Blastopathes Horowitz, 2020

Horowitz, Jeremy, Brugler, Mercer R., Bridge, Tom C. L. & Cowman, Peter F., 2020, Morphological and molecular description of a new genus and species of black coral (Cnidaria: Anthozoa: Hexacorallia: Antipatharia: Antipathidae: Blastopathes) from Papua New Guinea, Zootaxa 4821 (3), pp. 553-569 : 557-567

Blastopathes Horowitz gen. nov.

( Figures 2–8 ; Tables 1–2)

Diagnosis. Corallum sparsely branched to the third and sometimes fourth order, not pinnulate. Branches long (up to 1.3 m) and spaced far apart (distances between first order branches and second order branches range from 210 cm to 560 cm) and occurring singly or in verticil-like clusters of varying numbers (as many as 10). Stem and branches thick (up to 6 mm diameter) and rigid. Each branch extending out at their base perpendicular to the stem and lower order branches from which they arise, and then curving upward with distal ends being straight or curved. One branch can extend directly upwards from the center of the cluster. Spines triangular or conical, laterally compressed, smooth, up to 0.34 mm tall. Polyps, ~ 1.25 mm in transverse diameter, ~6 polyps per cm in one row. Sagittal tentacles (~ 8 mm in length, extended) are more than twice the length of lateral tentacles (~ 3 mm in length, extended).

Remarks. Blastopathes morphologically resembles Allopathes Opresko & Cairns, 1994 , which also has stemlike branches coming from a singular location on the corallum ( Opresko & Cairns 1994). However; Blastopathes differs from Allopathes by having branch clusters that do not necessarily occur near the base of the stem and in having more than one branch cluster ( Figures 2 A–2B). Additionally, the abpolypar spines of Blastopathes are triangular, smooth, and distally slanted while all spines of Allopathes are conical with conical tubercles near the apex ( Figures 2 C–2D). Other genera that contain sparse and elongate branches are Pteropathes Brook, 1889 , Hillopathes van Pesch, 1910 , and in the genus Antipathes , Antipathes dichotoma Palla, 1766 ; however, none contain branch clusters. Lastly, Blastopathes contains a stiff and non-pinnulate stem and branches that resemble unbranched genera Pseudocirrhipathes Bo et al., 2009 , Cirrhipathes de Blainville, 1830 , and Stichopathes Brook, 1889 , all of which differ from Blastopathes by lacking branches.

Molecular results. The mitochondrial igrN sequences for specimens NMAG 1893 and NMAG 1895 consisted of 482 base pairs. The two specimens shared identical sequences across 465 comparable bases. The complete igrN alignment consisted of 47 sequences, 682 bp, and included species from all seven black coral families. In the 682 bp alignment there were 274 parismony informative site (40%). Targeted capture data for 33 specimens that spanned six of the seven families in the Antipatharia , resulted in a total number of raw reads ranging from 44,898 to 3,603,888. One sample (10 raw reads, C705) was removed due to sequencing failure. Quality control and adapter trimming resulting in a mean of 1,606,997 ± 1,640,018 SD trimmed reads per sample. Trimmed reads were assembled into a mean of 927 ± 154 SD contigs per sample. The total number of matched UCE/exon loci was 2,309 with an average base pair length of 752 (ranging from 83 to 18,423 base pairs). The 75% taxon occupancy matrix included 286 loci that were concatenated into an alignment with a total length of 111,929 base pairs. A total of 36,052 parismony informative (PI) sites were identified (32% of total sites), with an average of 126.06 PI sites per locus.Alignment were also constructed for the for the holotype specimen (MTQ G74904) and the two paratype specimens (NMAG 1893 and NMAG 1895). The total number of matched loci across the three samples was 1,290 with an average base pair length of 623 (ranging from 189 to 4,068 bp). A complete (all three samples present in each loci) concatenated matrix included 792 loci, with a total alignment length of 499,264 base pairs. There were 3,855 variable sites (~0.7% of total sites) among the three samples.

Despite the difference in species-level sampling, the maximum likelihood phylogenies displayed similar topologies for both alignment types (igrN, UCE/exon). In both cases, the new genus formed a distinct clade within the family Antipathidae and members of the genera Cirrhipathes and Antipathes formed separate monophyletic groups ( Figures 3 A–3B). Differences between the two trees include the UCE/exon tree suggesting that Arachnopathes Milne Edwards H., 1857 , and Stichopathes also share a common ancestor with Blastopathes , while in the igrN tree Stichopathes is more closely related to another lineage containing members of the Aphanipathidae Opresko, 2004 , than to Blastopathes .

Etymology. From the Greek “blastos”, germ, sprout, or shoot, in reference to the branch cluster features, and the commonly used suffix “pathes”. From the Latin “Medusa” in reference to thick and upward curving branches, like the snakes on the mythical gorgon’s head.

Type material. Holotype, MTQ G74904, Papua New Guinea, Bismarck Sea, West New Britain Province, Kimbe Bay, Vanessa’s Reef , 35m depth, 13 March 2019 ( SEM stubs MTQ G74906 to MTQ G74910, schizo- holotype NMAG 1892 ) . Paratypes, NMAG 1893 , Papua New Guinea, Bismarck Sea, West New Britain Province, Kimbe Bay, Christine’s Reef , 30m depth, 13 March 2019; MTQ G74911, Papua New Guinea, N Bismarck Sea, West New Britain Province, Kimbe Bay , Lady Di, 37m depth, 15 March 2019 ( SEM stub MTQ G74912); MTQ G74913, Papua New Guinea, Bismarck Sea, West New Britain Province, Kimbe Bay Restrf Island , 30m depth, 16 March 2019 ( SEM stub MTQ G74915) ; NMAG 1895 , Papua New Guinea, Bismarck Sea, West New Britain Province, Kimbe Bay, Christine Reef , 30m depth, 16 March 2019 .

