What the heck is this transparent fish thingy?

[glazeddonut]

Hey all,

There's probably a better place on the boards to post Fish ID questions, but I saw this thing in Bonaire last week, and thought I'd check here first, to see if someone with local knowledge knew what this was.

So, what the heck is this thing? Transparent, like a jellyfish, but sort-of shaped like a fish, seemed to have something like a mouth at one end, and no apparent tentacles. Sorry for the poor photo...unfortunately the camera battery died before I could get a better pic. Saw about 4-5 of these at Something Special on one of my dives. Didn't see any others the whole trip.

 

[Thalassamania]

I believe it is a salp. Most likely: Thetys vagina. Often seen in chains.

 

[annieols]

hey were you at Bonaire Dive and Adventure?
I think we identified it as a pelagic tunicate.. when i looked into it closer i also thought it was a salp (Salpa maxima looked about right)

I cant figure out how to post a pic on the new Scubaboard, but go to this website and look at the photo labeled fig 2
Johnsen Lab - Research, Tissue Transparency

 

[aquaregia]

Isn't a salp a pelagic tunicate? (And although this isn't my specialty, I also think it looks like a salp)

 

[Thalassamania]

From "The Jellies Zone:"

The salps (Class Thaliacea, Order Salpida) include the most commonly encountered pelagic tunicates. Salps can form massive aggregations of millions of individuals that may play a significant role in marine ecosystems. They exhibit among the fastest growth rates of any multicellular organism. A transparent test encloses the cylindrical body, and may be relatively thick and tough with projections and keels. Using rhythmic contractions of bands of circular muscles within the body wall, movement by jet propulsion is accomplished by regulating the action of sphincter muscles that open and close anterior and posterior openings. This also serves to pump plankton-laden water through the body, where a mucous net is used to extract food particles. The number and pattern of muscle bands is useful in distinguishing species.

Salps exhibit a complex life cycle with alternating aggregate and solitary generations. Aggregates (the sexual gonozooids) develop asexually from an elongating stolon that buds from an area just behind the endostyle of the solitary individuals (the oozooid). Individuals within aggregates are hermaphrodites, typically starting as females that are fertilized by older male individuals from another chain. The resulting embryos (oozooids) then develop into the solitary asexual phase. There is no larval stage and even before release the young oozooid often has a developing stolon. In many species only a single embryo develops within each individual of the aggregate. This method of asexual reproduction enables salps to quickly exploit periods of abundant food with rapid increases in population density. With few defenses, rapid growth to maturity is the primary means to avoid predation by heteropods, jellyfish, siphonophores, ctenophores, sea turtles, marine birds and numerous types of fishes. Hyperiid amphipods and several species of fish also use salps as traveling homes.

 

[glazeddonut]

Yep, after looking at more pictures, and comparing it with what I saw, I'm pretty certain it was a salp. Thanks guys!

 

[aquaregia]

Salps were the coolest thing I'd seen in the water for a long time, until I saw a heteropod.