Parasmittina alanbanneri Soule and Soule, 1973

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 : 194-196

Parasmittina alanbanneri Soule and Soule, 1973

( Figure 17)

Parasmittina alanbanneri Soule and Soule, 1973, p. 385 , fig. 3(a–c).

Material examined

NSMT-Te 1103 ( MIN- 12), bleached, on SEM stub (with Bryopesanser latesco ); NSMT-Te 1104 ( MIN- 17), bleached, on SEM stub; NSMT-Te 1105 (REEF-7), bleached, on SEM stub; NSMT-Te 1106, dried specimen, MIN site; NSMT-Te 1107, dried specimen, REEF site.

Measurements

AzL, 0.33–0.46 (0.397 ± 0.038); AzW, 0.21–0.35 (0.279 ± 0.038) (n = 15, 2). SecOrL (including sinus), 0.09–0.12 (0.102 ± 0.008); SecOrW, 0.09–0.11 (0.099 ± 0.005) (n = 15, 2). OvL, 0.17–0.20 (0.183 ± 0.010); OvW, 0.17–0.22 (0.191 ± 0.014) (n = 11, 2). Longest AvRosL per zooid, 0.06–0.11 (0.081 ± 0.014) (n = 16, 2). Largest colony observed 9 mm across.

Description

Colony forming an irregular, unilaminar, encrusting sheet; light tan in colour. Zooids ( Figure 17 (a, c, d)) distinct, boundaries indicated by opposing columns of areolae and suture line. Frontal wall convex, tuberculate, rugose; five to seven small areolae along each lateral margin. Primary orifice with very broad, low, alate lyrula ( Figure 17 (b)). Condyles blunt, with minute denticles at tip; angled proximomedially, nearly meeting lyrula and forming a small, oval notch on each side. Main part of secondary orifice subtrapezoidal in shape, lateral margins tapering towards secondary peristomial sinus; sinus deep, U-shaped, conspicuous; peristomial rim often with a projection on each side lateral to sinus; distal margin of secondary orifice gently curved, with 13 to 16 minute, sharp, evenly spaced denticles. Three oral spines ( Figure 17 (a, b, d)) close to distal margin of secondary orifice. Zooids have one (39%), two (61%) or three (2%) frontal avicularia (n = 38, 1). If paired, the avicularia are proximolateral or lateral to orifice, directed proximolaterally or laterally, occasionally slightly distolaterally, but often differing from one another in the angle from the midline; if single, avicularium is proximolateral to orifice and directed proximolaterally, or close to midline, pointing proximally or slightly proximolaterally. Rostrum slightly raised from frontal plane, not tilted laterally; rostral plane slightly decurved; rostral edges smooth; crossbar typically complete; mandible long-triangular, acute. In one colony, some zooids have a hypertrophied avicularium proximolateral to orifice ( Figure 17 (d)), up to twice the length of the smaller avicularia. A small pseudopore is occasionally present to one side or other of an avicularium. Ovicell ( Figure 17 (c)) hyperstomial; peristome extends across proximal quarter to third of ooecium, forming a raised, thick semicircular band, often with a heavy tubercle on each side. Ectooecium smooth, with about 20 conspicuous pseudopores over entire area distal to peristome. Proximal edge of ooecium visible within peristome, usually serrate. Ancestrula not observed.

Remarks

Our specimens show the following characters indicated in the original description of P . alanbanneri from Hawaii ( Soule and Soule 1973): small zooid size (average zooid size 0.40 × 0.28 mm, compared to 0.41 × 0.31 mm in Hawaiian material); rugose frontal wall; small marginal pores; a low, very broad, alate lyrula; small, single or paired frontal avicularia close to the orifice, with an acute, long-triangular mandible; the avicularian rostrum scarcely elevated from the frontal surface, not tilted and with smooth edges; and scattered pseudopores over the entire surface of the ooecium . Differences are as follows . In Hawaiian P . alanbanneri, the avicularia are typically situated lateral to the orifice, with the rostrum directed laterally or nearly so. In our specimens, while some paired avicularia are situated and oriented in this manner, most are proximolateral to the orifice and directed proximolaterally; when they are single, avicularia are often positioned near the midline proximal to the orifice and point proximally or nearly so . Zooids in Hawaiian P . alanbanneri have three to six spines, whereas those in our specimens have invariably three; however, many of the zooids in SEM images in Soule and Soule (1973) have three spines, which may be the modal number in Hawaii. Finally , there was no indication that the distal orificial margin is denticulate in Hawaiian P . alanbanneri, although this character might easily have been overlooked in the low-quality SEM images accompanying the original description.

Occurrence

We found a total of five colonies, at the REEF and MIN sites. Parasmittina alanbanneri was previously known only from the Hawaiian archipelago (Oahu, Molokai, and Hawaii islands) ( Soule and Soule 1973).