Plasmatocytes Research Articles

Effects of parasitism by the braconid wasp, Bracon hebetor (Hymenoptera: Braconidae), on the host hemolymph and phenoloxidase activation of the rice moth, Corcyra cephalonica larvae (Lepidoptera: Pyralidae)

BackgroundBiological control of insect pests is an economic, eco-friendly and harmless approach to integrated pest management strategies. Bracon hebetor (Say) (Hymenoptera: Braconidae) considers a polyphagous ectoparasitoid of various pests of the order Lepidoptera. The parasitized host insects' defense mechanisms are triggered as a result of the parasitic wasps' injury and penetration. Thus, induce the host cellular and humoral immune responses through a blend of secretions injected into the host body. The present study was designed to evaluate the efficacy of B. hebetor on the immune response of the parasitized full grown larval instar of the rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) under natural envenomation.ResultsOn cellular level, the ultrastructure examination of the hemocytes displayed a considerable structural deformation in hemocyte morphology of the detected types of the hemocytes. Moreover, the effects of parasitism on both differential hemocyte counts (DHCs) and total hemocyte counts (THCs) were investigated. The number of prohemocytes (PR) (40.33 ± 5.61, 43 ± 8.33 and 26 ± 2.31) was statistically differed after (24, 48 and 72 h) of parasitism, respectively, compared to unparasitized (31.33 ± 6.49) larvae. Similar observations were recorded in plasmatocytes (PL) before and after the parasitism. However, Spherulocytes (SP) and Oenocytoids (OE) were recorded in the hemolymph with little abundance. On the other side, the quantitative analysis of total hemolymph proteins (THP) provoked a significant effect of considering parasitized and non-parasitized larvae. As the Phenoloxidase (PO) cascade plays a critical role in immune defenses, so the substantial activation of PO in the host's hemolymph following successive hours of parasitism compared to unparasitized larvae using L-DOPA as a substrate indicated the induction of larval immune system. The parasitized larvae showed a gradual increase in the PO activity (0.442 ± 0.103) after 24 h reached up to (1.482 ± 0.272) at the end of parasitism (72 h) in comparable to unparasitized larvae (0.177 ± 0.0.044).ConclusionThe present investigations clarified the efficacy of B. hebetor parasitism on the host immune mechanism, which will enable the progress of sustainable stored product protection approaches for the control of an important pest rice moth C. cephalonica.

Impact of different diets' nutrition on the fitness and hemocytic responses of the greater wax moth larvae, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae)

BackgroundThe greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), is the major devastating insect pest of beekeeping industry all over the world; however their larvae were valuable to be the most favorable alternative invertebrate model. For this purpose, new-hatched larvae were reared on five different nutritional diets based on: old wax-comb (natural food); wheat flour diet (Triticum aestivum L.); soybean diet (Glycine max); wheat germ diet; and date syrup diet (Phoenix dactylifera L.) till reaching the fully grown 6th instars to evaluate their fitness and hemocytic responses.ResultsFully grown larvae from soybean diet had the highest rates of fresh (280 mg) and dry weights (104 mg), water contents (175.6 mg), carbohydrates (1.97%), total hemocyte count (THC) (4746/mm3), total soluble solid (TSS) (21.7%), hemolymph protein concentration (HPC) (1662.5 mg/100 ml), and hemolymph content (density 3.82 mg/µl and volume 70.35 µl/larva), followed by wheat germ diet in comparable to the natural food. All suggested diets considered as rich protein-materials; recording high protein rates on their larvae (39.51–41.87%), with only the exception of old wax-comb had the lowest one (36.63%). Moreover, five types of hemocytes were classified in the larval hemolymph as (prohemocytes (PR), plasmatocytes (PL), granulocytes (GR), oenocytoids (OE) and spherulocytes (SP)), but with different rates related to different diets. Regardless the rearing diets, PR type was the most frequently recorded cell type (73.31%) in hemolymph, followed by PL (8.37%), and the lowest one was OE cells (5.82%).ConclusionsThe suggested diets of soybean and wheat germ recorded the best results than the other diets used almost, and could be recommended as standard diets to mass-produce healthy and high-quality G. mellonella for in vivo experimentation and/or microbiological studies.

