We describe organogenesis at a histological level in American shad( Alosa sapidissima) larvae from 0 until 45 days after hatching(DAH). Larval development was divided into four stages based on the feeding mode,externa...We describe organogenesis at a histological level in American shad( Alosa sapidissima) larvae from 0 until 45 days after hatching(DAH). Larval development was divided into four stages based on the feeding mode,external morphological features,and structural changes in the organs: stage 1(0–2 DAH),stage 2(3–5 DAH),stage 3(6–26 DAH) and stage 4(27–45 DAH). At early stage 2(3 DAH),American shad larvae developed the initial digestive and absorptive tissues,including the mouth and anal opening,buccopharyngeal cavity,oesophagus,incipient stomach,anterior and posterior intestine,differentiated hepatocytes,and exocrine pancreas. The digestive and absorptive capacity developed further in stages 2 to 3,at which time the pharyngeal teeth,taste buds,gut mucosa folds,differentiated stomach,and gastric glands could be observed. Four defined compartments were discernible in the heart at 4 DAH. From 3 to 13 DAH,the excretory systems started to develop,accompanied by urinary bladder opening,the appearance and development of primordial pronephros,and the proliferation and convolution of renal tubules. Primordial gills were detected at 2 DAH,the pseudobranch was visible at 6 DAH,and the filaments and lamellae proliferated rapidly during stage 3. The primordial swim bladder was first observed at 2 DAH and started to inflate at 9 DAH; from then on,it expanded constantly. The spleen was first observed at 8 DAH and the thymus was evident at 12 DAH. From stage 4 onwards,most organs essentially manifested an increase in size,number,and complexity of tissue structure.展开更多
Plant organs are derived from stem cells.Once a leaf primordium initiates growth from the shoot apical meristem（SAM）,it establishes adaxial-abaxial（dorsal-ventral）polarity.This polarity essentially allows the leaf...Plant organs are derived from stem cells.Once a leaf primordium initiates growth from the shoot apical meristem（SAM）,it establishes adaxial-abaxial（dorsal-ventral）polarity.This polarity essentially allows the leaf to become a flat structure with the lamina expanding along the juxtaposition,i.e.,the middle domain,between the adaxial and abaxial domains.展开更多
基金Supported by the National Spark Program of China(No.2012GA690001)
文摘We describe organogenesis at a histological level in American shad( Alosa sapidissima) larvae from 0 until 45 days after hatching(DAH). Larval development was divided into four stages based on the feeding mode,external morphological features,and structural changes in the organs: stage 1(0–2 DAH),stage 2(3–5 DAH),stage 3(6–26 DAH) and stage 4(27–45 DAH). At early stage 2(3 DAH),American shad larvae developed the initial digestive and absorptive tissues,including the mouth and anal opening,buccopharyngeal cavity,oesophagus,incipient stomach,anterior and posterior intestine,differentiated hepatocytes,and exocrine pancreas. The digestive and absorptive capacity developed further in stages 2 to 3,at which time the pharyngeal teeth,taste buds,gut mucosa folds,differentiated stomach,and gastric glands could be observed. Four defined compartments were discernible in the heart at 4 DAH. From 3 to 13 DAH,the excretory systems started to develop,accompanied by urinary bladder opening,the appearance and development of primordial pronephros,and the proliferation and convolution of renal tubules. Primordial gills were detected at 2 DAH,the pseudobranch was visible at 6 DAH,and the filaments and lamellae proliferated rapidly during stage 3. The primordial swim bladder was first observed at 2 DAH and started to inflate at 9 DAH; from then on,it expanded constantly. The spleen was first observed at 8 DAH and the thymus was evident at 12 DAH. From stage 4 onwards,most organs essentially manifested an increase in size,number,and complexity of tissue structure.
文摘Plant organs are derived from stem cells.Once a leaf primordium initiates growth from the shoot apical meristem（SAM）,it establishes adaxial-abaxial（dorsal-ventral）polarity.This polarity essentially allows the leaf to become a flat structure with the lamina expanding along the juxtaposition,i.e.,the middle domain,between the adaxial and abaxial domains.
