Aphrocallistes beatrix Gray, 1858

Lopes, Daniela A., Hajdu, Eduardo & Reiswig, Henry M., 2005, Redescription of two Hexactinosida (Porifera, Hexactinellida) from the southwestern Atlantic, collected by Programme REVIZEE, Zootaxa 1066, pp. 43-56 : 45-49

Aphrocallistes beatrix Gray, 1858

( Figs. 2–3, Tab I)

Material examined. MNRJ 3111, off Espírito Santo State, (19.296 º S – 37.954 º W), Central II cruise, station 20 c, 500m depth, coll. R.V. “Astro Garoupa”, 22 /xi/ 1997; MNRJ 8534, off Rio de Janeiro State, (24.365 º S – 43.602 º W), RJ II cruise, station 9, 640m depth, coll. R.V. “Diadorim”, 24 /vii/ 2004.

Comparative material. Aphrocallistes vastus Schulze, 1886 ­ MNRJ 1932, Jervis Inlet, British Columbia, Canada, 30 m, coll./det./leg. M. LeBlanc. MNRJ 3445, 5.5km N of Elden Hood Canal, Washington, det./leg. G.J. Bakus (# 379, Allan Hancock Foundation, University of Southern California). MNRJ 7185, off Kiwash Island (51 º 51.8 ´N ­ 128 º 53.6 ´W), Fitzhugh Sound, British Columbia, Canada, 27m, coll./det. H.M. Reiswig (RMM­I 3708).

Diagnosis. Aphrocallistes with a branching­tubular to funnel shaped body form with cylindrical diverticula, a thin wall 0.5–3mm thick, dictyonal framework of closely spaced diarhyses separated by thin septa and tuberculated beams. Dermalia are pinular hexactins and dermal scopules in three forms. Atrialia are tuberculate diactins and parenchymal hexactins. Microscleres are diverse.

Description. Body consists of sparsely branching and sometimes anastomosing tubes, without an axial funnel or a funnel bearing lateral tubular diverticula (5­9.6 ­ 12mm in diameter); thin wall (0.5­1.6 ­ 3mm thick; Fig. 2 A); rigid transverse sieve plate may subdivide the atrial lumen ( Fig. 2 B).

Skeleton. Dictyonal framework of closely spaced diarhyses (570 ­765.0­ 1100 m in diameter), separated by thin septa (35­95.1 ­ 260 m thick), resulting in a regular hexagonal honeycomb aspect ( Fig. 2 C –D); beams are tuberculate ( Fig 2 C­E).

Spicules (Table I). Dermalia include pinular hexactins with narrow, thorned pinulus with tuberculate paratangential and proximal rays ( Fig. 2 F); dermal scopules in three forms: (a) thick scopules with 3–7 tines ending in strongylote or button tips ( Fig 2 G); (b) thin scopule with 3–6 tines ending in disc or tylote tips ( Fig. 2 H); (c) thin scopules with tines ending in pointed tips; uncinates in two forms ( Fig. 3 D): (a) large and moderately thick, frequently with few barbs ( Fig. 2 I); (b) small and very thin, often unbarbed. Atrialia includes slightly curved diactins, heavily spined or tuberculate, bearing four central knobs ( Fig. 2 J­K, 3 E); parenchymal hexactins entirely spined ( Fig. 2 L); hexactins may rarely have only a rudiment of the sixth ray. Microscleres include hemihexasters in oxy­tipped (hemioxyhexaster; Fig. 2 M) and disco­tipped forms (hemidiscohexaster; Fig. 2 N), discohexasters and oxyhexasters ( Fig. 2 O­Q).

Distribution and ecology. Aphrocallistes beatrix is mainly northern­cosmopolitan in distribution, with only two records south of 15 ºS, and ranges in depth from 60 to 2949m. This is the first record from the southern Atlantic. Specimen MNRJ 3111 was collected on an area with prevailing muddy carbonatic sand. Specimen MNRJ 8534 is associated with zoanthids ( Fig. 2 A).

Remarks. The genus Aphrocallistes contains only two recognized species, A. beatrix and A. vastus Schulze, 1886 , which are sympatric around Japan. Aphrocallistes beatrix is presently understood to include A. beatrix beatrix , with synonyms A. bocagei Wright, 1870 , A. ramosus Schulze, 1886 and A. jejuensis Sim & Kim, 1988 , and A. beatrix orientalis Ijima, 1916 , as a distinct subspecies ( Reiswig, 2002 a). Aphrocallistes vastus can be clearly set apart by gross morphological features such as its cup­shape and thicker walls (ca. 5 mm; Schulze, 1887).

Ijima (1916) argued for the recognition of A. beatrix orientalis , which appeared to him to be restricted in occurrence to Japan, the China Sea and the Philippine Islands. The typical subspecies, A. beatrix beatrix was widely distributed in all three major oceans. Six main morphological characters were listed by Ijima (1916) in support of his proposition, viz., (1) slender body tubes (4–8mm in diameter), body wall (less than 1mm thick) and diarhyses (0.6–0.8mm across); (2) tridimensional arrangement of dictyonal septa; (3) tubercles on the surface of dictyonal septa only occasionally present; (4) dermalia largely pentactine, the hexactins show variably developed pinular rays which frequently bear only a rudimentary development of spines; (5) scopules with terminal swellings which are never in the form of a convex­disk with a marginal whorl of spines; and (6) elongate forms of hemihexasters smaller than 100 m in length.

The Brazilian material studied here somewhat bridges the gap perceived by Ijima (1916) in recognizing A. beatrix orientalis . From the proposed distinguishing features enumerated above, the Brazilian specimens bear similarly slender diarhyses, scopules without terminal disks and hemihexasters smaller than 100 m in length. The main distinguishing feature which remains, suggesting the Brazilian material to be best assigned to A. beatrix beatrix is their possession of fully formed dermal pinular hexactins which do not grade into pentactins. The validity of Ijima’s propositions cannot be evaluated on the basis of material at our disposal, and given the apparent morphological plasticity of both purported subspecies (e.g. Schulze, 1904; Ijima, 1916), it appears that a molecular study would be more appropriate to establish the limits of A. beatrix .

TABLE I: Spicule dimensions of Aphrocallistes beatrix Gray, 1858. Measures are expressed in μm as: smaller­ mean­largerN. Ln = Length, Wd = width, Diam = diameter.

Figures

FIGURE 3: Spicules of Aphrocallistes beatrix Gray, 1858. A. dermal pinule. B. parenchymal hexactin. C. variety of scopules. D. uncinates. E. diactins. F. hemihexasters. G. discohexasters. H. oxyhexaster (Scale bars: A = 50 μm, B, F = 20 μm, C­E = 100 μm, G­H = 10 μm).