Morphology and function of the skin epithelium covering the giant keyhole limpet Megathura crenulata

Mucus-secreting epithelia protect marine gastropods from abrasive particles and microbes in seawater. We studied the morphology and function of the epithelium in the giant keyhole limpet Megathura crenulata. All exposed surfaces of the limpets were covered by a mucus-secreting, simple columnar epith...

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Bibliographic Details
Published in:Invertebrate biology 2018-06, Vol.137 (2), p.151-170
Main Authors: Martin, Gary G., Bailey, Abby K., Cohen, Seth, Loera, Yeraldi, Crooke, Anne M., Stamnes, Stephanie, Field, Naomi, Natha, Zain, Ramesh, Nisha, Rose, Kasey
Format: Article
Language:English
Subjects:
Additives
archeogastropoda
Atrophy
Bacteria
Cells
Chemical analysis
Cilia
Epithelium
Feet
Fixatives
Freshwater molluscs
immunity
Locomotion
Mantle
Marine molluscs
Megathura crenulata
Morphology
Mucous membrane
Mucus
Original Articles
Protective coatings
Regions
Seawater
Secretions
Shrinkage
Silt
Skin
Talc
Thickness
Tissue
Upper mantle
Vetigastropoda
Water analysis
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Summary:Mucus-secreting epithelia protect marine gastropods from abrasive particles and microbes in seawater. We studied the morphology and function of the epithelium in the giant keyhole limpet Megathura crenulata. All exposed surfaces of the limpets were covered by a mucus-secreting, simple columnar epithelium, in which most cells on the sole of the foot bore cilia, while the majority of cells on the side of the foot and three mantle regions bore microvilli. None of the coatings had antibacterial properties. The epithelium of the foot was distinct from that of other regions, in that the mucus secreted was used for locomotion and was left behind as the limpet moved. The glycocalyx bound to the microvilli of the mantle cells appeared to be clean in visual and SEM examinations, and attempts to enhance the binding of inert particles and bacteria were unsuccessful. Because studies have shown that standard tissue processing may cause artifactual shrinkage of mucous layers, cryostat sections and additives to standard fixatives were tested, but we found no change in the thickness of the mucous layers of the limpets compared to routinely processed tissues. Sloughing of the glycocalyx in vertebrate systems removes bound microbes, and alterations of the glycocalyx layers are associated with disease conditions. Sloughing of the glycocalyx on limpets was rarely observed. In one case, the outer mantle of the limpet was covered with silt and the glycocalyx appeared to be detaching. This process could be experimentally induced by dousing the outer mantle with talc particles. The types of secretory cells producing the mucus in each region of the skin were characterized using standard histological stains and lectin staining. Because analysis was hampered by their small size, classification of the types of secretory cells was based on TEM descriptions of granule morphology, which allowed for comparison to the secretory cells described from skin of the abalone. The possible roles of the numerous secretions, and the mechanisms of mucus production and loss, are compared to what is known in vertebrate systems and to our relative lack of knowledge regarding invertebrate systems.
ISSN:1077-8306
1744-7410
DOI:10.1111/ivb.12213