Cephalopyge trematodes

Image courtesy of Todd Aki
Halmahera, Indonesia
Feb. 2020

Cephalopyge trematodes (Chun, 1889)

Well we venture off into Never-Never land with Peter Pan this week and present an amazing pelagic nudibranch. We refer to the family Phylliroidae Menke, 1830, to which this species belongs, as "highly modified." In case you are wondering that is scientific lingo for "advanced or highly evolved." This species certainly is.

The species name explains some of this. Cephalo is Greek for head and "pyge" refers to the position of the anus, in this case way up front right behind the head. The trivial name "trematodes" was given by Chun to draw attention to the Tremotode worm likeness, the shape of a fluke.

This amazing species is transparent, making it hard to see as it swims in the water column. The viscera are seen as rows of white organs. The body is elongate with a fish like tail. There are two long rhinophores on the head, just like normal sea slugs, but these guys are contractile. The brightest coloration comes from the white to yellow photophores ornamenting the body.

This critter swims fast, so shots like Todd's, shown here, are hard to get. Because it is pelagic, swimming around the world in oceanic currents, it is not surprising that the species distribution is circumtropical. It is known to feed on siphonophores - those colonial jellyfish like organisms. Portuguese Man-of-War, which looks a lot like a jellyfish and Velella velella or the By-the-Wind-Sailors are examples of a siphonophores.

Photos like Todd's are hard to come by and are usually only achieved during "Black water" night dives. To see more awesome Black water photos like Todd's go to Facebook .

Dave Behrens
Sammamish, WA 98074
Feb., 2020
Send Dave email at davidwbehrens@gmail.com

Todd Aki
I started diving about 20 years ago and became obsessed with underwater photography shortly thereafter. I am shooting with a Canon 7D mark ii in a Nauticam housing, two Inon Z240 strobes and either a 60 macro or Tokina 10-17 fisheye lens.

Recently, I became captivated with blackwater diving which involves night diving where divers are taken far offshore over deep oceanic water.

When you are on a blackwater dive, you can't tell which is up, down, left, or right. Oftentimes on blackwater dives, I wonder why my bubbles are going straight down and if I am caught in some horrible down current, only to realize I am upside down. Excellent buoyancy is a must! Trying to focus on tiny creatures adds to the degree of difficulty. When I saw this nudibranch, I had no idea what it was. I just knew it was small, about 15mm long and it loved to swim erratically. Never in my wildest dreams did I think I would be able to combine blackwater diving and my love for nudibranchs.

Send Todd email at aki340@sbcglobal.net

Attention all you Sluggers, and you know who you are!

The NSSI 2nd edition is available in ebook PDF and book form . The hard back version will become available Nov. 1st. Both will cost $65 (individually).

You will need to jump through a few hoops to get the electronic version as pdf distribution is protected by Adobe ID!! Please read the following to enable reading your electronic purchase!

This new 2nd Edition is updated and reorganized, including 185 new species. Among other features, the new edition includes additional photographs of species, an identification key, and an up-to-date classification reflecting the latest evolutionary relationships. The Indo-Pacific represents the largest expanse of tropical ocean in the world, stretching from the Indian Ocean coast of southern Africa and the Red Sea to the central Pacific of the Hawaiian Islands, Easter Island and the Marquesas.

This region supports the most diverse marine fauna of any place in the world for most groups of marine organisms.

2,138 Indo-Pacific nudibranchs and sea slugs, including many undescribed species.

From left to right, Terry Gosliner, Angel Valdes, Dave Behrens La Jolla, Calif.

Send Dave email at davidwbehrens@gmail.com

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