What is the optimal fertigation start time and frequency in lettuce seedlings?

Although lettuce is one of the most important vegetable crops cultivated in Brazil, producers conduct seedling production empirically, as there are no published reports on the optimal start time and management strategy for seedling fertigation. The present aimed to assess the influence of fertigation management on the growth, physiological aspects and nutritional status of lettuce seedlings and to determine the optimal fertigation start time and frequency. Two experiments were conducted, each with a randomized block design and six repetitions. The first consisted of six treatments, namely six fertigation start times at 0, 3, 6, 9, 12, and 15 d after emergence (DAE), and the second consisted of five treatments, representing different application frequencies at 3, 4, 5, 6, and 7 d intervals. The assessment of nutrient accumulation levels and biometric and physiological characteristics of the seedlings were performed after transplanting. Fertigation start times significantly affected 14 of the 18 variables assessed, particularly the number of leaves, shoot dry weight, leaf area, initial chlorophyll fluorescence, and P, K, Ca, Mg, and S accumulation. The best results for ten variables were obtained when fertigation began at emergence, with values 17.77 - 35.63% higher than those at fertigation onset at 15 DAE. Application frequency only influenced chlorophyll content and N, P, K, and S accumulation, with optimal results obtained at 3 - 6 d intervals. Beginning fertigation at plant emergence favors dry weight production, nutrition and photosynthesis and shortens the production time of lettuce seedlings. The optimal start time for lettuce seedling fertigation is at emergence, with application performed every 6 d.

Developmental and reproductive patterns of Triatoma brasiliensis infected with Trypanosoma cruzi under laboratory conditions

The aim of this work was to study the interaction between Trypanosoma cruzi-1 and Triatoma brasiliensis. A group of 1st instar nymphs was initially fed on T. cruzi-infected mice and a control group was fed on uninfected mice. From the second feeding onwards, both groups were otherwise fed on non-infected mice. The resulting adults were grouped in pairs: infected male/uninfected female, uninfected male/infected female, infected male and female and uninfected male/uninfected female. The infection affected only the 1st instar nymphs, which took significantly more time to reach the 2nd instar than uninfected nymphs. The differences in the molting time between the infected and uninfected nymphs from the 2nd to the 5th instars were not statistically significant. Both groups presented similar rates of nymphal mortality and reproductive performance was not significantly affected by infection in any of the treatments.

Influência do comportamento gregário nos processos de muda de Rhipicephalus sanguineus (Latreille, 1806) (acari: ixodidae), em condições laboratoriais / Influence of aggregation on the molting process of Rhipicephalus sanguineus, (Latreille, 1806) (acari: ixodidae) under laboratory conditions

Objetivou-se com o experimento verificar a influência de diferentes agregações sobre os parâmetros relacionados ao processo de ecdise ninfal e de adulto de Rhipicephalus sanguineus (Latreille, 1806). Foram utilizados como hospedeiros 10 coelhos domésticos (Oryctolagus cuniculus) primos-infestados. Foram analisados os períodos de pré-ecdise, de ecdise e de muda, o percentual e o ritmo de ecdise para todos os estágios estudados. Durante toda a fase não-parasitária, os carrapatos foram mantidos em condições controladas de umidade (80±5 por cento) e temperatura (27±1ºC). Um total de 1560 larvas ingurgitadas e de 1560 ninfas ingurgitadas foi utilizado. Os carrapatos foram divididos em seis grupos contendo um, cinco, dez, 20, 40 e 80 espécimes cada. Para cada um desses grupos foram realizadas dez repetições. Os processos de ecdise ninfal e de adulto foram acompanhados diariamente. Após a análise dos resultados, verificou-se que não houve relação entre as diferentes agregações e o percentual de ecdise em nenhuma etapa experimental. Em todos os outros parâmetros biológicos estudados, verificaram-se diferenças significativas (p<0,05). Os resultados obtidos sugerem que em elevadas agregações o processo de ecdise tende a ser mais rápido.

The objective of this experiment was to evaluate the influence of different aggregations on the molting process of Rhipicephalus sanguineus (Latreille, 1806). Tick-naïve domestic rabbits (Oryctolagus cuniculus) were used as experimental hosts for the parasitic phase. A total of 10 rabbits were used on the experiment. All tick free-living phases were kept in incubator at 27±1ºC, 80±5 percent relative humidity and scotophase. The periods of pre-molt, molt, percentage of ecdisis and molt rhythm of larvae and nymphs were studied. A total of 1560 engorged larvae and 1560 nymphs of R. sanguineus were divided in six groups of aggregations: 1, 5, 10, 20, 40 and 80 ticks with ten repetitions each one. The ecdises of nymphs and adults were daily observed. The percentage of ecdysis was the only parameter with no aggregations effects. All others parameters were statistically different (p<0,05). The results suggested that highest aggregations accelerate the molting process.

