File:American malacological bulletin (1988) (18157703241).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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HANLON AND WOLTERDING: OCTOPUS BRIAREUS 33 static morphological array of elements in the skin (especially the chromatophores). In O. vulgaris there is a conspicuous morphological unit - a system of grooves that create obvious skin patches, or "chromatic units," but this arrangement is not seen in all octopuses, including O. briareus. The concept of a "physiological unit" can also be considered (Packard, 1982), based upon neural control of the units by motor axons originating in the CNS. In our study we limit our analysis to small circular "visual units" that are mainly physiological en- tities generally appearing dark or light in various components (Figs. 18-23). Each visual unit has a papilla in the center and varies in size, but there are three basic size categories: 0.5 mm diameter with approximately 80 chromatophores; 1.5 mm with approximately 700 chromatophores; and 3.0 mm with ap- proximately 1500 chromatophores. Each visual unit also com- prises an unknown number and arrangement of reflecting cells such as the leucophores that reflect the bright white seen in many components. We do not promote use of the term "visual unit" until detailed work is undertaken. COMPONENTS: These are the recognizable and repeatable parts that constitute the whole body patterns. Thirty-five are listed in table 4 under four categories: (1) chromatic, (2) tex- tural, (3) postural and (4) locomotor. As explained by Packard and Sanders (1971), components may be expressed in a wide variety of combinations. Some components commonly go together while others are mutally exclusive. Collectively they confer upon the animal the ability to show a highly diversified range of body patterns. Chromatic components are those concerned strictly with color. They are conspicuous and well defined and occur repeatedly in the same relative position on the body. They are recognizable because of contrasting light and dark areas. The light components result when the overlying chromato- phores are retracted and light is reflected from the underly- ing leucophores or iridophores. The dark components result from light that is reflected from and transmitted through the pigment granules of expanded chromatophores. Chromatic components are physiological entities that reflect selected neural activity because individual chromatophores are con- trolled directly from the CNS (cf. Messenger and Miyan, 1986). The components are numbered (Table 4) and most are self-explanatory and indicated on the figures. Figure 24 depicts the arrangement of seven chromatic components that are associated with the eye. The appearance of the eye fluc- tuates constantly, and it can appear prominent or obliterated depending upon the combinations of these components that are expressed at any given moment. The iris can be either light (Comp. 2) or dark (Comp. 10) depending upon the degree of expansion of the iris chromatophores. The pupil of the eye always appears black. Depending upon the quantity of inci- dent light, the pupil can appear as a thin horizontal slit or a circle. The outer perimeter of the eye is generally the same color as the head, and with expanded chromatophores it forms the Dark eye ring. The region above the eye can also be papillate (Comp. 21). In young animals, the presence or absence of expanded chromatphores on the outer eye ring
Text Appearing After Image:
Fig. 24. The chromatic components of the eye. Note the range of expression. Not all pupils were printed horizontal. A, Dark eye ring; B, Pupil margin; C, Pupil; D, Iris; E, Iris margin. determines how obvious the Reflective eyeball will appear in hatchlings. The Dark eye ring can make the eye appear larger by matching the color of the eye or contrasting with the Iris margin. The Pupil margin and Iris margin are thin rings that enhance the contrast of the pupil or eye. Some representative illustrations of components common in young O. briareus are shown in Figs. 25-32. The White patches (Figs. 20-23; Comp. 6) are irregular- ly shaped and made up of several circular visual units in which the chromatophores are retracted. The white Head bar (Figs. 26, 29, 30; Comp. 4) consists of an irregular, transverse row of white patches between the eyes. The Transverse mantle bar (Figs. 29, 30, 33; Comp. 5) is irregular in shape and con- sists of a series of white patches each with a White papilla (Comp. 7). White transverse arm bands (Figs. 20-23; Comp. 8) are fairly regularly spaced and are made up of groups of White patches. The dark components Branchial hearts (Figs. 27, 29;

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