The effects of temperature on the growth, survival and biomass of different families of juvenile Penaeus japonicus Bate

Variation in the growth, survival and change in total biomass (termed biomass increase) of different families of juvenile Penaeus japonicus was investigated over a range of temperatures in controlled laboratory experiments. In the first experiment, the effects of temperature on six families of juveniles were examined over a broad range of temperatures (24 to 30 degreesC). In the second experiment, the effects of temperature on six more families of juveniles were examined over a narrower range of temperatures (27.5 to 31.2 degreesC). Over the broad temperature range, mean growth and biomass increase were highest at 27 degreesC and mean survival was highest at 24 degreesC. Mean growth was lowest at 24 degreesC, whilst survival and biomass increase were lowest at 30 degreesC. However, there was a significant interaction between family and temperature, with some families tolerating a broader range of temperatures than others. As a result, the ranking of families in relation to growth, survival and biomass increase changed at each temperature. This effect was more pronounced for survival than for growth. Over the narrower range, temperature significantly affected growth, survival and biomass increase, but there was no significant interaction between family and temperature. Growth, survival and biomass increase were significantly lower at 31.2 than at 27.5 and 29.2 degreesC. These results suggest that if grow-out conditions for P. japonicus vary by more than a few degrees, interactions between family and temperature could affect the efficiency of selection. The results also suggest that the family x temperature interaction may have a more pronounced effect on survival than on growth. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

On the importance function in splitting simulation

The splitting method is a simulation technique for the estimation of very small probabilities. In this technique, the sample paths are split into multiple copies, at various stages in the simulation. Of vital importance to the efficiency of the method is the Importance Function (IF). This function governs the placement of the thresholds or surfaces at which the paths are split. We derive a characterisation of the optimal IF and show that for multi-dimensional models the natural choice for the IF is usually not optimal. We also show how nearly optimal splitting surfaces can be derived or simulated using reverse time analysis. Our numerical experiments illustrate that by using the optimal IF, one can obtain a significant improvement in simulation efficiency.

On the permutation behaviour of Dickson polynomials of the second kind

The known permutation behaviour of the Dickson polynomials of the second kind in characteristic 3 is expanded and simplified. (C) 2002 Elsevier Science (USA).

Lower Bounds on the State Complexity of Geometric Goppa Codes

We reinterpret the state space dimension equations for geometric Goppa codes. An easy consequence is that if deg G less than or equal to n-2/2 or deg G greater than or equal to n-2/2 + 2g then the state complexity of C-L(D, G) is equal to the Wolf bound. For deg G is an element of [n-1/2, n-3/2 + 2g], we use Clifford's theorem to give a simple lower bound on the state complexity of C-L(D, G). We then derive two further lower bounds on the state space dimensions of C-L(D, G) in terms of the gonality sequence of F/F-q. (The gonality sequence is known for many of the function fields of interest for defining geometric Goppa codes.) One of the gonality bounds uses previous results on the generalised weight hierarchy of C-L(D, G) and one follows in a straightforward way from first principles; often they are equal. For Hermitian codes both gonality bounds are equal to the DLP lower bound on state space dimensions. We conclude by using these results to calculate the DLP lower bound on state complexity for Hermitian codes.

Cleaner fish Labroides dimidiatus reduce 'temporary" parasitic corallanid isopods on the coral reef fish Hemigymnus melapterus

To determine if cleaners affect 'temporary' parasitic corallanid isopods (Argathona macronema) on fish, we used caged fish Hemigymnus meldpterus (Labridae) on 5 patch reefs on Lizard Island, Great Barrier Reef, and removed all cleaner fish Labroides dimidiatus (Labridae) from 3 of the reefs, In a short-term experiment, fish were sampled after 12 or 24 h, at dawn and sunset respectively, and in a long-term experiment they were sampled after 12 d at sunset. Isopod prevalence, abundance and size were measured. In the short-term experiment, on reefs without cleaners the prevalence of A. macronema was higher after 24 h than after 12 h while on reefs with cleaners, prevalence was low at all times, Although the abundance of A, macronema did not vary after 12 and 24 h, when combined over the 24 h, the effect of cleaners was significant with only 2 % of all the A. macronema found on reefs with cleaners. Cleaners had no effect on the size frequency distribution of A. macronema in the short-term experiment, most likely because fish had so few isopods on reef with cleaners. In the longer-term experiment, the effects of cleaners on isopod prevalence and abundance were less clear. Their effect on isopod size was, however, significant with smaller parasites on reefs without cleaners. The reduction of isopod prevalence and abundance by cleaner fish over a period of hours may explain why these A, macronema are rare on wild fish. Our findings support the idea that cleaning is beneficial to clients and has important implications for the control of parasites of fish farmed in cages,

