In some metazoans, the body surface is entirely or partly covered with an array of nipples about 100 nm or less in height. This structure, a nipple array, is sometimes called the moth-eye structure because it serves as an anti-reflection property on the compound eyes of a night moth. The nipple array is supposed to be a multifunctional structure since this structure occurs in various species across different taxa. Here, we hypothesize that the nipple array may prevent the settlement of epibionts that are often a nuisance and potentially cause serious problems for the host. Using a synthetic film that imitates the nipple array, we tested the substrate selection within ascidian larval settlement. The results indicate that the nipple array has anti-fouling properties, since more larvae settled on the flat surface than the nipple array (P < 0.01, paired t-test). The present results demonstrated that the nipple array potentially serves an anti-fouling function on the body surface, which should be important especially for sessile organisms.

The ascidian Ecteinascidia turbinata is reported from Maltese waters for the first time. Mature colonies were recorded on artificial substrata at two different sites (and on natural substrata at one of these), 4 km apart, during the summer months. The appearance of this ascidian is expected to be seasonal as the winter temperature in Malta may fall below that required for the maintenance of zooid growth. A second species, E. moorei, which was described in 1890 is here confirmed to be the same as E. turbinata, meaning that the species has existed in the Mediterranean since at least ~1880. The possibility that the Mediterranean population is a relic one from warmer periods cannot yet be excluded, so it is best described as being cryptogenic. The species appears to be spreading slowly, perhaps as a result of the rise in surface sea temperature. The Maltese sites offer an opportunity to monitor the species as they are accessible dive sites. This will allow assessment of whether this species remains restricted to these sites, or if it spreads perhaps to impact other species.

Despite the current global decline in seagrass, sessile epifaunal invertebrates inhabiting seagrass ecosystems, particularly sponges and ascidians, have been poorly studied due to their taxonomic complexity. Understanding patterns of distribution of sessile epifaunal communities in seagrass meadows is an important precursor to determining the processes driving their distribution and species interactions. This study (1) identified the sponge and ascidian assemblage associated with Posidonia australis meadows and (2) determined distributional patterns of these invertebrates at a hierarchy of spatial scales in Jervis Bay, Australia. We used a fully nested design with transects distributed in the seagrass (10s m apart), two sites (100s m apart), and six locations (km apart). Within these transects, we recorded the abundance, volume, diversity and substratum used for attachment by sponges and ascidians. We encountered 20 sponge species and eight ascidian species; they were sporadically distributed in the seagrass meadows with high variability among the transects, sites and locations. A few sponge and ascidian species dominated the assemblage and were widespread across the largest spatial scale sampled. The remaining species were mostly rare and sparsely distributed. Sponges attached to a variety of substrata but most notably shells, P. australis and polychaete tubes. No obligate seagrass species were recorded although three species predominantly used P. australis as a substratum. These sponge species relying heavily on seagrass for their attachment are likely prone to disturbances impacting their host habitat. Examining the response of sessile epifauna to the degradation of their seagrass habitat remains a key challenge for the future.

The ascidian fauna at Campbell Bay, Bquary Beach and Laxman Beach, Andaman and Nicobar Islands, was surveyed. A total of six species – Botrylloides leachi, Botrylloides pizoni, Clavelina picta, Clavelina robusta, Phallusia julinea and Polycarpa pigmentate – were newly recorded in the Andaman and Nicobar Islands, and the genera Clavelina was recorded for the first time in India. It is likely that the Andaman and Nicobar Islands provide a better environment for the growth of ascidians and this area in particular is populated by a greater variety of these ascidians than any of the other areas of the islands. This paper details their morphological and taxonomical features.

The presence of the pantropical ascidian Microcosmus exasperatus has been an object of some taxonomic confusion in the Mediterranean Sea. A closely related species, M. squamiger was previously reported in the north of Tunisia (in 1962) as M. exasperatus; it has spread to the western Mediterranean and the northern part of the Ionian Sea, whereas, the reliable report of M. exasperatus has been made more recently (in 1998) in the Gulf of Gabès (South Tunisia), and later studies have confirmed its presence in the eastern Mediterranean basin (Lebanon and Israel). The occurrence of this species in Izmir (Turkey) extends its distribution range to the Aegean Sea. At present, the distributions of both species of Microcosmus are not overlapping in the Mediterranean, suggesting a different route of entrance, probably by the maritime traffic (M. squamiger via the Strait of Gibraltar; and M. exasperatus via the Suez Canal). The discontinuity in the distribution of M. exasperatus in the Mediterranean is analysed and discussed.

The twin-island state of Trinidad and Tobago has a thriving yachting industry with numbers of leisure craft having increased 10-fold from 1980 to 2000. Being geographically outside of the hurricane belt, the islands offer a prime hurricane Caribbean shelter with excellent boating and repair facilities. The Chaguaramas coastline (on the north-west peninsula) has seven (7) anchorages. One of these (the Chaguaramas Bay) was the study site for a survey of hull foulers on recreational boats. In that survey, twenty-seven (27) recreational vessels were sampled for biofoulers, one group being the Tunicates (Ascidiacea). In Trinidad and Tobago little is known about these organisms. Of the eighteen species (18) collected, eight (8) were solitary species and ten (10) were colonial species. Their distribution (all species collected) is wide and they can be found throughout the western Atlantic, the eastern Mediterranean and the Indian Ocean. This survey is a preliminary one in terms of the ascidian fauna of Trinidad and represents only one (1) sampled habitat (boat hulls). There has however been a previous survey of the Tobago fauna. For completeness, there should be a full survey of the ascidians along Trinidad's coastline including their various habitats (rocky shores, mangroves, seagrass beds, etc.). These new data could be used to determine those species which occur in natural communities in Trinidad as compared with this survey (fouling community). In this paper these preliminary results are however used for comparison with the Tobago fauna.

