producer could defray this cost if the trail were to perform some post-deposition function. Here we report laboratory experiments aimed at assessing the potential role in nutrition of the mucus trail of the common intertidal periwinkle Littorina littorea (L.). Mucus trails bound more microalgal cells from suspension than did a glass substratum, microalgal densities increasing with period of exposure to the suspension up to ∼5-8 h. After this time adhesion was less (but still greater than to glass). Amphora coffeaeformis (pennate diatom) adhered in greater densities than did Tetraselmis suecica (flagellate prasinophyte). Mucus trails containing microalgae of both species (∼ 50 to 100 cells mm -2 ; approximatly the conditions on-shore) induced a greater degree of trail-following than did bare trails. Individuals followed conspecific trails longer than they did their own trails. Winkles moved significantly slower on bare mucus trails (mean = 0.35 mm s -1 ) than on glass (0.68 mm s -1 ), though the addition of microalgae to mucus increased the speed of the winkles, A. coffeaeformis significantly so. Feeding rate (rate of radular rasping) was also significantly increased on trails containing A. coffeaeformis (mean = 17.8 bites min - 1 ) and T. suecica (12.9 bites min -1 ) in comparison to control trails (4.3 bites min -1 ), where a form of searching behaviour occurred. Microalgae embedded in mucus were seen to enter the mouth. Only 3 out of 40 periwinkles showed any radular activity on glass. Following the passage of a winkle, the density of A. coffeaeformis was reduced by ∼38% and that of T. suecica by 43%. Winkles can clearly exploit food (microalgae) in conspecific mucus trails and in doing so modify their trail-following and feeding behaviour. Thus trail-following seems inextricably linked to nutrition. Since much of the intertidal is likely to be covered with a layer of mucus - or its degradation products - those experiments on trail-following that used 'clean' substrata were not representative of the field. Distribution patterns of both L. littorea and benthic microalgae might be shaped by the ability of mucus trails to bind microalgae and by their subsequent exploitation by the grazer.

Limpet Mucus as a Depuration Route and Potential Biomonitor

Metal granules have previously been found in the mucus trails of gastropods. We hypothesised that such metals could be a marker of environmental pollution and that mucus may constitute a depuration route. We investigated this using limpets from sites in north-east England. Mucus production generally showed a significant logarithmic correlation with flesh dry weight of limpet but there was an up to 4-fold inter-site variation. Mucus production did not vary in any systematic way with metal content of either mucus or flesh. X-ray microanalysis revealed that Ca, Cl, S, K, P, Si, Mg and Fe were widely distributed in mucus across sites. Aluminium, Cr, Cu, Mo and Ni were also detected, but at lower frequencies. Ion chromatography analysis of metals in mucus (Cd, Co, Cu, Ni, Pb, Zn) indicated that Pb was dominant. In general, metals with levels>10 μg g-1 were found at sites close to the polluted Tees estuary. In limpet flesh, the dominant metal was Fe and again metal levels were generally highest close to the Tees. Where comparisons can be made, metal levels in mucus were typically higher (by up to 2000×) than those in the flesh. Metal levels in mucus showed little correlation with flesh dry weight or with metal levels in limpet flesh. The high levels of Pb and other metals in mucus, relative to the flesh, may suggest that mucus functions as a depurator, animals releasing as much Pb per day in mucus as is stored within the flesh. Mucus has the potential for use as a non-destructive biomonitor that allows for repeat and instantaneous measurements.

Immunocytochemical Localisation of Glycosaminoglycan-Like Activity in the Mucus and Associated Tissues of Terrestrial Slug Species (Gastropoda: Pulmonata)

Indirect immunofluorescence assays were conducted on cryotome sections of four terrestrial slug species from three distinct phylogenetic groups, Arion ater (L.), Arion hortensis (Férussac), Tandonia (Milax) budapestensis (Hazay), and Deroceras reticulatum (Müller) using monoclonal antibodies for two glycosaminoglycans (GAGs), heparan sulphate, and chondroitin sulphate. Specific staining for a heparan sulphate-like component was demonstrated in the foot and tail regions of each species and was particularly intense in A. ater and A. hortensis, notably in the epidermis and associated mucus-like material, and in mucus-like material from the pedal gland region of the latter species. Subsequent studies with A. ater confirmed the presence of heparan-sulphate–like activity in the caudal gland duct region. No evidence of specific staining for chondroitin sulphate-like activity was found in any of the slug species. This work suggests that a specific GAG, or a group of closely related GAGs, is a common component of mucus in a range of slug species and of different types of mucus, including trail (pedal) mucus and the more viscous mucus produced by the caudal gland.

