Xenia umbellata Lamarck 1816
Creators: name: Halász, Anna
name: Mcfadden, Catherine S.
name: Toonen, Robert
name: Benayahu, Yehuda
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Alcyonacea
Xeniidae
Xenia
Xenia umbellata

description: Xenia umbellata Lamarck, 1816
Figs. 16–22
Xenia umbellata Lamarck, 1816: 403
Xenia umbellata:; Savigny 1817: 227 fig. 3; Ehrenberg 1834: 53–54; Klunzinger 1877: 39–40 fig. 3; Schenk 1896: 57; May 1899: 16–18; May 1899: 82–84; Ashworth 1900: 513–516 Figs. 10–13; Kükenthal 1902: 650–651; 1904: 34; Thomson and Henderson 1905: 273; 1906: 410–411; Thomson & McQueen 1907: 50; Gravier 1908: 206–207; Kükenthal 1913: 7; Thomson & Dean 1931: 26–27; Hickson 1931a: 156–157; Roxas 1933: 88–89 fig. 3; Gohar 1940: 93–95; Verseveldt 1965: 46–47; Tixier-Durivault 1966: 367, fig 330; Verseveldt 1971: 63; Utinomi 1977; Benayahu 1990: 118, table 1, listed only; Imahara 1996; Reinicke 1997; Benayahu et al. 2002: 279, table 1, listed only; Haverkort-Yeh et al. 2013; Janes et al. 2014.
Material. Neotype: ZMTAU CO 36788, northern Red Sea, Gulf of Aqaba, Eilat, reef across from the Interuniversity Institute for Marine Sciences in Eilat (IUI) (29°30'14.508"N, 34°55'9.84"E), 12 m, 19 March 2010. Additional material: ZMTAU CO 36780, northern Red Sea, Gulf of Aqaba, Eilat, IUI (29°30'6.54''N; 34°55’4.44''E), 5 m, 5 January 2010; ZMTAU CO 36792, northern Red Sea, Gulf of Aqaba, Eilat, the Pyramid site, on artificial reef (29°32'44.7"N, 34°57'26.3154"E), 22 m, 30 June 2010; ZMTAU CO 37034, northern Red Sea, Gulf of Aqaba, Eilat, Underwater restaurant, on artificial reef (29°32'49.43N; 34°57'14.51''E), 8 m, 22 June 2010. ZMTAU CO 36783, collection details as ZMTAU CO 36780; ZMTAU CO 36784, northern Red Sea, Gulf of Aqaba, Eilat, Dekel beach (29°32'26.1708"N, 34°56'52.731"E), 5 m, 26 January 2010; ZMTAU CO 36790, northern Red Sea, Gulf of Aqaba, Eilat, Tur Yam (29° 30' 56.4978"N, 34° 55' 36.1986"E), 5 m, 4 May 2010; ZMTAU CO 36791, northern Red Sea, Gulf of Aqaba, Eilat, Underwater restaurant (29°32'49.43N; 34°57'14.51''E), 11 m, 23 June 2010. All of the above collected by A. Halász; USNM 1202005, Saudi Arabia, Jeddah, 21°43'N, 39°06'E, 23 April 2011; USNM 1202010, same details; USNM 1202016, same details. All USNM material above collected by R. Haverkort-Yeh; ZMTAU CO 34073, northern Red Sea, Gulf of Aqaba, Eilat, Nature reserve, (29 o 30.6'N, 34 o 55.35'E), 2.4–5.5 m, 24 July 2007, coll. Y. Benayahu; ZMTAU CO 34072, same collection details as above.
Description. The neotype, ZMTAU CO 36788, consists of one colony growing on a dead colony of a branched stony coral. Its maximal height is 20 mm; the stalk is unbranched, up to 5 mm long and 8 mm wide. The polyp body is up to 4 mm long, and the tentacles up to 3.5–5 mm long. The slender pinnules are up to 2.5 mm long and 0.2 mm wide, with a pinnule-wide space between them. The pinnules are arranged in three rows with 19–22 in the outermost one.
Sclerites are ellipsoid platelets, abundant in all parts of the colony, measuring 0.008 –0.015 X 0.013 –0.025 mm in diameter (Fig. 16, n=20). They are composed of calcite rods, uniform in width (0.1–0.2 µm). The rods are arranged more or less randomly and their distal tips are aligned in part parallel to the surface of the sclerite (Fig. 16b, c). Clusters of sclerites are densely packed in different spatial orientations (Fig. 16d). The ethanol-preserved neotype is white. Pulsation was observed in live colonies.
