Embryonic development of the jumping bristletail Pedetonutus unimaculatus Machida,with special reference to embryonic membranes (Hexapoda: Microcoryphia,Machilidae)

In the machilid Pedetonutus unimaculatus, a germ disc is formed by the aggregation and proliferation of cells within a broadly defined embryonic area. Cells adjacent to the embryonic area form the serosal fold that grows beneath the embryo. Then the embryonic margin is extended to form a cell layer or amnion that lies between the embryo and serosal fold. Thus, an amnioserosal fold is formed by the addition of the amnion to the serosal fold. Serosal cells cover the entire surface of the egg and begin to secrete a serosal cuticle. Soon the amnioserosal fold is withdrawn, and the embryo is exposed to the egg surface. The spreading amnion replaces the serosal cells that finally degenerate through the formation of a secondary dorsal organ. In the areas of amnion anterior and lateral to the embryo, yolk folds form and encompass the embryo. The amnion is a provisional dorsal closure and never participates in the formation of the definitive one. The amnioserosal fold of the Microcoryphia appears to have the functional role of secreting a serosal cuticle beneath the embryo. This fold of the Microcoryphia may be regarded as an ancestral form of the amnioserosal folds of the Thysanura-Pterygota. the yolk folds may appear to be passive transformation of the yolk mass linked to positioning of the growing embryo within the egg. There is no evidence that the yolk folds and the cavity appearing between them in the Microcoryphia are homologous to the amnioserosal fold and amniotic cavity in the Thysanura-Pterygota. The yolk folds appear to be one of the embryological autapomorphies in the Microcoryphia. © 1994 Wiley-Liss, Inc.     

In ovo peptide YY and epidermal growth factor administration and their effects on growth and yolk utilization in neonatal meat-type chickens (Gallus domesticus)

The effects of in ovo peptide YY (PYY) or epidermal growth factor (EGF) administration on chick growth, yolk absorption and yolk stalk function in posthatch (0–5 days) meat-type or broiler chicks were determined. At Day 18 of incubation, treated eggs were injected into the air cell with 100 μl of either PYY (Trial 1) or EGF (Trial 2) at a dosage of 600 μg/kg egg weight. Saline-treated control eggs were injected similarly with 0.9% saline. At hatch, 200 μl of ⁵¹Cr-labeled microspheres were injected into chick yolk sacs. Epidermal growth factor increased ileal wet weight adjusted for body weight as well as ileal serosal dry matter. Body weight, feed consumption and excreta weight per bird, and relative weights of the yolk sac, intestine and liver were significantly affected by age of the chick in both trials. Relative radioactivity of the yolk sac, yolk stalk, blood, liver, and kidneys were affected by bird age in Trial 2; however, there were no significant effects due to PYY or EGF treatments on relative radioactivity of the tissues and organs examined. These data suggest that PYY and EGF had no effect on yolk absorption or yolk stalk function through 5 days in the posthatch chick.     

Effects of egg yolk during the freezing step of cryopreservation on the viability of goat spermatozoa

