Zoology 10th Edition by Stephen Miller,John Harley

Exercise 9

Members of the phylum Nematomorpha are long and threadlike. They have separate sexes. Larvae are parasites in arthropods, and adults are freeliving in freshwater. Members of the phylum Kinorhyncha live in marine sediments. Their bodies are divided into zonites. Zonite 2 contains scalids and placids. The introvert is retractable. Kinorhynchs are dioecious and larvae molt into the adult form. Members of the phylum Priapulida have an introvert that is used in burrowing in marine sediments. Their cuticle bears spines and superficial annuli. Sexes are separate and gametes are shed into the sea. Members of the phylum Loricifera live in marine sediments. They possess a retractable introvert and are surrounded by a protective outer case called the lorica. Loriciferans are dioecious.
Adult nematomorphs are aquatic, but sometimes they are observed on sidewalks or lawns following a rain. How can you explain these observations?