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...