Four experiments were conducted to investigate the effects of egg yolk during the freezing step of cryopreservation (namely, the process except for the cooling step), on the viability of goat spermatozoa. The effects of egg yolk on sperm motility and acrosome integrity during the freezing step were investigated in Experiment 1. Spermatozoa diluted with Tris-citric acid-glucose (TCG) solution containing 20% (v/v) egg yolk were cooled to 5 degrees C, washed, and then frozen in TCG with egg yolk (TCG-Y), TCG without egg yolk (TGG-NY), 0.370 M trehalose with egg yolk (TH-Y), or trehalose without egg yolk (TH-NY). All extenders contained glycerol. In frozen-thawed spermatozoa, the inclusion of egg yolk in the freezing extenders increased (P<0.05) percentages of motile sperm, progressively motile sperm, and the recovery rate (ratio of post-thaw to pre-freeze values), but decreased (P<0.05) acrosomal integrity. Moreover, extenders with trehalose had better (P<0.05) post-thaw sperm viability. In Experiment 2, the effects of egg yolk on acrosome status before and after freezing were studied. Egg yolk significantly decreased the proportion of intact acrosomes before freezing, leading to fewer (P<0.05) intact acrosomes post-thaw and lower (P<0.05) recovery rates for intact acrosomes. In Experiment 3, including sodium dodecyl sulfate (SDS) in a diluent containing egg yolk tended to preserve the acrosome compared with the egg yolk containing diluent free of SDS, however, spermatozoa had a lower (P<0.05) proportion of intact acrosomes than those in a yolk-free diluent. However, after cooling, spermatozoa were diluted with a glycerolated extender containing egg yolk. Therefore, the objective of Experiment 4 was to explore whether the egg yolk or glycerol was responsible for the reduced intact acrosome percentage. In this experiment, after cooling and washing the spermatozoa were diluted in TCG with glycerol and/or egg yolk. The combination of glycerol and egg yolk in the extender reduced (P<0.05) the proportion of intact acrosomes compared with egg yolk or glycerol alone. In conclusion, the inclusion of egg yolk significantly improved sperm motility, indicating its beneficial effects during the freezing step of cryopreservation; trehalose appeared to synergistically increase its cryoprotective effects. Furthermore, although neither glycerol nor egg yolk per se affected the proportion of intact acrosomes, the combination of the two significantly reduced the proportion of acrosome-intact spermatozoa.     

Cryoprotective and contraceptive properties of egg yolk as an additive in rooster sperm diluents

The addition of chicken egg yolk to semen extenders is thought to reduce the fertilizing potential of rooster spermatozoa - but not (or at least not as much) that of other avian species. The aim of the present study was to determine whether quail egg yolk, a novel extender additive, provides advantages over chicken egg yolk in the cryopreservation of rooster spermatozoa. Experiments were also performed to determine whether the harmful effect of egg yolk occurs during cryopreservation or during fertilization after artificial insemination. Heterospermic rooster semen samples were divided into aliquots and cooled in a polyvinylpyrrolidone-based medium containing 15% chicken egg yolk, 15% quail egg yolk or no egg yolk at all. The viability of spermatozoa of cooled samples (5 °C) without egg yolk were less viable (P < 0.01) than those of samples containing either type of egg yolk. The same aliquots were then cryopreserved for 15 days. Thawed spermatozoa preserved without egg yolk showed lower motility (P < 0.001) and viability (P < 0.001) than those in samples diluted with either type of egg yolk extender. No eggs were fertilized when hens were inseminated with semen that had been diluted with chicken egg yolk. The fertilization rate was only slightly higher when sperm diluted with quail egg yolk was used (1.5%). The best results were obtained when no egg yolk was used (13.8%). These results show that the addition of egg yolk of either type protects rooster sperm cells against cold shock and during freezing and thawing, but exerts a contraceptive effect in the genital tract of the hen.     

The Egg Yolk and Lipolytic Reactions of Coagulase Positive Staphylococci

The composition of egg yolk media is important for the identification of egg yolk positive strains of coagulase positive staphylococci. Media with glucose allowed the detection of more egg yolk positive strains than those without it. However, the presence of 50% CO₂ in the incubation atmosphere allowed a greater number of egg yolk positive strains to be detected regardless of whether glucose was present or not. This was due to the suppression of lipase activity by CO₂ thus allowing total lipid separation indicative of the egg yolk phenomenon. Staphylococcus aureus strains from human nares were egg yolk positive and strongly lipolytic while strains of animal origin and epidermal necrolysis were egg yolk negative and weakly lipolytic.     

A comparison of the protective action of added egg yolks from five avian species to the cryopreservation of bull sperm

Cryopreservation of domestic animal sperm has been widely used for artificial insemination (AI), and egg yolk is one of the most commonly used cryoprotectants during the freezing-thawing process. The objectives of this study were to compare the effectiveness of egg yolk from five avian species (domestic chicken, domestic duck, domestic goose, Japanese quail or domestic pigeon) and to optimize the concentration of egg yolk on the cryopreservation of bull sperm in terms of frozen-thawed sperm progressive motility and viability. The results were two-fold. First, they showed that pigeon egg yolk provided the best cryoprotective effects on the cryopreservation of bull sperm, compared with egg yolk of chicken, quail, goose or duck. Second, the best concentration of pigeon egg yolk in extender was 20% during cryopreservation among five concentrations of 5, 10, 20, 30 or 40%. The results suggest that pigeon egg yolk could be used as an alternative to chicken egg yolk in extender but requires further testing in fertility trials.     

