Chilomycterus reticulatus (Linnaeus, 1758)

Leis, Jeffrey M., 2006, Nomenclature and distribution of the species of the porcupinefish family Diodontidae (Pisces, Teleostei), Memoirs of Museum Victoria 63 (1), pp. 77-90 : 80-81

Chilomycterus reticulatus (Linnaeus, 1758)

Diodon reticulatus Linnaeus, 1758: 334 ( India) Diodon echinatus? Linnaeus, 1758: 335 ( India) Diodon tigrinus Cuvier, 1818: 127 , pl. 6 ( Moluccas)* Chilomycterus affinis Günther, 1870: 314 (unknown locality)* Chilomycterus californiensis Eigenmann, 1891: 1133 ( San Pedro,

California)* Euchilomycterus quadradicatus Waite, 1900: 208 (Lord Howe I.) * Chilomycterus lissogenys Günther, 1910: 476 , pl. 179 (Hawaii) Chilomycterus galapagosensis Klausewitz, 1958: 82 , fig. 7

(Galapagos Is.)* *extant type

Based on examination of 55 museum specimens, including extant types, from throughout its range (circumglobal in warm waters), I can find no morphological differences among the different nominal species or among geographic locations. There is variation in colour pattern similar to that found in the circumtropical Diodon holocanthus (see Leis, 1978, ref. 5529) but, like that species, it is not obviously geographically based. Spotting on the body is variable, although usually present to some degree, but smaller spots are present on at least some, and usually all, of the fins. The pelagic juvenile phase has a distinctly different colour phase from the benthic adult. The species remains pelagic to about 200 mm SL, thus providing ample opportunity for dispersal and maintenance of genetic continuity. Therefore, I regard Tylerʼs group of ʻcircumglobal Chilomycterus ʼ to consist of a single species. The rationale for calling this species Chilomycterus reticulatus (Linnaeus) follows.

Diodon atringa Linnaeus (1758, ref. 2787) is frequently regarded as a synonym (often the senior synonym) of this species. This name is often misspelled atinga by authors. This is clearly incorrect: Linnaeus used the spelling atringa in both his tenth and twelfth editions. Nelson et al. (2004, ref. 27807) recently explained why atringa is correct; and Eschmeyer (2005) used atringa . To avoid confusion with D. atinga Bloch (1785, ref. 4866), a synonym of D. hystrix , I herein use the spelling atringa for the Linnaean species, regardless of the spelling used by any subsequent author. Unfortunately, D. atringa Linnaeus is not identifiable. There is no type, and Linnaeusʼ description could apply to any of several species of Chilomycterus or Cyclichthys (including C. reticulatus , C. antennatus or C. spinosus ), and the same is true of Artedi (1738), the only source cited by Linnaeus, and the pre-Linnaean authors cited by Artedi. Artedi, 1738 mentioned that the fins of his “ Ostracion bidens sphaericus…”, upon which Linnaeus based his D. atringa , were spotted, but large individuals of C. antennatus (Cuvier, 1816, ref. 993) also have spotted fins (see below), so this is not diagnostic, as is often assumed. Linnaeus (1766, ref. 2786) cited a plate in Seba (1759, ref. 18716) that represents either C. reticulatus or C. antennatus . Brisout de Barneville (1846, ref. 296) was the first author to express a clear opinion, and considered D. atringa Linnaeus to be synonymous with D. orbe Lacepède (1798, ref. 2708). The latter was based on a specimen from Brazil – no longer extant – that is clearly identifiable as the Atlantic Diodon spinosus Linnaeus (see below). Le Danois (1959, ref. 12003) considered atringa Linnaeus to be approximately equivalent to Tylerʼs “Atlantic Chilomycterus ” group (which includes D. spinosus Linnaeus ) with several subspecies roughly equivalent to Tylerʼs species.

