Actisecos regularis Canu & Bassler, 1927

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 65-67

Actisecos regularis Canu & Bassler, 1927

( Fig. 27 , Table 26)

Actisecos regularis: Canu & Bassler 1927 , p. 11, pl. 1, fig. 13; Canu & Bassler 1929, p. 517, pl. 66, figs 1–4; Harmer 1957, p. 856‒857, pl. 60, figs 12, 16.

Material examined. Lectotype: USNM 8325 . Philippines, Linapacan Strait, Observatory Island, 11° 37´15´´ N, 119° 48´45´´ E, Albatross Station D. 5335, depth 46 fathoms, 18 December 1908 . Paralectotypes: USNM 545928 . Philippines, Linapacan Strait, Observatory Island, 11° 37´45´´ N, 119° 46´E, Albatross Station D. 5336, depth 46 fathoms, 18 December 1908 . USNM 545929 . Tacbuc Point, Leyte Island, 10° 46´24´´ N, 125° 16´30´´ E, Albatross Station D. 5478, depth 57 fathoms, 29 July 1909 .

Description. Colonies free, discoidal, small (no more than four zooidal generations have been observed). Frontal surface convex, basal surface concave, giving to the colony a flat conical form. Autozooids small, oval in shape, separated by shallow grooves. Primary orifice subcircular. Peristome tubular, often slightly swollen in the base which external surface bears pointed, uniformly distributed tubercles. Distal part of the peristome smooth. Frontal shield perforated by 9–20 well-spaced, rounded or oval foramina that occupy the most of the frontal shield. Majority of foramina with low rim. Walls of the foraminal lumen vertical or inclined with a lower opening smaller than the upper. Frontal shield between foramina with sporadic pointed tubercles, the most observed in the peripheral area of the zooid. Marginal pores (areolae) not present. Peripheral autozooids display basal pore chambers with 1–2 communication pores. The distalmost chambers predominantly have two such pores, distolateral just one. Basal part of the colony covered by flat, often irregularly shaped kenozooids with gymnocystal periphery and large central 'membranous' area. Ovicell peristomial (ooecium fused with and opened into the peristome), terminal, only developed by peripheral autozooids. Kenozooidal ooecium globose, budded by the maternal zooid. Ectooecium membranous, entooecium calcified with numerous pointed tubercules and small pseudopores predominantly without a raised rim. Ancestrula autozooidal, smaller than the rest of zooids, always having a central position in the colony, surrounded by six autozooids.

Philippines Remarks. Among three specimens kept at the USNM only one (USNM 8325) was mentioned as cotype having a catalogue number ( Canu & Bassler 1929). We selected it as lectotype. It was collected at the Station D.5335 ( Canu & Bassler 1927, 1929), whereas two other colonies (selected here as paralectotypes) were collected at the Stations D.5336 and D.5478.

Communication pores are not seen within ‘membranous windows’ in basal kenozooids that suggests that they were secondarily closed. Instead, few tiny pits (pores?) were detected on the gymnocystal areas of kenozooids.

External morphology of ooecia corresponds to both, “escharelliform” and “microporelliform” type ( Ostrovsky 2013a), and more precise attribution will be possible when colonies with developing ooecia will be found and anatomical sections of the fresh material will be made (for methodology, see Ostrovsky & Schäfer 2003; Ostrovsky et al. 2003). We suggest, however, that Actisecos has an escharelliform ooecium since no cheilostome with an umbonulomorph frontal shield is known having microporelliform ooecium. On the other hand, no escharelliform ooecia with pseudopores has been ever described.

Distribution. Actisecos regularis was found in Philippines, Indonesia, and New Guinea.

Figures

FIGURE 27. Actisecos regularis Canu & Bassler, 1927. Philippines (A, B: lectotype USNM 8325; C, D, F, paralectotype USNM 545928; E, G, H, paralectotype USNM 545929). A, general view of lectotype from above. B, central part of lectotype from above (ancestrula shown by arrowhead). C, D, general view of paralectotype from above (ancestrula shown by arrowhead in D). E, general view of paralectotype from below. F, close-up of several autozooids showing peristome shape and details of frontal surface. G, H, close-up of the peripheral part of colony from below showing ooecia, basal pore chambers (some shown by arrows) with communication pores and flat kenozooids. Scale bars: A, C ‒ E = 500 µm; B, F ‒ H = 200 µm.