Survival and growth rates of post-larval abalone Haliotis discus hannai fed conspecific trail mucus and/or benthic diatom Cocconeis scutellum var. parva

The settlement rate and growth rate of post-larval Haliotis discus hannai were compared in the laboratory when raised on the following three experimental substrata. (1) Mucus: trail mucus of juvenile H. discus hannai (3 cm in shell length); (2) diatom: monoculture of the benthic diatom Cocconeis scutellum var. parva; (3) diatom and mucus: C. scutellum var. parva coated with trail mucus of juvenile abalone. The mean percentage of larvae that settled were 48.7 on mucus, 98.0 on diatom, and 97.3% on diatom and mucus substrata. All post-larval abalone that settled on the mucus substratum died by the end of the third week, with a mean shell length during the third week of 711.9 μm. Individuals on the diatom substratum died by the end of the second week, with a mean shell length during the second week of 481.6 μm. Post-larvae on the diatom substratum and on the mucus substratum did not reach 800 μm in shell length; the size at which they are able to utilize the cell contents of C. scutellum var. parva. In contrast, on the diatom and mucus substratum, 70.0% of the individuals survived to the end of the experimental period (4 weeks). Individuals on the diatom and mucus substratum grew well over the entire experimental period and reached approximately 1.4 mm in shell length 4 weeks after settlement. Post-larvae reared on the diatom and mucus substratum grew to more than 800 μm by feeding initially on the trail mucus of conspecific juveniles, which was probably supplemented with extracellular diatom mucus and decomposed cells of the diatom. Once they reached about 800 μm, they were able to access diatom cell contents.

Role of the cephalic tentacles in trail following by Littoraria irrorata (Say)

Gastropod molluscs deposit mucous trails on surfaces over which they crawl Littorinids, as well as certain other gastropods, follow conspeafic mucous trails in the direction in which they were laid, that is '• The stimuli and sense organs used by snails to determine mucous trail polarity are not known; however, six mechanisms of trail polarity detection have been suggested in the literature' Of these, the hypothesis which has received the most attention is that trails possess a concentration macrogradient of a volatile chemical which is detectable across the points of contact of a pair of sensory structures UJJi The assumption that polarity detection involves a concentration macro-gradient has been tested by experimentally reversing the assumed concentration macro-gradient in trails of Littoraria irrorata} Snails still travelled against the assumed gradient in favour of the actual direction of trail deposition. Furthermore, snails exhibited random directional choices when trail polarity was rendered ambiguous for all potential cues except for a hypothetical concentration macro-gradient Thus, it was concluded that a concentration macro-gradient is not involved in trail polarity detection in L. irrorata Further evaluation of hypotheses for the mechanism underlying trail polarity detection would be aided by knowledge of the sensory basis for this behaviour. The paired lips of Euglandmd and the anterior lateral folds of Navanax' are reportedly involved in detecting the trails of prey and mates, but neither species can apparently detect trail polarity.' The oral lappets are supposedly involved in detecting mucous trails in Onchidium, which can detect trail polarity.' As a Littoraria irrorata progresses along the substratum, the cephalic tentacles alternately move up and down, contacting the substratum with the ventral surface of the tentacle tips an average of 16-20 times per minute under normal conditions. The paired cephalic tentacles of littorinids are known to be tactile and one of the sites where chemical detection of predator mucus is possible.' Thus, the cephalic tentacles are likely locations for sensory receptors involved in trail polarity detection. This report presents an experiment designed to examine the role of the cephalic tentacles of L. irrorata in

PRODUCTION OF MUCOUS GRANULES BY THE TERRESTRIAL SLUG ARION ATER L.

Mucous granules were obtained from mature Anon ater. Granules from the dorsal body, in modified slug Ringer solution, did not differ significantly in length from those taken from the animals ventral surface (mean length 6.75um ± 0.047, mean ± SEM, n = 180) but their widths were significantly smaller (1.18um ± 0.007 < 2.70jim ± 0.036, n = 90). Granules removed from the anterior, middle and posterior parts of each surface did not differ significantly in length or width. Individual granules burst in distilled water to absorb approximately 300 times their own volume of water. Regression analysis on swelling experiments using variable numbers of granules demonstrated that the number of granules was a significant predictor of the weight of swollen mucus. Mucus swollen from granules could be dned then reswollen in distilled water to achieve approximately 60% of its original swollen weight. These relationships were used to quantify granule incorporation into slug mucus trails. Active adult Anon ater in high humidity use approximately 0 6 x 10* granules to produce lcm2 of slug mucous trail with a fully swollen weight of approximately 3mg Slug weight was a significant predictor of the number of granules incorporated into the slug trail.

