Japanese Journal of Ichthyology 魚 類 学 雑 誌 Vol.30,No.21983 30巻2号1983年

A Revision of the Fish from ,with Description of a New Species

Kosaku Yamaoka (Received December 13,1982

Abstract The cichlid fish genus Petrochromis is endemic to Lake Tanganyika.The genus consists

of six species:5 previously known and the present new species,P.macrognathus.This new species is easily distinguished from the other species of Petrochromis by the following characters:more

projecting upper jaw,posterior margins of lips just reaching to vertical from anterior orbital rim, shorter pectoral fins(26.0•`28.2% in standard length(SL)instead of 30.5•`36.0%),strongly pro-

nounced premaxillary ascending process,pronounced concavity of chin region,greater number of vertebrae(33 34 instead of 30•`32),many small scales present on bases of dorsal and anal fins,

and specimens smaller than about 160 mm SL show distinct 11 to 12 vertical stripes(in larger ones those stripes become obscure and the whole body becomes dark-green or dull yellowish-green).

A key is given to the species of Petrochromis.

Fishes of the genus Petrochromis are algal interorbital width of Hubbs and Lagler(1958)is feeders and attain a large size for .They adopted as interorbital width.Distance between inhabit the shallow rocky shore of Lake Tanga- anterior tips of the upper and lower jaws is mea- nyika,and are endemic to the lake. sured from the anteriormost tip of upper jaw to Until recently five species of the genus Petro- the corresponding tip of the lower one with the chromis have been recognized,i.e.,P.polyodon, mouth closed on a projection chart.Propor- P.fasciolatus,P.trewavasae,P.orthognathus and tional measurements of five species excepting P.famula.A key to these species was given by the new one are shown in Table 1.Number of Brichard(1978)on the basis of Poll(1956), vertebrae is counted from radiographs. Matthes(1959)and Matthes and Trewavas(1960). Feeding behavior of the new species was ob- During an ecological survey of the north- served on two individuals of about 160mm in western part of Lake Tanganyika from July standard length(SL)at Luhanga on August 12 through December,1981 I caught some specimens and 13,and September 11,1981.One hundred of an undescribed species belonging to the genus and twenty-two observations were made. Petrochromis from shallow waters along the rocky shore.In addition to the description of the Genus Petrochromis Boulenger,1898 new species,a revised key to Petrochromis is Petrochromis Boulenger,1898:20(type species,Petro- offered,mainly based on external characters, chromis polyodon Boulenger,by monotypy); not on coloration or internal characters. Pellegrin,1904:350;Regan,1920:42;Poll,1946: Standard measurements and counts follow 277;Poll,1956:596;Poll,1957:143;Matthes and Hubbs and Lagler(1958)except for the follow- Trewavas,1960:350;Brichard,1978:334. ing items:length of head(from the tip of the Diagnosis.This genus is distinguished from snout to the posterior bony margin of the gill other cichlids by the following character com- cover),width of snout(the widest part of the bination:1)dental pads with many tricuspid snout not including the labial region),length of teeth with slender shafts,2)gill-rakers on lower lower jaw(from the anterior tip to the posterior limb of first arch 10 13,3)pharyngeal apophy- end of the lower jaw),depth of labial(the deepest sis of Tilapia type and 4)unpaired gonad. part of the upper lip)and width of lower jaw Description.Petrochromis is a genus endemic (the distance between the points on the left and to Lake Tanganyika.D.XVII•`XIX,7•`10; right lower jaws just anterior to the rim marking A.III,6•`8;number of lateral-line scales,32 their articulation with the suspensorium,as 36;vertebrae,30 34;gill-rakers on lower limb defined by Barel et al.(1977)).Least bony of first arch,10 13;branchiostegal rays,5.

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―130― Yamaoka:Revision of Petrochromis

Table 2.Frequency distributions of 5 meristic characters in species of Petrochromis.

A comparison of some diagnostic characters of cally the same(Yamaoka,1982,in prep.;Zihler, the six species of Petrochromis is presented in 1982).Their feeding behavior is also very Table 2. similar(Fryer,1959;Yamaoka,1982,pers.ohs.). Body stocky and compressed.Snout wide. The relationships among Petrochromis,Petro- Mouth large and protrusible.Lips thickened. tilapia and Tilapia(Sarotherodon)must be review- Crowded tricuspid teeth with slender shafts on ed more closely and at present I consider that jaws.Caudal peduncle longer than deep. they were derived from a common ancestor. One nostril on each side. Upper and lower lateral lines on body,both Key to the species of Petrochromis incomplete.Scales slightly ctenoid.Some la.Lower jaw projecting(Fig.2)•c scales on head,tending to be imbedded.Scales cP.fasciolatus present on cheek and opercle. 1b.Jaws equal anteriorly,or upper jaw pro- Dorsal fin continuous.Origin of dorsal jecting•c2 anterior to insertion of pectorals.Pectoral fins 2a.When mouth is closed completely,teeth pointed;fourth ray longest.Pelvic fins pointed; almost invisible from outside•c3 first soft ray longest ;insertion of pelvic behind 2b.When mouth is closed completely,teeth posterior end of pectoral base.Caudal fin visible from outside•c4 emarginate,subtruncate or lunate. 3a.Body not so deep(36.3•`40.7% SL);caudal Only a right gonad present. fin almost non-maculated..P.orthognathus Remarks.Petrochromis of Lake Tanganyika 3b.Body deep(41.5•`42.8% SL);caudal fin is very similar to the genus Petrotilapia of Lake Malawi,but their similarities have been regarded B as a remarkable convergence because these two A genera are different from each other in the struc- ture of the pharyngeal apophysis :the former shows Tilapia type and the latter Haplochromis type(Trewavas,1935;Matthes and Trewavas, 1960;Greenwood,1978).However,on the basis of close reexamination of this feature,Green- wood(1978)rejected the dichotomy of the cichlids into Tilapia and Haplochromis lineages by Regan(1920).Brichard(1978)stated that Petrochromis is very close to Tilapia(Sarother- Fig.1.Lateral view of head.A,P.polyodon, odon).The intestinal coiling pattern,which has FAKU 51093,118.7 mm SL.B,P.macro- been suggested to be a phylogenetically useful gnathus,sp.nov.,paratype,FAKU 50675, feature(Kafuku,1958,1975;Mok,1977;Mok 135.4mm SL.C,convexity of premaxil- and Shen,1982),of these three genera are basi- lary ascending processes.

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Fig.2. Boulenger.Lateral view of a male,100.4mm in SL,FAKU 51118.

notably maculatedP famula brae 31•`32(mainly 31). 4a.Caudal fin lunate;body deep brown to Body not so deep.Snout profile gentle, goldenP trewavasae ascending processes of premaxillae not prominent 4b.Caudal fin emarginate•c5 at all.Lower jaw extending in front of upper 5a.No scales on bases of dorsal and anal fins; jaw(prognathous lower jaw).Posterior margins convexity of premaxillary ascending pro- of lips not reaching to vertical from anterior cesses on snout less pronounced(Fig.1A) orbital rim,but going beyond vertical from nostril. P polyodon Tricuspid teeth on jaws in low density,not show- 5b.Many small scales on bases of dorsal and ing regular series. anal fins;convexity of premaxillary ascend- Cheek with four to five rows of scales.Small ing processes on snout much pronounced scales absent on bases of dorsal and anal fins. Fig.1B)•cP.macrognathus ( sp.nov. Posterior tips of dorsal and anal soft rays not filamentous.Pectoral almost same as head in Petrochromis fasciolatus Boulenger,1914 length.Pelvic fin short,not reaching anal (Fig.2) spine.Caudal fin emarginate. Petrochromis fasciolatus Boulenger,1914:446;Bou- Color in life.In large males,whole body except lenger,1915:273;Poll,1946:277;Poll,1956:105, dorsum and ventral part of head and chest fig.19;Poll,1957:143;Brichard,1978:338. grayish blue.Two gray interorbital stripes on Poll,1946:277. forehead.More than 10 gray vertical stripes on Materials examined.FAKU(Department of dorsum.Eight yellow egg dummies on anal Fisheries,Faculty of Agriculture,Kyoto University) fin.In smaller specimens,probably immature 51115 51117,two males and one female,96.6•` males,and females,ground color of body whitish 111.4mm SL,Luhanga,3•‹31'S,29•‹09'E,2•`6m brown to whitish green with 9 to 10 brownish deep,October 17,1981.FAKU 51118•`51120, vertical stripes on each side.Many small two males and one female,85.4•`100.4 mm SL, Kashombe,3°31'S,29°09'E,1 6 m deep,August 14, orange spots on body and fins.

1981. Color in formalin.In large males,whole body Description.D.XVII•`XVIII,8•`9;A.III, dark chocolate-brown.In smaller specimens, 6•`7:gill-rakers on lower limb of first arch 11•` probably immature males,and females,ground 13;number of lateral-line scales 32 33;verte- color of body brownish with dark brown stripes.

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Fig.3.Petrochromis orthognathus Matthes.Lateral view of a female,105.5 mm in SL,FAKU 51111.

Remarks.Though Boulenger(1914)did not rakers on lower limb of first arch 10•`13;number point it out in the original description of Petro- of lateral-line scales 32;vertebrae 30 31(mainly chromis fasciolatus,the prognathous lower jaw 31). is the most remarkable diagnostic character of Body not so deep.Snout profile of ascending this species. processes of premaxillae not prominent.Upper P.fasciolatus is relatively close to P.ortho- jaw meeting the lower almost evenly in front gnathus in having fewer jaw teeth(Yamaoka, (isognathous)or upper jaw only slightly pro- 1982)and smaller number of vertebrae(31), jecting.Posterior margins of lips not reaching but differs in the following characters:1)lower to vertical from anterior orbital rim.Tricuspid jaw projecting(jaws equal anteriorly in the lat- teeth on jaws in low density,tending to show ter);2)generally 18 dorsal spines(19 spines); regular series. 3)generally 9 vertical stripes on the body(no Cheek with four rows of scales.Only a few vertical stripes). small scales present on bases of dorsal and anal Brichard(1978)stated that all species of fins. Petrochromis are highly solitary and are never Posterior tips of dorsal and anal soft rays not found in schools or even the ephemeral groupings filamentous.Pectoral fin almost same as head of Tropheus.I observed and recorded on 8mm in length.In large male posterior tip of pelvic film,however,a school of many adult individuals fin filamentous,reaching anal spine.Caudal swimming slowly around rocks on sandy bot- fin emarginate. tom at the depth of 4 m at Kashombe. Color in life.Head and dorsum brown.Verti- cal stripes not conspicuous.Two pearl white Petrochromis orthognathus Matthes,1959 interorbital stripes on forehead.One whitish (Fig.3) stripe behind orbit on nape.Seven to eight Petrochromis orthognathus Matthes,1959:335;Bri- yellow egg dummies present on anal fin in larger chard,1978:338. specimens.Flank pearly olive white. Materials examined.FAKU 51110•`51114,2 Color in formalin.Head and dorsum dark males and 3 females,97.1•`136.3 mm SL,Luhanga, brown.Flank whitish brown. 2•`10m deep,from August to October,1981. Remarks.Matthes(1959)stated that Petro- Description.D.XIX,7•`8;A.III,6;gill- chromis orthognathus is closely related to P.

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Fig.4. Matthes et Trewavas.Lateral view of a female,93.3mm in SL,FAKU 51107. famula and pointed out seven characters for dis- Materials examined.FAKU 51104 51109,4 tinguishing the two species.The results of the males and 2 females,84.2— 118.1 mm SL,Luhanga, present study agree with those characters.He 1 6 m deep,from August to December,1981. included the morphology of the lower pharyn- Description.D.XVIII•`XIX,7•`9; III,7;

geal bone,an internal character,as one of the gill-rakers on lower limb of first arch 10 13; distinguishing characters.However,I think number of lateral-line scales 32; vertebrae 30 31

that such internal characters are not always (mainly 31). necessary for distinction.The diagnostic char- Body deep.Snout profile of ascending pro- acter of P.orthognathus is the isognathous jaws. cesses of premaxillae moderately prominent. As shown in Yamaoka (1982),this species seems Upper jaw extending in front of lower jaw slightly. to represent the most primitive form because of Posterior margins of lips not reaching to verti- the primitive arrangement of the jaw dentition. cal from anterior orbital rim.Tricuspid teeth In juveniles,the whole body color in life is on jaws in higher density,not showing regular brownish. series. Though the mean depth of the habitat of P. Cheek with two to three rows of small scales, orthognathus has been reported to be 3m by its inferior half naked.Fewer small scales Matthes(1959),large specimens,probably ma- present on bases of dorsal and anal fins. ture males,mainly inhabit deeper water of 8•` Posterior tips of dorsal and anal soft rays not 10m. filamentous.Pectoral fin almost same as head in length.Pelvic fin in males reaching anal spine, Petrochromis famula Matthes et but not in females.Caudal fin subtruncate. Trewavas,1960 Color in life.Generally almost whole body (Fig.4) deep purple.Occasionally 9 whitish narrow Petrochromis famula Matthes and Trewavas,1960: vertical stripes on each side.Distal tips of two 349,fig.1; Brichard,1978:338. membranes between three anal spines yellowish.

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Fig.5.Petrochromis trewavasae Poll.Lateral view of a male,147.1mm in SL,FAKU 51098.

Caudal fin maculated.Outer ring of eye whitish Petrochromis trewavasae Poll,1948 in underwater. (Fig.5) Color in formalin.Body deep purplish brown. Petrochromis trewavasae Poll,1948:10,fig.5:Poll, Caudal fin maculated. 1956:109;Poll,1957:134,Brichard,1978:338. Remarks.Matthes (1959)and Matthes and Materials examined.FAKU 51098•`51102,2

Trewavas(1960)stated that P.famula is very males and 3 females,121.2•`147.1mm SL,Luhanga, close to P.orthognathus and P.polyodon,respec- 4•`10m deep,from July to October,1981. tively.Matthes and Trewavas(1960)pointed Description.D.XVIII,9;A.III,6•`7;gill- out eight characters distinguishing P.famula from rakers on lower limb of first arch 10•`11;

P.polyodon.My data agree with their state- number of lateral-line scales 33 34;vertebrae ments.The number of the vertebrae is generally 32. 31 in the former and generally 32 in the latter Body deep.Snout profile of ascending process- (Table 2).Thus,on the basis of the number of es of premaxillae moderately prominent.Upper vertebrae P.famula is probably closer to P. jaw extending in front of lower jaw notably. orthognathus than P.polyodon. Posterior margins of lips not reaching to verti- Brichard (1978:257)showed two photographs cal from anterior orbital rim.Tricuspid teeth on of two specimens of Petrochromis.The upper jaws in higher density than in P.fasciolatus and specimen was designated as an unidentified P.orthognathus,and not in regular rows. species and the lower one as P.fasciolatus.I Cheek with five to six rows of scales.Fewer am almost certain that both specimens are P. small scales present on bases of dorsal and anal famula because of their common features of upper fins. and lower jaws and maculated caudal fin.The Posterior tips of dorsal and anal soft rays upper specimen seems to be a younger one.In slightly filamentous.Pectoral fin shorter than juveniles and young,9 whitish delicate vertical head.Pelvic fin long,reaching anal spine. stripes on each body side are conspicuous. Caudal fin lunate.

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Fig.6.Petrochromis polyodon Boulenger,Lateral view of a male,145.8mm in SL,FAKU51094.

Color in life.Whole body except basal part of black and they inhabit crevices among rocks. dorsal fin dark brown.Basal part of dorsal Specimens measuring28mm in standard length fin golden yellow.Occasionally9vertical del were found to be brooded in the oro-pharyngeal icate stripes of witish dots on each flank. cavity of a female. Color in formalin.Upper half of body dark

chocolate brown.Lower half whitish brown. Petrochromis polyodon Boulenger,1898 Remarks.Poll(1948)described this species (Fig.6) on the basis of a single specimen measuring Petrochromis polyodon Boulenger,1898:20,fig.1: 120mm in total length.As this species grows Pellegrin,1904:352;Boulenger,1906:573;Bou to almost 150mm SL the type specimen can be lenger,1915:270;Regan,1920:42;Poll,1946: regarded as a younger one.Description by Poll,1956:101;Poll,1957:143;Brichard,1978: Poll(1948)and a key given by Poll(1956)should 338.

be read with this view.A key given by Brichard Materials examined.FAKU 51093 51097,2 (1978)is only concerned with the coloration and males and3females,118.7•`147.9mmSL,Luhanga, inappropriate for the following reasons: 1•`5m deep,from August to October,1981. vertical stripes on flanks are not always present in Description.D.XVII•`XVIII,8•`9;A.III, specimens even in life.Besides,these stripes 6•`7;gill rakers on lower limb of first arch tend to fade away in formalin.Though the 10•`12;number of lateral-line scales 33•`34; number of dorsal spines was19in the original vertebrae 32. description by Poll(1948),it is commonly18. Body deep.Snout profile of ascending pro He also stated that P.trewavasae is very similar cesses of premaxillae moderately prominent. to P.polyodon.The same number of the verte Upper jaw extending in front of lower jaw brae(Table2)also indicates that these two species notably.Posterior margins of lips not reaching are closely related to each other.The most to vertical from anterior orbital rim.Tricuspid diagnostic character of this species is its lunate teeth on jaws in higher density,not showing caudal fin. regular series. Larger specimens(probably mature males) Cheek with six rows of scales.Small scales mainly inhabit deeper water of8•`12m deep. absent on bases of dorsal and anal fins. Whole body of juveniles and young are coal Posterior tips of dorsal and anal soft rays not

一136一 Yamaoka:Revision of Petrochromis

Fig.7.Holotype of Petrochromismacrognathus sp.nov.,FAKU 50673,161.3mm in SL,collected from Luhanga,northwestern part of Lake Tanganyika.

filamentous.Pectoral shorter than head and Petrochromis can be divided into three groups, almost transparent.In largemales posterior i.e.,those with31-,32-,and33vertebrae.The tip of pelvic filamentous,reaching anal spine. direction of the diversification seems to be from Caudal fin emarginate in large specimens and fewer to greater in number,which agrees with rather truncate in smaller ones. Cichocki's(1976)suggestion that themajor Color in life.In largermaturemales whole trend is toward increased vertebral number body grayish light blue.In smaller specimens, rather than reduced number in cichlids. probably immaturemales,and females,body Brichard(1978:339)shows a photograph of a yellowish green with 9 dark green vertical stripes. specimen identified as Petrochromis fasciolatus. Color in formalin.In largematuremales head I am confident that the specimen is P.polyodon, and dorsum dull chocolatebrown.Flank because of its projecting upper jaw,body form whitish brown.In smaller specimens,body and pattern of stripes on the body side. whitish brown with dull brown vertical stripes. P.polyodon inhabits from the surface(juveniles) Remarks.Excepting the number of dorsal to a depth of about7m on rocky bottoms,and and anal soft rays,and length and depth of caudal shallow water is itsmain habitat. peduncle,the external characters obtained from the present study agree with those of the original Petrochro mismacrognathus sp.nov. description by Boulenger(1898).The discrep (Fig.7) ancymay be due to differences inmethods of Holotype.FAKU(Department of Fisheries, counting andmeasuring.The number of the Faculty of Agriculture,Kyoto University)50673, vertebrae in the descriptions of the genus amale,161.3mm SL,Luhanga,3•‹31'S,29•‹09'E,rocky Petrochromis by Boulenger(1898)and Regan bottom at a depth of 0.5m,hand net,July 27,1981, caught by Ngera Ngera Lombola. (1920)agrees with the present study.P.polyo Paratypes.FAKU 50674,a female,130.3mm SL, don seems to be situatedmorphologically between Luhanga,at a depth of 0.5m,hand net,July 30, P.trewavasae and P.macrognathus.On the 1981.FAKU50675,a female,135.4mm SL, basis of the number of vertebrae,six species of Luhanga,at a depth of 0.5m,hand net,July 30,1981.

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FAKU 51090,a female,114.3mm SL,Luhanga,at a lowish-green.

depth of 0.5m,hand net,August13,1981.NSMT Description.Counts and proportionalmea P(Department of Zoology,National Science surements are shown in Table3. Museum,Tokyo)21791,a female,120.2mm SL, Body stocky and compressed.Head stout and Luhanga,at a depth of 0.5m,hand net,August 10, long.Skin of body thick.Snout very broad, 1981.NSMT-P21792,amale,164.1mm SL, width broader than length.Snout profiles Pemba,3•‹40'S,29•‹09'E,at a depth of1.0m,spear, strongly humped by ascending processes of pre October 17,1981. maxillae.Eye diameter short.Interorbital

Diagnosis.This species is easily distinguished space narrower.Mouth very large.Upper from other species of Petrochromis by the fol jaw extendingmuch in advance of lower jaw lowing characters:1)more projecting upper (retrognathous).Posteriormargins of lips just jaw,2)posteriormargins of lips just reaching to reaching to vertical from anterior orbital rim. vertical from anterior orbital rim,3)shorter Upper lipmuch thickened.Tricuspid teeth on

pectoral fins(26.0•`28.2%of SL instead of jaws in higher density,not in regular rows. 30.5•`36.0%),4)strongly pronounced premaxil Posterior teeth small.Scales slightly ctenoid.

lary ascending processes,5)pronounced con Scales of nape and thorax small.Cheek with

cavity of chin region,6)greater number of verte five to six rows of scales.Scales present on the

brae(33•`34 instead of30•`32),7)presence of opercle.Caudal fin lobes scaled except for many small scales on bases of dorsal and anal posterior region.Many small scales present on

fins,and8)specimens smaller than about 160mm bases of dorsal and anal fins.

SL show distinct11to12vertical stripes,but in Last dorsal spine longest:5th soft ray longest,

larger ones these stripes become obscure and when depressed extending to the posterior tip of

whole body becomes dark-green or dull yel anal soft ray:not so filamentous.Anal origin

Table3.Proportional measurements and counts of Petrochromis macrognathus sp.nov.Data show ranges;themeans and sample sizes in parentheses.

―138― Yamaoka:Revision of Petrochromis below 17th dorsal spine.Third anal spine polyodon also occur.Since its mode of life is longest:3rd soft ray longest,posterior tip not so somewhat cryptic between rocks near shore,it is filamentous.Anal fin with base ending a little apt to be out of sight.They are found in depths anterior to end of dorsal fin base.Pelvic fin ranging from the water surface to2 m,and hover long,reaching beyond the posterior tip of2nd in waves to feed on algae usually attached on a anal spine in larger specimens(male).Caudal fin nearly vertical plane of rocks between the water emarginate with slightly pointed corner(males) surface and a depth of0.5m.Whereas P. or with round corner(young and females). polyodon is found at depths ranging from the Color in life.In specimens larger than160mm surface to7m. SL(males),whole body dark-green or dull yel Feeding behavior of this species is somewhat lowishgreen.In smaller specimens(young and different from that of P.polyodon.Speed of females),head darkgreen,body dull yellowish grazing(frequency of mouthopening and mouth green,with distinct11to12dark-green vertical closing cycles per second)is faster.Because of stripes;the first stripe beginning dorsally at the its speed,brief duration and indistinctness origin of dorsal fin,passing semiobliquely just caused by foam from the waves,it was impos posterior to pectoral base;second,beginning at sible to measure.The mean and the standard fourth through fifth dorsal spines;tenth lying deviation of the figure of SRT(successional re between posterior dorsal and anal fins;eleventh peated times:frequency of mouthopening and and twelfth stripes on caudal peduncle;dorsal, mouthclosing cycles per each pressing of the anal,caudal and pelvic fins darkgreen,pectoral mouth against rock surface)is1.56•}0.61. fin not so dark. According to Yamaoka(1982),the mean of Color in formalin.Whole body dark choco SRT of P.polyodon,P.trewavasae,P.famula,P. late-brown in larger males.In young and females, orthognathus and P.fasciolatus were4.63,3.61, dark-green area in life becomes dark chocolate 1.66,2.74 and 6.29,respectively. brown,and dull yellowish-green becomes grayish Yamaoka(1982)stated that species possess brown. ing a more projecting upper jaw grazes slowly Remarks.Petrochromis macrognathus is and is regarded to be more specialized for comb closely related to P.polyodon in having a pro ing off algae from the rock surface.The pro jecting upper jaw and emarginate caudal fin,but jecting upper jaw and faster speed of grazing in differs from it in the following characters:1) P.macrognathus contradict the abovementioned shallower depth of body;2)posterior margins of suggestion.Since P.macrognathus feeds in the lips just reaching to vertical from anterior orbital surface zone,if speed of grazing is slower or the rim;3)more projecting upper jaw;4)thicker lip figure of SRT is higher,it may become stranded of upper jaw;5)much pronounced convexity of out of water. premaxillary ascending processes;6)pronounced concavity of chin region;7)shorter pectoral fins; Acknowledgments 8)narrower interorbital width;9)greater number I would like to express my sincere thanks to of vertebrae;10)greater number of dorsal soft Professor Tamotsu Iwai,Kyoto University for rays;11)small scales present on bases of dorsal his helpful advice and critical reading of the and anal fins;12)11to12 dark-green vertical manuscript.Delegue General and other mem stripes on the body.Poll(1956)described the bers of the I.R.S.(Institut de Recherche modal fin formula of dorsal for P.polyodon as Scientifique)of Zaire,especially Director Menga follows;D.XVIII,10,though modal counts of K.Kwetuenda and all other staff of the I.R.S./ dorsal soft rays in my material were eight.This Uvira Station,are greatly acknowledged for their discrepancy may be due to difference of counting courtesy and supports.I am also grateful to method.He probably counted the posterior Mr.Ngera Ngera Lombola in Luhanga for most two rays as two. collecting some specimens and to the members The largest specimen collected measures of our survey team;Drs.Hiroya Kawanabe, 172.2mm SL. Makoto Nagoshi,Yasunobu Yanagisawa and Habitat and feeding behavior.This species is Mr.Nseu-B.Mbomba,for advice and help not so rare along rocky shores where many P. during my stay in Uvira.My thanks go to Dr.

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Tetsuji Nakabo for critical comments on the testinal coiling pattern of Indian major carps. Bull. manuscript. Freshwater Fish. Res. Lab., 27 (1): 1•`19. The study was partly supported by a Grant-in Matthes, H. 1959. Un Cichlidae nouveau du lac Aid for Overseas Scientific Survey(Nos.404130,- Tanganika: Petrochromis orthognathus n. sp. Rev. 504328,56041032and57043028)from the Mini Zool. Bot. Afr., 60 (3/4). 335•`341. Matthes, H. and E. Trewavas. 1960. Petrochromis stry of Education,Science and Culture,Japan, and by grants from the Ito Foundation for the famula n. sp., a cichlid fish of Lake Tanganyika. Rev. Zool. Bot. Afr., 61 (3/4): 349•`357. Advancement of Ichthyology. Mok, H. K. 1977. Gut patterns of the Acanthur idae and Zanclidae. Japan. J. Ichthyol., 23 (4): Literature cited 215•`219. Barel, C. D. N., M. J. P. van Oijen, F. Witte and Mok, H. K. and S. C. Shen. 1982. Phylogeny of

Els L. M. Witte-Maas. 1977. An introduction to the chaetodontids on the basis of kidney and

the and morphology of the haplochro intestinal differentiations. Japan. J. Ichthyol., mine Cichlidae from Lake Victoria. Neth. J. 29 (1): 43•`61. Zool., 27 (4): 333•`389. Pellegrin, J. 1904. Contribution a l'etude anatomi Boulenger, G. A. 1898. Report on the collection que, biologique et taxinomique des poissons de la of fishes made by Mr. J. E. S. Moore in Lake famille des cchlides. Mem. Soc. Zool. France, Tanganyika during his expedition, 1895, 1896. 16: 41•`402, pls. 1•`7. Trans. Zool. Soc. London, 15 (1): 1•`30, pls. 1•`8. Poll, M. 1946. Revision de la faune ichthyologi Boulenger, G. A. 1906. Fourth contribution to the que du lac Tanganika. Ann. Mus. Congo Beige, ichthyology of Lake Tanganyika. Report on the Zool., ser. 1, 4 (3): 141•`364, pls. 1•`3. collection of fishes made by Dr. W. A. Cunnington Poll, M. 1948. Descriptions de Cichlidae nouveaux during the third Tanganyika Expedition, 1904 recueillis par la Mission Hydrobiologique Belge 1905. Trans. Zool. Soc. London, 17 (4): 537•`598, au lac Tanganika (1946•`1947). Bull. Mus. Roy. pls. 30•`41. Hist. Nat. Belg., 24 (26): 1•`31. Boulenger, G. A. 1914. Diagnoses de poissons nou Poll, M. 1956. Poisson Cichlidae, resultats scienti veaux. Rev. Zool. Afr., 3: 442•`447. fiques exploration hydrobiologique du Lac Tanga

