Hornera versus Stigmatoechos

Hornera (the images to the left) and Stigmatoechos (the images to the right) are genera that can be difficult-ish to distinguish. Both form robust, erect colonies that have a distinct frontal and basal side.

A photo collage of four electron microscope images. The pictures on the left show Hornera and the pictures on the right show Stigmatoechos​
The upper left image: Hornera. The upper right image: Stigmatoechos. The image down to the left: The brood chamber/gonozooid of Hornera. The image down to the right: The brood chamber/gonozooid of Stigmatoechos. Photos: Mali H. Ramsfjell.

However, there are some features that distinguish them. Among other things, you will see pores on the frontal side of the Hornera colonies, and you will also be able to see (this can sometimes be unclear) longitudinal striations on the frontal side of the colony. Stigmatoechos does not have these small pores, and the colony usually has a smoother texture.

A third difference is the location of the brood chamber/gonozooid. In Hornera, it is located at the basal side of the colony (the image down to the left), while in Stigmatoechos, the gonozooid can develop on the basal surface, but also on the lateral and even the frontal surface of the colony (the image down to the right).

By Mali Hamre Ramsfjell
Published Oct. 3, 2025 3:05 PM - Last modified Oct. 3, 2025 3:05 PM
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