Separation and Formation of Egg Yolk Oil by Solubilizing the Lipoproteins of Spray-dried Egg Yolk into Polypeptides

Egg yolk oil was formed from a hen’s egg without using the traditional charring method and organic solvents. By treating a spray-dried egg yolk suspension with a commercial crude enzyme preparation having protease and lipase activities, the lipids (egg yolk oil) could be easily separated, and a transparent solution of soluble polypeptides was obtained. When the enzyme preparation (4 mg) was added to a 5% spray-dried egg yolk (100 mg) suspension, the reaction mixture became transparent, and the egg yolk oil floated to the surface of the reaction mixture within 3 h. In the case of a 10% spray-dried egg yolk suspension, a transparent solution and egg yolk oil could be successfully obtained within 4 to 5 h by using a larger reaction vessel and a 0.2M lactate buffer. About 87% of the total polypeptides in the initial reaction mixture was recovered from the transparent solution, while about 83% of the total phospholipids was recovered from the floating egg yolk oil.     

Cryoprotective and contraceptive properties of egg yolk as an additive in rooster sperm diluents

The addition of chicken egg yolk to semen extenders is thought to reduce the fertilizing potential of rooster spermatozoa - but not (or at least not as much) that of other avian species. The aim of the present study was to determine whether quail egg yolk, a novel extender additive, provides advantages over chicken egg yolk in the cryopreservation of rooster spermatozoa. Experiments were also performed to determine whether the harmful effect of egg yolk occurs during cryopreservation or during fertilization after artificial insemination. Heterospermic rooster semen samples were divided into aliquots and cooled in a polyvinylpyrrolidone-based medium containing 15% chicken egg yolk, 15% quail egg yolk or no egg yolk at all. The viability of spermatozoa of cooled samples (5 °C) without egg yolk were less viable (P < 0.01) than those of samples containing either type of egg yolk. The same aliquots were then cryopreserved for 15 days. Thawed spermatozoa preserved without egg yolk showed lower motility (P < 0.001) and viability (P < 0.001) than those in samples diluted with either type of egg yolk extender. No eggs were fertilized when hens were inseminated with semen that had been diluted with chicken egg yolk. The fertilization rate was only slightly higher when sperm diluted with quail egg yolk was used (1.5%). The best results were obtained when no egg yolk was used (13.8%). These results show that the addition of egg yolk of either type protects rooster sperm cells against cold shock and during freezing and thawing, but exerts a contraceptive effect in the genital tract of the hen.     

Effect of egg yolk concentration on cryopreserving Spanish ibex (Capra pyrenaica) epididymal spermatozoa

Tris-egg yolk based diluents provide adequate cryoprotection for the sperm of most wild species in which they have been tested. The objective of the current study was to evaluate various Tris-based diluents containing different concentrations of egg yolk, for the fertilizing ability of epididymal spermatozoa of the Spanish ibex (Capra pyrenaica) after freezing and thawing. For this purpose, we used heterologous in vivo fertilization by intrauterine insemination of domestic goats (Capra hircus). In Experiment 1, a Tris-citric acid-glucose (TCG) diluent containing 6% (v/v) egg yolk and a TCG extender containing 20% egg yolk were compared. In Experiment 2, a TCG-6% egg yolk extender was compared with Triladyl-20% egg yolk. Diluted samples were cooled slowly to 5 degrees C over 1 h and equilibrated at that temperature for 2 h. At that point, aliquots of samples were loaded into 0.25 ml straws, and frozen in nitrogen vapor for 10 min. The fertility of spermatozoa frozen in TCG-6% egg yolk was higher (P<0.05) than for those extended with TCG-20% egg yolk, and tended to be higher than for those frozen with Triladyl-20% egg yolk. From the results of this study, the use of Tris-based extenders containing low concentrations of egg yolk (6%) is recommended for cryopreserving Spanish ibex epididymal spermatozoa.     

