Low Infestation Rates Research Articles

A Relationship Between Avian Foraging Behavior and Infestation by Trombiculid Larvae (Acari) in Chiapas, Mexico

ABSTRACTBirds face varying risk from parasites as they select and utilize habitat. Unfortunately, behavioral and habitat correlates of parasitism in birds are not well documented. This study combines data from a foraging behavior study with results from a banding study to test whether behavior and habitat affect an ectoparasite infestation by trombiculid mite (chigger) larvae on the bird community found in two different coffee agroecosystems in Chiapas, Mexico. Individuals from bird species with regular prevalence (i.e., infestation) foraged more frequently in lower vegetative layers and had significantly lower foraging height than those from species with little or no prevalence, suggesting that foraging near the ground increases exposure risk to chigger larvae. Using linear regression, across species, parasite prevalence decreased with increasing average foraging height. Lower infestation rates were found in coffee agroecosystems with higher management intensity (i.e., less shade and drier conditions), suggesting that management activities influence infestation rates. Consequently, drier tropical habitats may pose less risk to birds from ectoparasites, though seasonal prevalence was highest during the winter dry season. Although no direct link was found between host condition and infestation by chigger larvae on the wintering grounds, birds were sampled during the middle of the over‐wintering period, not the end when infestation could affect birds fattening for migration.

Thresholds and Management Strategies for <I>Aulacorthum solani</I> (Hemiptera: Aphididae) in Greenhouse Pepper

Economic injury level (EIL) and economic threshold (ET) were established for Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae) in greenhouse pepper, Capsicum annuum L. The high toxicity of the salivary secretion of A. solani produces deformation and decoloration of leaves, complete plant defoliation, and unmarketable deformed fruits at high densities. Low, high and null infestation rate treatments provided a broad range of population densities to determine the relationship between yield and the cumulative A. solani-days (CAD). In all infested compartments, A. solani reached a very high population density that eventually produced the complete defoliation of the plants and losses in total and marketable yield. At low A. solani density, pepper plants showed a tolerance response. Generalized Additive Models (GAM) and Gompertz equation were used to determine the relationship between yield and CAD. Both models explained a high proportion of the variance and described well the relationship between the two variables. However, GAM predicted the tolerance phase of the yield-CAD relationship more satisfactorily. The theoretical damage curve predicted by GAM describes a tolerance, compensation and a linearity part. EIL was estimated at 57 CAD. ET was established at 20 CAD to prevent aphid density from reaching EIL within the gap between sampling periods.

Fish parasites in the Arctic deep-sea: Poor diversity in pelagic fish species vs. heavy parasite load in a demersal fish

A total of 219 deep-sea fishes belonging to five families were examined for the parasite fauna and stomach contents. The demersal fish Macrourus berglax, bathypelagic Bathylagus euryops, and mesopelagic Argentina silus, Borostomias antarcticus, Chauliodus sloani, and Lampanyctus macdonaldi were caught at 243–708 m trawling depth in the Greenland and the Irminger Sea in 2002. A total of 21 different parasite species, six Digenea, one Monogenea, two Cestoda, seven Nematoda, one Acanthocephala, and four Crustacea, were found. The parasite diversity in the meso- and bathypelagic environment was less diverse in comparison to the benthal. Macrourus berglax had the highest diversity (20 species), usually carrying 4–10 different parasite species (mean 7.1), whereas Bathylagus euryops harbored up to three and Argentina silus, Borostomias antarcticus, Chauliodus sloani and Lampanyctus macdonaldi each up to two species. Most Digenea, Cestoda, Nematoda, Acanthocephala, and Crustacea are known from a wide host range. Several of the encountered parasites occurred at a very low prevalence (<10%), indicating that the studied deep-sea fishes are most probably not instrumental to complete the parasite life cycles in the area of investigation. It is suggested that the lack of nutrients in the meso- and bathypelagial limits the abundance of potential first intermediate hosts of nematodes and cestodes, resulting in low infestation rates even of widely distributed, non-specific species. In contrast, the higher biomass in the benthic deep-sea environment increases the availability of potential intermediate hosts, such as molluscs for the digeneans, resulting in increased parasite diversity. Because many deep-sea fish have a generalistic feeding behavior, the observed different parasite diversity reflects a different depth range of the fish and not necessarily a specific fish feeding ecology.

