Callopora craticula vs. lineata

Regarding Callopora

If you collect bryozoans along the Norwegian coast, you can find species belonging to the genus Callopora. This genus has several species, but if you collect material from the sublittoral zone, there are usually two species that often appear together and that appear quite similar: Callopora lineata and Callopora craticula.

These species both have several spines distributed around the entire zooid, they have avicularia, and the zooids do not have that much calcification compared to some other cheilostomes. It can be a bit difficult to tell them apart, but if you have a good stereo microscope, there is a good chance you will be able to do it! Here I present four differences that can be used for separating the two species.

NB: If you are unsure about the details of the traits that I'm mentioning here, you can check out this post

Difference nr. 1: Spines

In Callopora craticula, you will find more spines than in Callopora lineata. Callopora craticula usually has 12-15 spines, while C. lineata usually has 8-11.

Difference nr. 2: The ovicells

This can be difficult to observe, but in Callopora craticula you have an ovicell with a distinct ridge. This ridge is not found in Callopora lineata, but due to an area with less calcification it can sometimes resemble an indistinct ridge.

Difference nr. 3: The avicularia

The mandible of the avicularia in Callopora craticula is more pointed than in Callopora lineata. In addition, the avicularia in C. craticula have a greater tendency to be placed on the ovicell of the zooid below. In addition, the avicularia of Callopora lineata are more rounded.

Difference nr. 4: Zooid size

Callopora lineata zooids are slightly larger than the ones in Callopora craticula, but this can be difficult to judge unless you have the two species side by side.

Reference:
_{Hayward, P.J. & Ryland, J.S. (1998) Cheilostomatous Bryozoa. Part 1. Aeteoidea-Cribilinoidea. Synopses of the British Fauna, 10, 156–165}