Caulophacus (Caulophacus) subarcticus, 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 : 80-82

Caulophacus (Caulophacus) subarcticus sp.n.

Figs 21 , 22 ; Suppl. Tab. 13.

MATERIAL. HOLOTYPE: IORAS 5/2/2274: RV ‘ Akademik Mstislav Keldysh’ – 22, sta. 2306, trawl, Pacific sine of the Bering Island, 54°57.1– 57.7′ N 165°49.9 –51.0′ E, 4401– 3797 m.

DESCRIPTION. BODY. The specimen is fungus–like with a discoidal body 25 mm in diameter and 1–2 mm in thickness. The peduncle is about 1.5 mm in diameter and 35 mm long.

SPICULES. MEGASCLERES. Choanosomal spicules are diactins and hexactins. The diactins are divided into two types: large and small. The former (about 1.5/ 0.02 mm) have stout shafts, conically pointed outer ends. Common diactins are thin with a widening in the middle, the outer ends are rough, rounded or clavate, these diactins are 0.9–2.4/ 0.006 – 0.009 mm. Choanosomal hexactins have conically pointed outer ends, their rays are 0.6–0.8/ 0.02–0.04 mm. Hypodermal and hypoatrial pentactins have smooth tangential rays or they are spiny at base, the ray directed inside the body may be spiny, the outer ends are smooth, conically pointed. The tangential rays of hypodermal and hypoatrial pentactins are 0.3–0.5 mm long, the ray directed inside the body is 0.6–1.0 mm, the diameter of these rays is 0.02–0.03 mm. Spicules of the peduncle are diactins about 8/ 0.006 –0.023 mm with stout shafts, rounded or clavate outer ends. Unlike the penduncular diactins of other species, these do not fuse to each other.

Dermalia are hexactins as well as rare pentactins with a rudimental tubercle instead of a sixth ray directed inside the body. Dermal hexactins include those with clavate pinular rays and long tangential rays as well as those with a lanceolate pinular ray. The tangential rays and the ray directed inside the body are rough or short-spiny at their distal half with conically pointed outer ends. The clavate pinular ray of dermal hexactin is 0.037 –0.141 mm long (n=25, avg: 0.079 mm, std: 0.023 mm), maximal diameter of this ray is 0.011 mm, tangential rays are 0.041 –0.107 mm long (n=25, avg: 0.087 mm, std: 0.015 mm), the ray directed inside the body is 0.030 –0.093 mm long (n=25, avg: 0.066 mm, std: 0.018 mm), the diameter of these rays is 0.006 mm. Lanceolate pinular ray of dermal hexactin is 0.070 –0.159 mm long (n=25, avg: 0.123 mm, std: 0.020 mm), the maximal diameter of this ray is 0.004 mm, tangential rays of these spicules are 0.052 –0.081 mm long (n=25, avg: 0.064 mm, std: 0.010 mm), the ray directed inside the body is 0.033 –0.078 mm long (n=25, avg: 0.059 mm, std: 0.011 mm), the diameter of these rays is about 0.003 mm. Atrialia are pentactins with rudimental tuberculated ray directed inside the body or sometimes hexactins, these spicules have pinular ray elongate and short–spiny, other rays are equal to those of dermal spicules. The pinular ray of atrial pentactin is 0.130 –0.285 mm long (n=25, avg: 0.209 mm, std: 0.036 mm), about 0.007 mm in diameter, tangential rays are 0.041 –0.111 mm long (n=25, avg: 0.079 mm, std: 0.016 mm), the rudimental ray is 0.007 – 0.022 mm long (n=25, avg: 0.012 mm, std: 0.003 mm), the diameter of these rays is 0.005 –0.006 mm. Atrial hexactins have pinular rays 0.130 –0.266 mm long (n=14, avg: 0.181 mm, std: 0.034 mm), tangential rays 0.044 –0.104 mm long (n=14, avg: 0.083 mm, std: 0.016 mm), the ray directed inside the body is 0.048 –0.081 mm long (n=14, avg: 0.065 mm, std: 0.008 mm).

MICROSCLERES. All microscleres have discoidal outer ends and include discohexasters, discohexactins and lophodiscohexasters. Discohexasters have 3–7numerously spiny secondary rays are 0.111 – 0.289 mm in diameter (n=25, avg: 0.191 mm, std: 0.033 mm), the diameter of the primary rosette is 0.037 –0.067 mm (n=26, avg: 0.054 mm, std: 0.010 mm). Discohexactins have thin (about 0,006 mm in diameter), long, spiny rays are 0.148 –0.237 mm in diameter (n=26, avg: 0.194 mm, std: 0.025 mm). Discohexactins with thick (about 0.007 mm in diameter), short spiny rays are less numerous, they are 0.067 –0.163 mm in diameter (n=15, avg: 0.130 mm, std: 0.026 mm). Discohexasters with thick, short, spiny rays are very rare, they are 0.133 mm in diameter (n=1), the diameter of the primary rosette is 0.022 mm (n=1). The lophodiscohexasters have 4– 20 secondary rays are 0.036 –0.112 mm in diameter (n=28, avg: 0.066 mm, std: 0.016 mm), the diameter of the primary ray is 0.025 –0.054 mm (n=28, avg: 0.035 mm, std: 0.006 mm). Sometimes the shafts of lophodiscohexasters have some irregular spines of tubercles. Some intermediate in shape forms between lophodiscohexasters and discohexasters with spiny secondary rays may be found.

REMARKS. Among more than 20 species of Caulophacus , the new species, C. subarcticus , distinguishes by numerous types of microscleres, as well as variable dermal and atrial spicules, especially by their form of the pinular ray. It is very difficult to consider some of them to have allochthonic origin since they were the only representative of Caulophacus in the trawl sample. Some similarities may be found between the new species and Caulophacus arcticus Hansen (see one of the latest description of Koltun, 1967), known from the N Atlantic and Arctic Oceans; however the differences between these species are well-seen from the corresponding Suppl. Tab. 13.

ETYMOLOGY. The species name is originated from the name of the closest species Caulophacus arcticus .

DISTRIBUTION. Currently found only off the Pacific side of Bering Island, at 4401– 3797 m depth.

Figures

Fig. 21. Caulophacus (Caulophacus) subarcticus sp.n., holotype, external shape. Scale 10 mm. Рис. 21. Caulophacus (Caulophacus) subarcticus sp.n., голотип, внеШний вид. МасШтаб 10 мм.

Fig. 22. Spicules of Caulophacus (Caulophacus) subarcticus sp.n., holotype. A–B — dermal pinular hexactins. C — dermal pinular pentactin. D–E — atrial pinular pentactins. F — hypodermal or hypoatrial pentactin. G — choanosomal hexactin. H–I — choanosomal diactins. J — thick-rayed discohexactin. K — thin–rayed discohexactin. L — discohexaster. M — intermedium spicule between discohexaster and lophodiscohexaster. N — lophodiscohexaster. Рис. 22. Спикулы Caulophacus (Caulophacus) subarcticus sp.n., голотип. A–B — дермальные пинулЯр- ные гексактины. C — дермальнаЯ пинулЯрнаЯ пентактина. D–E — атриальные пинулЯрные пентак- тины. F — гиподермальнаЯ или гипоатриальнаЯ пентактина. G — хоаносомальнаЯ гексактина. H–I — хоаносомальные диактины. J — дискогексактина с толстыми лучами. K — дискогексактина с тонкими лучами. L — дискогексастер. M — спикула промежуточнаЯ между дискогесастером и лофодискогексастером. N — лофодискогексастер.