<i>Streptocephalus sirindhornae</i>, new species of freshwater fairy shrimp (Anostraca) from Thailand

Streptocephalus sirindhornae, new species, the first freshwater anostracan from Thailand, is wide-spread in the northeast of the country. It is morphologically closest to the Indian species S. dichotomus, but a sequence analysis of its SSU rDNA gene reveals that its closest relative is in fact the Indian species-pair S. dichotomus-S. simplex, that it is probably a conserved member of the S. dichotomus-group, and that it shares some relationship with the S. torvicornis-group

The cyst hatching pattern of the Thai fairy shrimp, Branchinella Thailandensis Sanoamuang, Saengphan & Murugan, 2002 (Anostraca)

We investigated factors influencing the hatching of the fairy shrimp, Branchinella thailandensis in relation to brood order, and also responses of cysts to wet and dry periods. Male-female pairs of B. thailandensis were cultured under static conditions at room temperature and fed ad libitum micro-algae (Chlorella sp.). Deposited cysts of the first, sixth and eleventh broods were monitored for cyst hatching under wet and dry conditions. Cyst hatching was scored daily for 5 days after incubation. Freshly laid cysts, immediately incubated, did not hatch in any of the experimental conditions (wet/dry). On the contrary, undried cysts immersed in their parental medium for 4 weeks showed the highest hatching in all brood treatments (76.67, 94.67, and 99.33% of the first, sixth, and eleventh broods, respectively). The cysts of the first brood hatched less successfully than did those of the sixth and eleventh broods. Cyst hatching mostly took place within 24 hours after incubation. The present study shows that a wet period has a strong influence on the cyst hatching success of B. thailandensis. The cysts require a period of retention in the parental medium for 2-4 weeks to complete their embryonic development before hatching. Hatching of the three representative broods showed a different pattern for each brood. The early broods required a longer wet period than did the late broods. In contrast to the hatching behaviour of many other species, drying is not absolutely essential for cyst hatching of this species. © Koninklijke Brill NV, 2005