Rhodolitica occulta, Breedy & Ofwegen & McFadden & Murillo-Cruz, 2021

Breedy, Odalisca, Ofwegen, Leen van, McFadden, Catherine S. & Murillo-Cruz, Catalina, 2021, Rhodolitica on rhodoliths: a new stoloniferan genus (Anthozoa, Octocorallia, Alcyonacea), ZooKeys 1032, pp. 63-77 : 63

Rhodolitica occulta sp. nov. Figures 2 , 3

Material examined.

Holotype. MZUCR 2514, lot 1, ethanol preserved, Cocos Island , Chatham Bay, 05°33.347'N, 87°02.336'W, dredging, 45 m depth, J. Cortés, J. Sibaja-Cordero, Proteus -CIMAR Expedition, R /V Proteus , 13 January 2007 . Paratypes. MZUCR 2514, lots 2, 3, ethanol preserved, same geographical data as the holotype. MZUCR 2734, lot ethanol preserved, Roca Chatham Bay , Langosta, Punta Ulloa, 05°33.222'N, 87°02.053'W, dredging 39-44 m depth, J. Cortés, J. Sibaja-Cordero, Proteus -CIMAR Expedition, R /V Proteus , 17 January 2007 . MZUCR 2513 ( GenBank accession numbers MW491885 (28S rDNA), MW491886 (mtMutS) and MW491887 (COI)), ethanol preserved, Chatham Bay, Punta Ulloa, 05°33.222'N, 87°02.063'W dredging 45 m depth, J. Sibaja-Cordero, 14 April 2008 . MZUCR 3301, ethanol preserved, Bahia Iglesias , Muela Rock, 23 m depth, J. Cortés, 14 January 2007 . MZUCR 3302, lot preserved in ethanol, Chatham Bay , 05°32'43.6"N, 87°01'41.7"W, 20 m depth, J. Cortés, 3 April 2009 . MZUCR 3303, lot ethanol preserved, off Cocos Island , Everest pinnacle, 55 m depth, HOV DeepSee Dive 2375, A. Klapfer, 25 October 2015 .

Type locality.

Chatham Bay, Cocos Island, Costa Rica, 45 m depth.

Description.

The holotype is composed of several bright red tubular, single anthosteles extending up to 8 mm above the surface of a 4 cm-diameter rhodolith (from one lot of five rhodoliths, 4-7 cm diameter) (Fig. 2A ). The tubular anthosteles are slightly expanded distally, forming groups of 10-12, and closely spaced, with the bases 1-2 mm apart. The anthosteles arise directly from thin basal stolons (Fig. 2B ). The stolons are ribbon-like, approximately 1 mm in width, and extending in irregular patterns on the surface of the rhodolith. Anthostelar walls are composed of bright red, variable coenenchymal sclerites: long warty spindles, 0.17-0.27 mm in length, 0.047-0.07 mm wide (Figs 2C , 3A ); complexly warted cylindrical spindles with fused tubercles on one surface, and warty on the other, 0.11-0.32 mm long and 0.045-0.08 mm wide (Fig. 3B ); bent spindles, 0.19-0.23 mm long, 0.01-0.013 mm wide (Fig. 3B , end of the row); smaller crosses, radiates up to 0.15 mm long, and transitional forms (Fig. 3C ) from the inner coenenchyme. Conspicuous fused or partly fused sclerites are present in the stolons (Figs 2C , 3F ); Figure 3F (right side) shows details of sclerites fused together. These brittle sclerites can partially dissociate during the dissolution process, forming small or large aggregations 0.2-1.6 mm long (Figs 2C , 3F ). They are present only in the stolons, and do not extend into the anthostelar walls. Anthocodiae are completely retractile into the anthosteles. The anthocodiae have eight interseptal points, composed of slender thorny spindles, 0.23-0.5 mm long and 0.018-0.05 mm wide (Figs 2C , 3D ) arranged 'en chevron’, with very few transverse spindles, not forming a collaret. The points are composed of 10-15 spindles. Orange biscuit-like rods, 0.047-0.095 mm long and 0.014-0.026 mm wide (Figs 2D , 3E ) are along the tentacles. Unfortunately, all specimens have been preserved with the anthocodiae partially or totally retracted therefore a full description is not possible.

Variability.

The paratypes were found on rhodoliths of 3-9 cm in diameter. Some variation in colour was found in a few paratypes. They present red and orange anthosteles in the same colony. All other characteristics were consistent with those of the holotype.

Habitat and distribution.

The colonies were found only associated with living rhodoliths, from 20 to 55 m depth. The rhodoliths were in aggregations, forming extensive beds or dispersed on sandy bottoms (Fig. 4 ). Specimens were also collected from a dead shell and from a dead piece of coral partially covered by rhodoliths, making it evident that this species is associated with living rhodoliths. In some colonies anthosteles are occupied by several epizoic organisms, especially bryozoans and small hydroids.

The species is presently only known from Cocos Island.

Etymology.

An adjective (L), occultus, meaning hidden, secret, mysterious. Historically, numerous expeditions to Cocos Island seeking pirate treasures buried somewhere in the mysterious island were completely unsuccessful. The new species, out of sight, hidden amongst rhodoliths, shows that the real treasure of the island is its biodiversity.

Figures

Figure 2. Rhodolitica occulta sp. nov. A holotype MZUCR 2514 B paratype MZUCR 2513, ribbon-like stolons can be observed at the upper cluster of polyps (white arrows) C unsorted sclerites of the holotype D tentacular sclerites.

Figure 3. Rhodolitica occulta sp. nov., holotype MZUCR 2514 A, B outer coenenchymal sclerites C inner coenenchymal sclerites D anthocodial sclerites E tentacular sclerites F fused and partially fused sclerites from stolons, details at the right.

Figure 4. Rhodoliths bed, Pajara Islet, Cocos Island, at 22 m in depth. Photograph by Beatriz Naranjo, UCR.