Light and electron microscope studies of the digital lamellar setae of geckos and anoline lizards demonstrate that the free ends of the setae consist of flattened spatulas of less than 1 p in width. The anoline setae are simple structures usually less than 30 , u in length and with a single terminal spatula to each seta. In contrast the setae of geckos are complex structures of about 100 p in length, with numerous branchings, and having many spatulas per seta. The spatulas of Gekko and Aristelliger were smaller (0.2-0.4 j~ in width) than the spatulas of Anolis (0.8 p in width). The electron microscope studies indicate that the scales of lizards appear to be covered with small epidermal spines (1.5 / . L long). The setae of anoles and geckos are considered to have evolved independently from these more primitive epidermal spines. It is further suggested that the mechanism that allows the lamellae to adhere to the substratum is a surface phenomenon. The spatulas provide a large surface that is in contact with the substratum and thus produces a large total frictional force. The a layer of the lizard stratum corneum can be readily identified in the lamellae. However, the structure of the j 3 layer is not easily interpreted and there is evidence of a fibrous layer between the Oberhautchen and the a layer in the skin of the outer lamellar surface.For many years the ventral surface of the enlarged digital lamellae of gekkonid lizards have been known to possess microscopic "hair"-like projections. The gross structure of these setae and of the lamellae of the toes have been studied by various authors (see references in Lange, '31; Gourvest, '59; and Maderson, '64). The function of these microscopic setae have been studied by Dellit ('34) and Mahendra ('41). The setae are believed to function in providing traction by intermeshing with irregularities of the substratum and permit the lizards to easily climb vertical surfaces. The presence of similar setae on the digital lamellae of anoline lizards (Iguanidae) has not been so widely recognized even though they were described by Braun in 1872. In the Gekkonoidea the setae appear to be present on the digits of most of the species except those belonging to the family Eublepharidae (Underwood, '54) while in the family Iguanidae they have only been found in members of the anoline group (i.e. Anolis, Chamaeleolis).Under the light microscope the setae appear as densely packed hair-like projections about 100 CI long in the geckos and about 20 p long in the anoles. The free ends of the setae are not resolvable with the light microscope. In the geckos the J. MORPW., 117: 271-294.setae have the appearance of being packed in groups while in the anoles they appear single.Our study of the digital setae began as an interest in the method of regeneration of these rather bizarre structures, however, the current article is a description and comparison of the fully formed setae in some anoles and geckos. An article is currently in preparation discussing the development of the setae.
MATERIALS AN...
The epidermal setae and the spinules of the digital lamellae of anoline and gekkonid lizards are shed periodically along with the rest of the outer layer of the skin. These structures are developed within the lamellae prior to ecdysis. The setae are larger and more complicated than the spinules and begin their development first. The setae of Anolis start as aggregations of tonofibrils beneath the plasma membrane of the presumptive Obel-hautchen cells. These cells are arranged in rows parallel to the surface, several cell layers beneath the alpha layer of the skin. The developing setae protrude into the clear layer cells as finger-like projections, with the tonofibrils longitudinally oriented in the direction of growth. About 100 setae are formed by each Oberhautchen cells in Anolis. In late development, the clear layer
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