Amphipods: Caprella acanthifera and Pthisica marina

[Rikisub]

2021-10-02-17.52.42 ZS retouched by Rikisub, en Flickr

Two different species of caprellid amphipods together: on the left, Caprella acanthifera; on the right: Pthisica marina. They were on branches of the hidrozoan Obelia dichotoma, several polyps of which may be seen as well. This two amphipods didn't seem to get on well, although they look like they were neighbors...
JML 21 mm and Sony nex - 6. 3x, 20 shots stacked with Zerene.

[MarkSturtevant]

Interesting. I had quite forgotten about Bryozoans, but there is an extensive and important fossil record on them. They can be so abundant, that their populations are used as an indicator of rates of speciation and extinction in the fossil record.