For Eric’s class this summer, he raised the early life stages (larvae) of the Bat Star (Patiria miniata). Eggs and sperm from spawning can be mixed in the laboratory to produce fertilized embryos. Like many marine invertebrates, the fertilized embryos of sea stars develop into a swimming larval stage that looks very different from the adult form. The photo above shows the larval stage (called a brachiolaria) of the Bat Star about 25 days after fertilization. This stage uses cilia to swim through the water as it feeds on phytoplankton.
By about 45 days after fertilization, the juvenile sea star is starting to form at the base of the larval body. In the photo below, the golden-white dome-like section is the developing juvenile body (called the juvenile rudiment), which is already forming its skeleton (made of shiny calcareous plates called ossicles) and its tube feet (that it will use to crawl on the bottom).
Now for the best part. Eric was able to capture some microscope video of the bat stars over the course of their development! In the video below you will see the larvae swimming about at ~25 days (where the pink structure is their stomach), and at ~45 days (with the developing juvenile body clearly visible). In the final video clips from about 50 days, you will see the metamorphosed juveniles walking along the bottom using their first tube feet. These new juveniles are very tiny (< 0.5 mm across)!
[If you can't see the video player in your e-mail, click on the title of the post above to watch the video on the NHBH website.]
You can read more about this amazing process of development
in Bat Stars in some previous posts, "A new star(t)" on 12 August 2013 and "First steps" on 8 August 2017.
P.S. Many thanks to Ellie and Christina for spawning the Bat Stars, and to Eric for the great video!
Thanks for the masterful class! I rarely see bat stars in the wild. Are they in danger or is it because the dwell in the sandy bottom rather than clinging to rocks?
ReplyDeleteHi, Rodolfo!
ReplyDeleteHmmm...Bat Stars tend to be in more wave-sheltered habitats (boulder fields protected from direct wave energy) and their distribution can be patchy, but from our surveys and time in the field it seems like they're doing fine overall. Their visibility does seem to vary year-to-year and day-to-day, so I suppose whether you encounter them can be a bit like fishing -- sometimes you find them, sometimes you don't, but if you keep trying you're likely to encounter them on some days. I think of them in low zone areas in shallow water with a mix of boulders and surfgrass. They can also be in subtidal areas (like kelp forests).
:) Jackie
Thanks for the excellent insight into these beautiful creatures. In the ~45-day stage the larva looked like it was going to turn into a flying squirrel. :)
ReplyDeleteJackie et al, these are amazing! The tiny first tube feet settled bat star is amazing. Thank you for your daily blog. It brings so much joy and information. Josie
ReplyDelete!! I'll admit, I hadn't ever contemplated the similarities between a larval Bat Star and a flying squirrel -- but as soon as John mentioned it and I looked at the photos, I couldn't believe it! Complete with flaps spread and a tail!
ReplyDelete:) Jackie
thank you! Beautiful to sea, I mean see! Right on the heals of last week's presentation. Literally, brought to life.
ReplyDelete