Armoured bush cricket, Acanthoplus discoidalis (Walker) (Orthoptera: tettigoniidae) outbreak prediction using rainfall patterns in three zones of Botswana

Based on a quantitative understanding of the environmental factors effecting armoured bush cricket, Acanthoplus discoidalis population dynamics, a hypothesis was formulated to explain the occurrence of outbreaks in some years and locations. The principles, expressed using a rule-based or qualitative model, were that nymph and adult survival and fecundity were reduced in years with uneven rainfall and that egg survival was reduced in years with a wet late-season as this is associated with increased egg predation and/or water-logging. The implication was that large egg banks resulted either when a large number of adults were present or when neither low fecundity nor high egg mortality were constraints. Such large egg banks were however predicted only to lead to outbreaks when there was an adequate amount of food for nymph and adult survival in the following season. Model predictions were compared with observed outbreaks of A. discoidalis between 1988 to 2002 for the three climatic zones of the east, central and western parts of southern Botswana. There was significant agreement between model predictions and observed outbreaks in two of the three zones (95% confidence interval of the kappa coefficient of agreement > 0). Taking the data for all three zones together and compared to the average outbreak frequency, an outbreak was three times more likely to occur when the model predicted an outbreak and six times less likely to occur when it predicted no outbreak.

Live birth and clinical outcome of vitrification-warming donor oocyte programme: an experience of a single IVF unit

Summary Medically assisted reproductive (MAR) treatments using donated oocytes are commonly applied in several countries to treat women who cannot conceive with their own gametes. Historically, in Italy, gamete donation has been prohibited but, in 2014, the law changed and gamete donation became allowed for couples undergoing MAR treatments. Consequently, in the last decade, there has been an increase in application of the oocyte donation programme. This study reports an egg-donation programme’s clinical efficacy, based on importing donated vitrified oocytes from cryo-banks located in a foreign country. For this, we conducted a retrospective analysis of data from a single reproductive unit located in Italy (Donna Salus Women’s Health and Fertility, Bozen). The study group consisted of 681 vitrified oocytes, which were warmed and culture to be replaced in 100 recipients. The survival rate after warming was 79.1% (n = 539/681), whereas the fertilization and blastulation rates were 90.2% (n = 486/539) and 47.9% (n = 233/486), respectively. Positive pregnancy test, clinical pregnancy rates, and live-birth rates per embryo transfer were 37.8%, 31.1% and 28.4%, respectively. The multiple pregnancy rate was 0.7%. This study is one of the first to report on the efficacy of a donor oocyte programme in Italy using imported vitrified oocytes. The above data may reassure women who are undertaking donation programmes using vitrified oocytes imported from commercial egg banks.

Spatial variation of ostracod (Crustacea, Ostracoda) egg banks in temporary lakes of a tropical flood plain

Ostracods are microcrustaceans that produce resting eggs under adverse conditions. In this study we evaluated the spatial variation of ostracod resting eggs in different regions of temporary lakes in a Brazilian flood plain. Based on the homogenisation effect of flood pulses on aquatic communities in flood plains, we hypothesised that the composition and abundance of ostracod eggs in the centre of temporary lakes would be similar to those in edge regions. Samples were collected from the centre and edge regions of five temporary lakes. Sediment was oven dried, rehydrated and hatching was monitored in germinating chambers. Twelve ostracod species hatched from the egg banks during our experiments. The abundance and species composition were similar between the two regions of the lakes. Flood events may be responsible for the homogenisation of the egg banks as a result of the connection of lakes with principal river channels. During flooding, water masses powerfully enter lakes and can redistribute sediments. This study shows that egg banks have the potential to contribute to the maintenance of local biodiversity and the resilience of biodiversity of temporary lake ecosystems.

Cladocera resting egg banks in temporary and permanent wetlands

Cladocerans are important filter-feeders transferring energy up the food web to different invertebrate and vertebrate predators. Along the flood period, cladocerans are one of the primary food sources for juvenile fish in floodplain. Resting egg banks allow cladoceran populations to overcome the environmental stress, related to several limnological changes, including complete drying of temporary wetlands. After drought, resting egg banks influence cladoceran community attributes during the cyclic and successional processes driven by episodic flood events. In this study we compared the taxonomic richness of active (from the water column) and dormant (from the sediment) Cladocera assemblages and analyzed the structure of resting egg banks, comparing the diversity, abundance and apparent viability/unviability of the eggs, between six temporary and six permanent wetlands, located along the Ovens River Floodplain, Victoria, Australia. The qualitative analysis shows higher taxonomic richness in active assemblages from temporary (24 taxa) than permanent (13 taxa) wetlands compared to dormant assemblages present in resting egg banks (9 taxa) from temporary and permanent wetlands. However, richness was influenced by taxonomic level of identification, with the majority of resting eggs only being identified to the taxonomic level of family (i.e. Chydoridae). Total taxa richness within egg banks was similar between wetland types, however, on average higher Shannon’s diversity of resting eggs was found within permanent (1.53) than temporary (0.82) wetlands. This is likely to be due to more stable wetlands not providing appropriate cues to trigger dormancy induction or breakage for specific populations, leading to higher values of evenness in permanent than temporary wetlands. Comparing permanent and temporary wetlands, higher abundance of resting eggs (more than four times) consisting of higher abundance of unviable eggs and similar viable egg abundance to permanent wetlands, was found within temporary wetlands, suggesting that the increased resting egg abundance in temporary wetlands is balanced by the losses due to factors such as predation, parasitism or other physical damage, during the terrestrial phase. Despite resistant outer shell structure, this study highlights that the damage to egg integrity is intensified in wetlands that undergo dry phases. Cladoceran resting egg banks represent the potential assemblage to recover after disturbance events such as drying, and information about these is important to ensure appropriate management and conservation of floodplain biodiversity.

Daphnia laevis ephippia cemetery in the sediment of a permanent tropical lake

Aiming to evaluate the importance of egg banks from a tropical lake for the active Daphnia laevis dynamics, we investigated ephippia down to a 28-cm sediment depth, and used data obtained by traps to compare with the in situ production and hatching rates of fresh ephippia. All the ephippia from the sediment were opened for inspection of the presence of resting eggs, and those found were incubated to verify hatching. Ephippia density degradation rate was tested by putting isolated ephippia immersed in the sediment lake for 75 days, and found to exponentially decrease with increasing sediment depth. Higher densities were recorded in 2017 (maximum of 1.43 ephippia per cm2) than in 2016 (maximum of 0.8 ephippia per cm2). The empty ephippia rates were high in all sediment depths ranging from 83% to 100%. In contrast, the hatching rates in situ of fresh ephippia were high, suggesting that those that sink are mostly unviable or empty, forming an unusual egg bank in the sediment. In the laboratory, ephippia degradation signs were observed as early as the fifteenth day after contact with sediment. We conclude that the egg bank is not able to support an active population since most of the ephippia are empty and also rapidly degrade in sediment. Our results contribute to the current understanding of diapause in tropical cladocerans, demonstrating that the presence of Daphnia ephippia in the sediment of permanent lakes do not always correspond to an egg bank for temporal dispersion.