Acanthistius Gill 1862

Acanthistius Gill, 1862: 236

Type-species, Plectropoma serratum Cuvier, 1828, by monotypy).

Diagnosis. Body robust; scales small, ctenoid, those on the head, chest and belly ctenoid or mostly embedded; lateral line complete, tubed scales 48 – 67, not counting several on proximal half of caudal fin, the tubes with 2–5 branches. The scales of Acanthistius ocellatus and A. serratus were described as “cycloid” (Kuiter, 1994), but the lateral body scales of the juvenile of each species that I examined are ctenoid, although the ctenii are very small and mostly covered by skin. Dorsal fin single, with 11–13 spines and 13–18 segmented, branched rays; the fin margin slightly notched before the soft-rayed part; anal fin with 3 spines and 7– 9 segmented, branched rays; caudal fin truncate or convex, with 15 branched, segmented rays; no filamentous or elongated median-fin rays; pectoral fins rounded, with 15–21 rays, most of which are branched and fleshy. Mouth terminal, jaws equal; premaxillae slightly protrusile, maxilla reaches to below rear half of eye; supramaxilla autogenous, well developed, its length about half length of maxilla, hidden by skin on upper rear edge of maxilla. Jaws with inner row or rows of small slender teeth and a few outer teeth enlarged as small canines; vomer and palatines with cardiform teeth; tongue edentate. Opercle with 3 sharp spines posteriorly, but upper and lower spines are mostly hidden by skin and scales; preopercle serrate, with 3 or 4 serrae at angle enlarged and 1–3 large, antrorse spines on ventral edge. Branchiostegal rays 7, the membranes connected to anterior end of isthmus. Lower limb of first gill arch with 13–16 gill-rakers, of which 4–8 are rudiments. Oblong tooth plate on 2nd epibranchial. Anterior nostrils with a fleshy rim, the rear margin enlarged, forming a large flap reaching to or over posterior nostril. Vertebrae 26 (10 abdominal + 16 caudal or 11 abdominal + 15 caudal); 3 supraneural bones: 0/0/0+2/1+1/1/1/1 or 0+0/0/2/1+1/1/1/1/.

Remarks. Plectropoma aculeatum Valenciennes, 1830, was described from a specimen said to have been collected from the "Banc des Aiguilles" [= Agulhas Bank off the south coast of South Africa]. But, according to Boulenger (1895) who examined the holotypes, P. aculeatum is a synonym of Acanthistius brasilianus (Cuvier, 1828), which is endemic to the coast of Brazil (Irigoyen et al., 2008); and the type locality for P. aculeatum is surely in error (Bauchot et al., 1984: 20).

The genus Acanthistius is not clearly defined, and its inclusion within the family Serranidae has recently been questioned (Craig and Hastings, 2007). The genus comprises ten species, occurring in shallow, warmtemperate waters of the Southern Hemisphere: Acanthistius brasilianus (Cuvier), south coast of Brazil; A. cinctus (Günther), Australia, New Zealand, Lord Howe Id, Norfolk Id, and Kermadec Islands; A. fuscus Regan, Easter Id and Sala y Gómez Id; A. ocellatus ( Günther), Australia; A. pardalotus Hutchins, Western Australia; A. patachonicus (Jenyns), Argentina and southern Brazil; A. paxtoni Hutchins & Kuiter, Australia; A. pictus Tschudi, Ecuador, Peru and Chile; A. sebastoides (Castelnau), Namibia and southern Africa; and A. serratus (Cuvier), Australia.

Species of Acanthistius are superficially similar to those of the genus Hypoplectrodes Gill, 1862, which includes the genus Ellerkeldia Whitley, 1927 (Anderson and Heemstra, 1989); species of both genera have a truncate or convex caudal fin, branched pectoral-fin rays, with the middle rays thickened, and 1–3 strong antrorse spines on the ventral edge of the preopercle. Acanthistius species differ in having 11–13 dorsal-fin spines, versus 10 dorsal-fin spines in all Hypoplectrodes species (except H. wilsoni Allen & Moyer (1980) which has 10 or 11 dorsal-fin spines. Kuiter (2004) added the two South African species of Acanthistius, A. joanae and A. sebastoides to the genus Trachypoma, but the type, T. macracanthum, has a smaller head, with dorsal profile slightly concave, eye diameter 2 times interorbital width, and the interorbital area with a median groove.

The first fish to be described from South Africa that may have been a species of Acanthistius was named Serranus cuvierii by Andrew Smith (1831). Smith’s description was published in the South African Quarterly Journal, which even then, must have been an obscure serial. Smith’s description was based on a fish from Algoa Bay and includes the barely legible fin counts of D, 13/21 and A, 0/14 [dorsal fin with 13 spines, 8 softrays, anal fin with no spinous rays and 14 soft rays]. These fin ray counts do not agree with the dorsal-fin ray count of 12 or 13 spines, plus 15 or 16 rays, and the anal-fin ray count of 3 spines, 7 or 8 rays for A. sebastoides, or the fin counts of any other serranid fish of South Africa. Smith’s description of the colour for his Serranus cuvieri agrees in some respects and disagrees in others with the colour patterns of A. sebastoides. In view of these discrepancies, Serranus cuvierii Smith, 1831, is considered a nomen dubium, as the description does not match any known fish species from South Africa.