Chondrocladia (Chondrocladia) callistemonex, Ekins & Erpenbeck & Hooper, 2020

Ekins, Merrick, Erpenbeck, Dirk & Hooper, John N. A., 2020, Carnivorous sponges from the Australian Bathyal and Abyssal zones collected during the RV Investigator 2017 Expedition, Zootaxa 4774 (1), pp. 1-159 : 117-120

Chondrocladia (Chondrocladia) callistemonex sp. nov.

Figures 22 & 23 , Tables 10 & 13

urn:lsid:zoobank.org:act:DC70BE53-55B7-43BE-8014-906BAF215E43

Material Examined:

Holotype: QM G337494 , off Newcastle , New South Wales, Australia, Station 65, 33° 26’ 27.6”– 33° 26’ 6.0” S, 152° 42’ 7.2”– 152° 39’ 54.0” E, 4280– 4173 m, Beam Trawl, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03 , Sample 65-124, 30/v/2017.

Paratypes: QM G337493 same collection details as holotype, Sample 65-122 ; QM G337485 same collection details as holotype, Sample 65-122.1 .

Etymology: Named for the resemblance of this sponge to the flowers of the ‘bottlebrush’ ( Callistemon spp .) trees.

Distribution: This species is presently known only from type locality off Newcastle, Australia, at abyssal depth.

Description:

Growth form: Erect stipitate unbranched sponge with numerous horizontal filaments at right angles to the stem ( Figure 22 I ). These filaments form four to seven columns encircling the stem. The holotype is 80 mm in length, including the 10 mm of unbranched root-like appendages. The paratypes are 100 mm and 120 mm in length. The filaments are up to 12 mm in length and up to 0.4 mm in width. The main stems are 2–5 mm in thickness.

Colour: Cream in life and in ethanol.

Ectosomal skeleton: The ectosomal skeleton of the filaments consists of a thin layer, approximately 50 µm in thickness, consisting of the isochelae perpendicular to the styles in the underlying endosome ( Figure 23 D ). The ectosome of the stem consists of a matt of isochelae and oxeas ( Figure 23 G ).

Endosomal skeleton: The endosomal skeleton of the filaments, consist of tightly bound bundles of mycalostyles ( Figure 23 C ). The smaller and thinner styles provide structural support to the filaments at the attachment of the stem ( Figure 23 F ). The endosome of the stem and roots are formed by the large longitudinally arranged mycalostyles with occasional thinner styles ( Figures 23 E–H).

Megascleres: Large mycalostyles with rounded or faintly swollen bases and blunted points (1030– 2970 x 19.2– 53.4 µm) ( Figure 22 C–D); smaller thinner less common styles with sharp points (278– 2620 x 3.0–20.0 µm) ( Figure 22 E–F); oxeas symmetrical with sharp points (303–682 x 7.5–19.9 µm) ( Figure 22 G–H) (see individual specimen measurements in Table 13 ).

Microscleres: Isochelae tridentate unguiferate with short sharp alae (49.8–65.8 x 2.4–6.5 µm) ( Figure 22 A ); rare sigmas with slight torsion (35.9–100.0 x 1.2–3.3 µm) ( Figure 22 B ) (see individual specimen measurements in Table 13 ).

Molecular data: The 28S sequence of QM G337494 is provided in the Sponge Barcoding Database under accession number SBD#2308 and the molecular difference to other congenerics displayed in Figure 3 . Chondrocladia (Chondrocladia) callistemonex sp. nov. groups with other filamentous species, and distinctly from those species with flotation spheres.

Remarks: The morphology of Ch. (Ch.) callistemonex sp. nov. is superficially reminiscent of Cladorhiza species, such as C. rectangularis Ridley & Dendy, 1887 , however, the new species possesses unguiferate isochelae rather than anisochelae. The new species shows some resemblance to Ch. (Ch.) burtoni Tendal, 1973 , and one of the specimens of Ch. (Ch.) cf. burtoni sensu Dressler-Allame et al. (2017) , but differs in having tridentate unguiferate isochelae, a narrower size range of isochelae, a second thinner category of style, a narrower/ smaller size range of sigmas, and most significantly the possession of oxeas as an additional category of megasclere ( Table 10 ). The new species has some slight similarities of a stem with horizontal filamentous stem to Ch. (Ch.) virgata Thomson, 1873 from Gibraltar, but it lacks the dichotomous branching and also differs in having tridentate isochelae compared to seven alae in the latter. This new species also vaguely resembles Ch. (Ch.) dichotoma Lévi, 1964 , but lacks a dichotomous branched stem, has differently shaped and larger tridentate isochelae, as well as having sigmas and oxeas.

Figures

FIGURE 3. Maximum-likelihood phylogram of the DNA sequences of this study in comparison with other, published cornivorous sponges. Sequences from taxa of this study are in bold. Number at the branches are RAxML rapid bootstrap values. Numbers following the taxa are either QM registration numbers (QM G3xxxxx) or NCBI Genbank accession numbers. Scale bare are substitutions per site. Please note that the reconstruction does not represent a phylogeny as due to the variability of the 28SrRNA gene C-Region barcoding marker no unambiguous alignment is possible and clipping ambiguous sites would remove diagnostic characters for taxon distinction. The tree therefore indicates molecular differences rather than a robust phylogeny.

FIGURE 22. Chondrocladia (Chondrocladia) callistemonex sp. nov. Holotype QM G337494. A. Tridentate unguiferate isochelae. B. Sigma. C. Large mycalostyle. D. Magnified ends of the mycalostyle illustrated in C. E. Subtylostyle. F. Magnified ends of the subtylostyle illustrated in E. G. Oxea. H. Magnified ends of the oxeas illustrated in G. I. Holotype QM on deck.

FIGURE 23. Chondrocladia (Chondrocladia) callistemonex sp. nov. A. Large amphipod on the stem of the holotype QM G337494. B. Small isopod trapped on one of the filaments of the paratype QM G337493. C. Filament of paratype QM G337493 showing the thick endosomal longitudinal bundle of styles. D. Ectosome of the filament of paratype QM G337493 showing the perpendicular arrangement of isochelae. E. Cross section of the stem of the holotype QM G337494 showing the radial wedges of the longitudinal mycalostyles. F. Cross section of the stem of the holotype QM G337494 showing the filaments forming at right angles to the longitudinal stem mycalostyles. G. Cross section. of the stem of the holotype QM G337494 showing the oxeas and isochelae forming the ectosomal layer of the stem (arrow pointing to the oxeas). H. Root of the holotype QM G337494 showing longitudinal arrangement of mycalostyles.