Heteropathes opreski

Description of the holotype. The holotype (Fig. 1 a) is approximately 5 cm high (including pinnules) and about 1 cm wide (some of the lateral pinnules seem to be broken). The stem presents a diameter of about 0.3 mm near the base thickening up to 0.6 mm in diameter in the pinnulated portion. The unpinnulated portion of the stem is approximately 3 cm and the pinnulated portion 2 cm long (Fig. 1 a, b, c). There are two types of pinnules: 1) simple or presenting a small ramified subpinnule, elongate and slightly bent inward lateral pinnules and 2) short, straight, subpinnulated anterior pinnules. The 22 lateral pinnules are arranged alternately in such a way that adjacent pinnules on the same side of the stem are less than 2 mm apart and ca. 1 mm apart from those on the opposite side, which results in about 5 pinnules per cm on a given row and about 9 pinnules per cm of stem. The lowermost lateral pinnule is on the left side of the stem, subopposite from the next more distal pinnule on the right side, distanced about 0.7 mm, while the next pinnule on the left side is distanced about 1.4 mm. The lateral pinnules do not seem to be broken off at their tip, presenting very small spines on a blunt apex, measuring up to 7 mm in length and 0.2 to 0.5 (most 0.3) mm in diameter near their base. The lower lateral pinnules point toward the base and form an angle of approximately 70 º with the stem. Higher up they extend out at nearly right angles, becoming more inclined towards the apex of the colony, with the last lateral pinnule forming a 35 º angle to the stem. The interior angle formed by the two planes containing the lateral pinnules is close to 150 º for the lowermost pairs and 110 º for the higher ones (Fig. 1 d). A few lateral pinnules have a small and extensively ramified subpinnule similar to the anterior pinnules in all but size that is only visible when the colony is cut transversally as it tends to blend into the intertwined structure formed by the anterior pinnules. The secondary lateral pinnules are inserted in an acute angle on the anterior side of the lateral pinnules, arising about 1 mm after its base and measuring up to 2.5 mm in length and 0.25 mm in diameter near their base. They are heavily subpinnulated up to the 3 rd order (Fig. 1 e). The anterior primary pinnules are up to 6 mm in length, up to 0.4 mm in diameter near their base, and they are inserted 0.4 – 0.6 mm apart in a single irregular row, with 11 to 13 occurring along 1 cm of stem, from which they extend at almost right angles. The lowermost anterior pinnule is located between the second and third lowermost lateral pinnules. The anterior pinnules are heavily subpinnulated. The number and arrangement of the subpinnules is not strictly regular from pinnule to pinnule, but the primary pinnules seem to always present over 10, slightly shorter, secondary pinnules. They are inserted in an acute angle and curved distally, with the lowermost bilateral pair arising 0.5 – 0.8 mm above the base of the primary pinnule and parallel to the lateral pinnules. The subsequent pair presents a 90 º rotation and is inserted slightly above the first. The subsequent pinnules tend to follow this pattern forming a thick arborescent structure with up to 4 orders of pinnulation (Fig. 1 d, e). Simple and unornamented spines are present from the youngest parts of the corallum (Fig. 2 a) to the oldest, with the colony’s base and first 1.75 cm of stem presenting small conical spines measuring 0.005 – 0.04 mm in height and irregularly spaced in longitudinal rows (Fig. 2 b). Higher up the spines are replaced by 4 longitudinal ridges (from lateral view), reappearing on the pinnulated portion of the stem where they measure 0.04 – 0.09 mm in height and are inserted ca. 0.1 – 0.2 mm apart (Fig. 2 c, d). The spines on the primary lateral pinnules are triangular and often compressed and distally inclined. They measure 0.03 – 0.12 mm (most 0.05 – 0.09 mm) in height and are spaced 0.08 – 0.37 mm, with mostly 4 – 9 spines per mm within each of the longitudinal rows (Fig. 2 e). The spines on the secondary and tertiary lateral pinnules are conical, acute, distally inclined and bigger than those on the primary pinnules. They are inserted in longitudinal rows 0.07 – 0.3 mm apart and measure 0.04 – 0.18 mm in height (2 f). The spines on the anterior pinnules and subpinnules are larger than those on the lateral pinnules but also conical, acute and often distally inclined. The spines on the unpinnulated portion of the primary pinnules measure 0.05 – 0.07 mm in height and are spaced ca. 0.1 – 0.2 mm. The spines on the ramified portions measure 0.04 – 0.19 mm (most 0.05 – 0.15 mm) in height and are spaced ca. 0.1 – 0.4 mm, becoming larger towards the distal part of the ramifications, which often end in a blunt apex crowned by spines (Fig. 2 g, h). The spines are all similar in size on the unramified portion of the primary pinnules, but closer to the distal part of the anterior pinnules they are sometimes up to 0.05 mm higher on one side than on the opposite side, which suggests that these may be polypar spines. Additionally, they are not all placed in the same direction on all the pinnules. Assuming that these are indeed polypar spines, this suggests that the polyps are inserted randomly on the higher order pinnules. Since the specimen did not present any soft tissues, no further information regarding the polyps is available. Comparisons. Heteropathes opreski spec. nov. differs from the three other species assigned to this genus (H. americana, H. heterorhodzos and H. pacifica) in forming smaller colonies with shorter lateral pinnules (0.7 vs respectively 9, 6 and 14 cm) that sometimes present a small and extensively ramified subpinnule and presenting bigger spines on the primary lateral pinnules (up to 0.12 vs respectively 0.05, 0.05 and 0.06 mm in height) (for more details see dichotomous key below).

Fig. 1 (a – e), Fig. 2 (a – h)

Diagnosis. Corallum monopodial and pinnulate; pinnules arranged in two lateral rows and one irregular anterior row. Lateral pinnules simple or with a small and extensively ramified subpinnule. Primary lateral pinnules, elongated, arranged alternately, inclined and curved distally and up to 7 mm in length. Secondary lateral pinnules, short, inclined distally, up to 2.5 mm in length and ramified up to the 3 rd order. Anterior pinnules short, up to 6 mm in height, subpinnulate. Primary anterior pinnules inserted nearly perpendicularly to the plane containing the stem and lateral pinnules, presenting more than 10 secondary pinnules and forming an arborescent structure with up to 4 orders of ramification. Higher order pinnules slightly shorter than primary, inserted in an acute angle and presenting several pinnules on the upper and lower sides. Spines on primary lateral pinnules simple, up to 0.12 mm in height, triangular and often compressed and distally inclined. Spines on secondary and tertiary lateral pinnules are bigger than those on primary (up to 0.18 mm in height), simple, conical, acute and distally inclined. Spines on anterior pinnules simple, conical, acute, often distally inclined and bigger than those on lateral pinnules (up to 0.19 mm in height) becoming higher, more spaced and less regularly inserted towards the terminal pinnules that often present a distinctive, blunt and crowned by spines, apex.

Material. Holotype (EMEPC D 09 – Ma 007), NE Atlantic, Oceanographer Fracture Zone, EMEPC / AÇORES / G 3 / 2007 sta. 514, (34 º 46.722 ’ – 34 º 47.142 ’ N, 32 º 32.94 ’ – 32 º 32.868 ’ W), 2602 – 2270 m, rocky bottom, dredge, coll. V. de Matos, 23 May 2007.