Plectorhinchus gibbosus – Harry hotlips talks!

Sometimes things take time. It took me a while to identify this fish, and even longer to write about it. It probably took also a while to find it, since it mimics a leaf in very shallow water. The parents hide in plain sight, as they look rather unspectacular…

It is always challenging to find an animal on Google when you have no idea what you are looking for. So I searched for ‘brown fish that looks like a leaf ‘, and found Monocirrhus polyacanthus, the South American Leaf Fish. It looks very similar to mine. I also couldn’t get too close to my suspect, so I didn’t have many details. Of course a fish from South America is unlikely to be found in the Maldives, but not impossible as well. But impossible it is, since Monocirrhus is a freshwater fish. I got stuck here and kept finding that wrong freshwater fish..

Juvenile Orbicular Batfish (Platax orbicularis) look like leaves too, but yet very different from mine. Same is true for the Leaf Scorpionfish (Taenianotus triacanthus), which I have seen many times. And there I got stuck again. This brown fish floating at the beach was difficult to identify!

Until I saw a photo of a juvenile ‘Harry hotlips’. It was labelled as Brown sweetlips, and that made sense to me. Juvenile sweetlips are famous for their mimic behaviour. Juvenile Harlequin sweetlips, P. chaetodonoides, are brownish with white spots, Oriental sweetlips, P. vittatus, are black and white with some yellow. And both juveniles mimic swimming, poisonous flatworms for their protection. They can be found in reefs, somewhere between 5 and 30m deep is where I saw them. I have assumed, that all Plectorhinchus mimic flatworms. At least P. lessonii, polytaenia, albovitattus, lineatus, diagrammus, picus, gaternius share a similar appearance like vittatus and chaetodonoides. Do they all do the worm mimicry? P. picus and albovitattus juveniles can be seen swimming wiggly worm-like on YouTube, the others are hard to find, also because Harlequin and Oriental sweetlips are very popular amongst divers and there’reso many videos…

Plectorhinchus caeruleonothus looks a bit more like gibbosus, but still with fine lines. P. cinctus juveniles look more leaf-ish (hehe), and in fact P. cinctus and gibbosus seem to be closely related (see ‘Plectorhinchus makranensis (Teleostei, Haemulidae), a new species of sweetlips from the Persian Gulf and the Gulf of Oman’). Whether P. cinctus does leaf mimicry I don’t know. Quite interesting how different juveniles from one genus behave!

Plectorhinchus gibbosus belongs to the family Haemulidae, with two subfamilies: Haemulinae, the grunters or grunts, and Plectorhinchinae, the sweetlips. There are between 130 and 145 species, depending on the source. 35 species belong to the genus Plectorhinchus.

Sweetlips are called so because of their thick lips, and grunts are known to grunt. Being so closely related is a good hint that sweetlips are also able to produce sounds. Seahorses are known to do so, hermit crabs do it, but take this:

There is a growing number of research done on fish sounds. The website* conviently collects this data, and this is where I found our Brown Sweetlips mentioned. I couldn’t get access to the paper, but I contacted the author (unsuccessfully). Fishsounds lists 1227 species of fish known to produce sound! There is a very early French paper on fish sound from 1874, and ‘Sounds of western North Atlantic fishes; a reference file of biological underwater sounds’ was published by Marie Poland Fish (really her name!) and William Mowbray in 1970.

Knowledge about the audio system of fishes will be of great help to understand their biology better. I wouldn’t be surprised if we eventually find out that the entire reefs communicated. Imagine the effect of boat traffic on this.

If anyone has an idea how the Brown sweetlips came to it’s common name Harry hotlips, please let me know!

*Looby A, Vela S, Cox K, Riera A, Spriel B, Davies HL, Bravo S, Rountree R, Juanes F, Reynolds LK, Martin CW. 2024. FishSounds., version 2.2.