The alae is a protruding ridge that forms longitudinally on many nematodes. In the Caenorhabditis elegans nematode they are present in the L1, dauer (an alternative long living larvae stage where the nematode is dormant) and adult stages. The alae are most pronounced during the dauer larval stage and not present in the L2, and L3 C. elegans stages. The term ‘alae’ is the plural of ala (wing), describing either one of the pair of ridges that forms on a nematode or an individual crease found on an individual ridge. The term ‘ala’ is rarely used in describing the alae and scientific journals use the term ‘alae’ both singularly and in the plural. Structure The alae is formed by the hypodermal seam cells where a fibrous ribbon of a zona pellucida (ZP) domain protein is produced. In C. elegans many of these proteins are termed CUT-1. The CUT refers to cuticulins which are the various proteins that are not solubilised by both reducing agents and detergents made insoluble by the nature of their crosslinks. Described as a matrix that appears to be holding the two sides of the collagenous cuticle together for strengthening it should also be interpreted as a matrix separating the cuticle thereby exposing itself to the external environment. The alae is formed during an oxidative process where peroxidase acts on protein bound tyrosine residues. The alae is a crease, that by the cross linking process causes radial shrinking of the seam cell secreted proteins. Function The function of the alae is not yet clear. It is generally given a function related to cuticle strength, nematode movement or fat storage. But the predominant structure of the C. elegans alae contain the ZP domain proteins (CUT-1, CUT-3, CUT-5). The ZP domain had been termed ‘the sequence in search of a function’ and has been given the functional role of matrix assembly and also putatively, functions in pheromone and olfactory signal transduction. Despite the structural nature of the ZP domain, it is not the ideal protein for strength alone. Wherever ZP domains are found, they are found in definite or putative association with signal transduction accompanied by interaction with an external or hostile environment. Function based on genetic data of the H. Contortus dauer nematode In the parasitic nematode Haemonchus contortus a ZP domain protein of a dauer stage nematode has been genetically associated to a target molecule found in