Massinium keesingi O’Loughlin, 2014

P. Mark O’Loughlin, Melanie Mackenzie & Didier Vandenspiegel, 2014, New dendrochirotid sea cucumbers from northern Australia (Echinodermata: Holothuroidea: Dendrochirotida), Memoirs of Museum Victoria 72, pp. 5-23 : 13-15

Massinium keesingi O’Loughlin sp. nov.

Zoobank LSID. http://zoobank.org:act:BDDF31E0-C687-4932-

9541-A2C40266126C

Figures 7 , 8 , key.

Material examined. Holotype. NW Australia, Joseph Bonaparte Gulf , Kimberley region, off King George River, 13.85°S 127.29°E, RV Solander, large epibenthic sled, 45 m, J. Keesing, 6 Jun 2013, NMV F203008 (KGR lot 23324; UF tissue lot MOLAF1458 ).

Description. Form sub-spherical, 40 mm long (preserved), mouth anterior dorsal, anus posterior dorsal, slightly developed oral and anal cones (preserved); firm leathery body wall; tube feet scattered over body, withdrawn, sparse dorsally, more numerous ventrally, diameters about 0.2 mm; 20 dendritic tentacles, 5 pairs large in an outer ring, 5 pairs very small in an inner ring (proximal circum-oral); calcareous ring long, tubular, composite; radial plates blunt anteriorly with 2 lateral small notches and deeper central notch, most of radial plates with long median un-calcified section; inter-radial plates pointed anteriorly, small oval un-calcified section posteriorly; 1 polian vesicle; gonad tubules long, branched; respiratory trees extending the length of the coelom.

Ossicles in mid-body wall tables only, sparse, scattered, tables abundant in oral disc and peri-anally; table discs oval to round, variable sizes, up to 90 µ m long, margin smooth or slightly undulating, not spinous, 4 large central perforations, variable number of smaller outer perforations, some very small; spires rare or reduced, if present 1 or 2 pillars, spires up to half disc length long, few short spines apically. Oral disc with rods as in tentacles and abundant tables with multiperforate discs and predominantly single pillar spires, discs oval to sub-rectangular, 4 large central perforations, numerous smaller outer perforations, discs up to 96 µ m long, spires with 1 or 2 pillars, few short apical spines, length about half disc length. Tube feet with endplates, diameters about 150 µ m, lacking support ossicles. Tentacles with rod ossicles only, up to 90 µ m long, smooth, ends widened with few perforations and denticulate margin. Rosette ossicles not observed in tentacles or oral disc or body wall.

Colour preserved off-white; tube feet pale brown.

Distribution. NW Australia, Joseph Bonaparte Gulf, Kimberley region, off King George River, 45 m.

Etymology. Named keesingi for John Keesing (CSIRO), the leader of the King George River Expedition, with appreciation of John’s gracious and helpful collaboration in our work with the sea cucumber collection.

Remarks. A distinctive character of Massinium keesingi O’Loughlin sp. nov. is the frequent presence of table spires with a single pillar. We observed the five pairs of small tentacles to be in an inner ring. Massinium keesingi sp. nov. is distinguished from other species in the genus by the combination of morphological characters as detailed in the key.

Figures

Figure 7. Holotype specimen of Massinium keesingi O’Loughlin sp. nov. (NMV F203008). A, dorsal view of preserved holotype (40 mm long); B, ventral view of preserved holotype; C, sketch of dorso-lateral view of the holotype; insert with sketch of the calcareous ring; D, photo of the calcareous ring of the holotype.

Figure 8. SEM images of ossicles from the holotype of Massinium keesingi O’Loughlin sp. nov. (NMV F203008). A, peri-anal body wall tables and endplate fragment, discs with smooth margins, spires with 1 or 2 pillars (scale bars 10 µm); B, oral disc tables, table discs with smooth margin, spires with single or 2 partly fused pillars, apical spines short and blunt (scale bars 10 µm); C, tentacle rods (scale bars 10 µm).