Abstract
The model is based on observations of living animals, functional analyses of structures, and in situ studies.
The body-form and differentiation of legs, articles, joints, and spines reflect locomotionary adaptations to the tube. When moving outside the tube, a mucous thread released by the spinning legs (PII) acts as an anchoring life-line. The tube is built of various fragments and faeces, spun into a web as protection against predators, turbulence, UV-light, and desiccation. Three pairs of pleopods ventilate the tube by producing a posteriorly directed flow. When disturbed the flow can be reversed, as can the respiratory currents created by the epipodites. This, and the spine of the epipodite and the palpus of maxillulae, is a protection against fouling of ‘branchial cavity’.
The food, dominated by epiphytic organisms, is scraped off by the chelipeds. Special structures are developed as cleaning devices.
Transverse bands of bristles on the pleon act as a seal, preventing backflow in an irregular tube. By reducing the size of the pleon and the number of pleonites, pleopods, and transverse bands, a compact pumping mechanism is achieved, minimizing water leakage through the tube wall in the pleopod area.
From this model morphological characters of the phyletic group Tanaidae are presented.
