Hyalascus keldyshi, Tabachnick & Menshenina & Ehrlich, 2023

Tabachnick, K. R., Menshenina, L. L. & Ehrlich, H., 2023, Rossellidae (Porifera: Hexactinellida) from the Bering Sea and off Bering Island, Invertebrate Zoology 20 (1), pp. 57-89 : 83-85

Hyalascus keldyshi sp.n.

Figs 25 , 26 .

MATERIAL. HOLOTYPE: IORAS 5/2/2043. RV ‘ Akademik Mstislav Keldysh’ – 22, sta. 2296, submersible ‘Mir-2’, Pacific side of the Bering Island, 55°00.8′ N 165°51.0′ E, 2200 m.

DESCRIPTION. BODY. The specimen is conical-tubular, 450 mm high, with the diameter at base being 30 mm and 120 mm off the osculum. The walls are 1–5 mm thick.

SPICULES. MEGASCLERES. Choanosomal spicules are diactins with conically pointed, rough or rarely clavate, smooth outer ends, with a widening in the middle or sometimes four rudimental tubercles.

Dermalia are spicules with micro–spine rays, mostly pentactins and stauractins, rarely hexactins. Some stauractins have a rudimental tubercle instead of the fifth ray. Tangental rays of dermal stauractins are 0. 067–0.093 mm long (n= 25, avg: 0.080 mm, std: 0.006 mm). Tangential rays of dermal pentactins are 0. 052–0.085 mm long (n= 25, avg: 0.071 mm, std: 0.009 mm), the ray directed inside the body is 0.033 –0.093 mm long (n=25, avg: 0.069 mm, std: 0.015 mm), the diameter of the rays of dermal spicules is about 0.007 mm. Atrialia are hexactins with micro-spined rays, the ray directed outside the body is the longest and most spiny, the spines themselves are longer than those on the other rays of the spicule. The ray directed outside the body of atrial hexactins is 0.118 –0.233 mm long (n=27, avg: 0.158 mm, std: 0.035 mm), tangential rays are 0.070 –0.122 mm long (n=26, avg: 0.091 mm, std: 0.015 mm), the ray directed outside the body is 0.056 –0.122 mm long (n=27, avg: 0.098 mm, std: 0.015 mm), the diameter of these rays is 0.004 –0.007 mm.

MICROSCLERES. One type of microdiscohexaster and several types of oxyoidal microscleres are present in this species. The oxyoidal microscleres have micro–spined rays, usually they are oxyhexactins and oxyhemihexasters with 1–2 secondary rays, sometimes abnormal forms of these spicules and rarely oxyhexasters (the latter could be also not finally developed microdiscohexasters). The oxyhexactins are 0.067 –0.096 mm in diameter (n=25, avg: 0.081 mm, std: 0.009 mm). The oxyhemihexasters are 0.052 –0.096 mm in diameter (n=25, avg: 0.073 mm, std: 0.012 mm), the primary rosette is 0.006 –0.011 mm in diameter (n=25, avg: 0.008 mm, std: 0.021 mm). The rare oxyhexasters are 0.074 – 0.081 mm in diameter (n=3, avg: 0.076 mm, std: 0.004 mm), the primary rosette is 0.011 –0.015 mm in diameter (n=3, avg: 0.014 mm, std: 0.002 mm). The microdiscohexasters are spherical; they have anchorate outer ends of the secondary rays represented usually by 6 units on each primary ray. The microdiscohexasters are 0.047 –0.094 mm in diameter (n=25, avg: 0.062 mm, std: 0.011 mm), the primary rosette is 0.007 –0.014 mm in diameter (n=25, avg: 0.009 mm, std: 0.002 mm).

REMARKS. Among the species of Hyalascus the new representative is characterized by spiny dermal spicules which are a combination of pentactins and stauractins. It is worth comparing it with similar species with the same spicule combinations: H. giganteus Ijima, 1898 ( Ijima, 1904) and H. farallonensis Reiswig, 2018 . Both species have dermal stauractins and pentactins. H. attenatus Okada, 1932 with dermal stauractins has however a close location. The new species has smaller rays of dermal spicules and larger size of microdiscohexasters then H. giganteus and H. farallonensis . The microdiscohexasters and oxyoidal microscleres in the new species are larger than those in H. attenatus , while the sizes of the dermal spicules rays are more or less equal to that of the new species. Hypodermal pentactins are entirely absent in this new species.

ETYMOLOGY. The species is named after RV ‘Akademik Mstislav Keldysh’ and simultaneously in memory of M.V. Keldysh.

DISTRIBUTION. Currently found only off the Pacific side of the Bering Island, at 2200 m depth.

Figures

Fig. 25. Hyalascus keldishi sp.n., holotype, external shape. Scale 50 mm. Рис. 25. Hyalascus keldishi sp.n., голотип, вне- Шний вид. МасШтаб 50 мм.

Fig. 26. Spicules of Hyalascus keldishi sp.n., holotype. A–E — dermalia. A–B — dermal pentactins. C–D — dermal stauractins. E — dermal hexactin. F — atrial hexactin. G–H — choanosomal diactins. I–O — oxyoidal microscleres. I — oxyhexactin. J — oxyhemihexaster. K — oxypentactin. L — oxystauractin. M — abnormal oxyhemihexaster. N — oxydiactin. O — oxyhexaster. P — microdiscohexaster. Рис. 26. Спикулы Hyalascus keldishi sp.n., голотип. A–E — дермальные спикулы. A–B — дермальные пентактины. C–D — дермальные стаурактины. E — дермальнаЯ гексактина. F — атриальнаЯ гексактина. G–H — хоаносомальные диактины. I–O — оксиоидальные микросклеры. I — оксигексактина. J — оксигемигексастер. K — оксипентактина. L — оксистаурактина. M — аномаль- ные оксигемигексастры. N — оксидиактина. O — оксигексастер. P — микродискогексастер.