Variation of the response of clonal cocoa to attack by cocoa pod borer Conopomorpha cramerella (Lepidoptera: Gracillariidae) in Sabah

Eight cocoa clones were examined for variation in resistance to cocoa pod borer ( Conopormorpha cramerella Sn) in Sabah, Malaysia. Over a 13 month period up to 1200 ripe pods of each were shaved back to the sclerotic layer and the number of larval entry and exit holes were counted. There were statistically significant differences in the proportion of larvae that were able to exit, with PBC123, a popular commercial clone in Sabah, and IMC23 is more resistant than BAL244 and KKM22. The six more resistant clones were characterized for pod hardness, using a penetrometer. The correlation with the entry/exit ratio suggested that the measurements could be used for screening clones for resistance. The data indicated that at relatively low rates of infestation, the proportion of larvae that can exit from the pods is negatively correlated with the number that enter, which would amplify the effect of partial resistance. The partial resistance of PBC123 may be sufficient to greatly reduce moth populations in a large enough pure stand of the clone. Pod borer resistance should be given a high weighting in an economic index for cocoa clone selection, and should be combined with tolerance of infestation in the form of low damage to the cocoa beans despite infestation.

Risk factors associated with house infestation by the Chagas disease vector Triatoma pallidipennis in Cuernavaca metropolitan area, Mexico

Chagas disease caused by infection with Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae) is widespread in Mexico, transmitted by various triatomine bugs (Hemiptera: Reduviidae). The only domestic vector in Cuernavaca (population 650 000) is Triatoma pallidipennis (Ståhl) with T. cruzi seroprevalence ranging from 1% to 9% in the resident human population. We surveyed possible risk factors for T. pallidipennis infestation at Cuernavaca (altitude 1200-2200 m) on south-western slopes of the Sierra Madre Occidental. This metropolitan area (with five administrative counties) has rapid urbanization, forested environs and proliferation of 'weekend housing' for visitors from Mexico City, 60 km to the north. To assess factors associated with T. pallidipennis infestation, we first stratified Cuernavaca by altitude and by socio-economic status of population catchment units (PCUs). Within each PCU, one to three blocks were chosen for cluster sampling (three houses/block) and information about Chagas disease was distributed. After obtaining signed consent from householders, representative houses were routinely and opportunistically inspected for T. pallidipennis and surveyed for demographic, economic, physical and other potential risk factors. Of the 1129 houses assessed, T. pallidipennis was found in 4.1% (range 3.0-6.8% per county) and the T. cruzi infection rate was approximately 50% in bugs. Rates of house infestation in poor PCUs were double those in higher socio-economic strata (odds ratio 2.12, confidence interval 1.03-4.3), with >4-fold greater crowding index of T. pallidipennis. The bug density index was inversely correlated with PCU altitude and socio-economic category (altitude of homes being associated with prosperity), while the bug colonization index (presence of nymphs indicating breeding) did not vary significantly across the PCU categories, but did vary according to altitude. Multivariate regression analysis showed that the most significant risk factors associated with T. pallidipennis infestation were lower altitude (linked with lower socio-economic status), garden area >80 m(2), dogs at liberty to enter the house, occurrence of squirrels and opossums around the house, presence of pigs in the surrounding area and having at least one of the adjacent lots empty (unconstructed). Householders who had received information about Chagas disease comprised 33% from infested houses (14/42) but only 15% from non-infested houses (148/984). Hence, the awareness of Chagas disease was significantly associated with having a bug-free house (P < 0.01). When shown specimens of T. pallidipennis, the proportions of householders who recognized them were 78% from infested houses but only 29% of those with uninfested houses. Given the low infestation rates and the high capacity of the population to act appropriately once they have received information regarding this disease and its vector, relevant health education is expected to have a significant impact on triatomine control in this metropolitan area.

