Sixteen species of solitary ascidians were identified from subtidal marine fouling communities present on navigational buoys, jetty pilings, floating pontoons and nettings around the coastal waters of Singapore. Of these, twelve are new records: Ascidia gemmata, Phallusia arabica, Phallusia nigra, Rhodosoma turcicum, Rhopalaea crassa, Polycarpa argentata, Polycarpa aurita, Polycarpa captiosa, Polycarpa olitoria?, Styela canopus, Pyura curvigona and Herdmania pallida. The other four species include Ascidia sydneiensis, Phallusia philippinensis, Polycarpa papillata and Microcosmus exasperatus. A detailed morphological comparison of Phallusia nigra and P. philippinensis is included because these two species have been frequently confused, resulting in a significant under-reporting of the latter in the literature.

The solitary ascidian Herdmania momus, an Indo-Pacific species that has been introduced into the Mediterranean Sea via the Suez Canal during the past century, has so far been restricted to the Levantine region. Here we record H. momus from the Maltese Islands, which represents a considerable westwards expansion of the species' distribution range in the Mediterranean. Possible modes of introduction are discussed, with translocation of adults via shipping and subsequent spawning at destination sites deemed a plausible mechanism.

The city of São Sebastião (SS), in south-eastern Brazil, is one of the hotspots for marine research since the establishment of the Centre of Marine Biology of the University of São Paulo in the 1960s. The SS region experienced intense transformation during the past 50 years, including increasing urbanization and construction of maritime facilities. Ascidian surveys during the past 50 years have found 62 species, eight of which were described as new and 12 are introduced. Didemnidae and Styelidae are the most speciose families in São Sebastião Channel, with 20 and 15 species respectively. Phallusia nigra, Didemnum psammatodes, Trididemnum orbiculatum, Botrylloides nigrum and Symplegma rubra are the most common ascidians. Most of the species are of tropical origin and São Paulo is their southern geographical limit. Comparisons of reports of the ascidians from different time periods allowed detection of species introductions and shifts in assemblage structure in terms of both species composition and abundance. Additionally, we discuss the main taxonomic issues regarding ascidians from south-eastern Brazil and identify profitable areas for future research. We believe that the temporal data compiled here will serve as a baseline for monitoring and management of ascidians in SS. Additionally, this study provides one of the most detailed datasets of ascidian diversity from the south-western Atlantic Ocean.

Although there are a number of marine organisms located from various parts of the world, little information exists from Iranian coastal waters regarding the distribution of ascidian species. Hence, the present study attempts to describe the presence and distribution of Phallusia nigra from the four different stations along Persian Gulf coastal waters. The current study is the first record of the ascidian P. nigra off the Larak Island, Hengam Island, Qeshm Island and Bandar-e-Lengeh along the Iranian coasts of the Persian Gulf.

One of the most extensively documented marine bioinvasion phenomena is the invasion of Red Sea species to the Mediterranean Sea through the Suez Canal. The present study reports the occurrence of seven non-indigenous ascidian species along the Mediterranean coast of Israel: Ecteinascidia thurstoni, Ascidia cannelata, Phallusia nigra, Rhodosoma turcicum, Symplegma brakenhielmi, Microcosmus exasperatus and Herdmania momus. Five of these species (excluding P. nigra, and R. turcicum) probably reached the Mediterranean via the Suez Canal, since they have an extra-tropical Indo-Pacific distribution and a restricted distribution in the eastern Mediterranean. This is the first record of E. thurstoni in the Mediterranean. The accumulating evidence for the negative impact of non-indigenous ascidians on local species and habitats raises the necessity for long-term studies and monitoring of this group.

The validity of the Antarctic species of the “Oikopleura gaussica group” (O. gaussica, O. valdiviae, O. drygalskii, and O. weddelli) is discussed. The characteristics of new material from South Georgia and the Bellingshausen Sea are compared with the original descriptions. We examined 495 specimens at different stages of maturity and concluded that the characters used to differentiate these species of Oikopleura have not enough weight to justify their separation. The morphological variations found were ascribed either to intraspecific variability and/or to the different degree of maturity of the specimens examined of a single species, Oikopleura gaussica. The main taxonomic characters for the identification of this species are: the particular way in which the flat triangular gonads surround the intestinal ball like a sheath, the equal size of the two lobes of the stomach, the oesophagus entering the postero-dorsal edge of the rounded left lobe of the stomach, the presence of oval and some times lobate oral glands, and the variable number of subchordal cells (4 to 14) arranged in a single row on the right (ventral) side of the chorda.