Arthropoma cecilii ( Audouin, 1826 )

Ramalho, Laís V., Muricy, Guilherme & Taylor, Paul D., 2011, Taxonomic revision of some lepraliomorph cheilostome bryozoans (Bryozoa: Lepraliomorpha) from Rio de Janeiro State, Brazil, Journal of Natural History 45 (13 - 14), pp. 767-798 : 777-780

Arthropoma cecilii ( Audouin, 1826)

( Figure 5 )

Flustra cecilii Audouin 1826: 239 , pl. 8, fig. 3.

Arthropoma cecilii, Canu and Bassler 1930: 316 ; Marcus 1937: 93, fig. 49; 1955: 297; Harmer 1957: 1001, pl. 72, fig. 23, text-fig. 108; Gautier 1962: 127; Ryland and Hayward 1992: 263, fig. 19C, D.

? Arthropoma cecilii, Canu and Bassler 1929: 296 , pl. 32, fig. 1, text-fig. 126; Osburn 1952: 333, pl. 3, figs 1–3; Liu et al. 2001: 607, pl. 51, fig. 4.

Material examined

Arraial do Cabo, Rio de Janeiro State: MNRJ-069, 24 May 2002, Pedra Vermelha (Cabo Frio Island ), collected by L. V. Ramalho , depth 5 m.

Arthropoma cecilii . NHM 1948.2.16.57, Santos, Brazil, collected by E. Marcus; NHM 1975.7.1.34, Chios, Expedition to Chios, 1967; NHM 11.10.1.1257, British Barleei; NHM 2000.4.11.1042, 14 October 1978, Swa Barrier Reef , Fiji, collected by J.S. Ryland; NHM 1931.12.30.99, Jolo, Philippines, Bassler Collection, 38 m.

Revised diagnosis

Colony encrusting, unilamellar; autozooids hexagonal to rectangular with frontal wall perforated by circular pseudopores except centrally; orifice with proximal border almost straight; sinus moderate to deep; ovicell globose, imperforate.

Description

Colony encrusting, unilamellar ( Figure 5A ), varying in size and shape, white with orange embryos.

Autozooids hexagonal to rectangular, longer than wide (746 µm long, range 657–951 µm, by 437 µm wide, range 333–490 µm), disposed in quincunx or irregularly ( Figure 5A,B ); occasionally very irregular shaped zooids. Frontal wall with large circular pseudopores, except in a central area beneath the orifice, which is smooth and imperforate. Umbo often present immediately below the orifice. Orifice D-shaped, wider than high ( Figure 5C ), with a straight proximal border and narrow; U-shaped sinus, moderate to deep (168 µm long, range 157–196 µm by 213 µm wide, 196–245 µm), constricted and almost closed distally ( Figure 5B–D ).

Ovicell globose, higher than wide (437 µm long, range 392–470 µm long by 384 µm wide, range 323–412 µm, without pores, surface rough, seemingly cryptocystal; ectooecium reduced to a smooth, narrow band bordering orifice; closed by zooidal operculum.

No oral spines observed. Avicularia absent.

Habitat

Colonies were found on rock at 5 m depth.

Geographical distribution

This species is widely distributed in temperate-circumtropical regions of the southeast Atlantic ( Brazil), Western Atlantic, Mediterranean Sea, Indian and Pacific Oceans ( Canu and Bassler 1929, 1930; Marcus 1937; Osburn 1952; Ryland and Hayward 1992). In Brazil it has been recorded from São Paulo (Santos) and Espírito Santo (south of Vitória) ( Marcus 1937, 1955), and now Arraial do Cabo (Pedra Vermelha, Cabo Frio Island) in Rio de Janeiro State.

Remarks

The Brazilian material is very similar to specimens collected in the North Atlantic (NHM 1975.7.1.34, Chios; and NHM 11.10.1.1257, British Barleei) and the Pacific (NHM 2000.4.11.1042, Fiji), sharing with them a sinus of the same shape, not very deep and narrowing distally, as well as lacking pseudopores on the median region below the sinus. However, material from Chios (NHM 1975.7.1.34) has two oral spines. A specimen from Santos (NHM 1948.2.16.57) is also very similar to those described here. It shows variability in sinus depth, which is sometimes deep and narrow and sometimes shallow and wide, but always the sinus narrows at its opening.

The specimens described by Osburn (1952) and Canu and Bassler (1929) are distinguished from Brazilian species because they have a sinus that is deep and straight, without the extension of the orificial proximal border, pseudopores over the entire frontal surface, and the umbo may be absent. The specimen described by Liu et al. (2001) also has pseudopores over the entire frontal wall, the sinus is shallower than in Osburn’s material, and the extension of the orificial proximal border does not occur. Comparing the measurements of Osburn’s material to the Brazilian specimens, substantial differences are observed in zooid size, which is smaller and narrower in Osburn’s material; the operculum is also smaller. Similar differences are observed in the Chinese specimens described by Liu et al. (2001). These specimens are in need of a detailed review because of several differences with A. cecilii sensu Audouin (1826) .

Marcus (1937) and Harmer (1957) regarded A. perugiana as a synonym of A. cecilii . However, SEM study of A. perugiana shows differences between these two species in the size and shape of the sinus, which is narrower, deeper and straight in A. perugiana , the proximal border of the orifice not extending over the sinus entrance. These differences suggest that A. cecilii and A. perugiana are separate species. New studies should be carried out on material previously identified as A. cecilii to correct the identification and geographical distributions of these two species.

The Brazilian material studied here is considered to be A. cecilii . This is the first record of A. cecilii from the Rio de Janeiro coast. Its distribution in Rio de Janeiro State seems to be limited to a small area in Arraial do Cabo on the basis of sampling undertaken to date.

Figures

Figure 5. Arthropoma cecilii (Audouin, 1826). (A) Part of the colony; (B) detail of the zooids; (C) detail of an elongate autozooid; (D) fertile zooids. Scale bars: A: 600 µm; B–D: 200 µm. MNRJ-069.