Hypothalamus of Lates calcarifer (Family : Centropomidae) consists mainly

of nucleus preopticus (NPO), nucleus lateralis tuberis (NLT) and their axonal

tracts. NPO is a paired structure situated on either side of the third ventricle

slightly above the optic chiasma. It is a highly vascularised structure and

cytoarchitecturally divisible into dorsal pars magnocellularis (PMC) comprising

larger neurons and ventral pars parvocellularis (PPC) with smaller

neurosecretory cells. In the hypothalamus the NLT cells were found distributed

uniformly in the infundibular floor adjacent to the pituitary stalk. Prominent

phloxine-positive neurosecretory material (NSM) was encountered in PPC of

matured female. Though neurosecretory cells of both NPO and NLT were

positive to aldehyde fuchsin (AF), acid and chrome-alum-hematoxylin-phloxine

(CAHP), cellular differentiation was more marked in the latter. Both NPO and

NLT contributed beaded axons to form the neurohypophysial tract. Herring

bodies (HB) of varying sizes were encountered in the anterior neurohypophysis

(ANH). Neurosecretory cells of both NPO and NLT exhibited fluctuations in

their secretory activity in response to the gonadal maturation

Lal, Kuldeep Kumar

Pandey, A K

CMFRI Digital Repository

Indian J. Fish., 45(1) : 51-60, Jan.-Mar., 1998 Hypothalamo-neurosecretory system of the female sea bass, Lates calcarifer (Bloch), with special reference to gonadal maturation KULDEEP, K. LAL ' AND AJAY, K. PANDEY ' Central Marine Fisheries Research Institute, Cochin - 682 014, India ABSTRACT Hypothalamus of Lates calcarifer (Family : Centropomidae) consists mainly of nucleus preopticus (NPO), nucleus lateralis tuberis (NLT) and their axonal tracts. NPO is a paired structure situated on either side of the third ventricle slightly above the optic chiasma. It is a highly vascularised structure and cytoarchitecturally divisible into dorsal pars magnocellularis (PMC) compris-ing larger neurons and ventral pars parvocellularis (PPC) with smaller neurosecretory cells. In the hypothalamus the NLT cells were found distributed uniformly in the infundibular floor adjacent to the pituitary stalk. Prominent phloxine-positive neurosecretory material (NSM) was encountered in PPC of matured female. Though neurosecretory cells of both NPO and NLT were positive to aldehyde fuchsin (AF), acid and chrome-alum-hematoxylin-phloxine (CAHP), cellular differentiation was more marked in the latter. Both NPO and NLT contributed beaded axons to form the neurohypophysial tract. Herring bodies (HB) of varying sizes were encountered in the anterior neurohypophysis (ANH). Neurosecretory cells of both NPO and NLT exhibited fluctuations in their secretory activity in response to the gonadal maturation. I n t r o d u c t i o n is distributed throughout the coastal , , I P 1 1 1 waters of India it does not contribute Lates calcarifer, popularly known as i . ^^i ^^  . i ^ i i i • u • J • i. u i J • i."i. i 1 much to the total iish landings except m sea bass is distributed in the tropical ^ . _ ,^ *! , \.., and the subtropical coastal waters of ^ ? " * f " / r ^ " f „ .1"°,"^ ? f the Indo-Pacific (Grey, 1987; Bensam ^hilka Lake and Hooghly-Matlah estu-and Nammalwar, 1991). It is a highly ^"^s (^^sim and James , 1987). The sea carnivorous fish belonging to family ^ass exhibits complex sexuality mvolv-Centropomidae. The demand to con- ^ g protandric