Sampling bias in estimating Design II variance components with S1 families

Summary The use of several S₁ individuals to represent an S₀ individual permits the use of a Design II mating scheme for plants with only one pistillate flower per plant. Estimates of additive (V _A ) and dominance (V _D ) variance from this mating scheme will be biased upwards, when a small number (10) of individuals of each S₁ line are used. This bias can be computed, and the additive and dominance estimates can be corrected. Of particular interest is the observation that the additive genetic variance contributes to bias in estimates of V _D . When S₀ plants are non inbred and their selfedprogeny (S₁ lines) are used to represent them in developing families for use in the Design II, where m₁ is the number of individuals used to represent an S₁ line in developing half sib-families and m₂ is the number of individuals used to represent the S₁ line in making up full sib-families. For example, in a 3×3 Design II, with about 10 individuals used to represent each S₁ line in each cross, m₂ = 10 and m₁ = 30. When m₁ = m₂ = 1, and Joint contribution from Department of Agronomy, University of Nebraska 68583, and the S. S. Cameron Laboratory, Werribee, Victoria 3030, Australia. Published as paper No. 7395, Journal Series     

Effect of initial size on subsequent growth and carcass characteristics of divergently selected channel catfish

Summary Two experiments were conducted simultaneously to determine (1) if fast-growing fingerlings of channel catfish, Ictalurus punctatus, could be identified by simple visual selection of body size and (2) if initial size advantages influenced subsequent growth and carcass traits of divergently selected channel catfish. Exp. 1 included large (L), medium (M), and small (S) fingerling sizes from each of the control (C), selected upward (+) and selected downward (–) lines for body weight. Exp. 2 included all fmgerlings of the same size (25±5 g) from the 3 lines. Catfish from the L size-class, within each full-sib family in each line, were consistently heavier and longer than M and S size-classes throughout the 53-week experimental period. Fingerlings from the M size-class were also superior in growth to those from the S size-class. Catfish from the + line exceeded those from the C and –lines in body weight and total length at the conclusion of Exp. 1 but not in Exp. 2. This was attributed to the selection of equal size fmgerlings in Exp. 2 which may have excluded fingerlings with the best growth potential from the + body weight line. Results of the two experiments combined indicated that one generation of divergent selection has created genetic differences among lines of channel catfish.Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Station     

Seasonal and size-related changes in the food of the short-finned eel,Anguilla australis in Lake Ellesmere,Canterbury, New Zealand

Synopsis An approximately monthly sampling programme in Lake Ellesmere, Canterbury, New Zealand, from January 1974 to April 1976 yielded 487 eels. The stomachs were fixed in 10% neutralised formalin and the contents examined. Preliminary analysis indicated that the mollusc Potamopyrgus antipodarum, the isopod Austridotea annectens, the mysid Tenagomysis chiltoni, the amphipod Paracalliope fluviatilis, the midge larva Chironomus zealandicus and the teleosts Retropinna retropinna, Galaxias maculatus and Gobiomorphus cotidianus together made up the bulk of the diet. The pre-ingested dry weight (i.e. the reconstructed weight) of the most important of these prey species was obtained by relating the length of a digestion resistant part to actual dry weight in field collected specimens. Regression equations for this relationship in each season enabled the reconstructed dry weight of each stomach item to be calculated. In some instances reconstructed weight was less than the actual digested dry weight of the prey specimen. In every case the larger value was used. This method is referred to as Combination Dry Weight (CDW) and is believed to be new. These data, used in conjunction with the energy content of the species concerned, enabled the caloric dietary contribution of each prey species to be determined. Comparison of relative contribution to eel diet between CDW and energy values calculated from CDW and bomb calorimetry revealed large differences. Marked variations in diet between ⩽40 cm, 40.1–50 cm, and>50.1 cm size classes were also shown. Eels ≤40 cm feed primarily on invertebrates and become progressively more piscivorous as they grow. Eels >50.1 cm are almost entirely piscivorous. Seasonal differences in diet also exist within each size class examined.     

Characteristics and determinants of osmotic lysis in chromaffin granules

(1) Using isolated bovine chromaffin granules, we demonstrate that osmotic lysis is not a random process and establish the osmotic pressure dependence of osmotic lysis in chromaffin granules, the so-called osmotic fragility curve. (2) We show by measuring the release of constituents of the granule core and correlating these with changes in spectroscopic parameters (turbidity and endogenous catecholamine fluorescence), that the latter can be safely used to measure lysis. (3) Within a particular granule population, noradrenaline granules lyse at higher osmolarities than adrenaline granules, suggesting a higher core osmolarity of the noradrenaline granules. (4) The size distribution of chromaffin granules as a function of lysis was determined by the use of whole mount electron microscopy. It is shown that the mean size of chromaffin granules decreases as a function of lysis. (5) On the basis of theoretical considerations three alternative models of the sequence of osmotic lysis in chromaffin granules are proposed. The experimental results best support a model which postulates that during partial osmotic lysis, granule membranes reseal into smaller vesicles after graded release of contents. The osmotic fragility would represent several cycles of lysis and resealing and would not be a reflection of the distribution of osmotic pressures in the granule population.     

