The pinhead pearlfish is a slender, tapering, eel-like fish that can grow to a length of 30 cm (12 in).

[1] E. boraborensis is normally found living within the body cavity of a sea cucumber which it enters through the anus.

[3] When E. boraborensis enters a host and finds a carapid fish already present, it makes a noise.

If the fish already present is the closely related silver pearlfish, the sound is often reduced to a single longer pulse.

When E. homei enters a sea cucumber already occupied by E. boraborensis, the sound it emits is also often reduced to a single pulse, but in this case it is shorter than its normal call.