Table 1.
Comparison between stable carbon isotope analysis and conventional approaches applied in studying the development of Cordyceps sinensis.
| Stages | Caterpillar-shaped sclerotium formation | Stiff worm | Stroma sprout | |
|---|---|---|---|---|
| Duration for different stages40 | Around 2 months | About 3–5 days | 3–4 months | Around 2 months |
| Stable carbon isotope analysis (δ13C values of subsamples*) | H1 to H2: highest value, initial infection | A3 to Ai: slightly declined | H1 to S1: sharply jumped down | S1-Si: continuously decreased |
| H2 to T3: slightly declined, inception | ||||
| T3 to A3: sharply decreased, incubation | ||||
| Field observation in morphology | Could not be observed due to no symptom)40 | The larva started to behave abnormally, and its skin colour gradually changed31,40. | Relatively long dormant period40,43 (“Winter-worm”) | The stroma started to germinate at the head for more than 2 months and eventually formed the mature stroma31,41,43 (“Summer grass”). |
| Macroscopic observation in the growth of mycelia | The inside became hollow and the integument became moist. Then, a white hyphal coil firstly developed at the pharynx and gradually extended to the whole body42. | The stiff worm was gradually coated by mycelia31. | 1st: The stroma kept growth for one month to reach the length of around 3 cm. Then, its apex swelled and covered with the granulated perithecium. | |
| 2nd: The stroma continued to grow for 20 days to reach the final length of about 4.5 cm. | ||||
| 3rd: In the coming 10 days, the stroma would underwent the development period of ascospores, including growth, maturation, and eruption31,41. | ||||
| Microscopic observation in the growth of mycelia | 1st: The infectious fungus firstly invaded the host and formed several spheroid hyphal bodies. | The inner of a stroma was made up of interwoven mycelia, and finally multiseptate and elongate fusoid ascospores were produced31. | ||
| 2nd: The hyphal bodies multiplied in the host and gradually formed multinucleate hyphal bodies. | ||||
| 3rd: The multinucleate hyphal bodies further developed into mycelia through the following processes: budding multiplication, conglobation and connection, and hyphal body fusion. The mycelia continued to grow and completely filled the host body cavity15,16,31,41. | ||||
*S1 to Si, H1 to H2, T1 to T3, and A1 to Ai are the subsamples from the stroma, head, thorax, and abdomen according to their positions, respectively. The italic lower case letter i represents the section numbers of the stroma and abdomen, respectively.