Iophon koltuni Morozov & Sabirov & Zimina 2019, sp. nov

Iophon koltuni sp. nov

(Figure 3 (a – d1))

Iophon piceus dubius Koltun 1959, p. 151 – 152, fig. 107; pl. XXVI, fig. 2

Iophon cf. nigricans: Dinn and Leys 2018, p. 33

Material examined

The holotype was collected at the edge of the continental shelf at the central part of the Laptev Sea (76.76°N, 124.28°E), and deposited in the Edward Eversman Zoology Museum (identification number 2.2.8.443).

The paratype was found in the east of the southern tip of Spitsbergen (75.82°N, 25.62°E).

Description

The examined fragment of sponge is massive and more or less leaf-shaped, with several poorly pronounced lobes, about 8 cm in width and 2 cm in height. Surface uneven, slightly scabrous, coarse-pored, covered with a thin dermal membrane. Disorderly scattered irregular openings (oscules) are often covered by a coarse sieve, or partly hidden by the edges of dermal membrane surrounding them. The dermal membrane (where undamaged) is pierced by numerous small roundish pores often lying in meshes. The consistence of the body is soft and compressible, but not strong in tension. Colour dark brown (in alcohol).

Skeleton

Main skeleton composed of a quite diffuse network of acanthostyles lying in bundles and disorderly scattered single spicules of the same category. Skeleton of dermal membrane consists of similar network of tylotes lying more or less tangentially.

Spicules

(Figure 3 (a – d1)) Acanthostyles straight or slightly curved, dimensions: 226.1 – 296.9 – 324.7 (n = 40) × 6.3 – 10.2 – 12.1 (n = 15) µm; tylotes with slightly spined ends, dimensions: 249.8 – 266 – 286.2 (n = 15) × 6.5 – 7.8 – 9.6 (n = 15) µm; palmate anisochelae, dimensions: 15.4 – 22.6 – 38.7 (n = 15) µm; bipocilla, dimensions: 10.4 – 12.85 – 16.9 (n = 30) µm.

Etymology

The species is named in honour of Vladimir M. Koltun (1921 – 2004) – an outstanding Russian zoologist and spongiologist.

Distribution

The Barents (south-east of Spitsbergen: 75.82°N, 25.62°E) and Laptev (st. O-18) seas, the Labrador Sea. Depth range: 92 – 141 m.

Remarks

Lundbeck (1905) in his monograph provided detailed descriptions of three representatives of the genus Iophon that inhabit the Nordic seas and adjacent Arctic: I. piceus, I. dubius and I. frigidus. Regarding the delimitation of these species, he suggested some differences mainly concerning style spination, the form of tylotes, and spicule dimensions in general, as well as the presence or absence of bipocilla. As Burton (1932) and later Koltun (1959, p. 140 – 150) noted, such minor differences may hardly be considered sufficient reason for species delimitation. Koltun examined 152 specimens of Iophon and proposed two subspecies for the Arctic seas. The first, Iophon piceus piceus, was identical to Iophon piceum (Vosmaer 1882). Iophon dubium (Hansen 1885) and I. frigidus (Lundbeck 1905) were united under the name Iophon piceus dubius. However, the variety of Iophon piceus dubius described by Koltun differed from both mentioned species. I. frigidus (Lundbeck 1905) is characterised by the absence of bipocilla in its skeletal composition, while in I. dubius (Hansen 1885) the bipocilla differed significantly in morphology (Figure 4). In the case of I. p. dubius the bipocilla have the identical, distinctly reduced alae, the length of which is half the size of the shaft of the spicule, and are provided with laterally arranged elongated teeth. The same distinctions from previously described Iophon species were mentioned for the specimens of I. cf. nigricans found in the Canadian Arctic by Curtis and Leys (2018). Thus, the validity of Iophon koltuni sp. nov. removed any doubts.