Caulophacus (Caulophacus) discohexaster Tabachnick & Levi , 2004

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) discohexaster Tabachnick & Levi, 2004

Figs 12 , 13

Type and locality (not examined).

Holotype - MNHN HCL519, Norfolk Ridge, HALlPRO 2, Zoneco Stn BT 062, 24.71°S, 168.648°E, 720-1048 m.

Material examined.

NIWA 126342, RV Sonne Stn SO 254/85ROV19_BIOBOX6, Southern Kermadec Ridge , 35.609°S, 178.854°E, 1163.6 m, 24 Feb 2016 ; NIWA 126343, RV Sonne Stn SO 254/85ROV19_BIOBOX17, Southern Kermadec Ridge , 35.612°S, 178.852°E, 1149.8 m, 24 Feb 2017 .

Distribution.

Known from the type locality, Norfolk Ridge near New Caledonia, and southern Kermadec Ridge, ~ 223 km N of East Cape, North Island, New Zealand.

Habitat.

Attached to hard substratum; depth 720 to 1348 m (New Zealand locations, Fig. 12A ).

Description.

This description refers to New Zealand specimens only. Body forms a solitary mushroom cap-shaped upper body on a long, kinked, somewhat crooked, flattened, hollow stalk (Fig. 12B, E ). Surfaces of the upper body are smooth (Fig. 12C, D ) with a slight blunt eminence on the outer atrial face opposite the stalk insertion, but there is no indication of an osculum. The upper dermal surface lacks any visual indication of a lattice. The lower dermal surface of the specimen is divided by ridges into six depressions not seen in the smaller specimen. The stalks of both are flattened and that of the smaller bears a cylindrical central canal (Fig. 12F ). SEM views of the dried surfaces show pores in the dermal body surface membrane (Fig. 12G ), apparently contracted pores in the atrial body surface involving the atrial pinules (Fig. 12H ), and no indication of pores on the dermal stalk surface (Fig. 12I ). Dimensions of the smaller specimen upper body is ~ 12.5 × 10.6 cm in diameter; stalk is 15.9 × 9.0 mm in diameter and stalk canal is 4.1 × 3.3 mm in diameter. Length of the stalk could not be approximated. The larger specimen upper body is 25.0 × 15.9 cm in diameter while the flattened stalk is 5.9 cm wide. Measurable ostia of the smaller specimen (Fig. 12G ) are 70 and 99 µm in diameter. Texture of the body is firm but compressible; the stalk is hard. Surface of all parts are smooth, consisting of tight palisades of pinular rays of dermalia and atralia supported on hypodermal and hypoatrial pentactins. There are no projecting prostalia. Colour in life is pale pinkish brown as are the specimens preserved in ethanol.

Skeleton. Choanosomal skeleton of the body consists of a tight network of choanosomal hexactins and diactins. There is no evidence of fusion between any spicules within the body. Microscleres are scattered evenly throughout the choanosome. The stalk internal skeleton is composed of large diactins oriented longitudinally and fused by synapticula. Ectosomal skeleton of the dermal and atrial sides consists of tightly packed pinular hexactins and very few pinular pentactins (1.6% of 623 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. 13 ; Table 6 ) are hypodermal pentactins, choanosomal hexactins and diactins, and pinular hexactins and a few pentactins. Hypodermal pentactins of the body (Fig. 13A ) are regular and usually smooth except for spined ray ends; 8% have indistinct spines on the proximal part of the proximal ray. The proximal rays are longer, averaging 1.24 × the length of tangential rays. Hypoatrial pentactins of the body (Fig. 13B ) are regular and spined on both ray-ends and 61% of them on the proximal part of the proximal rays. The proximal ray is longer, averaging 1.62 × the length of tangential rays. Hypodermal pentactins of the stalk (Fig. 13C ) are regular in shape but significantly smaller than those of the body; they are spined only on ray ends. Tangential and proximal rays are approximately equal in length. Choanosomal hexactins (Fig. 13D ) are restricted to the body; rays are smooth, and spines are restricted to the ray ends except where the ray is exceptionally short. These hexactins occur in two forms, one with a short spiny ray (upper figure) and the other with all rays approximately equal in length (lower figure). Choanosomal diactins (Fig. 13E ) are straight or slightly curved and are smooth except for ends on which they have small but detectable central swellings. Dermal pinular hexactins of the body (Fig. 13F ) have bushy, nearly cylindrical pinular rays with a short, thick, rounded apical tip. Tangential and proximal rays are entirely spined and approximately similar in size and shape. Very rarely, these and pinules of other body surfaces are pentactine with only a round nub in place of the proximal ray. Atrial pinular hexactins of the body (Fig. 13G ) have pinular rays that taper in length of scales at both ray ends, resulting in fusiform shape. The pinular ray has a thick and rounded tip. Tangential and proximal rays are entirely spined and similar in size and shape. Stalk pinular hexactins (Fig. 12H ) have a pinular ray that is squat and slightly wider than those of the body spicules. Scale lengths taper basally and apically and again the apex of the pinule is a blunt, thick cap. Tangential and proximal rays are entirely spined and similar in size and shape.

