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991.
992.
The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely
exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T
LRR) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation
rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation
at 23 and 25°C. The mean T
LRR of epaulette and grey carpet sharks was inversely proportional to temperature. The T
LRR was similar between species at 23°C; however, grey carpet sharks had significantly reduced T
LRR at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly
earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation
rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation
rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during
re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control
animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant
reduction in the T
LRR occurring at higher temperatures. Epaulette sharks had a significantly greater T
LRR at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression. 相似文献
993.
There is a wealth of evidence showing that a moderate level of non-stop exercise improves the growth and feed conversion of
many active fishes. A diverse number of active fish are currently being farmed, and an optimal level of exercise may feasibly
improve the production efficiency of these species in intensive culture systems. Our experiments have set out to resolve the
growth benefits of juvenile New Zealand yellowtail kingfish (Seriola lalandi) enforced to swim in currents at various speeds over two temperatures (14.9 and 21.1°C). We also probed potential sources
of physiological efficiency in an attempt to resolve how growth is enhanced at a time of high energetic expenditure. Results
show that long-term exercise yields a 10% increase in growth but this occurs in surprisingly low flows (0.75 BL s−1) and only under favourable environmental temperatures (21.1°C). Experiments using a swim flume respirometer indicate that
exercise training has no effect on metabolic scope or critical swimming speeds but it does improve swimming efficiency (lower
gross costs of transport, GCOT). Such efficiency may potentially help reconcile the costs of growth and exercise within the
range of available metabolic energy (scope). With growth boosted in surprisingly low flows and elevated water temperatures
only, further investigations are required to understand the bioenergetics and partitioning of costs in the New Zealand yellowtail
kingfish. 相似文献
994.
This study is an attempt to go further in the comprehension of the effects of heavy fuel oil in the context of an accidental
oil spill at sea. It focuses on the link between morphological and functional impacts of realistic doses of the dissolved
fraction of a heavy fuel oil on fish gills. Juvenile turbot, Scophthalmus maximus were exposed to the dissolved fraction of a heavy fuel oil for 5 days and then placed 30 days in clean sea water for recovery.
During the contamination period, the concentration of the 16 US EPA priority poly-aromatic hydrocarbons showed small variations
around a mean value of 321.0 ± 9.1 ng l−1 (mean ± SEM). The contamination induced a 64% increase in hepatic cytochrome P 450 1A (Western blot analysis). Osmolality,
[Na+] and [Cl−] rapidly and significantly increased (by 14, 23 and 28% respectively) and slowly decreased to normal levels during the recovery
period. At the same time, branchial histology showed decreases in the number of mucocytes (by 30%) and of chloride cells (by
95%) in the interlamellar epithelium. Therefore, it is suggested that the osmotic imbalance observed after the 5 days of exposure
to the dissolved fraction of the heavy fuel oil is the consequence of the structural alteration of the gills i.e, the strong
reduction of ionocyte numbers. 相似文献
995.
Makiguchi Y Konno Y Konishi K Miyoshi K Sakashita T Nii H Nakao K Ueda H 《Fish physiology and biochemistry》2011,37(2):273-284
The movements of 28 adult chum salmon, Oncorhynchus keta (Walbaum) tagged with electromyogram (EMG) transmitters were tracked along the Toyohira river, Hokkaido, Japan, in October
of 2007 and 2008 to investigate and evaluate the upstream migratory behavior through the protection bed and fishway of ground
sills. The approach time of fish that ascended successfully through the protection bed and fishway was shorter than that of
unsuccessful fish. The unsuccessful fish were observed to swim in currents with high water velocity and shallow water depth
at swimming speeds that exceeded their critical swimming speed (U
crit) during the approach to these structures. In consequence, unsuccessful fish frequently alternated between burst and maximum
sustained speeds without ever ascending the fishway, and eventually became exhausted. It is important that fishway are constructed
to enable chum salmon to find a passage way easily, so that they can migrate upstream rapidly without wasting excessive energy. 相似文献
996.
