Autolytus cornutus Agassiz, 1862: 384 –403, pl. 9, fig. 1–20, pl. 10, fig. 1–15, pl. 11, fig. 1–10; Quatrefages 1866: 44 –46; Verrill 1881: 292, 300, 304, 308, 323, pl. 12, fig. 4, 6; Mensch 1900 a; 1900 b; 1900 c; Potts 1911: 29 –30; Treadwell 1948: 30, fig. 16 A–C; Korringa 1951: 77 –79, fig. 7 A–D; Pettibone 1963: 144, fig. 37 E; Okada 1933 a: 645 –647, figs 3, 4.
Autolytus fallax Malmgren, 1867: 33 –34, pl. 6, fig. 41; Pettibone 1954: 247 –249, fig. 29 C–F.
Myriana cirrata Treadwell, 1931: 2 –3, fig. 2 A–C.
Autolytus prismaticus Thorson 1946: 39 –40.
Autolytus prolifer Dales 1952 (in part).
Proceraea cornuta Gidholm 1965: 35; 1967: 205–206, figs 13 E–F, 28 A; Hamond 1967: 1 –4, fig. 2 A–B; 1969 c; HartmannSchröder 1971: 184, fig. 59 A–D; Rasmussen 1973: 76, fig. 23; Hamond 1974; Gardiner 1976: 129; Kirkegaard 1992: 255 –257, fig. 126 A–D; Hartmann Schröder 1996: 188, fig. 81 A–D; Nygren & Sundberg 2003: GenBank sequences, 16 S rDNA partial sequence AF 474266, and 18 S rDNA partial sequence AF 474312.
Autolytus (Regulatus) cornutus Imajima 1966: 49 –51, fig. 13 A–I.
Material examined. Sweden: 20 spms, Tjärnö archipelago, Inre Vattenholmen, 58 ° 52 'N 11 °06'E, intertidal, algae with epifauna, Apr 2000. Faroes: 7 spms (2 spms in formalin, 2 spms on slides, 3 spms in author's collection for DNA analyses), outside Kaldbak marine laboratory, 62 °N 06°W, dive, 1–4 m, Laminaria spp. with epifauna, 21 Jun 1997.
Diagnosis. Proceraea with 2 indistinct longitudinal black lines along the sides.
Description. Length in live specimens 4–10 mm for 30–50 chaetigers; width c. 0.3 mm. Live specimens yellowish with 2 indistinct black lines along the sides of body, sometimes with 2 very faint lines on dorsum. Preserved specimens without colour markings. Ciliation present on prostomium, nuchal epaulettes, and a few segments ventrally.
Eyes separated (Fig. 9 A); eye spots present. Palps in dorsal view projecting 1 / 4 – 1 / 3 of prostomial length (Fig. 9 A), fused. Extension of nuchal epaulettes from half to end of tentacular segment (Fig. 9 A).
Median antenna reaching chaetiger 8–10 in live specimens (n= 5). Lateral antennae and dorsal tentacular cirri, length 1 / 2 – 2 / 3 of median antenna. Ventral tentacular cirri 1 / 3 – 1 / 2 as long as dorsal pair. First dorsal cirri as long as median antenna, second dorsal cirri as long as ventral tentacular cirri. Alternation in direction of cirri not assessed. Dorsal cirri from chaetiger 3, of equal length, 1 / 3 – 2 / 3 of body width. Cirrophores on tentacular segment and first dorsal cirri present; cirrophores otherwise absent. All appendages cylindrical.
Parapodial lobes rounded conical, small. Single acicula in all chaetigers. Chaetal fascicle with 7–12 compounds in anterior chaetigers, 3–8 in median and posterior. Compound chaetae with small distal tooth (Fig. 9 B); serration present. Single thick bayonet chaetae (Fig. 9 C), beginning between chaetiger 1–5.
Pharynx with 1 sinuation anterior and lateral to anterior half of proventricle (Fig. 9 A). Trepan in chaetiger 1–2 (Fig. 9 A), with 18 unequal teeth, 9 large and 9 smaller; 1 large alternating with 1 small, arranged in 2 rings. Basal ring present; infradental spines absent. Proventricle equal in length to 1–2 segments in chaetiger 5–9 with 30–35 rows of muscle cells (n= 7). Anal cirri equal in length to c. 1 / 2 body width.
Reproduction. Schizogamy by anterior scissiparity behind chaetiger 13. According to Gidholm (1967), reproduction confined to colder seasons, mainly in November and December but also through May. Stolonforming individuals caught all year around though.
Morphology of epitokous stages.
Male. Length in preserved specimens 4–4.2 mm for 6 +(21–23)+(2–7) chaetigers (n= 2), width in region a 0.3 mm, width in region b 0.5 mm. Ciliation absent except for nuchal epaulettes.
Prostomium with concave anterior margin. Nuchal epaulettes rounded, reaching over half of first segment.
Median antenna reaching chaetiger 11. Lateral bifid antennae, 3 times as long as prostomial width; basal part 1 / 3 of total length, outer ventral rami slightly shorter than inner dorsal rami. Frontal processes, equal to 1 / 3 of prostomial width. Tentacular cirri 2 pairs, dorsal pair as long as or 1.5 times prostomial width, ventral pair 1 / 6 in length of dorsal. First dorsal cirri, equal in length to median antenna; achaetous knobs present. Cirri in region a equal to 2 / 3 of body width, cirri in region b and c successively shorter, in region b equal to 1 / 4 of body width, in region c 1 / 4 – 1 / 5 of body width. Median antenna with ceratophore; small cirrophores on tentacular cirri, large cirrophores on first dorsal cirri, and small cirrophores on cirri in region a, present; cirrophores otherwise absent. Cirri on chaetiger 3–6 fusiform, frontal processes club shaped, other appendages cylindrical.
Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 3 thick and 4 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 4–10 compounds, single bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with 20–25 swimming chaetae. Anal cirri equal in length to cirri in region c.
Female. No females found. Pettibone (1954), Gidholm (1965, 1967), Hamond (1967, 1974) give brief descriptions on stolon morphology. Length 4–5 mm for 6 +(12–15)+(9– 11) chaetigers (Gidholm 1967), 5–15 mm according to Pettibone (1954). Tentacular cirri 2 pairs, achaetous knobs present (Pettibone, 1954). Short nuchal epaulettes covering anterior part of first segment. One short egg sac, eggs yellowish (Gidholm 1967) or orange (Pettibone 1954).
Habitat. Shallow waters, 0–20 m, amongst algae with bryozans, e.g. Membranipora membranacea and Electra pilosa, or hydroids, like Laomedea geniculata and Campanularia sp. It has been shown that P. cornuta feeds on a number of Laomedea species (Hamond 1969 c).
Distribution. North Atlantic and North Pacific.
Remarks. Proceraea cornuta is most similar to P. okadai, P. nigropunctata Nygren & Gidholm, 2001, and P. micropedata HartmannSchröder, 1962; P. okadai, and P. nigropunctata may be separated on their respective colour markings, synonomy with P. micropedata cannot be excluded as information on colour in this taxon is lacking.