Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Posts from the ‘Flatfish’ category

What’s With the Flat Face?

Seadate April 11th, 2020, Port McNeill.

Suddenly I realized the bottom of the Ocean was staring at me.

It has happened before and . . . oh how I stared back!

These flatfish or flounders are a particular marvel.

In this case, the species of flounder was a big Rock Sole (Lepidopsetta bilineata up to 58 cm long).

Be sure to read below about the “ba-boing” of their eyes! Yes, I am a scientist but that may not be a fully appreciated scientific descriptor. 🙂

Rock Sole are a “righteye flounder” species. All flounder species start off, when larvae, with eyes on either side of their heads. They are anything but “floundering”. They are astounding adapted for life on the sand. (I include photos of additional NE Pacific flatfish species at the end of this blog).

As the larvae develop, the right or left eye (depending on species) migrates across the top of the head to the other side of the body changing some skull bones in the process. This adaptation “allows flatfish to exploit a common habitat – flat sandy bottoms . . . Many fish avoid this habitat because of the lack of rocks or other features that would provide a hiding place. Flatfish can hide from predators by burrowing [and/or camouflaging], leaving only their eyes above the surface . . . the habitat is home to an abundance of prey such as worms and shrimp. With both eyes on the upper side they can use 3D vision to hunt and detect predators. There has been considerable controversy over the origin of flatfish, but recent discoveries of several fossil intermediate forms show that eye migration evolved gradually some fifty million years ago.” Source: Puget Sound Sea Life.

The series of photos show this metamorphosis (images by Dr. Alexander M. Schreiber):

Also, flatfish change colour to match their surroundings. But how is this possible when their eyes are positioned where they are?

The answer via National Geographic: “All flatfish have eyes on the end of stalks, so they pop out of the head “kind of like the eyes we saw in cartoons—ba-boing!” says George Burgess of the Florida Museum of Natural History. Thanks to those pop-up peepers, “they can’t see the bottom directly underneath them, but they can see the bottom around them,” notes Jackie Cooper of the National Aquarium in Baltimore. Once flatfish eyes get the lay of the land, they message the brain, which in turn sends signals back to the skin. This organ contains color-changing cells such as melanophores, which either expand or contract according to the background the fish is trying to match . ..”

At this time where so many are striving to educate children at home, I want for my blogs like this to be of all the more use.  For example, I am hoping the photos allow for children to reflect “if the fish looks like this, what advantages does that provide” , leading to greater deductive reasoning, connection to life in dark seas, and ultimately the appreciation that organisms are the way they are for a reason i.e. the understanding of adaptations.

More fabulous flatfish faces below.

(Note that  this NOT a comprehensive showing of ALL the flatfish / flounders of the NE Pacific Ocean. Rather, it’s just some of the species I have had the opportunity to photograph.

Some Lefteye Flounder Species
Now more commonly called the “Sand Flounders”
Family Paralichthyidae:

 Pacific Sanddab (Citharichthys sordidus to 41 cm).

Speckled Sanddab (Citharichthys stigmaeus to 17 cm). This one is only about 5 cm long. At first I thought it was an Alder leaf.

Other Righteye Flounder Species
Family Pleuronectidae:

Sand Sole (Psettichthys melanostictus to 63 cm). This little one was only ~2.7 cm. I found this little guy/ gal in a tideline and photographed it in my dive mask. See the blog I wrote about this “find” in my “Plankton Got Sole” item at this link. 

C-O Sole (Pleuronichthys coenosus to 36 cm). This one has more pink colouration than usual as it is living around pink coralline algae. Named the “C-O” Sole for the reverse “C” and an “O” shape on the tail. 

Another C-O Sole to give a sense of the variation in colour. A big dot in the middle of the body is typical in this species. For this individual, you will note it is purple. 

