The effect of climate change on an aphid–coccinellid interaction

A model (Carter et al. 1982) that described the population dynamics of Sitobion avenae was modified and extended to include the population dynamics of the aphidophagous coccinellid, Coccinella septempunctata. The model was run under three different temperature regimes, corresponding to different degrees of warmth in typical English summers, and, in addition, within-regime temperature was altered, to predict the likely effects of climatic change on the interaction between the aphid and coccinellid. The model predicts that the presence of coccinellids causes a reduction in the number of aphids of between 40 and 60 percent, and advances the Julian date of their maximum numbers. The model also predicts that an increase in temperature within a regime results in smaller maximum and total numbers of aphids. In the presence of coccinellids, aphids were predicted to be most successful in moderately warm summers. The predicted maximum number of coccinellids was not greatly affected by temperature, but their total number was, in a complex way. The greatest effect of coccinellids to reduce both maximum and total aphid numbers was predicted to occur for relatively hot summers. A sensitivity analysis was used to identify those aspects of the coccinellid submodel that require possible refinement.     

The Heart Ultrastructure in Two Species of Pycnogonids, and its Phylogenetic Implications

The heart of the pycnogonids Nymphon (Chaetonymphon) macronyx G. O. Sars and Boreonymphon cf. abyssorum Norman is pseudotubular and lacks an epicardium and an endocardium. The body wall forms the roof over the heart lumen. The myocardium is innvervated, and forms the lateral walls of the heart. Myofibres are absent in the midventral floor. This part is formed by cells of the horizontal septum attached to the gut complex. The myofibres are short. Interdigitating intercalated discs have not been observed, but lateral overlaps are common. Z-, I- and A-bands are seen in the sarcomere. The 2-bands are diffuse and irregular. The sarcolemma invaginates and forms a sparse system of clefts; a poorly developed T-system is indicated. Its presence supports the view that a T-system is inherent in the arthropod myocardium. Couplings are not related to any specific sarcomere band level. It is implied that the thin-walled pseudotubular heart in pycnogonids is a result of a reduction, and that it functions more like a channel than a heart.     

A field trial to assess the effects of rabbit grazing on spring barley

Spring barley is widely grown throughout the UK and significant yield loss can occur as a result of rabbit grazing. In a 3-yr trial, spring barley was grown in six enclosures following current agronomic procedures and was subjected to grazing by different population densities of rabbits. The annual yield loss at the end of the trial was 0.5% rabbit⁻¹ ha⁻¹. The yield loss per rabbit was calculated to be around 25 kg and the financial loss was calculated as £2.00 per rabbit at 1998 prices (approx. £80 tonne⁻¹). Models allowing farmers to predict the levels and costs of damage by rabbits to winter wheat and for silage have already been developed. The results from this trial enable farmers to extend their predictions to include spring barley. The implications for this are discussed.     

Historic and current habitat use by North Pacific right whales Eubalaena japonica in the Bering Sea and Gulf of Alaska

1. To help define areas and ecological parameters critical to the survival and recovery of the remnant population of North Pacific right whales, habitat use was investigated by examining all available sighting and catch records in the south-eastern Bering Sea (SEBS) and Gulf of Alaska (GOA) over the past two centuries. 2. Based on re-analyses of commercial whaling records, search effort, and resultant catches and sightings, waters of the: (i) SEBS slope and shelf, (ii) eastern Aleutian Islands and (iii) GOA slope and abyssal plain were important habitat for North Pacific right whales through the late 1960s. 3. Since 1980, the only area where right whales have been seen consistently is on the SEBS middle shelf. However, acoustic detections and single sightings have been reported in all other regions except the SEBS slope and oceanic GOA (areas where little, if any, acoustic and visual effort has occurred). 4. Sightings since 1979 were in waters < 200 m deep which may simply reflect the paucity of search effort elsewhere. From the commercial whaling era to the late 1960s, right whales were commonly seen in waters > 2000 m deep, indicating that their distribution is not restricted to shallow continental shelves. 5. North Pacific right whale sightings through the centuries have been associated with a variety of oceanic features, and there is little in common in the bathymetry of these regions. These whales appear to have a greater pelagic distribution than that observed in the North Atlantic, which may be related to the availability of larger copepods across the SEBS and GOA.     

Evidence for an H-Y Crossreactive Antigen in Invertebrates

A sex specific antigen which crossreacts with the mammalian H-Y antigen has been identified on the cell surface of hemocytes from the lobster ( Homarus americanus ) and the gonadal cells of three insect species. The hemocytes from the male lobster, the testicular cells from the male beetle ( P. cornutus ), and the ovarian cells from two Orthopteran species ( L. maderae and D. punctata ) specifically absorbed H-Y antibodies. The specificity of H-Y antibody absorptions by cells from only one sex, suggest that an ancestral H-Y-like antigen may be present in invertebrates which could be engaged in sexual (cellular) recognition events.     

Studies on death of deteriorated barley seeds in soil

Seeds of barley cv. Golden Promise which had been deteriorated by storing at 20% moisture content and 30 °C and which all had viabilities >85% were treated with a slurry of calcium peroxide and with dusts of a mercurial and a non-mercurial fungicide. Calcium peroxide improved seedling emergence in wet soil conditions and deteriorated seeds benefited more than non-deteriorated seeds. The fungicide dusts had no effects. In controlled conditions at 20 °C, deteriorated seeds in wet soil died mainly within 2 days of sowing and they were more tolerant if they were placed in moist soil for 2 days before transfer to wet soil. Application of a mercurial fungicide and sterilizing the soil and the surface of seeds improved emergence but did not restore it to the level in moist soil. Fusarium culmorum, F. equiseti, Mucor spp. and Mortierella spp. dominated the fungus flora isolated from surface sterilised dead seeds in wet soil. When the fungi were inoculated to seeds, they increased the proportion which died in wet soil but only at high inoculum levels. It was concluded that they acted primarily as saprophytes depriving seeds of oxygen and secondarily as seed colonisers.