Molt and reproduction of the European green crab Carcinus maenas (Decapoda: Portunidae) in Patagonia, Argentina

The green crab Carcinus maenas, a decapod crustacean native to the northeastern Atlantic, has beeninvading distant areas, mainly for the last 25 years. This species is currently distributed along the coasts of thenortheastern Pacific, South Africa, Japan, South Australia, Tasmania, and western and eastern North America,among others. Here we provide information on the biology of the green crab occurring in the central area of SanJorge Gulf, Argentina, where it has been established since 1999-2000. Crabs of both sexes were hand-collectedbetween January 2004 and May 2005 from the intertidal zone and the upper sublittoral fringe. Sex, carapacewidth and molting stage were recorded. The reproductive status of males was based on the presence of sperm andspermatophores in testes and deferent ducts, and that of females on ovarian development and presence-absenceof eggs. Stages of embryonic development for ovigerous females were also recorded. The most importantphysiological events taking place during the annual cycle of the adult population were as follows: (1) male moltoccurred mainly in November and female molt between January and the beginning of March; (2) the reproductiveseason started in January, after a courtship in which the male, larger in size, holds the female until the molt,and spermatophores are ejaculated once the old exoskeleton is cast off; (3) females left the intertidal zone earlyand moved to lower littoral levels during fall and winter; (4) larvae appeared in September.

El cangrejo verde europeo es un crustáceo decápodo originario del Océano Atlántico nororiental, el cual principalmente en los últimos 25 años ha invadido, entre otros, el Pacífico nororiental, Sudáfrica, Japón, sur de Australia, Tasmania y ambas costas de América del Norte. Aquí resumimos las observaciones biológicas en el área central del Golfo San Jorge, Argentina, donde este cangrejo se ha instalado a partir de 1999 ó 2000. Recolectamos manualmente muestras de ambos sexos entre enero de 2004 y mayo de 2005 en el intermareal y la franja superior del sublitoral. La muda de los machos ocurre principalmente en noviembre y la de las hembras, entre enero y principios de marzo. La época reproductiva se inicia en enero, con un cortejo previo donde el macho, de mayor talla que la hembra, la retiene hasta la muda y, una vez desprendido el viejo exoesqueleto, se produce la eyaculación de los espermatóforos. Las hembras abandonan tempranamente el intermareal y migran a niveles inferiores del litoral durante el otoño e invierno, eclosionando las larvas en setiembre.

Indução a muda forçada em Galinhas D’Angola (Numida meleagris) através do óxido de zinco / Induced molt in Guinea fowls (Numida meleagris) through the use of zinc oxide

Devido à escassez de estudos sobre muda forçada em aves alternativas de produção, este experimento teve o objetivo de realizar a muda forçada em galinhas D’Angola avaliando as perdas de peso corpóreo (PPC) que promovessem os melhores índices produtivos pós-muda. Com este propósito foram utilizadas 110 galinhas D’angola alojadas individualmente em gaiolas de poedeiras comerciais e, posteriormente, submetidas à muda forçada com 20000 ppm de óxido de zinco na ração. Estas passaram 21 dias recebendo ração e água ad libitum. Para análise da PPC relacionada à produtividade pós-muda foram utilizados 60 aves organizadas nos seguintes grupos: 24% (n=18); 26% (n=18); 28% (n=12) e acima de 30% (n=12). As outras 50 aves foram sacrificadas para o estudo do aparelho reprodutor, onde se verificou o tamanho e peso do oviduto e peso do ovário com PPC de 0% e sua regressão à medida que atingiam os níveis de PPC: 24%; 26%; 28% e acima de 30%. A média de retorno produtivo foi 60%, sendo o grupo com PPC de 24% com o melhor índice (100%), no entanto, este apresentou índice de produção insatisfatório juntamente com o grupo de PPC acima de 30%. A muda forçada em Galinhas D’Angola foi viável com índices de PPC em torno de 26% a 28% e inviáveis com níveis abaixo de 24% e acima de 30%. Em relação à regressão do aparelho reprodutor, os melhores resultados produtivos foram em torno de 65,15%, 90,49% e 94,27% para tamanho e peso do oviduto e peso do ovário, respectivamente.

