Cerebratulus californiensis species complex

Many of the undescribed species we’ve uncovered in the NE Pacific are cryptic species complexes which are currently lumped under the same name. One example is the Cerebratulus californiensis species complex. We’ve found two NE Pacific species that form a species complex with C. californiensis. All three share a larval morphotype characterized by a pyramidal shaped episphere and pigment spots on larval lobes and lappets (left). Interestingly, other larvae of the same morphotype collected from other regions in the world and identified with DNA sequence data are also related to the group of species we find in the NE Pacific. 

Cerebratulus californiensis

Sequence Data: 16S, COI

Observed in Coos Bay: Jan-Mar, June-July

The larvae of Cerebratulus californiensis can be very common in the plankton. In 2013, we encountered many individuals in February. They are easily recognizable by the characteristic pyramidal episphere and compact rounded pigment spots on their lobes and lappets. Although pigment spots are usually confined to one spot per lappet or on either side of anterior and posterior lobes, several smaller spots are also seen. When viewed from the top down, the anterior (and sometimes posterior) lobes are scalloped into three sub lobes. Advanced larvae are very large (up to 1200 µm in height) and the juvenile inside is long and slender with pointed anterior, two small eyes and a caudal cirrus. 

Cerebratulus sp. "Sunset Bay"

Sequence Data: 16S, COI

Observed in Coos Bay: July, Oct

This is the larva of one of the undescribed species in the Cerebratulus californiensis species complex and we call this species Cerebratulus sp. “Sunset Bay” in reference to the location in which we find the adults. The larval body resembles that of other members of the Cerebratulus californiensis species complex with pyramid-like episphere and pigment spots. Advanced juveniles are pointed anteriorly and posteriorly, with two small eyes and a caudal cirrus. A potential difference between this larva and the larvae of other members of this species complex is the pigment pattern on the larval lobes and lappets. Rather than circular, the pigment in Cerebratulus sp. “Sunset Bay” are irregular amorphously star-shaped patches. We have only found and identified a single larval specimen (above) that belongs to this species, so whether the characters we describe here are species-specific or individual variation remains to be seen.

Cerebratulus sp. "pink proboscis"

Sequence Data:  16S, COI

Observed in Coos Bay: July, Oct

This is the larva of the second undescribed species in the Cerebratulus californiensis species complex and we call this species Cerebratulus sp. “pink proboscis”. Their larvae are not differentiable from C. californiensis, although they are less common in the plankton. We usually find the larvae of this species in October. They exhibit the same larval morphotype observed for C. californiensis and C. sp. "Sunset Bay". Although we’ve only collected and identified three larvae, we have yet to observe the scalloping of the anterior or posterior lobes, which is seen in the larvae of C. californiensis. Advanced juveniles have two small eyes are pointed anteriorly and posteriorly and have a caudal cirrus. The pigment spots develop early, which can be seen in the young larva (right) collected in October 2013.

General larval morphology = hat - shaped

Pilidial characters = spotted lobes and/or lappets

Pilidial spots = present on both lobes and lappets