Moscas ectoparasitas (Diptera, Streblidae) de morcegos (Chiroptera, Phyllostomidae) no sul do Brasil: associações hospedeiros-parasitos e taxas de infestação

As associações hospedeiros-parasitos e as taxas de infestação de dípteros ectoparasitos da família Streblidae foram estudadas em morcegos da família Phyllostomidae na Floresta Atlântica no extremo sul do Brasil. Para as espécies mais abundantes de filostomídeos, foi examinado se há diferenças nos valores de prevalência e intensidade média dos ectoparasitos nas diferentes estações do ano e conforme sexo e idade do hospedeiro. Em quatro espécies de filostomídeos (Anoura caudifera (E. Geoffroy, 1818), Artibeus fimbriatus Gray, 1838, Artibeus lituratus (Olfers, 1818) e Sturnira lilium E. Geoffroy, 1810) foram coletados 118 indivíduos de sete espécies de Streblidae (Anastrebla caudiferae Wenzel, 1976, Megistopoda aranea (Coquillett, 1899), Megistopoda proxima (Séguy, 1926), Metelasmus pseudopterus Coquillett, 1907, Paratrichobius longicrus (Miranda Ribeiro, 1907), Trichobius phyllostomae Kessel, 1925 e Trichobius tiptoni Wenzel, 1976). Para A. lituratus, A. fimbriatus e S. lilium, as taxas de infestação foram baixas e houve uma tendência à infestação ser maior no verão e outono, fato provavelmente relacionado à sazonalidade de temperatura na região, que afeta as taxas reprodutivas e a mortalidade dos ectoparasitos. A infestação por P. longicrus em A. lituratus não foi afetada pelo sexo e idade do hospedeiro. Para S. lilium, a infestação por M. proxima não foi afetada por sexo e idade do hospedeiro, com exceção da maior prevalência de ectoparasitos em indivíduos jovens. Os dados indicam que não existem diferenças comportamentais ligadas a sexo e idade do hospedeiro que favoreçam ou comprometam a infestação por Streblidae nestas espécies de morcegos filostomídeos.

Sero-epidemiological surveillance of hypodermosis in yaks and cattle in north China by ELISA

A large-scale serological surveillance was conducted for hypodermosis in the north of China. A total of 4175 sera samples of yaks and cattle were collected from five provinces in north China that included Xinjiang, Inner Mongolia, Heilongjiang, Jiling and Gansu provinces, between 2001 and 2002, and were examined for anti-hypoderma antibody by ELISA. The results indicate that the naturally infested positive rates of Hypoderma spp. in the above provinces were 51.77%, 27.02%, 13.00%, 6.03% and 44.41%, respectively. These results suggest a significant warble fly population in the north of China. Positive sera were collected from infested cattle in Pingliang county of the Gansu province monthly between August 2001 and July 2002. These sera were used to evaluate the seasonal kinetics of anti-hypoderma antibody. The kinetics demonstrated that anti-hypoderma antibody was elevated from October to December. Thus, serological surveillances associated with low infestation rates and chemical therapy would best be performed from October to December in the region.

Tritrophic Interaction of Parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae), Greenbug, Schizaphis graminum (Homoptera: Aphididae), and Greenbug-Resistant Sorghum Hybrids

Interactions of the parasitoid Lysiphlebus testaceipes (Cresson) and the greenbug, Schizaphis graminum (Rondani), on greenbug-resistant 'Cargill 607E' (antibiosis), 'Cargill 797' (primarily tolerance), and -susceptible 'Golden Harvest 510B' sorghum, Sorghum bicolor (L.) Moench, were tested using three levels of biotype I greenbug infestation. The parasitoid infestation rate was 0.5 female and 1.0 male L. testaceipes per plant. For all three greenbug infestation levels, the parasitoid brought the greenbug under control (i.e., prevented the greenbugs from killing the plants) on both resistant hybrids, but it did not prevent heavy leaf damage at the higher greenbug infestation rates. At the low greenbug infestation rate (50 greenbugs per resistant plant when parasitoids were introduced), greenbugs damaged 5 and 18% of the total leaf area on 'Cargill 797' and 'Cargill 607E', respectively, before greenbugs were eliminated. Leaf damage was higher for the intermediate infestation study (120 greenbugs per plant), 21% and 30% leaf area were damaged on the resistant sorghum hybrids 'Cargill 797' and 'Cargill 607E', respectively. At the high greenbug infestation rate (300 greenbugs per plant), heavy damage occurred: 61% on 'Cargill 607E' and 75% on 'Cargill 797'. The parasitoids did not control greenbugs on the susceptible sorghum hybrid 'Golden Harvest 510B'. L. testaceipes provided comparable control on both greenbug-resistant hybrids. This study supports previous studies indicating that L. testaceipes is effective in controlling greenbugs on sorghum with antibiosis resistance to greenbugs. Furthermore, new information is provided indicating that L. testaceipes is also effective in controlling greenbugs on a greenbug-tolerant hybrid.

