. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STRENGTHENING OF URCHIN SKELETONS 137 collagenous sutural ligaments. meridional suture peristomial membrane Aristotle's Lantern Figure 1. Schematic of interambulacral suture geometry and sutural ligament attachment. Interambulacral. meridional, and circumferential sutures are illustrated. Ligaments bind together adjacent plates (magni- fied inset of cross-section of a suture). at the edges and faces of the plates and by the addition of new plates at the apex (Deutler. 1926). Initially apical, new plates gradually migrate ado
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STRENGTHENING OF URCHIN SKELETONS 137 collagenous sutural ligaments. meridional suture peristomial membrane Aristotle's Lantern Figure 1. Schematic of interambulacral suture geometry and sutural ligament attachment. Interambulacral. meridional, and circumferential sutures are illustrated. Ligaments bind together adjacent plates (magni- fied inset of cross-section of a suture). at the edges and faces of the plates and by the addition of new plates at the apex (Deutler. 1926). Initially apical, new plates gradually migrate adorally during growth. Skeletal plates may show seasonal or yearly growth rings that reflect changes in growth rate (Gage. 1991. 1992a. b) or spurts of growth (Pearse and Pearse, 1975). Urchins may also shrink under conditions of lowered food avail- ability or overcrowding, as observed, for example, in Diu- dema antillamin (Levitan, 1988), and in Strongylocentro- tus purpuratus (Ebert, 1967). In Heliocidaris erythro- grcinuuu. shrinkage is associated with diminution of sutural gaps (Constable, 1993). That sutural ligaments might strengthen the skeleton was suggested in a taphonomic study in which decom- posed urchin skeletons disarticulated at sutures and broke at lower forces than did undecomposed urchin skeletons (Kidwell and Baumiller, 1990). On the basis of histologi- cal and morphological evidence, sutural ligaments were interpreted as "stress-breakers" that evenly distribute stresses and thus contribute to the structural integrity of echinoid skeletons (Moss and Meehun. 1967). In other theoretical and experimental studies of the structural me- chanics of echinoid skeletons (Telford, 1985b; Dafni. 1986. 1988: Baron. 1991a. b; Ellers. 1993; Philippi and Nachtigall, 1996), the possible structural role of the su- tural ligaments has not been a focus. Nor has a possible structural role for the peristomial membrane been tested. Although this membrane is not flexurally s
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