Study of haemocytes of the rice brown planthopper, <em>Nilaparvata lugens</em> Stål (Hemiptera: Delphacidae)

Purpose: The brown planthopper (BPH), Nilaparvata lugens, is one of the most serious insect pests of rice (Oryza sativa L.) in South and South East Asia and also parts of the Pacific and Australia. The BPH, like other insects, is able to build up powerful innate immune responses against invading pathogens and cellular immunity mediated by haemocytes. Hence, an attempt was made to investigate the detailed microscopic analysis of the haemocytes of BPH. Research Method: The study was primarily concerned with the haemocyte profile of BPH with emphasis on the changes in the total and differential haemocyte population with three different life stages; 5th nympal stadium, newly emerged adults (post-moulting adult of 1-3 days old) and matured adults (15 days old) for an insight of the physiological events during the morphogenesis Findings: According to light microscopic examinations, the haemogram of the BPH comprised six types of haemocytes viz. prohaemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs), adipohaemocyte (ADs) oenocytoids (OEs) and spherulocytes (SPs). It was estimated that the mean numbers of total haemocyte count are varied from 6096.4 to 7393.6 cells per mm3 of haemolymph with the different physiological stages of the insects and it was statistically increased in the mature adults. PLs, GRs and PRs are the most abundant cells in the haemolymph in all development stages of BPH while SPs is the scarcest type. Originality/value: To our knowledge, this is the first report that has detected the haemogram of BPH and these data are valuable for future avenues of immunological research of BPH.

Identification of Silkworm Hemocyte Subsets and Analysis of Their Response to Baculovirus Infection Based on Single-Cell RNA Sequencing.

A wide range of hemocyte types exist in insects but a full definition of the different subclasses is not yet established. The current knowledge of the classification of silkworm hemocytes mainly comes from morphology rather than specific markers, so our understanding of the detailed classification, hemocyte lineage and functions of silkworm hemocytes is very incomplete. Bombyx mori nucleopolyhedrovirus (BmNPV) is a representative member of the baculoviruses and a major pathogen that specifically infects silkworms (Bombyx mori) and causes serious losses in sericulture industry. Here, we performed single-cell RNA sequencing (scRNA-seq) of hemocytes in BmNPV and mock-infected larvae to comprehensively identify silkworm hemocyte subsets and determined specific molecular and cellular characteristics in each hemocyte subset before and after viral infectmadion. A total of 20 cell clusters and their potential marker genes were identified in silkworm hemocytes. All of the hemocyte clusters were infected by BmNPV at 3 days after inoculation. Interestingly, BmNPV infection can cause great changes in the distribution of hemocyte types. The cells appearing in the infection group mainly belong to prohemocytes (PR), while plasmatocytes (PL) and granulocytes (GR) are very much reduced. Furthermore, we found that BmNPV infection suppresses the RNA interference (RNAi) and immune response in the major hemocyte types. In summary, our results revealed the diversity of silkworm hemocytes and provided a rich resource of gene expression profiles for a systems-level understanding of their functions in the uninfected condition and as a response to BmNPV.

Quantitative and Qualitative Impacts of Selected Arthropod Venoms on the Larval Haemogram of the Greater Wax Moth, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae)