Type locality. Kimbe Bay, Papua New Guinea. Latitude: -5.305; Longitude: 150.124

Description. The holotype is a 1.2 m tall specimen that branches to the third order ( Figure 4 ). The stem is 0.6 m in length, 6.3 mm in diameter near the base, and 4 mm in diameter just below the first branch cluster. First branch cluster occurs at the apex of the stem and consists of 10 elongate branches extending in different directions ( Figure 5A ) of varying lengths (maximum length 1.3 m) and diameters (none thicker than the stem). One first order branch is 0.6 m in length, 4 mm in diameter near the base, and 2 mm in diameter just below a second order branch cluster consisting of ~10 branches ( Figure 5B ), with a maximum branch length of 50 cm. Another first order branch is 1.3 m in length, 3 mm in diameter near the base, and 0.5 mm at the branch tip and does not produce a branch cluster. Another first order branch extends from the center of the branch cluster and extends 0.9 m directly upwards with a branch thickness of 4 mm near the base and 2 mm just below a second order branch cluster consisting of four branches with a maximum branch length of 65 cm. Another first order branch extends 5 cm, is 2 mm in diameter near the base and increases to 2.5 mm just below what resembles a new branch cluster consisting of three branches of different lengths and thicknesses. The longest of the three branches coming from the 5 cm branch is 0.6 m in length, 1.5 mm in diameter near the base, and 0.5 mm diameter near the tip. The second longest branch is 0.42 m in length, 0.2 mm in diameter near the base, and 0.1 mm near the tip. The shortest of the three branches is 5 cm in length, 0.8 mm in diameter near the base, and <0.1 mm near the tip. Branchlets are found on all branch clusters ( Figure 5B ) and locations on branches that seem to be newly forming branch clusters ( Figure 5C ) ranging from 1 cm to 8 cm in length, with ~ 0.5 mm diameters at their bases and <0.5 mm diameters at branch tips.

The spines ( Figures 6 A–6C) on the branches and stem are smooth and laterally compressed. Polypar spines are 0.2 mm– 0.34 mm tall, are conical at right angles to branch axes with rounded apexes, and spines are spaced ~ 0.45 mm in one row ( Figure 6A ). Abpolypar spines are 0.12 mm– 0.24 mm tall and are triangular with distally slanted proximal edges and perpendicular or proximally slanted distal edges, and spines are spaced ~ 0.38 mm in one row ( Figure 6B ). Seven to eight, sometimes offset rows of spines can be counted in one view of a branch and stem, and approximately three spines can be counted in 1 mm of a spine row on a branch ( Figure 6C ) and stem.

The polyps ( Figures 7 A–7B), olive in color when alive, are arranged in a single row on thin branches ( Figure 7A ), and in multiple rows on the stem and thick branches ( Figure 5A ). In-situ measurements reveal that lateral tentacles (~ 3 mm in length, extended) are less than half the length of sagittal tentacles (~ 8 mm in length, extended) ( Figure 7A ). Polyps range 0.5 mm– 1.38 mm in transverse diameter and are spaced ~ 1 mm apart, resulting in approximately five polyps per 1 cm in one row ( Figure 7B ). The sizes of contracted and extended polyps are quite variable.

The paratypes ( Figures 8 A–8E) range from 0.4 m to 0.5 m in height. The stem lengths range from 3 to 10 cm in length from basal plate to the first branch cluster. All paratypes have branch clusters ( Figures 8 A–8C), 7 to 8 rows of compressed spines, tall and conical polypar spines, and triangular distally slanted abpolypar spines ( Figure 8D ), with polypar spine heights ranging from 0.14 mm to 0.3 mm and abpolypar spines ranging from 0.1 mm to 0.2 mm. About five polyps per 1 cm with lateral tentacles less than half the length of sagittal tentacles, with varying polyp sizes like the holotype ( Figure 8E ).

Figures

FIGURE 2. Comparison A–B, branching characteristics of Allopathes denhartogi and Blastopathes medusa (A from A. denhartogi holotype RMNH Coel. 31293, B from B. medusa holotype MTQ G74904); comparison C–D, spine characteristics of A. denhartogi and A. medusa (C from A. denhartogi schizoholotype USNM 1014577, D from B. medusa holotype MTQ G74904)

FIGURE 3. Maximum likelihood-based phylogenetic reconstructions: A, using igrN sequence data; B, using UCE and exonic sequence data.

FIGURE 4. Blastopathes medusa holotype (MTQ G74904): Lateral view of corallum.

FIGURE 5. Blastopathes medusa holotype (MTQ G74904): A, branch cluster on stem; B, branch cluster on branch; C, branchlet on branch.

FIGURE 6. Blastopathes medusa holotype (MTQ G74906): A, polypar spines on terminal branch; B, abpolypar spines on terminal branch; C, section of terminal branch.

FIGURE 7. Blastopathes medusa holotype (MTQ G74904): A, single row of polyps on multiple terminal branches; B, interpolypar space on terminal branch.

FIGURE 8. Blastopathes medusa paratypes: A–C, in-situ images of colonies showing branch clusters (A from paratype MTQ G74911; B from paratype NMAG 1893; C from paratype MTQ G74913); D, paratype (MTQ G74912): section of terminal branch showing eight rows of compressed spines; E, paratype (NMAG 1893): section of branch showing polyp density and tentacle lengths.