M. R. Morone De Lucia

POSTEMBRYONIC DEVELOPMENT IN HETEROTARDIGRADES

SUMMARY Cuticular structures were examined in specimens of numerous natural populations of heterotardigrades. Comparison of original and bibliographic data leads to the conclusion that heterotardigrades undergo indirect development. An exception being made for certain specific cases, both Arthrotardigrada (all marine) and Echiniscoidea (marine and nonmarine) are characterized by two larval stages. The first larval stage lacks anus and gonopore and has on each leg two digits or claws less than the adult. The second larval stage has an anus and the same number of digits or claws as the adult but lacks the gonopore (exceptionally it is rudimental). Species-specific modification or appearance of cuticular structures may be found during development. The presence of indirect development represents a further distinguishing character between heterotardigrades and eutardigrades.