Acropora tenuissima Bonito, Bridge, Fenner & Baird 2024, n. sp.
Creators: name: Bridge, Tom C. L.
name: Cowman, Peter F.
name: Quaưrini, Andrea M.
name: Bonito, Victor E.
name: Frederic
name: Harii
name: Head, Catherine E. I.
name: Hung, Julia Y.
name: Halafihi, Tuikolongahau
name: Rongo, Teina
name: Baird, Andrew H.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Scleractinia
Acroporidae
Acropora
Acropora tenuissima

description: Acropora tenuissima Bonito, Bridge, Fenner & Baird, n. sp.
Zoobank registration: urn: lsid: zoobank.org:act: 43573A79- 8333-4FBE-8C78-20E8837CAA10
Holotype: G78705 * collected from 7 m depth on the eastern fore-reef of Myrmidon Reef * GBR* Australia (Fig. 5A * B).
Paratypes: G78343 * 7 m depth * fore-reef of Namaqumaqua * Viti Levu * Fiji (Fig. 5C); and G81179 * collected from 1 m depth at Blue Pools * Heron Island * GBR* Australia.
Other material examined: MTQ: GBR G30675* Davies Reef* Queensland * Australia; G30677* Fitzroy Reef* Queensland * Australia.
Holotype: Colony shape corymbose with determinate growth form. Primary branches long (> 10 cm)* thin and terete* 3–5 mm in diameter and vertically orientated (Fig. 5D * E). Axial corallites tubular* 1.2–2.0 mm outer diameter and 0.8– 1.0 mm inner diameter (Fig. 5F). Radial corallites closely positioned but not touching* predominantly appressed tubular with extended lower lip and large oblique or nariform openings* but become labellate towards branch tips. Septa on both axial and radial corallites are weakly developed; primary septa up to one-quarter of the radius of the calyx* secondary septa absent or some present as points (Fig. 5F * G). The coenosteum is costate* with some spinule development in the paratype specimen (Fig. 5H).
Molecular phylogeny: The two specimens sequenced of this species* from the GBR and Fiji * are recovered as a reciprocally monophyletic group in all phylogenetic trees (Figs 2 * 3; Supporting Information* Figs S1* S2). The species is sister to A. aff. pagoensis in the ML reconstructions* but the SNAPP species tree places A. aff. pagoensis as sister species to A. rongoi (Fig. 3D).
Remarks: Forms small corymbose clumps* generally 15–30 cm in diameter. Colonies are compact cushions with short branches in high-energy environments. In more sheltered habitats* colonies can form taller* more upright corymbose colonies. Generally* an iridescent yellow–orange to pinkish/orange colour* especially pronounced at the branch tips and axials* but can also be greyish/brown in colour. Polyps lower on the branches are generally extended during the day and brownish in colour. The species is clearly differentiated morphologically from all other species in clade I-C by its thin* neat branches. Within cluster 1i* A. aff. pagoensis has much thicker branches* whereas A. rongoi has thick branches and an indeterminate growth form. Acropora tenuis and Acropora azurea Veron & Wallace * 1984 can co-occur with A. tenuissima and can have similar colony shape* but A. tenuissima is distinguished from A. tenuis by its thinner branches and smaller corallites* whereas A. azurea has appressed radial corallites that are nariform rather than tubular. Specimens of A. tenuissima in the MTQ collection are identified as Acropora nana (Studer* 1878); however* the holotype of A. nana (MNB 1941) has tubular to nariform radial corallites* which extend from the branch at an obtuse angle* rather than the acute to appressed angle of A. tenuissima. The coenosteum of the A. nana holotype also exhibits a heavily ornamented coenosteum* whereas the coenosteum of A. tenuissima is costate and lacks spinules. A specimen of A. tenuissima from Fiji is included in the series of images illustrating A. subulata by Veron et al. (2016) http://www. coralsossheworld.org/media/images/0073_C04_01.jpg; however* the holotype of A. subulata is a fragement of a large tabular or corymbose colony with tightly packed* labellate radial corallites reminiscent of Acropora squamosa (Brook* 1892) but very distinct from A. tenuissima.
Distribution: Currently recorded only from Fiji and the centralsouthern GBR* but likely to occur elsewhere in the south-west Pacific (Supporting Information* Fig. S6).
Etymology: Meaning ‘very thin’ in Latin * tenuissima refers to the thin branches characteristic of this species and which distinguish it from A. tenuis and A. kenti * both of which co-occur with A. tenuissima across its range.
description: Published as part of Bridge, Tom C. L., Cowman, Peter F., Quaưrini, Andrea M., Bonito, Victor E., Frederic, Harii, Head, Catherine E. I., Hung, Julia Y., Halafihi, Tuikolongahau, Rongo, Teina & Baird, Andrew H., 2024, A tenuis relationship: traditional taxonomy obscures systematics and biogeography of the ' Acropora tenuis' (ºcleractinia: Acroporidae) species complex, pp. 1-24 in Zoological Journal of the Linnean Society 202 (1) on pages 14-16, DOI: 10.1093/zoolinnean/zlad062, http://zenodo.org/record/14443904