Caementabunda simplex (Thomson & Dean, 1931)

Benayahu, Yehuda, Ofwegen, Leen P. van & McFadden, Catherine S., 2018, Evaluating the genus Cespitularia MilneEdwards & Haime, 1850 with descriptions of new genera of the family Xeniidae (Octocorallia, Alcyonacea), ZooKeys 754, pp. 63-101 : 83-89

Caementabunda simplex (Thomson & Dean, 1931) Figures 5 C–D, 29, 30, 31, 32, 33, 34, 35, 36, 37

Cespitularia simplex Thomson & Dean, 1931: 33-34; Macfadyen 1936:27; Verseveldt 1971: 62; Janes 2008: 606-608; Janes 2013: 198 (listed only); McFadden et al. 2014: 249 (listed only), Cespitularia turgida Verseveldt, 1971: 61-62.

Material.

Syntype: INDONESIA: ZMA 2344, Siboga Exped., Sta. 40, 12 m depth, Kawassang. Other material: SEYCHELLES: RMNH Coel 38673, Southern coast of Aride I. (04°13'S; 55°40'E), <20 m depth, 18 December 1992; MADAGASCAR: RMNH Coel 6697, Nosy Be, west of Andilina, 24 August, 1967, 20 m depth; RMNH Coel 42168, Stn. 22, 21 December 1999; RMNH Coel 42169; PHILIPPINES: Cebu Strait Exped., Sta. CEB. 1, Cebu Strait, Olango Channel, east side of Olango Is., USNM 60493, Sulu Archipelago, 6°07'N, 121°00'E, R/V Albatross; AUSTRALIA: USNM 60794, Flinders Reef, Great Barrier Reef, November 1981; BMNH 1934.3.28.8, Great Barrier Reef Exped., Sta. 10, dredge, 22 February 1929; 1982.11.17, Great Barrier Reef, Flinders Reef, South Coral Sea, southern outer slope, 10-15 m depth, coll. Z. Dinesen; BMNH 1982.11.18, similar details; JAPAN: ZMTAU Co 31642, off Danno, Yonaguni Is., Ryukyu Archipelago, 24°27'N, 122°57'E, 15 m depth, coll. Y. Benayahu, 13 November 1992; ZMTAU Co 31638, Mao Cave, Shimoji Is., Ryukyu Archipelago, 10 m depth, coll. Y. Benayahu, 19 November 1992; ZMTAU Co 35120, Umabanazaki Point, Yonaguni Is., Ryukyu Archipelago, 8-12 m depth, coll. Y. Benayahu, 3 June 2010; MADAGASCAR: ZMTAU Co 36057, three specimens; ZMTAU Co 36076, 4 Frères, 13°00.142'S, 48°29.099'E, 6-14 m depth, coll. Y. Benayahu, 2 December 2012; ZMTAU Co 36065, 4 Frères, 12°59.655'S, 48°29.248'E, 4-15 m depth, coll. Y. Benayahu, 1 December 2012, four specimens; ZMTAU Co 36115, Ronald Point, Nosy Be, 13°23.530'S, 48°00.143'E, 19-27 m depth, coll. Y. Benayahu, 3 December 2012; ZMTAU Co 36122, Ronald Point, Nosy Be, 13°29.032'S, 47°58.721'E, 2-4 m depth, coll. Y. Benayahu, 03 December 2012, two specimens; ZMTAU Co 36127, details as before; TAIWAN: Co 33021, Chaikou, Green Is., Taiwan, 22°40'40"N, 121°28'20"E, 3-6 m depth, coll. Y. Benayahu, 13 July 2005; ZMTAU Co 35715, Shihlang, Green Is., 22°39.425'N, 121°28.399'E, 8-12 m depth, coll. Y. Benayahu, 3 September 2012; ZMTAU Co 33022, Lomenyen, Green Is., 22°40'56"N, 121°30'06"E, 3-25 m depth, coll. Y. Benayahu, 12 July 2005; ZMTAU Co 35713, details as before, three specimens; ZMTAU Co 35701, details as before, four specimens; ZMTAU Co 35757, Shihlang, Green Is., 22°39.425'N, 121°28.399'E, 7-10 m depth, coll. Y. Benayahu, 5 September 2012, four specimens.

Description.

The syntype RMNH Coel 2344 consists of three encrusting lobed colonies attached to calcareous fragments. The largest syntype is 3 cm high by 5 cm wide, the second 1.5 by 2.5 cm, and the third 2 by 3.5 cm (Figure 29). The finger-like lobes feature non-retractile polyps, some of which are found on the colony base. The polyp body is up to 2.8 mm long and the tentacles are up to 1.0 mm long. The tentacles bear one row of 12-14 pinnules along each of their margins. The short pinnules are closely set, with no space between adjacent ones. The preserved colonies are brown-beige. Sclerites are highly abundant and found in all parts of the colony. Under the light microscope they are ovoid or pear-shaped as fully confirmed by SEM (Figure 30A), measuring up to 0.022 mm in length. Occasionally they are arranged in groups (Figure 30B), but during preparation they tend to dissociate and become sin gles. SEM revealed the unique microstructure of the sclerites, which comprise densely packed chip-like microscleres (Figure 30C), giving the sclerite surface the appearance of cement-chip aggregates (Figure 30D).

