Copepods associated with reef corals: a comparison between the Atlantic and the Pacific

Endoparasitic copepods are very numerous in Indo-West Pacific corals. In West Indian corals they were thought to be absent, but recent studies have shown that a varied endoparasitic copepod fauna exists as well. Striking is the taxonomic composition of the coral-inhabiting copepods:In the Indo-West Pacific Lichomolgidae and Xarifiidae are the dominant families, both are absent in the West Indies. On the other hand, Corallovexiidae and Asterocheridae dominate in the West Indies; the former family is absent and the latter is apparently rare and not very diversified in the Indo-West Pacific.     

Influence of aerial dispersal on persistence and spread of pesticide-resistant Metaseiulus occidentalis in California almond orchards

Aerial dispersal of the phytoseiid Metaseiulus occidentalis (Nesbitt) was evaluated as a component in managing pesticide-resistant populations established in California almond orchards. Peak dispersal occurred in late July and early August during 1982 and 1983. Most predators (and spider mites) left the orchards on the prevailing winds from the northwest. Within the orchard, the prevailing winds had less influence, and dispersal was usually random. Both spider mites and predators dispersed randomly with regard to height from the almond trees, but data obtained during one 24-h interval suggest they do not disperse randomly throughout the day. Most aerial movements occurred between 16–22 h when relative humidity and wind speeds increased and temperatures decreased. Spider mites and predators were trapped on panels located 200 m from the orchard. A survey of carbaryl resistance levels in M. occidentalis collected from almond orchards surrounding the release sites indicates that carbaryl-resistant M. occidentalis dispersed at least 800 m between 1981–83. However, growers wishing to use the resistant strains should release them in their orchards as natural dispersal appears to be too slow. Migration of native M. occidentalis into the release sites appeared to be sufficiently rare that dilution of carbaryl-resistant populations was minimal during a 2–4 year period.

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Résumé La dispersion aérienne du phytoseïdae, M. occidentalis (Nesbitt), a été estimée comme élément de la lutte contre les populations résistantes aux insecticides établies dans les vergers de Californie. La dispersion maximale s'est produite fin juillet et début a oût en 1982 et 1983. La plupart des prédateurs (et des acariens) quittent les vergers avec les vents dominants du nordouest. Dans le verger, les vents dominants sont moins importants et la dispersion est généralement au hasard. Tant les acariens que les prédateurs se dispersaient au hasard par rapport à la taille des amandiers, mais les relevés sur 24 heures laissent supposer qu'il n'y a pas une distribution aléatoire pendant la journée. La plupart des mouvements aériens se produisirent entre 16 et 22 heures quand HR et vitesse du vent augmentaient et température diminuait. Les acariens et prédateurs ont été piégés sur des panneaux à 200 m du verger.

     

Philomena oncorhynchi: Effect of hormones on maturation in anadromous sockeye, Oncorhynchus nerka

Adult sockeye salmon, Oncorhynchus nerka (Walbaum), treated with salmon pituitary extract in July survived for up to 47 days and developed nuptial colours in both male and female fish during this period, whereas no such characteristics appeared in untreated control fish. Furthermore, results showed that 20 of 50 adult female Philomena oncorhynchi recovered from the 15 treated fish contained fully developed tailed larvae in the uterus as compared with only one of 44 female P. oncorhynchi from 31 untreated control fish. None of 51 worms from 13 stilboestrol treated adult sockeye showed development in utero beyond an elongated embryo, nor did the host fish develop nuptial colours. P. oncorhynchi and its immature sockeye host (approx. 1 year prior to spawning) remained unaffected by any of three separate hormone treatment experiments using injection of salmon pituitary extract, injection of 17-β-estradiol, and stilboestrol mixed in the food.     

Direct and indirect evidence for polypeptide absorption by the teleost gastrointestinal tract

The ability of the gastrointestinal tract of chinook salmon, Oncorhynchus tshawytscha , to absorb polypeptides in vivo was investigated by reference to the appearance of orally administered adrenocorticotropic hormone (ACTH) within the blood of fish previously treated with dexamethasone (3μg g^−l body weight) in order to suppress endogenous ACTH secretion. Further, since cortisol presence within plasma is dependent upon the availability of ACTH, dexamethasone blockade of endogenous ACTH secretion, in conjunction with subsequent measurements of plasma cortisol levels, provides a means by which biological patency of absorbed exogenous ACTH may be demonstrated. Levels of ACTH and cortisol in plasma of dexamethasone-treated salmon were therefore measured for a period of 360 min immediately following oral intubation of ACTH (15μg g⁻¹ body weight). Peak plasma presence of ACTH-like immunoreactivity (676.6 ± 33.6 pg ml⁻¹ plasma) and cortisol (227.1 ± 29.0 ng ml⁻¹ plasma) were recorded 120 min after ACTH administration. Results from the experimental groups were compared to those of 15 control treatments. Since administration of ACTH to chinook salmon elicited a consistent and significant elevation in not only plasma ACTH but also cortisol presence, it is contended that the salmonid gut expresses an ability to absorb polypeptides of dietary origin. The significance of these findings with respect to the oral administration of biologically active peptides and proteins to fish of importance to aquaculture is discussed.     

Migratory and reproductive behaviour of female adult Atlantic salmon, Salmo salar L., in a spawning stream

Migration and spawning behaviour of eight Atlantic salmon adult females were analysed by radio-tracking in relation to the degree of sexual maturity in a spawning tributary of the R. Sélune. Six of them were grilse and four of them were ripe. All the fish migrated upstream until reaching their spawning site at a distance of 4–12 km from the trap. The daily migration rate up to this site was inversely correlated with the length of the female. Spawning occurred in all fish at the same time when the water temperature increased dramatically. Spawning lasted 1–10 days according to the fish. After spawning, females quickly moved downstream only small distances and then stayed in approximately the same location until death. This study concluded that ripeness did not influence behaviour on the spawning migration and describes certain characteristics of the reproductive phase in a spawning tributary.     

