Anthothela tropicalis Bayer 1961
Creators: name: Moore, Kirrily M.
name: Alderslade, Philip
name: Miller, Karen J.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Alcyonacea
Anthothelidae
Anthothela
Anthothela tropicalis

description: Anthothela tropicalis Bayer, 1961
(Figs. 32–41)
Anthothela tropicalis Bayer, 1961: 68, Fig. 13.
Material examined. Holotype: USNM 50650, southeast of Galveston, Texas, Gulf of Mexico, Oregon stn. 534, 27.533°N, 93.027°W, depth 732–823 m, 11th April 1952.
Other material: USNM 1090549, St. Augustine, Reed Peak #160, Atlantic Ocean, 29.849°N, 79.633°W, depth 742–828 m, 9th Nov 2005.
Description:
Colony form: According to Bayer (1961), originally the holotype was a rambling colony with “crooked” branches forming a “tangled mass” with no central stem; he figured only a small fragment (Fig. 32 A). The holotype now consists of seven fragments (Fig. 32 B); five of these are straight to slightly bent pieces of branch and two are pieces of tangled branch with anastomoses evident. There is no central stem or obvious holdfast. There are many calyces present but very few remaining polyps. The calyces apparently were “widely separated on all sides” but no distances between calyces or measurements of colony surface without polyps were given. On the holotype fragments, calyces are evident on all sides of the branches and distributed evenly throughout. There is no mention or evidence of clumps of polyps which is a common feature in other species of Anthothela. Only a tiny fragment of the holotype was examined for this study (Fig. 32 C) so parts of the original description have been incorporated here. The fragment is 1.9–2.1mm in diameter (which corresponds with “about 2.0 mm” from Bayer) and is basically circular in cross-section.
Colour: According to Bayer, “the colonies (sic) are ivory white in alcohol”. The fragment examined here is also white in alcohol. There is no mention of live colour.
Polyps and calyces: Calyces, as described by Bayer, are cylindrical in shape, “about 1.5 mm tall” and 2–3 mm wide from his figure (Fig. 32 A). Bayer does not give the dimensions of polyps in the text but from the figure the head of the polyp extends approximately 2 mm from the lip of the calyx and is 1.8–2 mm wide. Most of the polyps were preserved exsert although Bayer mentions that the “polyps are fully retractile”, and in his figure a polyp head is partly retracted such that the base of the polyp head rests on the lip of the calyx (Fig. 32 A). One of the few remaining polyps visible on the holotype fragments resembles that figured by Bayer (Fig. 32 Ba).
The fragment examined here has two mound-shaped calyces which are approximately 1.2 mm tall and 2 mm wide with no discernible ridges. The single polyp present is fully retracted within its calyx and appears poorly developed—it may in fact be a juvenile polyp (Fig. 32 Ca). The calyces and the colony surface are covered in large sclerites which have a projecting tip, giving the colony a very prickly appearance (Fig. 32 D). The polyp head has sclerites arranged in a distinct collaret and points (Fig. 33 A) and the tentacles are folded tightly into the mouth forming eight mounds and furrows, giving the top of the polyp a starred appearance. A single row of approximately 10 pinnules are arranged along each side of the tentacles but it was impossible to accurately determine the number of pinnules with the material available.
Medulla and Cortex: Bayer included a figure of a cross-section of the colony (Fig. 32 Aa), and a cross-section from the fragment of holotype here generally confirms this figure (Fig. 33 B). The branch fragment consists of a medulla of tightly packed sclerites, longitudinally or obliquely arranged, surrounded by a thin cortex. The cortex and the medulla are separated by a series of longitudinal canals, running adjacent to each other and so close as to form a circle of boundary canals. They are, however, still discernible as individual canals and do not appear to frequently anastomose. There is no evidence, either in Bayer’s figure or the small cross-section taken here, of internal coelenteric canals within the medulla. However, Bayer qualifies his description by admitting that the “material is not sufficiently well-preserved to determine the extent to which the medulla is penetrated by solenia”. There is insufficient material to investigate the canal arrangements any further.