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.

Immature oocytes are arrested at prophase I of the meiotic process and maturation onset is indicated by oocyte nuclear disassembly (germinal vesicle breakdown or GVBD). Signaling pathways that elevate intracellular cyclic AMP (cAMP) may either prevent or induce oocyte maturation depending on the species. In some marine invertebrates and, in particular, in ascidian oocytes, cAMP triggers GVBD rather than blocking it. In this paper, we tested different cAMP elevators in fully grown oocytes at the germinal vesicle stage (GV) of the ascidian Ciona intestinalis. We demonstrated that through the activation of adenylate cyclase or the inhibition and phosphodiesterases the oocyte remained at the GV stage. This effect was reversible as the GV-arrested oocytes, rinsed and incubated in sea water, are able to undergo spontaneous maturation and extrusion of follicle cells. In addition, oocytes acquire the ability to be fertilized and start early development. However, morphology of follicle cells, embryos and larvae from in vitro matured oocytes showed different morphology from those derived from in vivo mature oocytes. The role and the transduction mechanism of cAMP in the regulation of oocyte maturation were discussed. Finally, we indicated a variation of biological mechanisms present in the ascidian species; moreover, we sustain evidence proving that tunicates share some biological mechanisms with vertebrates. This information provided new hints on the importance of ascidians in the evolution of chordates.

Settlement of the fouling community is generally influenced by the physical, chemical and biological properties of the settling surface. The colour of the substratum may also exert an influence on larval settlement. In the present study, the influence of surface colour on the recruitment of fouling communities was investigated by suspending acrylic panels (red, green, blue, white and yellow) in coastal waters. Results showed that the colour of the substratum plays an important role in the recruitment of sessile species. Recruitment was comparatively high on red and blue coloured surfaces. Barnacle and tubeworm recruitment showed significant variation (Tukey test, P < 0.05) between different coloured surfaces. The significant conclusion of this study is that the colour of the artificial substrata should be taken into consideration when interpreting results from short-term biofouling studies.

The vertical distribution of fouling communities in Kudankulam coastal waters was studied for a period of one year (January to December 2005) by suspending wooden test panels at 1 m, 4 m and 7 m depths. Panels were submerged on short-term duration (15 days) and long-term basis (cumulative). The fouling organisms observed were barnacles, mussels, ascidians, polychaetes, amphipods and seaweeds. Recruitment was observed on the panels throughout the year with a considerable variation in relation to time and depth. On the short-term series, the fouling biomass varied from 0.218 to 1.23 g.dm−2 (dry wt) at 1 m, 0.23 to 4.72 g.dm−2 (dry wt) at 4 m and 0.241 to 5.66 g.dm−2 (dry wt) at 7 m depths. The biomass of the fouling community that colonized on the long-term panels ranged between 0.79 and 35 g.dm−2 (dry wt) at 1 m, 3.72 and 58.2 g.dm−2 (dry wt) at 4 m and 0.241 and 55.9 g.dm−2 (dry wt) at 7 m depths. At 1 m depth, macro-algae, ascidians (Botryllus tuberatus and Diplosoma sp.) and amphipods were the dominant species. Barnacles, tube worms and ascidians (Didemnum spp.) were abundant on the 4 m and 7 m depth panels. In general, the fouling community recruitment was higher at 4 m than 1 m and 7 m depths.

A total of 25 species of ascidians were collected in the Mar Piccolo of Taranto, a semi-enclosed Mediterranean basin. Three are non-indigenous for the Mediterranean Sea: Microcosmus squamiger, Polyandrocarpa zorritensis and Distaplia bermudensis. The substrate features, season and depth affect the distribution of ascidians in the study area. Some species, such as Pyura dura and Pyura microcosmus, were found only on artificial substrates, while Ascidiella aspersa was almost exclusively recovered on natural bottoms. Seasonal variation in the ascidian distribution and abundance seems to be due mainly to their biological cycles, larval recruitment and adaptation. During the autumn and winter the most abundant species were Clavelina phlegraea and Ciona intestinalis, while A.aspersa was particularly abundant during spring. Depth and more directly light intensity play an important role in ascidian distribution. In the upper few metres the shallow-water species Polyandrocarpa zorritensis was abundant due to its photopositive larvae. Even though the distribution and abundance changed significantly between substrates, seasons and depths, the most abundant species in the Mar Piccolo of Taranto were Clavelina phlegraea, Ciona intestinalis and Styela plicata all of which are able to tolerate the variations in environmental conditions, low rate of water renewal and continuous silting of this semi-enclosed sea. Assuming the role that the above mentioned species have as marine pollution indicators and the abundance recorded for some of them, a high degree of environmental stress can be confirmed for the Mar Piccolo of Taranto. A comparative list of the ascidians recorded in this and previous studies is also reported.