O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)
Adler, Kr.: Sensory aspects of Amphibian navigation and compass orientation 7-18. o.
/ Most revealing were those experiments in which the opaque block was affixed on salamanders with eyes intact: these animals also failed to orient (Fig. 4-C). Taken together, these experiments suggest that the critical receptor for polarized light in tiger salamanders is extraocular but cranial in location and, based on earlier experiments by several researchers, the pineal complex was suspected. Later tests with tiger salamanders and also bullfrog tadpoles, in which the eyes or various portions of the pineal complex or both were removed, confirmed the involvement of the pineal (see ADLER 1976, for review; also TAYLOR & ADLER 1978; TAYLOR & AUBURN 1978). The pineal complex in amphibians arises as a dorsal evagination of the diencephalic roof (EAKIN 1973). Ia most frogs and toads (Anura) it consists of two discrete bodies: (1) an intracranial pineal body or epiphysis cerebr i, and (2) an extracranial frontal organ (Stirnorgan, pineal end organ), as illustrated In Figure 5. In salamanders (Caudata) and caecilians (Gymnophiona) a pineal body is present but the frontal organ is lacking. Electrophysiological evidence suggests that both pineal structures in amphibians are photosensitive and, ultrastrucuirally, elements in both the frontal and pineal organs closely resemble the photoreceptive visual cells in the lateral eyes (HAMASAKI & EDER 1977). The pineal complex was present even in the earliest amphibians since Ichthyosteg a from the late Devonian of Greenland possessed a large pineal foramen (ROMER 1966). WITH EYES [mit Augen] A CONTROL (Kontrolle) B. SKIN CUT ( Haut geschützt) EYELESS [ohne Augen] E CONTROL (Kontrolle) F SKIN CUT (Haut geschlitzt) (opake Plastikscheibe) D CLEAR PLASTIC (transparente Plastikscheib*) H CLEAR PLASTIC (transparente Plastikscheibe) Fig. 4. Directional behavior of tiger salamanders ( Ambystoma tlgrinu m) with and without eyes under linearly-polarized light. Data plotted as in Fig. 2 except that shaded edges represent quadrants in which animals were expected to score if the polarization axis (e-vector, denoted by dashed lines) is perceived. In composite diagrams, separate test and retest are designated by solid and half-solid dots, respectively. Arrows indicate the mean axes for each group, except where data are not significant (n.s.; chi-square test, alpha = 0.05). Note that all groups of animals orient in the predicted directions except for those where the top of the head is covered with opaque plastic, whether they have eyes intact or not (C and G; shaded boxes). Adapted from ADLER & TAYLOR (1973) ) G OPAQUE PLASTIC (opake Plastikscteibe)
