MARDI Res Bull. 4, 2: (51

" Part II.

62)

BIOLOGY OF ANGELFISHGrowth and Maturation of the Gonads

ANG KOK JEE

Accept<:d for publication on l9 November, 1974

RINGKASAN

Tumbesar dan kematangan gonad Angelfish telah dikaji di dalam kolam yang besarnya0.01 ekar (0.004 hectare) . N{orphologi umum bagi obar i dan test is jenis ikan in i te lahditerangkan, 'Oocytes' telah dibagikan pada empat peringkat, iaitu 'Oocyte I. Oocyte II, OocyteIII dan Oocyte IV'. Di dalam testis sel-sel yang bciikut dapat dikcnali 'primary germ cell,spermatogonia, spermatocyte, spermat id dan spermatozoa' . Setelah pemeriksaan histo logicaldilakukan didapati bahawa 20% lkan betina dan 40% lkan jantan telah mcncapai kcmatanganpada 130 har i dan 4.5 cm. panjang. Ket ika berumur 160 har i dan panjangnya 5.18 cm. semuaikan-ikan ini telah mencapai kematangan. Telur-telur telah didapati mengalami process"regression" dan sperma mengalan, i process'phagocytosis ' bagi ikan- ikan yang t idak membiak.Kadar tumbesar masih ccpat bagi ikan-ikan peringkat alval. Ikan ini jenis maun. "Fecundity"yang t inggi te lah diperhat ikan bagi ikan- ikan yang berukuran 5.0-5.5 cm..

INTRODUCTION

The Angelfish (Ptuoph.vllum eintekeifscalare) is native to South Arnerica. The breedingbiology and larval development of this species has been discussed in part I of this series (ANGand LIM, 1914). This present paper deals with the growth and maturation of the gonads ofAngel f ish stocked in a 0.0 i acre (0.004 ha.) pond at M.A.R.D.L Stat ion. Batu Berendam,Malacca. The biology of Angelfish must be cleariy understood to properly rnanage andinvestigate the rnass culture of this species. One of the aspects of its biology which has notbeen docuurented in l iterature is age at f irst spawning.

The ecology and taxonomy of th is species has been g iven by Lon' l NIcCONNEL (1964.1969). ANG (1973) has studied the reproductive biology and growth of some MalaysranAnabantid fishes. It is hoped that this study wil l be useful for further investigation into thebiology and rlass culture of Angelfish.

MATERIALS AND METHODS

The specinrens used for this study were taken from the brood which spawned onSeptember 12, 1912. A batch of 150 young Angel f ish were stocked in 134 pond (0.004 ha.) onOctober 30, 1972. The fish were not given any supplerncntary feed. The pond was treated with

150 gT of P, O, rnonthly. l 'en flshes were randomly sampled from this pond at monthly

mtervals.

The conditions of the gonads were noted and sections were prepared according toGunR's method,(1956). Immature ovaries and testes were fixed in Bouin's fluid. Bouin's fluidwas not suitable for f ixing ovaries with yolky eggs, as the eggs crumbled during sectioning.However, it was found that Srrrith's Formal -Bichromate fixative (uide PnNrlN, 1964) rvassuitable for fixing such material. The different stages of the eggs and male gen.n cells wereexamined and rneasured with a lt l icronteter under a conpound microscoDe.

) l

1\' lean specific grorvtlrra tc (S .G.R. ) rvas c l l cu la ted us ing thc fonnu la ( r , i r l c S lv l r r l . 1955) :

S . G . R . = 1 n L 2 1 n L 1 o r l n W 2 l n W l x 1 0 0

T : - T t

rvheie L2 or W2 rcprcsents lcngth or ' ,ve ight at t inre T2 ancl L1 or W1 represel t ts length orweight at t i l l le T ' . Tr is la ter than T1. The t inre is ureasurecl in r iccks, so that the S.G.R. isexpressed as percentage length or rvc ight per week.

About 30 mature fernale flshes were also dissccted so that their gonads could be studied.The ovaries were flxed in Gilson's tluid for egg counts. The length and rve.ight oi-the fishes wcrealso recorded. This was to dcternr ine wl ie ther there was anv corre lat ion benvcor ess nuni t rcrand s ize of the f ish.

RESULTS AND DISCUSSIONMaturation of the Gonads

General N{orphology of the Ovary: The ovary ol Angelfish is a pairecl, lobulated strLlcturc.ly ing in the poster io l region of the body cavi ty , dorsal to thc gut . Each lobc of the ovary iscovered wi th v iscera l per i toneurn. Bencath the per i toneunr is a capsulc of connect ive t issues audsmooth rnuscles, the tunica a lbugenia. Dorsal ly they are held by t l re uresovar ia.