The greater wax moth, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) is the most destructive pest of honey bee, Apis mellifera Linnaeus (Hymenoptera: Apidae), throughout the world. The present study was conducted to determine the quantitative and qualitative impairing effects of the arthropod venoms, viz., death stalker scorpion Leiurus quinquestriatus (Hemprich & Ehrenberg) venom (SV), oriental Hornet (wasp) Vespa orientalis Linnaeus venom (WV) and Apitoxin of A. mellifera (AP) on the larval haemogram. For this purpose, the 3rd instar larvae were treated with LC50 of each of these venoms (3428.9, 2412.6, and 956.16 ppm, respectively). The haematological investigation was conducted in haemolymph of the 5th and 7th (last) instar larvae. The important results could be summarized as follows. Five basic types of the freely circulating haemocytes in the haemolymph of last instar (7th) larvae of G. mellonella had been identified: Prohemocytes (PRs), Plasmatocytes (PLs), Granulocytes (GRs), Spherulocytes (SPs) and Oenocytoids (OEs). All venoms unexceptionally prohibited the larvae to produce normal hemocyte population (count). No certain trend of disturbance in the differential hemocyte counts of circulating hemocytes in larvae of G. mellonella after treatment with the arthropod venoms. Increasing or decreasing population of the circulating hemocytes seemed to depend on the potency of the venom, hemocyte type and the larval instar. In PRs of last instar larvae, some cytopathological features had been observed after treatment with AP or WV, but SV failed to cause cytopathological features. With regard to PLs, some cytopathological features had been observed after treatment with AP while both SV and WV failed to cause cytopathological features in this hemocyte type. No venom exhibited cytopathological effects on GRs, SPs or OEs.

Variations in hemocyte profile induced by Beauveria bassiana (Bals.) Vuill. in Periplaneta americana (L.) (Blattodea: Ectobiidae)

Hemocytes of healthy (untreated) and Beauveria bassiana (Bals.-Criv.) Vuill.-treated nymphs and adults Periplaneta americana (L.) (Blattodea: Ectobiidae) were examined with phase contrast microscopy. The total hemocyte counts (THCs) and differential hemocyte counts (DHCs) were estimated and compared between the untreated and treated nymphs and adults; significant augmentation of THC was observed in the treated 3rd, 4th, 5th instars and adults at 6 h after treatment (HAT), compared to the untreated individuals, followed by its suppression. In addition to changes in the population dynamics of prohemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs) and spherulocytes (SPs), their morphology was also affected. GRs, predominant hemocytes involved in cell-mediated defense, responded to the infection differently including the formation of fine pseudopodia–like cytoplasmic extensions and, they clumped together.

Humoral Immune Response And Midgut Histopatholical Changes In Grasshopper Schistocerca Gregaria Fed On Four Different Plants And Infected With Bacillus Thuringiensis

The present study investigated the effect of dietary changes on differential and total haemocyte counts (THCs) and midgut histopathologiocal changes of S. gregaria injected with Bacillus thuringiensis israelensis (Bti). THCs of Bti-injected adults significantly decreased in all insects fed on all experimental plants. In Bti-injected locusts, prohaemocytes (PRs) percent decreased in insects fed on grass and quietly disappeared in other treatments. plasmatocytes (PLs) percent increased, while the granulocytes (GRs) decreased in all tested insects fed on sorghum, sesban, grass and clover than those of the control. The percentages of oenocytoids (OEs) increased in all treatments except in insect fed on sesaban. The results indicated that insects fed on clover had the highest number of haemocytes, while those fed on grass had the lowest number. Certain pathological symptoms in the midgut of Bti treated adults were observed after 48 hr post injection, such as (1) disorganisation, disintegration and vacuolization of epithelial cells, (2) lysis of the basement membrane and surrounding muscles and (3) detachment of microvilli from epithelial cells. The most deformed group to Bti was grass fed locust. Subsequently, the host plant could be a major factor that affect on the response of herbivorous insects to pathogens.

Immunological and Histopathological Effect of Plant Extract on Schistocerca Gregaria

The desert Locust, Schistocerca gregaria (Forsk) is one of the serious pests attacking vegetables and wide varieties of other field crops in Egypt and other different countries.The present study was also extended to conduct the insecticidal effect of the most potent extracts Citrullus colocynthis, and Guayacum officinalis extract post formulation on S. gergaria larvae. The present study has been conducted to investigate the effect of plant extract on differential and total haemocyte counts and midgut histopathologiocal changes of S. gregaria Four types of haemocytes were characterized; prohaemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs) and oenocytoids (OEs). The percentage of PRs decreased in insects fed on leaves treated with Citrullus colocynthis, and Guayacum officinalis plant The percentage of PLs increased, while the percentage of GRs decreased in all tested insects treated. The percentages of oenocytoids (OEs) increased in insect fed treated compared with control. Results indicated that THCs of insects fed on leaves treated significantly decreased in all insects treated. also, showed highly histopathological disturbances in the midgut and body wall cells of this pest. Among the most recorded observations are vacuolation, destruction of the cells.

