Proc. Indian Acad. Sci., Vol. 85 B, No. 5, 1977, pp. 351-363. The development of the ehondroeranium of Cyprinus carpio Linn. R. G. PASHINE AND V. B. MARATHE Department of Zoology, Institute of Science, Nagpur440001 MS received 29 April 1975; in revised form 20 September 1976 ABSTRACT The common carp, Cyprinuscarpio Lian. has been studied for the deve- lopment of the chondrocranium. A large number of early developmental stages of the embryos were fixed at regular intervals of time. The develop- meat of the cartilage has been traced from the serial sections which were cut at 10 micra. These sections were stained with Delafield's haematoxylin and eosin. Waxo model and graphic reconstructions were prepared. For some stages, bulk stained preparations were also made. Eleven stages have been investigated and described. 1. INTRODUCTION NUSBAUM (quoted by De Beer 1) has studied the development of the skull of the carp, Cyprinus carpio, only so far as the Weberian ossicles al'e con- cerned. What little knowledge exists is, therefore, practically restricted to the posterior region. A perusal of the literature reveals very little information concening the structure and development of the chondrocranium of the common carp, Cyprinus carpio Linn., belonging to the family Cyprinidae. In order to fill up this lacuna, the development of the chondrocranium of this food fish has been studied. 2. MATERIALAND METHODS A larger number of fertihzed eggs of Cyprinus carpio were collected from a local fish farm. The fertilized eggs were reared in the laboratory and a large number of stages were fixed at regular inte,vals of time. The fixatives used were 70% alcohol, 5% formalin, picro-formal and acetic-alcohoL The serial sections of the alevins were cut at 10 micra and were stained with Delafield's haematoxylin and eosin. The stages in which the bones had already developed, were decalcified and the bulk stained preparations were made by van Wijhe's technique) Wax model and graphic reconstructions were prepared in several cases. 351 B12--May 77 352 R.G. PASHINE AND V. B. MARATHE 3. OBSERVATIONS STAGE 1: TOTAL LENGTH--3.73 MM (60 HR) (figure 1) The foundation of the cartilaginous skull has been laid down in the form of a pair of independent procartilages, the trabeculae (tc), measuring about 60-70 microns in length. The notochord (n) is well represented. STAGE 2: TOTAL LENGTH--4.28 MM (66 HR) (figure 2) The trabeculae (tc) are cartilaginous and have increased in size extending upto about 90-100 microns in length. The parachordals (pc) are noticed as procartilages. STAGE 3: TOTAL LENGTH----4"4 MM (69 HR) (figures 3 and 4) The trabeculae (tc) extend.further in the ethmoid region and anteriorly they join to form a small ethmoid plate (ep), extending for over 30 microns. The trabeculae and the parachordals together enclose a hypophysial fenestra (hf) which extends to over 300 microns. The occipital arches (oa) have appeared and extend to over 20 to 30 microns. The capsular cartilages (ac) are laid down in the anterior part of the auditoiy sac (as). The notochord (n) extends for about 100 microns into the hypophysial fenestra (hf). Meckel's cartilage (me), quadrate (qu), hyosymplectic (hs), ceratohyal (ch) and the first two branchial arches (ba 1-2) have appeared. STAGE 4: TOTAL LENGTH---4.52 UU (72 nR) (figure 5) The anterior end of the auditory capsule (ac) is better chondritied. An anterior basicapsular commissure (abc), connecting the anterior part of the auditory capsule to the anterolateral border of the pa:tachordal has appeared. The hyosymplectic articulates with the anterolateral side of the auditory capsule. STAGE 5: TOTAL LENGTR--4"7 MM (81 I-IR) (figures 6 and 7) The ethmoid plate (ep) is slightly better represented. The palachordals (pc) extend behind to join the occipital arch elements. The quadrate (qu) has increased in size. The hyosymplectic (hs) is well formed and extends underneath the posterior part of the quadrate. The third and fourth bran- chial arches (ba-3 and ba-4) have appeared. The fifth inch (ba-5) is in proeartilaginous stage. STAGE 6: TOTAL LENGTH--5"0 MM (90 rig) (figures 8 to 10) The parachordals (pc) have broadened at the posterior end. The lateral wall of the auditory capsule (rac) is appearing. Meckel's cartilage (mc), CHONDROCRANIUM OF Cyprinus carpio INN. 353 -(15 E P ~ep "k'nC /~r., -~ ctbe ctbc ~ -. pc pc ...pc ,:." .~btt-s 1-1/ ep~ ~ 'h t% , f raC ( b~c '3u" ch bb-i s sh__.b,~ ~ I ? " (1.C pc pc E z.._g oa -rl I o.3 mrn.J bg.8 Figure~ 1-10. 1. Dorsal view of the chondrocranium of Cyprinus carpio, stage 1 (3.73 ram). 2. Dorsal view of the chondrocranium of stage 2 (4.28 ram). 3. Dorsal view of the chondrocranium of stage 3 (4" 4 ram). 