The size of the body is 8–12 mm. The shape of the body is elongate, but broad. The color of the slug is from grey to black. The eyes are the only externally clearly visible feature on its head.
Aiteng ater has an unusual combination of morphological characters: • Reduction of mantle cavity • Prepharyngeal (circumpharyngeal) nerve ring • The presence of
ascus However, re-examination of the supposed "ascus" in
Aiteng ater is necessary, because an examination of an undescribed species Aitengidae sp. from Japan showed no true (i.e. sacoglossan-like) ascus containing old teeth, just a radula slightly bent at the end. • Uniseriate radula (radula with a descending and ascending limb) • The radula has a strong rhachidian tooth • The large, internal lateral eyes closely associated with the cerebral ganglia • The presence of a foot groove • A branched
digestive gland. This species lacks several acochlidian characteristics: • It has no
shell • No
tentacles • No
gills • No
cerata • It lacks the division of the body into head-foot complex and visceral hump • It lacks presence of 1–2 head appendages (with characteristic innervation of the rhinophores) • Tt lacks the ability to retract the head-foot complex into the visceral hump.
Aiteng ater has a
notum with a free margin. However, in the absence of a separated visceral hump,
Aiteng ater is able to retract its head under the frontal part of the notum. == Ecology ==