Aploactinids are marine, cryptic demersal scorpaeniform fishes found primarily in tropical waters of the western Pacific and Indian Oceans, with a few species represented in temperate waters of Australia.

Southern Velvetfish,  Aploactisoma milesii
A Southern Velvetfish at a depth of 3.5 m, Muttonbird Island, Coffs Harbour, New South Wales, 19 October 2012. Image: Steve Smith
© Steve Smith

Aploactinids are a poorly understood group and many species are known from only a few specimens. This is probably due to their relatively small adult size, very cryptic appearance, and adult habitat among vegetation, or rocky, shelly, coral rubble, or coralline algae substrata. Overall, there are about 40 species in 18 genera (Poss and Eschmeyer, 1978; Poss & Johnson, 1991; Poss, 2000; Johnson, in press), 20 and 18, respectively, of which occur in Australia. Only one of the nine species known to occur in temperate Australian waters is common there (J Johnson, personal communication), but adult distributions are poorly known and larvae may range further south than do adults. Adults are small, cryptic fishes, characterized by a dorsal fin that originates very far forward (normally on the head), large pectoral fins, and a body usually covered with modified prickly scales, that give the skin a velvet-like appearance. The head has numerous bony ridges and blunt spines. Nothing is known of spawning mode. Only a few larvae have been described (Kojima 1988, Leis and Carson-Ewart 2000, Leis et al 2004). Aploactinid larvae are characterized by their huge, early-forming pectoral fins, dorsal fin with some spines on the head, massive, coiled gut, large head with short snout and steep profile, head spination, myomere number, and thick, vesicular skin. Specializations to pelagic life are the extremely large, early forming pectoral fins and the extensive head spination, however, much of the latter is retained by adults.

Meristic characters of aploactinid genera of temperate Australia

Meristic characters of aploactinid genera of temperate Australia
Dorsal Anal Pectoral Pelvic Caudal Vertebrae
Acanthosphex XI-XIII,7-11 I-II,6-8 9-10 I,2 - 24-26
Aploactis XII-XV,11-15 I-III,10-12 11-14 I,2 - 28-30
Aploactisoma XIII-XV,12-16 I,9-12 10-11 I,2 13
Cocotropus XII-XV,7-12 I-II,6-9 11-14 I,3 - 25-28
Erisphex X-XIII,9-16 I-II,9-15 11-15 I,1-2 - 27-31
Kanekonia XI-XIII,7-10 I-II,7-9 13-16 I,1-2 - 25-26
Matsubarichthys II+IV,6 II,4 15 I,1 6+5=11 9+12=21
Neoaploactis VI+VII+I,9-10 I-II,7-9 12 I,3 - 26
Paraploactis XII-XV,8-11 I-II,7-10 13-15 I,3 - 26-28

Main characters of aploactinid larvae

  • Myomeres 21-31
  • Huge, early-forming pectoral fins
  • 3-5 dorsal-fin spines separate and positioned on the head from formation
  • Pelvic-fin count I,1-3
  • Massive, coiled gut
  • Large head with short snout and steep profile
  • Extensive head spination, consisting of blunt spines
  • Thick, vesicular skin that is often inflated in preflexion larvae, and that often obscures myomeres

References to aploactinid larvae

  • Kojima (1988), Leis and Carson-Ewart (2000), Leis et al. (2004)

Families with similar larvae

  • Larvae of the scorpaeniform families Pataecidae and Gnathanacanthidae are unknown, but likely to be similar to aploactinid larvae. Pataecids and gnathanacanthids lack a detatched to semidetatched spiny dorsal fin on the head and have 28-44 vertebrae.
  • Scorpaenidae - Preflexion aploactinids are very similar to morph A scorpaenids of Leis and Rennis (2000), although myomere counts may be useful in distinguishing them. Postflexion individuals are usually identifiable based on the fin-ray counts, particularly the pelvic count of I, 1-3 of aploactinids (I, 4-5 in most scorpaenids): in addition, most of the scorpaenids have better-developed head spination that is pungent and, in many, the dorsal fin does not extend onto the head.
  • Lophiiformes - Early larvae of some lophiiform fishes Ð particularly those with early-forming pectoral fins - might be confused with early Matsubarichthys inusitatus larvae because they share inflated dermis and low number of myomeres, but in the lophiiform larvae, the exhalent opening of the gill is located at the lower edge or below the pectoral-fin base.
  • Grammistinae Serranidae - The grammistin serranids have one or more very elongate, whip-like anterior spines in the dorsal fin, a dorsal fin that does not extend onto the head, and no spination on the infraorbital or parietal.
  • Ophidiidae - The ophidiid, Brotula, has similar body shape to some aploactinids and a large pectoral fin, but has many more myomeres (>50), a dorsal fin without spines, and no head spination.
  • Blenniidae - The blenniids with large, early-forming pectoral fins have more myomeres (usually, >30), often have enlarged, recurved canine teeth, lack head spination other than on the preopercle, and have a much more compact gut.

Note: families in bold text are dealt with in Neira et al., 1998.

Literature cited

  • Johnson, J.W. (2004). Two new species and two new records of aploactinid fishes (Pisces: Scorpaeniformes) from Australia. Records of the Australian Museum 56: 179-188
  • Kojima, J-I. (1988): Scorpaeniformes. In: An Atlas of the early stage fishes in Japan. (Ed: Okiyama, M.) Tokai University Press, Tokyo, 777-887.
  • Leis, J.M. and Carson-Ewart, B.M. (Eds.) (2000): The larvae of Indo-Pacific coastal fishes: a guide to identification (Fauna Malesiana Handbook 2). Brill, Leiden. 850 pages.
  • Leis, J.M., A. C. Hay and A. G. Miskiewicz (2004). Larval development of the rare Australian aploactinid fish Matsubarichthys inusitatus (Pisces: Scorpaeniformes). Zoological Studies
  • Leis, J.M. and Rennis, D.S. (2000): Scorpaenidae (Scorpeonfishes, Stonefishes). In: The larvae of Indo-Pacific coastal fishes: an identification guide to marine fish larvae (Fauna Malesiana Handbook 2). (Eds: Leis,J.M. and Carson-Ewart, B.M.) Brill, Leiden, 226-235.
  • Poss, S.G. (2000): Aploactinidae: Velvetfishes: In: The living marine resources of the western central Pacific, vol 4 (Eds: Carpenter, K.E. and Niem, V.H.) FAO, Rome, 2354-2358.
  • Poss,S.G. and Eschmeyer,W.N. (1978): Two new species of Australian velvetfishes, genus Paraploactis (Scorpaeniformes: Aploactinidae), with a revision of the genus and comments on the genera and species of the Aploactinidae. Proc. Cal. Acad. Sci. 41, 401-426.
  • Poss,S.G. and Johnson,G.D. (1991): Matsubarichthys inusitatus, a new genus and species of velvetfish (Scorpaeniformes: Aploactinidae) from the Great Barrier Reef. Proc. Biol. Soc. Wash. 104, 468-473.