Determinism of the induction of the reproductive cycle in female Eurasian perch, Perca fluviatilis: Identification of environmental cues and permissive factors

In Eurasian perch, Perca fluviatilis, gametogenesis is induced by decrease of both temperature and photoperiod. However, a multiplicity of other factors can display non-permissive or modulating effects on the induction of the reproductive cycle. Consequently, a 9-week study was carried out to determine the environmental cues and permissive factors controlling the induction of the reproductive cycle in this species. A two-level fractional factorial design 2^8-4 was used in order to identify the influent factors from 8 environmental and nutritional ones and their 28 interactions. Tested factors were: (1) amplitude of temperature decrease, (2) time, (3) kinetics and (4) amplitude of photoperiod decrease, (5) initial nutritional state, (6) handling, (7) feeding rate and (8) light spectrum. Increase of gonadosomatic index (GSIi), proportion of female in exogenous vitellogenesis (EVP), plasma 17 β-estradiol (E₂) and cortisol levels, fat consumption and food intake were evaluated.This study showed that the amplitude of the decrease of temperature and the time of photoperiod decrease are the two main environmental cues controlling the induction of the reproductive cycle in Eurasian perch. GSIi was the highest (3.8%) when females were exposed to both low amplitude of temperature decrease and precocious decrease of photophase. It was the lowest (1.1%) when high amplitude of temperature decrease and late decrease of photophase were applied. Handling in association with temperature modulated the broodstock response. 100% of the unhandled fish held at 14 °C were at the exogenous vitellogenesis stage with mean E₂ and basal cortisol levels of 1.6 ng mL^− 1 and 9 ng mL^− 1 respectively. Handled fish and fish held at 6 °C exhibited lower vitellogenesis (40-73%) associated with lower E₂ (0.6-1.1 ng mL^− 1) and higher basal cortisol levels (37-89 ng mL^− 1). No other factor nor interaction displayed a cueing or non permissive effect on the induction of the reproductive cycle in female Eurasian perch. A first schematic model is proposed to explain the factorial determinism of the induction of the reproductive cycle.     

Historical processes and landscape context influence genetic structure in peripheral populations of the collared lizard (<Emphasis Type="Italic">Crotaphytus collaris</Emphasis>)

Populations at the periphery of a species’ range often show reduced genetic variability within populations and increased genetic divergence among populations compared to those at the core, but the mechanisms that give rise to this core-periphery pattern in genetic structure can be multifaceted. Peripheral population characteristics may be a product of historical processes, such as founder effects or population expansion, or due to the contemporary influence of landscape context on gene flow. We sampled collared lizards (Crotaphytus collaris) at four locations within the northern Flint Hills of Kansas, which is at the northern periphery of their range, to determine the genetic variability and extent of genetic divergence among populations for ten microsatellite loci (n = 229). We found low genetic variability (average allelic richness = 3.37 ± 0.23 SE; average heterozygosity = 0.54 ± 0.05 SE) and moderate population divergence (average F_ST = 0.08 ± 0.01 SE) among our sample sites relative to estimates reported in the literature at the core of the species’ range in Texas. We also identified differences in dispersal rates among sampling locations. Gene flow within the Flint Hills was thus greater than for other peripheral populations of collared lizards, such as the Missouri glade system where most of the mesic grasslands have been converted to forest since the last glacial retreat, which appears to have greatly impeded gene flow among populations. Our findings signify the importance of considering landscape context when evaluating core-peripheral trends in genetic diversity and population structure.     

Efficacy of acaricides against chorioptic mange of goats

Angora goats heavily infested with Chorioptes bovis were dipped one time in either 0.05% amitraz, 0.27% coumaphos, 0.05% fenvalerate, or 0.03% lindane. Control of the mites by the single dips was evaluated for 21 days. Amitraz caused 98% mortality of the mites initially. Both coumaphos and lindane caused greater than 85% mortality at 3 days, but mite numbers increased rapidly thereafter. Only fenvalerate killed all of the mites.     

Effect of ivermectin in heifers on mortality and egg production of Psoroptes ovis

Ten stanchioned heifers, heavily infested with Psoroptes ovis (Hering), were each given a single subcutaneous injection of 200 micrograms of ivermectin/kg. Another 10 heavily infested heifers (stanchioned) were injected subcutaneously with the solvent system (vehicle) used to formulate the ivermectin. Treatment with the vehicle did not reduce mite populations or total egg counts. The 10 heifers treated with ivermectin had an immediate reduction in live mite and egg counts (an increase in the percentage of mortality of mites) and were completely free of psoroptic mites by 20 days after treatment. Ivermectin was equally effective against adult and immature psoroptic mites.     

Development and transmission of psoroptic mange of cattle in feed lots in endemic and non-endemic regions

A test was begun in November 1982 to evaluate the development of Psoroptes ovis, the severity of psoroptic mange of cattle, and the incidence of transfer of P. ovis from artificially infested cattle to non-infested cattle held in feed lots in either an endemic (Bushland, TX) or non-endemic region (Kerrville, TX). The 2 herds each consisted of 24 Hereford steers. The 24 steers were randomly assigned to 3 pens of 8 steers per pen. Two steers from each pen that were randomly selected were artificially exposed to ca. 1000 P. ovis (AINF). The development of mange on these 6 AINF steers and the incidence of transfer to the other steers (INF) were monitored approximately every 3 weeks for 17 weeks. The 6 AINF steers at Bushland (endemic region) developed significantly more lesions than the 6 AINF steers at Kerrville. Three AINF steers in Bushland died from hypothermia and mange while no deaths were recorded at Kerrville. The numbers of mites sampled from affected skin areas of AINF steers from both regions were not significantly different. All 18 of the naturally exposed steers (INF) in Bushland contracted mange; whereas, only 9 INF steers in Kerrville did. The severity (% lesions) and number of mites per sample from affected skin were significantly greater on the INF steers in Bushland. These differences among INF steers in Bushland and Kerrville may be attributed to the higher level of parasitism attained in Bushland on the AINF steers. We propose that the extremely cold weather in Bushland contributed to the greater level of parasitism attained on AINF steers in Bushland by stressing the host steers.     

Pulp in Shop-Bought Orange Juice Has Little Effect on Flavonoid Content and Gut Bacterial Flavanone Degradation In Vitro

Orange juice is an important source of flavanones in the Western diet. However, little is known of the variation in flavanone content of shop-bought orange juice with pulp (OJP) or without pulp (OJ), nor the impact of pulp on the fate of flavanones in the gut. Total phenols, total flavonoids, antioxidant capacity, hesperidin and narirutin, and dietary fibre were measured in six orange juice brands sold as OJP and OJ. The inclusion of pulp had little impact on fibre content. Apart from total phenols (OJ: 208.4?±?10.7 μg gallic acid equivalents (GAE) ml^?1; OJP: 225.9?±?16.7 μg GAE ml^?1, P?<?0.05), there were no differences between OJ and OJP. The fate of flavanones in OJ and OJP (Tropicana) were further compared using in vitro gastrointestinal (GI) models. After in vitro upper GI digestion, recovery of hesperidin was higher in OJ compared with OJP (89?±?6 vs. 68?±?3%, P?=?0.033). After 2 h colonic fermentation, hesperidin was 1.2 fold higher in OJP than OJ. However, after 24 h colonic fermentation there was no significant difference between juices in terms of hesperidin, hesperetin, narirutin, naringenin and catabolites. In conclusion, the amount of pulp included in these shop-bought orange juices had little impact on flavanone metabolism in models of the GI tract. The effects of greater amounts of orange pulp remain to be determined.