In contrast, D. reticulatus Linnaeus (1758, ref 2787) is readily identifiable. Linnaeus based his description on Artediʼs “ Ostracion subrotudus …”. Atredi (1738) cited a Willughby (1686) plate of “Orbis muricatus and reticulatus” that is clearly identifiable as reticulatus by its colour, general morphology, spine distribution and spine shape. The name reticulatus has been in regular use as a senior synonym (in addition to the nine 1870–1926 references listed by Fowler, 1936, ref. 6546 and the>30 post-1985 references listed by Eschmeyer, [2005]: Lowe, 1844, ref. 2833; Brisout de Barenville, 1846, ref. 296; Günther, 1870, ref. 1995; Poey, 1876, ref. 3510; Goode, 1876, ref. 1832, 1877, ref. 13360; Jordan and Gilbert, 1883, ref.2476; Eigenmann, 1885; Poll, 1959, ref. 12014; Tyler, 1980, ref. 4477; Leis, 1981, 1984; Leis and Bauchot, 1984, ref. 12539). Some authors, apparently following Jordan and Evermann (1898, ref. 2444, have considered reticulatus to be a junior synonym of atringa , but none have attempted to justify this view. It is clear from Jordan and Evermannʼs description and key that they incorporated more than one species in their concept of C. atringa , including at least C. reticulatus and C. antennatus . Jordan and Evermann (1898) described C. atinga as having dark dorsal blotches and a ʻsupraocular cirrusʼ, both features that are lacking in C. reticulatus (Linnaeus) and in Tylerʼs ʻcircumtropical Chilomycterus ʼ, but present in species of the ʻAtlantic Chilomycterus ʼ group.

There is a great deal of confusion in the literature as to just what constitutes C. reticulatus and C. atringa . For much of the 19th century, most authors accepted Blochʼs (1785, ref. 21381) concept of D. atinga (= D. hystrix Linnaeus, 1758 , ref. 2787), and although Brisout de Barneville (1846, ref. 296) pointed out that this was in error, the use of D. atinga sensu Bloch persisted for some years. Séret and Opic (1981) stated without reasons that reticulatus was a synonym of C. atringa (Linnaeus) , but their illustration of C. atringa shows what appears to be C. antennatus (Cuvier) (Séret and Opic kindly provided unpublished dorsal and lateral views of the specimen that strengthen this opinion). Similarly, Tortonese (1973, ref. 7192), without comment, listed reticulatus as a junior synonym of atringa , but, later, Tortonese (in Whitehead et al., 1986, ref. 13677) illustrated as C. atringa a specimen of the eastern Atlantic C. spinosus mauretanicus (Le Danois) , but with spotted fins, a feature I have not observed in the latter species. Smith-Vaniz et al., 1999 (ref. 25013) listed C. atringa (Linnaeus) as occurring in Bermuda, but had seen no specimens, stating that their listing was based on Goodeʼs (1876, ref. 1832; 1877, ref. 13360) and Güntherʼs (1870, ref. 1995) records of C. reticulatus . Unfortunately, this leads to ambiguity because, Smith-Vaniz et al. (1999, ref. 25013) could be interpreted as considering reticulatus a synonym of atinga , or as considering that the other authors misidentified their specimens. Some other workers (e.g., Fowler, 1936, ref. 6546; Lozano Rey, 1952) have included reticulatus of authors in their synonymies of atringa , but not reticulatus Linnaeus (1758, ref 2787), implying that they questioned othersʼ concept of reticulatus rather than that they considered reticulatus Linnaeus to be a junior synonym of atringa .

In more recent years, a view has developed among some American workers that Atlantic individuals of this taxon are C. atringa , whereas the Indo-Pacific individuals are either C. affinis (Robins et al.,1991, ref.14237) or C. reticulatus (Nelson et al., 2004, ref. 27807), but, again, no justification for this or means of distinguishing the two nominal species has ever been presented. Tyler (1980, ref. 4477) tentatively recognized four species in this complex that have, based on his material examined and text, different distributions: C. atringa (western Atlantic); C. reticulatus (eastern Atlantic and Indo-Pacific); C. tigrinus (western Indian Ocean); and C. affinis (Eastern Pacific). However, Tyler (1980, ref. 4477) said that C. tigrinus may be the young of C. reticulatus (I agree). So confusion about the identity and distribution of these species continues.

In summary, D. atringa Linnaeus is unidentifiable, and the post-Linnaean use of the name by various authors has been inconsistent as to what species was being included: at least four species and two multi-species groups have been identified as D. atringa by various authors at various times. In spite of the use of C. atringa (usually spelled atinga ) by several authors, the name should be regarded as a nomen dubium, and not used. Diodon reticulatus Linnaeus is clearly identifiable, and the use of the name has been remarkably consistent: it should be used for this species.