Seasonal occurrence of sea lice Lepeophtheirus salmonis on sea trout in two north Norwegian fjords

Seasonal occurrence of the parasitic copepod Lepeophtheirus salmonis(sea lice) was studied from March to December 2001 in two large north Norwegian sill fjords without fish farming activity, the Ranafjord and the Balsfjord. Anadromous brown trout Salmo trutta(sea trout) in both fjords had a low infestation rate during all sampling periods, but followed a seasonal pattern. During early and late winter (November to December and March to April) and spring (May to June), the prevalence varied from 0 to 25% and the abundance was &lt;0·5 sea lice. Adults dominated (92%) during this period, particularly gravid females. In both fjords, the highest prevalence was during September (80–81%, all stages represented). In Ranafjord, the abundance and mean intensity during this month was 6·8 and 8·6 sea lice, respectively, while in Balsfjord it was 3·6 and 4·5 sea lice, respectively. Fish were captured at temperatures down to 1° C and at full strength sea water which is supposed to cause osmoregulatory problems for the fish. This observation has implications for the understanding of high‐latitude sea trout behaviour and can also make the fish more vulnerable to heavy sea lice infestation during this period. It is suggested that winter running sea trout help to maintain a self replicating local population of sea lice within such fjord systems where other possible hosts (e.g. farmed Atlantic salmon Salmo salar) are not present during a whole year cycle.

Control of Stored-Product Beetles with Combinations of Protein-Rich Pea Flour and Parasitoids

Protein-rich pea flour is toxic and repellent to three major stored-grain pests: the rice weevil, Sitophilus oryzae L.; the red flour beetle, Tribolium castaneum (Herbst); and the rusty grain beetle, Cryptolestes ferrugineus (Stephens). This study found that protein-rich pea flour was not toxic to, and did not reduce the offspring of, Anisopteromalus calandrae (Howard), a parasitoid of S. oryzae, nor did it reduce offspring of Cephalonomia waterstoni (Gahan), a parasitoid of C. ferrugineus. Protein-rich pea flour was also not repellent to A. calandrae. Small-scale and large-scale tests of a combination of protein-rich pea flour and parasitoids were conducted in 2-liter jars and in barrels containing 330 kg wheat. A larger population of A. calandrae was found at a high host infestation rate (24 adults/kg for 25 d), but the parasitoid did not become established at middle and low host infestation rates (2.4; 0.24 adults/kg for 25 d). The combinations of protein-rich pea flour and parasitoids reduced populations of S. oryzae in both tests. Additional effects of protein-rich pea flour and parasitoids were found in the large-scale test. Releasing parasitoids alone reduced the populations of S. oryzae by 46% and C. ferrugineus by 49%. Treating wheat with 0.04 or 0.1% protein-rich pea flour reduced the population of S. oryzae by 26 and 79% and C. ferrugineus by 27 and 43%, respectively. Combining parasitoids with 0.04 or 0.1% protein-rich pea flour reduced S. oryzae populations by 76 and 98% and C. ferrugineus populations by 42 and 75%, respectively. At the end of the large-scale experiment, grain treated with protein-rich pea flour alone or in combination with parasitoids had better grain quality than the untreated controls.

