A bioenergetic assessment of the influence of stocking practices on rainbow trout (Oncorhynchus mykiss) growth and consumption in a New Zealand lake

Summary

• 1 To investigate the carrying capacity and factors affecting growth of rainbow trout in Lake Rotoiti, we employed a bioenergetics model to assess the influence of stocking rates, timing of releases and prey abundance on growth and prey consumption. We hypothesised that stocking rates and prey abundance would affect growth and prey consumption by influencing per‐capita prey availability, and that the environmental conditions encountered by fish at the time of stocking would affect growth and consumption.
• 2 Prey consumption of stocked rainbow trout was calculated with the Wisconsin bioenergetics model. We calculated growth trajectories of released trout based on data from stocked trout that were released in spring and autumn from 1993 to 2009 and then re‐captured by anglers. Diet, prey energy density, body mass lost during spawning and lake temperature were measured locally.
• 3 Stocking timing had no effect on return rates to anglers or length or weight of caught fish. Although trout released in autumn were smaller than those released in spring, autumn‐released trout grew at a faster rate and had similar lengths and weights to spring cohorts after 2 years of growth in the lake. Modelled consumption parameters were negatively correlated with trout population size, suggesting that stocking rates (347–809 fish ha^?1 year^?1) caused density‐dependent effects on growth. Although common smelt (Retropinna retropinna) accounted for 85% of total prey consumption, no significant relationship was found between prey consumption by individual trout and adult smelt abundance, possibly because trout are targeting smaller smelt that our abundance estimate did not account for.
• 4 Releasing trout in autumn appears to be advantageous for growth, possibly because (i) temperature is more suitable for growth in autumn–winter than in spring–summer and (ii) prey for small trout is abundant in autumn. Mild winter conditions appear to enhance overwinter survival and growth of rainbow trout in warm‐temperate lakes compared to higher latitudes. This implies that moderately productive warm‐temperate lake ecosystems are highly suitable for trout growth in winter, but less so in summer, when lake stratification and high nutrient levels may create conditions suitable for algal blooms and hypolimnetic deoxygenation. High growth rates of trout in warm‐temperate lakes can therefore be supported by timing releases to coincide with favourable winter conditions.

     

Genome organization in diploid hybrid species of Argyranthemum (Asteraceae) in the Canary Islands

Two diploid species of hybrid origin, Argyranthemum lemsii and A. sundingii , have been described from different valleys in the Anaga peninsula, north-east Tenerife. They have previously been shown to originate from hybridization between the same parental species, the montane A. broussonetii and the coastal A. frutescens , A. broussonetii being the chloroplast donor in one valley and A. frutescens in the other. The specific status of the two hybrid species has been questioned. In this study we used karyotype analysis, FISH, and GISH to address the question of multiple diploid hybrid speciation. GISH did not discriminate clearly between the parental genomes, but differential labelling was observed in separate hybrid populations, indicating different chromosomal rearrangements in different valleys. Small karyotype differences and local loss of rDNA were also observed. Thus separate origins of the same hybrid combination in different valleys in Tenerife have been verified. Our results add some support to the recognition of two species of hybrid origin, but the case serves to illustrate some of the many problems connected with the species concept in plants.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 491–501.     

Sexually transmitted disease in a promiscuous insect, Adalia bipunctata

Abstract.

• 1 Sexually transmitted diseases (STDs) have rarely been reported in insects and other invertebrates. The majority of those reported involve organisms where sexual transmission is augmented by either vertical (i.e. inherited) transmission, or horizontal transmission, independent of host sexual activity.
• 2 We here demonstrate the existence of an STD in the coccinellid beetle Adalia bipunctata. This species bears a parasitic mite of the genus Coccipolipus. We show that, like many other podapolipid mites, this mite is transmitted between host individuals at a high rate during copulation. It also appears to be transmitted at a low rate between non-copulating individuals.
• 3 We show that infected female A.bipunctata produced eggs at a reduced rate, and that the eggs produced by infected females have highly decreased viability. However, no effect of infection upon host longevity was observed.
• 4 The results are discussed in relation to the incidences of sexually transmitted disease in invertebrates in general, the causes of disease symptoms, and the importance of this disease in the evolution of A.bipunctata.