The effect of the cleaner fish Labroides dimidiatus on the capsalid monogenean Benedenia lolo parasite of the labrid fish Hemigymnus melapterus

The cleaner fish Labroides dimidiatus affected the pigmented monogenean parasite Benedenia lolo on the fish Hemigymnus melapterus (Labridae) held in aquaria. The effect of cleaner fish varied with the size class of fish; only small fish [a posteriori size class < 11-5 cm standard length (L-S)] exposed to cleaner fish had fewer monogeneans compared with fish not exposed to cleaner fish. The abundance of monogeneans on large fish (a posteriori size class > 11-5 cut L-S) was not affected by cleaner fish. The size-frequency distributions of monogeneans on both size-classes of H. melapterus were affected by cleaner fish. Fish exposed to cleaner fish had fewer large (> 3 mm) and more small (< 1 mm) monogeneans than fish not exposed to cleaner fish, suggesting cleaner fish selectively removed larger monogeneans. This difference was more pronounced on large fish. In the absence of cleaner fish, small fish had almost as many monogeneans as large fish; they also had more small monogeneans than the large fish, suggesting small fish were more vulnerable to infection by monogeneans than larger fish. This suggests that the cleaner fish L. dimidiatus has the potential to control benedeniine monogeneans on captive fish and highlights the importance of taking into account fish size in studies of the effect of cleaner fish on ectoparasites. (C) 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.

Comparative influence of forest management and habitat structural factors on the abundances of hollow-nesting bird species in subtropical Australian eucalypt forest

We examined the impact of single-tree selective logging and fuel reduction bums on the abundance of hollow-nesting bird species at a regional scale in southeastern Queensland, Australia. Data were collected on species abundance and habitat structure of dry sclerophyll production forest at 36 sites with known logging and fire histories. Sixteen bird species were recorded with most being resident, territorial, obligate hollow nesters that used hollows that were either small (18 cm diameter). Species densities were typically low, but combinations of two forest management and three habitat structural variables influenced the abundances of eight bird species in different and sometimes conflicting ways. The results suggest that habitat tree management for biodiversity in production forests cannot depend upon habitat structural characteristics alone. Management histories appear to have independent influence (on some bird species) that are distinguishable from their impacts on habitat structure per se. Rather than managing to maximize species abundances to maintain biodiversity, we may be better off managing to avoid extinctions of populations by identifying thresholds of acceptable fluctuations in populations of not only hollow-nesting birds but other forest dependent wildlife relative to scientifically valid forest management and habitat structural surrogates.

Argyrodes: phylogeny, sociality and interspecific interactions - a report on the Argyrodes symposium, Badplaas 2001

Argyrodes Simon 1864 is a large, cosmopolitan theridiid genus whose members exhibit a wide range of foraging techniques which usually involve exploiting other spiders, either by using their webs, stealing their food, or preying on them directly. We held a symposium on this genus at the 15th International Congress of Arachnology, Badplaas, South Africa in order to obtain a clearer perspective on the relationship between the phylogeny of the genus and the different foraging techniques. We concluded that Argyrodes forms a monophyletic group within the Theridiidae, and that there are clear monophyletic clades within the genus (already identified as species groups) that appear to share behavioral characteristics. We found no clear indication that foraging behaviors such as kleptoparasitism (stealing food) evolved from araneophagy (eating spiders) or vice versa. However, it appears that species that specialize in either kleptoparasitism or araneophagy use additional techniques in comparison to species that readily use both foraging modes. During our examination of Argyrodes/host interactions we noted the importance of Nephila species as hosts of Argyrodes species around the world and the impact of Argyrodes on Nephila. We also noted the fluid nature of the relationship between Argyrodes and the spiders with which they interact. For example, an Argyrodes/host relationship can change to an Argyrodes/prey relationship, and the type of kleptoparasitic behavior employed by an Argyrodes can change when it changes host species. The importance of eating silk was also noted and identified as an area for further research. We concluded that more work involving international collaboration is needed to fully understand the phylogeny of the genus and the relationships between the different types of foraging behaviors.