hermaphroditism mak-sumers as an excellent tablefish coupled ing it an interesting specimen for with its fast growing and euryhaline academic studies too (Moore, 1979). nature, are considered as valuable at- Lates calcarifer is reported to breed tributes by the aquaculturists (James from mid-October till December along and Marichamy, 1987). Though the fish the Tuticorin coast (Lai, 1991). Present Address : ' National Bureau of Fish Genetics Resources, Post Box No. 19, Lucknow - 226 004, India. Kuldeep Lai & Ajay, K. Pandey 52 Hypothalamus is a strategic point in vetebrate brain where various neural stimuli converge. It comprises groups of neurosecretory cells which control the secretion of the pituitary tropic hor-mones by elaborating releasing (RH) and / or inhibiting (IH) hormones (Ball, 1981; Maksimovich, 1987). Hypotha-lamus also contains receptors specifi-cally sensitive to the hormones which in turn regulate its activity through feed-back mechanism (Maksimovich, 1987). Though there are increasing evidences that the hypophysial functions in fishes are also mediated by hypothalamic neurohormones the regulatory mecha-nisms are not properly defined (Peter et al., 1991). So far, the hypothalamus of sea bass is not described. An attempt has therefore, been made to record the hypothalamo-neurosecrtory centres of the female Lates calcarifer with special reference to the gonadal maturation. Material and methods Live specimens of the sea bass, Lates calcarifer (Bloch), were collected from the commercial catches caught in gill net and shore seine operations at Tuti-corin coast (Gulf of Mannar). The region experiences rainfall during October-November due to the northeast monsoon. Average monthly temperature ranges between 25 and 31°C. The shore is partly muddy and sandy. The area adjoining Tambraparani estuary and Korampallam are swampy, infringed with thick mangrove vegetation. Sea bass though distributed throughout this region, is more concentrated near Punnaikkayal. Female specimens (total length range 855-1050 mm; total weight range 8.0-11.0 kg) were collected during August 1988 to December 1988 out of which sixteen specimens with ripe ovaries were used for the study. The brains along with pituitary were surgically removed from the live fish and fixed immediately in aqueous Bouin's solu-tion. A small piece of ovary was also dissected out and fixed in Zenkers-acetic (for 7 hrs) and neutral buffered formalin .(for 24 hrs). After 24 hrs the tissues were thoroughly washed in running tap water dehydrated in as-cending series of alcohol, cleared in xylene and embedded in paraffin wax at 60°C. To maintain the original shape and avoid breakage of yolky oocytes, double embedding (with celloidin and paraffin ) of the ovary was done (Khoo, 1979). Serial sections were cut at 6-8 vi and stained in aldehyde fuchsin (AF), Mallory's triple and chrome-alum-hematoxylin-phloxine (CAHP) whereas ovarian sections were stained in hematoxylin-eosin (H & E). Standard gonad weight (GS), used as an index in place of gonosomatic index (GSI) (Davis, 1985) was calculated as : GS = GES x (GO/GEO): where GES is expected gonad weight at standard length, GEO expected gonad weight at observed length and GO observed gonad weight. Oocyte diameter was measured along its horizontal axis using ocular micrometer. Oocytes were measured at random till the count reached 100 cells. The data obtained was used