The Butterflies of Malacca.

THE author has already, in a brief communication (Journ. Linn. Soc. no. 67, vol. xiii. p. 115), given a preliminary notice of two new species of Lepidoptera from Malacca, and mentioned the donor and circumstances which have enabled him to draw up an extended list, with annexed remarks on geographical distribution. It is only necessary to add that the paper, with figures of the new and more remarkable forms, will subsequently appear in the Society's ‘Transactions’     

Nonadditive expression of lipid metabolism pathway-related genes in intestine of hybrids of Nile tilapia females (Oreochromis niloticus) and blue tilapia males (Oreochromis aureus)

Nonadditive expression contributes to heterosis in hybrids. In this study, the expression profiles of twelve lipid metabolism pathway-related genes were investigated in the intestine of Nile tilapia (Oreochromis niloticus) ♀?×?blue tilapia (Oreochromis aureus) ♂ hybrid. The expression of genes from the hybrid were assigned to nonadditive and additive expression pattern groups and compared with expression patterns from Nile tilapia and blue tilapia. In the intestine of the hybrid, apoA4B was expressed at intermediate levels, but apoB and MTP were assigned to ELD-B and ELD-N categories, respectively. The LPL and LRP1 showed transgressive up-regulation in the hybrid, but LDLR was assigned to the ELD-B category. For fatty acid uptake related genes, only FABP11a was categorized as nonadditive expression with transgressive up-regulation, while CD36 and FABP3 were categorized as additive expression in the intestine of the hybrid. Two genes in triacylglycerol metabolism, namely, FAS and DGAT2, showed transgressive up-regulation in the hybrid. Most of the genes analyzed in the present study showed nonadditive expression (8 in 12), and five genes showed transgressive up-regulation. These results indicated that the stimulation of lipid metabolism in the hybrid compared to that of its parents. The hyperactive expression of these genes in the hybrid may be associated with the growth and lipid usage vigor.

     

Effects of growth hormone transgenesis on metabolic rate, exercise performance and hypoxia tolerance in tilapia hybrids

Swimming respirometry was employed to compare inactive metabolic rate ( R _r), maximum metabolic rate ( R _max), resultant aerobic scope and maximum sustainable (critical) swimming speed ( U _crit), in growth hormone transgenic (GHT) and wild-type (W) tilapia Oreochromis sp. hybrids. Although the R _r of GHT tilapia was significantly (58%) higher than their W conspecifics, there were no significant differences in their net aerobic scope because GHT tilapia exhibited a compensatory increase in R _max that was equal to their net increase in R _r. As a consequence, the two groups had the same U _crit. The GHT and W tilapia also exhibited the same capacity to regulate oxygen uptake during progressive hypoxia, despite the fact that the GHT fish were defending a higher demand for O₂. The results indicate that ectopic expression of GH raises metabolic rate in tilapia, but the fish compensate for this metabolic load and preserve such physiological determinants of fitness as aerobic scope, swimming performance and tolerance of hypoxia.     

Transgenic tilapia and the tilapia genome

The tilapia fish (Oreochromis niloticus) has an important place in the aquaculture of the developing world. It is also a very useful laboratory animal, and readily lends itself to the transgenic technology. Through the use of reporter genes, a range of potential gene promoters have been tested in tilapia, both through transient and stable expression of the reporter construct. Using the transgenic technology, growth enhanced lines of tilapia have been produced. These fish have no abnormalities and offer a considerable growth advantage for future exploitation. It is however crucial that transgenic fish, to be exploited in aquaculture, be sterile, and various methods of achieving sterility are considered. These include triploidy, gene knock out of crucial hormone encoding genes via homologous recombination, and knock down of the function of the same genes via ribozyme or antisense technologies.Transgenic tilapia also offer the potential for exploitation as biofactories in the production of valuable pharmaceutical products, and this is also discussed.     

The effect of temperature on juvenile Mozambique tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) exposed to full-strength and hypersaline seawater

