Final answer:
Acorn worms have a trunk divided into a proboscis, collar, and trunk proper, with a closed circulatory system rather than the hemocoel of arthropods. The nervous system includes a dorsal nerve cord, differing from the arthropod's ventral nerve cord. Information provided is related to body systems in various invertebrates, demonstrating the diversity among animal phyla.
Step-by-step explanation:
The student's question asks about the different regions of the trunks of acorn worms, which is not fully related to the provided references. However, the provided information about the nervous system and the circulatory system in some invertebrates can be connected to the phylum Hemichordata, to which acorn worms belong.
The trunk of an acorn worm is divided into three regions: the proboscis, the collar, and the trunk proper. In some species, the trunk possesses gill slits, which are part of the respiratory system, and the heart-kidney complex, which is associated with excretory and circulatory functions. Unlike arthropods with a hemocoel and dorsal blood vessel, acorn worms have a simpler closed circulatory system.
Regarding the nervous system, acorn worms have a dorsal nerve cord, which is different from the ventral nerve cord found in arthropods like peripatus.
While the references mostly discuss the organs and bodily systems of other groups of animals such as arthropods, annelids, and specific invertebrates, they collectively highlight the diversity of anatomical structures and systems across the animal kingdom, including those in acorn worms.