Anthothela quattriniae, Moore & Alderslade & Miller, 2017

Moore, Kirrily M., Alderslade, Philip & Miller, Karen J., 2017, A taxonomic revision of Anthothela (Octocorallia: Scleraxonia: Anthothelidae) and related genera, with the addition of new taxa, using morphological and molecular data, Zootaxa 4304 (1), pp. 1-212 : 81-91

Anthothela quattriniae sp. nov. Moore, Alderslade & Miller

http://zoobank.org/CB327C2D-3D3D-41DA-8F40-85E6E6C44350 ( Figs. 56–67 )

Material examined. Holotype: USNM 1207951 , Gulf of Mexico, USA, Lophelia II, (LII–10–464), ROV Jason , J2-531 GB535, NOAA Ship Ronald H. Brown, 27.426°N, 93.589°W, depth 522 m, 20–21st October 2010.

Description:

Colony form: The holotype is a tangled colony with narrow branches and no main stem, and is approximately 80 mm high and 90 mm wide ( Fig. 56 A). Six fragments of the colony were available for examination ( Fig. 56 B), all with polyps and calyces arranged along narrow branches. The pieces range in size from 6–20 mm long and 4– 14.5 mm across at the widest parts and the largest piece has six bifurcations with no distinguishable order or arrangement. There is some evidence of previous anastomoses. Branches are circular to elliptical in cross-section and range from 0.6–2.2 mm wide; there is some distortion of the branches at the bifurcation points and where the calyces occur. There is no holdfast or evidence of any membranous growth forms in the fragments examined but in the photograph of the whole colony it appears to be attached to a solitary coral and possibly has more than one attachment point ( Fig. 56 A).

Calyces and polyps occur along and around all of the branches. The largest space between two calyces is approximately 2 mm but most are closer than that, and they are crowded together at the branch tip, making it clavate ( Fig. 57 A, B).

The fragments are in good condition with many intact polyps and the cortex is complete.

Colour: Soon after collection the colony was recorded as white. The fragments of the holotype examined are white in alcohol.

Polyps and calyces: Calyces are mostly low cylinders, projecting usually at right angles from the branches and bearing large projecting sclerites ( Fig. 58 A). There are many smaller, probably juvenile polyps and calyces mixed amongst the larger ones ( Fig. 57 A, B)—the larger calyces are approximately 1–2 mm high while the juveniles are approximately 0.6–1.0 mm high. Calyces tend to be as wide or slightly wider than they are tall with larger calyx widths ranging from 1.5–2.5 mm (juvenile calyces between 1–1.5 mm wide). They have a very rough, prickly appearance due to the projecting sclerites and, although there are not true longitudinal ridges on the calyces, there is a slight tendency for the largest projecting sclerites to be arranged in longitudinal columns with the sclerites between the columns tending to be smaller.

Most polyps are partly retracted so the base of the polyp head sits on the lip of the calyx and the polyp neck is not visible ( Figs. 57 B; 58A). These polyps protrude approximately 1–1.5 mm from the lip of the calyx with the juvenile polyps protruding only 0.5–0.8 mm. Occasionally there are polyps fully retracted within the calyces with just a small round aperture obvious at the apex of a cone-shaped calyx ( Fig. 58 B). These calyces are approximately 1–1.2 mm high. Only one polyp in the holotype fragments examined is slightly extended, and this is only on one side of the polyp, otherwise there are no extended polyps. Polyp heads are approximately 1–2 mm wide and are crowded with large sclerites arranged into a collaret and points ( Fig. 58 A, C). Large sclerites project spectacularly from the points above the flat top of the polyp, which is formed where the tentacles fold over the mouth. Thus the polyp heads have imposing spiky peaks with the distinction between the points and the tentacle rachis being quite pronounced. There is a single row of 12 pinnules along each side of the tentacles.

Medulla and Cortex: The colony branches have a central medulla surrounded by a thin cortex. Both the medulla and cortex are comprised of tightly packed sclerites arranged longitudinally or obliquely. A ring of coelenteric canals, running longitudinally along the branches, surrounds the medulla, clearly separating it from the cortex ( Fig. 58 D). The canals are adjacent to each other but do not seem to anastomose or join thus they are always discernible as separate canals. They do not form a true boundary space. There are no obvious canals in the medulla.