to work out largest oocyte diameter. Results The salient features of ovaries of sea bass, Lates calcarifer corresponding to various stages of development are sum-marised in Table 1. Sea bass females with ovaries in recovering and maturing phases (Stage 2, 3) were observed during February. However, the female possessing vitellogenic oocyte (stage 4) Hypothalamo-neurosecretory system of female seabass 53 TABLE 1, Salient features of ovaries ofh. calcarifer (n = 311) corresponding to various stages of maturity Stage Macroscopic characteristics Histological characteristics Largest oocyte diameter (pm) Standard gonad weight Gs(g) Stage -1 (newly formed) Stage -2 (developing virgin/ recovering spent) Stage -3 (maturing) The ovaries are deep reddish in colour, recently derived from testes after sex mversion. The ovaries are thick walled, translucent, with pinkish-red hue. The ovaries increase in size, translucent and cream in Stage -4 (mature) colour The ovaries are markedly larger in size, with thinner wall. Yellow hue start appearing Ovigerous lamellae are packed with chromatin nucleolus and early 110 78.1041 perinucleolus stage oocytes with a few at late perinucleolus stage. Chromatin nucleolus stage 140 82.9406 oocytes present but perinucleolus stage oocytes dominate. Perinucleolus stage oocytes 160 - 270 168.1038 are present; oocytes entering gonadotropin dependent phase (cortical alveoli stage) predominate the population. Stage -5 (ripe) Stage -5A. (involuting) Stage -6 (spent) The ovaries are deep yellow. in colour, with thin walls. distended and occupying most of the body cavity The ovaries are deep red in colour, progressively decrease in size and have watery consistency. The ovaries are flaccid. reduced in size, with purple yellow colour. The wall becomes tough and wrinkled. Ovigerous lamellae are packed with yolky oocytes visible to the naked eye. Most of the oocytes are at early and late vitellogenic stages, forming the leading clutch, Previtellogenic stages also coexist with this clutch. The oocytes undergo final maturation, migration of germinal vesicle and break down, coalescence of oil droplets. Vitellogenic oocytes at various stages of atresia, often surrounded by blood vessels. Post ovulatory follicles; previtellogenic oocytes dominate along with a few residual yolky oocytes. 260 - 500 406.7025 450 - 700 628.7930 140 127.4911 started appearing only in July. The ripe females (stage 5) were seen in late September till December with peak in November. The spent fish (stage 6) were encountered in late October till early January. Hypothalamo-neurosecretory complex of Lates calcarifer consisted mainly of nucleus preopticus (NPO), nucleus lateralis tuberis (NLT) and their axonal tracts. NPO was a paried structure situ-ated on either side of the third ventricle nv, K I'finili'y 5 4 ' l - l ' i | M , , I . , 1 ) i . I in the size of neuronal cells was discern-ible from dorsal to ventral asfiect of NPO. Most of the PM:C and PPC n(3i:iro^ lies were bipolar. NPO neurosecretory ccslls (both PMC and PPC) of the females pos.'«3ssing viteflogenic oocytes (stage 4) stained readily during July-August owing" to the ciccurnuilation of iieuro.secretory mate-rial (NSIM) (Fig. 2, 3). However, during .spawning .season (October-November), the neurosecretory cells of ripe female I Stage 5) exhibited declined staining ,, • I f ' \ i • • I i 1111 '. I . ' , > ' . • .".'