Aulosaccus ijimai ( Schulze, 1899 )

Reiswig, Henry M. & Stone, Robert P., 2013, <strong> New glass sponges (Porifera: Hexactinellida) from deep waters of the central Aleutian Islands, Alaska </ strong>, Zootaxa 3628 (1), pp. 1-64 : 33-36

Aulosaccus ijimai ( Schulze, 1899)

( Figs. 16 & 17 , Table 8)

Synonymy. Calycosaccus ijimai, Schulze, 1899: 30 .

Aulosaccus ijimai Ijima 1904: 18 .

Aulosaccus pinularis Okada, 1932: 88 ; Koltun 1967: 75; Stone et al. 2011: 32.

Material examined. USNM# 1196555 , ROV ' Jason II' from RV ' Roger Revelle', dive J2095, 26 July 2004, 25.4 km SSW of Amlia Island, Aleutian Islands , Alaska, 51º48.693'N, 173º49.965'W, 843 m, whole specimen attached to a boulder was collected in pieces, dry & ethanol .

Comparative material examined. Calycosaccus ijimai holotype, USNM 07529 , USFS ' Albatross' , stn 2853, 09 August 1888, SW of Kodiak Is, Alaska, 56˚00'N, 154˚19.5'W, 291 m. Aulosaccus pinularis holotype, USNM 22112 , USFS ' Albatross', stn 4790, 14 June 1906, Bering Sea , 54º39'N, 167º12'W, 117 m.

Description. The specimen encountered in situ ( Fig. 16A ) is a tubular sac flattened on one side at contact with an inclined substrate, with a single large osculum opening opposite the flattened side but subterminal in position. About one half of the body was recovered as a piece 15 cm long by 9.5 cm wide, by 8–13 mm thick. This was subdivided into three smaller 3 x 6 cm subsamples preserved in 95% ethanol and one large dry fragment 14.5 x 6.7 cm ( Fig. 16B ). Both internal and external surfaces are smooth, without prostalia, hyperdermal veil or conules. The oscular margin is sharp, thin and without marginalia. The dermal layer is sturdy and easily detachable from the rest of the body wall; it is supported by clearly visible strands of hypodermal diactins oriented in all directions, forming a subsurface network supporting the dermal spicule rectangular lattice ( Figs. 16C, D ). The dermal lattice has such fine mesh (143 ± 26 µm sides) that it visually obscures the underlying apertures of the subdermal inhalant canals in the dried fragment ( Fig. 16B ). The atrial surface has a more irregular lattice with larger and more irregularly shaped mesh openings. This lattice overlies (covers) the apertures of the exhalant canals, which are generally visible through the atrial lattice ( Figs. 16E, F ). Both dermal and atrial lattices are composed exclusively of pinular hexactins. The main supporting skeleton is a network of loose interwoven unfused diactins, occurring singly or in bundles, oriented without order. Spicule fusion probably occurs only in the basidictyonal skeleton, not collected. Within the moderately firm surface layers, the main parenchyma is cavernous, resulting in a very soft overall body texture. The spacious atrial cavity does not project into the short stalk. Color of the fresh specimen is white; when preserved in ethanol or dried it is light brown.

Megascleres: (spicule dimensions are given in Table 8). Hypodermal pentactins are absent in this species. Dermalia ( Fig. 17A ) are pinular hexactins with moderate bushy pinular ray; the 5 non-pinular rays are all smooth over the proximal half and roughly spined on the distal half. Atrialia ( Fig. 17B ) are all similarly pinular hexactins but all rays are longer and the pinulus is narrower and less bushy than the dermal pinules. Neither pentactins nor stauractins were found as dermalia or atrialia. Hypodermal and parenchymal megascleres are all diactins, including thick principal diactins and thin hypodermal, intermediate and comital diactins. Thick principal diactins are slightly curved, generally smooth, with no medial swelling and rough rounded or parabolic tips (not figured). Thin diactins ( Fig. 17C ) are straight to sinuous, generally smooth with a significant medial swelling and rough parabolic tips.

