(Linnaeus, 1767)
Body
Small larvae up to 5 mm long and very thin. Posterior parapods very long with about 10 apical claws. Two pairs of anal tubules, about half the length of the posterior parapods. The upper pair longer than the lower pair Kloosia anal segments.
Head
The headcapsule is much longer than wide.
Antenna
The antenna is almost as long as the head, 6 segmented. The basal segment and the blade are shorter than the flagellum. Lauterborn organs are absent Kloosia antenna.
Mentum
The mentum has very pale teeth that are difficult to see. The median tooth is the largest, the first lateral and outer teeth are the smallest of the 6 lateral pairs. The ventromental plates are almost circular with striae divided in a long proximal part and a short distal part. Laterally the plates are covered with a sickle shaped thickening Kloosia mentum.
Labrum
SI is simpel and labral lamellae are absent. The pecten epipharyngis consists of thee lamellae with a plumose apex. The premandible has three teeth, the middle one longer than the others.
Mandible
The mandible pale with a long apical tooth and 3 subsequently smaller inner teeth Kloosia mandible.
Differential characteristics
The long and very thin body combined with a 6 segmented antenna is distinctive Kloosia antenna. The mentum is also highly characteristic Kloosia mentum.