Abstract:We investigated the relationship between digestive function and ecological distribution for four related species of Gastropoda (Cerithidea rhizophorarum, Cerithidea cingulata, Batillaria multiformis, and Batillaria attramentaria) inhabiting the Tanaka River estuary (Mie Prefecture, Japan). We compared the digestive enzyme activities for four hard degradable carbohydrates, namely, cellulose, mannan, xylan, and laminarin. Among the investigated four species, Cerithidea rhizophorarum showed the highest cellulase, mannanase, xylanase, and laminarinase activities, and was also dominantly distributed in the estuary reed bed. The results of CN stable isotopic analysis suggested that this species assimilated organic matter derived from reeds. Hard degradable carbohydrates, including plant components derived from the reed bed or from dry land, accumulate in the sediment of estuaries. Estuarine benthic animals are assumed to consume these accumulated hard degradable carbohydrates, as well as microphytobenthos and particulate organic matter (including phytoplankton). Our present findings suggest that Cerithidea rhizophorarum is dominant in reed beds because it can more efficiently digest plant-derived carbohydrates than can Cerithidea cingulata, B. multiformis, and B. attramentaria. To the best of our knowledge, ours is the first study to demonstrate that the specific ecological distribution of related animal species with similar ecological traits can be explained by the efficiency of their digestive enzyme activity.
The photoconductive and semiconductive properties of some organic charge-transfer (CT) salts consisting of a pyrylium or thiopyrylium cation and a polycyanoacid anion were investigated in single crystals. The salts are poor semiconductors with a resistivity of 1010–1012 ohm·cm at room temperature, but show relatively large photoconduction when irradiated with monochromatized light in the interionic CT absorption band. There is a strong possibility that the photocarrier is intrinsic in nature, being generated spontaneously from the excited CT state. A weak ESR signal observed originally in these salts increased on the CT band or near IR excitation. From the relationship between the darkcarriers, photocarriers, paramagnetic species and the excited CT state, a mechanism of electrical conduction is proposed in which the carrier generation by the CT interaction and the carrier migration by trapping conduction are involved.
New organic charge transfer salts composed of an organic cation (pyrylium or thiopyrylium) and an organic anion (1,1,3,3-tetracyanopropenide or tricyanomethanide) were prepared. The absorption spectra were studied both in solution and in a solid. These salts have the charge transfer band in the visible region as a result of the electronic transition from the anion to the cation. The charge transfer bands of these salts in solution are sensitive to the nature of the solvent. The charge transfer band is observed in solvents with a low polarity; this band shifts toward a shorter wavelength in solvents with a high polarity. The increase in the polarity of the solvent causes a decrease in the apparent molar extinction coefficient. The charge transfer band in the solid shifts toward a shorter wavelength compared with that in the solution. In a single crystal, the polarized absorption spectrum shows a remarkable dichroism.
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