(Figs 7A–H, 8A–D; Table 7)
Diagnosis. Achramorpha with cortical skeleton composed of big triactines and thin diactines. Aquiferous system syconoid with rounded choanocyte chambers.
Type locality. Norwegian Sea.
Synonyms and citations. Leucosolenia sp. Borojević & Graat-Kleeton 1965, p. 84; Clathrina sp. Barthel et al. 1993, p. 85.
Material examined. Holotype: ZMBN- 127207, Norwegian Sea, G.O. Sars 2008-SL1, collection date 03.07. 2008. 2425 m depth (73°35.32’N 07°45.119’E). Paratype: ZMBN- 127208, Norwegian Sea, GS14-AGT04- N24, collection date 30.7.2014, 2651 m depth (73°42.129’N 07°23.854’E). Paratype: NHMD- 611895, Norwegian Sea, Ingolf expedition st. 113, collection date 21- 22.07.1896, 2465 m depth (69°31’N 07°06’W).
Etymology. Named after the Danish Ingolf Expedition where the first specimens were collected in 1896.
Spicules. Diactines: thin and straight with sharply pointed ends. One of the ends can be lanceolate asymmetrically (Figs 7D, 8A–B). Some diactines are also thin but curved (Fig 8B). Both group of diactines are found in the oscular region and in the cortical skeleton. Size: 135.5 ± 31.6 µm length, 3.0 ± 0.9 µm width (Table 7).
Cortical triactines: sagittal with slightly bent paired actines, and straight and longer unpaired actines. Size: unpaired actines 368.6 ± 42.7 µm length, 12.0 ± 1.3 µm width; paired actines 235.6 ± 35.9 µm length, 12.3 ± 1.8 µm width (Fig 8C; Table 7).
Chiactines: paired and unpaired actines straight, forming a tripod, while the apical actine is sharply bent, with the shape of a blade. Size: unpaired actines 297.7 ± 50.7 µm length, 9.5 ± 1.2 µm width; paired actines 138.5 ± 23.7 µm length, 7.9 ± 1.5 µm width; apical actines 64.2 ±16.0 µm length, 6.0 ± 1.3 µm width (Fig 8D; Table 7).
Distribution and depth. This is a deep-sea species which has been found in the Norwegian Sea and Greenland Basin, at 2425–2651 m depth.
Molecular identification. Sequences available in GenBank under the following accession numbers: for 28S rRNA MH385224 (ZMBN-127208, GIN05), MH385157 (ZMBN-127207, SA127); and for 18S rRNA MH385225 (ZMBN-127208, GIN05), MH385158 (ZMBN-127207, SA127) (Alvizu et al. 2018).
Remarks. The shape of the diactines and the absence of tetractines, represent distinctive characters of this new species from the deep-sea. Some of the diactines present a similar shape than the typical minute diactines reported in most species of the family Achramorphidae, but instead of presenting minute spines, the diactines of A. ingolfi sp. nov. are lanceolate with smooth surface and slightly longer. The spicule sizes are very variable, both within each sponge, and between different specimens. The triactines are the most variable in size (unpaired actines 153.0– 652.8 µm leng h, 12.0– 17.3 µm width; paired actines 112.2–408.0 µm length, 12.3–18.2 µm width), but also the chiactines show differences, especially the width (unpaired actines 9.5–11.7 µm width; paired actines 7.9–13.6 µm width; apical actines 6.0– 8.7 µm width).