Diurnal migration

Although some species of cestodes (e.g. Hymenolepis diminuta, p. 236) undergo diurnal migrations within the intestine - and therefore their suckers may not always be in a state of sustained contraction - others (e.g. Echinococcus granulosus) apparently remain in the same place and appear to be able to maintain contraction. How this is achieved physiologically is not known, but it has been speculated that this may operate through a catch muscle mechanism (as in lamellibranchs) or by the involvement of special stretch receptors (796). 

As indicated above, this long-term migratory pattern is overlaid by a diurnal migration. That this latter pattern is related to feeding is... 

The concept that the scolex of adult cestodes is generally non-penetrative has been shown not to hold for species such as Echinococcus granulosus and E. multilocularis, where the scolex penetrates the crypts of Lieberkiihn and, occasionally, even the lamina propria (Fig. 9.5) often resulting in a complete breakdown of the mucosal epithelium. These species can be regarded as both tissue and lumenal parasites. That the scolex contact is close is reflected in the fact that anti-Echinococcus antibodies appear in dog sera 14 days post-infection (p.i.) (368). It is likely, however, that in many cestodes the scolex contact is more superficial and breakdown of the mucosa may not occur, especially in those species which undergo diurnal migration - see Chapter 9. 

Fig. 6.18 Acoustic backscatter for 24 hours around 19° N, 67° E indicating diurnal migration of organisms (mostly myctophids). Reproduced from Morrison etal. (1999) (see Color Plate 4).

Hydrocarbon vapor migration within the carbon canister is a significant factoi during the real time diurnal test procedure. The phenomenon occurs after the canister has been partially charged with fuel vapors. Initially the hydrocarbons will reside primarily in the activated carbon that is closest to the fuel vapor source. Over time, the hydrocarbons will diffuse to areas in the carbon bed with lower HC concentration. Premature break through caused by vapor migration for twc different canisters is shown in Fig. 17. The canister with the L/D ratio of 5.0 shows substantially lower bleed emissions than the canister with an L/D ratio of 3.0. 

Table 32.12 Time Required to Transport Selected Radionuclides Added into Marine Waters at Surface out of the Upper Mixed Layer by Biological Transport (Processes include diurnal vertical migration, fecal pellets, and sinking of dead matter.)...

Zusser, S.G. (1971). Diurnal Vertical Migrations of Fish (In Russian). Pishchevaya Promyshlennost, Moscow, 224 pp. 

The microphytobenthos consist of an assemblage of benthic diatoms (principally pen-nate in shape) that typically migrate vertically in the sediments over a diurnal period (Serodio et ah, 1998). Enhanced turbidity in shallow regions from resuspension events can limit light penetration thus, the most effective time for primary production occurs in intertidal sand and mud flats during daytime exposure periods (Guarini et ah, 2000,... 

MIGRATION IN THE HYMENOLEPIDIDAE The migratory behaviour is even more complex in the case of the Hymenolepididae, in which the phenomenon has been extensively studied, especially in the case of Hymenolepis diminuta, by the fact that two interacting patterns of migration take place (20). One is an age-dependent forward migration and the other a diurnal (circadian, diel) migration. Since it is... 

The hydrocarbon gases migrating through soil pore spaces are not dissipated and diluted to the same extent as those in the atmosphere. There are, however, problems posed by the very low levels of hydrocarbon gases and by the diurnal breathing of many near-surface soils. In order to overcome these problems, soil-gas techniques which integrate the hydrocarbon signal were introduced by Pirson (1946), Horvitz (1950), Kartsev et al. (1959), Karim (1964), Heemstra et al. (1979), Hickey (1983), Hickey et al. (1983) and Klusman and Voorhees (1983). 

First, zooplankton may adapt or alter their seasonal or spatial distribution to reduce the UV-stress. Seasonal life cycle adaptations to avoid periods of peak solar intensity may very well be a strategy for UV-exposed and sensitive organisms, yet this is not explicitly demonstrated. Diurnal vertical migration is, however, commonly accredited to direct UVR [8,9]. A critical question is whether organisms have a sufficient spectral resolution to separate UVR from, for example, blue light. This may be important to respond to an increased UVR under constant PAR. Such behavioral responses clearly are important evolutionary traits for swimming animals, and could affect both productivity and trophic interactions the topic will be fully covered in another chapter, and will thus only briefly be touched upon here to illustrate some ecological implications. 

Small stream invertebrates have also been noted to respond negatively to UVR in nature. Blackfly larvae appear to exhibit a diurnal emigration, or migration out of UV-exposed stream channels, during periods of peak irradiance but return to UV-exposed regions as irradiance levels decrease [45]. In streams that were experimentally shielded from UVR exposure, however, larvae remained in the stream channels throughout the day. Larvae were allowed to move... 

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