Investigation into the Effect of Altitude on the Differential Hemocyte Count of Circulating Plasmatocytes and Granulocytes of Larval Stage of Antheraea assama (Lepidoptera: Saturniidae).

Differential hemocyte count of circulating plasmatocytes (PL) and granulocytes (GR) of fifth-instar larvae of Muga Silkworm Antheraea assama Westwood (Lepidoptera: Saturniidae) reared at four different sericulture farms situated at different altitudes, viz, Khanapara State Sericulture Farm, Assam, altitude 55.5 m above sea level (ASL); Nongpoh (Central Silk Board farm), Meghalaya, altitude 464 m ASL; Tura (Central Silk Board farm), West Garo Hills, Meghalaya, 657 m ASL; and Kalimpong (Central Silk Board farm), West Bengal, altitude 1,247 m ASL, were calculated and compared to investigate the effect of altitude on the number of PL and GR per mm3 of larval hemolymph. The investigation showed that the mean circulating PL and GR were highest at Khanapara (55.5 m ASL) located at the lowest altitude, whereas their numbers gradually decreased with increase in altitude at Nongpoh (464 m ASL), Tura (657 m ASL), and Kalimpong (1,247 m ASL). This may be attributed to the average environmental temperatures observed at different altitudes, which may affect the overall hemocyte load of larval stages reared at those altitudes.

Effects of Destruxin A on Hemocytes Morphology of Bombyx mori

Destruxin A (DA), a kind of cyclo-hexadepsipeptide isolated from entomopathogenic fungus, Metarhizium anisopliae, is an inhibitor of insect's immunity. But its mechanism has not been clarified yet. In this study, the effects of DA on morphologic changes of in vivo and in vitro hemocytes of silkworm, Bombyx mori, were investigated by means of inverted phase contrast microscopy (IPCM), fluorescence microscopy (FCM) and environmental scanning electron microscopy (ESEM). The results indicated that DA was cytotoxic to granulohemocytes (GR) and plasmatocytes (PL). The LC50 values of DA against in vitro GR and PL of silkworm were 68.77 and 84.11 µg mL−1, respectively. However, the hemocytes in vivo were more susceptible to DA, although at the extremely low dose of 10 µL of 12.5 µg mL−1 for each insect (i.e., 0.036 µg g-1 body weight, or approximately 0.25 µg mL−1 hemolymph), DA could induce obviously morphologic alterations of hemocytes in vivo. The results imply that there might be some factors in silkworm's hemolymph, which influence the interaction of DA and hemocytes.

Parasitism of Pieris rapae (Lepidoptera: Pieridae) by the endoparasitic wasp Pteromalus puparum (Hymenoptera: Pteromalidae): Effects of parasitism on differential hemocyte counts, micro‐ and ultra‐structures of host hemocytes

