Effects of weaning age and diets on ontogeny of digestive activities and structures of pikeperch (<Emphasis Type="Italic">Sander lucioperca</Emphasis>) larvae     

Neila Hamza  Mohamed Mhetli  Patrick Kestemont 《Fish physiology and biochemistry》2007,33(2):121-133

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   

Paralytic shellfish poison as an attractant for toxic snails     

Pai-An Hwang  Tamao Noguchi  Deng-Fwu Hwang 《Fisheries Science》2007,73(1):202-207

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   

Density effects on length at maturity of walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> off the pacific coast of northern Japan in the 1990s     

Tomonori Hamatsu  Keizou Yabuki 《Fisheries Science》2007,73(1):87-97

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   

Isolation of purple nor-carotenoid, 2′, 3′-dihydroroserythrin,from crawfish <Emphasis Type="Italic">Procambarus clarkii</Emphasis>     

Takashi Maoka  Seiichi Ando 《Fisheries Science》2007,73(4):967-968

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Identification of a telomere sequence type in three sponge species (Porifera) by fluorescence <Emphasis Type="Italic">in situ</Emphasis> hybridization analysis     

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   

Influences of feeding frequency of extruded pellet and moist pellet on growth and body composition of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> in suboptimal water temperatures     

Kyoung-Duck Kim  Kyong-Min Kim  Yong Jin Kang 《Fisheries Science》2007,73(4):745-749

This study was carried out to investigate the influences of feeding frequency of extruded pellet and moist pellet on growth and body composition of juvenile flounder (initial mean weight 6.3 g) in sub optimal water temperatures. A 2 (diets: extruded pellet and moist pellet)×2 (feeding frequencies: two and three times daily)×2 (water temperatures: 12 and 17°C) factorial design with three replications was used. After 60 days of feeding, the feeding frequency did not significantly affect growth performance of fish. Weight gain, daily feed intake, feed efficiency and protein efficiency ratio were significantly (P<0.05) higher for fish reared at the higher water temperature. At the same water temperature, weight gain, feed efficiency, and protein efficiency ratio were significantly (P<0.05) higher for fish fed the extruded pellet than moist pellet. The results of this study indicate that feeding frequency of two times daily is sufficient for optimal growth of juvenile flounder when reared in suboptimal water temperatures, and an increase in water temperature from 12 to 17°C improved growth and feed efficiency.  相似文献   

Validation of multi-frequency inversion method by using dummy scatterers of zooplankton     

Bo-Kyu Hwang  Masahiko Furusawa  Masaki Ogata 《Fisheries Science》2007,73(2):250-262

ABSTRACT:   High- and multi-frequency acoustic measurement systems and the multi-frequency inversion (MFI) method have been used to measure spatial distributions and abundances of zooplankton by size. In this study, the calibration method for high- and multi-frequency systems was developed and the validation of MFI method was carried out by scatterer measurement. The standard sphere calibration method that has not been applied to such high- and multi-frequencies was applied to calibrate our high- and multi-frequency system, TAPS-6 (Tracor Acoustic Profiling System, BAE Systems). An optimum size of standard sphere of tungsten carbide of 1 mm radius was derived to have a small target strength variation for the six frequencies of TAPS-6, and the practicability and precision of the standard sphere calibration method was confirmed for those frequencies. A school or cluster of dummy scatterers of zooplankton with small tungsten carbide spheres were designed to validate the MFI method, and volume back-scattering strength values were measured by the multi-frequency system. By comparing the result of the inversion with their real composition, the features of the MFI method could be validated and examined.  相似文献   

Dietary value of benthic diatoms for post-larval abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> associated with feeding transitions     

Toshihiro Onitsuka  Tomohiko Kawamura  Satoshi Ohashi  Toyomitsu Horii  Yoshiro Watanabe 《Fisheries Science》2007,73(2):295-302

ABSTRACT:   The feeding behavior and growth of post-larval Haliotis diversicolor with initial shell lengths (SL) of approximately 500 μm (Exp. 1-1 and 1-2), 800 μm (Exp. 2), and 1200 μm (Exp. 3) were studied in a laboratory setting while they fed on four species of benthic diatom Achnanthes longipes , Cocconeis sublittoralis , Cylindrotheca closterium , and Navicula ramosissima . Exp. 1-1 and 1-2 revealed no marked differences in post-larval growth rates (mean 24–39 μm SL/day) among the diatom species. However, marked differences in growth rates among the species were revealed in Exp. 2 and 3. Three species, A. longipes , Co. sublittoralis, and Cy. closterium , produced faster growth (Exp. 2 mean 29–51 μm/day, Exp. 3 mean 36–44 μm/day) than N. ramosissima (Exp. 2 mean 18 μm/day, Exp. 3 mean 23 μm/day). Post-larvae fed N. ramosissima had lower digestion efficiency (42.8%) than those fed other diatom species (90.7–100%). Diatom extracellular substances appeared to be principally used from post-settlement to 800 μm SL, and diatom cell contents were required to produce rapid growth of larger post-larvae (>800 μm SL). It is likely that the availability of each diatom for post-larvae was affected by diatom morphology, attachment strength, frustule strength, and post-larval size.  相似文献   

DNA content of the cell nucleus in the macroalga <Emphasis Type="Italic">Porphyra yezoensis</Emphasis> (Rhodophyta)     

Kazuyo Matsuyama-Serisawa  Maki Yamamoto  Mariko Fujishita  Hirotoshi Endo  Yukihiko Serisawa  Satoshi Tabata  Shigeyuki Kawano  Naotsune Saga 《Fisheries Science》2007,73(3):738-740

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Increase of otolith Sr:Ca ratio related to metamorphosis and maturation in anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis>     

Hiromu Zenitani  Naoaki Kono  Youichi Tsukamoto  Noritaka Mochioka 《Fisheries Science》2007,73(6):1395-1397

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