Do all parosphromenus species stand on their head when flashing ? – someone asked me the other day at a presentation.

No – they don’t.

It’s a peculiar thing, that most of the paro-species we know do stand head down when flashing, yet we know of 3 species that do the opposite. When the males do their little dance in front of the female they stand head up.

These 3 species are ornaticauda, parvulus from Borneo and sumatranus from Sumatra.

Ornaticauda and parvulus are normally thought of as paro-species that differ from the others paro-species, in not only this way, – but also in bodyshape, size and general demands.

Scientific work by Wentian Shi, shown in this paper, also suggests that parvulus is a very old species, and in a distinct evolution branch from other species, which might explain the difference. (see https://mapress.com/zt/article/view/zootaxa.5060.1.3/45781 )

But sumatranus is different from that , – it reminds of most other species, – as far as we know – except for this one feature with the head-up flashing.

Why the evolution happened like this we don’t know, we can just accept that this is a curious difference between some of the parosphromenus species.

Below photos of the 3 species + one ‘ordinary’ head down flashing species for comparison, P. sp. bintan

Photos 1. Parvulus (credit Helene Schoubye Johansen) 2. Sumatranus (credit David Jones) 3. Ornaticauda (credit Horst Linke) P. sp. bintan (credit H.S.Johansen)