Metazoan parasites of some commercially important fish along the Kenyan coast

Key words: metazoan parasites, fish, Kenyan coast The parasitic fauna of some commercial fish species along the Kenyan coast was investigated at four localities between August 2001 and March 2002. The study was carried out to establish the extent of parasitisation of different fish species and quantify the relationship between the parasites and their fish hosts. Fish samples were collected once a month from four landing beaches. Sixteen fish species were examined out of which only eight were infested with ecto-and endo parasites. The infested fish species included: the rabbitfish ( Siganus sutor ), the mackerels ( Selar crumenophthalmus, Scomberomorus commerson and Rastrelliger kanarguta ), parrot fish ( Leptoscarus vagiensis ), sardine ( Sardinella gibbosa ), tuna ( Thunnus sp.) and needle fish ( Hemiramphus far ). Of the eight species, Si. sutor was most infested with parasites while Sardinella and Leptoscarus were primarily infested with ectoparasites (isopods). Intensity of infestation increased with age (size), especially in Si. sutor , where very young fish had a low infestation rate, while adults were heavily infested (P Si. sutor (P > 0.05). Western Indian Ocean Journal of Marine Science Vol.3(1) 2004: 71-78

Studies on the epidemiology of tropical theileriosis (Theileria annulata infection) in cattle in Central Anatolia, Turkey.

An epidemiological survey for Theileria annulata infection was conducted in 12 selected villages around Ankara in Central Anatolia, Turkey, during the period April 1990 to January 1993. During the survey, 198 cattle of 30 local breeds, 84 Holstein-Friesian x local breeds and 84 Holstein-Friesian breed were examined for antibodies to T. annulata and the presence of the vector ticks. Four species of Hyalomma ticks were identified: Hyalomma anatolicum anatolicum, Hyalomma anatolicum excavtum, Hyalomma detritum and Hyalomma marginatum marginatum. Salivary gland staining indicated that infected adult ticks of all four species were present and, therefore, were implicated in the transmission of tropical theileriosis in the field. Generally, the Hyalomma infestation rate was low, with the heaviest infestations occurring on the older animals. Young adults and calves had very low infestation rates. Most ticks seen on cattle were adults, very few nymphs were found. The blood smear and serological examination of the 198 cattle conducted in March, before the start of the first disease season, showed that the prevalence of piroplasmosis was 11.1% (22 out of 198) and the seroprevalence of T. annulata was 10.6% (21 out of 198). Forty-three animals were then excluded from the study because they were seropositive and/or harboured piroplasms. Ninety-two seronegative animals showed piroplasmosis (92 out of 155) and 34 seronegative animals became seropositive for T. annulata (34 out of 155) during the three disease seasons. One animal became clinically ill with tropical theileriosis and required treatment. The incidence of cattle showing piroplasmosis and disease in the total study sample was 50.7% and 0.5% per disease season, respectively. The seroconversion rate of new infection with T. annulata in the total study was 14.3% per animal season. The number of cattle showing piroplasmosis was much greater than the number of seropositive cattle, which may indicate the presence of another species of Theileria. The two different management systems encountered in the study were considered to have influenced the tick infestation levels.

Infestación por vectores de la Enfermedad de Chagas en cuatro zonas endémicas de la meseta central de Costa Rica

An entomological search for vectors of Chagas` disease was performed in 157 houses located in 4 endemic regions of the Central Plateau of Costa Rica. Thirteen of the houses (8.3%) were positive for Triatoma dimidiata (Hemiptera: Reduviidae) the only triatomine species found. The bugs were collected mainly in peridomestic piles of firewood (95.2%) and 8.1% of all the insects were infected by Trypanosoma cruzi. The low abundance of Chagas' disease vectors and the their low infestation rates could be attributed to the improvement of the living conditions in the four study zones. The data also suggests that the impact of T. cruzi infection in Costa Rican populations could be low and the prevalence of T. cruzi could be linked to zoonotic cycles

Interactions of aphid herbivory and nitrogen availability on the total foliar glycoalkaloid content of potato plants.

In plant growth room (PGR) and open-air pot (OAP) experiments, potato cvs King Edward and Maris Piper were grown under two nitrogen levels or two different nitrogen release patterns. Plants were subjected to infestation by peach potato aphids Myzus persicae (Homoptera: Aphididae). Total glycoalkaloid (GA) levels were measured in the foliage of both infested and non-infested plants, before, during and after aphid infestation. In the PGR experiment, aphid infestation reduced the amounts of total GAs in both cultivars. This reduction is attributed to the sugar deficiency induced in the plants owing to the dense aphid colonization. Results from the OAP experiment showed a temporal increase of GAs produced by potato cv. King Edward plants subjected to aphid infestation. Elevated amounts of nitrogen in the nutrient solutions (PGR experiment) reduced total GAs, while no differences were observed between manure and fertilizer treated plants (OAP experiment). It is concluded that the source of available nitrogen does not affect foliar GA synthesis in potatoes, and as a consequence, does not affect its endogenous chemical defense against insect herbivory. The case for insect-induced chemical defense mechanisms as triggered by low rates of aphid infestation is discussed.

