The Z stack of a late brachiolaria larva of the asterinid sea star Parvulastra exigua recorded by confocal laser scanning microscopy

Abstract

The Z stack in this archive is representative of a late brachiolaria larva of P. exigua recorded in the Olympus FluoView 1000 laser scanning system. It is from a study of the morphology of the coeloms and their interconnexions in a pre-metamorphic brachiolaria larva. The data of the Z stack show the coelom on the left and right sides of the larva linked anteriorly, over the head of the archenteron, by a common anterior coelom. The asymmetry of the larger left and the smaller right larval coeloms translates into the oral and aboral coeloms of the juvenile sea star. The morphology of the coeloms in a late brachiolaria larva of an asteroid has application in the search for morphological homology between the echinoderm classes and the deuterostome phyla. ***** Late brachiolaria larvae of P. exigua were fixed seven days after fertilization in 2.5% (v/v) glutaraldehyde in filtered sea water for 1-2 hours, dehydrated in an ethanol series to 100% ethanol, then cleared in 2:1 (v/v) benzyl benzoate/benzyl alcohol. The larvae, made autofluorescent by glutaraldehyde fixation, were mounted in the clearant in a chamber between glass coverslips that sealed a hole cut through a conventional microscope slide. The larvae were viewed in the Olympus FluoView 1000 laser scanning system (version 1.7.1.0) attached to an Olympus IX81 inverted microscope. Each larva was excited with a 633 nm helium-neon laser with the emission collected from 645-745 nm. A stack of images was collected along the Z axis (the Z stack) with a pixel dimension of 1.24 x 1.24 µm and a slice thickness of 1.10 µm averaged over two frames with a 20x UplanApo objective lens NA 0.7 in a 512 x 512 pixel array, 12 bits/pixel.