Adult Tetrastemma bilineatum surrounded by yellow embryos (left, scale 1.0 mm) where embryos had polar bodies when collected in March (9 o'clock on left embryo, middle) and after several days developed into hoplonemertean larvae (right). Note hair-like anterior projections and two pairs of eyes (right). Scale bar 100 µm.
Tetrastemma bilineatum
Sequence Data: 16S, COI
Reproductive individual observed in Coos Bay: Mar
There are six species in the hoplonemertean genus Tetrastemma reported from central CA to OR (Roe et al. 2007). Of those, we have sequence data for two species (T. albidum and T. candidum and T. bilineatum (above left), with two distinct longitudinal brown lines, is only distantly related to either species. The development is known for several Tetrastemma (or Quasitetrastemma, Chernyshev 2008) species including the encapsulated development of T. candidum (Maslakova and Malakhov 1999) and the free-swimming lecithotrophic development of T. vermiculum (Lebedinksii 1898 in Chernyshev 2008), Q. nigrifrons and Q. stimpsoni (Chernyshev 2008).
The embryos of Tetrastemma bilineatum are yellow and brooded in a parchment tube which surrounds the adult body (above left). Brooding adults were found under rocks on a sandy beach (North Spit) in March 2013. The ciliated embryos were surrounded by a thick chorion and free-swimming larvae emerged after several days. These seemingly lecithotrophic larvae have two pairs of eyes and a distinct apical tuft of hair-like cirri rather than a single blade-like projection (above right).