Description and ecophysiology of a new species of Syndesmis Silliman, 1881 (Rhabdocoela: Umagillidae) from the sea urchin Evechinus chloroticus (Valenciennes, 1846) Mortensen, 1943 in New Zealand

Abstract

A new rhabdocoel of the genusSyndesmisSilliman, 1881 (Umagillidae) is described from the intestine of the NewZealand sea urchinEvechinus chloroticus(Valenciennes, 1846) Mortensen, 1943a. This new species,Syndesmiskurakaikinan. sp., is morphologically distinct and can easily be recognised by its very long ( ± 1 mm) stylet andits bright-red colour. In addition to providing a formal description, we present some observations on re-production and life history of this new species. Fecundity is comparable to that of other umagillids and the rateof egg production and development increases with temperature. Hatching in this species is induced by intestinalfluids of its host. Relevant to global warming, we assessed the effect of temperature on survival, fecundity, anddevelopment. The tests indicate thatSyndesmis kurakaikinan. sp. is tolerant of a wide range of temperatures(11–25 °C) and that its temperature optimum lies between 18.0 and 21.5 °C. Egg viability is, however, sig-nificantly compromised at the higher end of this temperature range, with expelled egg capsules often beingdeformed and showing increasingly lower rates of hatching. Given this, a rise in global temperature mightincrease the risk ofSyndesmis kurakaikinan. sp. infecting new hosts and would possibly facilitate the spread ofthese endosymbionts