First Record of the Polka dot Triggerfish Canthidermis Rotundatus (Proce) (= Canthidermis Maculatus) (Family Balistidae) from Mumbai

2004·1.3 MB·

by  B F Chhapgar

MISCELLANEOUS NOTES
Hora, S.L. (1921): Fish and fisheries of Manipur with some Menon, A.G.K (1954): Further observations on the fish-fauna of the
observations on those ofthe NagaHills. Rec. Indian Mus. 22: Manipur state. Rec. Indian Mus. 52(1): 21-26.
165-214. Menon, M.A.S. (1952): On a small collection of fish from Manipur.
Hora, S.L. (1936): On a further collection of fish from Naga Hills. Rec. Indian Mus. 50: 265-270.
Rec. Indian Mus. 28: 317-331. Talwar,P.K.& A.Jhingran(1991): InlandfishesofIndiaandadjacent
Hora,S.L. &D.D. Mukerji(1935):FishoftheNagahills,Assam.Rec. countries.OxfordandIBHPublishingCo. Pvt.Ltd.,New-Delhi,
Indian Mus. 37: 381-404. 2 vol: xix + 1158.
Jayaram K.C. (1999): The Fresh water Fishes of the Indian region. Weber, M. & L.F. de Beaufort (1922): The fishes of the Indo-
NarendraPubl. House, New Delhi. 551 pp. AustralianArchipelago. E.J. Brill Ltd. Leiden, 4: xii +40.
27. FIRST RECORD OF THE POLKA-DOT TRIGGERFISH
CANTHIDERMIS ROTUNDATUS (PROCE) (= CANTHIDERMIS MACUEATUS)
(FAMILY BALISTIDAE) FROM MUMBAI
The monsoon season is a harbinger ofunusual fishes,
normally associated with coral reefs, to Mumbai. So far, the
following have been recorded from Mumbai in this season:
MoorishIdolZancluscomutusandSquirrelFishHolocentrus
rubrum (Chhapgar and Deshmukh 1964), Filamented
Butterflyfish Anisochaetodon Linophora auriga Lined
( ) ,
Butterflyfish Anisochaetodon Oxychaetodon lineolatus
( ) ,
Racoon Butterflyfish Chaetodon (Chaetodontops) lunula
,
Yellow-headed Butterflyfish Chaetodon Rhabdophorus
( )
xanthocephalus (Chhapgar and Jatar 1968); Scribbled
LeatherjacketAluterascriptaandyellow-finnedleatherjacket
Monacanthus monoceros (Chhapgar 1978), Red-toothed
Fig. 1: Polka-dotTriggerfish, Batistesmaculatus
Trtggerfish Odonus niger? (Chhapgar and Ringangaonkar
1990) and pig-faced filefish Paramonacanthus dissolving into spots at bases of second dorsal, anal and
choirocephalus (Chhapgar and Muley 1997). caudal. Some parallel oblique stripes on cheeks.” Munro
InJuly 2002, twospecimensofafishwerecollectedat (1955) also observed “undulating brown lines and fine blue
Girgaum Chowpatty (south Mumbai) and brought alive to spots on sides. Fins brownish. Soft dorsal with obscure
the Taraporevala Aquarium. One died within afew days, but blotches on middle ofhighest rays. Caudal dark brown” (in
thelargeroneisstill survivingatthetimeofwritingthisnote. an 1 1 cmfish). Day(1878-88)givesthebodycolourasbluish-
It was about 10cmwhen captured, but is growing fast. It has black. We have not observed any stripes on the live fish. It is
been identified as the Polka-dot (also known as round or said to grow to 55 cm. Colour illustrations of the fish have
rough) Triggerfish Canthidermis rotundatus (Proce). been given by Halstead (1967) in addition to the various
The body of this fish (at least at this size) does not authors mentioned in the references.
have the typical shape ofatriggerfish with ahuge triangular As it is not possible to make scale or fin-ray counts in
head almost one-third the length ofthe body. It is more akin the live specimen, these counts by various authors are given
toCardinalFish(.Apogonspp.).Butithasthetypical“locking- below.
trigger”ofthefirst(spinous)dorsalfin,andthehigh,triangular Day: D.m/26-27,P. 15,A.24-25,C. 12,L.1.40-55,L.tr.
softdorsalandanalfinsbendingtogetherinthesamedirection 28.
—
whileswimming amovementtypical oftriggerfishes. Munro:D.EI/25-26,A.23-24,L.1.42-57,L.tr.30-54.
Colouration: The body iscoal-blackwith ivory-white Barnard:D.HI+24-26,A.24-25,L.tr.28-30.
roundedspotsscatteredalloverit.Withinamonthofcapture, Smith:D.ffl/24-27,A.24-26,L.tr.30.
thenumberandsizeofthesespotshaveperceptiblyincreased. Beaufort&Briggs: D.III/2.23-24,A.1-2.21,P. I 14,L.1.