Due to scarcity of studies on forced molt in alternative production birds, this experiment had the objective of performing an induced molt in Guinea Fowls observing the best body weight losses (BWL) that could promote good post-molt productions. With this purpose, 110 Guinea fowls were housed in individual commercial cages and were submitted to induced molt through the addition of zinc oxide in feed with the concentration of 20000 ppm during 21 days and received drinking water ad libitum. In the analysis of BWL related to post-molt productivity, 60 birds were organized in the groups, according to the percentage of BWL: 24% (n=18), 26% (n=18), 28% (n=12) and more than 30% (n=12). The other 50 birds were sacrificed for analyses of the reproductive organs, in which the oviduct size and weight of oviduct and ovary were measured with 0% of BWL and since then the regression of these organs were calculated to 24%, 26%,28% and more than 30% of BWL. The medium of post-molt return to production was 60% and the group of 24% of BWL presented the best productive return (100%), however this group presented an insufficient production rate as the birds with 30% of BWL. In this way, the induced molt in Guinea fowls was viable with BWL around 26 and 28% and unviable with less than 24% or more than 30%. In relation to regression of the reproductive organs the best productive results were 65,15%,90,49% and 94,27% to oviduct size and weight and ovary weight, respectively.

A Triatoma maculata ( Hemiptera, Reduviidae, Triatominae ) population from Roraima, Amazon region, Brazil, has some bionomic characteristics of a potential Chagas disease vector

A doença de Chagas é de rara ocorrência na Região Amazônica Brasileira, onde contudo as condições para o estabelecimento de ciclos domésticos existem. Um estudo previamente realizado em áreas de colonização agrícola no Estado de Roraima, mostrou a possibilidade de ciclos autóctones de transmissão virem a ocorrer uma vez que todos os elementos estavam lá presentes, indivíduos infectados por Trypanosoma cruzi, espécies de triatomíneos anteriormente descritas como infectadas por T. cruzi na Região Amazônica de países fronteiriços e, ambientes domiciliares e peri-domiciliares favoráveis à colonização de triatomíneos. Triatoma maculata foi a espécie mais frequentemente encontrada, tendo sido coletada em galinheiros no peridomicílio e esporadicamente nos domicílios. Visando investigar a potencialidade de T. maculata como espécie vetora na área, algumas características bionômicas foram estudadas em condições de laboratório incluindo freqüência de alimentação, tempo de defecação pós-prandial, tempo de jejum voluntário na pré- e na pós-ecdise, período inter-mudas, períodos de pré-oviposição e de oviposição, índice de oviposição, período de incubação, viabilidade dos ovos, índices de longevidade e de mortalidade. Os resultados mostraram que a população de T. maculata da Colônia Agrícola do Passarão deve ser considerada vetora em potencial do T. cruzi uma vez que mostrou capacidade de infestar ecótopos artificiais no peridomicílio, de se alimentar com freqüência durante o período ninfal, de possuir um ciclo de desenvolvimento relativamente curto com 2,9 gerações/ano, de possuir hábitos ecléticos de alimentação, de defecar imediatamente após a hematofagia quando ainda no hospedeiro e devido ao fato de ter sido previamente encontrada infectada por T. cruzi.

Effects of eyestalk ablation on moulting and growth of penaeid prawn Metapenaeus dobsoni (de Man).

Penaeid prawns M. dobsoni of two different size ranges were ablated both unilaterally (UEA) and bilaterally (BEA) and subjected to individual study. The UEA prawns consumed almost the same amount of food as the control prawns in the size group, 35-40mm, but consumed about 57.8% more food than the control prawns in the larger size group, 48-53mm. Growth was estimated as length and weight changes and significant variation was observed. The moult rate and dry moult weight showed marked differences. Average intermoult period increases with second ablation. Dry weight of moult in every succeeding moult was found to decrease irrespective of the level of ablation. Unilateral eyestalk ablation resulted in increase in dry weight whereas bilateral eyestalk ablation reduced the dry weight of moult and this decrease in the rate increased after each subsequent moult. In the larger size group, values of protein efficiency ratio (PER) were almost same as that of the lower size group. The UEA prawns exhibited highest conversion efficiency. The production rate of UEA prawns was 84% more than that of the control whereas BEA prawns indicated negative production. The same trend followed for net growth efficiency also. The results suggest that unilateral eyestalk ablation can be resorted to accelerate growth and conversion efficiency. Eyestalk ablation has been frequently resorted in matured forms for inducing maturation of gonads. For the first time attempts have been made to compare between the effects of removing one eyestalk versus two and changes taking place in juvenile forms especially in their physiology related to growth.

Changes in the integument of nymphal and adult hyalomma [hyalomma] dromedarii koch[Acari: Ixodoidea: Ixodidae] I the effects of feeding and moulting

The integument of the dorsal alloscutum in nymphal and female H. dromedarii consists of the cuticle underlined by epidermis. The cuticle contains two layers, a thin external epicuticle and a thick internal procuticle. The procuticle is distinguished into an outer endocuticle and an inner endocuticle. Changes occuring in the cuticle and epidermis in symphal and adult H. dromedarii are correlated with moulting and feeding