The structure of the cutaneous pedal glands in the banded snail Cepaea hortensis (Müller, 1774)

Abstract

Although gastropods have been crawling through the ocean and on the land for 60 million years, we still know very little about the sticky mucus produced in their foot. Most research has been focused on marine species in particular and, to a lesser extent, on the well-known terrestrial species Arion vulgaris and Cornu aspersum. Within this study, we aim to characterize the foot anatomy of a smaller representative of the family Helicidae, the banded snail Cepaea hortensis. We are particularly interested in the microanatomy of the foot glands, their position, and the histochemical nature of their secretory content. Characterization of the dorsal foot region of Cepaea hortensis reveals four glands, differing in their size and in the granules produced. Histochemically, three of them react positively for sugars (PAS staining and lectin affinity tests for mannose, glucose and N-acetyl-d-glucosamine) and acidic proteins (positive Alcian blue and Toluidine blue staining), indicating the presence of acidic glycosaminoglycans. The fourth gland type does not react to any of these dyes. The ventral pedal region includes two different gland types, which are positive for the presence of acidic glycoproteins, with a lectin affinity for mannose only. A comparison with Helix pomatia indicates differences regarding the number of glands and their contents. In Helix, only three gland types are described in the dorsal region of the foot, which show a similar granular appearance but nevertheless differ in their chemical composition. Congruently, there are two gland types in the ventral region in both species, whereas in Helix an additional sugar moiety is found. This raises the question whether these differences between the pedal glandular systems of both helicid species are the result of protection or size-related adaptations, as they occur in the same habitat.

Characterization of the Arion vulgaris pedal gland system

“…Currently, the high levels of potassium and chlorine found locally in the ventral and lateral mucus in Arion vulgaris (present study), as well as in the two helicid species examined earlier (Greistorfer et al, 2017;von Byern et al, 2018), cannot be explained. Analyses of the dorsal mucus of H. pomatia indicate that the high concentrations of potassium and magnesium are not exclusively components of the haemolymph, but are also released by the epithelial gland cells (Burton, 1965).…”

“…The aim of the current study of the lateral and ventral pedal glands in Arion vulgaris is to determine their secretory content histochemically and by lectin affinity tests. A comparison with earlier studies on Helix pomatia and Cepaea hortensis (Greistorfer et al, 2017;von Byern et al, 2018) is expected to show structural and chemical differences in the gland systems and mucus of these three common European terrestrial gastropods.…”

“…Although gastropod mucus appears to offer a range of industrial applications, surprisingly little is known about the mucus‐producing glands in this group of molluscs. In an earlier study on the pedal gland system in the helicid species Helix pomatia and Cepaea hortensis , we reported differences concerning gland number, size, and content (Greistorfer et al, 2017; von Byern et al, 2018). While in Helix three different glands were observed in the dorsal epithelium (Greistorfer et al, 2017), in Cepaea four glands could be distinguished in the same location (von Byern et al, 2018).…”

“…In arionid species, it is proposed that the ventral (trail) mucus for locomotion is not only produced by the ventral gland types, as been supposed for the helicid species (Greistorfer et al, 2017;von Byern et al, 2018). Additionally, the suprapedal gland system, located within the ventral body cavity, contributes to the secretion of trail mucus (Barr, 1927;Wondrak, 2012).…”

Hemolymph of molluscan origin: from biochemistry to modern biomaterials science

“…One of the novel directions in the utilization of molluscan shells is based on their demineralization [20] and the isolation of organic matrices known as conchixes [21]. Some other products of molluscan origin, for example, molluscan slime (mucus), have found applications in the pharmaceutical, bioengineering and cosmetic industries [16,[22][23][24]. Undervalued over the years, molluscan hemolymph is also now recognized as a potential source of biomacromolecules (peptides) with antimicrobial, antiviral, antifungal, and anticancer activity.…”