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Sunday, July 23, 2017

Hometown hydromedusa

Last week, Eric's summer students were sorting through some plankton samples collected in Bodega Bay and Bodega Harbor.  Rachel spotted something different and took a closer look.  We're glad she did, because it turned out to be an interesting hydromedusa:

Meet Hydrocoryne bodegensis!  The scientists who first described this species (John Rees, Cadet Hand, and Claudia Mills) named it after Bodega Bay because they collected colonies from one of the Bodega Harbor jetties.  It's always fun to become familiar with local species that have "bodega" in their names!

This hydroid also has a polyp stage that grows attached to the substrate.  The tiny medusae (their bells are only ~1 mm high) develop among the clubbed tentacles of the polyp and then eventually break away to swim in the water column:

Modified from Rees, J.T., C. Hand, and C. Mills.  1976.  The life cycle of Hydrocoryne bodegensis, new species (Coelenterata, Hydrozoa) from California, and a comparison with Hydrocoryne miurensis from Japan.  Wasmann Journal of Biology 34: 108-118.

Although I didn't know it at the time, five years ago I photographed what might be this species, with a medusa just about to swim away:

Eric captured a short video of the Hydrocoryne bodegensis medusa, so I'm including a video file below.  While watching, note the following:

- 4 long tentacles, with visible (knobby) clusters of nematocysts
- each tentacle ends in a prominent rounded cluster of nematocysts (you can locate the end of each tentacle by looking for these rounded tips) 

 - a red ocelli (eye spot) at the base of each tentacle

- dramatic extension and contraction of the tentacles (this is likely a feeding strategy, e.g., increasing surface area to increase likelihood of prey capture)

 And one last view of this beautiful medusa with its tentacles extended:

P.S.  Thanks, Rachel, for spotting a seldom-seen hometown medusa!

1 comment:

Maggie R. said...

So cool! I was imagining that video set to music.