Abstract Parasitism by the endoparasitic wasp Pteromalus puparum (Hymenoptera: Pteromalidae) by using only its associated venom, can suppress the immunal responses of Pieris rapae (Lepidoptera: Pieridae). However, up to now, current knowledge of the mechanisms has been limited. The response of host hemocytes to parasitism was investigated using a combination of light and transmission electron microscopy (TEM). Five hemocyte types, prohemocytes (PRs), granulocytes (GRs), plasmatocytes (PLs), oenocytoids (OEs) and coagulocytes (COs), were observed and characterized from both unparasitized and parasitized Pieris rapae pupae. Light microscopy showed that both GRs and PLs became more round and spread abnormally after parasitism, whereas the shape of other types of hemocytes remained unaffected. In addition, the size of PRs and PLs became larger while OEs became smaller. The proportion of PRs significantly increased after parasitism and that of PLs decreased by 43.9%, but there was no significant increase of GRs and OEs. TEM showed that all types of hemocytes except COs were damaged to various degrees after parasitism, especially resulting in electron opaque cytoplasm and nucleus, fewer cell organelles of rough endoplasmic reticulum, mitochondria and vesicles. Our results indicate that parasitism by P. puparum affects differential hemocyte counts and structures of host hemocytes, particularly for GRs and PLs, which may be the main cause of the parasitoid suppressing host cellular immune responses.

HEMOCYTES PROFILE OF STINK BUG, CANTHECONA FURCELLUTA Wolff: A SEVERE PEST OF ANTHERAEA MYLITTA DRURY

The five types of hemocytes were documented in Stink bug, Cantheconafurcelluta Wolff, they are prohaemocytes (PRs), plasmatocytes (PLs), granulocytes(GRs), adipohaemocytes (ADs) and oenocytoids (OEs). PRs are small spherical cellswith a centrally located large rounded nucleus filling the entire cytoplasmic area.Mitotic divisions are frequently seen in these cells. PLs are spindle shaped biramous,triramous and possess relatively smaller central nucleus with cytoplasmicprolongations. GRs are spherical with centrally located nucleus. Their cytoplasmis normally crammed with thick granules of diverse sizes. ADs are large, roughlyrounded to ovoid in shape with a comparatively small eccentric nucleus. OEs arealso large sphere-shaped with a small rounded eccentric nucleus and theircytoplasm is generally thick and uniform. In addition great deal of variations wasrecorded in the differential hemocyte count (DHC) of nymhal and adult stage.

Evaluation of Hemocyte Cells in Zonocerus variegatus (L.) During Postembryonic Development

The types and number of hemocyte cells present in Zonocerus variegatus (L.) during post-embryonic development were evaluated with the aid of hemacytometer. Six hemocyte cells, namely, Adipohaemocytes (ADS), Granulocytes (GRS), Oenocytes (OES), Plasmatocytes (PLS), Prohaemocytes (PRS), and Sphcrulocytes (SPS) were found in the haemolymph of the nymphs and adults. However, OES was not present in the 1st instar nymph. PLS had the highest hemocyte count (59.90 x 10’per ml of haemolymph) and OES had the least (21.01 x 10′ per ml). The adult stage had significantly (P<0.05) higher hemocyte count (62.75 x 105 per ml) than the nymphal instars (14.0-48.75 x 10\ however. the differences between the 1st and the 2nd instars as well as the differences among the 4th– 6th instars were not significant (P>0.05).

Changes in the haemocytes of Agrotis ipsilon larvae (Lepidoptera: Noctuidae) in relation to dimilin and Bacillus thuringiensis infections

Five types of haemocytes are observed in the fourth larval instar of the black cutworm, Agrotis ipsilon: prohaemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs), spherule cells (SPs) and adipohaemocytes (ADs). Infection of A. ipsilon fourth larval instar with Bacillus thuringiensis and dimilin resulted in a reduction of the total haemocyte count. Changes in the differential haemocyte population during bacterial and dimilin infections have been assessed. The PRs % decreased significantly while SPs, PLs, and GRs % increased significantly after the application of the two insecticides at 12 and 24 h. Ultrastructural alternations and malformations have been observed in circulating haemocytes of A. ipsilon larvae treated with dimilin and B. thuringiensis.

