First recording of kinorhynchs from Java, with the description of a new brackish water species from a mangrove-fringed lagoon

A new species of Echinoderes, E. applicitus sp. nov., is described from a brackish water lagoon on the south coast of Central Java, Indonesia. The species is recognized by its complete lack of spines on segments 1–10, lateroventral tubules on segments 5 and 8, laterodorsal tubules on segment 10, and a mid- to subdorsal tergal protrusion of segment 10 that extends beyond the posterior margin of segment 11. The general reduction of spine size and numbers, the absence of lateral terminal accessory spines in females and the enlarged sieve plate suggest a close relationship with E. rex, E. coulli, E. maxwelli and E. teretis. The adaptation to a brackish, estuarine habitat with highly fluctuating salinities is also shared between the three latter species and E. applicitus sp. nov. The examined populations of the new species had a relatively high infection rate (10–15%) of epibiontic growth from at least three different prokaryotic or protist organisms. An infection rate of this magnitude has not previously been reported for kinorhynchs, and it may have a relationship to the brackish habitat.