Research Article |
Corresponding author: Sérgio N. Stampar ( sergiostampar@gmail.com ) Academic editor: James Reimer
© 2018 Sérgio N. Stampar, Suraia O. El Didi, Gustav Paulay, Michael L. Berumen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Stampar SN, El Didi SO, Paulay G, Berumen ML (2018) A new species of Arachnanthus from the Red Sea (Cnidaria, Ceriantharia). ZooKeys 748: 1-10. https://doi.org/10.3897/zookeys.748.22914
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A new species of the genus Arachnanthus (Cnidaria: Ceriantharia), Arachnanthus lilith Stampar & El Didi, sp. n., is described. This species is widely distributed in the Red Sea, and recorded from 2–30 m depths. Arachnanthus lilith Stampar & El Didi, sp. n. is the fifth species of the genus and the first recorded from the Red Sea. The number of labial tentacle pseudocycles, arrangement of mesenteries, and distribution of acontioids allow the differentiation of the new species from other species of the genus.
Anthozoa , biodiversity, coral reefs, Indo-West Pacific, marine invertebrates, taxonomy
While tube anemones are common objects for underwater photographers and are widely exhibited in aquaria, they remain undersampled in most regions of the world, and the diversity and distribution of species remains poorly documented (
Specimens were collected by hand at three sites across the Red Sea, from the Gulf of Aqaba to the Farasan Islands, in Saudi Arabia (Fig.
The anatomical study of polyps and cnidome were based on characters defined by previous authors (
The classification of cnidae follows
Arachnactidae with sterile protomesenteries; metamesenteries in duplets (M and B), long (‘M’) metamesenteries with gonads and a double mesenteric filament, short (B) betamesenteries sterile, with single, convoluted mesenteric filament; very long stomodeum; lacking a directive labial tentacle; cnidome with p-mastigophores and b-mastigophores (after
Arachnanthus oligopodus (Cerfontaine, 1891)
Arachnanthus australiae Carlgren, 1937
Arachnanthus bockii Carlgren, 1924
Arachnanthus oligopodus (Cerfontaine, 1891)
Arachnanthus sarsi Carlgren, 1912
Arachnanthus lilith sp. n.
North Sea, Mediterranean Sea, Red Sea, East Australia, and Melanesia.
Holotype: UF Cnidaria 9168, adult individual (35 mm long), Saudi Arabia, island near Jaz’air Sila, (27.651°N, 35.2832°E) (Fig.
Arachnanthus lilith sp. n. A (Paratype UF Cnidaria 9227) (not to scale) B (Paratype UF Cnidaria 9168) (not to scale) C–D Live specimens in nature (not included as paratypes – ICZN 72.4.6) (not to scale) E Dissected specimen with detail of acontioids (arrows) (scale bar 2 mm) UF Cnidaria 9168 (Holotype) F Detail of oral disc UF Cnidaria 9229 (Paratype) with detail on tentacular pores with green fluorescent protein (GFP) (arrows) (not to scale).
Small ceriantharian, up to at least 42 mm long, 4–6 mm wide. With 19–24 translucent marginal tentacles (3–5 mm long in preserved specimens), each with 2–4 brown bands (Fig.
Cnidome of Arachnanthus lilith sp. n. based on two specimens (UF 9229; 9168). Mean and range given for each cnida.
Length (in µm) | Width (in µm) | ||
---|---|---|---|
Column | Pytchocysts | 40.69 (37.7–44.2) | 9.18 (9.1–10.4) |
Atrichs | 48.57 (41.6–53.3) | 8.01 (6.5–10.4) | |
b-mastigophores I | 32.32 (31.2–33.8) | 4.11 (3.9–5.2) | |
p-mastigophores I | 86.45 (83.2–89.7) | 21.49 (19.5–23.4) | |
Marginal tentacles | p-mastigophores I | 84.15 (78.0–91.0) | 19.84 (18.2–20.8) |
p-mastigophores II | 33.75 (31.2–37.7) | 6.84 (6.5–7.8) | |
b-mastigophores I | 32.63 (31.2–33.8) | 3.9 (3.8–4.0) | |
b-mastigophores II | 21.06 (19.5–27.3) | 4.11 (3.9–5.2) | |
Atrichs | 34.92 (31.2–39.0) | 6.58 (5.2–7.8) | |
Labial tentacles | p-mastigophores I | 64.87 (61.1–67.6) | 13.08 (11.7–14.3) |
b-mastigophores II | 25.3 (20.8–28.6) | 5.07 (3.9–7.8) | |
Atrichs | 25.69 (24.7–28.6) | 6.02 (5.2–6.5) | |
Stomodeum | p-mastigophores I | 49.44 (45.5–54.6) | 9.83 (7.8–11.7) |
b-mastigophores II | 24.05 (20.8–26.0) | 5.76 (5.2–6.5) | |
Atrichs | 33.28 (31.2–35.1) | 6.54 (5.2–7.8) | |
Betamesenteries | p-mastigophores I | 83.8 (80.6–89.7) | 23.14 (19.5–24.7) |
p-mastigophores II | 54.9 (52.0–58.5) | 15.34 (13.0–16.9) | |
b-mastigophores II | 19.24 (15.6–23.4) | 4.03 (3.9–5.2) | |
Metamesenteries | b-mastigophores II | 25.04 (23.4–26.0) | 5.76 (5.2–6.5) |
b-mastigophores III | 17.76 (16.9–18.2) | 4.2 (3.9–5.2) |
Graphical representation of the arrangement of mesenteries of Arachnanthus lilith sp. n. Abbreviations: M.C. multiplication chamber, D directives, T.P. terminal pore, S siphonoglyph, B betamesenteries (convoluted mesentery), M metamesenteries (double filament), P protomesenteries, AC acontioids
Presently known only from the Saudi Arabian Red Sea, from the Gulf of Aqaba to the Farasan Islands in the southern Red Sea. The species was found extended only at night.