The spatial pattern in a natural population of goldenrod (Solidago altissima L.), with particular reference to its change during the shoot growth

In a natural population of Solidago altissima L., the changes in the spatial pattern of shoots in the course of growth were studied. The results obtained were summarized as follows:

1. The spatial pattern changed from clumped to random distribution as plants grew. The change seemed to be resulted from some density-dependent process acting at a small spatial scale, probably the competition for space.
2. Large plants tended to distribute themselves more uniformly over the space than the small ones but at the mature stage of growth such a difference was not obviously recognized. The process of appearance of the small-sized plants during successive periods also seemed to be dependent on local density.
3. Large plants at the early stage of growth tended to survive better, and there was a positive correlation between initial size and the size at maturity.
4. From these results, it is inferred that the change of spatial pattern from clumped to random distribution is largely due to the elimination of small shoots as the result of competition for space among individual shoots.

     

Phylogenetic relationships of the garter snakes based on DNA sequence and allozyme variation

We estimated phylogenetic relationships among 26 species of garter snakes (genus Thamnophis ) using allozyme and mitochondrial cytochrome b gene nucleotide sequence variation. Parsimony analyses of the two data sets give substantially different estimates of phylogeny. Several lines of evidence indicate that much of this conflict is due to error associated with the restricted number of characters in each data set. Such sampling error may be reduced by combining all the characters; we therefore present an estimate of phylogeny based on parsimony analysis of all the data combined. All our analyses support several conclusions in conflict with previous views: a very distant relationship between T.errans and T. elegans , non-monophyly of the elegans group (even excluding T: errans ), and nesting of the form validus (previously considered a member of the genus Nerodia ) within Thamnophis.
The combined analysis gives an almost fully resolved tree. However, bootstrapping indicates only weak support for many clades in this tree. Furthermore, paraphyly of the assemblages of cytochrome b gene lineages within T. elegans and T. radix indicate the potential for discordance between the mitochondrial DNA (mtDNA) and species phylogenies through the sorting of ancestral mtDNA polymorphisms. These problems suggest the need for assaying additional characters, especially ones likely to be independent of those used in the present study.     

Reproduction in the North Atlantic oceanic ichthyofauna and the relationship between fecundity and species' sizes

Synopsis The pelagic (589 spp.) and demersal (505 spp.) oceanic ichthyofaunas of the North Atlantic Basin have very different compositions at ordinal and family level. Yet the pattern of relationships between species' maximum size and maximum fecundity from data available (10% of the pelagic, 19% of the demersal species) was similar. A positive relationship between fecundity and weight was confirmed among most teleosts, but was not followed by the elasmobranchs represented. Species' reproductive styles are reviewed in ordinal groupings within a framework of the overall body size/fecundity distribution. Species size (maximum weight) spectra were synthesized for both pelagic and demersal assemblages to assess the allocation of potential reproductive effort throughout the North Atlantic oceanic ichthyofauna. The only available examples of species size spectra and biomass spectra from the pelagic and demersal ichthyofauna in this ocean basin imply geographic and bathymetric variation in overall reproductive effort among fishes whose fecundity is size dependent. Further implications concerning reproductive effort are discussed in the light of food availability.     

Size structure of the metazoan community in a Piedmont stream

We characterized the size structure of virtually the entire metazoan community in a fourth order, sandybottomed Piedmont stream during late summer. Our study, the first to sample across all habitat types and sizes of metazoans in an aquatic ecosystem, indicates that at the community level, stream size spectra may be bimodal for the benthos or trimodal when fish are included. Animals spanning 10 orders of magnitude in dry mass (from gastrotrichs to fish) were quantitatively collected from nine habitat types. The bimodal benthic size spectrum was characterized by a meiofaunal component (mostly oligochaetes and micro-crustacea) and a macrobenthic component (mostly the introduced asiatic clam, Corbicula fluminea). Insects contributed little to overall standing crop. Size-specific contribution to whole-community metabolism was assessed using allometric equations for respiration, and we found a distinctly bimodal distribution across the entire metazoan size range, with peaks in the meiofaunal and benthic macrofaunal size ranges. Our bimodal benthic size spectrum is similar to that observed for marine benthos but not to other freshwater benthic systems, possibly because the entire range of habitat types and/or animal sizes were not sampled in the latter. Numerous factors may influence size spectra in stream ecosystems, including local geomorphic (habitat) conditions, water level fluctuations, species introductions, and predation processes.     

Reproductive biology of the slender smoothhound,Gollum attenuatus,collected from New Zealand waters

Synopsis The reproductive biology of 385 male and 373 female slender smoothhounds,Gollum attenuatus, collected from New Zealand waters was examined. Size at maturity for both sexes was about 700 mm TL. Litter size was usually two. The sex ratio of embryos was 1:1. The right ovary ovulated 50–100 ova, 4–8 mm in diameter, and 30–80 ova were enclosed in each egg capsule. Only one embryo developed from the many ova in each egg capsule, the other undeveloped ova were ingested and passed to an external yolk sac which formed the yolk supply for the developing embryo.