Field infestation of rambutan fruits by internal-feeding pests in Hawaii.

More than 47,000 mature fruits of nine different varieties of rambutan (Nephelium lappaceum L.) were harvested from orchards in Hawaii to assess natural levels of infestation by tephritid fruit flies and other internal feeding pests. Additionally, harvested, mature fruits of seven different rambutan varieties were artificially infested with eggs or first-instars of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), or oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) to assess host suitability. When all varieties were combined over two field seasons of sampling, fruit infestation rates were 0.021% for oriental fruit fly, 0.097% for Cryptophlebia spp. (Lepidoptera: Tortricidae), and 0.85% for pyralids (Lepidoptera). Species of Cryptophlebia included both C. illepida (Butler), the native Hawaiian species, and C. ombrodelta (Lower), an introduced species from Australia. Cryptophlebia spp. had not previously been known to attack rambutan. The pyralid infestation was mainly attributable to Cryptoblabes gnidiella (Milliere), a species also not previously recorded on rambutan in Hawaii. Overall infestation rate for other moths in the families Blastobasidae, Gracillariidae, Tineidae, and Tortricidae was 0.061%. In artificially infested fruits, both species of fruit fly showed moderately high survivorship for all varieties tested. Because rambutan has such low rates of infestation by oriental fruit fly and Cryptophlebia spp., the two primary internal-feeding regulatory pests of rambutan in Hawaii, it may be amenable to the alternative treatment efficacy approach to postharvest quarantine treatment.

Regional differences in rates and patterns of North American inland lake invasions by zebra mussels (Dreissena polymorpha)

Zebra mussels (Dreissena polymorpha) have spread rapidly in North America by dispersal within connected bodies of waters. This study provides the first systematic evaluation of rates of zebra mussel dispersal to inland lakes separated from source populations by functional dispersal barriers. Plankton samples were examined for this exotic species from 140 lakes during a 3-year period (1995-1997). Infestations were detected in 19% of lakes surveyed: seven of 28 Indiana lakes (25%), 15 of 49 Michigan lakes (31%), but only five of 63 Wisconsin-Illinois lakes (8%). Annual rates of infestation varied from 0 to 12%·year-1 among the three regions. Wisconsin-Illinois lake infestations were only detected in 1995 and 1996, whereas new Indiana and Michigan infestations were detected in all three years. Lakes with surface areas less than 100 ha had lower infestation rates than larger lakes. Incidental sightings of inland lake colonization within the study region qualitatively supported observed regional differences in rates and spatial patterns of colonization. These results demonstrate that the spread of zebra mussels into inland lakes is not occurring as rapidly as through connected waterways, and rates of inland lake colonization vary according to regional conditions and lake size.

Regional differences in rates and patterns of North American inland lake invasions by zebra mussels (&lt;i&gt;Dreissena polymorpha&lt;/i&gt;)

Zebra mussels (Dreissena polymorpha) have spread rapidly in North America by dispersal within connected bodies of waters. This study provides the first systematic evaluation of rates of zebra mussel dispersal to inland lakes separated from source populations by functional dispersal barriers. Plankton samples were examined for this exotic species from 140 lakes during a 3-year period (1995-1997). Infestations were detected in 19% of lakes surveyed: seven of 28 Indiana lakes (25%), 15 of 49 Michigan lakes (31%), but only five of 63 Wisconsin-Illinois lakes (8%). Annual rates of infestation varied from 0 to 12%·year-1 among the three regions. Wisconsin-Illinois lake infestations were only detected in 1995 and 1996, whereas new Indiana and Michigan infestations were detected in all three years. Lakes with surface areas less than 100 ha had lower infestation rates than larger lakes. Incidental sightings of inland lake colonization within the study region qualitatively supported observed regional differences in...