Microscleres (Fig. 13 ; Table 6 ) are discohexactins (43% of 221 assessed), hemidiscohexactins (54.7%), and discohexasters (2.3%); all are thick-rayed forms. Discohexactins (Fig. 13I ) have rays ornamented with large, reclined spines and a terminal disc with 5 (4-7) marginal teeth. Hemidiscohexasters (Fig. 13J ) are similar with at least one ray being branched and at least one ray being unbranched; the total number of rays is 9.4 (7-13). Terminal discs are similar to discohexactins. Discohexasters (Fig. 13K ) have all primary rays branched varying from 2-6 terminal rays on each primary ray. Terminal discs have 3-8 marginal teeth.

Remarks.

The morphological characters of the two New Zealand specimens place them clearly in subgenus Caulophacus (Caulophacus) , of which there are 22 recognised species. Table 7 compares the key morphological characters that differentiate them from each other and from the New Zealand specimens, NIWA 126342 and NIWA 126343. We admit that some of these differences are subjective and the list is not exhaustive. Table 7 shows only a single species, C. (C.) discohexaster , that has a single morphological difference from the specimens described here, i.e., the visual impression of the dermal pinule ( Tabachnick and Lévi 2004: 51, fig. 24A). Measurement of the dermal pinule in that figure shows that the figured pinular ray is too wide (84 µm) to fit within the data given for the pinular ray of the dermal hexactin given there (106-220 µm /30-46 µm). Removing this illustration error from the list results in no differences between the New Zealand specimens and the type material described by Tabachnick and Lévi (2004) from New Caledonia; therefore, we assign the specimens to that species.

Figures

Figure 12. Caulophacus (Caulophacus) discohexaster Tabachnick & Levi, 2004, NIWA 126342, 126343, distribution, skeleton, and morphology A distribution in New Zealand waters B smaller specimen, NIWA 126342 in situ C smaller specimen atrial surface on-deck image D smaller specimen dermal surface and stalk connection (deck images by PJS) E larger specimen, NIWA 126343 in situ F section of the stalk of the smaller specimen G-I SEM images of surfaces of smaller specimen; dermal G atrial H and stalk I at same magnification. Images B and E captured by ROV Team GEOMAR, ROV Kiel 6000 onboard RV Sonne (voyage SO 254), courtesy of Project PoribacNewZ, GEOMAR and ICBM.

Figure 13. Caulophacus (Caulophacus) discohexaster Tabachnick & Levi, 2004, NIWA 126342, spicules: A hypodermal body pentactin; whole and enlarged tangential and proximal ray ends B hypoatrial body pentactin; whole and enlarged tangential and proximal ray ends C hypodermal stalk pentactin; whole and enlarged tangential and proximal ray ends D choanosomal hexactins; two whole and enlarged ray end E choanosomal diactins; two whole and four enlarged ends and one central swelling F dermal body pinular hexactin G atrial body pinular hexactin H stalk dermal pinular hexactin I discohexactin J hemidiscohexaster K Caulophacus discohexaster and magnified terminal ray and terminal disc. Scale bars in A apply to B and C; scale bar is the same for F-H, I-K.