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.     

柔嫩艾美耳球虫感染对鸡肠炎沙门氏菌感染复发的影响

本研究揭示了柔嫩艾美耳球虫感染可以引起鸡肠炎沙门氏菌感染的复发。复发的主要表现为盲肠内容物的肠炎沙门氏菌阳性率和数量再次显著地升高;肠炎沙门氏菌在盲肠中的滞留时间显著延长。这种复发与肠炎沙门氏菌的初始感染量及球虫感染时间有关。肝脏和脾脏阳性率无显著变化。     

Nasal Shedding of Equid Herpesvirus Type 1 and Type 4 in Hospitalized,Febrile Horses

The objective of this study was to determine the prevalence of shedding of equid herpesvirus 1 (EHV-1) or EHV-4 in nasal swab samples from any febrile, hospitalized horses during a 1-year period. It was hypothesized that some fevers in horses are associated with viral replication following recrudescence of latent virus or following a horizontal viral infection prior to or during admission to a referral hospital. During the observational period, nasal swab samples were collected from 64 febrile and 10 nonfebrile hospitalized horses. Routine DNA extraction was performed, and a validated quantitative polymerase chain reaction (qPCR) assay was used to detect and quantify genomic EHV-1 and -4 DNA. Genomic DNA of EHV-4 was detected in the nasal swab specimen of 1 of 64 febrile horses. EHV-1 DNA was not detected in any of the febrile horses. Samples from all nonfebrile horses were negative for both viruses. Considering the known association between fever and shedding of EHV-1 and EHV-4, we anticipated finding a higher percentage of PCR-positive samples from febrile patients. Fevers detected were likely a result of active disease processes for which the horses were hospitalized; concurrent other diseases appeared not to affect viral recrudescence. Further studies are warranted to examine frequency and factors of EHV latency and reactivation.     

The Relative Position of the Penis in Southern African Dassies (Hydracoidea) as a Character of Taxonomic Importance

Histological examination of gametogenesis revealed that the current staging criteria used to assess gonadal recrudescence of the redeye labeo, Labeo cylindricus, were adequate. Gametogenesis was qualitatively similar to thatof freshwater teleosts with a clearly defined seasonal reproductive cycle. L. cylindricus undergoes seasonal gross morphological and cytological gonadal changes with previtellogenesis dominating during the winter, vitellogenicdevelopment during spring and summer culminating in large-scale spawning at the end of summer. Post-spawning mass atresiaofoocytes was evident in autumn. The histological data presented support macroscopical evidence that L. cylindricus is a synchronous iteroparous spawner, reproducing over a short period each year throughout its life-span.     

Testicular histomorphometry and the proliferative and apoptotic activities of the seminiferous epithelium in Syrian hamster during spontaneous recrudescence after exposure to short photoperiod

Syrian hamsters are photoperiodic rodents in which reproduction, including testicular function, is stimulated by long photoperiod exposure and curtailed by exposure to a short photoperiod. The objectives of this study were to characterize the testis histomorphometrically and to determine the role of the proliferation and apoptosis phenomena in the recovery of the seminiferous epithelium during spontaneous recrudescence after exposure to short photoperiod. The study was performed using conventional light microscopy, proliferating cell nuclear antigen and terminal deoxynucleotidyl transferase (TdT)‐mediated dUTP in situ nick end labelling staining, image analysis software, and transmission electron microscopy in three recrudescence groups: initial recrudescence (IR), advanced recrudescence (AR) and total recrudescence (TR). The results morphometrically pointed to the gradual recovery of the testicular and tubular volumes, as well as of the seminiferous epithelium. Among the IR and AR groups, the increase in testicular and tubular volumes was accompanied by an increase in tubular diameter and length, with an increase in interstitial volume. From AR to TR, there was an increase in the tubular and total volumes, but, in this case, with a gradual increase in tubular diameter. Recovery of the seminiferous epithelium was accompanied by changes in apoptosis and proliferation activities. The first decreased halfway through the process, and the second remained higher than the control levels throughout the recrudescence stage. Alterations in the spermatozoa were ultrastructurally observed, which indicated that spermiogenesis was not yet completely normal. In conclusion, spontaneous testicular recrudescence in Syrian hamster comprises two histomorphometrical phases: the first related to an increase in tubular length and diameter and interstitial volume and the second depending principally on the gradual increase in tubular diameter. The restoration of the seminiferous epithelium is due to apoptosis reaching normal values in the AR group accompanied by higher proliferative activity than that observed in the Control group.     

福美砷悬浮剂防治苹果树腐烂病疤复发药效试验

田间试验表明，40％福美砷悬浮剂对苹果树腐烂病疤复发有良好的防治效果，120mL／m^2次，防效84．6％—92．3％。与同剂量可湿性粉剂相比，悬浮剂有增效作用。     

Anuran Ecology in Relation Particularly to Oviposition and Development out of Water

This paper is a contribution to the poorly known subject of wild rodent behaviour. Observations were conducted in the field and laboratory on the vlei rat, Otomys irroratus, as part of a comprehensive study of its ecology and life history.

Individual behaviour, social behaviour, and post natal development are described and discussed. It was found that the vlei rat is very shy and retiring in captivity. It can be considered as crepuscular, but activity tests conducted in the field and laboratory indicated some activity throughout the day and night.

Interactions of adults were tested and they were found to be very antisocial, with intrasexual aggression occurring when caged. Complex threat and communication patterns exist, a feature of asocial behaviour. Mating failed to occur in captivity, probably also a result of their antisocial nature.

Marking behaviour is very distinctive in this species and, combined with urination and possibly defecation, would appear to be useful in delimiting territories. It is concluded from their social habits, marking behaviour, and considerable overlap of home ranges that in nature their interactions with conspecifics are represented by a dominance hierarchy.

Several litters of young were reared. They are very precocial at birth and development proceeds rapidly. At birth the incisors are erupted, enabling them to cling firmly to the nipples of the mother. Most adult behaviour patterns are developed before weaning at 13 days.     

Gonadal recrudescence and induced spawning in Barbus altianalis

Gonadal recrudescence in Barbus altianalis from River Nile, Jinja (33°05E; 0°45N) Uganda was studied prior to induced spawning. Oocytes in B. altianalis were found to develop in cohorts suggesting batch spawning throughout the year with pronounced spawning activities coinciding with rainfall peaks of April and September. There was a strong positive correlation between rainfall and gonadosomatic index (r_S = 0.75, P = 0.008). B. altianalis had low fecundity (6.0 ± 2.0 per gram) and large‐sized eggs (2.97 ± 0.1 mm). Induced spawning was successful with exogenous hormones and water current. Results from this study suggested that total striping may not be appropriate, but larger eggs would confer high survival of offsprings under optimal conditions. The success registered in induced spawning of B. altianalis provides a breakthrough in seed production for multiplication and culture of this economically important fish species.