Will the real Hermissenda crassicornis please stand up

AquaFlite Custom Wetsuits, Dive Skins, and Dive Parkas

[ Follow Ups ] [ Post Followup ] [ California Scuba Diving BBS ] [ FAQ ]

Posted by Merry on September 26, 2016 at 13:39:25:

One of our most striking nudibranchs has undergone a name change. What was once the familiar Hermissenda crassicornis is now classified as Hermissenda opalescens. (T. Lindsay, A. Valdés, 2016)

Historically, various nudibranch subjects from a large geographic range were classified as H. crassicornis. Recent molecular, morphological, and populations analyses revealed that there are actually three distinct species within the genus Hermissenda. One species, H. emurai, occurs in Japan and the Russian Far East.

The two other species that were differentiated by DNA studies are also different morphologically and inhabit separate geographic ranges for the most part.
1. Hermissenda opalescens is found from Northern California to the Sea of Cortez.
2. Hermissenda crassicornis ranges from Alaska to Northern California, but it should be noted that crassicornis and opalescens overlap in range between Point Reyes and Bodega Bay.

Hermissenda opalescens
The original taxonomic name has been restored to this nudibranch; H. opalescens was first assigned to a specimen from San Diego in 1863.

 photo 1. Hermissenda opalescens DSC_6925_zpsfjvvzdu8.jpg

 photo 2. Hermissenda opalescens DSC_6828_zpsjxd5q0wy.jpg

 photo 3. Hermissenda opalescens duo_zpscgday2a5.jpg

The easiest way to distinguish crassicornis from opalescens is the longitudinal white stripe on the cerata of crassicornis, while the cerata of opalescens have white tips but no white stripe.

 photo 8. H. crassi. amp opal. cropped DSC_4177_zpsckqp1f6o.jpg

Hermissenda crassicornis from British Columbia. Originally described in 1831 from Sitka, Alaska.

 photo 5. Hermissenda crassicornis DSC_2611_zpsarmywvv3.jpg

 photo 6. Hermissenda crassicornis alternate DSC_5556_zpsg030yvc7.jpg

 photo 7. Hermissenda crassicornis DSC_2711_zpsc6bn08wl.jpg

More photos of the real Hermissenda crassicornis can be found on Kevin Lee’s site.
Link below.

Follow Ups:

Optional Link URL:
Optional Link Title:
Optional Image URL:
Post Background Color: White     Black
Post Area Page Width: Normal   Full
You must type in the
scrambled text key to
the right.
This is required to
help prevent spam bots
from flooding this BBS.
Text Key: