Alkmaria romijni is a small species, only up to 5 mm long, which live in shallow brackish water. It has only been found once in Norway.

Type locality

Alkmaarder Meer, Netherlands

Key characters

Measurements: Up to 5 mm long

Number of thoracic chaetigers: 16

Number of thoracic uncinigers: 13

Number of abdominal uncinigers: 13–19

Prostomium: With two longitudinal ridges and one pair of eyespots

Mouth tentacles: Smooth

Branchiae: Three pairs of branchiae in two groups located close together at mid-dorsum; branchiae in each group arranged in triangles and connected at bases

Paleae: Absent

Special features: None

Pygidium: Without cirri or papillae

Tube: Very thin, transparent layer of organic secretion incrusted with small sand grains and silt.

Remarks

The species has only been reported once in Norway, in Fredrikstad in 1974. Inhabits shallow brackish waters, a habitat rarely sampled for small worms, so it might be overlooked.

Similar species

Alkmaria romijni is a small-sized species. The small size makes it difficult to see characters and the species can be confused with other small-sized species and juvenile specimens of larger ampharetids. 

Sources

Holthe T (1986a). Polychaeta Terebellomorpha. Marine Invertebrates of Scandinavia 7: 1-192.

Horst R (1919). Twee sedentaire Polychaeten uit he brakke water var Nederland. Zoologische Mededeelingen, Leiden 5: 100-102. http://www.repository.naturalis.nl/record/318667

Jirkov IA (2001). [Polychaeta of the Arctic Ocean] (In Russian). Polikhety severnogo Ledovitogo Okeana. Yanus-K Press. Moscow, 632 pp.

Personal observations, Alvestad T.