Basal ly the two lobes of the ovary are fused and lead into a shor t s ingle ov iduct whichopens outs ide through a t ransverse s l i t . the geni ta l aper ture in the body wal l . poster ior to theanus.

General Morphology of the Testis: The testis of Arrgelfisl i occupies thc sarne lrosition as thcovary. It is paired and elongate. The twc; lobes of t l.re testis are frec distallv and lusecl basally.They are suspended dorsal ly by the mesorchia. Each lobe g ivcs r ise to r l rc sperni c luct whichruns along the dorso-ntedian margin (lr ig I ) These ducts elnerge frorrr rl ie blsal end ol thetcstis and combine to form a median duct which then is joined bv rhe ureter and opensouts ide through the ur ine-geni ta l apcr ture. Both lobes of the tcst is ntav bc as l , rnnrct r ica l orsyrnnletrical in shape. T1.re gonadal blood vessels are situatecl dorsal to thc lrcsorcli ia.

The bulk of the testis is cor.nposed of lobules or tubules of various sizcs and forrns /1.)gI ) . Tbe lobules which contr t runicate d i rect ly wi th the sperr l duct , branch profusely to forrn amesh of lobules of s l lght ly sr la l ler d ianreter and const i tu te the semini ferous tubulcs. The lobulcsarc separated front one another by a thin connective stronta containing clastic f lbres (l. ig 2)Lobule boundary cel ls are present in the lobules ( f ig . 2 ) and are apparent ly endocr ine infunct ion as in Couesi t ts p luntbeus (AnSAN, 1966).

Generally, the younger stages of the gernr cells are arranged along the periphery of thctestis (towards the ventral sidc) and the later stages occur trrrvards the inner nrargin of thelobules (towards the dorsal side). encloscd in separate cysts l l.:: igs. I and 2). Cells in one cystbelong to one spenltatogenetic stage and except for the earlicr divisions of the spermatogonia,the eienrents in one cyst belong to one stage and divide in an all or none fashion, as lnSalvel inus font i tn l is (Hl .Nt t l iRSoN. 1962). Unl ike Lepont is nwcrutchi rus (MATr{ l .ws, 1938),M.t :s tus seenghala (SATl lYANIrsArr* . 1959). and Couesius p lutnbeus (AHseN, 1966), theposterior region of the testis in Angclfish is functional. ,

For the sake of sirnplicity and rather aibitrari ly, thc gonads of Angelfish are classifiedinto immatt t re gonads. ntatur ing gonads and urature gonads. The var ious stagcs of the oocytesare c lass i f ied in to four s tagcs - Oocyte I . Oocyte I l . Oocyte I l l and Oocyte IV.

5 2

I,'igtrc l. Angelf'islt: L.S. ttJ testis shottirtg spennatozoalront 190 t lal 's olt l . f is lr /5.7 cnt. statrclanl lutgth). jS7X, 6attt l l ' .osit t .

in the lobulesmicrons, Hae

t:"#.F Teffiry

# - *

:F iff i ' .e. e as::5.

$permatogonta

Figurc 2. Angc$ish: L.S o. l ' tasl is slu. lr ' i r tg the rt tature sperms in the

lobulcs, prirrwr.r' gt'rnt calls, sperfttotL)gonia, spernwtids arul spemtatctcvtes.

(1.8 cnt. stanclanl length). )00X,6 rrt icft tns, Hae atul Eosirt .

lmmature Gonads: Fisl"r nreasuring 3.310.06 cnr. in standard length and 1.5010.08 g. in weighthave immaturc gonads. The fishes wcrc then about 70 davs old. The testis and ovaries arethrcadlike and transparent, situated in the bcldy cavity, dorsal to the gut.

6t&.lIr

Figure J. ,Tngelfish: L.S.oLts'y'7g5 .fnttt 100 tla.t 's rt lcltrt icrorts. Hae arul Ectsitt.

().f ot'ary s/tox'ltg tltc oyoCoel uttcl sluge

lish (-1.4 tnt. standurtl lt'rtgth). l-:0.\'.I6

[-igtre 4. Artga(islr: L.S. ctf ovarv shoruirtg stugcs I attd II ooc-r'tes Jionll-10 clat,s old fislt (4.5 <:rtt. stanLlard lettgth ). 44X,6 rnicrons, Hue ancl Eosin.

