Ultrastructure of the podia of Amphiura chiajei and Amphiura filiformis and their role in feeding

Abstract

O Deceased.Morphological study of the podia of the suspension feeding Amphiura ¢liformis and the deposit feeding Amphiura chiajei revealed sensory^secretory complexes in the podial epidermis, consisting of four cells, two secretory and two sensory. Large mucus cells were found in association, but not exclusively, with the sensory^secretory complexes. In A. ¢liformis, mucus cells stained positively for both acid and neutral mucopolysaccharides, while, in A. chiajei, these cells stained only for acid mucopolysaccharides. The surfaces of the arm podia in A. chiajei were relatively smooth, while the arm podia of A. ¢liformis bear papillae. The sensory^secretory complexes open through numerous paired pores, with each pair having an intervening cilium. Pores were restricted to the podial tip in A. chiajei, while in A. ¢liformis they are concentrated on the podial tip and on the papillae. Amphiura chiajei shows very little di¡erentiation of the podia along the length of the arm. In A. ¢liformis, the distal podia have papillae throughout their entire length, with pores being found on the head region and the papillar tips. Here, the papillae are oriented in such a way (i.e. facing inward towards the ventral arm plate) as to increase the area of the ¢ltering surface of the podium, serviced by the sticky secretions from the sensory^secretory complexes. The proximal podia are relatively simple in structure and are thought to function more in the transportation of mucus wrapped particles to the mouth rather than in their capture. The di¡erence in structure of the podia and chemical composition of podial secretory cells are taken to re£ect the di¡erence in feeding styles of the two species.

Troglomorphism in the brittle star Ophionereis commutabilis Bribiesca-Contreras et al., 2019 (Echinodermata, Ophiuroidea, Ophionereididae)

“…Distal tube feet play an important role on detritus and suspension feeding (Warner 1982), which could explain O. commutabilis having longer distal tube feet than O. reticulata, suggesting that detritus and suspended particles are also (Mejía-Ortíz et al 2013) an important source of food in the cave El Aerolito. On the other hand, oral tentacle, as well as proximal and middle tube feet, are commonly less specialized (Keogh and Keegan 2006), which provides an explanation for cave species not having longer structures than epigean congeners.…”

Mechanisms of temporary adhesion in benthic animals

“…The larval tentacles of the dendrochirote holothurian Aslia lefevrei bear numerous approximately 200 µm long projecting papillae that contribute mechanically to adhesion by increasing the area of contact (Costelloe, 1988). Keogh & Keegan (2006) found that the tube feet of the ophiuroid Amphiura filiformis are also covered with papillae, whereas the tube feet of Amphiura chiajei are smooth, and they attributed this difference to the feeding styles of the two species: A . filiformis is a suspension feeder and requires a large filtering area, achieved by means of the sticky papillae.…”