Skeleton development observation of Lates calcarifer larva fish

ObjectiveSkeleton development law of Lates calcarifer at larva stage was revealed to provide basic re-ference for relevant genetic research on skeleton development of L.calcarifer and exploration of fish fossils.MethodThe formation and development characteristics of pectoral fin,dorsal fin,ventral fin,caudal fin and anal fin in the spine and appendicular skeleton of L.calcarifer larva fish0-23 day post hatching(DPH)were continuously observed using carti-lage-bone double staining technique during development process.ResultThe results showed that the 1 DPH larva fish was 1.70±0.10 mm long and the body was slender and straight;ossification did not start and appendicular skeleton did not appear.The spine of 3 DPH L.calcarifer larva fish bent naturally and started to develop,and the pectoral fins and primor-dium of caudal fins gradually formed.The end of notochord began to warp upward and the dorsal fins began to develop on 5 DPH.On 9 DPH,the notochord of L.calcarifer larva fish was bent,and neural arch and haemal arch began to form;urostyle upturned then caudal fins formed,the primordium of pectoral fins and dorsal fins wrinkles appeared,and anal fin started to develop.On 13 DPH,the development of pectoral fins and caudal fins in L.calcarifer larva fish almost comple-ted,and neural spines and haemal spines appeared.On 15 DPH,the ventral fins of L.calcarifer larva fish began to deve-lop and the dorsal and ventral ribs grew in the form of cartilage,and urostyle contracted;the development of dorsal fins and pectoral fins entered late development stage.On 19 DPH,ossification occurred in spine,and fins spine appeared in pectoral fins,the development of appendicular skeleton was to be completed.On 21 DPH,ossification happened in dorsal ribs and ventral ribs and the ossification of caudal fins almost completed;neural arch,haemal arch,neural spine and hae-mal spine were ossified.On 23 DPH,the ossification of spine,the development of pectora fins and the basic framework of fish skeleton fully completed;fin rays was ossified and branch pterygiophores appeared,and the metamorphosis of L. calcarifer larva fish completed.Spinal deformity first appeared in 10 DPH L.calcarifer larva fish.By 22 DPH,the defor-mity rate accounted for 8% of the total collected samples,among which the early deformed larva fish was basically elimi-nated at the age of 14-15 DPH.ConclusionThe spine and appendicular skeleton of L. calcarifer larva fish are in the same developmental sequence as other fish species,but the development time node is different.The skeletal development deformity of L.calcarifer larva fish first appears at the age of 10 DPH,and mainly appears at the age of 20-22 DPH.