Maturing Gonads: Fish measuring 3.810.14 cm. in standard length and 2.25!0.68 g. in weightpossess maturing gonads. The fishes were then 100 days old. In longitudinal section, the ovary(stage I Ovary) possesses nunrerous Oocyte I individuals which take up uniform staining withHaerrrotoxy,l in and Eosin, (FiS 3) The ovary possesses definite distinct ovocoel (ovarian cavity,l . ' ig . 3) An inc l iv idual oocylc I nreasures between 0.02 0.07 nrm. in d iarneter . I t has a largenrrcleus (0.01 0.05 nrnr. in dianreter) with distinct nucleoli around its periphery. The testis ofthis stage porsesses nrainly prinrary gernr cells and spernratogonia.

"-{ i l&t'

Y

!d:

M3

) 4

Figrre -t. Angeffish: L.S. of ovary shorring stage III oocytes lrom 130tla.vs old lish (4.5 r'm. standard lertgth). 150X, 6 microns, Hae antl Eositt.

F ish measur ing 4.510.5 crr . in s tandard length and 5.510.18 g. in weight a l ready possessedstages II and III gonads. The fishes were then 130 days old. Some of the fishes were mature bythis stage and possessed stage IV gonads. Histological examinations of the gonads'revealed thatabout 40% of the male and 20% ol the f'emale fishes were already mature (Fig. 10), However,majority of the gonads were sti l l in stage III. Some of the fishes sti l l had stage II gonads. Inlongitudinal section, the ovary of this stage has a reduced ovarian cavity due to the enlargementol the ova (Fig 4) Oocyte II is covered b1, a distinct layei of foll icular cells (not seen in Flg4) and possesses vacuoles in the pei ip l iera l cytoplasrn. The ovul .n u leasures between 0.08 0.22mm. in d iameter . T l tc vacLto les in the cytoplasnr of the oocytes are probably t l ie or ig inal l ipo idvesic les as rcpor ted ear l ier b1, BRALKIVt ,LT and McMtt- t -AN (1967) in f .ucal ia , which havebeen dissolved during histological preparation. In stage II Ovary, there are also numerousOocytes | (l: ig. 4). In a longitudinal section of the testis of stage II, the following cells arerecognised prinrary gernr cells, spernratogonia and sperutatocytes.

Stage III Ovary (l: ig.5i bears Oocyte III, nreasuring 0.28-0.48 mm. in diameter. Thisstage is characterised by additional deposition of yolk (appeared as darkly stained area in thecytoplasrn, I: ig 5) The nucle ar nrenrbrane becomes indistinct and the nucleus contains manynucleoli ( lt ig 5) The cytoplasm becornes urore vacuolated (l '- ig. 5/ and the egg membrane isdistinct and acquires an outer layer of vitell ine urernbrane (f ig 5)

The longitudinal section of the testis of 1 30 days old fish indicates that soure of thelobules have mature sperms. Five distinct types of male germ cells can be distinguished in fishof thisl age. They are the prirnary gernr cells, spemratogonia, spermatocytes. spermatids andspermatozoa. The prinrary gernr cells are found in the walls of the lobules (Figs 2 and 3).These are large cells and are found either singly, in twos or in threes (Fig 2) They rneasureaborrt 7.5 microns in diameter. Spermatogonia are groups of cclls arranged in cysts in thelobules (FiS 2) Each spermatogoniunt is spherical and contains a small, round, dark-staining,

5 5

F-igrre 6. AngclJislt. L.S. oJ testis shov,itlg matLtre spenns in rhe ktbules.frorrt 160 Lia-t's oltl lish (1.8 cnt. sturttlartl length) 1,t0.\', 6 microns, Haeand Eositt.

centra l ly p laced nucleus which lneasures about 5 nt icrons in d ianrcter ( l : ig . 2) . NIatHfus(1938 ) , JAN{F .s (1946 ) and Se t t t vANt . . sAN (1959 ) no tc t he d i f f i cu l t y i n i n te rp rc r i ng t hcdi f ferent s tages of gernt ce i ls . par t icu lar ly the pr imary ancl secondary spennatocytes. Sinr i larproblern was encountered in the Angel f ish. The nucle i o f the spernlatocytcs u leasure about 4tn icrons in d iameter / f ig 2 ) and are crescent ic in shape. Spcrnrat ids have rouncl ntuc lc inreasuring about 3.5 rtt icrons in diarneter. The r.nature sperniatozoon has a clecply stairrccl rounclhead and has a nuclear diameter of 0.20 2.f microns (l: ig. 2). A\ thc spr.rnrat()1ol alc folrled.the thin wall of the cyst disintegrates and liberates the spcrniatozoa rnto tl ie lobules i l: igs. |, 2and 6).

