Fibulia occiensis, Rengaiyan & Palayil & Ingole, 2022

Rengaiyan, Periasamy, Palayil, John Kurian & Ingole, Baban, 2022, A new deep-sea sponge Fibulia occiensis sp. nov. (Poecilosclerida: Dendoricellidae) from the 25 ° South Oceanic Core Complex in the Central Indian Ocean Ridge, Zootaxa 5162 (1), pp. 87-96 : 89-91

Fibulia occiensis sp. nov.

( Figs 2 , 3 , 4 )

Type material

Holotype: NCPOR/HYD-CIR/0029 , Oceanic Core Complex of the Central Indian Ridge , Indian Ocean, R/V ‘MGS Sagar’ cruise MGS–35 (Station MGS-35B-BD6), 04 May 2020, 25°15’18’’ S 69°48’21.6’’ E, 1982 to 2079 m, benthic sledge, Coll. Periasamy R, samples in 70% ethanol.

Paratypes: NCPOR/HYD-CIR/0030 from the same locality as holotype.

Description

External morphology: Stalked specimen, club-shaped and is flexible. In its upper part, an apical multispicular axis is noted, with tracts in perpendicular arrangement to the main axis. The dimension is 80.5 mm in length; the peduncle length is 50.5 mm and 1 mm wide in its middle part. Both paratype and holotype are stalked. It is 4 mm in length and 0.4 mm wide. The tracts are about 3.5 mm in length and 0.4 mm in width. The main axis, with a long, very thin stem has inflated tracts that increase in size towards the apex, basal rhizoid holdfast with fine rootlets from the main axis forms a dermal brush. The surface is hispid but feels slightly smooth. The specimen is soft but the projections are firm. Beige colouring in alcohol ( Fig 2 ).

Skeleton: Choanosome skeleton consists of long and thick tracts of oxeas, arranged in a plumose manner, 200 µm thick, running from the main axis to the surface. The tracts are not differentiated into primary and secondary tracts where they somewhat bend out, running perpendicular to the surface. Here they expand transversely and terminate as brushes on the surface. The ectosomal skeleton is plumose, with inter crossing tracts (1–5 spicules) of oxeas ( Fig 3 ). The arcuate chelae are abundant and scattered throughout.

Spiculation

Megascleres: Oxea, some are slightly bent at the centre 483 (628)–700 × 19 (14.5)–21 µm, n = 25 ( Fig 4 ).

Microscleres: Arcuate isochelae are scattered through the soft tissues. The shaft is strongly curved, frontal alae well-formed. Size 30–(36)–40.5 μm length, n = 25 ( Fig 4 ).

Molecular data: We have generated molecular sequences of the Fibulia occiensis sp. nov. using 18S ( MW810071 ) and 28S rRNA ( MW810076 ) genes.

Substratum, depth range, and ecology: The OCC was mostly a mixed screen of basaltic and ultramafic along the rift valley floor and flanks. The specimens were collected from the depth range of 1982 to 2079 m. The new sponge species has foraminifera on its surface and small fragments of mollusc shells trapped in its skeleton. Other deep-sea communities associated with the sponge specimens were also collected (deep-sea corals, four types of glass sponges, shrimp, starfish, and brittle stars).

Distribution: The type locality is Oceanic Core Complex, Central Indian Ridge close to the Rodrigues Triple Junction.

Etymology: The new sponge species is named ‘ occiensis ’ for its type locality. Gender is feminine.

DNA: The sequences of Fibulia occiensis sp. nov. were submitted to NCBI GenBank and received the accession numbers: 28S MW810076 and 18S MW810071 . The 28S is 716 bp, while the 18S is 1705 bp. We have not performed a formal phylogenetic analysis since this is beyond the scope of the present paper. Nevertheless, a preliminary BLAST search indicated that these new sequences are very similar to those of poecilosclerid sponges.

Remarks: Fibulia occiensis sp. nov. is unique amongst the ten known Fibulia species, by an arrangement of its morphology and the unique shape of the isochelae with a strongly curved shaft and well-formed frontal alae. The oxeas of F. occiensis sp. nov. is similar to those of F. ramosa (oxeas 450–500 µm length ×18–25 µm width and chelae 15–16 µm length) recorded from South Africa (91–279 m). The oxeas size of F. occiensis sp. nov. is 483–(628)–700 µm in length, 14.5–(19)–21 µm in width, and the chelae size is 30–(36)–40.5 µm in length. This species was found in the deeper regions (1982–2079 m) of CIOR and is geographically close to F. ramosa and F. cribriporosa . These sponge species have been collected in the Terra Nova Bay area (17–1,100 m) during the Italian Antarctic Expeditions ( Ghiglione et al. 2018).

Figures

FIGURE 2. A, Fibulia occiensis sp. nov. holotype (NCPOR/HYD-CIR/0029), B, paratype (NCPOR/HYD-CIR/0030). C, section through the bundles of tracts showing many fine tracts. D, ectosomal skeleton plumose and feathery appearance of the body.

FIGURE 3. Fibulia occiensis sp. nov. Holotype (NCPOR/HYD-CIR/0029). A, SEM images showing the hispid surface of the sponge body and scattered arcuate isochelae forming the ectosome among the oxeas. B, the cross-section of the intercrossing tracts.

FIGURE 4. Fibulia occiensis sp. nov. holotype (NCPOR/HYD-CIR/0029). A, oxeas. B–H, arcuate isochelae.