The additional material, ZMTAU CO 36780, is 22 mm high. Its stalk splits into 3 branches 5 mm above its base, the branches are 9, 15 and 7 mm long; 5, 10, and 5 mm wide at their base; and 12, 13 and 7 mm wide at their uppermost part, respectively. The polyp body, tentacles and pinnules are similar in size to those of the neotype. The pinnules are arranged in three rows, 20–23 in the outermost row. Sclerites are abundant in all parts of the colony and are similar to those of the neotype, measuring 0.011 –0.015 X 0.014 –0.023 mm in diameter (Fig. 17, n=20). Their surface reveals a partially granular texture, but in addition the longitudinally aligned dendritic rods can be seen on the surface of the sclerites.
ZMTAU CO 36792 is similar in dimensions to the neotype. Pinnules are arranged in three rows, 22–27 in the outermost row. Sclerites are abundant in all parts of the colony, and their morphological features—including surface texture (Fig. 18)—are similar to those of the neotype, measuring 0.011 –0.015 X 0.017 –0.022 mm in diameter (n=20).
ZMTAU CO 37034 consists of three small white-beige colonies. The first is a colony with multiple branches; its total height is 20 mm, and the stalk is up to 13 mm wide at its base and 25 mm wide at its uppermost part. The second colony is unbranched, similar in height to the first, 10 mm wide at its base, and 4 mm wide at its uppermost part. The third colony is 15 mm high; its stalk branches into three, and its base is 10 mm wide and 30 mm at the uppermost part at the branching point. The tentacle and pinnule dimensions are similar to ZMTAU CO 36780. The pinnules are arranged in three rows, 19–22 in the outermost row. Sclerites are scarce, ellipsoid platelets, round or egg-shaped and occasionally irregular, measuring 0.009 –0.017 X 0.015 –0.022 mm in diameter (Fig. 19, n=20). Their surface microstructure (Fig. 19a) is similar to that of the neotype (Fig. 19b). Sinuous dendritic rods are radially arranged, and can be seen in a fractured sclerite (Fig. 19c).
The size of all other colonies is rather similar to that of the neotype. ZMTAU CO 36783, 36790, 36791, USNM 1202005 and 1202016 feature three rows of pinnules with 21–24, 17–20, 18–20, 19–26 and 21–27 pinnules in the outermost row, respectively. ZMTAU CO 36784 and USNM 1202010 bear two rows of pinnules with 16–20 and 20–24 pinnules in the outermost row, respectively. Polyp sclerites of the three colonies collected in Saudi Arabia (USNM 122005, 1202010 and 1202016) all share a similar microstructure to that of the neotype and the Eilat colonies (Figs. 20, 21 and 22 respectively). Their sclerites typically maintain their intact shape following processing for SEM and only occasionally feature small marginal fractures (Fig. 22). Pulsation was observed in all live colonies.
Phylogenetic affiliation. All of the X. umbellata colonies described above shared identical DNA sequences at mtMutS, igr1+COI, and 28S rDNA (Fig. 23); species delimitation analyses that included those loci plus four additional genes further supported the conclusion that all of the X. umbellata specimens examined here belong to one species (McFadden et al. 2017). Two specimens previously identified as X. hicksoni (ZMTAU Co34072, 34073; McFadden et al. 2011) were also genetically identical to X. umbellata (Fig. 23). X. umbellata belonged to a strongly supported clade that included members of the genus Ovabunda from the Red Sea and Thailand (Fig. 23). This [Ovabunda + X. umbellata] clade was nested within a larger clade of Xenia that included specimens previously identified as X. lepida, X. ternatana and X. viridis (clade X1 of McFadden et al. 2014a). Additional species of Xenia, including material identified as X. sansibariana (= X. actuosa; Haverkort-Yeh et al. 2013) belonged to a second distinct clade that also included species of Heteroxenia (clade X2 of McFadden et al. 2014a). Finally, specimens identified previously as X. kusimotoensis and X. membranacea belonged to a clade with species of Sansibia, Sarcothelia and Yamazatum (clade X3; McFadden et al. 2014a).
