Masked Puffer

Arothron diadematus (Rüppell, 1829)

syn. Tetraodon diadematus

30 cm1-20 mRed Sea endemicPoisonousLeast Concern

988

The most familiar puffer on this coast may not be a species of its own. FishBase records it as very closely related to the Indo-Pacific blackspotted puffer, Arothron nigropunctatus, and notes that some authors treat the two as one animal. What separates them is the mouth of this sea. The masked puffer is recorded from the 🌊 Red Sea and nowhere else; the blackspotted one holds the rest of the Indo-Pacific, from East Africa to the Pacific islands, and comes in gray, yellow and blue-gray forms. Where one ends the other begins, and they meet nowhere.

What you see is an olive-gray fish about 30 cm long with a black mask laid across the eyes and over the snout, a dark blotch at the base of each pectoral fin, hanging over coral-rich reef by itself and sculling gently with those pectorals. It has no pelvic fins at all and it is in no hurry, which is the surest sign that nothing is hunting it.

Tetrodotoxin blocks the sodium channels that nerves use to fire. A dose measured in milligrams paralyzes an adult, working inward from the face while the person stays conscious, and there is no antidote: treatment is to keep the patient breathing on a machine until the toxin clears. It is among the most potent poisons in the natural world.

The fish does not make it. Bacteria do, and they arrive with what the puffer eats, so the toxin is accumulated and concentrated rather than produced. Puffers raised in captivity on clean feed end up almost free of it, and become toxic again on a wild diet. The fish is a container.

Which is why this is a poison and not a weapon. Nothing is going to be envenomated by a masked puffer. The danger is entirely in eating one, and cooking does not destroy it.

The species. Arothron diadematus (Rüppell 1829) - crowned. ETYFish

How to recognise it

black mask across the eyes and over the snout, on an otherwise olive-gray fish
dark blotch at the base of the pectoral fin
no scales and no pelvic fins; sculls slowly with the pectorals
hangs over coral-rich reef by itself, in no hurry
up to 30 cm

Why it's threatened

Residential & commercial development

Housing & urban areas · Commercial & industrial areas · Tourism & recreation areas

Biological resource use

Intentional use: (subsistence/small scale) [harvest]

Pollution

Sewage · Run-off · Type Unknown/Unrecorded · Oil spills · Seepage from mining · Nutrient loads · Soil erosion, sedimentation · Herbicides and pesticides · Garbage & solid waste

Climate change & severe weather

Habitat shifting & alteration · Temperature extremes

There have been no confirmed population declines in A. diadematus. However, because of its affinity with coral reefs, we infer that A. diadematus may be experiencing population declines due to habitat loss in parts of its range.

In the Red Sea, which includes 17,640 km2 of coral reef area, 4% of the reefs have been effectively lost (90% mortality), while another 4% are at a critical stage with 50–90% loss of coral cover as of 2008 (Wilkinson et al. 2008).

In Egypt, coastal development to accommodate expanding tourism, which includes road construction and the discharging of waste from desalination, sewage, and wastewater treatment plants, as well as beach replenishment, increasing fishery, and the production of trash and pollutants, has negatively affected some reefs (Heisse et al. 2005). Additionally, physical damage to corals directly caused by recreational human activities is significant on some reefs (Jameson et al. 1999). As of 2008, the status of coral reefs and coral communities in the Red Sea and Gulf of Aden was generally good, with coral cover averaging 30–50%. However pressures from major development for mass tourism and industrialization, over-exploitation and destructive fishing in poorly managed fisheries, Crown-of-Thorns outbreaks, and bleaching events are expected to increase (Kotb et al. 2004).

Arothron diadematus is targeted by collectors for the marine aquarium trade in Egypt, Yemen, and Saudi Arabia, and is of moderate value. Collection pressure is expected to continue to increase. Although there have been no recorded decreases in the abundance of this species, marked decreases in the abundance of other targeted species have been observed on Egyptian reefs from 1997 to 2002 (Kotb et al. 2004).

Threat classification from the IUCN Red List.