Supplementation of L-glycine and L-glutamate to Japanese quails from 01 to 36 days of age using the ideal protein concept.

Experiment I: T1-1 =  basal diet with 25% crude protein (CP) + limiting amino acids (LA); T1-2  = 20% CP + LA; T1-3  = 20% CP + LA + L-glycine; T1-4  = 20% CP + LA + L-glutamate; T1-5  = 20% CP + LA + L-glycine + L-glutamate. Experiment II: T2-1  = basal diet with 22% CP + LA; T2-2  = 20% CP + LA; T2-3  = 17.6% CP + LA + L-glycine; T2-4  = 17.6% CP + LA + L-glutamate; T2-5  = 17.6% CP + LA + L-glycine + L-glutamate. The reduction of dietary protein based on the concept of ideal protein decreases nitrogen excretion in quails when L-glycine is added to the diets. Quails fed diets supplemented with L-glutamate as the non-specific nitrogen source equivalent to the nitrogen level of the control diet had increased nitrogen excretion. However, quails had reduced nitrogen excretion in both experiments when L-glycine was added to diets with L-glutamate. Carcass fat was increased by reducing dietary protein, but fat deposition was reduced by adding L-glutamate and L-glycine, or both. The dietary addition of L-glutamate and L-glycine in quails based on the ideal protein concept is not necessary (Exp. I). Although the total nitrogen, electrolytic balance and glycine level were adjusted in diets, quails had decreased performance. Therefore, other hypotheses besides protein reduction need to be studied (Exp. II). Protein reduction with supplementation of only limiting essential amino acids does not affect quail performance. Dietary addition of L-glycine reduces nitrogen excretion.

Chemical communication in Schizocosa malitiosa: evidence of a female contact sex pheromone and persistence in the field.

Mate finding in many spider species is mediated, at least in part, by chemical cues. Although few have been characterized, most spider sex pheromones seem to be associated with the silk threads of adult females, attracting and/or triggering sexual behaviors in males. Schizocosa malitiosa (Araneae: Lycosidae) is a wolf spider common in dry environments in Southern Uruguay. Here, we report evidence for the occurrence of a female sex pheromone in the silk of virgin S. malitiosa females. The pheromone elicits typical courtship displays by conspecific males (palpal drumming and leg shaking), when it is applied to an artificial substrate. We also showed that this pheromone is quickly inactivated under field conditions, possibly due to the effect of dew, and that it is readily extracted from the silk by water, which renders the silk threads inactive. Preliminary chemical analyses by mass spectrometry suggest that the pheromone is a low molecular weight, highly oxygenated polar compound, present in a high concentration only in older virgin females. Quick inactivation in the field of the pheromone would allow males to discriminate between recent and old cues, thus facilitating mate searching and sexual meeting, by preventing males from following old cues for wandering females that could be distant in space and/or time.

Mating system in the tarantula spider Eupalaestrus weijenberghi (Thorell, 1894): evidences of monandry and polygyny.

The road tarantula Eupalaestrus weijenberghi shows a strongly female-biased sex ratio since adult females live several years while adult males live only for 2 months. In this scenario selective males could be expected. However, several factors such as the rates of reproduction of each sex, degree of sexual selectivity and synchronicity of female receptiveness determine the operational sexual ratio and mating system of the species. Our objective was to determine the mating rates and mating tactics for females and males of E. weijenberghi and their variation throughout the reproductive period. Four hundred sexual encounters among 20 females and 20 males in all possible pair-wise combinations were carried out during 29 days, a brief but intense experimental period, as it also occurs in the field. Mating success differed strongly between sexes. Females mated once: five females mated at the first attempt, eight initially rejected males and copulated in subsequent attempts. Half of the males did not copulate and the others copulated 1-3 times. Mated females actively rejected males. Results indicate a mating system with monogamous females and polygamous males. Not all the females were receptive in every reproductive season. We suggest that female monogamy drastically affects the operational sex ratio, since several females were unreceptive after a single copulation, directly diminishing the male potential reproductive rate. This is the first experimental approach to estimate tarantula mating systems, their determinants and the consequences of the strategies shown by each sex.

Energy sources from the eggs of the wolf spider Schizocosa malitiosa: isolation and characterization of lipovitellins.

In oviparous species, proteins and lipids found in the vitellus form the lipoproteins called lipovitellins that are the major source of energy for the development, growth, and survival of the embryo. The energy resources provided by the lipovitellins have not yet been investigated in the Order Araneae. Using the wolf spider Schizocosa malitiosa (Lycosidae) as an experimental model, we identified and characterized the lipovitellins present in the cytosol, focusing on the energetic contribution of those lipoprotein particles in the vitellus. Two lipovitellins (LV) named SmLV1 and SmLV2 were isolated. SmLV1 is a high-density lipoprotein with 67% lipid and 3.6% carbohydrate, and SmLV2 is a very high-density lipoprotein with 9% lipid and 8.8% carbohydrate. Through electrophoresis in native conditions we observed that SmLV1 has a molecular mass of 559 kDa composed of three apolipoproteins of 116, 87, and 42 kDa, respectively. SmLV2 comprised several proteins composed of different proportions of the same subunits (135, 126, 109, and 70 kDa). The principal lipids of these lipovitellins are sphingomyelin + lysophosphatidylcholine, esterified sterols, and phosphatidylcholine. Lipovitellin-free cytosol contains abundant phospatidylcholine and triacylglyceride related to the yolk nuclei (the vitellus organizing center). The principal fatty acids of SmLV1 and SmLV2 are 18:2 n-6, 18:1 n-9, and 16:0. Spectrophotometry detected no pigments in either the lipovitellins or the cytosol. The egg caloric content was 92 cal/g, at proportions of 59.8% protein, 20.1% carbohydrate, and 19.9% lipid. SmLV1 and SmLV2 provided 19.5% and 17.1% of the calories, respectively. Both lipovitellins contribute mainly with proteins (15.8-18%), with the input of carbohydrates and lipids being lower than 1.3%.