Glass Sponges off the Newfoundland (Northwest Atlantic): Description of a New Species of Dictyaulus (Porifera: Hexactinellida: Euplectellidae)

Thehexactinellid fauna of the northwestAtlantic is remaining poorly investigated up to now. A unique notable population ofVazella pourtalesi Schmidt was recently described from the adjacent area (the shelf of Scotia) [1], a monospecific genus previously known by few specimens from two findings in the Caribbean Sea off Florida and off Azores [2]. The present work complements data on hexactinellid fauna of the northwest Atlantic (the Newfoundland area). It is based on materials collected on groundfish bottom trawl surveys and on NEREIDA cruises. We describe a new species ofDictyaulus, a genus known for a long time by a single representative from the Indian Ocean, and recently two species from the central Pacific [3] and the north Atlantic [4] were described.


Introduction
The hexactinellid fauna of the northwest Atlantic is remaining poorly investigated up to now. A unique notable population of Vazella pourtalesi Schmidt was recently described from the adjacent area (the shelf of Scotia) [1], a monospecific genus previously known by few specimens from two findings in the Caribbean Sea off Florida and off Azores [2].
The present work complements data on hexactinellid fauna of the northwest Atlantic (the Newfoundland area). It is based on materials collected on groundfish bottom trawl surveys and on NEREIDA cruises. We describe a new species of Dictyaulus, a genus known for a long time by a single representative from the Indian Ocean, and recently two species from the central Pacific [3] and the north Atlantic [4] were described.

Material and Methods
Material was collected by groundfish bottom trawl surveys by the RV Vizconde de Eza supported by the Instituto Español de Oceanografía and the European Union (methodology used is described in [5]) and from rock dredge samples on board the RV Miguel Oliver sustained by Spain's General Secretariat of the Sea (Secretaría General del Mar) in the framework of the NEREIDA (a multidisciplinary research project). Samples were fixed in 70 ∘ ethanol.
Spicules were dissociated using solution of K 2 Cr 2 O 7 , fresh water, and H 2 SO 4 then washed in fresh, water, and dried. Spicules were mounted in Canada balsam and analysed (including measurements) using light microscopy.
Type materials are stored in the National Museum of Natural Sciences in Madrid (Spain); other specimens are deposited in the Instituto Español de Oceanografía, Vigo (Spain); small fragments and slides for the light microscopy of all investigated specimens are treasured in the P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow (Russia). Description. Three small fragments of 20 × 15 mm, 15 × 10 mm, and 15 × 5 mm were studied.
Remarks. This specimen does not contain any loose spicules; hence its precise identification is impossible, while their morphology is typical for the genus. Nevertheless due to the location of this specimen and data on distribution of representatives of this genus [6], and the name Aphrocallistes beatrix beatrix is assigned with minimal hesitations Figures   The paratype is 265 mm high, 50 mm in diameter, and at base it is broken. Numerous round or oval lateral oscula 0.5-3 mm in diameter penetrate thin 0.5-0.8 mm walls of the specimen. The sieve plate is colander in structure, and it is made of the beams with meshes usually square, sometimes rectangular, or triangular with sides 2-5 mm long. A fine, circular, about 5 mm high structure of small, loose spicules is situated above and around the main osculum of both specimens. No prostasia lateralia was observed in this specimen. Dermalia are hexactins smaller than that described above; they have distal rays lanceolate, lanceolate-pinular, or stout, similar to other rays of these spicules. The distal ray of dermal hexactin is 0.037-0.252 mm long up to 0.03 mm in diameter at the thickest part; tangential rays are 0.104-0.241 mm long, their proximal ray is 0.093-0.525 mm long, the diameter of these rays is 0.004-0.007 mm, and their outer ends are conically pointed, smooth. Atrialia are pentactins with tangential rays 0.200-0.500 mm long, their ray directed inside the body is 0.252-0.444 mm long, the diameter of these rays is 0.004-0.007 mm, and the outer ends are equal to those of dermal hexactins and to small choanosomal spicules. These pentactins are very rarely found, and it is possible that these pentactins are choanosomal spicules (common in many representatives of the subfamily).
Microscleres. Spicules of this type are numerous: drepanocomes, floricomes, pappocomes, large and small discohexasters, and spiny hexactins; discohexactins were unique (found in the holotype only). The drepanocomes with 4-7 secondary rays are 0.059-0.101 mm in diameter, and their primary rosette is 0.014-0.020 mm in diameter. The floricomes have 4-7 secondary rays, each secondary ray has 2-5 teeth, the diameter of the floricomes is 0.072-0.140 mm, and their primary rosette is 0.014-0.030 mm in diameter. The spiny hexactins are 0.133-0.266 mm in diameter. The pappocomes, spicules with secondary rays approximately 11-15 in number, are distributed in slightly widened tufts (as it may be suggested since these spicules were found always broken: secondary rays separated from the primary rosettes); the secondary rays are straight and oxyoidal, rarely onychoidal, curved oxyoidal and rarely spiny. The pappocomes are 0.169-0.333 mm in diameter, and their primary rosette is 0.014-0.026 mm in diameter. The large discohexasters with 2-3 secondary rays are rare, they are 0.072-0.141 mm in diameter, and their primary rosette is 0.014-0.036 mm in diameter. The large discohexasters have anchorate discs with umbel 0.015-0.034 mm long and 0.007-0.016 mm in diameter. The small discohexasters with numerous secondary rays are 0.022-0.065 mm in diameter, and their primary rosette is 0.007-0.020 mm in diameter. Their discs are also anchorate with umbel 0.004-0.007 mm long and 0.002-0.003 mm in 4 Journal of Marine Biology diameter. The large discohexactins were found in the lower part of the holotype specimen, and they are 0.185-0.215 mm in diameter.
Remarks. Until now the genus Dictyaulus comprised 3 species: D. elegans Schulze, 1895 [7] (NW Indian Ocean); D. starmeri Tabachnick and Levi, 2004 [3] (SE Pacific); and D. marecoi Tabachnick and Collins, 2008 [4] (N Mid-Atlantic). Huge discoidal spicules in Dictyaulus are discohexasters in D. elegans, discasters in D. starmeri, and discohexactins in D. romani; in D. marecoi such spicules were not found as well as in the paratype of D. romani, described above. Specific feature of the new species is presence of pappocomes and their derivatives with onychoidal outer ends and secondary rays carrying some spines. As for other spicules the species from the Atlantic Ocean are very similar.