The black body colouration during the day fades to a very 42-43,L.tr.29-34.
light brown at dusk and remains so at night, darkening again Jones&Kumaran:D,III,D,ii,23-24,A.i,21-22,P.i, 13-
in the morning. The dorsal spine is black and held erect. 14,L. 1.42-44+6-7,L.tr.29-32.
The colour after preservation has been described by It is likely that the depth of the body increases as the
deBeaufortandBriggs(1962)as“lightbrownwithdarkbrown fishgrows, asseenfromtheillustrationsgivenbythevarious
interrupted longitudinal stripes on head, body and tail. authors. The depth is contained 2Vi to 3 times in the total
1 Bombay Nat. Hist. Soc., 101 (3), Sep-Dec 2004 469
MISCELLANEOUS NOTES
length (Day, pp. 687, 688, pi. clxxv), VA times in standard subsequentauthors, rightdown to Day(1878-88), continued
length(Munro,p.271,pi.53),2V3times(Smith,p.409,pis.91, to use Balistes, a genus created by Linnaeus in 1758. It was
104); insmallspecimens, 1.7-1.9,2-2.3 in lengthwith caudal Bleeker (Atlas Ichth.des Indes Orientales Neerlandaises V,
(de Beaufortand Briggs, pp. 309-312), 2.1 to2.6 instandard 1865)who,thoughcontinuingtouse Balistesasgenus, added
length,2.5to3.1 intotal length(JonesandKumaran 1980,pp. Canthidermis as a subgenus, describing the species as
&
665, 666,fig. 566). Inourspecimen it is2.1 times instandard Balistes (Canthidermis) maculatus. Jordan Fowler (Proc.
length2.5times intotal length(132mm). U.S.Nat. Mus.xxv, 1902)raisedittoCanthidermisrotundatus.
Diagnostic features: Agroove in front ofeye. Scales de Beaufort and Briggs, as late as 1962, have usedthe genus
rough, granular, without spines. The cheeks are entirely Balistes without the subgenus Canthidermis.
scaled, but there are no osseous scutes behind the gill- There is alsodifference ofopinionwhetherrotundatus
opening. Second dorsal and anal high anteriorly. Ventral is thejuvenile ofmaculatus orwhetherthe two are separate
,
spineshort,coveredwith spinules, immovable(accordingto species. Mostdescriptions ofrotundatus (with its synonyms
de Beaufort and Briggs as well as Jones and Kumaran), oculatusofGray 1832, Bleeker 865,Gunther 1910, Duncker
I
usuallymovable(accordingto Day). Hindedgeofcaudal fin and Mohr 1929 and senticosus ofRichardson 1848, Bleeker
convex. 1853 and Gunther 1910) are based on small specimens,
The genus Canthidermis can be distinguished from whereas most accounts of maculatus (with its synonym
XanthichthysandPseudobalistes bythe nature ofitscheeks, azureus Lesson 1830)areoflargespecimens.There isfurther
which are normally scaled and without naked grooves confusionasBloch’s(1786)maculatusisfromtheWestIndies
(.Xanthichthys has longitudinal naked grooves, while in (AtlanticOcean),while Bleeker’s(1865)maculatusarefrom
Pseudobalistes the cheeks are naked anteriorly). It differs the Indo-Pacificarea.
from Odonus in not having red teeth. It differs from As the present specimen is of a small size, we have
Rhinecanthus and Balistapus in having a groove before the preferred to call it Canthidermisrotundatus.
eye. It can be distinguished from Abalistes in not having a
depressedcaudalpeduncle,andfromMelichthys Balistoides November2 2002 B.F. CHHAPGAR
, , 1,
Sufflamen and Hemibalistes in not having spines on the BombayNaturalHistorySociety,
caudalpeduncle. Finally, itdiffersfromBalistesinnothaving HornbillHouse,S.B. SinghRoad,
enlarged plates behind the gill-opening. Mumbai400023, Maharashtra, India.
Systeniatics: There is a great deal ofconfusion in the Email; [email protected]
nomenclature ofthis species. Itwas first described by Proce
(Bull. Soc.Philom. Paris,p. 30)asBalistesrotundatusin 1822. K.L. VAIDYA
The genotype is based on Balistes angulosus ofQuoy and TaraporevalaAquarium,
Gaimard 1824.(Fraser-Brunner 1935,pp.658-663).Thegenus Netaji Subhash Road,
Canthidermis was created by Swainson in 1839, but Mumbai400002, Maharashtra, India.
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