Exochella moyanoi Ramalho & Calliari, 2015

López-Gappa, Juan, Liuzzi, María G., Castro, Karen L., Bobinac, Magalí & Schwindt, Evangelina, 2022, Fouling bryozoans in Argentine harbours (Southwest Atlantic): new records and the description of a new species, Zootaxa 5205 (4), pp. 374-400 : 383

Exochella moyanoi Ramalho & Calliari, 2015

( Figs 21–23 )

Exochella longirostris : Canu, 1908: 300, pl. VI, fig. 13; Marcus 1937: 82, fig. 43; 1941: 22, fig. 16; 1949: 1 (non E. longirostris Jullien, 1888 ).

Exochella moyanoi Ramalho & Calliari, 2015: 578 , fig. 6A−C.

Material examined. MACN-Pi 1920, Holocene material identified by Canu (1908) as Exochella longirostris Jullien, Belgrano harbour (‘Puerto Militar’ in Canu 1908). MACN-In 32304, Mytilus bank, off Mar del Plata. MACN-In 32531, Mytilus bank, off Mar del Plata, January 15, 1971. MACN-In 43877, Storni pier, Puerto Madryn, October 27, 2016, collected by Karen Castro.

Description. Colony encrusting, unilaminar, multiserial, usually closely adnate on hard substrates. Autozooids irregularly hexagonal, 335−431 × 246−373 µm, disposed quincuncially, separated by distinct sutures. Frontal shield slightly convex, smooth, with 11−13 marginal areolae separated by ridges converging towards the center; areolae initially rounded and conspicuous, then becoming more slit-like, their size restricted by increasing frontal calcification. Primary orifice D-shaped, with indistinct proximo-lateral condyles; proximal border slightly concave, without denticle. Oral spines 2−4, delicate, cylindrical, articulated, mostly absent, even in marginal autozooids. Peristome well-developed, with a medio-proximal prominent mucro flanked by two proximo-lateral concave spaces; bluntly triangular processes project from the lateral borders but do not fuse with the median mucro; secondary orifice barely longer than wide, 92−131 × 100−119 µm. Adventitious avicularia usually single, sometimes paired, developing from one of the marginal areolae, located mid-laterally, sometimes proximally; rostrum triangular, protruding, pointing towards the orifice of the neighbouring lateral or proximal autozooid; crossbar complete. Ovicell rounded, endozooidal, budding from the distal peristomial margin over the proximal frontal shield of the following zooid, visible only during early ontogeny, then completely covered by frontal calcification. Ancestrula tatiform, with ovoid opesia, gymnocyst granular, more developed proximally and ten delicate spines. Early astogeny with a first pair of zooids budded distolaterally.

Remarks. Exochella longirostris Jullien, 1888 , a common species in the Magellanic Region, differs from E. moyanoi in its slightly larger zooids, coarsely nodular frontal shield and more slender adventitious avicularia (see Hayward 1991).

The examination of Holocene (‘Postpampéen’) material from Puerto Belgrano identified as E. longirostris shows that it is identical with Recent material of E. moyanoi . In the Bahía Blanca estuary, the marine transgression occurred during the middle-late Holocene, after 7,500 yr B.P. ( Aliotta & Farinati 1990). Its presence in Argentina before the arrival of European maritime traffic shows that E. moyanoi is a warm-temperate native species reaching its southern limit of distribution at Chubut province, Argentina. This study expands its geographic distribution southwards by about 5 degrees of latitude.

Distribution. Brazil, from Espirito Santo to Rio Grande do Sul ( Vieira et al. 2008, as E. longirostris ; Ramalho & Calliari 2015), Buenos Aires and Chubut provinces (this study); Holocene of Belgrano harbour, Buenos Aires Province ( Canu, 1908).

Figures

FIGURES 18–23. FIGURES 18–20. Bicellariella edentata (MACN-In 32310); 18, general aspect; 19, branch bifurcation and ovicelled zooid; 20, close-up of avicularium. FIGURES 21-23. Exochella moyanoi (MACN-In 43877); 21, general aspect; 22, growing margin, showing ovicells in different stages of development; 23, close-up of peristomes and avicularia. Scale bars. 18, 21, 22: 200 µm; 19, 23: 100 µm; 20: 20 µm.