User:JonRichfield/Collocyte

Collocyte Collocyte is a term variously used in botany and zoology   in referring to cells that produce gluey substances, or that bind or capture prey or assorted objects with with gluey materials and structures, or that simply look smooth and gelatinous. Literally the word simply means "glue cell", and it has a number of poorly distinguished synonyms, such as colloblast.

Use in Botany
In English the term "collocyte" (or, less formally, "glue cell") is uncommon in botanical publications, though it appears more often in French texts; however, it sometimes is used in referring to individual cells in ground tissues of types characterised as collenchyma.

Use in Zoology
In zoology the word "collocyte" applies to several different types of cell in very different taxa, and there are a few similar terms used confusingly or interchangeably, such as colloblast and collencyte. Some of the terms refer to specialised subject matter, so from time to time variations and inconsistent definitions have been coined independently in niche disciplines. For example glial cells sometimes are called "glue cells" but have little in common with any of the other types of cells that sometimes go by that name.

Apart from such difficulties, "glue cells" of various types commonly occur in taxa of animals that are practically unrelated to each other, and in such cases they are as a rule non-homologous and differ profoundly in their morphology, histology and function. This suggests that distinct terms should be allocated to the different types. The problem is so marked that many workers are abandoning traditional terms in favour of new words to avoid confusion.

Among the taxa of animals that have some form of collocyte, are the larvae of sessile forms of Tunicates. Most of those have collocytes near the head end, with which they permanently fasten themselves to the substrate.

Perhaps the most striking and celebrated examples of collocytes are in the Ctenophora (comb jellies). The Ctenophora use their colloblasts or collocytes in hunting and gathering food, in much the same way as members of the Cnidaria use cnidocytes; they keep the cells in a retracted form until they deploy their for securing prey. In keeping with their food capturing function, the cells sometimes are called "lasso cells", but as is common with such common names, the term is not precise and are variously applied to both colloblasts and cnidocytes. The retracted mechanism is kept coiled in the Ctenophora, as opposed to inside out in the Cnidaria. The Cnidaria evert their stings to penetrate the prey, but the Ctenophora eject microscopic balls of adhesive mucus that stick to the prey externally, trailing threads that do not lose attachment to the parent cell. The structures of the organs are extremely complex, and vary among the species of the Ctenophora. Their mechanisms are still under study.

In some organisms collocytes that attach the animal to substrates must be able to release their grip as well as establish it. Commonly, though not always, this requires the ability to dissolve the adhesive substances after the adhesion has been achieved. When a glandular structure has the ability to perform both the adhesion and the dissolving of the adhesive, it is called a duo-gland This is a very common requirement and examples occur in Platyhelminths, both parasitic and free-living, Annelida, Echinodermata and other phyla. In some organisms the adhesion it affords is so remarkably reversible that it is used as the basis of locomotion over solid surfaces.

Another class of so-called collocyte, or in this case "collencyte" occurs in sponges, but in this case there is little to do with adhesion. These are the component cells of the sponges' collenchyme tissue, loose mesenchyme between the ectoderm and the endoderm in the body wall.