AETEOIDEA Smitt, 1868

Dick, Matthew H. & Grischenko, Andrei V., 2016, Rocky-intertidal cheilostome bryozoans from the vicinity of the Sesoko Biological Station, west-central Okinawa, Japan, Journal of Natural History 51 (3 - 4), pp. 141-266 : 152-156

Superfamily AETEOIDEA Smitt, 1868

Family AETEIDAE Smitt, 1868

Genus Aetea Lamouroux, 1812

Aetea sp. A

( Figure 3 (a))

? ‘ Aetea ? australis Jullien’: Gordon 1984, p. 39, pl. 8A–D.

Material examined

NSMT-Te 1503 ( MIN- 1), dried, on SEM stub.

Measurements

Running stolon diameter, 0.018 –0.030 (0.024 ± 0.005) (n = 6, 1). Stolon dilatation length 0.26; width, 0.10 (average values, n = 2). Length of erect part of zooid (including circular stalk and expanded ‘hood’), 0.43–0.78 (0.619 ± 0.140); stalk length, 0.25–0.54 (0.376 ± 0.103); hood length, 0.19–0.28 (0.241 ± 0.036); ratio, length of hood to total length of erect part of zooid, 0.33–0.44 (0.396 ± 0.042) (all n = 7, 1). Stalk diameter, 0.055 –0.072 (0.065 ± 0.005); maximum width of hood, 0.064 –0.104 (0.090 ± 0.014); ratio, maximum width of hood to stalk diameter, 1.00–1.58 (1.398 ± 0.184) (all n = 8, 1).

Description

Colony small, recumbent, with zooids in branching uniserial series. Recumbent part of zooids consists of long, thin proximal stolon and wider, oblong distal dilatation. Dilatation width roughly 3 times that of stolon. Basic branching pattern cruciform; dilatation can be terminal, or give rise to stolon of daughter zooid from distal end, and/or from lateral margin on one or both sides. Erect part of zooid arises from distal end of dilatation and consists of tubular stalk and expanded hood open on one side (where frontal membrane covers opesia) and distally (where aperture is closed by operculum). Stalk relatively thick; diameter more than half width of dilatation. Hood relatively long, comprising roughly 30–40% of length of erect part of zooid. Hood widest in mid-region; transversely or slightly obliquely truncate distally. Opesia tapering proximally, forming V-shaped notch where hood meets stalk. Operculum terminal, fitting transverse curvature of distal end of hood. Stolon, dilatation, stalk and hood appear smooth, with no overt, regular annulation.

Remarks

The taxonomy of Aetea is poorly resolved. Species in this genus have a simple, rather stereotypical morphology, and some of the characters perceived to be taxonomically informative unfortunately appear to vary ecophenotypically, as Gordon (1984, p. 39) noted for parts of a single colony of Aetea cf. ligulata growing in different microhabitats. At least part of the material from the Kermadec Ridge, New Zealand, that Gordon (1984) reported as Aetea ? australis Jullien, 1888, is similar to our specimen in the following characters: the branching pattern appears to be cruciform; the dilatation is markedly wider than the stolon; the erect tubular stalk is thick, roughly half or more as wide as the dilatation; the hood is transversely or slightly obliquely truncate, and comprises nearly half the total length of the erect portion in some zooids; and there are no regular annuli on any part of the zooid.

Occurrence

We found one colony, at the MIN site.

Suborder THALAMOPORELLINA Ostrovsky, 2013 Superfamily THALAMOPORELLOIDEA Levinsen, 1902 Family THALAMOPORELLIDAE Levinsen, 1909

Genus Thalamoporella Hincks, 1887

Thalamoporella stapifera ( Levinsen, 1909)

( Figures 3 (b–f) and 4(f))

Thalamoporella granulata var. A ( stapifera ) Levinsen, 1909, p. 188, pl. 6, fig. 5(a–e).

Thalamoporella stapifera: Harmer 1926, p. 297 , pl. 19, figs 17 and 20–25. Winston and Heimberg 1986, p. 8, figs 13–16.

Not Thalamoporella stapifera: Ryland and Hayward 1992, p. 241 , fig. 10(d, e).

Not Thalamoporella stapifera: Soule and Soule 1970, p. 10 , fig. 4(c–g). Soule et al. 1992, p. 13, 31, figs 21 and 47; [= Thalamoporella molokaiensis Soule et al., 1999 ].

