Tubulanus spp.

 

Five species of Tubulanus are reported from the Nortern California to Oregon (Roe et al. 2007). We have sequence data for only three of those species and have identified larvae of two: T. polymorphus and T. sexlineatus. We have found three distinct larval types that are nested on our molecular phylogenies within the genus Tubulanus, but currently we cannot know if these larvae represent undescribed species or Tubulanus species reported from the NE pacific for which we have yet to obtain sequence data (T. capistratus and T. cingulatus). The sheer number of larvae we have found, however points toward at least one previously unknown species of Tubulanus in this region. The larvae are distinguishable from other palaeonemertean larvae in that they are eyeless, have thick handlebar-like lateral cirri and a relatively thick epidermis (left).

Three Tubulanus species which we've found as larvae in the plankton collected January, February and October 2013 (left to right). Scale bars 100 µm.

Tubulanus larva collected in January 2013, shown here in two postures: swimming (left) and compressed antero-poseriorly (right). Scale bars 100 µm.

Tubulanus sp. 1

Sequence Data:  16S, COI

Observed in Coos Bay: Jan, Oct

This Tubulanus larva has very conspicuous and handle-bar like lateral cirri at younger stages (above), however in later stages, they are less distinct (below). The larvae have no eyes, a small caudal cirrus and no prominent apical tuft. They can compress themselves antero-posteriorly where the body wrinkles resembling segments (above right). Later developmental stages have a very prominent dark brown to black epidermal band toward the larval posterior (below). The gut region remains filled with golden lipid droplets, which are not seen in other Tubulanus larvae.

Advanced larvae of Tubulanus sp. "1" collected in October 2013, shown here in two focal planes. Note coiled and advanced proboscis (left) and epidermal pigment band (right). Scale 100 µm.

Tubulanus sp. "2" larva collected February 2013. Note thick lateral cirri, a light pigment band posteriorly and dark gut. Scale 100 µm. 

Tubulanus sp. 2

Sequence Data:  16S, COI

Observed in Coos Bay: Feb, Oct

The second Tubulanus species larva resembles later developmental stages as the previous, except that the lateral cirri remain thick and curve downward in this species. Furthermore, the posterior band of color is not nearly as distinct and sharp as in Tubulanus sp. "1". There is also a stark dark color in the gut region. Larvae belonging to this species have been collected both in February and October, suggesting a reproductive season with several peaks throughout the year.

Tubulanus sp. "3"  larva belonging to a third species, collected in October 2013 shown here in dorsal (left and middle) and lateral (right) view. Note "pseudosegments" on compressed individual. Scale 100 µm.

Tubulanus sp. 3

Sequence Data:  16S, COI

Observed in Coos Bay: Oct

The third Tubulanus species who's larva we find in the plankton in Coos Bay is recognizable by exhibiting a combination of the characters from the other Tubulanus larvae discussed above. This species has lateral cirri, dark gut color and compresses its body such that "pseudosegments" are visible (above right). However, we did not observe any epidermal color patterns in the larva of this species, suggesting that it may be distinguishable from other Tubulanus larvae that way, in later developmental stages. Having only found and identified one larva from this species, so far, we cannot be sure if this is a species-specific character or dependent on developmental stage.