Mature Gonads: Fish measuring about 5.1810.01 cnr. in standard length and 7.78!0.3) g. arealready mature. They are about 160 days old. The ovary is in stage IV with nrainly Oocyte IVmeasuring about 0.6-0.9 mm. in diameter (tt ig 7) and occasionally as large as 1.1 rnm.. Theegg is yolky and the cytoplasm stains pink. Though Oocyte [V are dominant in stage IVovaries, there are also nests of imr.nature oocytes of different sizes.

In male fish of this age, the testes appear swollen and the lobules are fi l led withspermatozoa /Fig 6). There is a general reduction in the numbcrs of the early stages ofdividing germ cells.

Atresia: Atresia occurs at any stage during the deveiopment of oocytes. This is a cotnmonphenomenon in the mature ovary whereby the unspawned oocytes are renroved. Atresia is notobserved in Stage I ovaries. Atretic oocytes may be found in stages II IV ovaries. Horvever,they are more common in stage IV ovaries (FigS). Similar conditions were reported b|CuNNtNcnau (1897 ) , JRv rs (1946 ) , BnRcn (1959 ) , SRrHyeunsAN (1962 ) andB R A E K E V E L T a n d M c M T L L A N ( 1 9 6 7 ) .

Sex Ratio: As stated earlier, ten fishes were sarnpled monthly from tl.re J-pond. The resultsindicate that about 50% of the population consists of male fish and thus the sex ratio is 1 :1.

5 6

fr

I : igrrc 7. . , lngcl. f isl t . L.S. (t ()t 'arJ'

du.t's oltl .lish 11.-t (rt. st0nLldrd lcttgtlr).

i/rr.,rr'ing stogc II o()c.t,tcs Jrottt l -)(.)

I -,<(.))', 6 ntit'rotts, Ilae atrcl L.'ositt.

b *

F' iprc 8. Attgcl. / isl t : L.S. o.f ot 'ar1, slult ' i r tg s()ntc o. l t l te eggs uttdergoin!:atrcsio onLl cntpt. l t . l l t l l i t ' l t 's. front 190 t la.t ,s olt l . f is lL. 44X,6 trt i t ,rorts, Haaut td I ' ,os iu .

5 7

Growth: The growth pattern in Angelfish is shown in I;igure 9. In general, growth of this fishfollows a normal growth pattern for fishes. They attain rapid gains in length and weight untilreaching 130 days old. Subsequently the growth is rnuch slower. The maximum growth rate is.howerler, during the first 70 days of the fish life as indicated by the specific growth rate curvein Figure 12. This is in correlation with the maturation of the gonads of the fish whichindicate that by the time the fish is about 130 days old, the gonads are already in a nraturingor a mature stage /Fig 10i. Similar growth pattern was observed in other species (ANG, 1973).The rapid increase in weight is apparently due to the physiological processes associated withdevelopment of gonads and external structures, such as fins, in early l i fe. Such development iscorrelated with the uti l ization of large amounts of energy. Thus, maximal weight increase isattained during the init ial maturation. The maturation of Aneelfish within 130 to 160 daysconfirms NIKoLSHY'S (1963) view that small f ish attain sexual maturity early.

Maturity/Iength/Weight Relationship: Figure ./0 represents the relationship between maturity,length and weight for male and female fish. It is evident that males start maturing at about4.52 cm. in standard length and females at 4.54 cnr. in standard length. At this stage of

1 0 , 0

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' o e Q ' ' ' . . ; . ; : " : ' : ) " . . .

160

Age (days)

f igurc 9. (irov'th itr AttrclJish.

100

58

r90

t2

r . . " . . . r Length rna le

.- Length female

L ---. Weight female

r_.-d, Weight male

ts < Percentage of mature male

o....-< Percentage of mature female1 0.)

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boo , ,

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€-5

a a a a a

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a a - a a a a a a

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r 0 0

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Figure 10. Angelish. Relation of muturitl

I l 0 160 190 l l 0Age (days)

to lcngth attd weight in male and .female Attgcffish

developrrrent about 40% of the nrales and )07t of the fenrales are already nlature (see earlier).At .1 60 days o ld, a l l male and female f ishes beconie mature. There was a faster growth in lengthand weight in tJre male fish after the onset of rnaturity (I"ig. l0). Tlie fentale fish seerns to loseweight when i t reaches the age of 190 days. This rnay be at t r ibuted to the loss ofeggs throughregression. In several cases, it has been observecl that "f ish becoure mature at a size which issome rather constant proport ion of thei r f inr l len; : , th" ( I lo t r , 1962). BEVERToN and HoLT(1959) have conrpi led the rat io of rnean length of rnatur i ty to the asymptot ic length (1nr /1-)for various species of f ishes and found thc variation, which ranges front 0.3 to nrore than 0.9,to be considerable. In the present instance i t is observed that 1m/ l* in the case of nra les andfemales is 0.75 and 0.83 respectively. Thus in the fast growing nrales rvl 'r ich i iave a higherasymptot ic length, the '1m/ l - ' ra t io is lower than in fenra les.