Crystalline calcium in littorinid mucus trails

Previous work has shown that the feet of terrestrial and freshwater snails are important in calcium regulation, often secreting granules of CaCO3. This phenomenon has not, until now, been observed in marine snails. Here we report the presence of CaCO3 granules in the trail mucus of Littorina littorea (L.), L. saxatilis (Olivi) and L. obtusata (L.) Fixed mucus trails on plastic coverslips were examined by X-ray microanalysis under the SEM. Of the single-metal granules observed in the mucus trails the most abundant were of calcium (means: L. littorea, 440 mm−2; L. saxatilis, 401 mm−2; L. obtusata, 348 mm−2) followed for each species by silicon (maximum mean density: L. saxatilis, 120 mm−2) and iron (maximum mean density: L. saxatilis, 65 mm−2) granules. Single-metal granules of Al, Ti, Mg and P were also found but only in the mucus trails of L. obtusata, perhaps reflecting its different collection site from the other two species. The mean size of the calcium granules showed significant interspecific variation (L. littorea, 1.32 µm diameter±0 08 µm, n = 143; L. saxatilis, 1.80 µm±0.12, n = 113; L. obtusata, 2.14 µm±0.09, n = 167). Most calcium granules (L. littorea, 80%, n = 35; L. saxatilis, 57%, n = 113; L. obtusata, 69%, n = 167) were attached to, or embedded within, microthreads of mucus which tended to run parallel to the direction of locomotion. The significance of this is unknown although it may imply that the CaCO3 granules are secreted with the mucus. It is concluded that calcium losses via this route are too small for pedal mucus to function significantly in ionoregulation of calcium. The calcium in the trail may therefore perform other functions, for example indicating trail polarity.

Mucous trail following in 2 intertidal nudibranchs

Gastropods are generally known to be able to follow mucous trails. They follow the trails of their own for homing (McFarlane 1981; Chelazzi et al. 1987), of the same species for mating (Townsent 1974) or of other species for predation (Paine 1963; Gonor 1967). But according to Cook (1977), "trail following may be widespread [but] it need not necessarily be a general feature of a gastropod's normal behavioural repertoire." Trail-following behavior in opisthobranchs, especially for mating, has been referred to in only a few studies (Hadfield & SwitzerDunlap 1984) and not certified experimentally. For example, Stylocheilus longicauda (SwitzerDunlap & Hadfield 1979) and Bursatella leachii pleii (Lowe & Turner 1976) were observed to follow conspecific trails in the field. Todd (1979) considered that Onchidoris bilamellata might find mates by following trails, but the results of his laboratory tests were inconclusive. Dendrodoris nigromaculata and D. nigra are common sponge feeders in the intertidal zone of southern Japan. They are annual species, as is common among nudibranchs, and are sometimes observed in aggregations during the spring mating season. As nudibranchs are simultaneous hermaphrodites, they need not distinguish the sex of other individuals for mating. In the present study, I examined whether they utilize water-borne substances of the same species or mucous trails to find their mate.

Trail following, speed and fractal dimension of movement in a marine prosobranch, Littorina littorea, during a mating and a non-mating season

We quantitatively studied movement behaviour in the gastropod Littorina littorea in laboratory experiments during periods of their non-mating season (November 1992) and their mating season (April–May 1993). Snails were collected in 1992 and 1993 from one boulder shore on the north west coast of Sweden. In a comparison between the two seasons (one non-mating and one mating) we measured trail complexity of unsexed snails using fractal dimesion, the degree of mucus trail following (coincidence index of marker and tracker trails) and average movement speed of marker and tracker snails. We found no differences in fractal dimension and coincidence index of trails between the two seasons. Tracker snails moved, however, significantly faster than marker snails during both seasons. This could not be explained by trackers, when locomoting, using the mucus trail deposited by the marker to increase their speed, since there was no correlation between coincidence index and tracker speed. During the mating season we also conducted trail complexity, trail following and speed experiments comparing the behaviour of males and females. There was no difference between males and females in the fractal dimension of movement, nor was there any difference between the mean speed of male and female snails, although male marker snails tended to move faster than female marker snails. Males tracking other males, females tracking other females and females tracking males followed trails about equally long distances (i.e., coincidence indices did not differ). In contrast, males following female mucus trails showed a significantly higher degree of trail following than the other sex combinations. This new finding may suggest that females of L. littorea release pheromones in their mucus trails and that males are able to identify them.