22 de enero de 2022

How to pick apart a Gloomy Octopus from a Maori Octopus.

From my time spent diving around SE Australia I became fascinated and endeared to Cephalopods. Always a student of taxonomy I originally struggled to separate some species but over time recognized the key differences between many of the species from there.

Periodically I review Australian Ceph's and where I can, help out with identifications or make corrections. I recently found that there was a bunch of confusion in separating Octopus tetricus and Macroctopus maorum. Two species found both in Australian and New Zealand waters. Seems it is mainly large mature Octopus tetricus that are the most confusing.

The confusion seemed to have been magnified by an erroneous conclusion that they could easily be separated by eye colour alone. IE if the eye was white it must be a Gloomy and if orange it must be a Maori. Here's an example of the confusion in identifying a large Octopus- https://inaturalist.ala.org.au/observations/18928172

To help I've arranged a list of the key differences I look for when separating these 2 species.


Octopus tetricus key diagnostics-
Base skin texture Tessellated(like irregular tiny cobblestones with contrasting mortar).
Colouration is mottled Grey/Beige/Brown/Orange often with mustard highlighting.
Arms often show transverse dark brown banding.
Arms are faced red in varying shades around the suckers.
Eyes are often White with a dark horizontal band when at rest on in den. When active/hunting eye is more likely rusty orange. The orange eye colour coincides when the octopus is showing increased skin papillae activation.
Around the eye skin flaps can be raised all around the eye, Star like.
Skin Papillae when raised are pinched flaps mostly on mantle net and upper arms.

Skin colour and texture- https://inaturalist-open-data.s3.amazonaws.com/photos/175099195/original.jpg
Skin papillae around eye- https://inaturalist-open-data.s3.amazonaws.com/photos/72101071/large.jpg
Classic in den look- https://inaturalist-open-data.s3.amazonaws.com/photos/123955531/large.jpg


Macroctopus maorum key diagnostics-
Base skin texture basically smooth but warty/lumpy or gently wrinkled. Depending on level on skin texture activation.
Base colouration, rust colour. Can switch to pale/sandy or mottled hues depending on terrain. Arms can remain orange hued while net can go pale.
Bright white speckling always apparent on upper arms and netting.
Skin papillae when raised are warty finger like protrusions and mainly on mantle extending down to upper netting .
Single large papillae that can be raised(finger like) above eye.

Base skin colour and texture- https://static.inaturalist.org/photos/90405542/large.jpg
Skin colour blending with light coloured substrate- https://inaturalist-open-data.s3.amazonaws.com/photos/105485107/original.jpg
Example of raised(finger like) papillae on mantle- https://static.inaturalist.org/photos/42486642/large.jpeg

I hope this is of help to anyone trying to get a handle on the two species. Happy for any feedback or discussion.

Regards,
Jim.

Ingresado el 22 de enero de 2022 por jimbobo jimbobo | 4 comentarios | Deja un comentario

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