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

Figs 14 , 15

Material examined.

Holotype NIWA 126084, RV Sonne Stn SO254/22ROV06_BIOBOX6, Kermadec Trench slope, 29.266°S, 176.702°W, 4816 m, 04 Feb 2017.

Distribution.

Known only from the type locality, the Kermadec Trench slope, north of New Zealand (Fig. 14A ).

Habitat.

Attached to large pieces of rubble lying on a sediment plain at 4816 m.

Description.

Morphology of the holotype a rhizome-like, hard, hollow, thin stem that creeps across the sediment seabed, attaching to rubble here and there, in places forming a tangled mass, from which arises the main mushroom-shaped body on a zigzag stem (Fig. 14B, C ), and two tiny, mushroom-shaped bodies (Fig. 14D ). Overall dimension of the holotype, spreading across the seabed, is 64 cm. Dimension of the larger body (Fig. 14B ) is 22.2 mm in diameter and 11.2 mm in height; its associated stalk is 3.6 (2-6-4.3) (n = 12) mm in diameter. The associated stalk measures 3.3 (2.7-4.0) (n = 29) mm in diameter, the length, measured in conformation from the body to the stalk tangle, is 167 mm. The smaller bodies (Fig. 14D ) are 7.2 × 5.4 and 5.2 × 4.3 mm in diameter and height, respectively; the stalk of the larger one is 1.1 (1.0-1.3) (n = 12) mm in diameter. The piece of thick stalk received from NIWA is 72 mm long and 3.0 (2.8-3.3) (n = 12) mm in diameter, approximately the same gauge as the convoluted stalk shown in the in situ and deck images. Surfaces of the body are a bit lumpy and fuzzy (Fig. 14D ); that of the thin attached stalks is also fuzzy. There are no projecting prostal spicules. Colour of the body in life is white, and the stem pale brown; when preserved in ethanol it is very pale brown, almost white.

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 synapticula and points of spot contacts between spicules. Microscleres are scattered evenly throughout the choanosome. Ectosomal skeleton of the dermal and atrial sides of the body and living stalks consists of tightly packed pinular pentactins and very few pinular hexactins (1.3% of 374 assessed). 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. 15 ; Table 8 ) are hypodermal and hypoatrial pentactins, choanosomal hexactins and diactins, and pinular pentactins and a few pinular hexactins. Hypodermal pentactins of the body (Fig. 15A ) are regular and usually smooth except for spined ray ends; 31% have macrospines on the central part of the proximal ray. The proximal rays are longer, averaging 1.21 × the length of tangential rays. Hypoatrial pentactins of the body (Fig. 15B ) are regular and spined on both tangential and proximal ray ends; macrospines are present on the central part of most (60%) proximal rays but all tangential rays lack macrospines. The proximal ray is longer, on average 1.86 × the length of tangential rays. Hypodermal pentactins of the stalk (Fig. 15C ) are regular in shape but significantly smaller than those of the body; they are spined on ray ends but macrospines are uncommon (12%) on the central part of only the proximal rays. Proximal rays are generally longer, on average 1.49 × tangential ray length. Choanosomal hexactins (Fig. 15D ) are restricted to the body; rays are smooth, and spines are restricted to the ray ends. Macrospines are never found in the central part of these spicules. Choanosomal diactins (Fig. 15E ) are straight or slightly curved and are smooth except for ends; they have small but detectable central swellings. Dermal pinular pentactins of the body (Fig. 15F ) have narrow pinular rays topped with a short, sharp apical spine. Their basal rays are entirely spined and end in abruptly pointed tips. Approximately 10% of the dermal pinules are hexactine forms. Atrial pinular pentactins of the body (Fig. 15G ) have narrow pinular rays like the dermal pinules but with a longer pinular ray (on average 2.1 ×) and longer apical spine; basal rays are like those of the dermal pinules. Stalk pinular hexactins (Fig. 15H ) have a pinular ray that is narrow in its basal half but curves to one side and swells in width apically, assuming an overt club-shape. It has no atrial spine since the apex is enfolded by the apical scales. Basal rays are like those of the dermal and atrial pinules.

Microscleres (Fig. 15 ; Table 8 ) are discohexactins, thick-ray discohexasters and thin-ray discohexasters. Discohexactins (Fig. 15I ) are the most abundant microscleres; they have rays ornamented with large, reclined spines and a terminal disc with 5-8 marginal teeth. Thick-ray discohexasters (Fig. 15J ) are the least abundant microsclere; they are spherical, have 6-9 thorned terminal rays on each smooth primary ray, and terminal discs have 4-8 marginal teeth. Thin-ray discohexasters (Fig. 15J, K ) are among the most numerous microscleres, but comparing their abundance with discohexactins is not possible since detection of the two spicule types requires different microscope arrangements. They are semi-stellate with each smooth primary ray supporting 16 (8-28) (n = 16) thorned terminal rays ending in discs with 3-7 marginal teeth.

Etymology.

Named for the rhizome-like stem that may form tangled, convoluted stems from which the main bodies arise, the whole creeping along the substrate ( Caulophacus serpens , creeping; Latin).

Remarks.

The morphological character of all microscleres being discoid, places this species in the subgenus Caulophacus (Caulophacus) . In comparing them to the 22 recognised species of this subgenus (Table 7 ), it is apparent that there are no forms known with both dermal and atrial spicules as mainly pinular pentactins. It is thus clear that the form described here is the holotype of a new species named Caulophacus (Caulophacus) serpens sp. nov.

Figures

Figure 14. Caulophacus (Caulophacus) serpens sp. nov., NIWA 126084, distribution, skeleton, and morphology A distribution in New Zealand waters, collection location of holotype on the Kermadec Trench slope B in situ image of the largest specimen body and the irregular undulating stalk associated with it. The laser spots indicated by the arrows are 6.24 cm apart C deck image of the same with smaller specimens in the stalk tangle at right (image by PJS) D two smaller bodies and their stalks, previously attached to the main mass, used for spicule analysis E cross sections of the uncleaned stalk of the larger specimen in D; F Acid-cleaned part of the stalk of the same (SEM) G closer view of the outer stalk surface showing most fused diactins oriented nearly parallel to the stalk axis (SEM) H close view of the internal stalk surface showing most superficial spicules oriented at large angles to the stalk axis (SEM). Image B captured by ROV Team GEOMAR, ROV Kiel 6000 onboard RV Sonne (voyage SO 254), courtesy of Project PoribacNewZ, GEOMAR, and ICBM.

Figure 15. Caulophacus (Caulophacus) serpens sp. nov., NIWA 126084, spicules A hypodermal body pentactin B hypoatrial body pentactin C hypodermal stalk pentactin D two whole choanosomal hexactins and an enlarged ray end E two whole choanosomal diactins and enlarged ends and central swellings; F dermal body pinular pentactin G atrial body pinular pentactin H stalk dermal pinular pentactin I discohexactin with enlarged terminal ray and facial view of end disc J large thick-rayed Caulophacus discohexaster with two smaller thin-rayed discohexasters entangled K thin-rayed Caulophacus discohexaster and magnified terminal ray. Scale bar in A applies to B-E scale bar in F applies to G and H whole microscleres are at the same scale.