Quail Egg Yolk: A Novel Cryoprotectant for the Freeze Preservation of Poitou Jackass Sperm

For many years, attempts have been made to establish a sperm bank for the Poitou jackass population which is threatened with extinction. Unfortunately, no cryopreservation technique has ever been described for spermatozoa of this species. In an attempt to find a suitable technique, we studied the relative effectiveness of chicken egg yolk and quail egg yolk in preserving the motility and characteristics of movement of Poitou jackass spermatozoa during the freezing–thawing process. Semen was diluted to 60 × 10⁶sperm/ml in a preservation medium containing 4% (v/v) glycerol with 0, 2, 5, 10, 15, or 20% (v/v) of chicken or quail egg yolk. The chemical composition of these two eggs was compared. Effects were assessed using an automated analyzer which measured curvilinear velocity (VCL), straight line velocity (VSL), and the velocity of the average path. Linearity was defined as VSL/VCL × 100. The amplitude of the lateral head displacement was also measured. It was found that after the freeze–thaw process, quail egg yolk improved the percentages of motile and progressively undulating spermatozoa and the movement characteristics compared with chicken egg yolk. The optimal concentration of quail egg yolk was 10%. The general composition of the two types of egg yolk were similar, but quail egg yolk contained significantly more phosphatidylcholine, less phosphatidylethanolamine, and a smaller ratio of polyunsaturated to saturated fatty acids than chicken egg yolk. The improvement of motility for frozen–thawed Poitou jackass spermatozoa using frozen–thawed quail egg yolk compared to chicken egg yolk may be due to the differences in composition of the two yolks.     

The serosa of Manduca sexta (Insecta, Lepidoptera): ontogeny, secretory activity, structural changes, and functional considerations

In Manduca sexta, the blastoderm forms successively and becomes immediately cellularized as the cleavage energids reach the surface of the oocyte. Presumptive serosal cells are large and contain 2 or 4 large polyploid nuclei; presumptive embryonic cells are small and mononuclear. All parts of the blastoderm participate in the uptake and digestion of yolk material. About 10 h post-oviposition, the blastoderm breaks at the amnioserosal fold and the extraembryonic part closes above the germ band and constitutes the serosa (12 h post-oviposition, i.e. 10% development completed). At once, the serosa starts to secrete a cuticle consisting of an epi- and a lamellated endocuticle. Detachment of the serosal cuticle, 22h post-oviposition, is reminiscent of apolysis of larval cuticle. Thereafter, the serosa deposits a membranous structure, the serosal membrane. The sercretory process lasts from 23h to 44h post-oviposition. At first a fine granular layer, then an amorphous, spongy-like, fibrillar layer is secreted via microvilli. This persisting membrane is tough, rubbery and very elastic. It may serve to bolster the serosa during katatrepsis (48h post-oviposition) and later embryonic movements. After detachment of the serosal membrane, 44h post-oviposition, a distinct subcellular reorganization of the serosa takes place. The nuclei become still larger and more irregular. Uptake of yolk granules, but not of lipid droplets, ceases, although interaction of serosa and yolk cells are intense. Serosal cells include many mitochondria, large areas of rER, besides some sER, increasing amounts of lysosomal bodies and prominent Golgi complexes. Most conspicuous is the assembly of spindle-shaped, electron-lucent vesicles below the apical surface. These vesicles may contain metabolic products which are released into the peripheral space. The studies show that the serosa assumes changing functions during embryogenesis: digestion of yolk substances, synthesis of a serosal cuticle and a serosal membrane, which may have a protective function, and excretion.     

Development and ultrastructure of the thickened serosa and serosal cuticle formed beneath the embryo in the stonefly Scopura montana Maruyama, 1987 (Insecta,Plecoptera, Scopuridae)

We aimed to describe the development and ultrastructure of the thickened serosa and serosal cuticle formed beneath the embryo of Plecoptera, using Scopura montana of Scopuridae as a euholognathan representative. Using transmission electron microscopy, we found that the egg membranes were composed of a thick exochorion, a thicker endochorion consisting of two sublayers, and an extremely thin vitelline membrane. The egg membrane construction represents a groundplan feature of the euholognathan egg membranes. The serosa converges beneath the embryo to form a thickened serosa, comprising cells in a radial arrangement, in association with the formation of the amnioserosal fold. The thickened serosa then deposits the thickened serosal cuticle, consisting of four layers differing in fine structure and electron density. After achieving its secretory function, the thickened serosa then disintegrates, and the liberated serosal cells float for a short period in the peripheral region of the egg inside. Collectively, our findings should provide the basis for further characterization of the serosal structures concerned, but we were unable to corroborate previous studies assigning the thickened serosa and serosal cuticle in Plecoptera to the water absorption function.     