Sclerites: The polyp head is covered in closely packed sclerites, with approximately 10 transverse rows of sclerites forming a collaret and others arranged en chevron to longitudinally in eight points. These sclerites (0.2– 0.87 mm long) are mainly curved or straight sticks and spindles with relatively simple tubercles (Fig. 34). Occasionally in the points, there are sclerites where one end has developed short spines or thorns and these are positioned such that these tips project above the base of the folded tentacles (Fig. 35). It was impossible to adequately determine the arrangement of the sclerites on the polyp neck due to the limited material available.
The tentacles are crowded with sclerites that are arranged longitudinally along the aboral side and angled obliquely on the flanks. They are mostly short tuberculate rods, usually straight, sometimes curved, and are approximately 0.1–0.4 mm long (Fig. 36 B). Bayer mentions that the tentacle sclerites have “spines larger at one end than elsewhere” and includes them in his figure (Bayer, 1961 Fig. 13 a). A few sclerites like those figured were found in this study (Fig. 36 Ba) although they were not the dominant sclerite type in the tentacles. However, not specifically mentioned by Bayer is the fact that the pinnules are packed with longitudinally arranged spatulate clubs, with an enlarged and flattened tip, along with some simple small tuberculate rodlets, particularly in the tip of the tentacle (Fig. 36 A). Sclerites from the pinnules range in size from 0.06–0.35 mm long, with the spatulate clubs falling mainly into the range of 0.19–0.35 mm long.
Bayer mentions that the pharynx has “numerous slender, spinose spindles about 0.1 mm long”. In this study sclerites were found to be very numerous and densely arranged throughout the pharynx, leaving very little free tissue (Fig. 37 A, B). They are small, slender spindles with sparse, small tubercles, approximately 0.05–0.12 mm long (Fig. 37 C).
The calyces and cortex are covered with tightly packed, relatively large sclerites with projecting tips, making the calyces and colony surface very prickly (Fig. 32 D). These sclerites are usually strongly bent or curved and are mostly covered in simple to quite complex tubercles (Figs. 38 A; 39A) except at the tips which have foliose and flattened thorns but little or no tuberculation directly on the smooth spines. These sclerites are termed “bent hockey-stick spindles” by Bayer but conforming to the much later published octocoral glossary (Bayer et al. 1983), they are here termed thorn clubs. These thorn clubs range in length from 0.28–0.68 mm long in the calyx. In the cortex, the thorn clubs tend to be of similar size (0.33–0.78 mm long) but there are more numerous small ones (Fig. 39 A). Mixed in with the thorn clubs, in both the calyces and cortex, are straight or slightly curved tuberculate spindles and sticks (Figs. 38 B; 39B). These range in length from 0.18–0.6 mm long in the calyx and 0.33–0.57 mm in the cortex where they appear to be more common. This supports Bayer’s description where he stated “in the cortex [the bent hockey-stick spindles] are smaller and many ordinary spindles are mixed with them”.
Sclerites in the medulla are mostly long, narrow sticks and spindles with sparse, simple tubercles (Fig. 40). Occasionally, there are large sclerites with a greater covering of tubercles or warts. In the small sample taken here the sclerites ranged from 0.32–0.66 mm long, although Bayer mentions that the medulla sclerites often exceed “a length of 0.5 mm ”. There is evidence of sclerites occasionally fusing and branching.
The sclerites are all translucent and colourless under transmitted light.
