One of the cutest fish ever – a juvenile in the genus Naso (surgeonfish family)
Ned went diving last month in Palau, a destination we had long wanted to visit. I had to change plans at the last minute and stay home with my parents so I missed out on the trip but we are counting Ned’s visit as a recon for a future visit when we can both go. This week on Blenny Watcher we share some of my favorite images from his visit. They range from a speck of an algae shrimp to… a shark! Yes, here on Blennywatcher, a shark photo by Ned DeLoach, but don’t get too excited – he took it with his 60 mm macro lens.
Humphead Wrasse (Cheilinus undulatus) making a close pass
Always on the watch for behavior: Bluestriped Cleaner Wrasse clean a Barramundi
A pelagic ctenophore, captured during an open water night drift dive
A half-inch Cave Pygmygoby (Trimma taylori)
And Palau has itty bitty stuff too, like this algae shrimp – the size of a flax seed.
Arrowhead Soapfish (Belonoperca chabanaudi)
OK, for the record, a shark picture taken by Ned (but he used his 60mm macro lens)
Not much chance for this sea pen to escape (video frame)
A few months ago I posted about Carry Crabs, little crabs of the family Dorippidae that have modified back legs that they use to grip things, living or inanimate, to disguise themselves. Carry Crabs don’t appear to be fussy – one of the first I ever saw was carrying a live nudibranch. Anyway, my Carry Crab post included this screen capture of a crab toting an unlucky sea pen and I have to say that I think being uprooted and hauled around as camouflage by some upstart crab has to be the ultimate insult (video at the end of this post).
While looking at that video, I also ran across some of another sea pen under siege by hungry Armina nudibranchs That was interesting because the sea pen seemed to uproot itself and start rolling, presumably to escape from the onslaught. I decided to read up a little about sea pens.
While the Arminas were feeding on the sea pen, it uprooted itself and began rocking (video frame)
Sea Pens, a.k.a., Sea Feathers, are octocorals in the order Pennatulacea. Octocorals are made up of colonial polyps and in the case of the sea pen, the polyps are specialized, for example, the primary polyp develops into the stalk with a bulbous holdfast or root that it buries to anchor it into the soft bottom. If you want a good overview of sea pens, check out the PLOS One open access publication, “The Global Diversity of Sea Pens (Cnidaria: Octocorallia: Pennatulacea)” by Gary Williams, where you can read all about their distribution and read some interesting historical accounts about their natural history. There, I also learned that they are bioluminescent and that the Romans referred to them as “Mentula alata” (winged penis) – always good to know things like this for dive boat chitchat.
This sea pen was a porcelain crab condo!
I plead guilty to giving sea pens no more than a passing glance to look for little crabs and shrimp that live symbiotically with some of them, but intend to spend more time looking at them on my next dives. Here, posted to our YouTube BlennyWatcher Channel, is my collection of sea pen observations, including some spawning:
Seeing the Shorthead Blenny’s eyes rotate backward is one thing – getting the shot was another!
And a double take is just what I did when the big round eyes of this Shorthead Blenny rolled onto Ned’s laptop screen. Something wasn’t quite right with the picture so I took a second look and the image fell into place: The tiny blenny’s googly eyes were rotated backwards staring directly behind the fish’s head at Ned’s approaching camera port—a vision of visual dexterity that would make any blenny lover proud.
Ned was photographing this Shorthead Blenny when he saw its eyes rotate backward.
Ned’s preoccupation with backward focused blenny eyes began when he found the Shorthead Blenny (Emblemariopsis bottomei) living within the grooves of a helmet-sized brain coral growing on the side of a large concrete mooring block. I knew Ned was hung up on something. Each time I swam past the block where he was working, his body was contorted, sometimes to extremes; once I saw him standing on his head (well, floating upside down) with his eye still pasted to the viewfinder. However, persistence paid. Three dives and something like four hours later, bingo, everything fell into place.
Shorthead Blenny, Emblemariopsis bottomei from Bonaire
The photo above is a Shorthead Blenny, which we think is a male. A few weeks ago, in our Bonaire Blenny Challenge Week 3, I posted a male in its nuptial colors labeled as Emblemariopsis sp. that Dr. Ben Victor has since identified it as E. bottomei. From Ben: “All the Emblemariopsis in Bonaire are E. bottomei…Females and juveniles with a spike, males without and clear to black.” I’m posting the nuptial male again below, for comparison to how very different it looks from juveniles, females and non-courting males of its species. Thanks to Ned’s photo of the amazing rotating eyes, I spent a lot more time watching these tiny fish during our Bonaire stay.
Two Mimic Fliefish and one Black Saddled Toby – can you tell which is which?
More fascinating mimicry: the filefish and the puffer. The little Mimic Filefish, Paraluteres prionurus not only looks like the toxic Black Saddled Toby, Canthigaster valentini, it is often found swimming around in tight little mixed groups of both species. When I started looking for the filefish, they turned out to be more common than I thought and I realized I had likely been seeing them all along but had been lumping them in with tobies. This is an example of Batesian mimicry in which a palatable species, the filefish, mimics a toxic species, the toby, which has tetradotoxin in its skin and other tissues. As a side note, I don’t know that all toby species are unpalatable to all predators because we have witnessed more than one being snarfed down by a lizardfish. So how to tell them apart? Let’s cover the easy identification clues first.
The extended dorsal spine, just behind the eyes, is an ID clue for the Mimic Filefish
Filefishes have an elongate dorsal spine that can be raised and lowered, so if you can catch the fleeting moment when the fish raises the spine, you have your filefish. The above photo was taken during courting or a dispute, we couldn’t tell which, and the fish extended its the dorsal spine numerous times in the course of the chase.
Whoa – puffy! During an extended battle, this toby puffed up twice (video frame capture)
The Black Saddled Toby is a member of the pufferfish family, Tetraodontidae, so a puffed up fish is a pretty good clue. They swell by rapidly drawing in water, but I can count on one hand the number of times I have seen a swollen pufferfish of any species. While this is a helpful clue on the rare occasion that it is encountered, what about all those other tobies and mimics swimming around together?How to tell them apart? Fins – look at their fins!
On the toby, The dorsal & anal fins start way back (video frame capture)
The toby’s dorsal and anal fins start well back toward the tail as marked in the above video frame capture.
The dorsal and anal fins of the Mimic Filefish start much closer to the head.
The filefish’s dorsal and anal fins are more elongate, starting behind the eyes, about mid-body, and extending almost to the tail as marked in the above photo.
There are a few other identification clues. For example, male Black Saddled Tobies have blue, lined markings behind their eyes and mature (male?) Mimic Filefish have tiny spines at the base of their tails. But color patterns can vary and spines can be difficult to discern on a moving fish, so go with the fins. Want to see them in action and test your mastery of these identification clues? Check out this video from our BlennyWatcher YouTube channel. Side note: check out the scene where the toby puffs up and watch how quickly it expels the ingested water when it deflates: