Proc, Indian Acad. SCi. (Anim. Sci.), Vol. 91, Number l, January 1982, pp. 79-98. ~ Printed in India.
Some biometric studies of certain closely related species of the genus Arius (Pisces : Siluriformes : Arfidae)
J R DHANZE and K C JAYARAM Zoological Survey of India, 27 J L Nehru Road, Calcutta 700 016, India
MS received 6 March 1981 ; revised 17 August 1981
Abstract. The marine catfish genus Arius of the family Ariidae comprisrng 21 species have been divided into six complexes and three groups based on interspecific relationships and morphometric affinities. In this paper the maculatus complex of four species, viz., Arius maculatus, Arius arius, Arius gagora and Arius jella has been critically examined in respect of a selected list of 20 morphological characters based on examination of a large series of examples collected first hand bY the authors. The samples have been statistically analysed, and the range of variation in respect of each character as exhibited by each species has been delineated. The probability significance test has been made to establish the interspecific relationship.
Keywords. Biometric study; Arius species; Ariidae,
1. Introd1lCtioQ The genus Arius Valenciennes, 1840 forms a commercially important group of marine catfishes comprising 21 species from India, Pakistan, Bangladesh, Burma and Sri Lanka. Most of the species are marine often entering estuarine waters and occasionally even in freshwaters such as A. acutirostris, A. burmanicus and A. gagora etc. About 80% of the total catfish landing in our country is of Arius species. Despite the economic value of these fishes, the taxonomic identity of most of the species is in a state of confusion. The main reason for such ambi guity is because earlier workers depended mainly on one or two characters which were highly variable interspecifically if not associated with the changes in growth or sex. Day (1877, 1889) gave a comprehensive account of 23 species by using the anal fin counts, relative head length and eye diameter as diagnostic characters, besides the shape and size of teeth bands on the palate. Weber and de Beaufort (1913) also utilised the dentition pattern, besides the shape of the occipital process for separating the species of this genus. Smith (1945)considered the dentition pattern as one ofthe very important taxonomic character and stated, "the most important character for separating the species are teeth." Chandy (1954) framed a key mainly based on the dentition pattern on the palate, for the identification of Arius species present in the NZC of ZSI, Calcutta. Subsequent ichthyologists also relied upon this character (Munro, 1955 ; Smith, 1962; Wongratana and Bathia, 1974 ; Misra, 1976). Taylor (1978) adopted the length of the median 79 80 J R Dhanze and K C Juyarani
longitudinal groove on the head, the shape of the bony shield for separating Arius species of western central Atlantic (Fishing Area 31). It may b e seen that for separating the various species of Arius the pattern of teeth patches on the palate still remains to be an unavoidable necessity. How ever, it may be indicated that whereas the basic contour, the number and posi tion of the patches remain constant, the size, number and nature of the teeth themselves vary highly and alter considerably with age and growth. Earlier ichthyologists seem to be unaware of this fact and established species like A. serratus Day, A. malabaricus Day, A. satparanus Chaudhuri for such variants which are invalid (Jayaram and Dhanze 1978a~ 1981). Based on the number and contour of the patches we have placed the 21 species of Arius in six complexes under three groups. The constituent species of each complex are closely interrelated and some may even prow later either to be synonyms or subspecies. In this paper 'maculatus' complex which has four species (A. maculatus, A. arius, A. gagora and A. jella) (Text-figures 1A~H), have been analysed to determine their interspecific affinities and systematic status.
2. Materials and methods The material for this study is based on 430 specimens collected by the authors during extensive survey tours of the entire eastern. coast and ~ part of southwest
1:
A
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Text Figure 1 A.-A. maculatus (dorsal view of head). B.-A. maculatus (dentition). C.-A. gagora (dorsal view of hcadj .; D.-A. gagora (dentition). E.-A. arius (dorsal view of hoad). F.-A. arius (dentition), G.-A. [ella (dorsal view). H. A. jela (dzntition). (Figures A-E, G and H, after Chandy, 1953, Figure F-after Chaudhuri 1916). Biometric studies of the genus Arius 81 coast of India. The specimens presen t in the National Zoological Collections of the Zoological Survey of India, Calcutta, have also been examined. Fresh material of species SUC]1 as A. jella and A. maculatus were collected and studied by the second author (KC1) during the FAO consultation, Cochin in 1980. A total of 45 characters were mensurated and of which 20 alone are selected for the statistical analysis. All the measurements were taken with dial calipers to the nearesthalfof a millimeter for the size range upto 150 mm and by measuring tape abcve this size. Taxonomic characters are generally found to intergrade or overlap between closely related species when a large series of specimens are studied. The reliability or otherwise of such characters are to be evaluated. Different methods of measuring intergradation 01' divergence have been proposed (Davenport and Blankinship, 1898; Pearl, 1930; Ginsburg, 1938 ; Simpson and Roe, 1939 ; Amadon, 1949 ; Snedecor, 1956; and Simpson et at 1960). Methods deviced tby Simpson et al (op. ca.) for the comparison of two populations irr-espective of heir taxonomic identity seems to be useful here. The "Student's z-test " to determine the probability value at 95~ confidence intervals have been applied. Before deducing any ilUm<'lical conclusion, a hypothesis was set forth that all the specimens of different populations examined belong to a same species, and the univers .lly used rejection value of 5 per cent was chosen as a criteria for the rejection of tris hypothesis. However, the estabIisf-ment of the significance of a difference between two species by numerical derivation is not in itselfa zoological conclusion. Thus the numerical expressions for each character were further compared or rather standaridized by employing geometrical expressions proposed by Dice and Leraas (1936), and later on adopted with some modification by Hubbs and Perlmutter (1942), Pillay (1951), Hubbs (1952), and WiEterbottom (1980). In this method, for each character the range, mean, one standard deviation and one standard error on each side of the mean were delineated on the graph. The degree of overlap or sepal', tion of the standard deviations in respect of the arithmetic mean of each species Was determined.
3. Results
Tables 1-6 and graphs 1-20 present the biometric comparison of the four species with each other for ell the 20 characters selected.
3. 1. A. maculatus vs. A. arius
It is seen that excepting the head length, in respect of all other characters the two species have a probability of less than 0 '1% and are significantly different (table 1). From the graphs XIV-XVI, XVIII, XX, Dice diagram A and Bin each, it is seen that the mean of each population as well as standard deviation (S) diverge to a considerable degree, thereby justifying the separate specific status of A. maculatus and A. arius. Both the species have a single large oval patch of teeth on each side of the palate (tex t-figure 1 B, F). Further, the two species can be morpho logics lly distinguished by the size and position of the eye The eye diameter is 1&-50% ill Ai maculatus vs. 21·40% in A. arius in the hear: length; 33·30% lS 45·60% i.i the interorbital width and 57·35% vs. 63·30% in snout length, QC Table 1. Biometrical comparison of various morphometric data for A. macula/us vs, A, arius from different localities of east and west IV coast of India,
67 s",Jccimens of A_ macula/us (Thunberg) 81 specimens of A. arius (Hamilton)
------<...., Range Mean X1±SX 8, Range Mean x,±sx S. t P ::tl
LHjTL % 18' 60-25' 00 21-1238±'23 1,7656 18'87-24-32 20-7239± -18 1 '3642 1'3796 10--20% ~b ,;:, HBjTL % 15'13-21'58 18' 3448±' 28 1- 9319 13-52-21'50 16-3244± '19 J '4744 6-4097 <0'1% ~ 26' 7961 28 2-0935 1'3996 LHjSL % 23-29-30-12 ± - 24,65-·29'il8 26'6695± -18 0'4185 <60·70% '",." HE/SL % 18'75-26'97 n 9738± -28 2'0858 17'77-26'23 21' 0027 ± -21 1'6385 5'7282 <0')% ::> 7280 :::, PDL/SL ~~ 32-41-39-44 36'3168±'Z3 1- 35-2$-40'45 37'0227± '20 I' J529 - 2-6251 )'00% "---. PALj5L % 66,67-75'00 (i9'6174±-~12-)284 63-93-73-08 69'8702± '29 2'278 - 0-6025 <0-1% ='\ PPL/SL % 21 '72-30'~S ;~5'9972::!:'36 2"7055 22-40-27'41 24'707&± '1& 1'3965 - 3'28J7 0'1% ') 4,1754 WDFjWAF % 50'00-/2'22 59'7017±'55 52' 59-69' 70 61' 6339± -51 3'9983 - 2-5670 <1'00% 0..... WH/LH % 63'16-84' 09 n'8778±'6,1 ~,8220 62,60-78' 57 70,1412± '45 3' 51167 3-5376 <0-1% 2 § HH/LH ~~ 55' 26-71' 59 65' 4108± -57 4'2906 52'00-70'00 60' 6015±1' 26 4-7358 5'4483 <0'1% LSjLH % 28: OO~37'25 32' 3725±' 29 2-1.60J 30'00-37'00 33-8687± '21 1-6373 - 4'2560 <0'1% § BDjLH % 14' 7l-22' 22 13'4687±-21 J-5800 16'00-26'67 21' 3634± ' 29 2' 2268 - 7-9n6 <0'1%
INwjLH ~~ 17-91-23'86 2.1-2597±'20 1-5291 15' 29-21-77 lS'2822± '18 \ -4063 11'0167 -.o1'/'0 IOWjLH % ,H' 19-67' 39 56'1914±-67 4'5746 41'07-52:75 47'0943± '43 2-7251 12-8595 <0'\ 'io BDjLS % 39'47-66'67 57'3725±'82 6' 2239 43, 24-77 -78 63'3336±J '07 8'3560 4'3693 <0'\% INW/LS % 54-55-76- 67 {'5'9427±-aO 6-0087 44'64-61'90 54'0478± '55 4,3287 12' 3950 <0'1% INW/WS % 42' 86-57' 50 49'0378±'45 3'4019 40, 91-51' 22 46' 2846± ' 35 2,7336 4'860'3 <0'1% BDjIOW % 25-42-47-06 33'2938:1:'56 4' 2541 32'65-60'87 45' 6090± '86 6'7380 11,7740 <0'1% WPMTjLPMT % 15-00-22'22 19-0363et:'28 2' U50 16'67-30-00 23'7321± '38 2-9768 9'8383 <0'1% HCPD/LCPD % 47' 62-()3' 1:·1 :,3' 8982:1: 62 4,6490 38-54-59'65 49'S?]?±: '61 4'8020 - 4'9852 <0'1%
BD = Bye diameter i HB = height of body; HCPD = height of caudal peduncle; lIH = height of head; INW = inter-nostril width; IOW = inter-orbital width; LCPD = length of caudal peduncle; LH = length of head; LPMT = length of premaxillary band of teeth; LS = length of snout : P = observed probabilities for confidence intervals given in the Simposn et al(1960), Appendix Tab, n, for the corresponding ca'culated 'I' value; PAL = pre-anal length ; PDL = pre-dorsal length PPL = pre-pectoral length; Sl' S~= standard deviation of first and second population respectively; SL = standard length; sS':= standard error; TL = total length ; WAF = width of anal fin base; WDF ==width of dorsal Ul\ base WH = WIdth of head; WPMT = width of pre-maxillary band of teeth; XI'X~= arithmetic mean of the first and second population respectively. Biometric studies of the genus Arius 83
3.2. A. maculatus vs. A. gagora The two species differ significantly in respect of 14characters having the probability of less than 5% (table 2) and the standard deviation not overlapping with arith metic mean of the other in respect of 11 characters (Graphs I, II, V, XI-XIII, XV, XVI, XVIII-XX, Dice diagram A and D in each). A. gagora and A. maculatus have a single oval large patch of teeth on each side of the palate (Text-figure 1 B, D), though the teeth may be set sparsely in the former and densely packed in the latter. However, we have observed sparse arrangement of teeth in a few adult male specimens of A. maculatus also. Further, A. gagora is significantly different from A. maculatus in respect of eye size and internostril distance. The eye diameter in snout length is 57·37% in A. macu latus vs. 39·03 in A. gagora ; the internostril width in snout length is 65'94% vs. 48·17~. It may be mentioned here that in respect of the other so called significant characters such as predorsal length, width of dorsal fin, height of head etc., the difference is not very high. From the distributional pattern of both the species it would seem that A. maculatus is replaced by A. gagora in the Hooghly estuarine system,
3.3. A. maculatus vs. A. jella
From the data presented in table 2, itcan be seen that only in respect of 10 charac ters the probability is less than 5'-" and in respect of the remaining ten characters it is more than 5%. Among the significant characters, the least depth of caudal peduncle in its length is 53'89% in A. maculatus vs. 43·96% in Ai jella ; inter nostril width in snout length 65·94% vs. 60 ·42% and the size and position of eyes are noteworthy. Purther, A.jella is clearly separable from A. maculatus by the length of the pectoral spine which in A. jella is longer than the dorsal spine. In most species of Arius the pectoral spineis equal or shorter than the dorsal spine. We have examined specimens of a11 sizes in both the sexes in each species and have not found any variation in respect of this character (Graphs XII, XVIII~ XX, Dice diagram A and C in each).
3.4. A. arius vs. A. jella
These two species differ statistically in respect of ten characters in the fact that their- probability is less than 5%. Table 4 and Graphs XII~XIV, Dice diagram Band C in each, indicate the degree ofintergradation or divergence. Here again the size and position of the eye appears to be an important character. The eye in head length is 21·30% in A. arius vs. 15·95% in A.jella; in snout length 63·30% vs. 50·35%;. in interorbital width 45·60% vs. 33·90%. Purther, as stated already A. jeIla is separable by the character of pectoral spine being longer than dorsal spine as compared to other species of Arius. A.jella is darker in colour than A. arius. 3.5. A. arius vs. A. gagora The systematic position of these two species is slightly vague. A. gagora is not very well represented and apparently 110t collected extensively as A. anus. One ofUS (JRP) was able to obtain four fresh specimens (195..,245 mm SL) of A. gagorq 00 +:>. Table 2. Biometrical comparison of various rnorphometric data for A, maculatusfrom different localities of east and west coast of India vs, A, gagora from Hooghly Estuary,
67 specimens of A, l/lacllla!u~(Thu!1berg)18 specimens of A, gagora(Hamilton) ...... ~
RaTl~c Mean x1 ± sx --SI Rang!' Mean X2±SX S2 t P t:::l :::- l:l ;:: "l
~r~;. .LH/TL % 18'60-25'00 21'1238± '23 1-7656 22'41-25'38 23'7500± '87 1-5070 - 2-5120 l:l"" ~-(l.'(l\-%::s un.rr. % 15'13-21-58 18'S300±'34 2-3920 17, 24·-18'28 ]7- 6100± '33 0-5812 0'6050 ~ l.H/SL % 23·29-3(' -12 26'7960±'28 2'0935 27'66-29-28 28'8'7~()±'32 (;"7\ 68 - 2- ran "% .% >: HB/SL % IB'75~26-97 22'9738±'28 2'0858 19' 23-22'55 20'8680± '60 I' 3336 2'1883 ::- o (J 32'41~39'44 36'3168±'23 1'7280 For abbre, iations see table J_ Table 3. Biometrical compariSon of various morphornetric data for A. macula/us from different localities of east and west coast vs, A, jella only from east coast of India, 67 specimens of A, maculatus (Thunberg) 12 siecimens of A, jella (Day) ---~------ S~ f Range Mean X1±SX 81 Range Mean X2±SX P b:l 15' ~ ...... '" 80-~O% LH/TL% 18'6(}-'25'OO 21'1238±'23 ],7656 19'82-22'13 21' 0780± ,36 0' 8903 0'1433 r:;' HB/SL% 15'13-21.'58 18'5300±'34 2'5920 16'46-19'64 18'3533± '46 ]'1.381 0-16?-8 5~1% LH/SL % 23'29-30'12 24'67-27'94 26'0325± '45 ]'2626 0'9963 30-40% ""~ 26'7960±' 28 2'0935 ~ RH/SL % 18'75-26'97 22'9738±'28 2'0858 17'20-24'44 21' 3337± '77 2 '1917 2'0419 5% "" PDL/SL % 32'41-39'44 36' 3168±' 23 I, 7280 35'56-38'71 36-8312± '39 1'1093 -0' 8104 Mori' than "" 90% ~ ... PAL/SL 2,2873 60% ::::- % 66'67-75-00 69'6174±'31 2' 3284 65'71-72'07 69'0900± '81 0'5936 'll PPI/SL % 0'8171 2% 21'72-30'98 25'9972± '36 2-7055 22-38-24'71 23'6812± '29 2-3858 CXl ;1.,6487 ~3'8391 LesS tt,,·,- WDF/WAF% 50'00-72' 22 59'7017 ±' 55 4-1.754 62' 50-69' 23 6S'5857±l'OO :;:s'" 0'% ~ 3,6856 90% ~ WH/LH% 63'16-84'09 72' 8778±'64 4,8220 68' 27-78' 38 72'5950±1'30 0-1577 .., HH/bH 5,1389 V-,sstha,' % 55' 26-71'59 65'4108±'57 4'2906 50'98-66'67 58'3900±1'82 4'2014 ~' 0-1% LS/LH % 28'00-37' 25 32'3725±' 29 2'1601 27'45-34'62 31'9212±'98 2,7583 0'5248 60% ED/LH% 14'71-22'22 18'4687±' 21 r-5800 15'38-16'84 15'9662± '20 0'5620 4,4029 LeSS than 0'1% INW/LH % 1.7'91-23'66 21'2597±'20 I' 5241 15'69-23'16 19' 2425± -73 2'0512 3· 2888 0-1% IOW/LH % 44'19-67' 39 56'1914±'67 4'5746 41'18~50'OO 47'3887±1'33 3'7722 5'1410 LesS than 0'1 % ED/LS % 39'47-66'67 57'3725± '82 6'2239 44'44-57'14 50'3725±1'67 4'7330 3'0281 0,1% INW/LS% 54'55~76'67 65'9427± '80 6'0087 55' 56-70'97 60'4250±1-98 5'5894 2'4226 2~ INW/WS % 42' 86-57'50 49'0378±'45 3'4019 44'44~57'89 51'3862±1· For abbreviations sec table 1 Table 4, Biornetrical comparison of various morphometric data for A, arius from different localities of east and west coast of India 00~ vs, A, iella only from Crissa coast, 81 specimens of A, arius (Hamilton) 12 specimens of A, jella Day ~--- "-< Range Mean X1±S,X s, Range Mean x~±sx S4 / P ~ ~ l::l LH/TL% 18'87-24'32 20'7239± '18 1'3642 19'82-22'13 21'0780± '36 0'8903 -0-6157 50% ~ ","l HB/TI.l% 13' 52- 21'50 1.6-3243± '19 1'4744 16'46-19'64 18'3533± '46 1'1381 -3'2675 0'1%,9 l::l LH/SL % 24'65-29'48 26'6595± -18 1- 3996 24-67-27'94 26'0325:1:: '45 1'2626 I' 2031 20% ~ HB/SL % 17'77~26'23 21'0022± '21 1'6385 17'20--24'44 21' 3337± '77 2'1917 .-.0' 5171 60% l::l... ~ PDL/SL% 35'25-40'45 37'0227± '20 1-1529 35'56-38-71 36-8312± ·39 1'1093 0'4434 60-7°% PALjSL % 63'93-73'08 69'8702± -29 2-2278 65'71-72'07 69'0900:1:: '81 2'2873 0'9287 30-40% (j PPL/SL% 22'40-27'41 24'7078± '1.9 1,3965 22'38-24-71 23'6812± -29 0-8171 2-0258 'i% ~ - a '-.,: WDF/WAF% 52'59-69'70 61-6339± '51 3-9983 62'50-69-23 65-5857±I'OO 2·6487 -2,7090 1%.11 l::l .... WH/LH% 62'60~78-57 70'1412± '45 3-5157 58-27~73-39 72' 5950±1-30 3-6956 -1'8461 5-10% l::l HHjLH% 52-00-70'00 60-6Q15±I'26 4,7358 50'98-66'67 58-3900:1::1'82 5-1389 I' 2305 20% s LS/LH% 30-00-37'00 33'S687± -21 1-6373 27'45-34'62 31'9212:1:: -98 2-7583 2'8972 0'1-1 % ED/LH% 16'00--26-67 21'3634± -29 2'2668 .15-38~16-84 15-9662± '20 0'5620 6'6673 Less than 0'1%.11 lNWjLH% 15'29-21'77 18-2822± -18 1-4063 15-69-23-16 19'2425± ,73 2'0512 -1'7176 10% IOW/LH% 41-07_52,75 47'0943± '43 2,7251 41'18-50'00 47'3887±1'33 3,7722 -0-2744 80% EDjLS % 43, 24---77-78 63-3336±I'07 8-3560 44-44-57'14 50-372S±1-67 4-7330 4'2796 Less than 0-1% INWjLS% 44' 64-61'90 54' 0476± . 