Gills and a well developed nervous system
legs.
Closed hydrovascular for echinoderms, open haemolymphatic for arthropods. ^^
Sponges, Cnidarians, Mollusks, and Echinoderms are not Arthropods.
The types of organisms which have segmented bodies include annelids, arthropods, echinoderms, and chordates. Some of the most obvious examples of segmentation are found in insects which belong to the arthropods.
A. Arthropods
No, echinoderms do not have bilateral symmetry. They have radial symmetry, which means their body parts are arranged around a central axis.
sponges+mollusks+arthropods+worms+octopods+echinoderms
Gills and a well developed nervous system
Lobsters are neither echinoderms nor mollusks like clams. They are also not arachnids. Instead, they are crustaceans, a subsection of arthropods.
Appendages.............in multiples of........numbers........and clouds
Arthropods and echinoderms are two distinct groups of invertebrates. Arthropods, such as insects, spiders, and crustaceans, have segmented bodies, exoskeletons made of chitin, and jointed appendages. In contrast, echinoderms, which include starfish, sea urchins, and sea cucumbers, possess a radial symmetry, a calcareous endoskeleton, and a water vascular system for movement and feeding. Additionally, arthropods are primarily found in terrestrial and aquatic environments, while echinoderms are exclusively marine organisms.
Echinoderms are mostly marine while arthropods dwell in almost all habitats.