I've shown a few sea spiders (also known as pycnogonids) on this blog, but this is the first post about Tanystylum californicum. Eric spotted this individual earlier in December. It's <5 mm across (including the legs).
Here's a closer view. Although this sea spider was small, Eric could tell it looked "spiky" even before looking through a microscope:
If you look closely in the photo above, you might notice some white clusters underneath the sea spider. Flipping the sea spider over revealed that this was a male.
In the photo below, note the three white clusters of embryos. In most pycnogonids, there is paternal brood care (unusual for marine invertebrates) — males carry and take care of the developing embryos:
Look for the special hook-like appendage, called an oviger, that holds the embryos. (There are two ovigers, but one is hidden below the embryos.)
And note that the three different embryo clusters are in different stages of development. The whitest, opaque cluster (on the left) is the youngest; the cluster with embryos showing tiny red eye spots is further along (on the upper right); and the lowest cluster is the oldest, with larvae hatching!
Here's a zoomed in view of a couple of larvae (called protonymphons) crawling on the outside of the embryo cluster:
The larvae were tiny, but here's a close-up of one. Note the fairly substantial claws (chelifores) pointing downward. Sea spider larvae will undergo many molts before they look like the adults!
To see some of the previous posts about sea spiders, check out "One of Joel's old friends'" on 13 January 2014; "Different mates" on 27 February 2014; and "Along came a sea spider" on 15 May 2013.