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11.
The population dynamics of zooxanthellae living in the mantle of a giant clam, Tridacna derasa, was studied. The giant clams with shell lengths of 5 to 6 cm which had been reared in the Palau Mariculture Demonstration
Center, in the Republic of Palau, were transferred to aquaria on deck of the R.V. “Sohgen-maru” and kept in running sea water
at 29 to 30 °C. Two clams were removed from the aquaria, and zooxanthellae in the mantle were isolated every 2 h for 24 h.
Numbers of the zooxanthellae in or not in the cell division stage were counted for calculations of the zooxanthellae population
in the mantle and their mitotic index (MI). The MI increased after sunset and reached the maximum values of 6.1 to 11.5% at
03:00 to 05:00 hrs. The specific growth rate, μ, estimated from the MI was 0.083 to 0.14 d−1. Five clams were kept in each of 2 Plexiglas containers in the aquarium for collection of the discharged feces every 3 to
4 h. The discharged zooxanthellae in the feces were counted. The zooxanthellae discharged in 24 h were 0.38 to 1.46% of the
total zooxanthella population in the mantle, and 2.7 to 16.9% of the newly formed zooxanthella population in a day. Increase
of zooxanthella population in the mantle was estimated from clam shell growth rate and from the correlation between zooxanthella
population and clam shell size. Daily increase of zooxanthella population in the mantle was estimated to be approximately
7.6 to 19% of the newly formed zooxanthella population. Therefore, the sum of zooxanthellae populations accounting for daily
increase in the mantle and discharge in the feces was 11 to 36% of the newly formed population. About 64 to 89% of the newly
formed cells were missing; some of these may have been digested by the clam.
Received: 14 July 1996 / Accepted: 19 August 1996 相似文献
12.
K. Miyazawa T. Noguchi J. Maruyama J. K. Jeon M. Otsuka K. Hashimoto 《Marine Biology》1985,90(1):61-64
Two starfishes, togemomijigai Astropecten polyacanthus and momijigai A. scoparius were collected from the Seto Inland Sea in October 1983 through November 1984, and assayed for toxicity by the standard method for tetrodotoxin (TTX). Most of the 54 A. polyacanthus specimens assayed were toxic, with the highest toxicity score being 520 mouse units (MU) g-1. All seven A. scoparius were toxic, with the highest score being 46 MU g-1. The toxin from A. polyacanthus was purified by a method which consisted mainly of activated charcoal treatment, and chromatography on CM-Sephadex C-25 and Bio-Rex 70 columns. The purified starfish toxin showed a specific toxicity of 4 700 MU mg-1, a value which was almost comparable to that of authentic TTX. From the thin-layer chromatographic and electrophoretic behavior, along with 1H-NMR spectrum, A. polyacanthus toxin was identified as TTX. 相似文献
13.
Teruhiko Takahara Yukihiro Kohmatsu Atsushi Maruyama Ryohei Yamaoka 《Behavioral ecology and sociobiology》2008,63(2):235-240
When predator chemical cues are present, low activity of prey is a commonly seen defensive behavior. However, few studies
have explored the functional implications of the defensive behaviors and, thus, elucidated the possible linkages between behavioral
responses and its consequences. In this study, we experimentally investigated how behavioral responses of Hyla japonica tadpoles to predator chemical cues affect vulnerability to a dragonfly nymph Anax parthenope julius. The frequency of tadpoles attacked by dragonfly nymphs was lower with chemical cues of predator was present than without
chemical cues, and most of attacks occurred when tadpoles were mobile. When tadpoles were exposed to chemical cues, on the
other hand, their swimming speed was quicker and swimming distance was longer, respectively, and the rates of being approached
of the swimming tadpoles by dragonfly nymph was lower than those not exposed to chemical cues. We found that the tadpoles
are induced by predator chemical cues not only to generally lower activity but also to swim in bursts as additional behavior
and that the suite of their behavioral responses reduce the vulnerability against dragonfly nymph. Tadpoles can receive information
about the predation risks by chemical cues and adjust their defensive behavior accordingly. 相似文献
14.
Montastraea annularis, M. faveolata, and M.␣franksi are three recently separated species that together dominate reefs of the tropical western Atlantic. Despite morphological,
life-history, ecological and genetic differences, the legitimacy of their status as separate species has been questioned.
This controversy stems from both the scarcity of unambiguous, diagnostic differences among them, and from the possibility
of extensive hybridization associated with their approximately synchronous reproduction in sympatry. Here we report on fertilization
trials and the timing of spawning, both of which suggest that the potential for hybridization may be limited. Crosses between
M. faveolata (the most genetically distinctive taxon) and the other two species were largely unsuccessful, as were selfed matings for
all three species. M. annularis and M. franksi showed no evidence of fertilization barriers, but the timing of spawning typically differed between them by 1 to 2 h. We
also found that spawning times in the field of M. annularis and M. faveolata were non-overlapping in 1995, and that the timing of spawning in M. annularis could be experimentally shifted forward by simulating earlier than natural sunsets. These findings from Panamá and Honduras,
particularly given their consistency with comparable observations and experiments elsewhere, provide evidence of reproductive
isolation and support the separate species status of these three taxa. Some hybridization may occur under natural conditions
at these sites, particularly between M. annularis and M.␣franksi. Rampant genetic interchange among these taxa in Central America seems unlikely, however, in the light of the concordant
associations between morphology, reproductive biology and other characters which are observed.
