Trichoplax from marine cultures in Brazil – First record of the phylum Placozoa in the South Atlantic Ocean

Abstract

Trichoplax adhaerens F.E. Schultze, 1883, phylumPlacozoa, is a primitive and enigmatic metazoan. Thespecies was registered in different parts of the world(Mediterranean, Red Sea, North Atlantic, Japan, andCaribbean), most of the records being restricted towarm coastal waters (Pearse 1989). Although severalultrastructure studies have already been conducted withthe species (Rassat and Ruthmann 1979; Grell andRuthmann 1991), scientific community knows littleabout its biology (Grell 1971; Grell and Ruthmann1991). A few studies provided some data on the feeding,movement, vegetative reproduction, and growth of thespecies (Pearse 1989; Thiemann and Ruthmann 1991;Ueda et al. 1999; Maruyama 2004). Due to its extremesimplicity as multicellular animals, the species wasalways interesting for studies of lower metazoanevolution (see Syed and Schierwater 2002; Ender andSchierwater 2003; Schierwater 2005).Recent studies considering molecular data presenteddifferent results, suggesting that there is more than onelineage of placozoans (Aleoshin et al. 2004; Voigt et al.2004), with samples from different places, but did notattempt to name them. Although, based on the basicmorphology and histology described in the literatureand of the observed material, the specimens from theBrazilian coast match Trichoplax adhaerens (from theGulf of Trieste, Italy); it is wise, based on the resultspresented by different authors (cf. Aleoshin et al. 2004;Voigt et al. 2004), to refer to the southeastern Brazilianspecimens just as Trichoplax sp. (Figs. 1–4).Most of the placozoan records came from aquarium/laboratory observations and long maintained cultures(see Schierwater 2005). A few studies report the groupfrom nature or substrates where they might be over (e.g.Maruyama 2004). Placozoans are widespread all overthe world, but only found when ‘‘specialists’’ look forthem. Their distribution is mainly restricted to warmcoastal waters, and the closest record to our finding isfrom the Caribbean. The area where our culturing watercame from is a harbor region (see below), with relativetransit of ships from different parts of the world.Although we might expect that our specimens clustercloser to the specimens from Caribbean we cannotdiscard the possibility of a marine introduction byballast water.The specimens were found crawling on glass watchescovered with encrusting benthic green algae, and ciliates.Our culture (ca. 2 months old) started with small plasticvessels (500ml), filled with filtered sea water from theSa˜o Sebastia˜o Channel, Sa˜o Paulo State, Brazil). TheSa˜o Sebastia˜o Channel is located on the northern coastof Sa˜o Paulo State (23141