Question

check your progress 1.1 are the spines of sea stars movable? 1.2 were you able to locate pedicellariae on the epidermis? dermal branchiae? 1.3 how do the arms and central disc of sea stars differ from those of brittle stars discussed earlier? 15 sea star internal anatomy to reveal the internal anatomy of your sea star, you will make several cuts through the epidermis. review the dissection diagram to assist you in this process. procedure 1 use a sharp pair of dissecting scissors to make a shallow incision on the aboral side through the epidermis encircling the central disc, leaving the madreporite in place. 2 make additional incisions along the outer margins of one or more arms, extending from the original circular incision distally along each arm. 3 do not carelessly rip away the epidermis; rather, gently tease it apart from the underlying tissue with a dissecting needle or blunt probe, especially in the region of the central disc. the underlying organs lie very close to the inner surface of the epidermis and actually adhere to it in some places. sloppy technique here may ruin underlying organs! 4 the internal anatomy of each arm is identical, so you should work from the aboral surface toward the oral surface, identifying each structure or organ as you proceed (table 15 - 3). dissection diagram 1 use scissors to make a shallow incision through the epidermis encircling the central disc, leaving the madreporite in place. 2 make additional incisions along the outer margins of one or more arms, extending from original circular incision distally along arm. 3 gently tease away the separated portions of the epidermis, being careful not to damage underlying structures. 302 exploring zoology: a laboratory guide

Explanation:

1.1 The spines of sea - stars are movable. They can be used for protection and locomotion - related functions.
1.2 Pedicellariae are small, pincer - like structures on the epidermis of sea - stars used for cleaning the surface and capturing small prey. Dermal branchiae are respiratory structures. Their presence can be determined through careful dissection and observation.
1.3 Sea - star arms are usually broader and more fleshy, and they are more closely attached to the central disc. Brittle star arms are more slender and more freely movable, and they are more distinctly separated from the central disc.

Answer:

1.1 Yes
1.2 Answers may vary depending on the dissection (Yes/No)
1.3 Sea - star arms are broader and more fleshy, more closely attached to the central disc; brittle star arms are more slender and more freely movable, more distinctly separated from the central disc.