Carmichael’s Concise Review
can be vigorous? Te tail of a lizard affects its ability to run, leap, mate, and escape the next predator, so losing the tail is a costly sacrifice. Te precise mechanism that provides the lizard with the advantage of retaining the tail in situations that are not life-threatening, yet readily shedding it when threatened, has recently been addressed in an elegant study by Navajit Baban, Yong-Ak Song, and others. Baban et al. studied the tails of three common lizards, two
species of geckos (Hemidactylus flaviviridis and Cyrtopodion scabrum, of the Gekkonidae family), and one from the family of “true” lizards (Acanthodactylus schmidti, of the Lacertidae fam- ily). In the laboratory the tail of the live animal was passively autotomized, and the event was captured by high-speed (3,000 frames per second) video. Te proximal and distal exposed sur- faces of the tail (the fracture plane) were immediately preserved in formalin and prepared for scanning electron microscopy (SEM). Tere are several potential facture planes in the tail, allowing for portions of the tail to be sacrificed, depending on the need. Tis is made possible by the fact that the lizard tail is not one entity, but assemblies of segments connected via the fracture planes. Te micrographs reveal assemblies analogous to “plugs-
and-sockets.” Te distal part contains eight circumferen- tially arranged wedge-shaped muscle bundles representing the “plugs,” and the proximal part encloses complementary grooves or pockets representing the “sockets.” Closer exami- nation of the distal part showed tightly packed micropillars of muscle with dilated ends so that they resembled mushrooms. Te surface of the mushrooms had many nanopores and a few nanobeads. Te magnified view of the complementary pockets showed imprints of the tops of the mushroom-shaped pillars. Tese surface imprints implied that the mushroom tops did not penetrate the proximal pockets, which would have resulted in a stronger connection. Instead, the lizard has adopted a dif- ferent strategy for tail attachment, with many microscale and nanoscale points of contact that create a firm, but not rigid, attachment. To explore the role of the nanopore-covered micropillars,
Baban et al. built a biomimetic model of polydimethylsiloxane, a rubbery, flesh-like material. Tey performed mechanical tests on their model and correlated the results with the high-speed video of tail autotomy. Tey found that the spaces between micropillars, as well as other voids, slowed the spread of an ini- tial fracture. Tese and several other studies lead Baban et al. to hypoth-
esize that contraction of skeletal muscle fibers (which are under voluntary control) would provide favorable autotomy condi- tions. As they state it, the tail remains sturdily and faithfully connected to the body, quickly detaching only when the lizard wills it. It is tempting to speculate that autotomy of the lizard tail is a voluntary survival response.
References [1] NS Baban et al., Science 375 (2022)
https://doi.org/10.1126/ science.abh1614.
[2] Te author gratefully acknowledges Drs. Navajit Baban and Yong-Ak (Rafael) Song for reviewing this article.
2022 July •
www.microscopy-today.com
alluxa.com 9
YOUR
FLUORESCENCE MICROSCOPY
FILTER PARTNER
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72