The gastric cavity of the polyps arranged along the branches terminates in a flat base at the medulla while the polyps at the branch ends are slightly more elongated with the gastric cavities extending internally down the branches a small distance.

Sclerites: A robust covering of sclerites encases the colony pieces. Polyp heads have an impressive circlet of protruding spikes formed by large, more or less longitudinally arranged sclerites in the points, which grade from en chevron to transverse at the base of the polyp head to form a stout collaret, approximately 5–6 large sclerites in depth. The most common sclerite types in the collaret and the base of the points are straight or slightly curved, sometimes clavate, sticks and spindles with simple tubercles ( Fig. 59 ). These sclerites mostly grade from 0.5–0.7 mm long. At the top of the points there are large, bulky, slightly spiny thorn clubs projecting above and away from the polyp head. These sclerites ( Fig. 60 ) have a short, warty handle and a long, large head. The lower part of the head is bulbous and commonly narrows to a long end with small spiny projections. The handles are reasonably crowded with complex warts while around the bulbous middle of the sclerites there are usually low and fairly simple tubercles. Most of these bulky thorn clubs range in length from 0.45–0.8 mm although there are smaller ones only reaching approximately 0.3 mm long. On the single polyp which has some neck exposed, the neck region is covered in similar sclerites to the collaret, all transversely arranged. These are still quite large and crowded, surprisingly so considering the polyps can invaginate into the calyces.

At the top of the polyp head where the tentacles fold over, there is an abrupt change in the form of the sclerites. The bulky thorn clubs from the points give away to slightly curved rods, with simple tubercles, arranged almost en chevron along the aboral side of the tentacle rachis ( Fig. 61 A). These sclerites tend to curve over the sides of the tentacle and they grade down to small rods arranged haphazardly at the very tip ( Fig. 61 B). The sclerites grade continuously from 0.1–0.4 mm long.

The pinnules are tightly packed with longitudinally arranged, narrow sclerites ( Fig. 62 ). The most distinctive type is the spatulate club. They are long and narrow with a flattened spatulate tip positioned distad in the pinnules ( Fig. 61 A) and range from 0.1–0.3 mm in length. There are also small, straight, narrow sclerites with sparse, small tubercles and some flattened rods also with sparse tubercles; both these groups range from 0.07–0.25 mm long.

The calyces have three distinctive types of sclerite. Firstly, large, bulbous, slightly spiny thorn clubs, some with a rounded head, some with spear tips ( Fig. 63 ), project out from the calyx giving it a very prickly, complex surface ( Fig. 58 A). Many of these clubs are bent, with the projecting head arranged distally in the calyx. These sclerites have quite complex, crowded warts, particularly on the handle, while the head has sparse tubercles and small spines. Most of these are 0.4–0.6 mm long, although there are some smaller, less developed ones. The second type of calyx sclerites is much smaller sticks and rods, a few clavate, with simple to complex tubercles and these are only 0.1–0.5 mm long ( Fig. 64 ). All sclerites are mixed together on the calyx except for just below the lip where the large, bulbous sclerites cease and only the smaller sclerites are present, arranged haphazardly ( Fig. 58 A).

Small (0.5– 0.15 mm long), narrow rodlets with sparse simple tubercles, often in girdles, occur in the pharynx ( Fig. 65 A). Overall they are not prolific; however they tend to occur more densely in line with the mesenterial attachments than in between them ( Fig. 65 B).

The cortex sclerites tend not to be thorn clubs with pointed tips as in the calyx, but more commonly are rounded, swollen sclerites covered in large, complex warts ( Fig. 66 A). The rounded ends of the sclerites project out from the surface of the colony. There tends to be a gradient from the largest bulbous sclerites, with the dense covering of complex warts (approximately 0.2–0.43 mm long), to narrower sticks and spindles, also with complex warts, right through to long sticks and spindles with simple tubercles (approximately 0.2–0.57 mm) ( Fig. 66 B). These sclerites are mixed together in the cortex with no discernible order to their placement.