<'...'» • ; ( • I h l h l l O , , - I c ' i 1 1 r< | , ! i i i ,1 . ' . ( i ' l . i. i i ' 4 o 11,11 O i l ! . 55 I • I > , . 1 ' , • i . i ; 1 J . 1 • 1 1 , 1 ' ' • I . ' I I . ' I ( , | ' !•• ' . ' • , . , 1 | ! ' l ! i l , 1 i I- , 1 , I , ; • ! . i '• •• ' M - l l I I I , 1 , , i ( i , j j , | , , , I , 1 ' ^ ' ' • ' ' . • > . . . d , • lU .',. i n i M . ' -• ! • . i \ i \ - U . K . j . i . ( I I - I " 1 , I' <> ( • • ) ' - ' i I t . , - ! • I • i ' ' I , , i j i , , • ;.! . ; . , ; : , ! , . , ( ' - >: I i I ! . P i l l . I d ,1 J' f I , ; 1 ( 1 ' . > . i . - I 1 . . . . [ . , 1 ( i H i ' ' I ' >' .1 11 i . 1, , | * . ; ' , , I ! t , , I . ' ' • ' ' . ' i ' I .1 I ' i - i . i i i - I ' , , i , ! l , , . ; ' " r , 1 1 ' l ,( ,1 - r < , ! I I ' > , Kiilf'i;i-p Lai A' /1/«v, K. I'nndcy 56 M l , ' ' , , l l ) ,1 '! - . .-. „ ' . I , ' h ) . , i i ' ; . I I . , ' < | . < ) l ' / I J ' i ' ' , . ,1 i 1 1 1 U I I ' . ' S I • ' j . 1 I I ! , | i H . i J- I . ' ' I I ' f I • I i ! [ H , . ( , . ' 11 ] • ' • '! .. j ) M l l ( , I i , ,. i I , , f ., i h ' i 1 1 . 1 ' ' • ' ' I , M : f H • I / ,' , • ' t I i i . f , . . ( i , , ! ' I ' • , > : • •. '. I ; i 1 1 I I ' I ; < , i , ' ; I . I • ' i , • > , - ' I I ' I ' ' I ; I . ' I i l J ^ I ' U ' ,i m I ! . I , , i . '•< , ( • i ( . f i . 1 • i ! , , j ,1 i i ' i l l ' , / . . , I I , ! I i • !• / . , ' , . . , ( • i l - ' . ; • ' ! ' ' ' ^ I . ' ' I , I ' ! i , , , , l • ' '• 11 . 1 • : 1 ) ! ' , ; . ' I ' I , II ' ! , ; > • - ! , ; M I I 1 , , ! 1 • i ' , ; ,1 I ' i . I , I ' .- . .. , l i ,1 . I , i l . , i .1 !. , , 1 . . 1 - ,, I ' ' ! I i i )"( ,S ' , I . . I I . ' . . I . l i 1, , h i " -111',' i i i i f i , . ( , j h h ! • l i h r , , • ' . >.•!' i'. . i l l . i l l . . | . 11 1 . » : 11, J ,1 ! 1 . 1 ' ' 1 ! ( i . • I -i .1 . I • .••' . I ; . . ' . i i . i h i I .. h .,1 , . h , l i i i . • ! ! • . ( . . 1 1 1 . I . ( ( l l . M, • •; ' . . i . i i . j i I j . I ! , I I - I. > I I • h . / i . . i i , ' 1 ' . I I . . . . ! ! (I< {'.••,• . - . ' , . ,'. .'. 1 ' '• • '• l l ' . h ' l M l I I , • l l . 1 I'.f I l l " . ! ! ( ' ! ' . . . I , ' • ' ' , ••'II n I 1 I h I (111 I- ' I I ' . i l / l l ! i . h • ! • l i , • . . -i ) l , ( i I • I. ,1 •! " H I iH • ! ! . h ' l i i i i . ' i i ' h i i h I I . [ . l ( i ' 1 . I l l l l < "',', | . . • . • • ! | , 1 > , • I ' l l . , . u i - ! i i . I I , i i < »' i i n .-1 1 f I j : i . . . i i . i | . . I.I I .1' 1 h.- h. ,-•' I i - | . .1 .11 ! ; I, , 11 ! ! 111 • ' I I • 1 . . 1 ( l l •111 ( I . ! ; I. . i i i i r i | . f f , . ' - i j / . ' . / ' . I l l I / ' . i u i "111 I I , I'' ' I 1 . • • .' I I , h i , - 1  ' , l . i l I I I . I . I I h >| i f ' I , II t . I S. ,,:, . . i , 1 I . ' ' , I 11 ; , , i I , 1 I • t 1 I ' I 1' ( . l l . l i ,. ..1 I I , . . I l l I ..,1 , 1 11 j i i , i . | i ' 1 I , ,11 <i; M l . . , ; . . h 111 1, , . , , . . ' . ' , ' I , l l ! I l l 1,1 ..1,11 . . l l I . 