Yolk lipids.

The mature egg yolk of the domestic hen possesses remarkably constant lipid and lipoprotein composition despite much variation in dietary and environmental conditions. The greatest differences are seen in the fatty acid composition of the triacylglycerols which may show significant alterations in the content of the minor acids including certain polyunsaturated acids. The lipid class composition appears to be minimally affected by dietary influences, including the cholesterol content of the diet. The limited dietary influence on the yolk lipid composition extends to different strains of the hens. Genetic selection has led to some increase in the cholesterol content of the egg, but the desired lowering of the cholesterol content of egg yolk has not been realized. Likewise, production of a polyunsaturated fatty acid egg does not appear to be practical. As a result the egg yolk continues to provide a food product of nearly constant composition, which serves to maintain its chemical and physico-chemical properties for reliable utilization in the baking, cosmetic and pharmaceutical industries. The great uniformity in the composition of the egg yolk phospholipids makes them desirable starting materials for partial chemical resynthesis of glycerophospholipids. Partial hydrogenation of the egg yolk lipids promises to further increase the utility of the product as a desirable material for the manufacture of liposomes and liposome based drug products. In contrast, the constancy of the egg yolk composition and the inability to alter it significantly by dietary or genetic means also renders egg yolk undesirable for unlimited human consumption. Excessive ingestion of egg yolk raises plasma lipid and cholesterol levels which are believed to contribute to the development of heart disease. The physico-chemical and biological properties of egg yolk apoproteins have been less extensively investigated and their function is less well understood. The finding that phosvitin is a effective chelator of metal ions and thus an effective antioxidant demonstrates that egg yolk lipoproteins possess as yet unexplored potential for beneficial nutritional, medical and industrial application.     

Cryopreservation of Spanish ibex (Capra pyrenaica) sperm obtained by electroejaculation outside the rutting season

The effectiveness of electroejaculation for obtaining Spanish ibex sperm samples for freeze preserving outside the rutting season was evaluated—the aim being to optimise biological resources for the establishment of germplasm banks. The effect of different egg yolk concentrations (6% or 12%, v/v) in diluents of different buffer composition (Tris-citric acid buffer or Tes-Tris buffer) on frozen-thawed samples of the above also investigated. Experiments were undertaken with six ibex males in February-May, and involved four different semen samples from each animal with four combination of extender, respectively: Tes-Tris-glucose (TTG)-6% egg yolk, TTG-12% egg yolk, Tris-citric acid-glucose (TCG)-12% egg yolk, TCG-6% egg yolk. The results show that electroejaculation is a useful way of obtaining sperm samples from Spanish ibex outside the rutting season (i.e., at a time coinciding with plasma testosterone levels of <0.4 ng/ml). According to the results of the eosin-nigrosin staining and the hypo-osmotic swelling test, the freezing-thawing process significantly reduced the viability and membrane integrity of the spermatozoa extended with TTG-6% egg yolk, TTG-12% egg yolk, and TCG-12% egg yolk, but did not affect these variables in spermatozoa extended with TCG-6% egg yolk. Therefore, the use of Tris-citric acid-based extenders containing low concentrations of egg yolk is recommended for cryopreserving Spanish ibex spermatozoa obtained by electroejaculation outside the rutting season.     