Material examined

NSMT-Te 1054 (MIN-Thal1), bleached, on SEM stub; NSMT-Te 1055 (MIN-Thal2), bleached, on SEM stub; NSMT-Te 1056 ( MIN- 15), bleached, on SEM stub; NSMT-Te 1057, four dried specimens, MIN site; NSMT-Te 1058, 22 dried specimens, REEF site; NSMT-Te 1059, four bleached fragments, REEF site; NHMUK 2016.5.13.1-6, six dried specimens, REEF site.

Measurements

AzL, 0.68–0.96 (0.807 ± 0.076); AzW, 0.36–0.58 (0.458 ± 0.050) (n = 43,3). OrL, 0.20– 0.27 (0.235 ± 0.017); OrW, 0.19–0.25 (0.226 ± 0.014) (n = 43, 3). OvL, 0.50–0.60 (0.549 ± 0.034); OvW, 0.59–0.70 (0.644 ± 0.029) (n = 8, 3). AvL, 0.56–0.61 (0.585 ± 0.017); AvW, 0.34–0.38 (0.358 ± 0.014) (n = 6, 3). Stirrup-shaped calliper: H, 0.048 –0.061 (0.055 ± 0.003); W, 0.041 –0.050 (0.044 ± 0.002); H/W ratio, 1.13–1.38 (1.251 ± 0.074) (n = 17, 1). C-shaped calliper: H, 0.031; W, 0.036; H/W 0.086 (n = 1, 1). Compass length, 0.053 –0.165 (0.085 ± 0.022) (n = 40, 1). Largest colony observed 20 × 13 mm.

Description

Colony forming a unilaminar, encrusting sheet, becoming locally multilaminar due to selfovergrowth; light yellowish to greyish tan in colour; often irregular in outline. Zooids ( Figure 3 (b–d)) distinct. Cryptocyst flat, densely granulated, uniformly perforated with small pseudopores proximal to level of opesiules; completely surrounded by raised, beaded rim. Opesiules oval, elongate, subcircular or irregular in outline; symmetrical in size, or one larger than other. Opesiular insertions ( Figure 3 (e)) irregular open hooks, though distal end sometimes extends laterally to meet lateral wall, giving closed hook. Orifice ( Figure 3 (b, c)) subcircular, approximately as long as broad; semicircular distal to articulations; broad, deep sinus proximal to articulations, proximal margin concave or straight. Small, paired knobs present or absent lateral to orifice, this character variable even within colonies. Avicularia ( Figure 3 (b, c)) shorter than autozooids; ratio of mean AvL to mean ZL, 0.72; middle flanges lacking; articulations small, bracket-like. Mandibular part of rostrum raised, with smooth gymnocystal surface; mandible tapering to rounded, sub-acute tip. No torsion evident among avicularium, sister zooid or other adjacent zooids. Large ooecium of bivalved hyperstomial ovicell ( Figure 3 (b, d)) somewhat broader than long, with median suture and acute, lanceolate opening. Spicules ( Figure 3 (f)) comprise small stirrup-shaped callipers and small to medium, slightly angled compasses; one small, C-shaped calliper observed. Zooids interconnect ( Figure 4 (f)) via broad line of single pores near base of transverse wall and two small, raised pauciporous septula in each lateral wall.

Remarks

Our material is consistent in virtually all characters with the redescription of T. stapifera by Soule et al. (1999). We found inter-colony variation in the occurrence of the stirrupshaped callipers; among three colonies examined, callipers were abundant in one, rare in another and not detected in the third. There was also considerable variation in zooid and orifice size, so much so that it appeared two distinct species were involved; however, in some specimens, a part of the colony having small zooids could be traced to another part of the same colony having large zooids. This size variation may be related to seasonal variation in water temperature.

Occurrence

This species was abundant at REEF and common at MIN ( Table 1). It is distributed from the north-eastern Indian Ocean to the western Pacific. Originally described from the Andaman or Nicobar islands ( Levinsen 1909), T. stapifera has been reported from Timor ( Harmer 1926); Lombok, Indonesia ( Winston and Heimberg 1986); and the South China Sea ( Androsova 1963). Okinawa (~ 26°N) is the farthest northern record.