Colomesus psittacus

Colomesus: from the Ancient Greek χωλóς (cholós), meaning 'physically defective, crippled', and μέσος (mésos), meaning 'middle', presumably in reference to the frontal bones being narrowed, not connected to the orbit, and with the elongated postfrontals connected to the prefrontals (see Gill 1884, also note misspelling of χωλóς as Κολoς).

psittacus: from the Ancient Greek ψιττακός (psittakós), meaning 'parrot', persumably in reference to this species' beak-like mouthparts.

This species' known range extends eastwards from the Parque Nacional Natural Tayrona in Magdalena Department, Colombia, across northern Venezuela, the Gulf of Paria and Orinoco Delta, then southwards via the Guyanas and past the mouth of the Amazon, with the southernmost records from Sergipe state in northeastern Brazil. It is also known from Trinidad and Tobago and Caribbean islands including the Greater Antilles, Lesser Antilles, and Bahamas.

Records from the middle and upper Amazon basins appear to represent misidentifications of the congener C. asellus.

Type locality is given in error as 'Indian Ocean'.

Although it does penetrate the lower basins of rivers, particularly the Amazon where it has been collected from the rio Xingu several hundred kilometres from its mouth, this species is predominantly an inhabitant of mangrove swamps, estuaries, and other such saline habitats.

It is particularly common in tidal channels, shallow inshore lagoons, and the lower reaches of rivers.

An aquarium measuring 180 ∗ 60 ∗ 60 cm72 ∗ 24 ∗ 24 in is suggested as a bare minimum, but even this may prove too small for long-term care.

Choice of décor is not especially critical though it should be maintained in a well-decorated set-up, perhaps containing some driftwood roots or branches in order to mimic its natural mangrove habitats.

It is intolerant of organic waste and require spotless water in order to thrive. Moderate levels of dissolved oxygen and water movement are also recommended, meaning additional powerheads, pumps, etc., should be employed as necessary. A linear flow pump may prove a useful addition, while weekly water changes of 30-50% should be considered mandatory.

Wild examples can be delicate and sensitive to white spot/ich post-import, so a lengthy quarantine period may be required. Maintenance in pure freshwater may also present problems, so the addition of marine salt to a standard gravity of ≥1.010 is recommended.

Chiefly carnivorous and feeds almost exclusively on molluscs and crustaceans such as Cirripedia (barnacles) and Brachyuran crabs, taking increasingly mobile prey as it matures. There is also evidence to suggest seasonal changes in diet, with crabs favoured during drier periods.

In the aquarium offer unshelled crab legs, cockles, mussels, prawns, etc. Tetraodontids lack true teeth, the jawbone itself being modified into four fused toothlike structures. These grow continuously at a surprising rate, so such a diet is essential in order to maintain them at a reasonable length.

Juveniles apparently form loose aggregations in the wild, but in the confines of an aquarium this species is likely to prove aggressive in all but the largest systems.

Unknown.

Unrecorded.

This species is also referred to as 'parrot puffer' in the ornamental trade, although it is not a popular aquarium fish.

Within the genus Colomesus, it can be immediately identified from congeners by its larger adult size, possession of 17-19 (vs. 13-16) pectoral-fin rays, presence of 6 (vs. 5) transverse dark bands dorsally on the body, and predominantly brackish, coastal (vs. freshwater, fluvial) ecology.

Tetraodontids are commonly referred to as 'puffers' due to the ability of many species to inflate their body to an enormous size when stressed or threatened. This is achieved by drawing water into a specialised ventral diverticulum of the stomach, although air can also be used if the fish is removed from the water. As a result of these morphological adaptations puffers swim via a unique combination of pectoral and median fin undulations referred to as 'diodontiform' swimming. They are also able to produce sounds by grinding the jaw/pharyngeal teeth or vibrating the swim bladder. Puffers are secondary freshwater fishes, with the majority of members exclusively inhabiting marine environments.

Other defining characters of tetraodontids include a tough skin usually covered with small spines, a beak-like dental plate divided by a median suture, a reduced gill opening anterior to the pectoral-fin base, no pelvic fins or spinous fin rays, typically short-based dorsal and anal fins, and no ribs.

Puffer flesh is toxic and can cause clinical poisoning and human mortality, although it is regarded as a delicacy in certain countries. The predominant toxin, usually either tetrodotoxin or saxitoxin, is dependant on species, geographic area, and time of year. The toxins are not produced by the fishes themselves, but by bacteria living in symbiotic association, or they are acquired via the food chain. Colomesus species accumulate saxitoxin, although it is unclear whether eating their flesh represents a danger to humans.