Phylo ornatus

Phylo ornatus (Verrill, 1873)

Figures 43–44

Aricia ornata Verrill, 1873: 596; Verrill & Smith 1874: 60, 71, 302–303; Webster & Benedict 1884: 724; Andrews 1891: 292; Sumner et al. 1913: 623.

Orbinia ornata: Hartman 1942: 61; 1944: 340, pl. 18, fig. 7, pl. 19, fig. 6 (as Scoloplos armiger); 1945: 28.

Phylo ornatus Hartman 1951: 79; 1957: 265, pl. 24, figs. 1–10.

Orbinia (Orbinia) ornata: Pettibone 1963: 285–286, fig. 75a–b.

Material examined. Northeastern USA, Massachusetts, Cape Cod Bay, coll. N.J. Maciolek, Jul 1975, 41°46′N, 70°14′W, ca. 12 m (2, MCZ 161597).

Description. A large species, recorded with up to 300 setigers, 250 mm long and 5 mm wide (Pettibone 1963); present specimens both incomplete, largest with 131 setigers, 60 mm long, and 4–5 mm wide across middle thoracic setigers. Recorded with 19–32 thoracic setigers, present specimens with 28–29 thoracic setigers; branchiae from setiger 5 (Fig. 43B). Body elongate, with thoracic segments more-or-less rectangular in cross section, about ten times wider than long; flattened dorsally, weakly rounded on venter; abdominal segments strongly rounded on venter, flattened across dorsum with parapodia dorsally elevated. A narrow mid-ventral line extends along most of body.All known specimens with branchiae from setiger 5. Present specimens light tan with no other pigmentation.

Pre-setiger region and first four setigers slightly elevated, rounded dorsally (Fig. 43 A–B). Prostomium short, conical, tapering to rounded tip (Fig. 43 A–B); eyespots absent; nuchal organs a narrow groove at junction with peristomium. Peristomium a narrow single ring dorsally; ventrally forming anterior and posterior lips of mouth, extending on to setiger 1. Anterior oral lips with two large rounded lobes; posterior lips formed by 5–6 weakly developed elongate lobes. When everted, proboscis consisting of two inflated lobes.

Present specimens with 28 and 29 thoracic setigers; Pettibone (1963) recorded specimens with 19–32 thoracic setigers; Hartman (1957) recorded 30 thoracic setigers (14 anterior and 16 posterior thoracic setigers based on presence of larger modified spines in posterior thoracic neuropodia). In present material, larger modified spines first present from setiger 15 in both. Thoracic notopodia all similar, triangular in posterior view (Fig. 44 A–C) and digitate in lateral view (Fig. 43B, D). Abdominal notopodia elongate, digitiform lobes tapering to conical tip (Fig. 44D); some lobes with bifurcated tip. Thoracic neuropodia thick, elongate, bearing up to six rows of numerous uncini and groups of capillaries (Figs. 43 A–D, 44A–C). First setiger with six rounded postsetal lobes; setiger 4 with nine short conical postsetal lobes (Fig. 44A); setiger 10 with 13 similar postsetal lobes, continuing for several more segments (Fig. 44B), then number of postsetal lobes decreasing to 3–4 on last thoracic setigers. All postsetal lobes arranged in a row posterior to rows of uncini. Subpodial lobes first present from setiger 12 with two lobes ventral to neuropodium (Fig. 43A, C); number of subpodial lobes increasing from three to about eight over setigers 15–20 (Fig. 44 B–C), then increasing to about 35–40 on a side in two irregular rows through rest of thoracic region (Fig. 43D), continuing on to 5–6 abdominal setigers; these forming prominent ventral fringe encircling venter (Figs. 43D, 44C); individual subpodial lobes conical, tapering, with inflated tips (Fig. 44 B–C). Abdominal neuropodia elevated, relatively short, divided apically into two lobes with lateral lobe long in anterior neuropodia and short in middle and posterior segments (Fig. 44D); a narrow, sometimes bulbous ventral flange present below neuropodium, but extra ventral cirri and subpodial lobes absent (Fig. 44D). Interramal cirri absent.

Branchiae from setiger 5 located mid-dorsally in thoracic setigers and widely separated from notopodium (Fig. 44B), but close to notopodium in abdominal segments (Fig. 44D). Each branchia triangular in shape, heavily ciliated.

Thoracic notosetae all crenulated capillaries, initially numbering about 25–30 per fascicle, increasing to about 45 setae per fascicle, and then reduced to about 30 in last few thoracic setigers. Abdominal notosetae about 18 capillaries and 1–2 furcate setae. Furcate setae with unequal tynes with blunt tips (Fig. 44 H–I); each tyne with fine needles directed medially (Fig. 44I); shaft with transverse rows of barbs, but these difficult to see, likely worn. Thoracic neurosetae of setigers 1–14 including up to six rows of conspicuous spinous yellow uncini and a few capillaries; uncini with a curved shaft and blunt tip; shaft with transverse ribs (Fig. 44E). Each row of uncini alternating in position with spine of adjacent row. From setiger 15, uncini in first row larger, dark, with straight pointed shaft, rounded tip (Fig. 44 F–G); position of uncini from setiger 15 also shifted, with most uncini arranged in six rows, but with first row of heavier spines extending dorsally toward notopodium (Fig. 43 C–D). Abdominal neurosetae consisting of 5–8 long serrated capillaries; flail setae not observed. One or two minute imbedded aciculae also present, usually not emergent.

Pygidium with a pair of long, thin dorsolateral cirri (Pettibone 1963).

Remarks. Phylo ornatus, unlike most species of Phylo, has specialized simple pointed neuropodial spines that occur over 13 or more posterior thoracic segments; these are located on the first or anterior row of uncini. In contrast, P. paraornatus n. sp. has similar spines, but these are initially located in the upper part of the thoracic neuropodium and limited to the posterior row in the last 10 thoracic setigers. See further comments on these two species in the following account.

Distribution. Off Massachusetts to Florida; Gulf of Mexico. California records need to be confirmed. Intertidal to about 30 m.