Received: 22 July 1996 / Accepted: 2 October 1996 相似文献
15.
Kayama M Quoreshi AM Kitaoka S Kitahashi Y Sakamoto Y Maruyama Y Kitao M Koike T 《Environmental pollution (Barking, Essex : 1987)》2003,124(1):127-137
In northern Japan, the growth of Picea abies Karst., and Picea glehnii Masters, which have been planted along the highways, is often suppressed due to several environmental stresses. To examine the adverse effects of deicing salt, the primary source of stress,we measured needle life span, photosynthetic capacity, and water potential and transpiration rate of the two spruce species at a site with damaged trees, near the roadside and a site with healthy trees, located far from the highway. Results from the analysis showed large amounts of sodium and chlorine in the soil and snow at the damaged site. These elements had accumulated in the needles of the spruce. Moreover, physiological traits of the spruce, at the damaged site were also affected. Therefore, we concluded that poor physiological traits might be attributed to an accumulation of deicing salt in the needles, resulting in the suppression of tree growth. 相似文献
16.
Adaptation of solitary corals, Fungia repanda and F. echinata, and their zooxanthellae to low light and ultraviolet light B (UV-B) was studied with respect to changes in their protein contents, photosynthetic pigment contents and the photosynthesis-irradiance (P-I) curves. The corals were collected from 1 to 50 m depths in the Republic of Belau (Paulau) in 1990 and 1991. The chlorophyll a content in a unit surface area of the coral did not change significantly with the depth of the habitat, whereas cellular chlorophyll a in the algae increased with the depth. Zooxanthellae density and protein content in a unit surface area of Fungia spp. decreased with the depth. Photosynthetic parameters normalized by a unit surface area of the Fungia spp., maximum gross photosynthetic rate (P
gmax area-1) and dark respiration rate (R area-1), were negatively correlated with the depth, while initial slope of the P-I curve () did not show significant correlation with the depth. Compensation light intensity (Ic) decreased with the depth. In isolated zooxanthellae, P
max chl a
-1, and R chl a
-1 decreased with the depth, while chl a was constant. P
gmax cell-1 and R cell-1 did not change significantly but cell increased with the depth. Ic decreased with the depth as in the intact corals. Reduction of protein content in a unit area of the coral from deeper habitat implies decrease of host animal tissues. Reduction of Ic can be explained by decrease of R area-1, which may be due to the diminution of animal tissues. The photoadaptational response to low light intensity of intact Fungia spp. was found to be a combination of the photoadaptation of symbiotic algae and the decrease of host animal tissue. In order to study their adaptation to ultraviolet (UV) radiation, P-I curves of Fungia spp. and isolated zooxanthellae were analyzed before and after UV-B irradiation. 1 h UV-B irradiation showed no effect on the photosynthetic rate of the shallow water (1 m) corals, while it inhibited the photosynthesis of the deep water (30 m) corals and zooxanthellae isolated from both shallow and deep water corals. These results indicate that the host, Fungia spp., in shallow water have protective mechanism for intense UV-B in their habitat. These photoadaptational mechanisms seem to allow the Fungia spp. to have wide vertical distribution where light intensity spans more than two orders of magnitude. 相似文献
17.
The effects of UV-A and UV-B radiation on photosynthesis of zooxanthellae within the siphonal mantle of the giant clam, Tridacna crocea, and in isolation were studied. While UV-B irradiation (2.4 W m−2, 20 min) completely suppressed photosynthesis of the isolated zooxanthellae, it had little effect on their photosynthetic
ability if they were irradiated while within the siphonal mantle of the host tissue. Chemical analysis of the siphonal mantle
of T. crocea showed the presence of significant amounts of mycosporine-like amino acids (MAAs), which absorb UV-A and -B light. However,
no MAA was detected in the isolated zooxanthellae. MAAs were concentrated in the siphonal mantle and kidney tissues in comparison
with other tissues. In the siphonal mantle, MAA concentrations were the highest in the outermost surface layer where most
of the zooxanthella cells resided. This indicates that the zooxanthellae are protected from UV radiation by a screen of concentrated
MAAs in the host clam. Aside from T. crocea, significant amounts of MAAs were found not only in other zooxanthellate clams, such as T. derasa, Hippopus hippopus, Colculum cardissa and Fragum unedo, but also in a closely related azooxanthellate clam, Vasticardium subrugosum. On the other hand, no MAA was detected in any of the zooxanthellae from these zooxanthellate clams. No MAA was detected
in the tissues of a deep-sea bivalve, Calyptogena soyoae. Although MAAs seem to block strong UV radiation in the shallow-water clam, they are probably not essential for the clam's
life in the dark. MAAs in shallow-water clams may be derived from food and accumulated in their tissues, especially in the
siphonal mantle and kidney.
Received: 29 November 1996 / Accepted: 13 January 1997 相似文献
18.
Sarmah Purbashree Ishiguro Takeshi Maruyama Kenji Xue Tianle Yamawaki Atsushi Katsumi Takeshi Takai Atsushi Omine Kiyoshi Doi Yoichi 《Journal of Material Cycles and Waste Management》2022,24(6):2183-2200
Journal of Material Cycles and Waste Management - Mechanical properties and slope stability of inert waste landfills under seismic condition were studied with three different approaches: in-situ... 相似文献