froesch d (5 risultati)

SC. Condizione: Gut. Obr., [KKAP9]. Deu 400g.

7 pp., 3 figs, gr. 8.

6 pp. + 5 plates, 6 figs, gr. 8 [with some underlining in the text].

The movements of the isolated buccal mass of Octopus vulgaris have been investigated. The beaks undergo rhythmic cycles of activity in the absence of applied stimulation and after electrical stimulation of the inter-buccal connective. Initial opening, closing, retraction and re-opening phases of movement are described. This cycle of movements is taken to resemble those in the intact animal. Anatomical and electrical evidence identifies the superior mandibular muscle as being partly responsible for the closing and retraction phases of movement. The inferior buccal ganglion determines the sequence of these buccal movements, but modification by sensory feed-back from the musculature is also implied. The preparation will allow a closer comparison of the control of movement in cephalopods and gastropods. 15 pp., 9 figs, gr. 8.

The leucophores of Octopus vulgaris are much branched cells bearing, all over the surface, small clubs that contain electron-dense material of an unknown nature. Some tens of leucophores are organized to form a "sponge" in the centre of the chromatic unit, which can be elevated above the peripheral region. This central region reflects light over a broad band and may be important in camouflage. The chromatic unit also contains iridophores and chromatophores. The latter may be yellow, orange, red or black, and the different types are interspersed among one another in a regular manner. The chromatophores are disposed in a precise way with respect to the leucophores, the black ones lying above holes in the sponge. The possible significance of this arrangement for camouflage is discussed. 11 pp., 6 pls, gr. 8.