Ampharete baltica Eliason, 1955

Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf & Bick, Andreas, 2022, From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae), Zootaxa 5174 (4), pp. 357-380 : 373

Ampharete baltica Eliason, 1955

( Fig. 10 )

Ampharete grubei baltica Eliason, 1955: 6–7 .

Material examined. Type material: Baltic Sea , Kalmar, 55°50‘N, 16°05‘E, 19.8 1954, GNM Polych. 11192 (holotype); 55°50‘N, 16°05‘E, 19.8 1954, GNM Polych. 11103 (4 paratypes) .

Diagnosis. Small species of up to 8 mm in length and 0.9 mm in width ( Fig. 10A ). Twelve thoracic, two intermediate, and ten abdominal uncinigers with minute neuropodial cirri ( Fig. 10E ). Prostomium triangular with three lobes, with eyespots. Branchiae arranged in two groups separated by a very small median gap of less than one branchial base width; three pairs in anterior transverse row (the middle one sometimes shifted anteriorly) and last pair in posterior position, directly below middle branchia of anterior row. Paleae long, slender with filiform tips, 6–10 each side ( Fig. 10B ). Pygidium with lateral cirri and a number of cirriform papillae ( Fig. 11C ).

Remarks. Type material of 7–8 mm in length, some specimens with eggs ( Fig. 10D ). The specimens found in the Baltic Sea had a maximum length of 11 mm (SBRO), but Holthe (1986) and Hartmann-Schröder (1996) reported a maximum length of 18 mm. Minute, rounded dorsal cirri have only been observed on abdominal neuropodia. Diagnostic characters on the pygidium are often difficult to verify on fixed material because the pygidium is often retracted into the abdomen. In addition, the pygidium seems to be very variable. There are one or two rings of cirri that vary in length. Methylene blue is very helpful in identifying the length of the cirri; the pair of lateral cirri being much more intensely coloured than the remaining cirri or papillae. The lateral cirri have the shape of lobes in smaller specimens (7 mm long) and are clearly distant from the ring of pygidial cirri. The papillae of the outer ring are as long as the lateral cirri or slightly shorter, the inner ring has a number of long cirri. As the pygidium of A. baltica is very variable, we have excluded this character from the identification key.

Distribution and ecology. Baltic Sea. This species was found on silt and sandy bottoms in 5–50 m depths, 7–29 psu. The species densities reached from 10–1,000 and more individuals/m 2.

Figures

FIGURE 10. Paratypes of Ampharete baltica Eliason, 1955 (GNM Polych. 11103). Micrographs of methyl blue staining patterns and unstained individuals.A. Complete specimen, dorsal view. B. Anterior end with branchiae and paleae, ventral view. C. Posterior end with anal papillae, dorsal view. D. Lateral view of segments XIII–XXI, eggs present in segments X–XXI. E. Last intermediate, and two abdominal segments (XIX–XXI), lateral view. Arrow is pointing towards minute dorsal papilla on pinnule of first abdominal unciniger. A, C: Methyl blue staining. B, D, E: Unstained. Scale bars: A, B = 500 µm. C, D = 250 μm, E = 150 µm.

FIGURE 11. Paralectotypes of Ampharete grubei Malmgren, 1865 (SMNH-Type 5101). Micrographs of methyl blue staining patterns and unstained individuals. A. Complete specimen, dorsal view. B. Anterior end with paleae, branchiae and buccal tentacles, ventral view. C. Last thoracic and both intermediate segments (XVII–XXX) of large specimen (50 mm long) without dorsal cirri on neuropodia, lateral view. D. Posterior end with lateral cirri and long anal papillae, ventral view. E. Last thoracic, intermediate and abdominal segments (XVIII–XXIX) of smaller specimen (37 mm long) with short dorsal cirri on neuropodia, lateral view. A–C: unstained. D, E: Methyl blue staining. Scale bars: A = 2 mm. B, D = 500 µm. C, E = 1 mm.