Effect of sweet flag rhizome oil ( Acorus calamus) on hemogram and ultrastructure of hemocytes of the tobacco armyworm, Spodoptera litura (Lepidoptera: Noctuidae)

Effect of the essential oil of Acorus calamus L. rhizomes, was studied on hemocytes of the tobacco armyworm, Spodoptera litura. The oil was administered in oral application at concentration of 500 and 1000 ppm to last instar larvae of S. litura and its effect on ultrastructure of hemocytes and hemogram was evaluated. The oil was administered in topical application at 250 μg dose to pupae to ascertain its effect on total and differential hemocyte counts. At both scanning (SEM) and transmission electron microscopic (TEM) levels, the major effect of oil treatment was observed on plasmatocytes (PLs) and granular hemocytes (GRs). SEM study revealed that the cytoplasmic projections of granular hemocytes were reduced, while the filopods of plasmatocytes remained unaffected. The vacuolization in the cytoplasm and degeneration of the organelles in both plasmatocytes and granular hemocytes was observed by TEM. However, no such deformities were observed in prohemocytes (PRs), spherulocytes (SPs), and oenocytoids (OEs). A concentration-dependent decrease has been observed in the larval body weight and hemolymph volume (HV), 24–72 h after treatment. In comparison to the controls, the maximum percentage growth inhibition (GI) was recorded to be 58.28 and 66.48, respectively at 500 and 1000 ppm after 72 h treatment. Similarly after 72 h treatment, the percentage reduction in hemolymph volume was 61.38 and 69.05, respectively at 500 and 1000 ppm. Total hemocyte count (THC), in larvae computed from five recorded hemocyte types viz. PRs, PLs, GRs, SPs and OEs, decreased only after 48–72 h of treatment. The maximum decrease in THC was recorded to be 29.15 and 49.05% at 500 and 1000 ppm, respectively, after 72 h of treatment. There was continuous decline in THC in pupae after 24–72 h treatment. DHC study revealed that both the concentrations of oil in 6th instar larvae of S. litura caused a decrease in PRs, PLs and SPs and increase in GRs and OEs after 24–72 h of treatment. Since A. calamus oil treatment causes the injury to both PLs and GRs and also affects the hemogram, it can be inferred that cellular defence reactions of S. litura are impaired.

Influência da temperatura sobre os tipos celulares presentes na hemolinfa de larvas e ninfas de Rhipicephalus sanguineus

Este trabalho foi realizado com o intuito de se verificar a influência de três temperaturas (18, 27 e 32°C) sobre os tipos celulares presentes na hemolinfa de larvas e ninfas de Rhipicephalus sanguineus (Latreille, 1806). Seis tipos celulares básicos foram encontrados na hemolinfa: prohemócitos (PR), plasmatócitos (PL), granulócitos (GR), esferulócitos (ES), adipohemócitos (AD) e oenocitóides (OE). Os ES foram divididos em dois subtipos (ES I e ES II), devido às variações morfológicas encontradas. O efeito da temperatura foi mais acentuado sobre o estádio de larva. Ocorreu queda acentuada de GR e aumento de ES II na temperatura de 18°C, enquanto que à 27 e 32°C, os valores foram semelhantes. GR foi o tipo celular mais abundante, indicando o seu envolvimento no metabolismo. Para ninfas este também foi o tipo celular mais abundante, porém não ocorreram variações acentuadas segundo a temperatura, indicando que cada estádio de desenvolvimento apresenta determinada necessidade metabólica que se expressa nos tipos celulares presentes na hemolinfa.

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Six circulating hemocytes cell types from Diatraea saccharalis (Fabricius) (Lepidoptera: Pyralidae) larvae were identified by transmission and scanning electron microscope: prohemocytes (PR), plasmatocytes (PL) granulocytes (GR), spherulocytes (SP), oenocytoids (OE) and vermicytes (VE). The PR was the smallest cell type with a large nucleus, a cytoplasm with few organelles and a homogenous smooth surface. The PL was polymorphic and abundant, with a cytoplasm rich in organelles and a cellular surface with several cytoplasmic projections. The GR was abundant, showing two types of membrane-bounded granules (dense and structutered), glycogen, lipid droplets and a surface with philopodial projections. The SP was a large cell, with a cytoplasm full of intracytoplasmic spherules. The OE was the largest hemocyte type with a large and homogeneous cytoplasm and scarce organelles. The VE was discoid in shape and showed electron-dense granules.

