(Kieffer, 1912)
Body
Large larvae with a length up to 12 mm. Living larvae are greenish. The fringe of swimming hairs is present (Moller Pillot, 1984a).
Head
The head is relatively small compared to the body, has a length of 0.55 - 0.65 mm with a cephalic index of 90 - 100% Tan head (Moller Pillot, 1984a).
Antenna
The antennal segments are all yellow and the antennal ratio is 5 - 6. The ring organ is situated at 0.8 - 0.9 of the height of the first segment. The second segment is normal and lacks a tuning fork (Wiederholm, 1983; Moller Pillot, 1984a).
Mentum
Dorsomentum with 5 - 6 teeth (rarely up to 8 teeth) on each side. Both parts are broadly joined in the middle Tan kraatzi dorsomentum (Moller Pillot, 1984a).
Ligula and paraligula
Ligula with 5 equal-sized yellow teeth in a straight line or slightly convex. Paraligula with 2 - 3 long teeth Tan kraatzi paraligula9.
Mandible
The mandible is very characteristic. The distal part of the inner margin with 2 long flat teeth and 2 small pointed accessory teeth next to each other. The basal tooth is a hump which is folded inwards distally Tan kraatzi mandible.
Maxilla
The maxilla is short with an undivided basal segment.
Anal tubules
6 anal tubules which are longer than wide Tan 6 anal tubules.
Posterior parapods
Some of the smaller claws with distal spines at the apex Tan kraatzi claws.
Differential characteristics
The yellow ligula with 5 equal teeth Tan punctipennis ligula, the cephalic index (90 - 100%) and the shape of the mandible Tan kraatzi mandible are distinctive for the genus Tanypus. T. kraatzi differs from T vilipennis by having 6 anal tubules (T. vilipennis only 4). T. kraatzi differs from T. punctipennis by the simpel paraglossa with 2 - 3 spines Tan kraatzi paraligula9 (T. punctipennis fan-shaped Tan punctipennis ligula), dorsomentum with 5-6 teeth Tan kraatzi dorsomentum (7-9 teeth in T. punctipennis Tan punctipennis mentum ) and distal spines on smaller anal claws Tan kraatzi claws instead of proximal spines in T. punctipennis Tan punctip claw.