Description
Body Morphology. These sponges are presented by broken fragments of thin walls 0.5-2 mm thick.
Spicules. Choanosomal spicules are diactins. Hypodermalia are smooth pentactins. Hypoatrialia are also pentactins with equal hypodermal ones; they were found only in some specimens in low amounts. Dermalia are pentactins with pinular rays distally directed, a short rudiment instead of the sixth ray has proximal direction, and the outer ray tips are rounded. Atrialia are large hexactins with pinular rays directed into the atrial cavity and pentactins smaller than dermal ones, with thinner rays and conically pointed outer ends, and their pinular rays are directed into the atrial cavity.
Microscleres. Oxyoidal microscleres are common, and they are oxyhexactins, oxyhexasters, and oxyhemihexasters. Discoidal microscleres are represented by spherical microdiscohexasters (found in all specimens) and low amounts of macrodiscasters (found in two specimens). In FC07 L48 a single macrodiscaster 0.089 mm in diameter with primary rosette 0.015 mm in diameter was found. In FC07 L26 we observed two macrodiscohexasters with very short primary rays, and they are 0.118-0.126 mm in diameter with primary rosettes 0.019-0.022 mm in diameter.

Remarks.
A unique feature of the specimens collected off the Newfoundland is rarity of large discoidal microscleres (which were considered to be important in the species identification by [8]). Meanwhile, this is the largest series of representatives of this species, and this unique feature may be an important specific character as well.

Abbreviations
Avg: Average NEREIDA: The project "NAFO" "potEntial vulnerable marine Ecosystems"-Impacts of Deep-seA fisheries IEO: Instituto Español de Oceanografía, Vigo (Spain) MNCN: National Museum of Natural Sciences in Madrid (Spain) n: N u m b e ro fm e a s u r e m e n t s Std: Standard deviation.