     

The parabolic pattern of animal growth: determination of equation parameters and their temperature dependencies

1. Parabolic (power) growth is characteristic of many aquatic poikilothermic animals for certain stages of their development. The parabolic pattern describing growth in weight (or length) under constant ambient conditions can be expressed in the following general form: where Y is growth rate (or specific growth rate), X is animal size, and Ω and τ are coefficients. The constancy of ambient conditions is of cardinal importance in determining τ. The problem of maintaining a constant level of nutrition can be reliably solved only by the presence of food in excess of demand. Data satisfying these requirements have demonstrated that τ does not depend on factors such as temperature, and can be assumed to be independent of ambient conditions. In the growth rate-weight equation, τ ranges between 0.5 and 0.85 for animals representing a variety of taxonomic groups. 2. The coefficient Ω. is affected by ambient conditions (e. g. temperature, amount of food). Its value reflects the ‘level’ of the growth rate-size relationship under given conditions. For a specific time period, Ω can be computed from the following formula: where X₁ and X₂ are the animal sizes (weights, lengths) at time t₁ and t₂, the beginning and end of the time period. The calculated value of Ω corresponds to the average intensity of the ambient factor (F) affecting the growth during the period between the two observations. If the values of the Ω are calculated for wide range of the factor, the relationship between the Ω. and F, Ω=f(F), can be determined. The function can be then incorporated into the parabolic equation of growth, as 3. Dependence of the development rate (1/D, where D is time interval needed to complete a given stage) on temperature (T), and dependence of Ω on T, are both described by sigmoid-shape curves. The broad intermediate part of these curves, a range to which animals are adapted in nature, can be approximated by straight line functions. For two groups, pan-size sockeye salmon (Oncorhynchus nerka) and different species of chironomid larvae, it was shown that an equation combining parabolic growth and linear temperature patterns describes accurately the variability observed in growth rates under experimental and natural conditions.     

Nuclear DNA Amounts in Angiosperms--583 New Estimates

The amount of DNA in the unreplicated haploid nuclear genome(itsC-value) varies over 600-fold between angiosperm species.Information regarding this character is used in a strikinglywide variety of plant biological fields. Moreover, recent studieshave noted a significant need for more information about thisimportant aspect of genome biodiversity. Bennett and co-authorshave published four collected lists of nuclear DNA amounts inangiosperm species, compiled primarily for reference purposes,including the most recent in 1995 (Annals of Botany76: 113–176).Together they list estimates for over 2500 species which representabout 1% of the global angiosperm flora. Interest in angiospermgenome size has remained high, as shown by the recent publicationof many new estimates, creating a need for a fifth compilation.This paper presents a supplementary list of nuclear DNAC-valuesfrom 37 sources for 471 angiosperm species not listed in theaforementioned compilations, plus additional estimates for 113species already listed by them. It contains estimates for palm,orchid and tropical hardwood species which significantly improvesrepresentation of the global flora. Work is in hand to combinethe genome size data compiled in this and the aforementionedpapers into a unified database, and to present the informationin separate lists, with species in alphabetical and systematicorders, respectively. Meanwhile, the availability of DNAC-valuesfor angiosperm species can be checked on the World Wide Web(http://www.rbgkew.org.uk/cval/database1.html). Angiosperm DNA amounts; DNAC-values; nuclear genome sizes; reference lists; plant DNA database     

DNA amounts for five pteridophyte species fill phylogenetic gaps in C-value data

C-values are important biodiversity characters, yet data for pteridophytes are scarce. A recent survey showed that reliable C-value data were available for only 62 species. This paper reports C-value estimates for a further five pteridophyte species which were selected to fill phylogenetic gaps identified in previous work: Angiopteris lygodiifolia , of the eusporangiate fern family Marattiaceae (1C = 7.10 pg); Lygodium japonicum , of the basal leptosporangiate fern family Schizaeaceae (1C = 11.66 pg); Marsilea quadrifolia , of the heterosporous water fern order Marsileales (1C = 4.01 pg); Isoetes lacustris (1C = 11.97 pg) and Lycopodium clavatum (1C = 2.86 pg), of the lycophyte families Isoetaceae and Lycopodiaceae, respectively. The C-value estimates are discussed in the context of other C-value data. Further, the range of C-values in lycophytes (0.16 pg – 11.97 pg), which comprise Selaginellaceae, Isoetaceae and Lycopodiaceae, is discussed in relation to nucleotypic constraints imposed by sperm flagella number.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 169−173.     