A Preliminary Study on the Effects of Salinity on Growth and Survival of MullowayArgyrosomus japonicusLarvae and Juveniles

Abstract.—Tko experiments were conducted to determine the effects of salinity on growth and survival of mullowayArgyrosomus japonicuslarvae and juveniles. First, 6‐d‐old larvae were stocked into different salinities (5, 12.5, 20, 27.5 and 35 ppt) for 14 d. Larvae grew at all salinities, but based on results for growth and survival, the optimum range of salinity for 6‐d‐old to 20‐d‐old larvae is 5–12.5 ppt. During this experiment larvae held in all experimental salinities were infested by a dinoflagellate ectoparasite,Amyloodiniumsp. Degree of infestation was affected by salinity. There were very low infestation rates at 5 ppt (0.2 parasites/larva). Infestation increased with salinity to 20 ppt (33.1 parasites/larva), then declined with salinity to 35 ppt (1.5 parasites/larva). For the second experiment, juveniles (6.1 ± 0.1 g/fish) were stocked into different salinities (0.6, 5, 10, 20 and 35 ppt) for 28 d. Juveniles were removed from freshwater 3 d after transfer as they did not feed, several fish died and many fish had lost equilibrium. However, when transferred directly to 5 ppt. these stressed fish recovered and behaved normally. Trends in final mean weight and food conversion ratio of juvenile mulloway suggest that fish performed best at 5 ppt. Although salinity (5 to 35 ppt) had no significant (P &gt;0.05) effect on growth, survival, or food conversion ratio of juveniles, statistical power of the experiment was low (0.22). Based on these results we recommend that mulloway larvae older than 6 d be cultured at 5 to 12.5 ppt. Optimum growth of juveniles may also be achieved at low salinities.

Geographical patterns of guinea worm infestation in Ghana: An historical contribution

Guinea worm disease (dracunculiasis) is caused by a parasitic worm, some 2–3 ft in length. Its victims suffer prolonged pain, physical incapacitation, and social and economic disruption. This study identifies geographical patterns of guinea worm disease in Ghana in 1989, just before a national eradication campaign was launched. The broadest belts of disease correspond with long dry seasons, water shortages, and deep water tables over Voltaian sandstone formations. A major “disease hearth” is located in the Northern Region savanna woodland, with rates rising to about 200 per 1000 population. In the rain forest, rates drop below 1 per 1000. Cyclical and seasonal labor migrations result in regional spread of dracunculiasis. The Upper Regions enjoy low rates of infestation, despite constant disease assault by returning migrants. This outcome is based on favorable geology, and hand-pump tube well programs. Village water security in the Upper West Region is associated with a reversal of the seasonal incidence of dracunculiasis. The dry coastal plains are associated with elevated dracunculiasis, but irrigation projects appear to be a compounding influence in the creation of “hot spots” or foci of disease. Notorious in the transtlantic slave trade, and historically long entrenched in rural areas, guinea worm now faces global extinction.

ARTHROPODS ASSOCIATED WITH A MANZANITA GALL INDUCED BY THE APHIDTAMALIA COWENI(COCKERELL) (HOMOPTERA: APHIDIDAE)

AbstractGalls induced by the aphidTamalia coweni(Cockerell) were sampled from greenleaf manzanita (Arctostaphylos patulaE. Greene) in Shasta County, California. Thirty galls from each of four sites were collected over a 5-year period (1990–1994) at roughly weekly intervals (N= 5010). The contents of each gall were examined and recorded. ExcludingT.coweni, 25 taxa were encountered representing eight arthropod orders: Acari, Thysanoptera, Hemiptera, Neuroptera, Coleoptera, Diptera, Lepidoptera, and Hymenoptera. All play a minor role in the gall community with the exception of two species of Diptera. The data suggest thatLeucopissp. andHeringiasp. are obligatory predators ofT.coweniand coexist by partitioning the aphid resource with different exploitation strategies.Heringiasp. has a relatively low infestation rate (10.8%) but is a superior competitor.Leucopissp. compensates for its inability to compete effectively withHeringiasp. by maintaining a higher infestation rate (41.4%).