AMERICAN MUSEUM Novitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2727, pp. 1-14, figs. 1-10, tables 1, 2 May 12, 1982 Redescription of the Indo-Australian Filefish Acreichthys radiatus (Popta) (Monacanthidae, Tetraodontiformes) JAMES C. TYLER1 AND MARK D. LANGE2 ABSTRACT Acreichthys radiatus (Popta, 1900) is rede- the smaller size at sexual maturity in radiatus, in scribed in comparison to A. tomentosus, indicat- radiatus usually having one less anal fin ray, and ing that these two Indo-Australian species differ in several proportional measurements. They also most obviously to the naked eye in color pattern, differ in that the smaller species, radiatus, is whereas microscopic examination shows that found around coral reefs, whereas the habitat of they also can be distinguished by the greater de- tomentosus is inshore on sand and grass beds. gree of scale spinule branching in tomentosus, in INTRODUCTION A small reef-dwelling species of Indo-Aus- tor G. Springer in the Philippines in 1978 and tralian monacanthid has been difficult to by the listing in Hutchins (1977) of a species identify, even though at younger stages it has under the almost forgotten name of radiatus a distinctive color pattern with prominent Popta as a new record for Australia. By ap- pale or chalky white vertical bars on the pellation alone, Monacanthus radiatus Pop- darker body and radiating pale lines centered ta (1900) seemed a candidate for the solution on the eye. to the problem. Moreover, Hutchins (1977) Interest in the identity of this species that placed radiatus in Acreichthys Fraser-Brun- has long perplexed us was renewed recently ner (1941) whose few given diagnostic fea- by finding it among collections made by Vic- tures applied to the unidentified specimens. 1 Research Associate, Department of Ichthyology, American Museum of Natural History; Department of Verte- brate Zoology, Smithsonian Institution; National Science Foundation, Division of Environmental Biology. 2 National Marine Fisheries Service, Southeast Fisheries Center, Miami Laboratory (present address: Rosenstiel School of Marine and Atmospheric Science, University of Miami). Copyright (©) American Museum of Natural History 1982 ISSN 0003-0082 / Price $1.40 2 AMERICAN MUSEUM NOVITATES NO. 2727 Correspondence with J. Barry Hutchins sus anal behind soft dorsal), lateral line "ob- indicated the likelihood of the Philippine solete" (versus discernible), scales broad specimens and of others previously exam- (versus narrow) and dermal filaments devel- ined by us that had been collected in Borneo oped (versus absent). by Daniel M. Cohen in 1965 and in the Mo- While all these characters at least tend to luccas by V. Springer in 1973 (all of the pre- distinguish the two groups, they have usually ceding specimens at the U.S. National Mu- been considered relatively trivial. Thus, seum or the Academy of Natural Sciences of Acreichthys has rarely if ever been recog- Philadelphia) being conspecific with the Aus- nized by subsequent workers as valid at any tralian specimens (at the Australian Mu- taxonomic level except in listings and not at seum) listed by Hutchins (1977). It also all by those conversant with monacanthids. seemed probable that they were conspecific However, Hutchins (1977, pp. 12-13) re- with the holotype and only previously known cently redefined it in a key to the genera of specimen of radiatus Popta (at the Rijks- filefishes from Australia (including nearly all museum van Natuurlijke Historie). the Indo-Australian genera, and several new Through the courtesy of M. Boeseman, genera and species). Hutchins recognized the type specimen of radiatus has been re- Acreichthys as a valid genus, distinguishing ceived on loan and J. B. Hutchins has gen- it more fully from Pervagor in having "all 4 erously sent the five Queensland specimens internal teeth in upper jaw with anterior ex- he had on loan from the Australian Museum tremities notched; bristles on caudal pedun- for comparison with the Philippine and Bor- cle of adult male usually in a well defined neo materials. Upon hearing of this activity, patch; 20 vertebrae" (versus in Pervagor Marie-Louise Bauchot (at the Museum Na- "upper 2 internal teeth with anterior extrem- tional d'Histoire Naturelle) volunteered to ities pointed; adult male generally with all send a specimen of apparently the same scales on side of caudal peduncle developing species that she had collected at New Cale- short bristles, decreasing in size anteriorly; donia in 1978. A search of the collections at 19 vertebrae"). the U.S. National Museum turned up three Hutchins (1977) listed two species in additional specimens of radiatus from the Acreichthys (tomentosus and radiatus), the Philippines and Indonesia, which had been latter being a new record for Australia, but obtained in 