It seems that every one of Anna’s and my favorite photos comes with a story attached. Our encounter with a night-prowling lobster is one of my favorites. It took place a few years back in Lembeh Strait, Indonesia where we were spending most of our time diving after dark searching for new crabs and other critters to include in Reef Creature Identification—Tropical Pacific.
Our guide, Liberty Tukunang, and I slipped away from Anna and her bug-buzzing video lights to explore the sand that extended from the reef where our boat—a long, low, green and yellow water taxi made of wood—bobbed 20 feet above. We hadn’t gone far before Anna’s beam waved us back. Returning, we found her staring down a lobster the size of Manhattan that happened to be a species we had been hunting for a long time – Panulirus ornatus, the Ornate Spiny Lobster. Our sudden arrival sent the lobster racing off into the night with Liberty and me on its tail.
But the beast was a thoroughbred. As hard as I kicked I couldn’t keep up with six jointed legs, built for the terrain. Just as I thought all was lost, Liberty, with a burst of speed, drew even and plunged his stainless steel stick into the sand. The lobster was stopped in its tracks. My momentum carried me around and, for a few brief seconds, face-to-face with a face epitomizing the unintended artistry of natural selection.
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:
At a snail’s pace: these tiny chanks took as long to hatch as you might expect (video frame capture)
This will likely not excite any but the anoraks amongst us: Last week in Utila, I witnessed hatching West Indian Chanks (I was excited) and I can report that they are as slow when hatching as they are as adults moving across the sand. Although the word chank is often used interchangeably with conch, chanks are gastropods belonging to the family Turbinellidae, while true conchs are in the family Strombidae. Over the years, we have received several inquires about a strange object, usually found attached to a gorgonian, that looks sort of like a vent hose from a clothes dryer. They are the egg cases of the West Indian Chank, Turbinella angulata, and while I have seen quite a few, I have never seen them unattached.
Egg Case of the West Indian Chank (video frame capture)
Look closely, you can even see the tiny eyes of the hatching chank (video frame capture)
We were diving in a large grass bed, just off a shallow reef, surveying fish for REEF, when I saw an egg case rolling around in the sand just under the boat. The strong winds and heavy seas all week may have contributed to the separation of the egg cases (I saw several) from their holdfasts – or maybe the shells growing inside became too heavy, causing them to tear away – who knows? Anyway, I showed it to a couple of divers and moved on to continue my fish count. Near the end of the dive, I returned to the one under the boat and saw that some of the tiny mollusks had moved, so I settled in to watch several of them crawl out of the protection of their egg case. Watch the video below, or on our BlennyWatcher YouTube channel. ~ Anna DeLoach
Photo Friday: Activity is the challenge this week. Our favorite activity underwater is “critter hunting” – the search for unusual fish and invertebrates. Finding cool critters like this crocodile fish above and the rare melibe nudibranch below are what keep us diving.
When disturbed, the melibe swam in a writhing motion.