Oligochaetes have well-developed heads chaetae for locomotion lungs for respiration a muscular foot a radulaWhich one of the following animals has an open circulatory system? squid earthworm mussel octopus polychaeteplease help with these two questions

Oligochaetae is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms. These worms usually have few setae (chaetae) on their outer body surfaces, and lack parapodia, unlike polychaeta. Oligochaetes are well-segmented worms and most have a spacious body cavity (coelom) used as a hydro skeleton. They range in length from less than 0.5 mm (0.02 in) up to 2 to 3 meters in the 'giant' species such as the giant Gippsland earthworm (Megascolides australis) and the Mekong worm (Amynthas mekongianus). Terrestrial oligochaetes are commonly known as earthworms and burrow into the soil. Open circulatory systems are systems where blood, rather than being sealed tight in arteries and veins, suffuses the body and may be directly open to the environment at places such as the digestive tract. Open circulatory systems use hemolymph instead of blood. The hemolymph performs the functions of blood, lymph, and intestinal fluid which are three different, highly specialized fluids in animals with closed circulatory systems. Instead of a complex and closed system of veins and arteries, organisms with open circulatory systems have a hemocoel. Hemocoel is a central body cavity found inside most invertebrate animals where both digestive and circulatory functions are performed. The hemocoel may have arteries through which the blood can reach tissues but these arteries are not closed and do not circulate blood as quickly as closed, muscle-assisted arteries.Oligochaetes have well-developed heads chaetae for locomotion lungs for respiration a muscular foot a radula The correct answer is chaetae The first segment, or prostomium, of oligochaetes is usually a smooth lobe or cone without sensory organs, although it is sometimes extended to form a tentacle. The remaining segments have no appendages, but they do have a small number of bristles, or chaetae. These tend to be longer in aquatic forms than in the burrowing earthworms, and can have a variety of shapes. Each segment has four bundles of chaetae, with two on the underside, and the others on the sides. The bundles can contain one to 25 chaetae, and include muscles to pull them in and out of the body. This enables the worm to gain a grip on the soil or mud as it burrows into the substrate. When burrowing, the body moves peristaltically, alternately contracting and stretching to push itself forward. Oligochaetes have well developed chaetae. Which one of the following animals has an open circulatory system? squid earthworm mussel octopus polychaete The correct answer is mussels. Squid, earthworm, octopus and polychaete have a closed circulatory system. Mussels have an open circulatory system meaning that blood is not completely transported within blood vessels. Tissues in mussels are covered in hemolymph in order for the exchange of gas and nutrients. The hearts of mussels have three chambers: one ventricle and two auricles. Blood (Hemolymph) is oxygenated in the gills and mantle, and then returns to the heart. Oxygenated hemolymph is pumped away from the heart through blood vessels to the body's organs. It is then moved to hemocoels where gases, nutrients, and wastes are exchanged. The hemolymph is reoxygenated in the gills and mantle before going back to the heart. Which one of the following animals has an open circulatory system? Answer: Mussels