55 4-3287 55-56--70'97 6O-4250±1'98 5'5894 -3-7886 <0'1% INW/WS % 40'91-51-22 46-2846± '35 2'7336 44'44--57'89 51-3862:\:1'46 4'1209 -4.6628 <0'1% EDjIOW% 32-65-60-87 45'6090± '86 6'7390 30·77-40-00 33-9312:\:1'26 3-5598 4'7931 <0-1% WPMTjLPMT % 16'67-30'00 23'7322± -38 2'9768 18'18-31-82 25'3887:\:1'79 5'0591 -1-3513 20% HCPDjLCPD % 38-64-59'65 49-5717± '6J 4-8020 37'04-48'33 43-9687:\:1-40 3-7722 3-1670 0'1-1%JI .Por aoorevlations see table 1 Biometric studies of the genus Arius 87 from the river Hooghly at Serampore (W.B.) and eight specimens (120-185 mm SL) from Haldi estuary at Halida 1 art (W.B.). From a critical examination it is seen that A. gagora is clearly separable from A. arius by its shallow median longi tudinal groove which extends up to the supraoccipital crest as compared to A. arius which has the median longitudinal groove narrow extending only up to the frontal bones (text-figure 1 C, E). Besides, both the species differ in respect ofthe size of the eye which is larger in A. arius than in A. gagora ; the eye diameter in head length is 21·35% in A. arius vs. 14·95% in A. gagora ; in snout length 63·30% "Vs. 39'00% ; in interorbital width 45·60% "Vs. 34'25% Further, 13 charac ters having less than 5% probability indicate the statistical differences between the two species (Tab le 5 ; graphs, I, II, V, XI-XIV, Dice diagram B and D in each.) 3.6. A. gagora vs. A.jella Table 6 presents the comparative data in respect of A. gagora and A.. jelia. Nine characters showing the probability of less than 5% are delineated in the Dice diagram C and D (graphs I, II, V, VII, XI, XIII, XV). Morphologically the two species can be distinguished by the size and position of the eye and also the rela tive distance between the pairs of nostrils on each side. The nostrils in A.jella are closer to each other on either side than in A.. gagora. The eye diameter in snout length is 39'00,", in A. gagora "Vs. 44·45% in A.}ella ; the internostril width in length of snout 48'20% vs. 55·60%. 4. Discussion The above analyses of four species forming the maculatus complex of the genus Arius indicate clearly their close inter-relationship. Morphologically also these species resemble each other in one or other character and in juvenile stages they are hard to separate, more particularly since all of them have a single oval patch ofteeth on the palate (text-figure 1 B, D, F, H). The 20 characters which appeared helpful to differentiate these species were utilized for statistical interpretation and the extent of range of variation of each character was computed. The probability significance in respect of each such morphometric character as shown by each species is summarised in table 7. Of the 20 characters selected there is not a single character which can distin guish each species from the other. The size and position of the eye is most signi ficant followed by the internostril width, snout length and the least depth of the caudal peduncle. The body depth, head width, head length etc., the conven tional characters used by the earlier ichthyologists do pot <"ppear to re of much help, at least in respect of these four species. Considering the fact that the macu latus complex of species are inhabitants of clear oceanic and estuarine waters feeding on carnivorous diet in midwater, the differences in structure and position of the eye seems justified. Of the four species it is seen that A.. maculatus and A.. arius are well established separate populations, each occupying its own separate habitat. Thus A.. maeu latus is extensively distributed in the Arabian sea with stray individuals occasio nally caught in Bay of Bengal. A.. arius on the other hand is extensively found in Bay of Bengal havns not been so far recorded south of Portonovo. Moreover, Table 5_ Biometrical comparison of various morphometric data for A, arius from different localities of east and west coast of India 00 00 vs, A, --gagora only from Hooghly estuary, 81 specimens of A, al'ills(Day) 18 specimens of A, gagora (Hamilton) ..... Range Mean Xl-+SX s, Range Mean X2_+.tr S2 1 P ~ ~b l:l LH/TL% 18' 87-24' 32 20'7239± -18 1-3642 22-41-25-38 