1908 and 1909 by the exploratory he did not describe or distinguish them. It is research vessel Albatross, and had been mis- his plan (personal commun.) to do so later in identified as Pervagor tomentosus among a a comprehensive general treatment of all the large series of tomentosus from various lo- Indo-Pacific monacanthids, but in the interim calities. he has generously offered to let us redescribe and diagnose the species radiatus in which GENERIC STATUS OF we have had such long-term interest. ACREICHTHYS Most recently Matsuura (1979) has listed Acreichthys originally was described as a the species hajam Bleeker, often considered subgenus of Pervagor by Fraser-Brunner a synonym of tomentosus Bleeker, in the (1941, pp. 183) with its type and only species genus Acreichthys. Matsuura (personal com- being tomentosus Linnaeus. The subgenus mun.) tells us that hajam has the character- Pervagor remained to contain all the other istics of Acreichthys as defined by Hutchins then recognizable species: janthinosoma (1977) and that it is closely related to but Bleeker, melanocephalus Bleeker, nigrolin- distinct from tomentosus. He also tells us eatus Herre, nitens Hollard, and spilosoma that it has branched spinules on the scales Lay and Bennett. Acreichthys was said to like tomentosus (in contradistinction to ra- differ from Pervagor by having no groove to diatus). Since hajam has a rather drab color receive the dorsal spine when unerected pattern unlike either radiatus or tomento- (versus in Pervagor with a groove present), sus, it obviously is not as closely related to soft dorsal and anal fin origins opposite (ver- radiatus as to tomentosus. Because Mat- 1982 TYLER AND LANGE: ACREICHTHYS RADIATUS 3 V r.-+ z '..11 14-1-.','.. ";k le. FIG. 1. Acreichthys radiatus, USNM 226709, 15.1 mm. s.l., Philippines (smallest specimen available, sex indeterminate). suura is preparing a paper on the distribution lines or other markings, radiatus may be and characteristics of hajam, we do not dis- unique in the family, and clearly differs from cuss it further here. tomentosus, in having about four or more pale to chalky white vertical bars on the up- per half of the middle of the body, another REDESCRIPTION OF ACREICHTHYS more anterior pale bar at the front of the soft RADIATUS AND COMPARISONS dorsal fin base which curves anteriorly to the WITH ACREICHTHYS TOMENTOSUS rear of the top of the eye, and several other Comparison of the 21 specimens of radia- pale lines or bars radiating out from around tus studied with large series of tomentosus the rest of the eye. The pale bands are far (of which counts or measurements were tak- wider and more prominent in younger spec- en on 36 specimens, with measurements con- imens than in older adults, but in the largest centrated on those in the ca. 15 to 50 mm. adults narrower versions of the main pale S.L. size range comparable to the specimens bands, including the four or more on the up- of radiatus) in the collections of the U.S. per half of the body, are evident even in long- National Museum (nearly all from the Phil- preserved specimens (see figs. 1-4). ippines but some also from Indonesia) shows By contrast, in tomentosus the most radiatus to be most easily distinguished from prominent color marking on the body is a tomentosus as follows: pale or chalky white band from just behind (1) COLOR PATTERN: While a number of the top of the pectoral fin base, with a ven- species of monacanthids have a color pattern trally curved middle region coursing poste- of straight to wavy or irregular horizontal riorly to about one-third the way back of the 4 AMERICAN MUSEUM NOVITATES NO. 2727 FIG. 2. Acreichthys radiatus, USNM 226709, 35.1 mm. s.l., Philippines (moderate size male). level of the origin of the soft dorsal and anal dark streak. In some specimens of tomen- fin bases, and sometimes with a much nar- tosus narrow pale lines radiate out from the rower pale line extending from the end of the rest of the eye, but not as prominently as in main pale band to about one-third back along radiatus. There are often irregular pale spots the base of the soft dorsal fin (see fig. 5). The or lines on the lower third of the body and main pale ventrally curved band, more or head of tomentosus, more so than in radia- less horizontal on the body, is bordered both tus, and it is possible that the dermal fila- above and below by a narrower dark streak, ments characteristic of Acreichthys are paler much darker than the generally brownish (in in tomentosus than in radiatus. The color preservative) ground color, with the upper pattern and its changes with increasing spec- dark bordering line tending to be slightly imen size in radiatus (figs. 1-4) stand in con- more complete and regular than the ventral trast to the typical color pattern of tomen- bordering line.