Arothron multilineatus is a new species of large pufferfish that has just been described from Japanese caught specimens. The new pufferfish species is most closely related to the starry puffer, Arothron stellatus, but it is easily distinguished by a network of thin lines along the length of the body.
As a juvenile the new Arothron multilineatus could easily be mistaken for a map puffer, Arothron mappa. But the taxonomists who described the new large multilined pufferfish state that it doesn’t have the same network of radiating lines around the eyes as in the map puffer.
The holotype and paratypes specimens of Arothron multilineatus were all around 50cm, 20 inches long. We’re not sure how a fish that grows up nearly two feet long could have gone unnoticed for so long, and the kicker is that this species is not even restricted to Japan! Further investigation has revealed underwater photographs of this fish from all over the Indo West Pacific and even as far as the Red Sea.
Interestingly, the appearance of the new species in underwater photographs is not exactly consistent. In the image below, the specimen from Japan has a bright white belly, slightly reticulated stripes on the body and a spotted tail fin. Meanwhile in the image of the same species from the Red Sea the specimen has much more consistent and thinner stripes that extend all the way to the tail fin.
The discrepancy could be due to regional variation but the description of Arothron multilineatus doesn’t include any genetic analysis. Without genetics to confirm the identity of this species, and its relationship to other pufferfish in the Arothron genus, it’s possible that we could be dealing with a regularly occurring hybrid.
Further research may reveal that like Amphiprion thielli, the new multilined pufferfish is not a valid species at all, but only time will tell. Arothron multilineatus is described by Keiichi Matsuura in Ichthyological Research.