Caulophacus (Caulophacus) ramosus Reiswig, Dohrmann & Kelly, 2021

Reiswig, Henry M., Dohrmann, Martin, Kelly, Michelle, Mills, Sadie, Schupp, Peter J. & Woerheide, Gert, 2021, Rossellid glass sponges (Porifera, Hexactinellida) from New Zealand waters, with description of one new genus and six new species, ZooKeys 1060, pp. 33-84 : 33

Caulophacus (Caulophacus) ramosus Reiswig, Dohrmann & Kelly sp. nov.

Figs 16 , 17

Material examined.

Holotype NIWA 126085, RV Sonne Stn SO254/22ROV06_BIOBOX4, Kermadec Trench slope, 29.266°S, 176.702°W, 4819 m, 04 Feb 2017.

Distribution.

Known only from the type locality, the Kermadec Trench slope, north of New Zealand (Fig. 16A ).

Habitat.

Attached to hard substratum; depth 4819 m.

Description.

Morphology of the holotype is a compound mass of a thin, convoluted stalk-part, with at least one small mushroom-shaped body branching from it (Fig. 16D, E ), and a longer, thicker, upright stalk-part bearing a larger terminal mushroom-shaped body (Fig. 16B, C ). The larger upright stalk has six lateral knobs just below the larger body on its stalk (Fig. 16C ) whose nature and function are unknown, possibly sites for attachment to a hard substratum, or are new buds. The lower convoluted stalk part branches into many attachment points, at least eight within a 27 mm length (Fig. 16D ). The smaller of the two bodies attached to this stalk system has a felt-like cover of long pinular pentactins on the outer surface (Fig. 16E ); we have had no opportunity to examine the larger body. The stalk in all parts is hollow (Fig. 16F ). Overall dimension of the larger body in the in-situ image is 45.5 mm in diameter with the stalk having a diameter of 5.9 mm at a point 5 mm below the attachment. The smaller specimen is 5.3 mm in diameter and 3.6 mm in height. Stalk diameter varies from 1.0 mm at the short branch joining the small specimen to the convoluted stalk which is mostly ca 1.8 mm thick. The connection of the convoluted part of the stalk to the thicker upright stalk part was not available for assessment. Surfaces of the small body are covered by a villous plush of long pinular pentactins, but there are no special prostalia present. The lower convoluted stalk surfaces appear devoid of any visible surface spicules, but spicule preparations of this apparently “barren” stalk still show that typical stalk spicules are present. Thus, spicules obtained from stalks may derive from other locations on the specimen and should be considered as possibly from other original sources. Surfaces of the upper straight stalk and the terminal larger body are known only from fresh seawater-wet lab photos; they are covered by a thick spiny layer of brown tissue (Fig. 16C ). Colour of the body in life is translucent white; when preserved in ethanol it is pale brown.

Skeleton. Choanosomal skeleton of the body is a network of diactins and hexactins. There is no evidence of fusion between any spicules within the body. Spicule fusion is restricted to the choanosomal diactins of the hollow stalks where the diactins are joined by fusion at spot contacts and by relatively long synapticula forming ladders. Microscleres are scattered evenly throughout the choanosome. Ectosomal skeleton of the dermal and atrial sides of the body consists of tightly packed pinular pentactins; no pinular hexactins are present. These are supported on, respectively, hypodermal and hypoatrial pentactins, which are never raised above the surfaces. Microscleres are present as in the choanosome.