11, h. ! . , h . I I „ M ' l ' Kuldeep Lai & Ajay, K. Pandey 58 Prakash et al., 1984; Maksimovich, 1987; Pandey, 1993; Pandey and Mohamed, 1993). Similar structure was noticed in the NPO (PPC) of matured female Lates calcarifer also (Fig. 6). Nucleus lateralis tuberis (NLT) has been reported to be the second neurosecretory centre in the teleostean hypothalamus, however, there exist stray reports of its absence among a few species (Kobayashi et al., 1959; Maksimovich, 1987). Since this struc-ture has been implicated to play a major role in the gonadal maturation of teleosts, it is unlikely that the same might be completely absent in some species (Maksimovich, 1987). Kobayashi et al. (1959) have also remarked that season or age factors may be responsible for the absence of stainable granules in the NLT. The neurosecretory cells of NLT pars anterior (Fig. 9), pars poste-rior (Fig. 10) and pars inferior (Fig. 7) of Lates calcarifer are readily stainable with acid fuchsin and CAHP. Fluctua-tions in the secretory activity of pars anterior (Fig. 9) and pars posterior (Fig. 10) with ovarian development suggest their involvement in the maturation of the sea bass. Clarias batrachus, Tor tor, Heteropneustes fossilis, Colisa fasciatus and Decapterus tabl also exhibited en-hanced secretory activity in NLT neurosecretory cells during spawning phase of reproductive cycle and/or sex steroid administration (Viswanathan and Sundararaj, 1974; Rai and Pandey, 1986; Maksimovich, 1987; Pandey and Mohamed, 1993). We found colloid-like neurosecretory material (NSM) in NLT pars anterior and pars posterior of Lates calcarifer at stage 4 and 5 of maturity. Such structures have also been recorded in NLT pars posterior of matured Decapterus tabl (Pandey and Mohamed, 1993). Zolotnitskiy (1980) also noticed similar structures in the form of differ-ent-sized drops in lateral nucleus of the Black sea turbot, Scophthalamus maeoticus. Herring bodies (HB) of varying sizes were seen in the anterior neuro-hjT)ophysis (ANH) of the ripe female Lates calcarifer (Fig. 13, 14). A similar distribution of herring bodies have also been observed in Porichthys notatus, Clarias batrachus, Phoxinus phoxinus, Glossogobius giuris, Scophthalamus maeoticus, Rastrelliger kanagurta and Decapterus tabl (Zolotnitskiy, 1980; Pandey, 1993; Pandey and Mohamed, 1993). It is assumed that HB have accumulated neurosecretory material (NSM) which help to increase the surface area for the release of biologi-cally active principles in the blood circulation (Zolotnitskiy, 1980; Maksimovich, 1987; Pandey and Mohamed, 1993). Acknowledgments The authors are grateful to Dr. P.S.B.R. James, Ex-Director, C.M.F.R.I., Cochin for his encouragement and inspi-ration. We greatly appreciate the co-operation rendered by Shri S. Maha-devan, the then Officer-in-Charge, and the other staff of Tuticorin Research Centre of CMFRI for the help extended during the procurement of live sea bass. Help by Prof. A.G. Sathyanesan, Prof. R.E. Peter, Dr. A. Noble and Ms. Rosahe N. Shaffer is acknowledged. Reference Ball, J.N. 1981. Hypothalamic control of pars distalis in fishes, amphibians and reptiles. Gen. Comp. Endocrinol., 44 : 135-170. Bensam, P. and P. Nammalwar 1991. Seed production and commercial culture of Hypothalamo-neurosecretory system of female seabars 59 sea bass, Lates calcarifer (Bloch) at Singapore and its lesson for India. Mar. Fish. Infor. Serv., T & E Ser., No. 109, p. 5-11. Das, R.C. and Y.K.P. Sinha 1988. Histo-morphology of the neurosecretory regulation of ovarian maturation in the teleost, Labeo bata (Hamilton). Vetern. Archiv, 58 : 11-21. Davis, T.L.O. 1985. Seasonal changes in gonad maturity and abundance of larvae and early juveniles of barra-mundi, Lates calcarifer (Bloch) in Van Dieman Gulf and the Gulf of Carpentaria. Aust. J. Mar. Freshwat. Res., 36 : 177-190. Grey, D.L. 1987. An overview of Lates calcarifer