<![CDATA[<B>Anatomical study on <I>Myoforceps aristatus,</I> an invasive boring bivalve in S.E. Brazilian coast (Mytilidae)</B>]]>

Abstract

The bivalve Myoforceps aristatus (Dillwyn, 1817), also known as Lithophaga aristata, have been recently collected in the coasts of Rio de Janeiro and São Paulo, Brazil; a species that bores shells of other mollusks. This occurrence has been interpreted as an invasion of this species, originally from the Caribbean. The distinguishing character of the species is the posterior extensions of the shell crossing with each other. Because specimens with this character have also been collected in the Pacific Ocean, they all have been considered a single species. However, it is possible that more than one species may be involved in such worldwide distribution. With the objective of providing full information based on Atlantic specimens, a complete anatomical description is provided, which can be used in comparative studies with specimens from other oceans. Additional distinctive features of M. aristatus are the complexity of the incurrent siphon, the kidney opening widely into the supra-branchial chamber (instead of via a nephropore), and the multilobed auricle.KEYWORDS: Myoforceps aristatus, biological invasion, boring bivalve, Brazil, anatomy, systematics.Samples belonging to Myoforceps aristatus have been collected in the southeastern coast of Brazil in the last two years, far outside of the normal geographic range of the species. The samples were found in shells of larger size, including cultivated scallops (Pectinidae), and attracted attention as an invading bivalve causing possible damage to native species, because the datemussels perforate living shells, causing deformation of the host and even its death.Only one species of the closely related genus Lithophaga Röding, 1798, is commonly found on the (Dillwyn, 1817), previously known as Lithophaga aristata, is a small bivalve that bores into calcareous hard substrata, mainly shells of other mollusks. In the western Atlantic, the species is known from North Carolina to Florida, the Gulf of Mexico and the northern Caribbean Sea. The species is easily identified by pointed tips at the posterior ends of the valves, which cross like fingers (Abbott, 1974) and give the common name of the species as "scissor datemussel". INTRODUCTION Myoforceps aristatus SIMONE, L.R.L. & GONÇALVES, E.P.: MYOPHORCEPS ARISTATUS, AN INVASIVE BIVALVE IN BRAZILS.E. Brazilian coast. Lithophaga bisulcata (Orbigny, 1842) is of larger size, normally inhabits soft rocks and corals, and it is not usually found boring into shells.This paper reports the first occurrence of Myoforceps aristatus, another invasive species on the Brazilian coast, and provides new data on its morphology and anatomy. The geographic distribution of the M. aristatus includes the Pacific (e.g., Turner & Boss, 1962;Abbott, 1974), as samples of Myoforceps with crossing posterior ends of the shell have also been collected in that ocean. This paper provides anatomical information that can be used in future comparative studies with samples from other oceans. MATERIAL AND METHODSThe available specimens were preserved in 70% E...

Associated fauna and effects of epibiotic barnacles on the relative growth and reproductive indices of <em>Stramonita haemastoma</em> (Gastropoda: Muricidae)

“…The continuous growth of the endobiont involves a growth in the volume of the breach causing a progressive perforation of the shell of the basibiont, which in some cases leads to its death. This finding was recorded by Simone and Gonçalves (2006) and by Trigui El Menif et al (2006), respectively in Nodipecten nodosus infested by L. aristata and in V. verrucosa infested by Rocellaria dubia. With regard to our results, the infestation of S. haemastoma by L. aristata does not seem to act negatively on the gastropod at this level, because the extracted endobiont had a size of 17 mm in length and 6 mm in thickness, which does not exceed either the length or the thickness of the gastropod columella.…”

“…Negative effects in the basibiont could probably occur with the progressive growth of the endobiont, since L. aristata can attain a length of 52 mm (Turner and Boss 1962). According to Simone and Gonçalves (2006), the geographical distribution of the L. aristata is probably limited to the Atlantic coasts. Moreover, Ávila et al (2009) discovered L. aristata as a fossil form on the island of Santa Maria (Azores).…”

The gill morphology of the date mussel Lithophaga lithophaga (Bivalvia: Mytilidae)

“…Although a number of previous studies have addressed the life history and ecological features of the members of the genus Lithophaga (Valli et al, 1986;Scott, 1988;Brickner et al, 1993;Sinis, 1994-1995;ElMenif et al, 2007;Devescovi, 2009), including limited descriptions of the general anatomy of the genus (Turner and Boss, 1962;Simone and Goncalves, 2006), very little has been published on its ctenidial structure (Turner and Boss, 1962). Well-documented observations are available on other genera of Mytilidae: Mytilus, Mytella, and Perna (Aiello and Sleigh, 1972;Domouhtsidou and Dimitriadis, 2000;Gregory and George, 2000;Gregory et al, 2002;David and Fontanetti, 2005;David et al, 2008).…”

Anatomical differences among specimens of Pinctada imbricata Röding, 1798 from different South American localities

“…We surveyed the specimens previous housed on Museu Nacional da Universidade Federal do Rio de Janeiro (MNRJ) and Museu de Zoologia da Universidade de São Paulo (MZUSP) collections. For the soft parts anatomy, a total of 22 specimens from 10 localities (see Table 1) were dissected under stereomicroscopy, using standard techniques (see SIMONE and GONÇALVES, 2006). Additionally, specifically for Pinctada the dissection following the sequential steps: 1) the right valve was removed, with subsequent exposure of the mantle; 2) the distal edge of the mantle was removed along with the radial pallial muscles; 3) the pericardium membrane was carefully removed so that the auricle and associated circulatory structures could be preserved; 4) an incision on the visceral sac was performed along the antero-posterior muscles; 5) gonads and distal portions of the digestive gland were removed to expose the stomach and intestine (partially); 6) an incision parallel to the direction of the style sac/proximal intestine towards the pearl pocket was performed to visualize the remaining intestine.…”