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Sex is found in all major eukaryotic groups of organisms. It has been known for some time that the choanoflagellates also possess the genes involved in meiosis and a full sexual cycle was also recently accounted for in Salpingoeca rosetta. With reference to the loricate choanoflagellates the current status is that only circumstantial evidence, from wild material of Bicosta spinifera, exists in favour of documenting division patterns that go beyond plain asexual division, and that has the potential to represent stages in a sexual life cycle. Here we present further evidence from wild material documenting possible morphotype changes that might similarly indicate the existence of complex life cycles. In this particular case, it revolves around the existence of so-called 'combination loricas' (i.e. two loricas that occur physically united), representing consistent species combinations from the genera Acanthocorbis and Stephanoeca.

A new acanthoecid choanoflagellate species, Acanthocorbis mongolica sp. nov. was found in preserved phytoplankton samples from the freshwater lake Bayan Nuur (Uvs Nuur Basin, NW Mongolia) in concentrations of up to 1.8 × 10 5 cells L −1 . It is the first well-documented species of the mainly marine order Acanthoecida to be found in a freshwater lake. The lorica structures were studied with scanning electron microscopy. Key morphological features of the vase-shaped lorica are spine bases that are composed of multiple (2–4) parallel costal strips, and the existence of two transverse costae. The ecological implications of this find are discussed.

Three new acanthoecidaean species collected from the coastal waters of Taiwan and Japan are described : Acanthocorbis camarensis n. sp. resembles Acanthocorbis unguiculata in lorica morphology, but differs in having regularly arranged longitudinal and transverse costae at the anterior lorica chamber, and in lacking a nail at the apical end of anterior spine ; Diaphanoeca spiralifurca n. sp. is characterized by the spiral arrangement of the costal strips in the posterior half of the lorica chamber and is closely related to Diaphanoeca grandis ; Stephanoeca supracostata n. sp. is closely related to Stephanoeca elegans, but differs in having an additional transverse costa at the anterior lorica chamber.