23'7500± '87 1-50'70 -3 '8275 Less than :::: O-J% '"~ HB/TL% 13' 52-21 -50 16-3243± '19 1'4744 17'24-18'28 17-6100± '33 0'5812 -1-4950 10-20% l:l :::: LH/SL% 24- 65-29- 48 26'6595± -18 1-3996 27'66~29'5728-8740± '32 0'7158 -3'4826 0'1% ~ HB/SL% 17-77-26'23 21'0022± -21 1-6385 19'23-22-55 20-8680± '60 1'3336 0-1779 80-90% ~ PDL/SL% 35'25-40-45 37'0227± -20 1-1529 37'45-42-07 39'4160± -77 -1-7134 - 2- 5898 1-2% (j PAL/SL~ 63-93-73'08 69-8702± '29 2'2278 70'61-74'52 71' 9540± -73 1-6371 -2-0402 5% ~ PPL/SL% 22 '40-27' 41 24'7078± -18 1-3965 25'53-28-83 26' 5642± -59 1'3234 -2'8667 1% ~ WDFjWAF% 52'59-69-70 61- 6339± -51 3-9983 57-89-71- 43 65'5316±2-51 5-6225 - 2'0343 5/' ~ WH/LH% 62'60-78-57 70'1412± '45 3'5167 65-15-76'92 71'3142±1'95 4'3687 -0,7051 50% ~ HH/LH % 52'00-70'00 60'6015±1-26 4'7358 53' 66-67 -69 59-2222±2'61 5'8275 0-6162 50-60% LS/LH% 30'00-37'00 33'8687± '21 1-6373 37-40-41-54 38-6443± '74 1'6519 -6-2666 Less than 0-1% ED/LH% 16'00-26-67 21'3634± '29 2'2668 13-64-16'18 14'9624± '52 1-1614 6-2152 0'1% INW/LH% 15'29-21'77 18-2822± -18 1-4063 17-65-19-70 18-5842± -33 0-7375 -0'4724 60-70% IOW/LH% 41'07-52'75 47'0943± -43 2-7251 42'11-45'45 43'7321± '56 1-2436 2'7204 1% ED/LS Y. 43, 24-77 '78 63' 3336±1- 07 8'3560 36' 00-42 -86 39'0343±1-46 3'2731 6-4235 Less thar 0'1% INW/LS% 44'64-61-90 54'0478± -SS 4'3287 44'44-52-00 48-1741 ±1' 34 3'0009 2- 9655 0'1-1% INW/WS% 40-91-51'22 46'2846± -35 2'7336 46-15-56'52 50'5662±l'99 4,4440 -3'2064 0-1% ED/IOW% 32'65-60-87 45-6090± -86 6'7380 30'00-37-50 34' 2721±1'49 3-3272 3'5588 Less than 0-1% WPMT/LPMT% 16'67-30'00 23'7322± -38 2'9768 23-33-31-25 25'9160±1'37 3'0682 -1- 5739 10% HCPD/LCPD% 38'64-59'65 49-5717± -61 4-8020 40-00-46-75 42'9453±1'38 3-0915 3-0222 O'I-l% For abbreviations see table I Table 6, Biometrical comparison of various morphometric data for A, gagora from I-Iooghly estuary vs. A jella from Orissa coast. 18 specimens of A. gagora (Hamilton) 12 specimens of A. jella Day -_._. Range Mean Xl± SX Sl Range Mean )(2 ± SX S2 t P ttl 0 ::;. ~ ..., LH/TL% 22'41-25'38 23'7500± '87 1'5070 19'82-22'13 21' 0780± '36 0'8903 3'2787 1% ~. HB/TL% 17'24-18-28 17-6100± -33 0'5812 16'46-19'64 18'3533± '46 1'1381 1-03(j9 30% LH/SL% 27-66--29'57 28'8740± '32 0'7158 24' 67-27' 94 26'0325± -45 1'2626 4-5485 Less than l2'" I:l.. O'J% (;;. I-IB/SL % 19-23-72'55 20'8680± '60 r-3336 17'20-24'44 21'3337± ·77 2' 1917 0'4244 60-70% '" PDL/SL % 37'45-42-07 39'4160± '77 1'7134 35'56-38'71 36'8312± '39 1'1093 2'4500 2-5% ~ 73 PAL/SL /'~ 17'61-74-52 71-9540± '73 1'6371 65'71-72'07 69'0900± -81 2'28 2'4215 2-S% s PPL{SL% 25'53-28'85 26' 5642± '59 1'3234 22'38-24'71 23' 681.7± .29 0,8171 4·8618 Less than '" O'1'Y I)q :: 57' 89-71 '43 65'58S7±l'OO 2'6487 -0'0237 More than '" WDF/WAF% 65'5316±2'51 5'6225 62'50-69'23 <:;; 90% WH/LH% 65'15-67-92 71'3142±1'95 4-3687 68':17-78'38 72' 5950±1' 30 3'6856 -0' 5691 60% ::t...... , HH/LH.% 53-66-67-69 59'22n±2'61 5-8275 50'98-66'67 58' 39CO±l'87 5'1389 0'2703 80% i:: "" LS/LH% 37-40-41-S4 38'6443± '74 1'6519 '27'45-34'62 31'9212± '98 2'7583 4'8825 Less than 0'1% ED/LH% 13' 64-16'18 14'9624± '52 1'1614 15'38-16'84 15'9662± '20 0'5620 -2'1174 5°'/. INW/LH% 17'65-19'70 18-S842± '33 0'1375 15'69-23'16 19'2425± -73 2'0512 -0'6825 50% IOW/LH% 4'2'l1-45'4S 43'7321± 'S6 1-2436 41'18-50'00 47'3887±1'33 3'7722 -2'0682 5-lO% ED/LS% 36'00-4:1'86 39-0343±1'46 3'2731 44'44-57'14 SO'37:.'5±l'67 4'7330 -4'6820 Less than 0'1% INW/LS% 44'44-52'00 48'1741±1'34 3'0009 55'56-70'97 60'4250±1'98 5'5894 -4'4657 0'1 /'~ INW/WS~ 46-1S-S6'52 SO'566:1±l'99 4'4440 44'44-57-89 51'3862±1'46 4'1'209 -0'3391 70% ED/IOW~ 30'00-37'50 34'2721±1'49 3-3772 30'77-40'00 33'9312±1'26 3-5598 -0'1719 80-90% WPMT/LPMT~ 2'3'33-31'25 25'9160±1'37 3'0682 18'18-31'82 2S'3887±l'79 5-0591 0'2083 80% Hq>D/LCPD~ 40"00-46'75 42'9453±1'38 3'0915 37' 04--48'33 43'9687±1'40 3"7712 -0'4069 60·70% 00 \0 For abbreviatioDS see table I ;g Table 7. ProbabilitY dist;ribation of various morp!lometric charactor in respect of si" combination. of the (OUl' species: A. maculae., A. arius, A. gagora and A. Jella. - A. macula//4s A. macl/lafl/S A. macu!afus A. (lrius A. or/us A. gagora <, vs· liS. vs. vs. vs. vs. ~ A. arius A. gagora A..jet/a A.. gagore» A. jella A.1el1a t:s~ (%) (%) 00 <%l I%> <%> ~ l.. LH/TL % 10-20 20 80--90 < 0'1 50 1'00 !i"" HB/TL % <: 0'1 50--60 50 10-20 o-r 3 c .11 vu ! zo 17 ~ A •• o __ Lc.