Ototyphlonemertes sp. 1 larva collected in October 2013. Note posterior cirrus (left), two black eyes and two statocysts with polystatoliths inside (right). Scale bars 100 µm.
Ototyphlonemertes sp. 1
Sequence Data: 16S, COI
Observed in Coos Bay: Oct-Nov
The larvae of the genus Ototyphlonemertes are easy to recognize by the presence of statocysts positioned in the posterior region of ventral cerebral ganglia (Envall and Norenburg 2011). Ototyphlonemertes are believed to have short-lived larvae being dependent on yolk reserves (Norenburg and Stricker 2002; Andrade et al. 2011b) and they are found in near-shore coastal plankton (Chernyshev 2000). The larvae of three Ototyphlonemertes species were described from the Sea of Japan including O. martynovi, O. aurita and O. norenburgia sp. (Chernyshev 2000).
We find the larvae of an unknown Ototyphlonemertes species (above) in plankton samples in Coos Bay. They are very fast swimmers (as has been seen for O. martynovi, Chernyshev 2000) and trapping them between a cover slip and microscope slide is not an easy task. They have two black eyes, which are lost in adults. The most distinctive character of these Ototyphlonemertes larvae are two spherical statocysts, each containing a polystatolith (a statolith consisting of more than 12 granules). The statolith shape is not unlike that of the locally reported O. americana (Roe et al. 2007) however, Ototyphlonemertes species are mesopsammic and easily overlooked and there are likely many more species locally and it is equally likely that this is the larva of a currently undescribed species (Envall and Norenburg 2011).
We've collected the larvae of a single Ototyphlonemertes species, their gut is always packed with golden lipid granules and, at their posterior, they have a caudal cirrus. They have a rounded anterior and no prominent apical tuft. The sizes range dramatically, suggesting that they may be feeding in the plankton. Although hoplonemertean larvae are thought to be non-feeding, recent evidence based on DNA sequence data of gut contents and intraspecific variation in size of wild-caught larvae suggests that some species may be feeding (Maslakova and Hiebert 2014).