The influence of cis/trans isomerism on the physical properties of a cyano-bridged dinuclear mixed valence complex

The cyano-bridged complexes cis-[L14CoIIINCFeII(CN)5]– and cis-[L14CoIIINCFeIII(CN)5] (L14= 6-methyl-1,4,8,11-tetraazacyclotetradecan-6-amine) are prepared and characterised spectroscopically, electrochemically and structurally: Na{cis-[L14CoIIINCFeII(CN)5]}·9H2O, monoclinic space group P21/c, a= 14.758(3), b= 10.496(1), c= 19.359(3) , = 92.00(2)°, Z= 4; cis-[L14CoIIINCFeIII(CN)5]·4H2O, orthorhombic space group P212121, a= 9.492(1), b= 14.709(2), c= 18.760(3) , Z= 4. In both complexes, the pendant amine is cis to the bridging cyanide ligand. An analysis of the metal-to-metal charge transfer (MMCT) transition in these systems with Hush theory has been carried out. This has revealed that the change in the configuration of the macrocycle both decreases the redox isomer energy difference (E1/2) and increases the reorganisational energy () of the cis-[L14CoIIINCFeII(CN)5]– complex with respect to the trans-[L14CoIIINCFeII(CN)5]– complex, the result being that both isomers display an MMCT transition of similar energy. The variation in redox isomer energy differences of the configurational isomers has been related to strain energy differences by molecular mechanics analysis of the [CoL14Cl]2+/+ precursor complexes.

Vitamin B12 stalls the 80 S ribosomal complex on the hepatitis C internal ribosome entry site

The effect of cyanocobalamin (CNCbl, vitamin 1312) on hepatitis C virus internal ribosome entry site (HCV IRES)-dependent initiation of translation was studied by ribosomal toeprinting and sucrose gradient centrifugation analysis. These results suggested that CNCbl did not inhibit HCV IRES-dependent translation by a competitive binding mechanism. CNCbl allowed 80 S elongation complex formation on the mRNA, but stalled the initiation at that point, effectively trapping the 80 S ribosomal complexes on the HCV TRES. CNCbl had no effect on cap-dependent mRNA, consistent with the known mRNA specificity of this translational inhibitor. To help elucidate the mechanism, comparative data were collected for the well-characterised translation inhibitors cycloheximide and 5'-guanylyl-imidophosphate, Although CNCbl stalled HCV IRES-dependent translation at approximately the same step in initiation as cycloheximide, the mechanisms of these two inhibitors are distinct. (C) 2002 Elsevier Science Ltd. All rights reserved.

Further observations on the Enenteridae Yamaguti, 1958 (Digenea, Lepocreadioidea) of the Indo-West Pacific region, including a new species from Western Australia

Measurements are given for all and full descriptions and illustrations for some of the following enenterid species: Enenterum aureum Linton, 1910 in Kyphosus bigibbus and K. sydneyanus? from Ningaloo Coral Reef, Western Australia, K. vaigiensis from off Heron Island, Queensland and K. vaigiensis from off Moorea, French Polynesia; E. mannarense Hafeezullah, 1980 in K. bigibbus and K. sydneyanus? from Ningaloo Coral Reef; E. elongatum Yamaguti, 1970 in K. vaigiensis from Heron Island, Queensland and K. bigibbus and K. sydneyanus? from Ningaloo Coral Reef; Koseiria alanwilliamsi sp. nov. in Kyphosus cornelii from off Kalbarri, Western Australia; Koseiria xishaense Gu et Shen, 1983 in K. vaigiensis from off Heron Island and K. bigibbus from off Palau, Micronesia; Proenenterum isocotylum Manter, 1954 in Aplodactylus arctidens from off Stanley, Tasmania; R ericotylum Manter, 1954 in A. arctidens from off Stanley; Cadenatella isuzumi Machida, 1993 from Kyphosus bigibbus and K. sydneyanus? from Ningaloo Coral Reef; Cadenatella pacifica (Yamaguti, 1970) from Kyphosus bigibbus from Ningaloo Coral Reef. Two recent cladistic studies of the Enenteridae are discussed and a further analysis has shown that Enenterum and Cadenatella are monophyletic, whilst Koseiria appears polyphyletic. The zoogeography and host-specificity of Kyphosus-inhabiting enenterids is discussed.