Allenbatrachus grunniens

Allenbatrachus: named for fisheries biologist George Allen (1923-2011) from Humboldt State University (California, USA) in combination with the Greek bátrakhos (Gr. βᾰ́τρᾰχος), meaning 'frog', and an early generic term for toadfishes.

grunniens: Latin term for 'grunting', presumably in reference to this species' ability to produce audible sounds when disturbed.

Type locality is given simply as 'East Indies', and this species is currently accepted to range eastwards from the Ganges River delta in India and Bangladesh around the coastlines of Myanmar, Thailand, Malaysia, Cambodia, Vietnam, and the Philippines.

A similar-looking fish from the Western Indian Ocean, including Madagascar and Réunion and previously considerded conspecific with A. grunniens, was described as A. meridionalis in 2004.

Although this species is euryhaline it rarely does well when maintained in freshwater for prolonged periods

This species is relatively common in the aquarium hobby but contrary to popular belief is not venomous in any way. The dorsal and opercular spines can pierce the skin, however, meaning extreme caution is necessary when netting it or performing aquarium maintenance.

It's known by several english names including 'freshwater lionfish', and 'grunting toadfish', with the latter in reference to the fact that it can produce audible sounds when disturbed, especially if removed from the water.

It's often confused with the related species Batrachomoeus trispinosus

The genus Allenbatrachus was erected in 1997 to accommodate 2 species with confusing taxonomic histories, A. grunniens and A. reticulatus, that could not be placed in any other toadfish genus that existed at the time. A third species, A. meridionalis, was added in 2004.

A. grunniens can be told apart from A. reticulatus by: possession of 3 main, irregular, dark blotches on the body (vs. 4 in A. reticulatus); teeth sharp and pointed (vs. rounded); anterior orbital cirrus simple with pointed tip (vs. 4 or more with rounded tips); posterior orbital cirrus with two or more pointed tips (vs. 5 or more rounded tips); largest barbel at end of maxilla with two or more pointed tips (vs. 5 or more rounded tips).

It can be distinguished from A. meridionalis by: anterior and posterior oribital cirri present (vs. single simple orbital cirrus with a pointed tip); largest barbel at end of maxilla with two or more pointed tips (vs. simple and pointed); 16-17 anal-fin rays (vs. 19); usually 19 dorsal-fin rays (vs. usually 22).

The combination of characters distinguishing Allenbatrachus from other genera in the subfamily Halophryninae (see below) is as follows: body completely naked; maxillary flaps absent; axillary foramen or pocket absent; 2 subopercular spines and 1 filament present; supraorbital tentacles present; gill opening at or below pectoral-fin base; eye diameter less than snout length; interorbital width greater than eye diameter; head relatively pointed and flattened with lower jaw protruding; epaxial trunk musculature covers entire dorsocranium; a foramen on each side of neurocranium behind eyes bordering sphenotic and frontal bones; accessory upper pectoral-fin radial completely ossified.

The family Batrachoididae is the only family in the order Batrachoidiformes of which members are mostly distributed in marine and brackish waters with a handful of purely freshwater species in South America.

They're often referred to as 'frogfishes' or 'toadfishes' and share certain characters in that the head tends to be broad and flattened with eyes on top, mouth large with barbels or flaps of skin around it, and body tapering. Although most species have spines on the opercle, in the first dorsal-fin, and often on the subopercle, the majority are non-venomous.

They tend to inhabit shorelines where they conceal themselves within the substrate, among rocks or corals and are ambush predators feeding on both invertebrates and other fishes.

The Batrachoididae is often split into four subfamilies following Greenfield et al. (2008), and these can be distinguished as follows:

Porichthyinae contains just two genera which are characterised by: canine teeth present; 2 solid dorsal-fin spines with no venom glands present; subopercular spines absent.

Thalassophryninae also contains two genera which are characterised by: 2 dorsal-fin spines present; subopercular spines absent; hollow dorsal and opercular spines connected to venom glands present. This grouping includes the freshwater 'prehistoric monster fish', Thalassophryne amazonica.

Batrachoidinae earlier contained all other genera but was split into 'Old World' and 'New World' clades by Greenfield et al. (2008) based on the results of their phylogenetic analysis. It currently represents the 'New World' grouping and contains 6 genera occurring only in the Americas with the exception of the species Batrachoides liberiensis, native to western Africa.

Diagnostic characters are: 3 solid dorsal-fin spines present; 1-3 subopercular spines present; hollow dorsal and preopercular spines plus associated venom glands absent; photophores absent; canine teeth absent; foramina in median process of pelvic bone present; median process of pelvic bone connected to pelvic bone along its entire length; upper accesory pectoral-fin radial fully ossified; medial suture between the epihyal and ceratohyal; ventral edge of cratohyal rounded where it joins epihyal; dorsal side of joint between dentary and articular about equal height and rounded; dorsal edge of quadrate flat all the way across where it meets the metapterygoid.

Halophryninae represents the 'Old World' clade of Greenfield et al. (2008) and contains all remaining genera, including Allenbatrachus.

They are characterised by: 3 solid dorsal-fin spines present; 1-2 subopercular spines with 1-3 filaments; hollow dorsal and preopercular spines plus associated venom glands absent; photophores absent; canine teeth absent; foramina in median process of pelvic bone present; median process of pelvic bone not connected to pelvic bone along its entire length; ventral edge of cratohyal square where it joins epihyal; dorsal edge of quadrate not flat all the way across where it meets the metapterygoid.