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New Abstracts for the Developmental Biology Society Meeting

New Egg-laying Mammal Found in North America

Brightly colored eggs have been observed in parklands throughout the United States and Canada, especially around the vernal equinox. However, the animal responsible for laying these eggs has not yet been identified. Rebach and Rebach (1980) had constructed traps of candy corn, and they observed the behaviors of those animals caught in the traps. They suggested that a small lagomorph, Leapus paschalis, was the animal responsible for laying these eggs. If so, this "Easter bunny" would be the first egg-laying mammal observed in North America. We now confirm this observation and have detailed the remarkable predator-escape mechanism of these rabbits.

When confronted by a predator, usually an immature bipedal mammal, Leapus paschalis females lay their eggs directly in the predator's path. This distracts the predator, allowing the rabbit to escape. Moreover, if grasped, both males and females will elaborate a sticky secretion of casein, carbohydrates, fats, oils, and cocoa. This will form a reasonable replica of the rabbit, which will escape out the bottom.

Pax6 Expression in Solanum tuberosum

Pax6 expression has been found in eyes of animals as diverse as planaria, fruitflies, and humans. Andrew Stein-Dionne (1998) has extended this observation by analysing the eyes of the russett potato, Solanum tuberosum. He finds that the eyes of potatoes have Pax6 expression. Moreover, he shows that the eyeless potato is deficient in Pax6. The mutation that results in eyelessness appears to be in a coding region that creates a stop-codon in the first exon. By inserting the Drosophila Pax6 gene into the potato embryo, he discovered that one can restore the expression of potato eyes in this genus (Figure 1). Thus, Pax6 expression appears to be necessary for the production of potato eyes.

Figure 1
Figure 1   Pax6 expression in potato eye rudiments. (A) Localization of Pax6 expression by in situ hybridization. A probe for Drosophila Pax6 shows localization of Pax6 expression to the sites where eyes are forming. (B) Similar in situ hybridization to eyeless potatoes show no areas of gene expression. (C) Transfection of potato embryos with a vector encoding active Drosophila Pax6 (wild-type eyeless gene) induces both Pax6 expression and eye formation. The eyes are potato eyes, and not the compound ommatidial eye of insects. (After Stein-Dionne 1998).

Distal-less Protein Expression in Human Umbilical Rudiments

Anyone who has ever seen human beings on a beach knows that our species comes in two distinct morphotypes &mdash innies and outies. With reference to umbilical anatomy, this appears to be a random event, although it is said that innies run in families. Panganiban et al. (1997) demonstrated that a Distal-less protein (Dll in Drosophila, Dlx1-3 in mammals) is expressed in the distal tip of those regions destined to stick out from the main body axis. To determine if Dlx expression provided a genetic basis for this morphological variation, Polly and Spiro Keats probed human embryos with antibodies against the Dlx proteins. They found Dlx3 expression in the umbilical rudiment. They showed that as early as the ninth week of gestation, Dlx3 was found in the tips of those umbilical rudiments destined to become outies. Such expression was not found in embryos whose umbilical anatomies proved to be innies (Figure 2).

Figure 2
Figure 2   Two nine-week human fetuses stained for the presence of the distal-less (DLX3) protein. (A) Presence of the DLX3 protein (arrow) in a fetus that became an outie. (B) No expression of DLX3 (arrow marking umbilicus) in the fetus destined to become an innie. (After Keats and Keats, 1998).

Gefilte Fish Embryo Found!

Research by Goodman and Manischevitz (1998) has finally identified the long-sought embryo of the gefilte fish. It is a chimeric pike and whitefish blastula which should (if all goes well) develop into a mature Gefilte (Figure 3). Fate maps are presently being constructed using horseradish peroxidase.

Figure 3
Figure 3   The blastula of a gefilte fish. (From Goodman and Manischevitz, 1998).

References

Goodman and Manischevitz (1998) The days of wine and charoses. Red Sea J. Zool. 5758: 42-142.

Keats, S. and Keats, P. (1998) Did Adam have a belly button? Journal of Navel Research (1 April) 100: 42 - 142.

Panganiban, D. and thirteen others. The origin and evolution of animal appendages. Proc. Natl. Acad. Sci. USA. 94: 5162 - 5166.

Rebach, S. and Rebach, J. A. 1980. Seasonal egg-scattering behavior of Leapus paschalis, the Easter bunny. J. Irrepr. Res. 26 (1): 9-10.

Stein-Dionne, Andrew (1998). Pax6 and 6-Pax: Here's looking at you, spud. J. Molecular Choreography 100 (1 April): 42-142.

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