Remarks. In the original description of X. umbellata, the type species of this genus, Lamarck (1816: 410) referred to dark-blue colonies from the Red Sea, bearing slender, tightly packed pinnules, arranged in two rows. Lamarck referred to drawings of colonies collected from the Red Sea that were published by Savigny (1817). Based on these drawings it is evident that the tentacles feature two rows of pinnules with 27–32/22–25 and 30–35/ 29–31 pinnules in the outer/inner row (Reinicke 1997: Fig. 18). No additional data were presented regarding the sclerite shape and dimensions or the exact type locality. Inquiries to various collections, including MNHN, led to the conclusion that the type should be considered lost (see also Reinicke 1997).
Since the original description of X. umbellata by Lamarck (1816), specimens collected from many Indo-Pacific reefs were referred to this species (see ahead), also attributing to it rather variable morphological features. Undoubtedly, the extensive literature has made it the most common Xenia species reported in the entire Indo-Pacific region, giving the impression that it is the commonest species of its genus. In contrast to the two rows of pinnules indicated in the original description by Lamarck (1816: 410), Ehrenberg (1834: 53–54) described this species from the Red Sea as having three rows. That study established the notion that three rows of pinnules should be attributed to X. umbellata. Subsequently, other studies referred to X. umbellata as featuring a different number of rows and also with a wide range of pinnule numbers in the outermost row compared to Lamarck's (1816) description. For example, Schenk (1896: 57) indicated three rows and 12–15 pinnules (Ternate, Indonesia); Ashworth (1900) 3–4 rows and 12–15 pinnules (Red Sea); and three rows, 22–29 pinnules (Papua New Guinea: New Britain). Subsequently, Kükenthal (1902: 561) indicated three rows, 12–29 pinnules in the outermost row (Red Sea, Indian Ocean, East Africa and Papua New Guinea: New Britain). Hickson's (1931a) revision of the Xeniidae described material collected in the Great Barrier Reef with three rows of pinnules and about 25 pinnules in the outermost row, and sclerites “round in outline”, 0.020 mm in diameter. That study also noted the resemblance to X. plicata. Roxas (1933) described X. umbellata as having three rows of pinnules, 17–20 in a row, and sclerites 0.014 –0.018 X 0.010 –0.018 mm in diameter (Puerto Galera Bay, Philippines). Gohar (1940) referred to pulsating colonies of X. umbellata from Hurgada, Red Sea, featuring 2–3 rows of pinnules and 16–22 pinnules in the outermost row (14–18 and 10–12 in the inner rows), and sclerites with a maximal diameter of 0.016 –0.022 mm. He further described the sclerites as: “general xeniid structure, minute, roughly circular, oval or slightly oblong corpuscles”. Later, Verseveldt (1971) reported the species from Madagascar, referring to Gohar’s description. Utinomi (1977) reported it from Okinawa, Japan, with 2–3 rows of pinnules, 15–17 in the outer row. Imahara (1996) noted the presence of the species from the same location and referred to the description by Utinomi (1977). Reinicke (1997: 19; Fig. 8a) depicted sclerites of X. umbellata collected in the Red Sea, and presented its sclerite surface microstructure for the first time using SEM. Undoubtedly, these studies may have raised confusion concerning the real identity of the species and its taxonomic features.
The Red Sea material examined in the current study, including the neotype and the additional material, encompasses 2–3 rows. The recorded number of pinnules in the outermost rows is mostly 19–22, but occasionally up to 27 or as few as 16, but not lower than that. These findings correspond to those of some of the previous taxonomic studies on this species (see above). Despite the variation attributed to the Red Sea colonies, they share a similar sclerite microstructure (Figs. 16–19) and identical DNA sequences at the molecular markers analyzed here (Fig. 23). It should also be noted that there is variation in the abundance of sclerites in the colonies: while they are usually abundant in all parts of the colony, they can also be scarce, but then confined mainly to the colony base.
The purpose of the designation of the neotype is to clarify the species’ taxonomic status, and to provide an account of its soft tissue morphological features, its sclerite microstructure and its genetic affiliation. The designation of the neotype is conducted here not within the framework of a full taxonomic revision of the genus Xenia, but rather is based on a comprehensive examination and re-description of 21 original Xenia types, including some from the Red Sea. It should also be noted that attempts to obtain additional types of the genus failed. This approach allows us to designate a neotype despite the convention that designation of neotypes is made only within the framework of a full revision of a genus (http://iczn.org/nontaxonomy/term/540). The original description of X. umbellata indicated that the species had been collected in the Red Sea, but without providing an exact location. Therefore, it is fully justified that the currently designated neotype as well as the additional material used for comparison, have been collected in Red Sea sites: Eilat and Saudi Arabia.