in Australia and Asia. In: Management of Wild and Cultured Sea Bass / Barramundi (Lates calcarifer). J.W. Copland and D.L. Grey (Eds.), p. 15-21, ACIAR, Dar-win, N.T., Australia. James, P.S.B.R. and R. Marichamy 1987. Status of sea bass (Lates calcarifer) culture in India. In: Management of Wild and Cultured Sea Bass I Barramundi (Lates calcarifer). J.W. Copland and D.L. Grey (Eds.), p. 74-79, ACIAR, Darwin, N.T., Australia. Kasim, H.M. and P.S.B.R. James 1987. Distribution and fishery of Lates calcarifer in India. In: Management of Wild and Cultured Sea Bass/ Barramundi (Lates calcarifer), J.W. Copland, and D.L. Grey (Eds.), p. 109-114 ACIAR, Darwin, N.T. Australia. Khoo, K.H. 1979. The histochemistry and endocrine control of vitellogenesis in goldfish ovaries. Can. J. Zool., 57 : 617-626. Kobayashi, H., S. Ishii and A. Gorbman 1959. The hypothalamic-neurosecre-tory apparatus and the pituitary gland of a teleost, Lepidogobius lepidus. Gumma J. Med. Sci., 8 : 301-321. Lai, K.K.1991. Studies on the reproductive physiology of Lates calcarifer (Bloch). Ph.D.Thesis, Cochin University of Science & Technology, Cochin, India. Maksimovich, A. A. 1987. Neurosecretory hypothalamo-hypophysial system of teleostean fish. J. Ichthyol., 27(4) : 92-106. Moore, R. 1979. Natural sex inversion in the giant perch (Lates calcarifer). Aust. J. Mar. Freshwat. Res., 30 : 803-813. P a n d e y , A.K. 1993. H y p o t h a l a m o -neurosecretory system of the Indian mackerel, Rastrelliger kanagurta Cuvier. Nat. Acad.Sci. Lett.., 16 : 265-268. Pandey, A.K. and M.P. Mohamed 1993. Histomorphology of the hypothalamo-neurosecretory system of the Indian scad, Decapterus tabl (Berry, 1968) In : Proceedings of Third Indian Fisheries Forum. M. Mohan Joseph (Ed.), p. 131-134, College of Fisheries, Mangalore. Peter, R.E., V.L. Trudeau and B.D. Sloley 1991. Brain regulation of reproduc-tion in teleosts. Bull. Inst. Zool., Acad. Sinica (Monogr.), 16 : 89-118. Prakash, M.M., S.S. Shrivastava and D.K. Belsare 1984. Correlative cyclical changes in the hypothalamo-hypo-physial-gonad system in Notopterus chitala (Ham.) Z. mikrosk.-anat. Forsch., 98 : 225-240. Rai, S.C. and K. Pandey 1986. Correlative seasonal changes in the hypothalamic nuclei, adenohypophysial cells and gonads of tropical perch, Colisa faciata (Bl. & Sch.). Bull. Inst. Zool, Acad. Sinica, 25 : 57-66. Sokolowska, M. P. Epler and K. Bieniarg 1978. The histological picture of the hypothalamus (nucleus preopticus) Kuldeep Lai & Ajay K. Pandey 60 and hypophysis in male Anguilla anguilla L. treated with hormones. J. Fish Biol, 12 : 1-4. Thomas, P.C. and A.G. Sathyanesan 1982. Hypothalamo-hypophysial neuro-secretory system of the Indian mud eel, Amphipnous cuchia (Ham.) with a note on the regenera-tion of the pituitary stalk after hy-pophy - sectomy. J. Hirnforsch., 23 : 671-679. Viswanathan, N. and B.I. Sundararaj 1974. Seasonal changes in the hypothalamo-hypophysial-ovarian system in the catfish, Heteropneustes fossilis (Bloch). J. 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Hypothalamo-neurosecretory system of the female

sea bass, Lates calcarifer (Bloch), with special

reference to gonadal maturation

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Hypothalamo-neurosecretory system of the female sea bass, Lates calcarifer (Bloch), with special reference to gonadal maturation

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