Callogorgia europaea, Altuna & López-González, 2019

Altuna, Álvaro & López-González, Pablo J., 2019, Description of two new species of bathyal Primnoidae (Octocorallia: Alcyonacea) from the Porcupine Bank (northeastern Atlantic), Zootaxa 4576 (1), pp. 61-80 : 63-69

Callogorgia europaea sp. nov.

( Figs. 1 A–C, 2–6)

urn:lsid:zoobank.org:act:AD3BC3F9-2ABD-4320-B19A-7A44C0CBFE46

Material examined. Porcupine Bank, 12.09.2015, Stn. 23, 52.869°N– 14.790°W, 645 m depth, one fragment 200 mm in length (MNCN 2.04/2022, holotype), one fragment 85 mm long ( MNCN 2.04 /2023, paratype) , and two small additional fragments 55 mm and 33 mm long. Porcupine Bank, 18.09. 2010, Stn. 28, 53.5739°N– 12.5657°W, 573 m, one fragment 128 mm long ( MNCN 2.04 /2024, paratype) .

Diagnosis. Colony plumose with polyps arranged in whorls of 4–8, with 4–5 whorls in 1 cm twig length; polyps with 11–14 scales in abaxial rows, 5–6 in outer-lateral rows, 2–3 in inner lateral rows and usually one in adaxial rows. Crest-like radial sculpture on distal-most scales of abaxial and outer-lateral rows. Sculpture strongest on marginals and becoming weaker proximally.

Description of the holotype. A colony fragment 200 mm long, whitish to light cream in colour, plumose, slightly flexible, uniplanar. No holdfast. Ramification pinnate, showing a tendency toward dichotomy in some branchlets. Branchlets up to 123 mm in length, slightly curved upwards at their origin, given off alternately left and right at acute angles every 7–15 mm along stem, and every 17–25 mm along each side of stem, giving the stem a subtle zigzag course; most branchlets ramified, up to the third order. Main stem almost round in cross-section, 2.0 mm in diameter, golden in colour, iridescent, with a faint longitudinal striation.

Polyps abundant, arranged in whorls of 4–8 (usually 5 in the final branchlets), with 4–5 whorls/cm (usually 4) of axial length; polyps clavate, most facing upwards and a few also downwards in the main stem, strongly bent inward toward the axis, 1.8–2.3 mm tall (average 2.07 mm) and 0.7–9.0 mm wide distally (average 0.78 mm). Body scales arranged in 8 longitudinal rows with 11–14 scales (commonly 12) in the two abaxial rows, 5–6 (7 rarely observed) in the two outer-lateral rows, 2–3 in the two inner-lateral rows, and 1 (2 rarely observed) in the adaxial rows; opercular scales 8.

Operculum well developed, with large abaxial and outer-lateral opercular scales, up to 0.56 x 0.35 mm (H: W of 1.75–2.44, average 1.90), longer and wider than inner-laterals, up to 0.47 x 0.20 mm (H: W of 2.38–2.71, average 2.58) and adaxials. Abaxials, outer-laterals and inner-laterals, more or less triangular, wide and slightly rounded to somewhat acute proximally, having a neat apical process. Adaxial scales similar to laterals but smaller and less triangular, up to 0.47 x 0.14 mm (H: W of 3.06–4.34, average 3.52). Scales moderately incurved with convex outer surface, inner surface with complex in most inner proximal surface with several cristate ridges distally; outer surface with abundant digitate processes indistinctly aligned in deep longitudinal ridges more finely digitate to cristate distally, proximal end of the outer surface with complex tubercles.

Abaxial scales toward the tip of the polyp more or less square to fan-shaped, usually straight proximally, having a cristate longitudinal ornamentation in the outer surface; crests prominent, radiating from lower third of scale to the distal margin, more or less straight to wavy, mainly digitated to complex edged, more irregular in the marginals. Scales getting wider proximally, with ornamentation becoming notably weaker, becoming almost smooth to slightly granulated proximally, and having frequently serrated margins; 3–4 most proximal ones wide and curved, up to 0.30 x 0.55 mm (H x W), becoming wing-shaped and circling the base of polyp ( Fig. 2 , 4C ); inner surface of scales covered by complex tubercles that extend to the lower end of the outer surface.

