Trochosodon fecundus, Bock & Cook, 2004

Bock, Philip E. & Cook, Patricia L., 2004, A review of Australian Conescharellinidae (Bryozoa: Cheilostomata), Memoirs of Museum Victoria 61 (2), pp. 135-182 : 166-167

Trochosodon fecundus sp. nov.

Figures 17A–F

Holotype. NMV F99007 , Dampier Archipelago, stn DA-2-75-02.

Paratypes. NMV F99008 , F99009 , Dampier Archipelago, stn DA-2-75-02 .

Etymology. fecundus (L.) – fertile, prolific, with reference to the numerous ovicells present in the specimens.

Diagnosis. Trochosodon with peristomes raised laterally and arranged quincuncially. Zooid orifices concealed, with a very wide, shallow sinus. Avicularia rounded. Ovicells prominent, symmetrical, with a thin marginal ectooecium. Root pores lunate.

Description. Colony forming a low cone, wider than high, with prominent peristomes, particularly at the margin. Calcification smooth to finely mamillate. Orifices in irregular, quincuncial series, oval, with a pair of minute condyles that delineate a broad, very shallow sinus. Peristomes raised laterally and antapically, forming a partial, shallow tube. One avicularium near and lateral to each orifice, rostrum semicircular, often orientated adapically, with a bar but no ligula. Adapical pore symmetrically placed. Ovicells fragile, symmetrical, prominent, with an ectooecial layer visible marginally, that extends laterally to form paired leaflike lobes above the orifice and the lateral part of the peristomes. Entooecium flat and smooth frontally, with raised marginal striations forming a series of pores where it meets the edge of the ectooecium. Small lunate root pores present. Antapical surface with large cancelli.

Colonies with maximum diameter 2.25 mm and height 0.75 mm, number of whorls 6–7, number of zooids per whorl 10–12.

Remarks. The extreme fragility of the ovicell calcification makes it impossible to treat specimens with bleach before electron microscopy. The striated ovicells are similar to those from this station (BMNH 1964.3.2.12 part), shows that they differ in having raised, radial series of zooid orifices, minute avicularia, and only rare, adapical, lunate root pores. The principal differences occur in the relationships and position of the ovicells, that are not exactly as described by Harmer (1957). They are, in fact, asymmetrically developed, like the ovicells of C. striata Silén (1947) but, unlike that and other similar species, have no obvious orifice. Instead, the ovicell opens into the base of the peristome through a laterally placed foramen. The peristome is long and tubular and completely obscures the ovicell opening. The frontal entooecium is striated, as figured by Harmer, and resembles that of C. striata and T. fecundus . The ectooecial wall of the ovicell of T. optatus is closely apposed to the walls of both the neighbouring peristomes; the ovicells are wedged in between them and difficult to observe. The only other species observed in that the ovicell orifice opens into the peristome is T. praecox (see below), and that has symmetrical ovicells.

The occurrence of an ancestrula with seven marginal spines ( Fig. 17E ) on the adapical centre of two colonies is unique. They are not referable to Trochosodon ; this suggests that they are extraneous and belong to another, possibly “anascan” species.

T. fecundu s is known only from north-western Australia from 20 m. Figure 18. Trochosodon asymmetricus sp.nov. NMV F99011 , paratype .

Adapical view of colony, scale = 1 mm.

figured in Trochosodon optatus by Harmer (1957: 747, pl. 48 figs 16–18, text-figs 77, 78). As the locality from that these colonies were collected is off the north-west coast of Australia, it is therefore not very remote from the type locality of T. optatus , from the coast of Java ( Siboga stn 318, Kangeang Island, 88 m). However, examination of two of the colonies

Figures

Figure 17. T. fecundus sp. nov. A, NMV F99009, paratype. Detail of orifice and adapical pore, scale = 50 µm. B–D, NMV F99007, holotype. B, Adapical view of colony with ovicells and lunate root pores, scale = 500 µm. C. detail of orifices and avicularia, note one adapical pore with developing ectooecial lamina (arrowed), scale = 200 µm. D, ovicells, orifices and lunate root pore, scale = 200 µm. E, NMV F99009, paratype. Adapical view of small colony with associated “anascan” ancestrula (arrowed), scale = 500 µm. F, NMV 99008, paratype, detail of ovicell, showing marginal ectooecium with lateral lappets and ridged entooecium, scale =100 µm.