Diodon echinatus Linnaeus (1758, ref 2787) is seemingly equivalent to his Chilomycterus reticulatus (see Leis and Randall, 1982). Linnaeusʼ (1758, ref 2787) description and the Marcgrave plate to which Artedi (1738) referred could apply to any Chilomycterus or Cyclichthys species. Linnaeus (1766, ref. 2786) referred to a Seba (1759, ref. 18716) figure that is clearly Diodon hystrix . Gronow (1854, ref. 6828), in his account of “ Holocanthus echinatus ”, cited a Seba (1759, ref. 18716) figure that is either Chilomycterus reticulatus or C. antennatus , and a Willughby (1686) figure that clearly represents C. reticulatus .

The holotype of Diodon tigrinus Cuvier (1818, ref. 18059) is a specimen in the pelagic colour phase of C. reticulatus . The species was recognized as a synonym of C. reticulatus as long ago as Brisout de Barneville (1846, ref. 296).

Chilomycterus affinis Günther (1870, ref.1995) was based on a specimen of unknown locality that is dried and thickly varnished. The holotype has minimal spotting on the body, and the spines, particularly on the head, are distorted by the taxidermy and insertion of large, blue glass eyes. However, there is nothing outside of the range of C. reticulatus variability in this specimen. In the absence of any locality information, it is unclear why most authors regarded this as a Pacific species.

Chilomycterus californiensis was described by Eigenmann (1891, ref. 18744) on the basis of a specimen that he initially did not obtain from the fisherman who captured it “on account of the unreasonable price asked for it”. However, the fish was subsequently “procured by the National Museum”, and Eigenmann (1892) redescribed and figured it. Therefore, USNM 43860 is in fact the holotype, in spite of Eigenmannʼs statement in the original 1891 description that “I did not obtain it”. The holotype is in the pelagic colour phase of C. reticulatus .

Euchilomycterus quadradicatus Waite (1900, ref. 4558) from Lord Howe I. was based on a dried specimen – apparently a beach wash-up – subsequently preserved in ethanol and in poor condition. Although not figured by Waite, Whitley (1952) illustrated the holotype (with some artistic license) clearly showing the caudal-peduncle spine and four-rooted spines on the head that in combination are diagnostic of Chilomycterus reticulatus .

Chilomycterus lissogenys Günther (1910, ref. 14460) was based on an illustration by Garrett of a Hawaiian fish. Although Garrett omitted some of the spines on the side of the head, he clearly showed the spine on the caudal peduncle that is characteristic of C. reticulatus . The illustration showed relatively few spots on the body, but heavily spotted fins, a condition well within the range of colour variation in this species.

Thedescriptionandphotoof Chilomycterus galapagosensis Klausewitz (1958, ref. 12080) are clearly that of C. reticulatus . The description of the nostrils alone is diagnostic. Klausewitz distinguished his new species from C. atringa , which he described as having a supraorbital cirrus and large dorsal blotches (presumably based on the description of Jordan and Evermann [1898, ref. 2244], which was based on more than one species), by its lack of these two characteristics. He distinguished it from C. californiensis by colour, but the latter is in pelagic-phase colour, whereas C. galapagosensis has typical, spotted demersal colour.

Distribution. Circumglobal in warm temperate to tropical waters:

W Atlantic – 39 oN to 24 oS

E Atlantic – Madeira (and possibly to Portugal) and Cape Blanco to Angola

W Indian Ocean – South Africa to Tanzania and Reunion, Seychelles and Mauritius

E Indian Ocean – Broome, Western Australia to Bali and Timor

W and central Pacific – Japan to Lord Howe I. and northern New Zealand, to Tuamotos to Hawaii (and in the east Pacific barrier)

E Pacific – San Pedro, California to Chile, Galapagos and Revillagigedos

Occurrences of this species are patchy, and many are based on pelagic juveniles: in particular, adults are unknown from broad areas of the Indo-Pacific. Pelagic juveniles are frequently found poleward of the distribution of adults in areas of strong, poleward currents.

If future work indicates that C. reticulatus contains more than one geographically distinct species, several names are available for Indo-Pacific populations, but no name is clearly based on Atlantic material. Most of the extant types are either dried or fixed in alcohol, so it may be possible to obtain genetic data from them that could be helpful. Unfortunately, there are no Linnaean types that might assist in this regard, and Linnaeusʼ usage of ʻhabitat in Indiaʼ cannot be taken at face value in most cases.