Brood chambers constructed from spines in fossil and Recent cheilostome bryozoans

Most cheilostome bryozoans brood their larvae in skeletal structures called ovicells which, in evolutionary terms, were derived from spines. Ovicells in the great majority of fossil and Recent cheilostomes, however, have lost all or most traces of their spinose origin. Here we review the occurrence of spinose (including costate) brood chambers in cheilostomes, investigating in detail 32 species belonging to ten genera among five families (Calloporidae, Monoporellidae, Macroporidae, Cribrilinidae and Tendridae). Spinose ovicells are moderately common in the Upper Cretaceous, where they are recorded in 28 species, and also occur in one Palaeocene, seven Eocene‐Miocene and 11 Recent species. The most primitive cheilostome ovicells occur in mid‐Cretaceous calloporids in which a group of mural spines belonging to the distal zooid were apparently bent towards the maternal zooid to form a cage‐like structure for reception of the embryo. The bases of these spines were initially aligned in a distally concave row that later became straight, distally convex and finally horseshoe‐shaped, affording progressively better protection for the developing embryo. We suggest that primitive monoporellids inherited from calloporid ancestors a distally concave arrangement of ovicell spine bases, while cribrilinids inherited a horseshoe‐shaped arrangement. Important trends that can be recognized in early ovicell evolution include: (1) loss of basal spine articulation; (2) spine flattening; (3) closure of the gaps between spines; (4) reduction in spine number (through loss or fusion), and (5) development of a concave ovicell floor. The conventional ‘unipartite’ ovicells found in the majority of cheilostomes may have originated either by spine fusion, as seems likely in some cribrilinids, or through a progressive loss of spines via an intermediate stage, seen in some calloporids and in two monoporellids, where the ovicell comprises a large pair of flattened spines. The spinose ovicells of some monoporellids and macroporids subsequently evolved investments of hypostegal coelom that allowed secretion of a surface layer of cryptocystal calcification. Acanthostegous brood chambers characteristic of Tendridae apparently provide an example of independent evolution of spinose brooding structures. © 2005 The Natural History Museum, London, Zoological Journal of the Linnean Society, 2005, 144 , 317?361.     

Distribution fields for aquatic ecosystem components: method of identification of correlation zones

1. Data from the two multidisciplinary surveys of Lake Kinneret (Israel), including acoustic surveys of fish concentrations and concurrent sampling of plankton at stations, were used to reconstruct fish and plankton distributions. No significant lake-wide correlations for the distribution fields were found. With respect to patchiness of the fish and plankton distributions, we hypothesized that they might be correlated in localized zones. 2. A method is suggested for the identification of areas where there are strong correlations of two distribution fields. The method is based on outlining zones where the gradients of the two fields of interest are in the same direction (or are opposite). Only areas larger than the autocorrelation circles (or ellipses) for the fields are considered. The correlation of the fields is calculated for each of the zones selected. 3. The method was used in analysing data from the multidisciplinary surveys. We were able to detect areas of the lake where there were correlations for fish and plankton distributions. Analysis of specific conditions inside the correlation zones made it possible to construct hypotheses concerning the causes for the observed patterns of fish and plankton distributions.     

Wild and agronomically important Agave species (Asparagaceae) show proportional increases in chromosome number,genome size,and genetic markers with increasing ploidy

Agave (Asparagaceae) includes cultivated and wild varieties of henequen used for hard fibre production. As part of a breeding programme to improve Agave production, species with different ploidy levels were genetically characterized: two diploids [A. tequiliana Weber and the hybrid H11648 ((A. amaniensis Trel. & Nowell × A. angustifolia Haw.) × A. amaniensis)], a triploid (A fourcroydes Lem. var. kitam ki), a tetraploid (A. angustifolia var. letona), three pentaploids (A. fourcroydes var. sac ki, A. fourcroydes var. yaax ki, and A. sisalana Perrine), and two hexaploids (A. angustifolia var. chelem ki from two locations). Chromosome spreading was used to determine the chromosome number, flow cytometry was employed to measure the genome size, and fluorescent in situ hybridization was performed using 45S and 5S ribosomal DNA (rDNA) and the telomeric sequences (TTAGGG)_n and (TTTAGGG)_n as genetic markers. There were proportional increases with ploidy level of the following: (1) chromosome number (from diploid 2n = 2x = 60 to hexaploid 2n = 6x = 180), including the number of large and small chromosomes in the bimodal karyotype of Agave; (2) genome size, with a mean monoploid genome size (1Cx) of 7.5 pg (range, 7.36–7.61 pg); and (3) the number and distribution of 45S and 5S rDNA loci, with one locus of each per basic, monoploid genome. Thus there was complete additivity in genome structure with increasing ploidy, as reported in some angiosperm polyploids. However, as other analyses of polyploids have revealed a decrease in 1Cx values with increased ploidy, possible explanations for the observed genomic stability were considered. With the (TTAGGG)_n probe, the signal was localized at the telomeres, consistent with published data showing that many species in the order Asparagales have this type of telomere sequence. It is speculated that sporadic telomeric signals using the (TTTAGGG)_n probe are probably derived from either errors in telomerase activity or relic ancestral‐type telomeric sequences. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 215–222.