I am no artist, but I do remember a technique I learned in a middle school drawing class called cross hatching. This eel, YPM ICH 13045, is a cutthroat eel of species Synaphobranchus kaupii, and was collected on July 29 2002 by Jon Moore at a depth of 1388 meters at Bear Seamount, an underwater volcanic mountain in the Atlantic Ocean off the coast of New England. Its scales remind me of cross hatching:
Cross hatching is used in drawings to create dimension, depth, and texture. Here are two examples of it that I found using Google image search at this site and this site, respectively:
In a previous post I talked about convergent evolution, which is the phenomenon where similar biological traits and forms evolve in unrelated lineages. A great example of convergent evolution is the wings of birds and bats-- although they both have wings, their wings evolved independently. It is not a trait that they both have through common ancestry.
Cutthroat eels tend to dwell on the slopes of continental shelves, where it might be useful to have scales that create texture to blend in with habitat there (I couldn't find any studies discussing the function of the scales, but this is my hypothesis. If you're wondering if light penetrates at these depths, see the discussion in the comments below). As I mentioned above, artists use cross hatching to create texture in their drawings. These eels have perhaps evolved criss-crossed scales to create texture; humans have developed cross-hatching to create texture. I am going to dub this convergent texture creation! (Presumptuously assuming, of course, that my hypothesis is correct...).
Here are more pictures of the scales, along with a full body shot for scale (although these eels can get much bigger than this).
My husband actually thinks the scales look more like the texture of a common type of steel flooring (pictured below), rather than cross hatching. What do you think?