Vol. 40 No. 1, 2001

Statistical Distinction between Normal and Amputated Specimens in a Field-Collected Sample of the Earthworm, Amynthas lautus (Ude)

Chu-Fa Tsai^1,* and Su-Chen Tsai¹

¹Habitat and Ecosystem Division, Taiwan Endemic Species Research Institute, Chichi, Nantou, Taiwan 552

Chu-Fa Tsai and Su-Chen Tsai (2001) The interac- tive outlier rejection procedure, which repeatedly performs a linear regression analysis between total length and segment length with the outlier rejection at the 95% confidence limits, is apparently a useful statistical method in distinguishing tail-amputated specimens (outliers) and normal specimens (within the confidence interval) in field- collected samples of the pheretimoid earthworm, Amynthas lautus. After removing amputated specimens, there was an asymptotic relationship between segment number and total length of normal specimens; segment num- ber increased with total length and reached a plateau in aclitellate worms and remained at the plateau in clitellate worms. Left skewness of the segment-frequency distribution of the field-collected sample indicated the pres- ence of tail-amputated specimens in clitellate worms, but the presence of both tail amputation and growth effect in aclitellate worms.

Key words: Oligochaeta, Length, Segment number.

*Correspondence: Tel: 886-49-2761331 ext. 215.    Fax: 886-49-2764600 or 2761582.