The occurrence of the Indo-Pacific swimming crab Scylla serrata ( Forskål , 1775 ) in the Southwestern Atlantic ( Crustacea : Brachyura : Portunidae )

The Indo-Pacific swimming crab Scylla serrata (Forskål, 1775) is reported here for the second time from the Southwestern Atlantic (Brazil). The species had been previously recorded from Brazil in the early 1980’s. On both occasions individuals were captured near port areas.


Introduction
During the Oligocene and throughout the Miocene, species of Scylla De Haan, 1833 inhabited the Atlantic Ocean (Tavares and Mendonça Jr. 1996).However, all the recent species in the genus are currently restricted to the Indo-Pacific.Among the four recent species is Scylla serrata (Forskål, 1775), which naturally occurs from the Red Sea, South Africa and Mauritius to Japan, Taiwan, Philippines, Timor, Indonesia, Western and Eastern Australia, Fidji, Solomon Islands, New Caledonia, Western Samoa, Panay Islands, and Tahiti (Keenan et al. 1998).In 1926 S. serrata was intentionally introduced to Hawaii, where it has selfmaintaining populations (Carlton and Eldredge 2009).In the early 1960's S. serrata was also intentionally introduced into the Gulf coast of Florida for aquaculture purposes (Park 1969).The species did not become established in the USA.
A transient female of Scylla serrata has been captured by fishermen off the coast of São Paulo (Melo 1983) and this remains the only known record from the Southwestern Atlantic to date (Tavares 2011;Tavares and Mendonça Jr. 1996;2004;Junqueira et al., 2009).More recently, a second Brazilian specimen of S. serrata was captured on 7 April 2011 and this record is discussed.

Discussion
The introduction of Scylla serrata in Florida clearly cannot explain the presence of S. serrata in both São Paulo (in 1983) and Rio de Janeiro (in 2011).However, the likely introduction point is Itaguai Port (also known as Sepetiba Port), located at Sepetiba Bay as this is, one of the biggest ports of Latin America.In terms of modes of introduction, it is unclear whether larvae of S. serrata arrived at the harbor with discharged ballast water or alternatively adult live S. serrata were carried on board ship as fresh food and possibly thrown overboard into the harbor.-Movable portion of antenna not excluded from orbit …………………………………... 5 -Movable portion of antenna excluded from orbit by a prolongation of its basal article.Antero-lateral teeth alternately large and small …………………………………………... Cronius (2 spp.) 5.
-Pterygostomial region of the carapace without a stridulating ridge …………………….. Portunus (7 spp.) -Pterygostomial region of the carapace with a stridulating ridge ………………………... Laleonectes (1 sp.) L. vocans (A. Milne-Edwards, 1878) Scylla serrata can attain a weight of over 2 kg and is highly aggressive (Motoh 1979).It inhabits estuarine and mangrove regions and is essentially carnivorous feeding upon a variety of food items, including fish, mollusks, smaller crabs, shrimps, and other small invertebrates.The species is not established in the Western Atlantic.However, if it succeeds to establish self-sustaining populations, and depending on its abundance, it could well be a serious threaten to sensitive ecosystems such as the mangroves.Scylla serrata is the host for the parasite dinoflagellate Haematodinium sp.In Alaska this parasite causes BCD (Bitter Crab Disease) considered a serious problem for the commercial fishery of Chionoecetes bairdi Rathbun, 1893 (Hudson andLester 1994).
The following key (adapted from Rathbun 1930) can be used to distinguish the Indo-Pacific swimming crabs Scylla serrata and Charybdis hellerii from native Brazilian portunids (Box 1).Between brackets is the number of species known from Brazilian waters.