Outer-lateral scales broader than high, up to 0.28 x 0.48 mm (H x W), with longitudinal crests in the whole surface of the 2–3 distal-most scales (except the base), progressively reduced in extension to the proximal scales, occurring mainly in the abaxial half row on the scales at the middle of the row, and being absent in the lower-most ones that have a more or less smooth to slightly granulated surface. Inner surface with densely packaged complex tubercles also covering the outer surface on the lower third of scales.

Inner-lateral scales broader than high, up to 0.23 x 0.45 mm (H x W), with slightly granulated outer surface having slightly pointed granules and distal margin serrated. Granules may develop roughly into striations towards the distal end of scale. Inner surface with complex tubercles.

Adaxial scales located beneath adaxial opercular scales and almost entirely overlapped by the inner-laterals, small, delicate, more or less quadrate to slightly higher than wide, up to 0.22 x 0.20 mm (H x W), with small digitated to pointed processes on the outer surface ( Fig. 3A, D ) and complex tubercles on inner surface.

Coenenchyme thin, easily separated from axis, with numerous densely packaged sclerites arranged in one layer. Sclerites are long (up to 0.9 mm in length and 0.3 mm in width), sometimes vermiform, with simple granular sculpture on the outer surface, and complex tubercles tightly covering the inner one ( Fig. 5 ). Margins may be partially serrated, and both ends are occasionally bifurcated.

Etymology. In reference to the European distribution of the species, and to highlight the current complementary North Atlantic distribution, but morphologically similar to Callogorgia americana Cairns & Bayer, 2002 occurring in American waters from Florida to Venezuela ( Cairns & Bayer 2002).

Remarks. The material collected is scarce and the variability of the new species cannot be elucidated fully. The paratypes are fragments. One of them is a distal portion (MNCN 2.04/2023, Fig. 1B ) in agreement with the holotype, but other material (MNCN 2.04/2024, Fig. 1C ) seems to be a broken and rolled more basal old part showing a quasi-dichotomous ramification. Two of its branches anastomose, not to be confused with detached branchlets that become entangled among others and cemented, as noticed with other species of the genus by Cairns & Bayer (2002). The polyps are scarce and smaller than in the holotype (1.5–1.8 mm long; 0.52–0.76 mm distal width). In the smaller branches they are grouped in whorls of 5–6, having 6 whorls/cm. On the main stem, polyps are arranged irregularly, appearing mainly isolated. As occurs with the holotype, some polyps of the main stem face downwards.

Callogorgia europaea sp. nov. pertains to a group of species with part of its abaxial scales having an external sculpturing of deep longitudinal crests (cristate) (see Bayer 1982; Cairns & Bayer 2002, 2009; Cairns 2016, 2018). They are mainly differentiated by means of features of the scales covering the polyps, such as number of abaxial scales, development of the outer scales, or the characteristics of the operculum and its scales (see Kükenthal 1924; Bayer 1982; Cairns & Bayer 2002). Most of these species inhabit Indo-Pacific localities. Cairns (2016: 68) included C. verticillata ( Pallas, 1766) within this group, but the sculpture of the scales in this species looks different (see Carpine & Grasshoff 1975, figs. 57, 58) and is formed mostly by granules as stated by Bayer (1982). This said, no species having scales with an external sculpturing of longitudinal crests were known from the Eastern Atlantic. However, doubtful records of C. flabellum ( Ehrenberg, 1834) ―a species having the abaxial scales sculptured with strong radial crests that extend distally (see Bayer 1982, fig. 2)― given by Stephens (1909: 9, as Caligorgia flabellum ) off Ireland, and by Thomson (1927: 34) from Cape Verde Islands are worth mentioning. The former author recorded the species from three stations at 51°37’N– 11°56’ W (ca. 1006 m), 51°36’N– 11°57’W (ca. 914 m), and 51°35’N– 11°44’W (ca. 1317 m) but gave neither figures nor description of the material, quoting only colony sizes (up to 117 cm in height). The latter author pictured the colony and the polyps and gave a brief description of the species, but lack sufficient detail to verify his identification. Thomson (1927) erroneously considered that the number and disposition of scales in the polyps were of little importance as a distinctive character. He mentioned up to 12 abaxial scales, but also described the adaxial ones as being very abundant (not a Callogorgia character) or completely absent. Besides, according to this author, the branching pattern of that material tends to be more dichotomous than pinnate. For Carpine & Grasshoff (1985) and Grasshoff (1985), Thomson’s record corresponds to C. verticillata . The material identified as Callogorgia flabellum by Stephens (1909) could belong to the new species here proposed.

