Meeting Abstract
P2.116 Sunday, Jan. 5 15:30 Claustrum Puddles in Marsupial Brains JOHNSON, J.I.**; FENSKE, B.S.; JASWA, A.S.; Michigan State Univ.; Michigan State Univ.; Michigan State Univ. johnij@aol.com
The canonical claustrum, in the forebrains of placental mammals, is a thin sheet of cells between cortex and underlying striatum. But we have reported cases where claustrum cells spread out from the sheet to form “puddles”, located in different places in different taxa. Anthropoid primates show a fronto-inferior puddle, pigs have a huge posterior lobed puddle, and many carnivores have a dorsal pyramidoid puddle, large enough to allow detailed experiments, such as those showing, in cats, that this region is an auxiliary of visual cortex. We explored brains of the other major branch of the mammalian radiation, the marsupials, to learn if these show taxon-specific puddles. We used representatives of the 3 major orders of marsupials, 1) from the carnivorous Dasyurimorphia: Opossum, Native Cat, Antechinus, and Dunnart; 2) from the herbivorous Diprotodontia: Wombat, Tammar Wallaby, and Gray Kangaroo; 3) from the smaller ominivorous order Peramelimorphia: Brown Bandicoot. In each we examined a complete anteroposterior series of Nissl-stained coronal sections. From these we made quantitative 3-dimensional reconstructions to display the variations in the puddles. We found in our Wombat a large balloon-shaped puddle at the front end of the claustrum, and a much smaller elongated postero-dorsal puddle. Our Kangaroo and Wallaby showed smaller versions of both these puddles. Most interesting, a dorsal pyramidoid puddle in the Native Cat is very like that of placental domestic cats. The small brains of the tiny, shrew-like, Antechinus and Dunnart, and the larger brain of the Opossum, have barely discernable claustrums on the dorsal aspect of the fundus of the rhinal fissure. Our Bandicoot showed a small, striated, claustrum near the sulcal fundus. The marsupial radiation, like the placental, shows taxon-related variations in claustrum morphology.