DSC08249Curlfin Sole (Pleuronichthys decurrens to 37 cm)


And more Rock Sole photos because you can never have enough:

Note that the tube worm species here is believed to be an invasive – Chaetopteridae or Spionidae (as shared by expert Leslie Harris).

Same individual as above photo. 

Sources:

Plankton Got Sole!

No, I have not mixed up my spelling of “soul” verses “sole”.

This last weekend, while watching herring feed on krill in a tide line, I suddenly noticed a very small transparent fish.

Upon closer inspection, I saw that it was a larval form of some species of flatfish.

I was able to dip the little guy / gal into my dive mask for a few pictures and, due to the size of the lettering in the mask, I know that the fish was only 2.7 cm.

Planktonic Sand Sole.  Only 2.7 cm. 
Photo: Jackie Hildering

I was in awe of how transparent s/he was; that I could see the bones and heart; and that this small, fragile planktonic stage could ever survive to grow into an adult.

These sorts of “finds” are as awe-inspiring to me as any sighting of a whale. The thick planktonic soup of our rich cold oceans is full of the larvae of so many species. Anemones, nudibranchs, sea stars, crabs, etc. – they all start off as zooplankton and the incidence of what sort of plankton are present often gives scientists an indication of what may be happening with the marine food web.

It is like a world of hidden secrets to me and of course I wanted to find out all I could.

What species of flatfish was this – halibut, sole, flounder?

Photo: Hildering

I do not have the expertise to know but, oh so thankfully, there are those out there willing to share their great knowledge.

Marie-Josée Gagnon of the Salmon Coast Research Station quickly steered me in the right direction, believing it was most likely a species of sole.

She connected me with zooplankton taxonomist  Moira Galbraith of the Institute of Ocean Sciences who confirmed that this was the larval form of a Pacific Sand Sole (Psettichthys melanostictus), a species that can grow to 63 cm. She also shared that the transparency of the larval fish serves as camouflage, reducing the chances of it being eaten before reaching the life stage where it settles to the ocean bottom and hides on and in the sand.

But wait, what are those two little zooplankton guys attached to the larval sole? They are copepods, but what kind of copepod?  What does their presence mean ?  Are they parasitic? And there I go down the marine id rabbit hole. 

One thing I know for sure though – and forgive me for the following pun because the emotion behind it is very sincere – how I hope this little planktonic fish will be a  . . . sole survivor.

Sources:

Update September 30, 2012:

  • This great item by Puget Sound Sea Life has been brought to my attention and includes the following: ” . . . within several days to weeks, depending on the species, the larva undergoes a radical metamorphosis. The right or left eye migrates from it’s normal position across the top of the head to the other side of the body changing some skull bones in the process . . . . After metamorphosis, the fish settles to the bottom on it’s left side, develops skin color on the right side and continues growth as a juvenile.  Adapting a bottom-dwelling life style allows flatfish to exploit a common habitat – flat sandy bottoms which are very common in the subtidal zone. Many fish avoid this habitat because of the lack of rocks or other features that would provide a hiding place. Flatfish can hide from predators by burrowing, leaving only their eyes above the surface. In addition the habitat is home to an abundance of prey such as worms and shrimp. With both eyes on the upper side they can use 3D vision to hunt and detect predators. There has been considerable controversy over the origin of flatfish, but recent discoveries of several fossil intermediate forms show that eye migration evolved gradually some fifty million years ago.”
  • With regard to the ectoparasites on the sand sole larva, Marie-JosĂ©e Gagnon and Moira Galbraith have again been very generous with their knowledge. It is impossible to know the species from my photo but, due to the size, it is likely a recent infection and could be (1) first stage Chalimus; (2) Lepeophtheirus bifidus – which, unlike most parasites of benthic marine species is host specific – only being found on the rock sole or possibly, (3) the isopod Gnathia.   I valued having affirmed too that adults and young live in different environments to eliminate competition for the same resources but also to provide a buffer or separation to prevent transfer of disease or parasites.