Arthropods and Molluscs, although both common in harsh coastal environments, in fact do not share many similarities due to the differences in their adaptations to their environments. Arthropods are described as segmented coelomates that have jointed appendages whereas Molluscs are coelomates, but have neither segmented bodies nor jointed appendages. By animal classification, both Arthropods and Molluscs have bilateral symmetry, are tripoblastic (having three layers of tissues in tissue development – ectoderm, endoderm and mesoderm) and have protosome pattern of development. Arthropods eventually branches away from Molluscs due to ecdysis, as they subsequently develop the ability to undergo molting, which Molluscs cannot.
First, we look at
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Arthropods have mouthparts adapted for piercing vegetation and sucking out plant juices, whereas Molluscs possess a radula that consists of rows of teeth that enables the animal to scrape algae from surfaces of rocks. Lastly, Arthropods and Molluscs both engage in filter-feeding, although not entirely similar. The bivalve molluscs filter-feed fine particles from the water, and similarly, barnacles from Arthropods also filter-feed with their legs. However, according to Bryant (n.d.), Molluscs such as clams and mussels are internal filter feeders because “they bring in water through one opening (the incurrent siphon), pump it through the filter to remove microscopic food particles, and discharge it through another opening (the excurrent siphon)”. In contrast, Arthropods like Barnacles are external filter feeders, in which no water is pumped through the filter. Instead, barnacles stand on their heads and use their legs for filter-feeding by “using grasping motion, rhythmically extending their feet upwards into the water, and then quickly bringing them back inside the shell along with any captured food” (Bryant,