Giant Siphonophore (Praya species)

By The Marine Detective on May 12, 2017

[Original post May 2017. Updated March 2022 (photos added at end).]

Here’s another fabulously unique jelly-like drifter for you. It’s a “Giant Siphonophore” which can be up to 50 metres long. That’s right – 50 metres – albeit the sightings near the surface are usually much smaller like those I have seen in the area of Port Hardy (around 2 to 3 meters).

They are not usually common off the coast of British Columbia but, like the recent sightings of many pyrosomes, their presence indicates that there must be warmer waters. They are regulars off the coast of central California.

Siphonophore jellies are so remarkable. While they appear to be a single animal, they are a colony of individuals (“zooids”) with very specialized jobs. The paired bells aid the propulsion of the colony (pneumatophores).  The units of the long stem are known as “cormidia”. Can you discern the individual units in the image below? Each of these segments has parts for reproduction (gonozooids), catching prey and digestion (gastrozooids), and defence (dactylozooids) by having stinging cells (nematocysts). While this species does deliver a bit of a sting to its prey, it packs no where near the punch of the most well-known siphonophore – the Portuguese Man o’ War.

What had me quite confused when I first saw the species, is that Giant Siphonophores often do not have the swimming bells – just the stem of individuals. The bells apparently have a role in reproduction (and are known as eudoxids) but cannot regenerate the whole colony. (Added bonus to this blog – more words for the next time you play Scrabble!)

In what little information I could find on this species, there was this fabulously, dramatic descriptor: “The giant gelatinous predator moves silently through cold, dark waters, propelled by a pair of expanding and contracting swimming bells. Its rope-like body is actually a colony of almost a thousand individual subsections, each performing a specific task. Some provide propulsion, others, reproductive functions; but most specialize in capturing and devouring prey. When hunting, these sections deploy thousands of slender, stinging tentacles to capture drifting krill, copepods, small fish, and other jellies. Almost anything blundering into this deadly net of tentacles soon finds itself stuffed into the nearest waiting mouth.” (Source: The Ecology Center).

And just in case this all is not fascinating enough, the species is also bioluminescent. It produces a bright blue light when disturbed, briefly illuminating our dark, mysterious, life-sustaining sea.

Sources:

• • Dunn, Casey – Siphonophore Lifecycle 
  • Ecology Center – “The Deep Next Door”
  • Jellies Zone – Praya
  • Siphonophores 
    • www.siphonophores.org/SiphLifeCycle.php
    • www.siphonophores.org/colonydevelopment.php
  • Monterey Bay Aquarium – Giant Siphonophore
    
    

    My reporting on a sighting of a Giant Siphonophore back in February 2017 off BC’s Central Coast.

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Update April 2020
See below for a GIANT Giant Siphonophore off the coast of Western Australia at a depth of 630 metres. It’s a different genus. The colony is feeding and its size is estimated to be 47 metres long (154 feet).

Update March 2022 – Two Giant Siphonophores near Port Hardy with dive buddy Jacqui Engel.