4. Dorsal view of the visceral arches of stage 3. 5. Dorsal view of the chondrocranium of stage 4 (4.52mm). 6. Dorsal view of the chondrocranium of stage 5 (4" 7 man). 7. Dorsal view of the visceral arches of stage 5. 8. Dorsal view of the chondrocranium of stage 6 (5.0ram). 9. Dorsal view of the mandi- bular arches of stage 6. I0. Dorsal view of the hyoid arch and five branchial arches of stage 6. (Explanations for the abbreviations in figures are given in p. 363 ) 354 R.G. PASHINE AND V. B. MARATHE quadrate (qu) and hyosymplectic cartilage (hs) are better represented A small basihyal (bh) is noticed and it measures about 60 miclons in length• The head of the basihyal is broad. A small cartilaginous stylohyal (sh) appears between the ceratohyal and the hyosymplectic cartilage. All the five branchial arches (ba 1-5) are distinct. Thee is a cartilaginous first basi- branchial (bb-1), supporting the first and the second pair of branchial arches. STAGE 7: TOTAL LENGTH--5"4 MM (102 Ha) (figures 11 to 13) The ethmoid plate (ep) has increased in size and is continued behind as the trabecula communis (tcom). In front of the anterior basicapsular commis- sure (abe) a thin, lateral commissure (lcm) is formed. Between these two commissures, is noticed a trigemino-facialis chamber (tfc) through which ..: ep hb-1 bh ch ~com mc r'}P 'i 2: '. ~¢ c~ ~ du,~ ~, bvc ~ i ....--~,_~,-ep mcu . bh co ::"~ 1.cm +,+ hb-+ ~ cb-1 bp ifi/:::: i, to.3 mm! 18 Figures 11-16. 11. Dorsal view of the chondrocranlurn of C. carpio, stage 7 (5"4 ram). 12. Dorsal view of the mandibular arch of stage 7. 13. Dorsal view of the hyoid and branchial arches of stage 7. 14. Dorsal view of the chondrocranium of stage 8 (6.0ram). 1~, Dors~ view of the mandibular arch of stage 8. 16. Dorsal view of the hyoid and branchial arches of stage 8. (Explanations for abbreviations in figures are giver in p. 363) CHONDROCRANIUM OF Cyprinus carpio LINN. 355 pass the V and VII cranial nerves. Posteriorly a small basivestibular commis- sure (bye) is noticed, which is not yet connected with the auditory capsule. The orbital cartilages (ore) have appeared as small cartilaginous rods, located between the trabecula communis and the auditoly capsules. A pterygoid process (,ptp) of the pterygo-quadrate bar is formed. The basihyal (bh) supports two broad ceratohyals (eh). The first two pairs of hypobranchials (hb 1-2) are noticed. A small independent cartilaginous second basibranchial (bb-2) is formed. It supports the third and fourth branchial arches. STAGE 8: TOTAL LENGTH--6"0 MM (129 HR) (figmes 14 to 16) The ethmoid plate (ep) has further increased in size and it is broad in the middle. The parachordals (pc) form the basal plate (bp). Each orbital cartilage (orO extends behind to join the auditory capsule (ac). The side wall of the capsule (rac) is slightly better formed. The original large basi- capsular fenestra (bcf) is invaded by cartilage and is restricted to about 80 microns in length. The basivestibular commissure (bvc) is complete. The metotic foramen (free), is formed which serves for the exit of IX and X cranial nerves. Meckel's cartilages (mc) fuse anteriorly to form a symphysis (mcu). Meckel's cartilage articulates with the pterygoquadrate cartilage. The basihyal and the first and second basibranchials have fused to form a common copula (cop). The first four branchial arches are represented by paired hypobranchials (hb 1-4) and ceratobranchials (cb 1-4). The first two epibranchials are noticed in the form of procartilages. STAGE 9: TOTAL LENGTH--6"8 MM (195 HR) (figures 17 to I9) Anteriorly the ethmoid plate (ep) shows a distinct notch. The trabecula communis (tcom) is thin and plate-like. Lamina orbitonasales (lon) develop as small upgrowths from the postero-lateral sides of the ethmoid plate. Epiphysial cartilage (epb) is being formed. Its middle part is still pro- cartilaginous. The floor of the auditory capsule (ac) is thickened. Meckel's cartilages (mc) posteriorly show a small retroarticular process (ra). The pterygoid process (ptp) has increased in size and is attached ante- riorly to the ethmoid plate by connective tissue. The hypohyals (hh) are differentiated from the ceratohyals (ch). The common copula noticed in the previous stage breaks up into two copulae. The first copula (cop-l) supports the hypohyals (hh) and the first three pairs of hypobranchials (hb 1-3). The second copula (cop -2) supports the third and fourth pair of hypo- branchials (hb 3-4) and the fifth branchial arch (ha-5). The first four epi- branchia.Is (ep 1-4) have appeared as small rod-like cartilages, which are connected with their respective ceratobranchials.