The quantitative relationship of lethality between extracellular protease and extracellular haemolysin of Aeromonas salmonicida in Atlantic salmon (Salmo salar L.)

An additive relationship of lethality between purified protease and haemolysin of the extracellular products (ECP) of Aeromonas salmonicida was demonstrated by i.p. injection in Atlantic salmon (Salmo salar L.). The lethal toxicity of the combinations of protease and haemolysin follow a linear regression line y = -54.54x + 2400. The LD50 of protease and haemolysin when injected separately was 2400 ng/g fish and 44 ng protein/g fish, respectively.     

Biogeography of milkweed butterflies (Nymphalidae: Danainae) and mimetic patterns on tropical Paciflc archipelagos

Distributions of danaine butterfly species and associated mimetic patterns were compared among fifteen archipelagos of the tropical Pacific Ocean, and within five major archipelagos (the Bismarcks, Fiji, East and West Solomon Islands, and Vanuatu). Using both simple and stepwise linear regression analysis, variation in the total number of danaine species and number of mimetic patterns was assessed with respect to island size, isolation and elevation. Relative to interarchipelago distributions, the distribution of danaine species and number of mimetic patterns on islands within archipelagos exhibited less dependence upon interisland distance and island area. Geographical features influencing the number of mimetic patterns were similar to those of danaines as a whole. Analysis of residuals from stepwise linear regression suggested that factors influencing danaine distributions were different from those for non-danaine butterflies. This result is consistent with the hypothesis of enhancement of danaine species establishment through Müllerian mimicry, although other factors such as host plant availability and similar habitat use may also be important.     

Tail-to-tail orientation of the Atlantic salmon alpha- and beta-globin genes

We report the cloning of a cDNA and two corresponding -globin genes of the Atlantic salmon (Salmo salar L.) as well as two genes for -globins. Nucleotide sequence analysis of the cDNA shows that the predicted -globin peptide comprises 148 amino acids with a calculated molecular mass of 16,127 Da and an overall amino acid similarity of 40–50% to higher vertebrates and 60–90% to fish sequences. The study of the genomic organization of - and -globin genes shows that, as is the case in Xenopus, the salmon genes are adjacent. Two sets of linked - and -globin genes were isolated and restriction-enzyme polymorphisms indicate that they belong to two distinct loci, possibly as a result of the salmon tetraploidy. In each locus the - and -globin genes are oriented 3 to 3 relative to each other with the RNA coding sequences located on opposite DNA strands. This is the first evidence for this type of arrangement found for globin genes. Moreover, while the linkage found in salmon and Xenopus supports the hypothesis of an initial tandem duplication of a globin ancestor gene, our results raise the question of the actual original orientation of the duplicated genes. Correspondence to: F. Gannon     

Variation in digestive performance between geographically disjunct populations of Atlantic salmon: countergradient in passage time and digestion rate

European Atlantic salmon (Salmo salar) populations inhabit rivers from northern Portugal to northern Norway across a wide spectrum of environmental variability. To address whether single physical factors might lead to genetic divergence of isolated populations, we compared the digestive performances total digestibility, relative nitrogen digestibility, passage time, and digestion rate (g dry matter · h^–1) — of northern (Scotland) and southern (Asturias, northern Spain) populations at three temperature regimes (5, 12, and 20° C). Total dry matter digestibilities increased directly with temperature but were similar for both populations at each of the three trials. Relative nitrogen digestibility did not differ between populations nor among temperature regimes. In contrast, passage time was significantly longer for low-than for high-latitude fish at both 5 and 20° C. When the percentage of food digested and the passage time were integrated as digestion rates (food digested per unit time), a significant population × temperature interaction consistent with a genotype × environment interaction was detected in addition to the population and temperature effects. This implies that not only is the digestive performance of the high-latitude population higher throughout the range of temperatures examined, but moreover the difference is reinforced at high temperatures, where the digestion rate of high-latitude fish was 1.6 times greater. Taken together, these two results provide preliminary evidence for countergradient variation in digestive rates of salmonids in response to variation in growth opportunity. The data support our previous work on the same two populations showing differences in growth rates, and underlie one of the possible mechnisms leading to more rapid growth of the high-latitude fish when both populations are reared in a common environment.     

Specific DNA probes for the identification of the fish pathogen,Renibacterium salmoninarum

To obtain specific DNA probes for the identification of the fish pathogen, Renibacterium salmoninarum, a discriminatory recombinant DNA library was constructed using selective fragments of the bacterial genome. Three renibacterial clones, pMAM29, pMAM46 and pMAM77, containing 149, 73, and 154 bp respectively, were isolated and characterized. The specificity of the probes was confirmed by dot-blot and Southern hybridization analyses. Bacterial hybridization experiments revealed that pMAM29 discriminates the R. salmoninarum genome from that of other fish pathogens such as Aeromonas salmonicida, Yersinia ruckeri, Flexibacter columnaris, Lactobacillus piscicola, Vibrio ordalii, Vibrio anguillarum and Aeromonas hydrophila. Thus, this probe may provide a new means to diagnose bacterial kidney disease in asymptomatic fish and ova.The authors are with the instituto de Bioquímica, Universidad Austral de Chile, P.O. Box 567, Valdivia, Chile