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.
Alkmaarder Meer, Netherlands
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
Special features: None
Pygidium: Without cirri or papillae
Tube: Very thin, transparent layer of organic secretion incrusted with small sand grains and silt.
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.
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.
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.