Influence of high vitamin E dosages on retinol and carotinoid concentration in body tissues and eggs of laying hens

The aim of the study was to contribute to the discussion of overdosing vitamin E in laying hens. A total of 45 laying hens, divided into 5 groups were fed diets supplemented with either 0; 100; 1000; 10 000 or 20 000 mg dl‐α‐tocopheryl acetate/kg diet over a period of 10 weeks. Concentrations of vitamins A and E were measured in plasma, various tissues and egg yolk. Furthermore egg yolk colour and some carotinoids were measured in egg yolks. None of the vitamin E doses significantly influenced performance of the hens. As expected, vitamin E concentration in plasma, all tissue samples and egg yolk was significantly increased with increasing tocopherol content in the diet. The egg yolk showed the highest vitamin E concentration, followed by liver and muscles. Feeding 1000 mg α‐tocopheryl acetate per kg diet resulted in an increase of vitamin A concentration in the liver. Very high doses (10 000 and 20 000 mg/kg diet) significantly decreased retinol concentration in the liver and egg yolk, as well as carotinoid concentration in the egg yolk. The lower carotinoid concentration in egg yolk resulted in a decreased intensity of egg yolk colour. A prooxidative and/or competitive effect of very high doses of vitamin E with other fat soluble substances has been discussed.     

Effects of egg yolk and salt on Micrococcaceae heat resistance.

The heat resistance and growth possibilities of various members of the Micrococcaceae in egg yolk and egg yolk with added salt were determined. Egg yolk alone protected members of the Micrococcaceae considerably against heat. Whereas in water Staphylococcus aureus S6 had a decimal reduction time (D) value of 66 s at 55 degrees C, its D value in egg yolk at the same temperature was 246 s. In salted egg yolk (water activity, 0.95), S. aureus S6 had a D value of 180 s at 66 degrees C and was largely inactivated during the pasteurization processes currently applied. Micrococcus saprophyticus and S. epidermidis (D value of each under the same conditions, 390 s) could survive such treatments to a certain extent and can thus spoil commercial egg yolk.     

l-Tryptophan Production by Achromobacter liquidum

The heat resistance and growth possibilities of various members of the Micrococcaceae in egg yolk and egg yolk with added salt were determined. Egg yolk alone protected members of the Micrococcaceae considerably against heat. Whereas in water Staphylococcus aureus S6 had a decimal reduction time (D) value of 66 s at 55 degrees C, its D value in egg yolk at the same temperature was 246 s. In salted egg yolk (water activity, 0.95), S. aureus S6 had a D value of 180 s at 66 degrees C and was largely inactivated during the pasteurization processes currently applied. Micrococcus saprophyticus and S. epidermidis (D value of each under the same conditions, 390 s) could survive such treatments to a certain extent and can thus spoil commercial egg yolk.     

Egg yolk plasma can replace egg yolk in stallion freezing extenders

Hen egg yolk is normally used as a cryoprotective agent in semen freezing extenders, but its use has sanitary and practical disadvantages. Moreover the protection afforded by egg yolk has not yet been completely elucidated. The objective of this study was to compare the egg yolk plasma fraction to whole egg yolk in stallion freezing extender. Plasma contains mainly Low Density Lipoproteins (LDL), which are widely presumed to be the cryoprotective agent in egg yolk. Plasma can be produced on an industrial scale, sterilised by gamma-irradiation and incorporated in a ready-to-use extender (our ultimate objective). Plasma samples were subjected to different doses of gamma-irradiation (3, 5, 10 kGy) without dramatic chemical changes that may affect their cryoprotective properties. Stallion semen was frozen with whole egg yolk as a control and with sterilised egg yolk plasma. A fertility trial was conducted on a total of 70 mares' cycles. Fertility per cycle was 60% after insemination of semen frozen in our control extender containing egg yolk (EY), compared to 69% for the extender containing sterilised egg yolk plasma (EYP) (P > 0.05). Post-thaw motility and membrane integrity of spermatozoa were also analysed. Motility parameters were not significantly different between extenders except for the variable VAP (for EY versus EYP, VAP: 63 μm.s⁻¹ versus 59 μm.s⁻¹, a, b: P < 0.001; PROG: 41% versus 39%, RAP30: 56% versus 54%; RAP40: 51% versus 48%, P > 0.05). Membrane integrity was better preserved in EY than in EYP but the difference between extenders was small (P < 0.05). Our results demonstrated that sterilised egg yolk plasma has the potential to replace egg yolk in stallion freezing extender. This experiment led to the development of a ready-to-use extender called INRA-Freeze^® (IMV-Technologies, France).     