Spicules. Megascleres (Fig. 17 ; Table 9 ) are hypodermal and hypoatrial pentactins, choanosomal hexactins and diactins, and pinular pentactins. Hypodermal pentactins of the body (Fig. 17A ) are regular and smooth except for spined ray ends. The proximal rays are longer, averaging 1.26 × the length of tangential rays. Hypoatrial pentactins of the body (Fig. 17B ) are also regular and smooth except for spined areas on both tangential and proximal ray ends. The proximal ray is longer, averaging 1.41 × the length of tangential rays. Hypodermal pentactins of the stalk (not figured) are regular in shape but significantly smaller than those of the body. Choanosomal hexactins (Fig. 17C ) are restricted to the body; rays are smooth and spines are present only on ray ends. Macrospines are never found in the central part of these spicules. Choanosomal diactins (Fig. 17D ) are straight or slightly curved and are smooth except for the ends; they have small but detectable central swellings. Dermal pinular pentactins of the body (Fig. 17E ) have narrow pinular rays topped with a short, blunt apical spine. Their basal rays are entirely spined and end in abruptly rounded tips. Atrial pinular pentactins of the body (Fig. 17F ) have narrow pinular rays like the dermal pinules, but with a longer pinular ray (on average 1.25 ×); however, presence of an apical spine was not determined since all of these examined in SEM had broken tips. Basal rays are like those of the dermal pinules. Stalk pinular pentactins (not figured) are morphologically similar to the dermal body pentactins.

Microscleres (Fig. 17 ; Table 9 ) are thick-rayed discohexactins and rare hemidiscohexasters and thin-rayed stellate discohexasters. Discohexactins (Fig. 17G ) are the most abundant microscleres; they have rays ornamented with large, reclined spines and a terminal disc with 5-8 marginal teeth. Rare hemidiscohexasters (Fig. 17H ) are similar to the discohexactins. Thin-rayed stellate discohexasters (Fig. 17I ) have long, smooth primary rays supporting a narrow shorter brush of 3-9 straight, rough, terminal rays ending in small discs.

Etymology.

Named for the lower, convoluted stalk part, which branches into many attachment points ( Caulophacus ramosus , branching; Latin).

Remarks.

The morphological character of all microscleres being discoid, places this species in the subgenus Caulophacus (Caulophacus) . In comparing it to the 22 recognised species of this subgenus (Table 7 ), it is apparent that there are no forms known with all pinules, both dermal and atrial, as exclusively pentactins. It is very like the previous described new species, C. (Caulophacus) serpens sp. nov. in its mainly, but not exclusively, pinular pentactins, and in the body form with a significant portion of the stalk convoluted, attached by many attachment sites and compound bearing several bodies. The two differ, however, in pinule morphology and types of microscleres. Also, molecular data (MD, unpubl. results) suggest a closer relationship of this specimen to C. (Caulophacus) arcticus , C. (Caulodiscus) valdiviae , and C. (Oxydiscus) weddelli than to C. (C.) serpens sp. nov. Since it cannot be assigned to any of the former species on the basis of morphology, it is thus clear that the form described here represents the holotype of a new species named Caulophacus (Caulophacus) ramosus sp. nov.

Figures

Figure 16. Caulophacus (Caulophacus) ramosus sp. nov., NIWA 126085, distribution, skeleton, and morphology A map of collection location on Kermadec Trench slope B in-situ image of the largest body; the irregular undulating stalk associated with it is largely hidden in accumulated sediment. The green line is 6.24 cm long copied from between laser spots elsewhere in the image C deck image of the large body, which was unavailable for taxonomic description since used for other analyses (image by PJS) D a smaller body (arrowhead) attached presumably to the same stalk but lower in the sinuous section with multiple branching attachments to small cobbles E The same body enlarged to show the plush of long atrial pinular pentactins F cross section of the larger contort white stalk and its central canal. Image B captured by ROV Team GEOMAR, ROV Kiel 6000 onboard RV Sonne (voyage SO 254), courtesy of Project PoribacNewZ, GEOMAR, and ICBM.

Figure 17. Caulophacus (Caulophacus) ramosus sp. nov., NIWA 126085, spicules A two whole hypodermal body pentactins and enlarged ray tips B two whole hypoatrial body pentactins and enlarged ray ends C a choanosomal hexactin and two enlarged ray tips D t wo whole choanosomal diactins and enlarged ends and central swellings E dermal body pinular pentactin and enlarged ray ends F atrial body pinular pentactin and enlarged ray ends G discohexactin and enlarged ray end H hemidiscohexaster I thin-rayed stellate Caulophacus discohexaster with enlarged secondary ray tuft and a secondary ray. Scale bars in A apply to B-D scales in E apply to F whole microscleres are at the same scale.