Umimayanthus discolor, Montenegro & Fromont & Richards & Kise & Gomez & Hoeksema & Reimer, 2024

Umimayanthus discolor sp. nov.

Montenegro, Kise & Reimer urn:lsid:zoobank.org:act:7A022F55-32F9-49FA-A395-081BA7240FF3

Synonymy. This specimen was mis- identified as Parazoanthus lividum , specimen F 67954 in the collection of Museum Victoria.

CONTRIBUTIONS TO ZOOLOGY 93 (2024) 466–522

Etymology. The specific epithet “discolor ” means multiple colors in Latin. This is in reference to U. discolor sp. nov. forming colonies of polyps with contrasting colorations between the oral disk and the column, stolon, and coenenchyma.

Material examined. Type locality: Albany [loc. 3], − 35.093889 °S, 117.963889 °E. Holotype: WAM Z88616 About WAM (− 35.093889 °S, 117.963889 °E, loc. 3, Murray Road boat ramp, Albany , Western Australia, 6.4 m depth, April 10, 2018 by O.A. Gomez). Paratype: WAM Z88626 About WAM (− 35.049722 °S, 117.693611 °E, loc. 4, Shelter Is., Albany, Western Australia, 8.5 m depth, April 11, 2018 by O.A. Gomez) GoogleMaps .

Other material (n =3). Other examined specimens belong to the Museum of Natural History and Museums Victoria; NHMUK-1887.5 .21.1865 (precise location unknown, southwestern part of Western Australia), NHMUK-1931.8 .4.57 (− 6.164028 °S, 134.944667 °E, loc. 24, east coast of Aru Is., Maluku, Indonesia, 4–15 m depth), MV-F67954 (− 39.016306 °S, 146.442917 °E, loc. 1, South Wall , Sealer Cove, Wilsons Promontory, Victoria, Australia, 10 m depth, April 16, 1987 by Dept. Conservation of Environment ) GoogleMaps .

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Diagnosis. U. discolor sp. nov. can be distinguished from other species in the genus Umimayanthus by combining the growing pattern and coloration of colonies. U. discolor has polyps connected in chains following a branching pattern, but branches are not connected to each other. Different from all other species of Umimayanthus in the Indo-Pacific Ocean, U. discolor sp. nov. has a disruptive coloration pattern when observed in-vivo, with polyps having a dark brown oral disk clearly contrasting against the white-coloured column, stolon, and coenenchyma ( fig. 14B–D). Currently known to establish associations with sponges in the genera Trikentrion Ehlers, 1870 and Clathria Schmidt, 1862 ; known host species are Trikentrion flabelliforme and Clathria (Thalysias) cactiformis (Lamarck, 1814) .

Additionally, multiple unique substitutions across the ITS-rDNA, 16S-rDNA and COI-mtDNA markers clearly differentiate this species from all other members of genus Umimayanthus in the concatenated alignment, as follows: in the ITS-rDNA there is a “A” in position 9 bp, “TCA” between 42 bp to 44 bp, “T” at 74 bp, 344 bp and 665 bp, “G” at 87 bp, 430 bp, 652 bp, 710 bp, and unique deletions at 51 bp and 455 bp; remarkably substitutions were found in the 16S-rDNA region, “T” at position 1337bp, and COI-rDNA region, “T” at position 1654bp. As well, a unique combination of substitutions and deletions/gabs is present between 132–339 bp in the ITS-rDNA region ( fig. 15).

Description. Size. Preserved polyps were on average 2.1 mm ± 0.26 mm (σ2 = 0.07, max. 2.39 mm, n = 9 polyps) in diameter, and 0.97 mm ± 0.46 mm (σ2 = 0.21, max. 1.58 mm, n = 8 polyps) in height. All measurements were performed on voucher specimens preserved in ethanol: zoantharian specimen vouchers WAM Z88616, WAM Z88626, and MV-F67954.

Morphology. The holotype specimen is associated with Clathria (Thalysias) cactiformis (Lamarck, 1814) . Colonies formed by polyps tightly connected by stolonifer- ous chains in a branching pattern extending over the surface of the host sponge. Polyp chains branch continuously with branches interconnected. The coenenchyma is clearly visible over the sponge surface and connects multiple polyps by the stolon. Polyps preserved in ethanol are white or cream in color. Capitulary ridges were not visible. Tentacles were approximately up to 22–24 in number. Capitulum and scapus were moderately encrusted by small sand particles.

Cnidae. The diversity of cnidae was relatively low across tissues. Spirocysts, bastrichs and microbasic b-mastigophores were numerous in the tentacles and pharynx. Additionally, holotrichs (L) were found in the pharynx. Mesenterial filaments were populated by numerous microbasic p-mastigophores, while cnidae were rare in the column with only holotrichs (L) found. See table 5 and fig. 16.

Internal morphology. Sphincter muscle was located in the endoderm. Mesenterial arrangement was macrocnemic. Mesenteries were approximately up to 22–24 in number.

Distribution. Analysed specimens were collected from Australia and Indonesia. In Australia, specimens were from Albany [loc. 3, 4] and Wilson’s Promontory [loc. 1], and in Indonesia from the Aru Islands

CONTRIBUTIONS TO ZOOLOGY 93 (2024) 466–522

CONTRIBUTIONS TO ZOOLOGY 93 (2024) 466–522

CONTRIBUTIONS TO ZOOLOGY 93 (2024) 466–522

[loc. 24] ( fig. 1). Specimens were found at depths of 4–15 m.

Associated host. Umimayanthus discolor sp. nov. was found to be associated with two sponge species; Clathria (Thalysias) cactiformis , family Microcionidae Carter, 1875 , and Trikentrion flabelliforme , family Raspailiidae .

As with Umimayanthus cf. aruensis , only historic specimens (collected in 1887 and 1931) of Trikentrion flabelliforme were shown to host Umimayanthus discolor sp. nov., and all more recently collected specimens of this sponge species available to us instead hosted Umimayanthus cf. aruensis .

Clathria (Thalysias) cactiformis is in a different sponge family ( Microcionidae ) from Trikentrion flabelliforme ( Raspailiidae ). The other Umimayanthus species described in this study are specific to the same host family, often to the same genus, and in one instance to a single species. Thus, Umimayanthus discolor sp. nov. is a more ‘host-generalist’ species, and the exception among these newly described Umimayanthus species.

Remarks. Molecular data and the arrangement of polyps in specimens BMNH-1887.5.21.1865 and BMNH-1931.8. 4.57 led us to identify these specimens as Umimayanthus discolor sp. nov., and further morphological analyses will be help- ful to confirm this decision.

Specimen MV-F67954 was initially identified as P. lividum , however based on the general morphology of the colony, with polyps arranged in branching chains, and the association with Clathria (Thalysias) cf. cactiformis , we have amended the identification of this specimen to Umimayanthus discolor sp. nov.

U. discolor sp. nov. has polyp diameter sizes similar to those reported for U. chanpuru , U. miyabi , and U. nakama , all from southern Japan. In contrast to these species, U. discolor sp. nov. has a well- developed coenenchyma firmly connecting polyps in chains in a branching pattern. These branches remain unlinked and do not form a reticulate pattern over the surface of the host sponge, unlike as in U. cf. aruensis , and do not form a mat as in Parazoanthus lividum .