Callogorgia europaea sp. nov. is close to C. americana and C. delta Cairns & Bayer, 2002 , two species that have a more southerly distribution in the western Atlantic, and to a lesser extent to C. weltneri Versluys, 1906 (= C. cristata Aurivillius, 1931 ), C. flabellum and C. gilberti ( Nutting, 1908) from the Pacific Ocean.

According to Kükenthal (1924) and Cairns (2018), the polyps of C. weltneri lack inner lateral scales, have 8– 10 scales in abaxial rows, and abaxial opercular scales have two to four apical points. Consequently, it is soon disregarded as a species comparable to C. europaea sp. nov. A description of C. flabellum was provided by Versluys (1906), and SEM pictures of the polyps and scales by Bayer (1982). According to Bayer (1982) and Cairns (2018) this species has 8–10 scales in each abaxial row, with 3 outer laterals, 2 inner laterals and 1 adaxial, hence differing from C. europaea sp. nov. The cristate sculpture of the abaxial rows of scales is also stronger than in C. europaea sp. nov., and extends in C. flabellum to the proximal-most scales of the rows (see Bayer 1982, fig. 2). The external side of the proximal-most scales of C. europaea sp. nov. is, however, rather smoother ( Fig. 4C ). According to Nutting (1908) and Cairns (2018), the Hawaiian C. gilberti is characterized by an elevated number of abaxials (11–13), a smaller polyp size (1.5 mm) than C. europaea sp. nov. (up to 2.3 mm, average 2.07 mm), and adaxial operculars not being notably smaller than the abaxial ones (ratios abaxial: adaxial operculars of C. europaea sp. nov.: 1.3 in height and 1.6 in width).

The new species differs from C. americana and C. delta by its bigger polyps, up to 2.3 mm in height (average 2.07 mm) and 0.9 mm in distal width, and by a higher number of abaxial, outer-lateral and inner-lateral scales. The opercular scales are of a similar size but of a different shape. In C. americana and C. delta the base is flat (see Cairns & Bayer 2002; Bayer et al. 2015), being curved or slightly acute in C. europaea sp. nov.; therefore, their maximal width is slightly above the proximal end. Moreover, the ornamentation of the opercular scales is distinctly different: radial crests (with finely serrated edges) more or less fractioned in the western Atlantic species, but of longitudinal ridges with digitated projections, or simply longitudinal lines of tall digitate projections in the eastern Atlantic one. This more ornamented structure due to the presence of digitate projections is also visible in the distalmost rows of abaxials and outer laterals (see Cairns & Bayer 2002: fig. 3 for C. americana , fig. 6 for C. delta ; and Figs. 4 , 6 in the present paper for C. europaea sp. nov.). Additionally, the centre of radiation of the ridges in western Atlantic species is often inside the sclerite, whereas in the eastern Atlantic species it is often outside of the sclerite ( Fig. 6 B–E). This fact provides a radial aspect in the orientation of the ridges in C. americana and C. delta , but a more parallel aspect in C. europaea sp. nov. Additional differences are the prevalent number of polyps per whorl and the number of whorls of polyps/cm (see Table 1, and Cairns & Bayer 2002). Our new species is also notably different from the newly described C. lucaya Cordeiro, Bayer & Cairns, 2018 from the western Atlantic. This species lacks outer-lateral body wall scales, has a small number of abaxials, and the body wall sclerites are externally almost smooth ( Cordeiro et al. 2018b).

Strong genetic divergence among species closely related morphologically has been demonstrated in western Atlantic species of Callogorgia (see Quattrini et al. 2013). Consequently, formerly proposed subspecies of C. americana ( C. americana americana and C. americana delta ), were raised to species rank after a molecular study by these authors (see also Bayer et al. 2015). The status of C. europaea sp. nov. is supported morphologically on the same grounds. A genetic evaluation of the new species will be desirable in the near future, but we failed in extracting DNA of high enough quality for sequencing from the present Porcupine material.