Fecundity: Figure 1l represents the relationship between length and nuurbcr of ova wl'ri leFigure 12 represents the relationship between weight and number of ova in Angelfish. Theresults show that the n.rost fecund stace of the fish are in which thc standard lengtl-r is betrveen

10070

59

-a

al

z

Standard t -ength (crn. )

Figurc I l. Angel.fish: Scatter diagram showing the relation of./ecundity to stlndarLl lengt lt in 30 femolc fishes.

5.0 and 5.-5 cm. and in which the weight is between 6.0 an<i 10.0 gm. Stat is t ica l analys isindicates that there is sotne posi t ive corre lat ion between length and nunrbcr of ova. However.this is not significant at the 5% level (r = 0.1662).

Feeding Habits of Angelfish in Pond: The gut contents of 40 fishes were analysed. The resultsindicate that this fish is ontnivorous in habit. However, they prefer l ive fbod as evident by thepreponderance of this diet in the guts. Its food includes ostracods, copepods, claclocera,hydracarina, chironomid larvae, larvae and adult of insects, desnrids, cliatoms, unicellular andfilanrentous algae. The monthly application of 150 gm. of PzO. to the pond indicates that thisis sufficient to culture anrple food for the fish as shown by the fullness of guts in thespecimens exanrined.

ACKNOWLEDGEMENTS

The author wishes to acknowledge the Director, Head of the Livestock Research Divisionand Head of the Freshwater Fisheries Research Station (MARDI) for their support in thispro ject . Technical ass is tance - { iven by Inc ik L inr Teck J in. Cik I - .non b. Sanracl is grate l i r l lyacknowledged

6 0

-o

'o

-

Z

Weight (grr . )

Figtre 12. AngelJish: Scatter diagrant showing the relation of Jbcun-ditl' to v'eight in 30 .f'ernale .fishes.

SUMMARY

Thc g ro r v th and r l a t u ra t i on o f t hc gonads o f Ango l f i sh i n a 0 .01 ac r c ( 0 .004 hec ta r c )

pond has bccn s tud ieC . Thc - r cnc r l l r no rpho lo l r o f t hc ova r l ' and t cs t i s has bcen dcsc r i bcd . The

ooc ) , t c s u , c r c a rb i t r a r i l y d i v i t l cd i n t o t ' ou r s t ugcs : Ooc ) ' t c I . Ooc ) t e I l . Ooc l ' t c I I I and Ooc l t e

lV. In thc tcst is . thc fo l lo$ ' inS gcrnr cc l ls c ln bc recosnizcd: pr i t tLrr l gcrnl cc l l . sper l l la lo-ronia,

l rature whcn their s tandrrd l tngt l . r is :1 . -5 cnr. and r lhen thel ,are 130 dal 's o ld. Al l f ishcs bt 'corne

n ta tu r c r vhen t hc i r s t and l r c l l cng th i s 4 . - 5 cn r . : r nd nhcn t hc ) ' a r c 130 da l s o l d . A l l f i sh bcco tnc

r l r a tu re a t 5 .18 c rn . i n s t r nda id l cn r t h r nd r vhcn t hc l a r c 160 days o l d . Thc eggs t t nde rso

rcgrcssion and thc s l )c i l t rs L l l td! ' rgo phauocytosis in thr : gonads of adul t unspa\\ 'ncd f ish. ( l rorvt l t

r a t c was rap id i n t hc ca r l l ' s t agcs o f t hc l ' i s l i l i f c c yc l c . Thc l ' i sh i s an o tnn i vo re . H ighc r

lccundi ty rvcrc obscrvcd in f ish ol 5.0 to 5.5 crn. in standard lcngth.

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6 l

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NIroLsxv, G.V. , 1963. The Ecology of F ishes. Academic Press, N.Y. , 352 p.

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Slvtt ' t, D.R.. 1955. Seasonal variation in the growth rate, thyroid gland activity and foodreserved of brown rrout, Salrtto trlttta. J. Expl. Biol., 32:151 164.

l).!.