Nemertean Larval ID

Currently there are 19 pilidiophoran species known to have lecithotrophic development (Maslakova and Hiebert 2014, also see Terra Hiebert, University of Oregon, Ph.D. Dissertation 2016). In Oregon, eight species are known to have planktonic lecithotrophic larvae (e.g. see Micrura sp. "dark" species complex). In addition two local species are known or suspected to have lecithotrophic development. A common intertidal species which we call Lineid sp. "large eggs" has ~600 µm oocytes and has been observed to have encapsulated (i.e. non-planktonic lecithotrophic) development (Maslakova pers. obs.). Another local species, Micrura sp. "not coei"  is strongly suspected to have lecithotrophic development due to the large size of oocytes (~300 µm). Planktotrophic pilidium larvae develop from oocytes that are 75–160 µm in diameter (Friedrich 1979; Schwartz 2009; Maslakova 2010a).  On the other hand, species with larger oocytes (150–400 µm in diameter) have lecithotrophic development (Iwata 1958; Friedrich 1979; Schwartz and Norenburg 2005; Schwartz 2009; Maslakova and Hunt 2017). The above species are both found in the rocky intertidal and produce eggs that are 300 (Micrura sp. "not coei") and 500 µm (Lineid sp. "large eggs") in winter months. Interestingly, they co-occur with another pilidiophoran with modified development – Micrura sp. "dark" (Maslakova and von Dassow 2012).