Variability: The tiny fragment of USNM 1090549 (Fig. 41 A) examined consists of only three polyps arranged as a terminal branch cluster (Fig. 41 B). The sclerites differ slightly from the holotype in having more numerous thorn clubs in the points. The polyps and calyces are taller and narrower than those from the holotype (calyx 2.2 mm high with the polyp fully extended 3.4 mm above that; polyp head 1.6 mm wide) but the colony has the spiky surface characteristic of A. tropicalis and, apart from those in the pharynx, the other sclerites correspond with those of the holotype. In the pharynx, it has only loosely arranged sclerites and lacks the densely arranged pharynx sclerites found in the holotype, however the taxonomic importance of this character is unproved. This specimen is from the east coast of Florida.
Distribution: Gulf of Mexico; northern Atlantic Ocean off the coast of Florida, USA.
Depth: 732–828 metres.
Remarks: Regretfully, there are very few polyps remaining on the holotype, and only a tiny fragment was available for study. Nevertheless, further specimens are likely to be collected in the future. In fact, in Bayer’s description he mentioned “colonies are white in alcohol” so although he only explicitly mentioned and figured the holotype he appeared to have more than one specimen at his disposal.
Of the specimen USNM 1090549, a similarly small fragment was available for study. Unfortunately, with so little material available, the phylogenetic importance of calyx and polyp form and size is impossible to assess. Geographic proximity and the presence of large thorn clubs in the calyx and cortex are the main features tying these specimens together. Future research, particularly some molecular analysis not possible for these specimens, may also assist with this species delineation.
Distinguishing A. tropicalis from other species in Anthothela centres on the presence and, in fact, dominance of the characteristic thorn clubs in the calyx and surface. A. grandiflora has, at times, quite complex sclerites in the calyx but it does not have the true thorn clubs with smooth, sharply pointed tips. Consequently, the surface and calyces of A. grandiflora are not as thorny as those of A. tropicalis. Additionally, sclerites in the pharynx are always sparsely arranged in A. grandiflora while those in the A. tropicalis holotype are crowded, with little scleritefree tissue.
A specimen collected from a location very close to that of the holotype of A. tropicalis is herein described as the new species A. quattriniae. It too has thorn clubs in the calyx and surface of the colony but these thorn clubs are bulbous and swollen (Fig. 63).
Bayer compared A. tropicalis with A. pacifica, calling them “a twin pair”, one from the Pacific Ocean and one from the Gulf of Mexico. He claims A. tropicalis has “smaller and more numerous spicules in the crown and a broader collaret”. In fact, the lectotype of A. pacifica has very small sclerites, in general much smaller than those of A. tropicalis. Using the limited material from both type specimens here, it appears A. pacifica lacks the large, bent thorn clubs of A. tropicalis, instead having straight clubbed sclerites in the calyx and points.
A. aldersladei n. sp. has thorn clubs dominant in the calyx and surface but they are usually shorter than those in A. tropicalis (0.19–0.54 mm cf. 0.33–0.78 mm). In the surface of A. aldersladei n. sp. the small thorn clubs are almost exclusive with very few straight sticks and spindles as opposed to A. tropicalis which has a far higher percentage of the latter mixed in with the thorn clubs. Additionally, A. aldersladei n. sp. has very large points and collaret sclerites relative to the size of the polyp. At this stage, A. aldersladei n. sp. has only been recorded from the Indian Ocean, in waters off Western Australia.
A. vickersi n. comb. is a very similar species to A. tropicalis. It has similar sized thorn clubs in the calyx but they only rarely occur in the surface. The surface sclerites of A. vickersi n. comb. are a mixture of straight, tuberculate sticks and spindles with numerous short, rounded clubs with a slightly developed tip which A. tropicalis lacks. Additionally, A. vickersi n. comb. has only been recorded from the southern Pacific Ocean.
Finally, Bayer mentions that in A. tropicalis, the polyps are “widely separated on all sides”. This might be considered a difference with other Anthothela species which all tend to have polyps closely bunched and, at times, quite crowded.
description: Published as part of 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, pp. 1-212 in Zootaxa 4304 (1) on pages 56-67, DOI: 10.11646/zootaxa.4304.1.1, http://zenodo.org/record/842289