Heterospio cf. reducta Laubier, Picard & Ramos, 1974

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 : 20-21

Heterospio cf. reducta Laubier, Picard & Ramos, 1974

Heterospio reducta Laubier, Picard & Ramos, 1974: 246 , figs. 1B–C, 3; Amoureux 1982: 185; Parapar et al. 2014, 990–995, figs. 9–10; Langeneck et al. 2017: 143–144.

Material examined. Off Ireland, R / V Chain, Cruise 106, J. F. Grassle, Chief Scientist, Sta. 310, 17 Aug 1972, Anchor dredge, 51.552°N, 12.357°W, 984– 978 m, 2 specimens ( MCZ 100580 ) .

Description. Both specimens incomplete, each, long, threadlike; largest with 11 setigerous segments, 16 mm long, 0.1 mm wide along most of body. Body with seven crowded thoracic segments followed by setiger 8 about as long as setigers 1–7; setiger 9 as long as setigers 1–8. Anterior setigers slightly flattened dorsoventrally, thicker than rest of body. From setiger 9 all segments cylindrical in cross section; from setiger 10 each segment elongate appearing stretched; with numerous transverse muscle bands. Color in alcohol light tan.

Prostomium broadly rounded anteriorly, flattened dorsoventrally; eyespots absent; nuchal organs grooves on posterolateral margin of prostomium. Peristomium with two rings, evident laterally, first ring narrow, second ring large, continuing across venter, interrupted dorsally by low crest. Dorsal tentacles and/or scars not present. Short, rounded pharynx everted on both specimens resulting in oral morphology not being apparent.

Branchiae present on setigers 2–4; these short, stubby. All parapodia biramous with setal fascicles well separated on all setigers. Encircling rows of setae or cinctures of setae not observed on any available segments. Noto- and neuropodia of setigers 1–8 each with about 12–15 capillaries arising from narrow setal fascicles; noto- and neuropodia of setigers 9–11 each with about 20–25 capillaries arising from two rows with broad dorsal and ventral gaps, not forming cinctures. Setae all capillaries; no neuropodial hooks in anterior setigers; acicular spines, aristate spines, and subuluncini not observed.

Posterior bulbous segments not present.

Methyl Green staining. No pattern, stain not retained anywhere along the body.

Remarks. These specimens from bathyal depths (984– 978 m) off SW Ireland agree with the morphology of Heterospio reducta as originally described by Laubier et al. (1974) from deep water (2335 m) off Algiers in the Mediterranean Sea and by Parapar et al. (2014) from bathyal depths (270–922 m) off Iceland. Amoureux (1982, 1987) also reported, but did not describe, specimens he identified as H. reducta from off W Ireland (500–1400 m). Langeneck et al. (2017) reported the species as a dominant polychaete from the Malta Escarpment in the Mediterranean, but did not describe their specimens. The species is characterized as having a broadly rounded, disklike prostomium, branchiae on setigers 2–4, with setiger 8 being the first elongated setiger, and all setae capillaries with no spines or segmental cinctures. However, no specimens having more than 12 setigers have ever been reported and therefore, complete absence of spines in abdominal segments cannot be fully confirmed until larger fragments or complete specimens are collected.

It has not escaped our notice that the type locality for Heterospio longissima Ehlers, 1874 , the type-species of the genus, is also off SW Ireland in bathyal depths (837 m) and only 116 km from the location of our specimens. Ehlers’ species was described for a specimen with 12 setigers with all capillary setae. Ehlers’ (1875) illustration also shows a broadly rounded prostomium, but branchiae are illustrated on setigers 2–8 instead of 2–4 and setiger 9 is the first elongate one instead of setiger 8 (see also Fig. 1 this study). Unfortunately, the original materials examined by Ehlers (1874, 1875) appear to have been lost ( Laubier et al. 1974; Borowski 1994). However, the possibility that the specimens from off Ireland identified here as H. cf. reducta , might actually represent the type species should be investigated given that we have determined that Hartman’s (1965) version of H. longissima was misconstrued and her collections actually include two of our newly described species ( H. hartmanae n. sp. and H. guiana n. sp.). We also note that Amoureux (1982) reported both H. longissima and H. reducta from off Ireland, but did not describe them. Amoureux (1987) later added H. mediterranea in a summary report of the “ Thalassia ” expeditions. A starting point might be to locate and examine his specimens. Some of his samples included two of these species.

Distribution. Mediterranean Sea, 1200–2100, 2335 m; Off SW Ireland, 500–1400 m; off Iceland, 270– 922 m.

Figures

FIGURE 1. Heterospio longissima Ehlers, 1874. A, anterior end, right lateral view; B, anterior end, dorsal view. Redrawn from Ehlers (1875).