The geographical distribution of X. umbellata based on the literature encompasses regions and sites across the Indo-Pacific reef systems. It includes the Pacific Ocean: Japan (e.g. Utinomi 1977; Imahara 1996), Indonesia (Schenk 1896), the Philippines (Roxas 1933), Papua New Guinea: New Britain (Ashworth 1900) and the Great Barrier Reef, Australia (Hickson 1931a); Indian Ocean: Zanzibar and Madagascar (e.g. Tixier-Durivault 1966; Verseveldt 1971), and the Red Sea (e.g. Ehrenberg 1834; Gohar 1940, Benayahu 1990, Benayahu et a l. 2002). In agreement with the note published by Reinicke (1997), as well as recent genetic insights into xeniid biogeography (McFadden et al. 2019), records from locations outside the Red Sea should be re-evaluated to determine if those specimens indeed share features of the neotype that had not been indicated previously, specifically its sclerite microstructure and genetic affiliation.
Similar species and conclusions. X. umbellata, X. blumi, X. ternatana and X. viridis all possess three rows of pinnules and have overlapping numbers of pinnules in the outermost row (16–27, 16–22, 15–23 and 15–22, respectively). All have sclerites that are composed of calcite rods, uniform in width, although X. ternatana and X. viridis also feature surface crests (Figs. 14 and 15, respectively). The sclerites of X. umbellata differ from those of the other three species, as the tips of the rods are aligned parallel to the sclerite surface and are sinuous (Figs. 16– 22), unlike those of other Xenia species, which are radially arranged and terminate vertically towards the sclerite surface (Figs. 1–15). Therefore, it is concluded that such differences in sclerite microstructure along with the distinct phylogenetic position of X. umbellata from the Red Sea compared to other Xenia species make X. umbellata unique and justify its designation as a separate species (see also Fig. 23).
X. hicksoni Ashworth, 1899 also resembles X. umbellata. It was described from Indonesia (Talisse, north Celebes) as bearing three rows of pinnules, 12–20 pinnules per row, with no sclerites in the tentacles and pinnules. Later, Roxas (1933) described it from the Philippines with three rows of pinnules, 16–18 pinnules in the outermost row, and numerous sclerites. Gohar (1940) examined the type and concluded that it is a good species, adding some notes on specimens he had collected in the Red Sea (Hurgada). That study also noted pulsating colonies of X. hicksoni, smaller than X. umbellata, bearing 2–3 rows of pinnules, 18–26 in the outermost row, with the sclerites appearing in patches throughout the colony, “unevenly scattered on the surface” (Gohar, 1940: 96). Accordingly, X. umbellata and X. hicksoni seem to share some similar morphological features of their soft tissue. Both species have 2–3 rows of pinnules and an overlapping number of pinnules in the outermost row, but differ in the presence of sclerites, with X. hicksoni having only a few or none (see also Reinicke 1997). The current study has shown that X. umbellata, too, may occasionally have a low abundance of sclerites. Two colonies collected in Eilat and identified as X. hicksoni (McFadden et al., 2011: ZMTAU CO 34072, 34073) share identical sequences with the Xenia umbellata examined during this study (Fig. 23). Both were re-examined here, and the former was found to have sclerites only in the colony base, while the latter lacks sclerites entirely. Colonies collected in Eilat during the current study and identified as X. hicksoni unfortunately could not be sequenced. Two of them lack sclerites in all parts of the colony (ZMTAU CO 36874 and 36892), and one has sclerites only in the colony base (ZMTAU CO 36853). Therefore, based on Red Sea material, X. hicksoni and X. umbellata might be considered synonyms. However, X. hicksoni from its type locality (Indonesia) might still represent a valid and different species, and should be compared genetically and morphologically with the Red Sea material.
Distribution. Red Sea, Japan, Philippines, Indonesia, Papua New Guinea: New Britain, Great Barrier Reef (Australia), Zanzibar and Madagascar.
description: Published as part of Halász, Anna, Mcfadden, Catherine S., Toonen, Robert & Benayahu, Yehuda, 2019, Re-description of type material of Xenia Lamarck, 1816 (Octocorallia: Xeniidae), pp. 201-239 in Zootaxa 4652 (2) on pages 227-234, DOI: 10.11646/zootaxa.4652.2.1, http://zenodo.org/record/3363653