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A New North Pacific Heterochone Transferred from Aphrocallistes (Porifera: Hexactinellida).

Abstract.--A hexactinellid sponge specimen from southern California, determined as a member of the genus Heterochone, was found to be conspecific with Aphrocallistes beatrix incognitus, a form previously described from the Okhotsk Sea by Koltun (1967). The taxon is redescribed and reassigned as a new combination, Heterochone incognitus (Koltun). It represents an addition to the North American Pacific fauna. The simple zoological diagnosis of Heterochone is: Aphrocallistidae with atrialia as pinular hexactins.

The deep-water marine fauna of the Pacific Coast of North America is poorly known primarily owing to avoidance of the region by the major oceanographic expeditions of the late 1900's. During an ongoing survey of California collections by myself and coworkers, with the aim of producing an updated guide to the Porifera of California, we encountered a hexactinellid sponge from southern California unknown to the region (last summarized by de Laubenfels 1932). The specimen is the third and, although imperfect, the best preserved specimen of a species known to date as Aphrocallistes beatrix incognitus; it has been recorded only from the Okhotsk Sea, eastern Russia (Koltun 1967). The severely damaged condition of the earlier specimens is likely cause for the original incorrect generic assignment, which is here resolved and corrected.

Materials and Methods

The specimen was obtained on loan from the Benthic Invertebrate Collection of Scripps Institute of Oceanography, La Jolla, California (SIO). After photographing the specimen, small pieces of dermal and atrial surfaces were wholemounted in Canada balsam for light microscopy and digested in hot nitric acid for spicule cleaning. Cleaned spicules were either mounted directly in balsam on slides or retained on nitrocellulose filters which were cleared and mounted on slides. Spicules and body apertures were measured by microscope-coupled digitizer. Spicule drawings were made directly from video-captured images. Data in text are given as: minimum-mean-maximum of 25 measurements.

Systematics

Class Hexactinellida Schmidt, 1870

Subclass Hexasterophora Schulze, 1886

Order Hexactinosa Schrammen, 1903

Family Aphrocallistidae Gray, 1867

Genus Heterochone Ijima, 1927

Diagnosis.-Aphrocallistidae with atrialia as pinular hexactins.

Type species.--Chonelasma calyx Schulze, 1886

Remarks.--Upon his erection of Heterochone, Ijima (1927) provided an extensive comparison of the new genus with its only sister genus, Aphrocallistes, but did not provide a diagnosis. Reid (1963), aware of Ijima's action, characterized the genus by body form, a strategy perhaps necessary for paleontological use but insufficient for zoological application. Koltun (1967) was apparently unaware of Ijima's formation of Heterochone, perhaps because it was mistakenly omitted from the final list of Ijima's (1927) publication (Reiswig 1990). The short, new diagnosis provided here differentiates Heterochone (with hexactine atrialia) from Aphrocallistes (with diactine atrialia).

Heterochone incognitus (Koltun, 1967)

Figs. 1-2, Table 1.

Synonymy.--Aphrocallistes beatrix incognitus Kotun, 1967: 60, Fig. 39.

Holotype.--Zoological Institute, Russian Academy of Science (Leningrad) N 16362 (2 fragments), 148[degrees]57'E, 44[degrees]41'N, 780m, RV 'Vitiaz' stn. 5640 (not examined).

Material examined.--SIO P 592, in alcohol, 118[degrees]53.6'W, 33[degrees]20.4'N. 1165-958 m depth, 11 Dec. 1971, RV 'Thomas Washington', col. Mathews.

Body and framework.--Specimen a massive irregular fragment, 13.4 cm X 6.9 cm X 4.0 cm, as part of basal region without attachment site; dead skeletal frame-work on presumed lower side; 2 major depressions interpreted as bases of mostly missing funnel-form body extensions on opposite presumed upper side (Fig. 1A); surface even and compacted but edge of upper funnel with small region of intact body wall (Fig. 1A, arrows); wall 1 cm thick penetrated by radial diarhyses (skeletal channels of dictyonal framework) passing from dermal to atrial surface; dermal surface entirely covered by rectangular lattice of loose pinular hexactins of 149-183-235 [micro]m mesh (Fig. 1B); dermal openings of diarhyses 0.44-1.07-1.88 mm diameter and irregulary distributed; atrial surface lined by compact felt of pinular hexactins not forming a rectangular lattice; atrial apertures of diarhyses 0.27-0.94-1.74 mm diameter, irregularly distributed, uncovered and open (Fig. 1C); dictyonal framework typically aphrocallistid (with diarhys es) with beams partly smooth and partly sparsly spined, 49-88-188 [micro]m in thickness; meshes 3- and 4-sided, very irregular with sides 183-483-1059 [micro]m.

Spicules.--Spicule form and dimensions are summarized in Fig. 2 and Table 1. Megascleres: Dermal and atrial pinular hexactins (Fig. 2A-B) are similar but proximal rays of dermal forms have greater length range; parenchymal hexactins occur in larger coarsly spined form (Fig. 2D) and smaller moderately spined form (Fig. 2C); scopules with micro-thorned tines occur in 2 forms in both surfaces: form with 4 tines and small (10[degrees]) angular spread (Fig. 2F), and form with 6-8 tines more widely (30[degrees]) divergent (Fig. 2G); large uncinates (Fig. 2E) are of form typical of the family.

