Periphragella spiridonovi, Tabachnick & Menshenina, 2025

Periphragella spiridonovi sp. nov.

( Table 1 View TABLE 1 . Figures 3–6 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material. Holotype: IORAS 5/2/3812—fragments. RV ‘Akademik M.A. Lavrentyev’—75 , ROV ‘Comanche’, sta. 18 , spec. 3–7, Piip Volcano , 55.4382 o N 167.2652 o E, depth 1569 m. GoogleMaps

Paratypes: IORAS 5/2/3802—fragments. RV ‘Akademik M.A. Lavrentyev’—75 , ROV ‘Comanche’ , sta. 18 , spec. 3–8, same with the holotype. IORAS 5/2/3839 GoogleMaps —fragments. RV ‘Akademik M.A. Lavrentyev’—75, ROV ‘Comanche’ , sta. 18 , spec. 3–2, Piip Volcano , 55.4382 o N 167.2652 o E, depth 1569 m GoogleMaps .

Body. All type materials are represented by fragments with lamellate, thin-wall about 0.6 mm of one layer of dictyonal framework. The paratype IORAS 5 /2/3802 contains also small, tubular, dichotomously branching fragments 5–10 mm in diameter. Nevertheless, the holotype was pictured before capturing. The shape of the sponge is typical for genus—with waste atrial cavity and large main osculum and tubular outgrowths on the dermal surface branching dichotomously, with small, lateral, apical oscula.

Framework. The wall is constructed of a single layer of dictyonal skeleton with square side (about 0.3 mm), rectangular side (about 0.4 x 0.5 mm) and triangular side (0.04–0.11 mm) meshes. The beams are rough 0.02–0.07 mm in diameter. Free rays of the framework, which are directed perpendicular to the body surface is rough, are 0.20–0.85 x 0.011 –0.026 mm.

Megascleres. Dermalia and atrialia are pentactins, their rays are spiny, tangential rays often have larger spines directed outside the body, some spicules often have a rudimental tubercle directed outside the body or rarely it is a short, rudimental sixth ray. The tangential rays of dermal and atrial pentactins are 0.142 –0.360 mm long, the ray directed inside the body is 0.195 –0.443 mm long, the diameter of these rays is 0.011 –0.017 mm. Clavate scopules have smooth or sometimes slightly rough surface and 2–5 tines (usually 3–4) the free end of the shaft is clavate or rounded. The clavate scopules are 0.307 –0.602 mm long with tines 0.041 –0.089 mm long, their shafts are 0.004 – 0.007 mm in diameter. The uncinates are 0.5–1,8 x 0.003 –0.011 mm.

Microscleres. Microscleres have two types of outer ends oxyoidal and discoidal (or even tyloidal). Usually they have 6 primary rays but abnormal forms with reduced number of primary rays were found among both types. The oxyoidal microscleres with 1–4 (usually 2–3) secondary rays have thin or thick rays, usually smooth but sometimes spiny. The oxyhexasters are 0.042 –0.112 mm in diameter, the primary rosette is 0.017 –0.078 mm in diameter. Discohexasters are of two types: microdiscohexasters—small with short primary rays, 2–8 secondary rays and macrodiscohexasters—large with long primary rays and 4–7 secondary rays (the letter were not found in the holotype). The microdiscohexasters are 0.020 –0.045 mm in diameter, the primary rosette is 0.006 –0.022 mm in diameter. The macrodiscohexasters were always found with 6 primary rays, they are 0.047 –0.162 mm in diameter, and the primary rosette is 0.032 –0.076 mm in diameter.

Etymology. The species is named for the memory of carcinologist V.A. Spiridonov.

Distribution. Currently found only at the Piip Volcano slope at 1569 meters depth.

Remarks. The new species definitely belongs to Periphragella due to the specific body shape, framework construction and spicule combination. The most important is simultaneous presence of oxyoidal and discoidal or tyloidal hexasters among microscleres.Compared to valid species of this genus ( P.antarctica , P.challengeri , P.elisae , P. irregularis , P. japonica , P. lusitanica , P. parva ( Topsent, 1928; Janussen et al., 2004)), the new representative has several very peculiar features: smooth clavate scopules and a type of oxyoidal microscleres with very thick rays: thick rays are found in dermal and atrial pentactins. The new species is mostly similar to P. elisae known from off Japan and the Moluccas. Smooth clavate scopules are shown in the picture of P. elisae (the revised holotype ( Reiswig et al., 2002)), but in the text it is written that the clavate tines are “microspined” unlike the smooth tines of the new species described above. P. spiridonovi sp. nov. has notable differences in spicule sizes (Tab. 2) and thick-rayed oxyoidal microscleres. The single layered framework is also a unique feature of the new species. But highly likely it is a character of the investigated specimens since “dead” specimens of Periphragella captured in close distance have multilayered framework (see below).