Morphometric study of a field population of the terrestrial planarian Artioposthia triangulata (dendy) in the Faroe islands

This study of A. triangulata at a horticultural site in the Faroes highlights considerable variation in the size of individuals within a field population. Flatworms sampled ranged from juveniles weighing 5.0 mg fwt to mature adults weighing 1536.6 mg fwt. Egg capsules ranged from 15.7 mg fwt to 428.0 mg fwt, with a mean of 147.9 mg fwt. A positive relationship between post-deposition adult weight and egg capsule weight was apparent. Egg capsule weight ranged from 5.1% to 21.9 % of the post-deposition weight of adults. Observation of newly hatched individuals revealed a minimum of 1 and a maximum of 14 hatchlings per egg capsule, the mean being 6.3. Hatchlings ranged in size from 0.5 mg fwt to 25.2 mg fwt, with a mean of 6.7 mg fwt. No clear relationship was apparent between pre-hatching egg capsule weight and total weight of hatchlings or total number of hatchlings. Total hatchling weight varied from as little as 5 % to 44 % of the original egg capsule weight. A negative correlation between the mean weight and number of hatchlings per egg capsule was evident. 'Dwarf' hatchlings were associated with egg capsules from which many individuals emerged, whereas 'giant' hatchlings were associated with few siblings. The results are considered in relation to reproductive biology and the colonisation process.