Growth and ontogeny of digestive function were studied in pikeperch (Sander lucioperca) larvae weaned on artificial food at different ages. Three weaning treatments initiated respectively on day 9 (W9), day 15
(W15) or day 21 (W21) post-hatching (p.h.) were compared with a control group, fed Artemia nauplii from first feeding until the end of the rearing trial on day 36 p.h. The digestive enzyme activities and the ontogeny
of digestive structures were investigated using enzymatic assays and histological methods. Growth of pikeperch larvae was
significantly affected by precocious weaning. Pancreatic (trypsin and amylase) and intestinal (leucine-alanine peptidase,
leucine aminopeptidase N and alkaline phosphatase) enzyme activities were detected from hatching onwards, increased at the
moment of first feeding and then decreased. Pepsin secretion occurred at day 29 p. h. only, concurrently with the stomach
development and differentiation of gastric glands. In the early weaning group (W9) the maturation process of intestinal enterocytes
seems to be impaired and/or delayed and several signs of malnutrition were recorded. Except for alkaline phosphatase activity,
no differences in enzyme activities and development of digestive structures were observed among the control, W21, and W15
groups. Moreover, at the end of the experiment, no differences in proteolytic activities were observed among larvae from the
different treatments, indicating that, in surviving individuals, the digestive structures were properly developed and the
larvae had acquired an adult mode of digestion. Based on the artificial diet used, our results suggested that pikeperch larvae
can be weaned from day 15 p.h. without significant adverse effect on digestive capacities (except for alkaline phosphatase)
or development of digestive tract, while earlier weaning impaired the onset of the maturation processes of the digestive system,
both in terms of morphological structures and enzymatic activities. 相似文献
997.
The attracting effect of paralytic shell poison (PSP) on eight toxic snail species (Polinices didyma, Natica lineata, N. vitellus, Zeuxis sufflatus, Niotha clathrata, Oliva miniacea, O. mustelina, O. hirasei) and two non-toxic species (Pomacea canaliculata, Satsuma bairdi) was investigated. Eight toxic species were reported to contain tetrodotoxin, and three out of these contained minor PSP.
The minimum lethal dose of PSP in most toxic gastropods was estimated to be more than 150 MU PSP/20 g body weight, but in
non-toxic gastropods was less than 15 MU PSP/20 g body weight. After the attracting test, all toxic gastropods showed significant
positive linear relationship (Y=3.716X+0.363, r=0.8427) between comparative attracting variation and the toxicity reported. The relationship between PSP resistance ability
and the toxicity also had a positive correlation (Y=0.91X+210.090, r=0.6803). However, the non-toxic species showed a negative response. This indicates that PSP is an attractant for toxic snails. 相似文献
998.
To determine how stock abundance fluctuations of walleye pollock Theragra chalcogramma are related to variations in reproductive characteristics, the length at 50% maturity of the fish sampled off the Pacific
coast of northern Japan from 1990 to 1999 was examined. In both sexes, the fish density increased, and the body length of
age-3-5 fish decreased, but the condition factor and the age at 50% maturity showed no clear trend during this period. Male
length at 50% maturity decreased, while value for females showed no clear trend. In both sexes, significant negative correlations
were found between density index (combined age-3-5) and each body length at age-3-5. Significant positive correlations were
seen between each body length at age-3-5 and length at 50% maturity in males. Positive correlation between body length at
age-5 and length at 50% maturity was significant in females from 1990 to 1999, except for the samples in 1998. We suggest
that the fish density might affect the length at maturity in males and possibly also in females. 相似文献
999.
1000.
Mizuho Sakai Sei-Ichi Okumura Kanami Onuma Hiroaki Senbokuya Kunio Yamamori 《Fisheries Science》2007,73(1):77-80
The telomere sequence type (TTAGGG)n is known to be distributed in various phyla in the Animalia and in Mastigophora (Protista). However, the telomere type of
Porifera (sponges), a phylum comprising the lowest multicellular animals, has not been reported. In this study, we examined
the three sponge species Leucetta chagosensis, Halichondria japonica, and Halichondria panicea for the presence of the telomere type (TTAGGG)n by fluorescence in situ hybridization (FISH). The oligonucleotide probe (TTAGGG)7 clearly displayed signals on the interphase nuclei of all three sponges. In contrast, the (TTAGG)7 probe, which has one base fewer than (TTAGGG)7, did not display the signals. These results suggest that the telomeres of the three sponges consist of (TTAGGG)n, which is identical to the sequence type found in many higher multicellular animals and in Mastigophora. Additionally, this
is the first study to reveal a telomere sequence type for Porifera. Moreover, these results suggest that Porifera are phylogenetically
related to Mastigophora, and supports the general theory that Porifera evolved from Mastigophora. Further, this study strongly
suggests that the origin of the (TTAGGG)n telomere sequence is to be found in a common ancestor of either the Bilateria and Porifera, or the Protista. 相似文献