- ---I 0 D I C· J I VIII ! ! I -64 7. 76 50 ,. S' s. 00 ,; 62:" 00 70 n .. WOf. WAr:· '" Graphs V~VHl Blomctric studies of the genus Arius 93 , Ui" P'(B)-lO J R Dhanze and K C Jayaram • I I l o Ib_DJ XI" I .., .. •• .. 7l •• • -, c~ e LIIr;;:. =--=:::I XIV zo u 21 3 l •• 52 . , c=• . r==- • e I•• I 1 XV • 0 ... •• .. .. 1J .. 10 • • c ~J t D IU':::JIIII::::L.I XV I ,. 11 11 It n •• "1Nl0-H~ " 20 Graphs xm-XVI Biometric studies of the genus Arius 9S A • • ... p 11 XVII 4Q 42 <6 41 so 52 ,. 56 58 /IQ 62 64 66 •• INW0WSO,' A l..--L_.JL_=:LJ • =- L----L ==:l-J 0 ~::::L_ '" XVIII I I I ... 16 20 22 rjt.< 2. 28 se J2 3< l' " WPMT. LP"'tTj Table 8, Showing the extent of intergradatlon in respect of five morphometric characters in A, gagora vs, A, [ella, Length of head as percentage of total length \0 Species 0\ 19'00-19'95 20'00-20'95 21'00-21'95 22'00-22'95 23'00-23'95 24'00-24'95 25'00-25'95 Intergradation A, gagora 33'33 33-33 33' 33 24' 995% ==Subspeclflc status A, jella 16'66 33·33 33'33 l6'66 ..... ::t; Length of head a~percentage of standard length :::-tl Species § 24'00-24'95 25'00-25'95 26'00-26'95 27'00-27'95 28'00-28'95 29'00-29'95 Intergradation '"'1> § A, gagora 20'00 80-00 22' 50 = Subspecific status ~ A, jella 37'50 12'50 25'00 25'00 ~ (") Pro-dorsal length as percentage of standard length ~ Species '-0::: :;:;, 35'00-35'9536'00-36'95 37'00-37'9538'00-38'95 39'00-39'95 40'00-40'95 41'00-41'95 42'00-42'95 Intergradation .... § A, sasora 20'00 20'00 40'00 20'00 16' 25% ==SUbspecific status A, jella 25-00 37'00 25'0') 12' 50 Pre-anal length as percentage of standard length Species 65'00 66'00 67'00 68'00 69'00- 70'00- 71'00- 72'00- 73'00- 74' 00- Intergradation 65'95 66'95 67'95 68'95 69'95 70'95 71'95 72'95 73'95 74'95 A, sasoro 40'00 20'00 20'00 .. 20'00 25'00% ==subspe- ciflc Status A. je/la 12'50 12'50 12' 50 12' 50 25'00 12'50 12' 50 Eye diameter as percentage of length of head Species 13'00-13'95 14'00-14'95 15'00-15'95 16'OO~16'95Intergradation A. sasora 40'00 40'00 20'00 A, iella 50'00 50'00 30'00% Diametric studies of the genus Arius 97 A. arius is an inhabitant of brackish water lakes such as Chilka, while A. macu atus seems to prefer deeper waters of the open seas. It would seem that A. macu atus is replaced by A. arius in the Bay of Bengal north of Coromandel coast. A. gagora is found in the Hooghly esturaine system and is known from compa ratively lesser saline waters than the other species of this complex. It is most closely related to A. jella which is also known from Orissa and Bengal coast. It is clearly separable from A. maculatus and A. arius by the relative extension of the median longitudinal groove, besides size and position of the eye (Vide supra). The data of probability distribution depicted in table 7 substantiated by Gins hurg's method of analysis (table 8) would seem to indicate that A. jella is only a subspecies of A. gagora. Pending further studies with the fond hope of obtaining more material of these two species, we have kept A. jella as a separate species for the present. It is concluded as such that A. maculatus complex comprises of four species: A. maculatus (Thunberg, 1792), A. arius (Hamilton. 