Boulenger, G. A. 1915. Catalogue of the fresh nika (1946•`1947). 3 (5b): 1•`619. water fishes of Africa in the British Museum (Nat. Poll, M. 1957. Les genres des poissons d'eau douce

Hist.), London, 3: xii+526 pp. de l'Afrique. Ann. Mus. Roy. Congo Belge, Zool., Brichard, P. 1978. Fishes of Lake Tanganyika. 54: 1•`191. T. F. H. Publication, Neptune City, 448pp. Regan, C. T. 1920. The classification of the fishes Cichocki, F. P. 1976. Cladistic history of cichlid of the family Cichlidae. I. The Tanganyikan fishes and reproductive strategies of the American genera. Ann. Mag. Nat. Hist. , (9) 5: 33•`53. genera Acarichthys, Biotodoma and Geophagus. Trewavas, E. 1935. A synopsis of the cichlid fishes Ph. D. Dissertation, the University of Michigan, of Lake Nyasa. Ann. Mag. Nat. Hist., (10) 15: 710 pp. 65•`118. Fryer, G. 1959. The trophic interrelationships and Yamaoka, K. 1982. Morphology and feeding be ecology of some littoral communities of Lake haviour of five species of genus Petrochromis Nyasa with special reference to the fish, and a (Teleostei, Cichlidae). Physiol. Ecol. Japan, discussion of the evolution of a group of rock 19 (1): 57•`75. frequenting Cichlidae. Proc. Zool. Soc. Lond., Zihler, F. 1982. Gross morphology and configura 132: 153•`281. tion of digestive tracts of Cichlidae (Teleostei,

Greenwood, P. H. 1978. A review of the pharyngeal Perciformes): phylogenetic and functional signi apophysis and its significance in the classification ficance. Neth. J. Zool., 32 (4): 544•`571. of African cichlid fishes. Bull. Br. Mus. Nat. Hist.(Zool), 33 (5): 297•`323. (Department of Fisheries,Faculty of Agriculture, Hubbs, C. L. and K. F. Lagler. 1958. Fishes of the Kyoto University,Sakyo-ku,Kyoto606,Japan) Great Lakes region. Bull. Cranbrook Inst. Sci., 26: 1•`213. タ ン ガ ニ ー 力湖 産 力 ワ ス ズ メ科Petrochromis属 魚 類 Kafuku, T. 1958. Speciation in cyprinid fishes on the の 分類 お よ び1新 種 の 記 載 basis of intestinal differentiation, with some re 山岡耕作 ference to that among catostomids. Bull. Fresh water Fish. Res. Lab., 8 (1): 45•`78, pls. 1•`8. タ ン ガ ニ ー カ 湖 に 固 有 なPetrochromis属 魚 類 の1 Kafuku, T. 1975. An ontogenetical study of in 新 種P.macrognathusを 記 載 し た.同 属 の 他 の5種 に

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つ い て も,比 較 の た め に 主 要 な 形 質 の 記 載 を 行 な っ 部 に 多 数 の 小 鱗 の 存 在 す る こ と;全 身 濃 緑 色 の 成 熟 雄 た.本 種 は 同 所 的 に 生 息 し形 態 的 に 最 も 近 縁 だ と思 わ を 除 く と,体 側 に11～12本 の 暗 緑 色 横 帯 の 存 在 す る れ るP.polyodonと 次 の 点 で 容 易 に 区 別 で き る:体 高 こ と.生 態 的 に も 両 種 間 に は,摂 食 行 動,微 生 息 場 所 が 低 い こ と;口 唇 後 縁 が 眼 の 前 端 部 か ら体 軸 に お ろ し に 差 が み ら れ る.外 部 形 態 に も と づ き,、Petrochromis た 垂 線 に ほ ぼ 達 す る こ と;突 出 し た 上 顎;厚 い 上 顎 唇; 属6種 の 検 索 表 を 作 製 し た. 前 上 顎 骨 上 方 突 起 が 吻 部 へ 顕 著 に 突 出 す る こ と;下 顎 の 順 部 に くぼ み が み られ る こ と;短 い 胸 鰭;脊 椎 骨 が (606京 都市左京区北白川追分町 京都大学農学部水 多 い こ と;背 鰭 軟 条 が 多 い こ と;背 鰭 お よ び 臀 鰭 基 底 産学教室)

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