The medulla sclerites resemble the simple sclerites from the cortex. There is a mixture of straight sticks and spindles with sparse, simple tubercles through to those with a denser arrangement of complex warts ( Fig. 67 ). Most of the sclerites with sparse tubercles range from 0.17–0.5 mm long but there are larger sclerites, up to 0.8 mm long. The sclerites with more complex warts and knobs range from 0.2–0.4 mm long.

The sclerites are all translucent and colourless under transmitted light.

Distribution: Gulf of Mexico, USA

Depth: 522 metres

Remarks: This specimen was first separated from the other Anthothela specimens using molecular results shared with the first author by Andrea Quattrini (Temple University, USA). Subsequent morphological investigation supported this separation due to the distinctive bulbous sclerites present in the calyx and surface of this specimen, not found in any other Anthothela species. The basic characteristics of the genus Anthothela are present, such as: the spatulate clubs crowded in the pinnules, sticks and spindles placed longitudinally (to en chevron) along the aboral side of the tentacle rachis, adjacent boundary canals separating the medulla and cortex, an absence of obvious internal medullary coelenteric canals, and multiple branch anastomoses.

A. quattriniae n. sp. is probably most closely related to the sympatric species Anthothela tropicalis which also has thorn clubs in the calyx and cortex. The holotypes from both A. tropicalis and A. quattriniae n. sp. were collected from similar geographic locations. However, the bulbous nature of the thorn clubs in A. quattriniae n. sp. distinguishes the species from A. tropicalis which has narrow, pointed thorn clubs (see Fig. 63 cf. Fig. 38 ). The size of sclerites may also be informative, however, unfortunately the fragment of the holotype of A. tropicalis examined here is very small, has many broken sclerites, and has only a single polyp, so comparisons of size of polyps and sclerites are prone to possible misinterpretation. No other specimen examined displayed the bulbous sclerites of A. quattriniae n. sp. Unfortunately, no specimens with the same morphological characteristics as A. tropicalis were available for molecular studies, but future comparisons of DNA sequences from A. quattriniae n. sp. and A. tropicalis may be elucidatory.

Other known Anthothela species all lack the bulbous spear-spindles present in A. quattriniae n. sp.

Etymology: The species was named in honour of Andrea Quattrini, then a fellow student from Temple University, California, USA, who recognised specimens she was working on were potentially Anthothela , and then shared these specimens and their DNA sequences with the first author.

Figures

FIGURE 38. Anthothela tropicalis Bayer, 1961, holotype, calyx sclerites: A. Thorn clubs; B. Spindles and sticks.

FIGURE 56. Anthothela quattriniae, n. sp., holotype: A. Colony; B. Fragments examined. (A. Courtesy of Andrea Quattrini and the Lophelia II program, US BOEM and NOAA OER).

FIGURE 57. Anthothela quattriniae, n. sp., holotype: A. Largest fragment examined; B. Branch tip.

FIGURE 58. Anthothela quattriniae, n. sp., holotype: A. Partly retracted polyp; B. Fully retracted polyp; C. Points and back of tentacles; D. Decalcified cross-section of branch.

FIGURE 59. Anthothela quattriniae, n. sp., holotype: Simple point and collaret sclerites.

FIGURE 60. Anthothela quattriniae, n. sp., holotype: Bulbous point sclerites.

FIGURE 61. Anthothela quattriniae, n. sp., holotype: A. Tentacular and point sclerites in situ; B. Tentacle rachis sclerites.

FIGURE 62. Anthothela quattriniae, n. sp., holotype, sclerites: Pinnule.

FIGURE 63. Anthothela quattriniae, n. sp., holotype: Bulbous calyx sclerites (a. sclerites lacking a spear tip).

FIGURE 64. Anthothela quattriniae, n. sp., holotype: Simple calyx sclerites.

FIGURE 65. Anthothela quattriniae, n. sp., holotype: A. Pharyngeal sclerites; B. In situ arrangement of pharyngeal sclerites.

FIGURE 66. Anthothela quattriniae, n. sp., holotype: A. Bulbous cortex sclerites; B. Simple cortex sclerites.

FIGURE 67. Anthothela quattriniae, n. sp., holotype, sclerites: Medulla.