Heterospio canariensis, Blake & Maciolek, 2023

Blake, James A. & Maciolek, Nancy J., 2023, New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas, Zootaxa 5260 (1), pp. 1-74 : 21-23

Heterospio canariensis new species

Figure 7

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Material examined. (9 specimens) Eastern North Atlantic Ocean , off Canary Islands, SE of Gran Canaria Island, coll. J. Allen, RRS Discovery, Cruise 21, Sta. 6711, 19 Mar 1968, EBS, 27.248°N, 15.605°W, 2988 m, holotype ( LACM-AHF Poly 13266); 4 paratypes plus middle and post. fragments ( LACM-AHF Poly 13267); Sta. 6709, 18 Mar 1968, EBS, 27.537°N, 15.427°W, 2351 m, 3 paratypes ( LACM-AHF Poly 13264); Sta. 6710, 19 Mar 1968, EBS, 27.395N, 15.66°W, 2670 m, 1 paratype plus posterior fragments ( LACM-AHF Poly 13265) .

Description. An elongate, threadlike species; all specimens incomplete, material includes anterior fragments with 12–13 setigers, abdominal fragments, and posterior fragments with bulbous posterior ends containing at least three setigers. Holotype (LACM-AHF Poly 13266) an anterior fragment with 13 setigers, 16.6 mm long, 0.36 mm wide across thorax and 0.38 mm wide across abdominal segments. Paratype (LACM-AHF Poly 13267) with 12 setigers, 12.4 mm long, 0.41 mm wide across thorax and 0.21 mm wide across abdominal segments. Dorsal surface of thoracic region with parapodia weakly elevated producing flattened channel along first seven setigers ( Fig. 7A ); following abdominal segments with relatively smooth surface interrupted by numerous transverse muscle bands. Ventral surface with mid-ventral ridge extending from peristomium to about setiger 6 ( Fig. 7B ), thereafter ventral surface relatively smooth, similar to that of dorsum. Color in alcohol light tan.

Pre-setiger region about as long as first three thoracic setigers ( Fig. 7A–B ). Prostomium rhomboid-shape in dorsal view, widest medially, anteriorly tapering to broadly rounded apex, narrowing posteriorly, continuing as dorsal crest or ridge over peristomium to middle of setiger 3 ( Fig. 7A ); eyespots absent; nuchal organs distinct slits on posterior lateral margins anterior to first peristomial ring; dorsal surface with numerous small lumps extending over dorsal surface, not as obvious on ventral surface ( Fig. 7A ); ventrally prostomium broadly rounded anteriorly, merging posteriorly with upper lip of mouth ( Fig. 7B ). Peristomium with two rings; anterior ring unusually narrow ( Fig. 7A ), ventrally forming anterior lip of mouth ( Fig. 7B ); posterior ring as large as subsequent parapodia, interrupted dorsally by dorsal crest ( Fig. 7A ) and ventrally by posterior lip of mouth and ventral ridge ( Fig. 7B ). Mouth opening a transverse slit with about six large lobes on anterior lip and smaller indistinct lobes on posterior lip that merge with mid-ventral ridge ( Fig. 7B ). Proboscis partially everted on some specimens as simple rounded lobe. Dorsal tentacles not present on any specimen, but scars evident mid-dorsally in notches between two peristomial rings. Branchiae limited to setiger 1 on all specimens examined ( Fig. 7A ); branchiae short, thick, apparently broken or regenerating.

All parapodia biramous with setal fascicles arising from near anterior edge of segment. Thoracic region of all specimens with eight short setigers, twice as wide as long ( Fig. 7A ); setiger 9 elongate, about as long as thoracic setigers 5–8 combined ( Fig. 7A ). All thoracic setigers slightly flattened dorsally with parapodia inflated and elevated over dorsum, bearing setae in tight fascicles. Abdominal setigers from setiger 10 rounded in cross section, bearing setae in transverse rows encircling each segment similar to cinctures of some cirratulid polychaetes ( Fig. 7A ). Abdominal parapodia from setiger 10 narrow elongate lobes, noto- and neuropodia with distinct dorsal and ventral gaps between setal fascicles; lateral gaps between noto- and neuropodia narrower.

All thoracic notopodia of setigers1–9 with 10–15 long capillaries in spreading fascicles; capillaries of neuropodia more numerous with up to 20–25 setae arranged in tight, dense fascicle. Noto- and neuropodia of setigers 10–13 with both capillaries and acicular spines in two transverse rows forming cinctures similar to those of some cirratulid polychaetes; cinctures partial on setiger 10, fully developed on setigers 11–13. Spines present in anterior or first row of setae and more numerous capillaries in posterior row. Acicular spines thickened, tapering to narrow pointed tip ( Fig. 7D ), aristate spines not observed; capillaries thin, narrowing to long fine tip ( Fig. 7E ). Far posterior bulbous section oval-shaped, with dorsal groove and terminal anal opening; with three parapodia, each bearing 1–2 hooked spines in each ramus. Each spine short, with curved with narrow blunted tip ( Fig. 7F ).

Methyl Green staining. Prostomium and both peristomial rings staining intensely with unstained grooves between, producing distinct pattern; laterally, first eight setigers staining intensely between parapodia, also producing pattern; areas where setae emerge not staining. Rest of body not retaining stain, no pattern.

Remarks. Heterospio canariensis n. sp. is characterized by having: (1) two peristomial rings where the first is narrow and ventrally forms the anterior lip of the mouth, (2) a dorsal crest that extends from the prostomium posteriorly to about setiger 2, (3) a ventral crest or ridge that extends from the posterior lip of the mouth to about setiger 6, (4) only a single pair of branchiae (setiger 2), (5) setiger 9 is the first long setiger and is about as long as the preceding setigers 5–8, (6) acicular spines are simple and first present from setiger 10, and (7) the posterior bulbous section has at least three parapodia each with 1–2 curved hooked spines. No other species of Heterospio has this combination of characters.

Etymology. The epithet is derived from the type locality off the Canary Islands.

Distribution. Eastern North Atlantic Ocean, off Canary Islands, 2351–2988 m.

Figures

FIGURE 7. Heterospio canariensis n. sp. A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, right lateral view; D, notopodial acicular spine setiger 11; E, notopodial capillary setiger 11; F, posterior notopodial hook.A, holotype (LACM-AHF Poly 13266); B–F, paratype (LACM-AHF Poly 13267).