Color.

Live colonies are brown with yellow polyps (Figures 5 C–D).

Remarks.

The original description of the type by Thomson & Dean (1931: 34) is in agreement with the current findings, and indicates 10-12 pinnules compared to 12-14 noted by us. The sclerite size of 0.01 mm as given in the original description is incorrect and was later corrected by Verseveldt (1971). The latter study provides a better description of the sclerites as oblong, pear-like or angular in shape, 0.015-0.021 mm in diameter. The light microscopy used in the past clearly could not have revealed the unique surface microstructure of that species (Figure 30D).

Examination of the type of Cespitularia turgida Verseveldt, 1971 (RMNH Coel 6607) revealed Caementabunda -type sclerites (Figure 31). In the original description Verseveldt (1971: 62) presented a comparison between the type of C. simplex and his new species and noted the number of pinnules in the single row of both species being 10-12 in the latter vs. 5-6 in the former. The current examination of the type of C. turgida has confirmed the original morphological findings, while we also present here for the first time images of its sclerites.

Dr. Zena Dinesen (Department of Agriculture, Fisheries and Forestry, Queensland) provided us with an unpublished taxonomic manuscript dealing with some Xeniidae of Flinders Reefs, Great Barrier Reef. Under the collection numbers BMNH 1982.11.17 and 1982.11.18 there are colonies labeled as paratypes of Efflatounaria flindensis Dinesen. Recently Dr. Dinesen confirmed that these two colonies are provisional paratypes of unpublished species presented in her manuscript. Our examination of the colonies revealed Caementabunda -type sclerites (BMNH 1982.11.17: figure 32, 1982.11.17: figure 33). In addition, it confirmed the unpublished morphological description of the material which states that the pinnules: "Mostly very contracted, difficult to measure, in one row on each side of the tentacle with 5-12 (6-9) pinnules per row". Hence, the pinnule number corresponds to the original types of both C. simplex and of C. turgida . Similarly, examination of ZMTAU Co 35757 from Taiwan revealed Caementabunda -type sclerites (Figure 34) and 10-12 pinnules in a row, and ZMTAU Co 36127 and Co 36122 from Madagascar both had Caementabunda -type sclerites (Co 36122: figure 35) and 7-11 pinnules, thus falling within the range stated above. Based on these findings, it is concluded here that pinnule count is not diagnostic for species delineation in the newly-described genus Caementabunda . Similarly, it is concluded that Cespitularia turgida is a junior synonym of Caementabunda simplex and thus that both should be accommodated within this new genus.

Other material.

All other material (see above) features the same sclerites described above for the syntype (Figure 30). Macfadyen (1936: 27) described in a colony from the Great Barrier Reef Expedition numerous minute discs about 0.010 mm in diameter, finely sculptured. The current examination of that colony (BMNH 1934.3.28.8) revealed Caementabunda -type sclerites. Likewise, RMNH Coel 38673 from Seychelles (see Janes 2008) and ZMTAU Co 31642 (Figure 36) feature this type of sclerite, as do USNM 60793 and 60794 collected in the Philippines (USNM 60793: Figure 37). Based on the current findings all of these colonies were assigned to the new genus.

Distribution.

Green Island, Taiwan; Philippines; Great Barrier Reef; Sulawesi; Madagascar; Seychelles.

Molecular phylogenetic results.

Sequences of mtMutS (582 bp), igr1+COI (767 bp) and 28S rDNA (755 bp) were obtained from 46 individuals of Conglomeratusclera and nine individuals of Caementabunda from three different geographical locations: Madagascar; Green Is., Taiwan; Yonaguni Is., Japan (GenBank accession nos. MH071812-MH071969). All phylogenetic analyses of individual gene regions as well as the concatenated alignment (2104 bp) recovered trees in which specimens of Conglomeratusclera and Caementabunda formed two separate, well-supported clades (Figure 6). The average pairwise genetic distance (K2p) among individuals belonging to the two different clades was 3.6%, a value comparable to or higher than that observed among most other genera of xeniids (Figure 6).

All individuals of Conglomeratusclera shared identical sequences at mtMutS and COI, with just two exceptions: a single individual from Taiwan (ZMTAU Co35731) that differed by 0.2% at mtMutS; and one from Madagascar (ZMTAU Co36055) that differed by 0.4% at COI. Variation at the 28S rDNA locus ranged from 0-1.5%. Although a group of nine Conglomeratusclera colonies from Taiwan shared a 28S genotype that differed from all others by three nucleotide substitutions (0.4%), there was no significant bootstrap or a posteriori support for them as a separate clade, and no obvious morphological differences to suggest that they might represent a different species.

All Caementabunda specimens also shared identical mtMutS and COI sequences, with the exception of a single individual (ZMTAU Co 36076) that differed by 0.1% at COI. At 28S rDNA pairwise genetic distances (K2p) among individuals ranged from 0-0.8%, and a group of three specimens from Madagascar (ZMTAU Co 36065, Co 36076, Co 36122) differed from all others by three nucleotide substitutions. There was, however, no significant support for this clade, and no apparent morphological differences between these individuals and others of C. simplex .