The effects of temperature on the salinity tolerance of Mozambique-Wami tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) were investigated by transferring 35 g/l, 25 degrees C-acclimated fish to 35, 43, 51 or 60 g/l salinity at 15, 25 or 35 degrees C for 24 h, and by assaying gill tissue for branchial Na(+), K(+)-ATPase activity at the three temperatures after acclimating the fish to 15, 25 or 35 degrees C for 2 weeks. Tilapia survived all salinities at 25 and 35 degrees C; however, at 15 degrees C, mortality was 85.7% and 100% in the 51 g/l and 60 g/l groups, respectively. There was a significant interaction between temperature and salinity, as plasma osmolality, [Na(+)] and [Cl(-)] were significantly increased at 51 and 60 g/l salinity in 35 degrees C water (P<0.001). Additionally, muscle water content was significantly reduced at 43 g/l, 15 degrees C relative to pre-transfer values (P<0.001). Branchial Na(+), K(+)-ATPase activity was reduced at 15 degrees C regardless of acclimation temperature, and 25 degrees C-acclimated gill tissue did not show an increase in activity when assayed at 35 degrees C. Results indicate that the effects of a combined temperature-salinity transfer on plasma osmolality and ion concentrations, as well as muscle water content, are greater than when either challenge is given alone. Additionally, branchial Na(+), K(+)-ATPase activity is altered when assayed at varying temperatures; in the case of 15 degrees C, regardless of acclimation temperature. Our enzyme activity data may indicate the presence of a high temperature isoform of branchial Na(+), K(+)-ATPase enzyme.     

罗非鱼对水质的影响

鱼类是影响水库等水质的重要因素,以我国南方主要养殖鱼类之一的罗非鱼为对象,通过广东大镜山水库原位围隔实验,研究了鱼类对水质的影响。结果表明,与对照组相比罗非鱼围隔中总氮,总磷和叶绿素a浓度分别升高了42%,129%和347%。罗非鱼的排泄增加了水体营养负荷,为浮游植物生长提供大量的营养盐,引起浮游植物生物量增加,水体透明度降低。罗非鱼通过营养盐释放所产生的上行效应明显大于由其牧食导致的下行效应。     

The origin of Phoxinus eos-neogaeus unisexual hybrids

Phoxinus eos-neogaeus unisexual hybrids (Cyprinidae, Pisces) are among the few vertebrate taxa known to reproduce clonally by gynogenesis. These taxa have a broad distribution in North America, mostly located in regions previously covered by the last Pleistocene ice sheet. To assess whether asexual hybrids dispersed from glacial refuges at the end of the Pleistocene or they originated from current hybridization events, genetic diversity of mitochondrial DNA (mtDNA) sequences and microsatellite loci was determined in populations from 16 different sites in the Mississippi-Missouri River (Nebraska and Montana), Rainy River-Hudson Bay (Minnesota), and St Lawrence River (Quebec) drainages. The maternal species (P. neogaeus) occurred in Minnesota and Nebraska but was absent from Montana sites and was restricted to only two of 11 lakes sampled in Quebec, although hybrids were present at all sites. The genetic survey revealed a total of 49 clones, originating from 14 hybridization events. Several of the lineages were characterized by mtDNA haplotypes not detected in the maternal ancestor. Lineages as well as clones frequently displayed a large geographical distribution at a regional scale. Dating of hybridization events suggested a relatively recent origin (<50,000 years ago) from the Mississippi glacial refuge, even in regions not covered by the last Pleistocene glacier. Altogether, these results indicate P. eos-neogaeus hybrids are not the result of current hybridization events, but display a pattern predicted by postglacial dispersal. Our findings have considerable implications for the nature of selection processes affecting the diversity of these asexual taxa and their coexistence with sexual ancestors.     

The properties of tilapia sperm and its cryopreservation*

The specific differences between the testis, milt and sperm of six species of tilapia including Oreochromis aureus, O. mossambicus, O. niloticus, Tilapia zillii, O. nilolicus×O. aureus hybrid and red tilapia, Oreochromis sp., were studied. The shape of testis is tubular; the gonadosomatic index varied from 0.07 to 2.71. The pH values of individual milts ranged from 6.2 to 8.2 and the osmolarity from 240 to 380 mOsmol kg^?1. The quantity of milt obtained by stripping averaged only about 0.3 ml, and only in the O. niloticus×O. aureus hybrid did it exceed 3 ml. Sperm motility graded from weak to moderate was determined for the stripped tilapia milt. Sperm concentrations ranged from 7.70 × 10⁸ sperms ml^?1 in T. zillii to 2.74 × 10¹⁰ sperms ml^?1 in O. mossambicus. Tilapia sperm was active in various salinity ranges such as 0–5‰ for O. niloticus, and 0–15‰ for O. mossambicus and T. zillii. Extender containing 15% milk and 5% methanol was used to prepare milt mixture before cooling rapidly to ?35° C and then at 5° C min^?1 to ?75° C for storage in liquid nitrogen (– 196° C). Fertility tests on frozen tilapia milt resulted in a fertilization rate of 72.7% (v. control 85.7%) for the 22-day frozen milt of the O. nilolicus×O. aureus hybrid used to fertilize the eggs of O. honorum, and 93.4% (v. control 90%) for the 304-day frozen sperm of red tilapia used to fertilize eggs of red tilapia.