Video Microscopy of Biphasic and Continuous Hemolymph Flow in the Circulatory Systems of Developing Embryos of the Waterstrider <I>Gerris paludum insularis</I> (Hemiptera: Gerridae)

Hemolymph flow patterns, deduced from movements of single plasmatocytes (PLs) in the heart-dorsal vessel system were observed in developing embryos of the waterstrider Gerris paludum insularis Motschulsky. Video images of single moving PLs successively captured at 0.033 s intervals were followed to reveal their passage during each cardiac cycle, and a structural cardiogram was used to analyze the movements of individual PLs in terms of the cycle. In hearts of G. p. insularis embryos, cultured for 80 h after katatrepsis (K+80 h embryos; K stands for katatrepsis), forward flow with systole and backward flow with diastole occurred alternatively during each cycle. In K+100 h embryos, however, forward flow was observed only with systole and ceases at other times in the cycle. Velocity of single moving PLs in K+80 h embryos, estimated from distance traversed by PLs for each 0.033 s, was smaller than that in K+100 h embryos similarly estimated. This might indicate that the force generated by each systolic contraction in the heart of G. p. insularis embryos increased as embryogenesis advanced. Velocity of single moving PLs was suggested as a useful parameter to assess functional development of embryonic heart in insects.

Influence of Precocene II on the estimated changes within the haemocyte population of parasitized spodoptera littoralis larvae by microplitis rufiventris

Series of experiments were undertaken to investigate whether application of Precocene II (PII) to parasitized S. littoralis larvae can influence their THCs and DHCs. PII was applied in single dose treatments (70μg/5 μl/dose). Haemolymph samples were taken at daily intervals from day 3 to day 8 post‐treatments. Two distinct alterations were noted; first, PII‐treatments caused significant decrease in THCs. Once the parasitoid larvae emerge from either treated or untreated hosts, a sharp decline in THCs was observed. The second effect was changes in DHCs of S. littoralis larvae. In controls, haemocyte types could be arranged in descending order due to their relative occurrence into plasmatocytes (PLs), prohaemocytes (PRs), spherule cells (SPs), granular cells (GRs) and oenocytoids (OEs). This order changed in treated hosts to PLs, GRs, PRs, SPs and OEs, i.e., GRs that were less prevalent in the haemolymph of control larvae increased significantly in PII‐treated hosts. In the latters, sharp rise in GRs levels followed parasitoid emergence. OEs cells were scarce in both treated and untreated hosts. No significant difference was observed between the overall means of PLs in both types of host larvae. But GRs‐PRs was markedly altered in treated larvae.

Follow-up of protein release from Pseudoplusia includens hemocytes: a first step toward identification of factors mediating encapsulation in insects

Hemocyte types involved in encapsulation were characterized using monoclonal antibodies (mAbs). This approach revealed that four hemocyte types in Pseudoplusia includens could be classified into two antigenically distinct cell lines. The first line comprised granulocytes (GR) and spherulocytes (SP) and the second line comprised plasmatocytes (PL) and oenocytoids (OE). One of the mAbs labeled a subpopulation of plasmatocytes that spread on culture plate surfaces. This subclass represented approximately 70 % of all plasmatocytes. The cytoplasmic punctate staining of granulocytes clearly decreased upon short term culture, suggesting the associated antigens were released into the culture medium during cell spreading. A follow-up of protein secretion into culture medium by Western blotting confirmed this hypothesis for both granulocytes and plasmatocytes. In a few cases, discharged proteins exhibited a short half-life suggesting they may behave as regulatory molecules. Among them, plasmatocyte proteins of ± 25 kDa might be mobilized at an early stage of encapsulation. The same proteins appeared to accumulate at the periphery of the median plasmatocyte multilayer in late capsules. This location coincides with where an outer monolayer of granulocytes attaches and causes termination of capsule growth. These preliminary results raise the possibility that released proteins regulate hemocyte recruitment during encapsulation.