The fatty acid composition of oophagous tadpoles (Chirixalus eiffingeri) fed conspecific or chicken egg yolk

We compared the lipid content and fatty acid composition of (1) the egg yolk of three anuran species (Chirixalus eiffingeri, Rhacophorus moltrechti and Buergeria robustus) and chicken eggs; and (2) C. eiffingeri tadpoles fed conspecific eggs or chicken egg yolk. Anuran and chicken egg yolk contained more non-polar than polar lipids but the proportions varied among species. Chicken egg yolk contained low amounts of 22:5n-3 in the polar lipid fraction, and B. robustus eggs did not contain any n-3 or n-6 non-polar lipids. The specific variation of lipid contents and fatty acid composition may relate to the maternal diet and/or breeding biology. In C. eiffingeri tadpoles that fed chicken yolk or frog egg yolk, the dominant components of polar and non-polar lipids were 16:0, 18:0, 18:1, and 18:2n-6, or 20:4n-6 fatty acids. C. eiffingeri eggs contained more n-3 fatty acids (e.g. 18:3n-3 and 20:5n-3) than chicken egg yolk, and tadpoles fed conspecific eggs contained more of these fatty acids than tadpoles fed chicken egg yolk. The compositional differences in the fatty acids between C. eiffingeri tadpoles that fed frog egg or chicken egg yolk are the reflection of the variation in the dietary sources. Our results suggest a direct incorporation of fatty acids into the body without or minimal modification, which provide an important insight into the physiological aspects of cannibalism.     

Long-term preservation of chilled canine semen: effect of commercial and laboratory prepared extenders

The present study was conducted to evaluate chilled semen conservation over time in 3 commercial and 4 laboratory prepared extenders, including a new Tris-glucose extender. The beneficial effect of adding egg yolk to these media was also analyzed. The effects of these extenders on motility and acrosome reaction were characterized objectively using a computer-aided semen analyzer and the chlortetracycline staining, respectively. No significant differences were observed when comparing the different commercial extenders without egg yolk, but addition of egg yolk improved all motility parameters significantly (preservation of 50% of motility was observed at 3.2+/-1, 2.9+/-0.5, 2.3+/-0.5, 8.5+/-0.2, 5.4+/-1.1, 5.2+/-0.4 d, for Biladyl, green extender and fresh-phos extenders without and with egg yolk, respectively). Motility parameters were best preserved in egg yolk supplemented Biladyl extender with a mean percentage of 86.3+/-10.5 motile spermatozoa after 7 d at 4 degrees C. Efficacy of egg yolk-supplemented commercial extenders on sperm motility at 4 degrees C was (in decreasing order) as follows: Biladyl > green extender > fresh-phos. However, high quality motility and the percentage of motile spermatozoa were highest with some of the laboratory prepared extenders: a 50% conservation rate of motile spermatozoa was observed following the use of supplemented egg yolk extenders. These are classified in decreasing order as follows: Tris-glucose (13+/-1 d) > Tris-fructose (9.7+/-0.6) > EDTA (4.+/-0.6 d) > Tris-bes (3.6+/-1.1 d). A low concentration of motile spermatozoa was still observed in the Tris-glucose egg yolk extender 16 d after collection, clearly demonstrating the importance of the medium and the beneficial effect of egg yolk on sperm motility of 4 degrees C chilled semen. Similar effects of extender were observed for acrosome reactions. Egg yolk clearly had a protective effect reducing acrosome reactions significantly in all media tested as follows: the highest acrosome losses were observed in the fresh-phos and EDTA extenders without egg yolk; the lowest rate was observed with Tris-glucose supplemented egg yolk extender. In conclusion, at 4 degrees C, egg yolk extender best-protected sperm motility parameters. Differences in osmolarity between the extenders in terms of substrate related to sperm metabolic activity may explain the optimal results obtained using egg yolk-supplemented Tris-glucose extender, which preserved motility and acrosome integrity in chilled dog semen. These results indicated that good quality dog spermatozoa could be preserved for up to 10 d.