Apiophragma hyalina ( Waters, 1904 )

Gordon, Dennis P. & Taylor, Paul D., 2017, Resolving the status of Pyriporoides and Daisyella (Bryozoa: Cheilostomata), with the systematics of some additional taxa of Calloporoidea having an ooecial heterozooid, Zootaxa 4242 (2), pp. 201-232 : 223-225

Apiophragma hyalina ( Waters, 1904)

( Fig. 14 )

Megapora hyalina Waters, 1904: 39 , text-fig. 1, pl. 2, figs 13a, b.

Apiophragma hyalina: Hayward & Ryland 1993: 120 , fig. 1; Hayward 1995: 154, fig. 120E, F.

Material examined. NIWA 23005 , NIC Wellington, Stn TAN 0402 /73, 72.0613° S, 173.2455° E – 72.0647° S, 173.2632° E, 620–622 m, NW Ross Sea off Cape Adare, Antarctica, 13 February 2004.

Redescription. Colony encrusting, small, spot-like, maximum spread up to 4.5 mm. Autozooids arranged contiguously in quincunx, communicating via basal pore-chambers, of which two lateral pairs and one mid-distal are visible in zooids at colony margin [ZL400–661 (561); ZW 343–544 (468)]. Gymnocyst continuous around zooid, narrow to moderately well developed. Cryptocyst and opesia surrounded by a distinct pyriform rim constricted at level of proximalmost oral spines [CrL 298–412 (360); CrW 239–350 (317)]. Cryptocystal shelf extensive, flat, with a pair of suboval opesiules. Opesia generally a little wider than long, distal margin rounded and tubercular, straight proximally, constricted in proximal third; articular surface smooth, rounded, operculum occupying c. three-quarters of opesial length [OpL 110–145 (122)]. Six articulated spines, perioral only, all of which are retained in ovicellate zooids, arranged in arc around operculum; 0–2 additional tiny spines on each lateral gymnocyst. No avicularia. Ooecium hyperstomial, acleithral, smooth with longitudinal carina in proximal half, carina occupied by elongate slit or smaller excavation [OoL 217–232 (226); OoW 233–245 (239)]. Ooecial kenozooid protruding a little distally, with small opesial foramen surrounded by semicircular cryptocyst, subgranular to smooth, flanked by pair of smaller pore-chambers. Ancestrula resembling later zooids but with slightly longer opesia and nine pericryptocystal spines [AnL 335–431 (383); AnW 223–305 (264)].

Remarks. Waters (1904) did not describe the ooecium, which meant that his illustration of it was ambiguousis the longitudinal feature on the front a carina or an excavation? This question could not be answered by Hayward & Ryland (1993) as their material was infertile. In the event, it is now seen to be both, viz a carina in which there is an elongate slit or shorter excavation. On the other hand, Waters described and illustrated the tiny gymnocystal spines that were not remarked upon by Hayward & Ryland. Hayward (1995) showed a presumed ancestrula but it had only six oral spines; it is clear from the larger, original SEM photograph in Hayward & Ryland (1993, fig. 1A) [from which figure 120E in Hayward (1995) was cropped] that this was not the actual ancestrula but a daughter zooid.

None of these authors mentioned the ooecial kenozooid in A. hyalina , which is a character also exhibited by Pyriporoides, Olisthella n. gen., Bryobrownius n. gen. and Megapora , suggesting that all of these genera could be phylogenetically related. Waters (1904) and Hayward & Ryland (1993) neglected to suggest a family for A. hyalina , but Waters’ inclusion of the species in Megapora shows that he regarded it as ‘membraniporine’. Hayward (1995) included it in Microporidae , no doubt on the basis of the cryptocystal opesiules. Significantly, Hayward & Ryland (1993) coined the name Apiophragma from “ apios (Gr.), a pear, and phragma (Gr.), a wall, referring to the shape of the mural rim,” which is one of the diagnostic characters of Pyrisinellidae ( Di Martino & Taylor 2012) . Interestingly, one autozooid in the present material shows a very thin suture line from each opesiule to the opesia. Such a line is to be expected to result developmentally as the cryptocyst calcifies around each opesiular locus (insertion of a parietal muscle), but it may also be indicative of origination of Apiophragma from an ancestor having a larger opesia and lacking opesiules.

Distribution. Antarctica (Ross Sea, Bellingshausen Sea, South Shetland Islands) from 60° to 72° S at 436–622 m depth on pebbles and dead stylasterid hydrocoral.

Figures

FIGURE 14. Apiophragma hyalina (Waters, 1904), NIWA 23005: A, Opesiulate autozooid, with arrows indicating tiny gymnocystal spines; B, close-up of opesia; C, ovicellate zooid with operculum in place (white arrow indicates foramen of narrow exposure of ooecial kenozooid, small black arrows indicate gymnocystal spines); D, close-up of opesia of ovicellate zooid and foraminal slit in proximofrontal fissure. Scalebars: A, C, 200 µm; B, 100 µm; D, 100 µm.