Assessment of inbreeding depression in a Guzerat dairy herd: Effects of individual increase in inbreeding coefficients on production and reproduction

Influences of inbreeding on daily milk yield (DMY), age at first calving (AFC), and calving intervals (CI) were determined on a highly inbred zebu dairy subpopulation of the Guzerat breed. Variance components were estimated using animal models in single-trait analyses. Two approaches were employed to estimate inbreeding depression: using individual increase in inbreeding coefficients or using inbreeding coefficients as possible covariates included in the statistical models. The pedigree file included 9,915 animals, of which 9,055 were inbred, with an average inbreeding coefficient of 15.2%. The maximum inbreeding coefficient observed was 49.45%, and the average inbreeding for the females still in the herd during the analysis was 26.42%. Heritability estimates were 0.27 for DMY and 0.38 for AFC. The genetic variance ratio estimated with the random regression model for CI ranged around 0.10. Increased inbreeding caused poorer performance in DMY, AFC, and CI. However, some of the cows with the highest milk yield were among the highly inbred animals in this subpopulation. Individual increase in inbreeding used as a covariate in the statistical models accounted for inbreeding depression while avoiding overestimation that may result when fitting inbreeding coefficients.

Hydrocoryne iemanja (Cnidaria), a new species of Hydrozoa with unusual mode of asexual reproduction

Hydrocoryne iemanja sp. nov. was found in an aquarium, growing on rhodoliths of coralline algae collected on the southeastern coast of Brazil (20 degrees 40`S 40 degrees 2`W). The colonies were reared through maturity in the laboratory. Each colony had up to 7 sessile, long and thin monomorphic zooids, very extensible and flexible, arising from a chitinous, hard dark-brown plate with minute spines. Medusae budded from near the basal part of hydrocaulus, and were released in immature condition, acquiring fully developed interradial gonads 5-7 days after release. Asexual reproduction by longitudinal fission was observed on the hydrocaulus of the polyps, both for those in normal condition and those with injuries. Fission started at the oral region, extending aborally, with a new hard plate formed in the basal part of hydrocaulus. When fission reached the new hard plate, the new polyp detached, becoming free and sinking to the bottom, starting a new colony. Detached polyps were morphologically indistinguishable from other polyps, being able to produce medusae. Mother and daughter polyps undertook subsequent fissions. This mode of longitudinal fission is distinct from other modes of longitudinal fission, a process known for a few species Of cnidarians. Further studies of this process may shed light on the understanding of the evolutionary pathways in Cnidaria and animals. Hydrocoryne iemanja sp. nov. is distinguishable from its two congeners by the distinct marginal tentacles of the medusae-short and with a median nematocyst knob-an unambiguous character useful even for the identification Of newly liberated medusae.

Effects of competition on sexual and clonal reproduction of a tunicate: the importance of competitor identity

Individual fitness and the structure of marine communities are strongly affected by spatial competition. Among the most common space holders are the colonial ascidians, which have the ability to monopolize large areas of hard substrate, overgrowing most other competitors. The effects of competition on colony growth and on gonad production of the ascidian Didemnum perlucidum were studied in southeastern Brazil by experimentally removing surrounding competitors. Colonies of D, perlucidum competing for space exhibited a growth rate 9 times less than that of colonies that were competitor free. Among the colonies subject to competition, growth rates were unrelated to the percentage of colony border that was free of competitors. However, the identity of the competitor was important in the outcome of border contacts. At the beginning of the experiment, most border encounters of D. perlucidum were with solitary organisms, which in most cases were overgrown. These were progressively replaced by colonial ascidians and bryozoans, resulting mostly in stand-off interactions. Besides reducing asexual growth, spatial competition also affected female gonad production. Colonies free of competitors had a significantly higher proportion of zooids with ovaries. Thus, our findings show that spatial competition reduces both ascidian colony size and gonad production.