In a reverse hierarchy, the conceptual pyramid of authority is turned upside-down, so that the apex is at the bottom and the base is at the top. This model represents the idea that members of the higher rankings are responsible for the members of the lower rankings.
Along the sides of the body is a light-colored horizontal stripe called the lateral line. The line is made up of a series of tiny pores that lead to receptors that are sensitive to the mechanical movement of water and sudden changes of pressure.The spiny dogfish has a double dorsal fin.The anterior dorsal fin is larger than the posterior dorsal fin.The spiny dogfish has the presence two spines, one immediately in front of each dorsal fin. The spines carry a poison secreted by glands at their base.he spiny dogfish has a double dorsal fin. The anterior dorsal fin is larger than the posterior dorsal fin. The spiny dogfish has the presence two spines, one immediately in front of each dorsal fin. The spines carry a poison secreted by glands at their base.
Skeletal Composition. Echinodermata means spiny skinned.. Surprisingly, the external spines are composed of the same material as the internal skeleton. Calcium carbonate and protein form the rigid inner skeleton, or ossicles, of echinoderms.The exoskeleton is composed of soft, spongelike micro-structures called stereom.he uniform symmetry of echinoderms sets the creatures off from other marine life. All echinoderms are pentameral -- they have limbs in multiples of five. This trait is easily recognizable in starfish and brittle stars with only five limbs.