1822), A. gagoro (Hamilton, 1822) and A. jella Day, 1877. Acknowledgement We are thankful to the Director. Zoological Survey of India, Calcutta, for facilities. References Arnadon D 1949 The seventy five per cent rule for subspecies ; Condor 51 250-258 Chandy M 1954 A key for the Identification of the catfishes of the genus Tachysurus Lacepede with a catalogue of the specimens in the collection of the Indian Museum (ZoJI. Surv.); Rec. Indian M/IS. 51 (I) 1-18, 3 pls. text figures. Devenport C Band Blankinship J W 1898 A precise criterion of species; Science (N.S.) 7 684-695 Day F 1877 The fishes of India; London, Wm. Dawson and Sons 778 pp. 198 pI' Day F 1889 The fauna ofBritish India including Oeylon and Buma, Fishes 1 169-192, Taylor and Francis, London Dhanze J Rand Jayaram K C 1979 The family of catfishes of the genus .. Arius " (Siluriformes) ; Curr. Sci, 48 (22) 1008 Ginsburg I 1938 Arithmetical definition of species, subspecies, and race concept with a proposal for a modified nomenclature ; Zoologtca 23 253-286 Dice L Rand Leraas H J 1936 A graphic method for comparing several sets of measurements, Contribs. Lab. Vertebr. Genetics, Univ, Mich, Ann. Arbor. 3 3 Hubbs C Land Perlmutter A 1942 Biometric comparison of several samples with particular reference to racial investigations; Amer. Nat, 76 582-592 Hubbs C 1952 A contribution to the classification of the blennoid fishes of the family Clinidae with a partial revision of the eastern pacific forms; Stanfard ichthyol, Bull. 4 (2) 41-165 Jayaram K C and Dhanze J R 1978a Siluroid fishes of India, Burma and Ceylon. 21. A note on the systematic positron of Tachysurus serratus (Day) (Arlidae) ; Bull. zool, Surv, India 1 (2) 203-205 Jayaram K C and Dhanze J R 1978b Siluroid fishes of India, Burma and Ceylon 22. A preliminary review of the genera of the family Ariidae (Pisces: Siluroidea); Matsya 4 42-51. P.(B)-lOa J R Dhanzc and K C Jayaram Jayaram K C and Dhanze J R 1981 Siluroid fishes of India, Burma and Ceylon. 23. The specific status of Tachysurus malabariucs (Day) (Ariidae); Bull. zool. Surv. India 4 (I) 121-123 Misra K S 1976 The fauna of India and tI'e adjacent eoIll/tries, Pisces, 3 xxi -I- 349 pp, 2nd ed, Munro I S R 1955 The marine and Freshwater fishes of Ceylon, Canberra, xvi + 349 pp. Pearl R 1930 Introduction to Medical Biometry and Statistics, Philadelphia and London Pillay T V R 1951 A morphornetric and biometric study of the systematics of certain allied species of the genus Barbus Cuv. and Val.; Proc. natn. Inst. Sci. Inida 17 (5) 331-348 Smith H M 1945 The freshwater fishes of Siam or Thailand; Ball, U.S. Natn, Mus., Washington (188), xi + 622 pp. Smith J L B 1962 Fish from the cape described by Liethtenetein 1833; S. Afr. J. Sci. 58 39-40 Simpson G G and Roe A 1939 Quantitative zoology, New York Simpson G G, Roe A and Lewontin R C 1960 Quantitative zoology New York, Rev. ed. Snedecor G W 1956 Statistical methods applied to experiments in agriculture and biology, 5th Ed. Anus Iowa, Iowa State ColIge Press Taylor W R 1978 FAO species identification sheets for fishery purposes Western Central Atlantic (Fishing Area 31) Rome 1 Weber M and de Beaufort L F 1913 The fishes of the Indo-Australian Archipelago Leiden 2, xx +404 pp. Winterbottom R 1980 Systematics, osteology and phylogenetic relationships of fishes of tho osteriophysan subfamily Anostomlnae (Characoidei, Anostomidae) ; Life Sciences Contri bution Royal Ontario Museum 123 Canada Wongratana T and Bathia U 1974 FAO species identification sheets for fishery purposes Eastern Indian Ocean (Fishing area 71) Rome 1 Graphs I-XX. Dice diagram showing the intergradation and divergence in respect of 20 characters in the four species of the genus Arius, In each diagram, the hori zontal base line indicates the extreme range; the vertical line in the middle repreSents the arithmetic mean ; the solid area on either side of the mean is the extent of One standard error; the hollow area delimits one stei dard deviatior on either side of the mean; the hatching lines represent the extent of standard deviation beyond the extreme range.