Microscleres consist of immense discohexasters, also known as solasters, oxyhexasters, oxyhexactins and microdiscohexasters. The subdermal solasters ( Fig. 17D ) have 6 readily detected, swollen but separate primary rays ( Fig. 17E ); the degree of separation seen in these is strongly dependent upon orientation of the visualized spicule. Terminal rays emanating directly from the primary lobes are unequal in length, ornamented with short reclined barbs, and end in marginally toothed discs ( Fig. 17F ). Oxy-tipped microscleres are moderately robust (normal thickness) oxyhexasters ( Fig. 17G ) with 2–3 terminals per primary ray, regular oxyhexactins ( Fig. 17H ), and hemioxyhexasters. They appear smooth in LM but are finely rough in SEM ( Fig. 17I ). Microdiscohexasters ( Fig. 17J ) are common and associated with sub-surface skeletons of both surfaces. They have short, thick, smooth primary rays, each of which supports 6–20 rough crooked terminal rays that end in very small discs with recurved marginal teeth.

Remarks. The main distinctions between Aulosaccus schulzei and A. ijimai are that the former species has pentactin hypodermalia and pentactins as the most abundant dermalia and atrialia while the later has diactins as hypodermalia and pinular hexactins as dermalia and atrialia. They are clearly different species. The Aleutian specimen described here agrees with Schulze's (1899) description of Calycosaccus ijimai (later moved to Aulosaccus ) in all general features, but the dermalia and atrialia are slightly larger, and the microdiscohexasters are slightly smaller than the informal approximate sizes given by Schulze. Significantly, this is only the second specimen of A. ijimai ever reported, and lies 1,360 km WSW of the type location of Schulze's specimen south of Kodiak Island in the Gulf of Alaska. The present report also includes the first and only objective spicule data set and SEM figures of spicules of this species.

The new Aleutian specimen, however, does not differ significantly from the type description of A. pinularis Okada, 1932 from the Commander Islands at the eastern end of the Aleutian chain, nor from Koltun's (1967) description of an additional specimen assigned to that species from Paramushir Island at the tip of the Kamtschaka Peninsula. Okada provided no figures of the type specimen nor of its spiculation. The only data given by both Okada and Koltun are informal typical spicule sizes, like those given by Schulze (1899). In our re-examination of the holotype of A. pinularis , we found the length of the atrialia pinular ray to be 188 ± 30 (95–249, n = 62) µm, completely outside the range of 260–300 µm given by Okada and parroted by Koltun. For comparison, we obtained new data for the same measurement from Schulze's type specimen of C. ijimai to be 152 ± 37 (79–269, n = 100) µm, slightly smaller in mean length than Okada's specimen, but covering a similar range. The major difference between the two species descriptions is the degree of pinularity of the surface hexactins, a subjective evaluation made by the two different original authors that is difficult to accept as significant. Our re-examinations of the type material have convinced us that these are both the same species and A. pinularis Okada is here moved to junior synonym of A. ijimai Schulze.

Review of all video footage collected with the ROV 'Jason II' indicates that this is a rare species occurring singly on bedrock, mudstone, and boulders at depths between 843 and 1715 m.

µm unless otherwise indicated).

Genus Bathydorus Schulze

Type species: Bathydorus fimbriatus Schulze, 1886

Figures

FIGURE 16. Aulosaccus ijimai (Schulze), body and surfaces. A. An in situ image of the collected specimen. B. Two sides (both dermal) of the largest dry fragment. C. Close-up of the dermal surface showing thick hypodermal strands supporting the loose spicule lattice. D. Closer view of the mounted dermal spicule lattice and supporting hypodermal diactin bundles. E. Close-up of the atrial surface showing the irregular atrial lattice overlying apertures of the exhalent canals. F. Closer view of the atrial hexactin lattice.

FIGURE 17. Spicules of Aulosaccus ijimai (Schulze) from the Aleutian Islands (SEM). A. Dermal pinular hexactins and enlarged ray ends. B. Atrial pinular hexactin. C. Thin diactin, whole and enlarged ends and middle segment. D. Solaster (discohexaster), whole. E. Two centra of solasters in different orientations (LM). F. Terminal ray ends of solaster. G. Oxyhexaster. H. Oxyhexactin. I. enlarged ray end of oxyhexactin. J. Microdiscohexaster.