Microscleres: Oxyhexactins (Fig. 2H) to hemioxyhexasters (Fig. 2I) with smooth primary rays and micro-rough secondary rays numbering 1-4, often with branching retricted to one axis; discohexaster (or tylohexasters) with short smooth primary rays, each bearing 5 rough secondary rays terminating in a small cap with 4-6 marginal spines (Fig. 2J).

Remarks.--The specimen, SIO P 592, agrees in spiculation with that described by Koltun (1967) as Aphrocallistes beatrix incognitus (Table 1; Koltun 1967, Fig. 39). Koltun's material consisted of 2 small, damaged pieces of sponge, ca. 2.5 X 1.5 cm, plus numerous fragments of washed-out skeletal framework collected from the Okhotsk Sea. He was able to describe and measure dermal and parenchymal spicules but atrial surfaces were too damaged to enable determination of associated spicules critical to generic placement. Surprisingly he made no statements on framework structure or channelization, features which were available for assessment and critical for family assignment. His placement of the Okhotsk material was presumably influenced by the distinctive "roller-form" of the hemihexasters, a well known feature of Aphrocallistes beatrix, and compromised by the unavailability of atrial spicules and his lack of awareness of Ijima's Heterochone. With availability of the atrial surface in the southern California spec imen, and conclusion that the specimen is conspecific with the Okhotsk material, Kotun's specimens can now be correctly reassigned as the new combination, Heterochone incognitus Koltun. The new form is easily differentiated from other Heterochone species: H. calyx Schulze has shorter inflated pinulus and spheric oxyhexasters; H. hamata Schulze has no oxyhexasters; H. tenera Schulze has microsclere populations that are mainly discohexactins.

Acknowledgments

I thank Spencer Luke and Larry Lovell for making loan material available for this study, and Prof. V.M. Kotun for providing holotype collection data. Financial support was provided by the Natural Sciences and Engineering Research Council of Canada.

Literature Cited

Ijima, I. 1927. The Hexactinellida of the Siboga Expedition. Siboga Exped. Rept. 6:1-383.

Koltun, V.M. 1967. Vitreous sponges of the Northern and Far-Eastern Seas of the USSR. [in Russian] Opred. Faune S.S.S.R. 94:1-124.

Laubenfels, M.W. de 1932. Marine and fresh water sponges of California. Proc. U.S. Nat. Mus. 81:1-140.

Reid, R.E.H. 1963. Notes on a classification of the Hexactinosa. J. Paleont. 37:218-231.

Reiswig, H.M. 1990. Correction of Ijima's (1927) list of recent hexactinellid sponges (Porifera). Proc. Biol. Soc. Wash. 103:731-745.

Schulze, F.E. 1886. Uber den Bau und das System der Hexactinelliden. Abh. Konigl. Akad. Wiss. Berlin (Physik.-Math.) 1886:1-97.

Accepted for publication 22 December 2000.
Table 1.
Spicule measurements of Heterochone incognitus, SIO P 592 with
comparison data from Okhotsk Sea specimens of Koltun, 1967.
Item measured Mean [+ or -] s.d. Range
Dermal pinule A
 pinulus length ([micro]m) 15 [+ or -] 24 88-222
 tangential ray length ([micro]m) 156 [+ or -] 22 104-227
 proximal ray length ([micro]m) 304 [+ or -] 155 68-728
Gastral pinule B
 pinulus length ([micro]m) 198 [+ or -] 47 85-280
 tangential ray length ([micro]m) 170 [+ or -] 37 104-247
 proximal ray length ([micro]m) 135 [+ or -] 33 65-193
Scopule F length ([micro]m) 606 [+ or -] 84 420-756
Scopule G length ([micro]m) 537 [+ or -] 103 369-751
Hexactin D ray length ([micro]m) 216 [+ or -] 47 146-341
Hexactin C ray length ([micro]m) 172 [+ or -] 41 100-278
Uncinate length (mm) 5.4 [+ or -] 0.9 3.6-7.1
 width ([micro]m) 24 [+ or -] 5 12-35
Oxyhexactin diameter ([micro]m) 92 [+ or -] 16 64-126
Hemioxyhexaster diameter ([micro]m) 100 [+ or -] 19 65-129
Discohexaster diameter ([micro]m) 28.8 [+ or -] 5.8 21.2-44.3
Item measured N Koltun, 1967
Dermal pinule A
 pinulus length ([micro]m) 100 120-165
 tangential ray length ([micro]m) 100 99-154
 proximal ray length ([micro]m) 100 159-264
Gastral pinule B
 pinulus length ([micro]m) 25 n.r.
 tangential ray length ([micro]m) 25 n.r.
 proximal ray length ([micro]m) 25 n.r.
Scopule F length ([micro]m) 25 412-660 [*]
Scopule G length ([micro]m) 25 412-660 [*]
Hexactin D ray length ([micro]m) 25 n.r.
Hexactin C ray length ([micro]m) 25 n.r.
Uncinate length (mm) 22 1.0-4.0
 width ([micro]m) 50 13-32
Oxyhexactin diameter ([micro]m) 25 66-121
Hemioxyhexaster diameter ([micro]m) 25 n.m.
Discohexaster diameter ([micro]m) 25 38
(*)Scouple types not measured separately
n.r. = not reported
n.m. = not measured
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Author:Reiswig, Henry M.
Publication:Bulletin (Southern California Academy of Sciences)
Geographic Code:1U9CA
Date:Aug 1, 2001
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