The new species differs from C. verticillata , the abundant and widely extended species in the northeastern Atlantic and the Mediterranean Sea, in the size of the polyps and the number and morphology of the scales covering them. The habitus of their colonies is certainly similar, with both species being of the same colour and having an alternate pinnate branching (see Carpine & Grasshoff 1975, Figs. 56–58, C. verticillata ). The longitudinal crests of the outer surface of the distalmost marginal scales of the polyps of the new species, which are absent in C. verticillata , and the different number and arrangement of body scales, promptly identify the species when closely examined. Callogorgia grimaldii from the Azores Archipelago is an obscure species rarely mentioned in the literature and different from the new species here proposed. Although accepted in WORMS ( Cordeiro et al. 2018c), it was considered a synonym of C. verticillata by Carpine & Grasshoff (1985) or a variety of this species ( Cairns & Bayer 2009).

The genera Fanellia Gray, 1870 and Callogorgia were largely considered related due to their morphology, the former genus having been restored by Bayer (1982), and both genera were considered sibling groups ( Cairns & Bayer 2009: 40) in the first cladistic analyses. However, recent molecular approaches suggested a polyphyletic nature, with species of both genera presented nested in the same clade ( Taylor & Rogers 2015: fig.1 clade 4), and finally Fanellia was considered a synonym of Callogorgia ( Cairns & Wirshing 2018) . Nevertheless, the nature of the sculpture of the outer sclerite surface, which is tuberculate to nodular for Fanellia instead of granular to smooth for Callogorgia , can be considered a practical feature in distinguishing groups of species within Callogorgia . As above described, the new proposed species in this paper agrees well with the characters originally attributed to the genus Callogorgia .

Distribution. At present, the species is only known from the Porcupine Bank, northeastern Atlantic, 573–645

m depth.

Figures

FIGURE 1. Callogorgia europaea sp. nov. (A) Holotype (MNCN 2.04/2022). (B) Paratype (MNCN 2.04/2023). (C) Paratype (MNCN 2.04/2024). Thouarella porcupinensis sp. nov. (D) Holotype (MNCN 2.04/2025). (E) Proximal part of axis showing sinuous morphology. (F) Epizoic sea anemone.

FIGURE 2. Callogorgia europaea sp. nov., holotype MNCN (2.04/2022). SEM microphotographs. (A) Two contiguous whorls of polyps. (B) Whorl of polyps. (C) Polyp, lateral view, showing ordination and number of the different scales according to their position. (D) Polyp, lateral view. Abbreviations: AB, abaxial; OL, outer lateral; IL, inner lateral; OP, opercular.

FIGURE 3. Callogorgia europaea sp. nov., holotype MNCN (2.04/2022). SEM microphotographs. (A–C) Polyps, distalmost part in oral views, stereopairs. (D) Polyp, distalmost part showing operculars, marginals, and submarginals, inner laterals and adaxial scales. (E) Polyp, adaxial view. (F) Axis surface.

FIGURE 4. Callogorgia europaea sp. nov., holotype MNCN (2.04/2022).SEM microphotographs. (A) Opercular scales: 1, abaxials; 2, outer laterals; 3, inner laterals; 4, adaxials. (B) Body wall scales of distal part of polyp. (C) Abaxial basal scales. All scales but those marked with * are in outer face view.

FIGURE 5. Callogorgia europaea sp. nov., holotype MNCN (2.04/2022). SEM microphotographs. Coenenchymal sclerites. All sclerites but those marked with * are in outer face view.

FIGURE 6. Callogorgia europaea sp. nov. holotype MNCN (2.04/2022). SEM microphotographs of characteristics scales: (A) Opercular scale. (B) Abaxial marginal scale. (C) Abaxial scale of distal part of polyp. Callogorgia americana: (D) Adaxial scale of distal part of polyp (modified from Cairns & Bayer, 2002: fig. 3J). Callogorgia delta: (E) Adaxial scale of distal part of polyp (modified from Cairns & Bayer, 2002: fig. 6H). Notice parallel ridges of digitated processes in A, and parallel to radial orientation of ridges in the abaxial body scales of the new proposed species (B and C) and the two closest species C. americana and C. delta, centres of radiation are indicated by the intersection of convergent arrows.