IOB
The Tagmatized #Echinodermnbsp; R L Turner
Fig. 1 Examples of perioral tagmata in #echinoderms.
@sicbjournals.bsky.social![(A) The oral frame of Ctenodiscus crispatus (Asteroidea; dissected and briefly treated with bleach, aboral view) includes 35 elements: 10 first ambulacral ossicles (am1), each representing the conjoined first and second ambulacral #ossicles in the juvenile rudiment; 10 second ambulacral ossicles (2); 10 oral plates (op), mostly hidden from view by the ambulacral ossicles but revealed by some of their oral spines (sp); 5 odontophores (od), unpaired interradial extraxial elements present in many families of seastar. Scale bar 5 mm. (B) The oral frame of Ophiomastix wendtii (Ophiuroidea; view of oral surface) includes 30 externally visible ossicles as well as other internal ones: 5 oral shields (os); 10 adoral shields (as); 10 oral plates (op); 5 first ventral arm plates (vp); 5 dental plates (dp, position indicated but mostly obscured by clusters of their tooth papillae [encircled]). Scale bar 2 mm. (C) The perignathic girdle of Lytechinus variegatus (Echinoidea, dissected, treated with bleach, internal view of test) consists of 5 pairs of auricles (au), each pair at the proximal end of an ambulacral column (am), and 5 apophyses (ap) of the interambulacral columns (ia). Scale bar 5 mm. nbsp;](https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:2646spzjwjyehz3svwrjfs2q/bafkreibxjylcjhntobydyoaltltnryx47fhyduzgka6rzoiynrtrzfrrsu@jpeg)
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@worldunderthewaves.bsky.socialAlways be wary when long-spined sea urchins are around.
Their venom is, luckily, mild and non-fatal to humans, but those stinging spines are bound to hurt!
