Chondrocladia sagari sp. nov.

Figure 6–7, Table 3

Material examined. Holotype. NCPOR /HYD-CIR/0035, seamount of the Central Indian Ridge, Indian Ocean, 23° 9’ 12.96’’ S, 69° 31’ 13.8’’ E, 2103 m, 20 April 2020, Benthic Sledge, Coll. Periasamy R, samples in 70% ethanol, MGS Sagar, cruise no: MGS-35, Sample MGS 35A-D11.

Etymology. Species name “sagari” refers to the Ocean. Sagar means ‘Ocean’ in Hindi. Gender is feminine.

Diagnosis: Holotype (Figure 6A) an erect columnar pedunculate sponge with a slender body bearing small filaments processes. The specimen is 3.1 cm in length a 0.5 cm wide. The sponge surface is rough and rigid, and roots are missing. The colour of the sponge is white, cream to clear brown in alcohol.

Skeleton: The Axis of peduncle consisting of tightly packed longitudinally large mycalostyles, and elongating to the center of the body (Figure 6C). The enlarged part of the peduncle is composed of mycalostyles and subtylostyles. The body filaments consist of bundles of subtylostyles, covered by soft tissue tightly packed with unguiferate isochelae, and sigmancistras (Figure 6B–F).

Megascleres: Styles in two categories (Figure 6A–B), the mycalostyles occur in the main stem with an abrupt shrinking near the head and a short acerate tip. The diameter was maximum in the middle of the shaft, slightly reducing towards both the ends. Size is 1975–(2440)–2659/15–(21)–36 µm (Figure 7A).

Subtylostyles of lateral filaments or body consists of a marked oval head. The subtylostyles occur mainly in the body radially orientated and penetrating the ectosome producing make the hispid surface, but also occur in the small tentacular processes. Size is 438–(974)–1988/16–(23)–28 µm (Figure 7B).

Microscleres: Multidentate unguiferate isochelae is common in the body and very abundant in the swellings, with four alae at each end. Alae are relatively short, sharp, with a well-marked hull on the underside. Shaft curved, with narrow fimbriae. Size: 37–(44)–53 µm in length with a diameter of 3–(4)–5 µm (Figure 7C).

Sigmas (“C”&“S” shapes) are slim and curved differently (Figure 7D). Size: 97–(120)–132 µm in length, 3–(4)–4 µm in diameter (Table 3).

Remarks. Our specimen sampled from the Central Indian Ocean, from the lower bathyal at 2103 m depth, is more similar to Chondrocladia clavata Ridley & Dendy (1887) species which is commonly recorded from the Southern Hemisphere (Dressler-Allame et al. 2017, Ekins et al. 2020). C. clavata and C. gracilis Lévi, 1964 have similar mycalostyles in the stem as C. sagari sp. nov., but also have a tridentate unguiferate isochelae in the filaments and body, whereas C. sagari sp.nov. has two categories of styles and a unique multidentate (4 alae) unguiferate isochelae and “C”&“S” shapes sigmas. C. gracilis Lévi, 1964 has a similar spicule type (mycalostyles and subtylostyles) in the stem, body, and filaments, but these are generally smaller than those of the C. sagari sp. nov. The new species is similar to previous descriptions of C. clavata Ridley & Dendy (1887), and more recently Dressler-Allame et al. (2017) who described from the Southern Ocean, and also described at bathyal and abyssal depths off the east coast of Australia during the RV Investigator 2017 Abyss Expedition (Ekins et al. 2020). Both species also resemble C. crinita in external morphology but have much smaller isochelae. The other species of Chondrocladia originally described from the Indian Ocean, namely C. clavata Ridley & Dendy, 1886, C. gracilis Lévi, 1964, C. multichela Lévi, 1964, and C. dichotoma Lévi, 1964, having differed in spicule characters. The morphological descriptions of the new species have been compared with all other species of Chondrocladia in Table 4.

The Chondrocladia sagari sp. nov. is recovered as a sister species to C. vaceleti Cristobo, Urgorri & Rios, 2005 with high bootstrap support (48%) and shows a separate branch in the phylogenetic tree based on the mtCOI gene (Figure 8).

Molecular data. GenBank accession number mtCOI: MW868387.

Distribution. Chondrocladia sagari sp. nov. is known for its type locality in the seamounts of the Central Indian Ridge system.