It has been known to be very difficult to distinguish the different species of sea spiders but the N. gracile does have some characteristics that can help it be recognized a little easier.

[7] There are signs of sexual dimorphism occurring within the species as the males have been known to typically have larger palps and chelifores.

[7] The main organ for food uptake in the species is a triradially symmetric proboscis with a terminal mouth that has three movable lips.

[11] The organism appears to prefer free-floating as to reserve energy and only utilizes its ability to swim when necessary for survival.

[6] A researcher by the name of Elfed Morgan wanted to know more about these two mechanisms, so he did a study where he collected a handful of N. gracile from Mumbles Point on the Gower peninsula and observed their swimming behavior.

[6] During the leg-beat cycle the legs of the N. gracile beat vertically which causes them to swim with their dorsal side foremost.

Before the migration, they are about the age of a young adult, and when they leave for the sublittoral zone, their fertilization occurs.

Since N. gracile are weak swimmers and have to move large distances, they depend on tidal or off-shore currents for their transportation up and down the shore.

[12] A study done by Elfed Morgan on the cost of migration found that their fuels reserves are just enough for them to successfully take advantage of the better tides because swimming off shore is very energetically expensive for the species.

[10] Eggs develop from August to February and are carried on the ovigerous legs of the male Nymphon gracile.

The Vitellogenesis process of the eggs has the yolk synthesized intra-oöcytecally with a small oöcytic contribution.