Morphometry and mechanical design of tube foot stems in sea urchins: A comparative study

peer reviewe

Estimation of the attachment strength of the shingle sea urchin Colobocentrotus atratus, and comparison with three sympatric echinoids

peer reviewe

How does bioadhesion impact locomotion in the starfish Asterias rubens?

Starfishes use a multitude of small hydraulic organs (i.e., the tube feet or podia), to locomote, to attach strongly to the substrate, and to pry open the mussels on which they feed. Podia are secretory organs in which two types of adhesive cells co-secrete a blend of adhesive proteins to form the adhesive layer joining the tube foot to the substrate [1]. Despite the importance of podia in the sea star locomotion mechanism, the regulation of the number of podia sticking to a surface during movement is still poorly understood. In this study, we used an aquarium equipped with a total internal reflection (TIRF) system and developed a robust technique for quantifying the number of podia sticking to the substrate during locomotion. We found that the contact area of individual podia increases during the adhesion phase to become a perfect circle. Surprisingly, we measured a very low percentage of podia in contact with the substrate during locomotion in Asterias rubens. Although the number of sticking podia, as well as the instantaneous speed, remains constant during movement, this number increases proportionally with the size of starfish. In contrast, we found that the average speed of movement decreases with the increase in the specimen size. Based on these preliminary results, we plan to study the role of important environmental factors, such as substrate angle and temperature of the environment on starfish locomotion, and we will determine the adhesion energy exerted by a sea star according to the number of sticking podia. 1. P. Flammang, A. Michel, A. Van Cauwenberge, H. Alexandre and M. Jangoux, Journal of Experimental Biology, 201, 2383-2395 (1998)

Between emission and perception: do luminous brittlestars perceive their own light?

peer reviewe

Measurement of the attachment strength of brachiolaria larvae and metamorphic individuals of the sea star Asterina gibbosa by centrifugation method

peer reviewedTwo methods are generally used to measure the adhesive strength of invertebrate larvae: direct measurement with a force transducer connected to the organisms and indirect measurement with a water flow used to dislodge the organisms. Each of these methods, however, has its drawbacks. The present study aimed to design a simple and straightforward method to measure the adhesion strength of marine invertebrate larvae based on centrifugation. This centrifuge technique works in immersed conditions and applies forces acting at 45° to the substratum, therefore mimicking natural conditions. It was tested with three different substrata on two developmental stages of the sea star Asterina gibbosa: the brachiolaria larvae, which use temporary adhesion, and the metamorphic individuals which use permanent adhesion. Measurements were completed by SEM and TEM observations of the larval adhesive organs. The critical detachment force (force required to detach 50% of the larvae) of brachiolaria larvae attached to glass (36 ± 9 µN) and rough PMMA (43 ±16 µN) were equivalent and both significantly higher than the critical detachment force measured on smooth PMMA (11 ±8 µN). Most metamorphic individuals, on the other hand, resisted to the highest centrifugation speed used, corresponding to a force of 2.13 mN. For the hydrodynamics of larval settlement and metamorphosis, force is the ecologically relevant factor, and adhesion forces obtained by centrifugation are strikingly similar to forces measured for other marine invertebrate larvae with other methods. This indicates the usefulness of the centrifugation technique to compare adhesion of larvae between different species or development stages, or between different treatments

A thresholding method to understand the locomotion of the sea star Asterias rubens.

Starfishes use a multitude of small hydraulic organs (i.e., the tube feet or podia), to locomote, to attach strongly to the substrate, etc... Podia are secretory organs in which adhesive cells secrete a blend of adhesive proteins to form the adhesive layer joining the tube foot to the substrate. Despite their importance in the locomotion of the starfishes, the regulation of the number of podia sticking to a surface during movement is still poorly understood. In this project, we used an aquarium equipped with a total internal reflection (TIRF) system to detect automatically sticking podia with a thresholding method

The attachment complex of brachiolaria larvae of the sea star Asterias rubens (Echinodermata): An ultrastructural and immunocytochemical study

peer reviewe