Use of Relief Contrast® Objective to Improve Sperm Morphometric Analysis by Isas® Casa System in the Ram

The aim of this study was to develop a new method for morphometric assessment of the sperm head and acrosome in the ram. Ejaculates from 10 adult males were collected using an artificial vagina. For each ejaculate, 10 semen smears were prepared, air‐dried and divided (in pairs) into the following five treatment groups: (i) washed in distilled water and allowed to dry without further processing (DRY); (ii) fixed in 50% methanol (MET); (iii) fixed in 2% glutaraldehyde (GLUT); (iv) fixed and stained with Hemacolor^® (HEM) and (v) fixed and stained with SpermBlue^® (SB). The prepared slides were examined with a 40 × Relief Contrast^® objective (RC) and processed with ISAS^® commercial software. The use of RC optics increased the contrast between acrosome and sperm head, allowing capture and morphometric analysis by ISAS of sperm heads and the acrosome, even in non‐stained samples. MET and GLUT groups resulted in a lower number of acceptable, that is, correctly delineated, sperm heads than those in the SB, and SB and HEM groups, respectively (p < 0.05). The higher proportion of sperm discarded in MET and GLUT groups may be explained by a higher presence of artefacts. For the majority of the primary morphometric parameters of the sperm head and the acrosomal area, the relationship between treatments was the following: GLUT> HEM≥ MET≥ SB> DRY. When studying the proportion of the sperm head covered by the acrosome, the relation between treatments was: MET> DRY = GLUT = SB> HEM. It was concluded that the new method for sperm morphometric assessment allows the simultaneous assessment of sperm head and acrosome in the ram by the first time, even in unprocessed semen smears.     

Influence of the FecXR Allele in Heterozygous Ewes on Follicular Population and Outcomes of IVP and ET using LOPU‐Derived Oocytes

Ewes heterozygous for the FecX^R allele (R+) in the bone morphogenetic protein 15 (BMP15) gene display increased ovulation rate and prolificacy. Besides this phenotypic advantage, the influence of the FecX^R allele on follicle number and size, oocyte competence and in vitro production (IVP) remains undefined. With these aims, 8 R+ and 8 wild‐type (++) ewes were subjected to 2 laparoscopic ovum pick‐up (LOPU) trials (four sessions per trial; two with and two without FSH) and subsequent IVP and fresh embryo transfer. All follicles >3 mm were punctured (n = 1673). Genotype did not significantly affect the number of punctured follicles per ewe and session (10.4 and 10.2 in R+ and ++ untreated ewes, 17.4 and 14.3 in R+ and ++ FSH‐treated ewes, respectively), but follicular diameter of R+ ewes was significantly reduced compared with ++ ewes (?0.2 mm in untreated and ?0.8 mm in FSH‐treated ewes; p < 0.01). R+ ewes showed higher recovery rate and increased numbers of total and suitable cumulus–oocyte complexes for in vitro maturation (IVM). Similar rates of day 8 blastocysts were observed in R+ (36.1%, 147/407) and ++ (32.6%, 100/307) ewes, but the final output of day 8 blastocysts per ewe and session was higher in R+ ewes (+0.75; p < 0.005), without differences in survival rate at birth of the transferred embryos (40.4%, 21/52 vs 36.4%, 16/44, respectively). In conclusion, a higher number of oocytes proven to be competent for in vitro development and embryo survival after transfer are recovered from R+ ewes, despite the lower mean size of their follicles at puncture.     

Spatial pattern formation in an insect host-parasitoid system

Spatial models in ecology predict that populations may form patchy distributions within continuous habitats, through strong predator-prey or host-parasitoid interactions combined with limited dispersal. Empirical support of these models is provided. Parasitoids emanating from a population outbreak of tussock moths (Orgyia vetusta) suppressed the growth of nearby experimental populations of the moth, while experimental populations farther away were able to grow. This result explains the observed localized nature of tussock moth outbreaks and illustrates how population distributions can be regulated by dynamic spatial processes.