The specific name lilith refers to the mythological figure of a female night demon in the vicinity of the Red Sea to ancient Mesopotamia (Saudi Arabia to Iraq).
Column pinkish tan at basal half or along most of its length, becoming clear toward base of tentacles. Marginal tentacles whitish/transparent, with brown and light green bands; extent of banding variable, with a basal brown band commonly developed. Labial tentacles clear to brown, with whitish base and tips. Oral disk with green and white colors.
(UF Cnidaria 9168). Small polyp, 35 mm long, 4 mm in diameter just below the marginal tentacles, 3 mm diameter near aboral end. With 19 marginal tentacles arranged in two pseudocycles, each 4 mm long and 0.5 mm in diameter near base, tentacle arrangement (1)2.12.12.12.12…. With 12 labial tentacles, each ~1 mm long, brown with a white apical tip, directive labial tentacle absent, tentacle arrangement (0)3.12.31.23.12…. Oral disc 0.7 mm wide, actinopharynx 17 mm long, light beige to light brown, siphonoglyph wide and elongate with eight mesenteries attached, hyposulcus 9 mm long. Directive mesenteries shorter than actinopharynx. Protomesenteries as in diagnosis, M-mesenteries (M), long, fertile with a double mesenteric filament; B-mesenteries (B) short, sterile with single mesenteric filament (double in a short part immediately below actinopharynx) and rather convoluted; acontioids only in mesenteries M3 and M4.
Although
Comparison of anatomical features of species of Arachnanthus (after
A. australiae | A. bockii | A. oligopodus | A. sarsi | A. lilith sp. n. | |
---|---|---|---|---|---|
Marginal tentacles | Up to 40 | Up to 30 | ~20 | Up to 35 | Up to 24 |
Arrangement of labial tentacles | (0)1.11.11.11.11 | (0)1.11.11.11.11(?) | (0)1.11.11.11.11 | (0)1.11.11.11.11 | (0)3.12.31.23.23.12 |
Length of actinopharynx | ~2/3 of gastric cavity | ~1/2 of gastric cavity | ~1/2 of gastric cavity | ~1/2 of gastric cavity | >1/2 of gastric cavity |
Hyposulcus | ~1/2 size of stomodeum | ~1/2 size of stomodeum | ~2X size of stomodeum | < size of stomodeum | = size of stomodeum |
Oral disc diameter | ~0.7 cm | – | – | ~1 cm | 0.5 cm |
Maximum n° of mesentery attached to siphonoglyph | 12 | 12 | 4 | 6 | 8 |
Directive mesenteries | = length of Actinopharynx | < length of Actinopharynx | > length of Actinopharynx | < length of Actinopharynx | < length of Actinopharynx |
P(C)2 | Short, 1/2 of gastric cavity | Very short, 1/4 of gastric cavity | Short, 1/2 of gastric cavity | Long, 3/4 of gastric cavity | Long, 6/7 of gastric cavity, almost to aboral pole |
P(C)3 | Very short, <1/4 of gastric cavity | Very short, <1/4 of gastric cavity | Short, ~1/2 of gastric cavity | Short, ~1/3 of gastric cavity | Short, 1/3 of gastric cavity |
M1 | Almost to aboral pore | Almost to aboral pore | To aboral pore | Almost to aboral pore | To aboral pore |
M3 | 4/5 of gastric cavity | Almost to aboral pore | 1/5 of gastric cavity | Almost to aboral pore | 3/4 of gastric cavity |
Cnido-glandular tract of fertile mesenteries | Present (short?) | Present (short?) | Present | Present | Present |
Cnido-glandular tract of B | Present (short?) | Present (short?) | Present (short?) | Present (short) | Present (short) |
Acontioids | Only in M1, M2 and M3 | Only in M1, M2 and M3 | Only in M1 | Only in M1, M2 and M3 | Only in M3 and M4 |
Distribution | Northern Australia | Fiji | Mediterranean Sea | North Sea | Red Sea |
Arachnanthus lilith has labial tentacles in three pseudocycles, unlike A. australiae, A. oligopodus, and A. sarsi, which all have them in one pseudocycle, while in A. bockii labial tentacles are not clearly organized and may be considered to fall into one or two pseudocycles. The actinopharynx is 2/3 as long as the gastric cavity in A. australiae, less than ½ as long in the other three described species, and a little over ½ as long in A. lilith. The maximum number of the mesenteries attached to the siphonoglyph is especially useful for distinguishing species: A. australiae and A. bockii have 12 each, A. lilith has eight, A. sarsi six, while A. oligopodus has four. The organization of mesenteries, particularly the mesentery P2 and M3, also provides useful characters to separate species (Table
Finally, the present study demonstrates the importance of more detailed investigations using non-standard collecting techniques. Small ceriantharians are rarely collected as they are frequently nocturnal and can be difficult to extract from the sediment as they retract quickly and rapidly. There are few described species of Ceriantharia with small body sizes; however, this may be the result of sampling limitations.
SED is thankful to the CNPq for a fellowship. This work was partly supported by São Paulo Research Foundation FAPESP 2015/24408-4, 2016/50389-0, 2017/50028-0, CNPq 404121/2016-0 and CAPES/CNPQ – PROTAX II 88882.156878/2016-01 to SNS, as well as the King Abdullah University of Science and Technology (award number CRG-01-BER-2012-002 to MLB). We are also grateful to Drs. Bert W. Hoeksema and Kensuke Yanagi for their helpful comments and suggestions.