Caulophacus palmeri, Goodwin, Claire E., Berman, Jade, Janussen, Dorte, Göcke, Christian & Hendry, Katharine R., 2016

Goodwin, Claire E., Berman, Jade, Janussen, Dorte, Göcke, Christian & Hendry, Katharine R., 2016, Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species, Zootaxa 4126 (2), pp. 207-220 : 215-216

Caulophacus palmeri sp. nov.

Note: We have followed Boury-Esnault et al. 2014 who, due to molecular phylogenetic evidence, transferred the genus Caulophacus from Rossellinae to Languinellinae. They emend Tabachnick’s (2002) definition of Languninellinae as ‘ Rossellidae with strobiloplumicomes or if these are absent the concerned group(s) share so many morphological characters with a group bearing strobiloplumicomes that their common ancestry with loss of that spicule is most parsimonious…’.

Type material. MNHNCL POR_15001. Dried sample, small sub-sample rehydrated with Decon–90, tissue section and spicule preparation on slides. Sub-sample of above deposited as BELUM.Mc2015.176 (spicule slide only). Cruise sample number NBP1103–DH59–sponge03. 20th May 2011 Shackleton Fracture Zone, 60° 32.25’S, 56° 49.07’W, 1810–1820m, Hein Dredge.

Etymology. Named after the research vessel Nathaniel B Palmer which in turn is named after the merchant mariner and ship builder Nathaniel Brown Palmer (8th August 1799 – 21st June 1877) who was amongst the first people to discover Antarctica .

External appearance ( Figure 5 A). Hispid cream-coloured sponge with bulbous mushroom-like top and narrow stalk. The width of the top is 25mm and height 14mm, the stalk is 4mm maximum diameter. Preserved appearance: Delicately hispid pale peach lump with firm texture and distinct but not detachable, slightly hispid, dermal surface.

Skeleton. The specimen has been poorly preserved (dried then rehydrated) and skeletal structure is hard to see clearly. Confused choanosomal skeleton of diactines and non-pinnular hexactines. Hypodermal layer of pentactines and pinular hexactines with pinular ray facing outwards. Atrial layer of pinular hexactines. Microscleres are present throughout tissue.

Spicules. Choanosomal diactins with rounded, slightly tylote, spined ends and a small central swelling. 903– (1517)–3502 by 9.3–(18.4)–33.8 µm ( Figure 5 B). Some larger examples were also present but as these broke in both the section and spicule preparations it was not possible to measure them.

Choanosomal hexactins:Tangential ray 304–(614)–851 µm, proximal ray 310–(724)–988 µm, distal ray 304– (592)–892 µm.

Hypodermal spicules are pentactins ( Figure 5 C) and hexactins ( Figure 5 D) with spined tips. Proximal ray 476– (761)–1541 µm, tangential ray 241–(310)–421 µm.

Pinular hexactins ( Figure 5 E). Dermal pinular hexactin: Pinular ray 167–(187)–203 by 15.9–(28.6)–40.1 µm, proximal ray 69–(77)–87 by 7.4–(8.5)–11.5 µm, tangential ray 61.8–(74.1)–88.2 by 6.3–(8.3)–12 µm. Atrial pinular hexactin: Pinular ray 118–(164)–193 by 20.1–(28.3)–47.4 µm, proximal ray 33–(73)–98 by 5.4–(8.6)–12.6 µm, tangential ray 55.2–(68.3)–81.6 by 6.4–(8.1)–11.3 µm.

Discohexactins ( Figure 5 F). Ray length: 55–(63)–79 µm, total diameter 116–(135)–169 µm, centrum diameter 5.0–(8.3)–11.2 µm.

Diagnosis. Caulophacus is defined as a stalked fungus or cup–like Rossellidae with pinular hexactine dermalia and atrialia ( Tabachnick 2002). The four sub-genera which are included in the genus are defined by the type of microscleres present: Caulophacus (Caulodiscus) Ijima, 1927 has microscleres with various terminations (discoidal, onychoidal, oxyoidal); Caulophacus (Caulophacus) Schulze, 1885 has mainly discoidal microscleres; Caulophacus (Oxydiscus) Janussen, Tabachnick & Tendal, 2004 has numerous oxyhexasters, discohexasters may also be present and Caulophacus (Caulophacella) Lendenfeld, 1915 has microscleres with exclusively oxyoidal endings. ( Janussen et al. 2004). This specimen possesses only discoidal microscleres and consequently is assigned to Caulophacus (Caulophacus) .

There are 20 currently valid species of Caulophacus (Caulophacus) of which ten species have been recorded from the Southern Ocean and surrounding areas (Table 4). The majority of these possess discohexaster as well as discohexactin microscleres; the only species which do not are C. basispinosus Levi 1964 and C. galatheae Levi 1964 . However, both of these species have oxy-tipped microscleres which are not present in our specimen.

Figures

FIGURE 5. Caulophacus palmeri sp. nov. Type specimen MNHNCL POR _ 15001. A. collected specimen, scale in cm; B. end of diactin, scale bar 10 µm, SEM; C. pentactin, scale bar 100 µm, illustration traced from light microscope image; D. hexactin, scale bar 100 µm, illustration traced from light microscope image; E. pinular hexactin, scale bar 10 µm, SEM; F. discohexactin, scale bar 10 µm, SEM.