Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Parasitization of the cottony-cushion scale in relation to host size

Measurements of body length of cottony-cushion scales,Icerya purchasi Maskell, are presented. Although length increased markedly with developmental stage, the length distributions of successive stages were found to overlap, making length an imperfect indicator of stage andvice versa. The likelihood of parasitism by the fly,Cryptochaetum iceryae (Williston), was found to increase with increasing scale size when scales of different sizes were concurrently made available to the parasites under field conditions. Also, parasite loads (no. of parasites per parasitized host) were found to increase with host size. The size ofC. iceryae pupae was found to depend on the developmental stage of the scale host in which pupation took place — the more developed (larger) the host, the larger the pupa. This result suggests that parasite growth is food limited in the smaller hosts, and that therefore its apparent preference for larger hosts is to the parasite's advantage.      

Parasites of the spotted stalk borer,Chilo partellus [Lepidoptera: Pyralidae] in South Africa

One egg parasite, 7 larval parasites, 2 pupal parasites and 3 larval hyperparasites were recorded parasitizing the spotted stalk borer,Chilo partellus (Swinhoe) on maize and grain sorghum in South Africa.Trichogrammatoidea lutea Girault [Trichogrammatidae] parasitized eggs ofC. partellus mainly in mid-summer. The larval parasites were active throughout the season with occasional peaks of up to 75% parasitism.Apanteles sesamiae Cameron [Braconidae], proved to be the most abundant larval parasite. It was recorded fromca. 93% of parasitized larvae but its efficiency was reduced by the hyperparasite,Aphanogmus fijiensis (Ferriére) [Ceraphronidae], which reached sometimes up to 100% parasitism on cocoons ofA. sesamiae. The efficiency ofIphiaulax sp. [Braconidae], the 2^nd most abundant larval parasite, was also hindered by the hyperparasite,Eurytoma sp. [Eurytomidae] Pupal parasites were sometimes very abundant reaching up to 100% parasitism without any interference by hyperparasites. The most abundant pupal parasites wereDentichasmias busseolae Heinrich [Ichneumonidae] andPediobius furvus (Gahan) [Eulophidae].      

Concurrently burrowing host fly larvae reciprocally enhance pupation depth to minimise parasitism risk

1. Variation in parasitism risk among hosts is a key factor influencing host–parasitoid interactions; however, within-patch variation (as opposed to between-patch variation) in parasitism risk has hardly been studied. This study investigated the mechanisms of within-patch variation in parasitism risk in the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). 2. Bactrocera dorsalis pupates underground. Previous studies have shown that pupae at greater depths have a reduced risk of parasitism by a pupal parasitoid Dirhinus giffardii (Silvestri) (Hymenoptera: Chalcididae). When a pupa near the ground surface is parasitised, the victim may decrease the risk of parasitism risk for pupae located at deeper depths. It was hypothesised that larvae will pupate at greater depths when they perceive the presence of conspecifics because of the benefit of pupating deeper than other individuals. 3. In a series of laboratory experiments, the effects of three factors on pupation depth were examined, including: (i) the density of larvae during development; (ii) the density of concurrently burrowing larvae; and (iii) the presence of pre-existing pupae in the pupation substrate. Only the density of concurrently burrowing larvae influenced pupation depth, which suggests that when a burrowing larva perceives the presence of other burrowing larvae, it aims to burrow deeper than them. 4. This study shows not only that parasitism risk is variable among pupae within a patch, but also that it is density-dependent. A commonly made assumption (i.e. the absence of within-patch variability in parasitism risk) needs to be re-evaluated in a wide range of host–parasitoid systems.     

The biology and behaviour ofIphiaulax varipalpis [Hymenoptera: Braconidae] as a parasite ofDirphya nigricornis [Coleoptera: Cerambycidae]

The ability of the braconid parasite,Iphiaulax varipalpis Cary to control the beetleDyrphya nigricornis Olivier was evaluated. Field collected samples and specimens reared in polyethylene paper tubes under laboratory conditions (23.0°C±1.0 at 70% r.h) were used. Field parasitism was low (10.72%) while laboratory parasitism was high (57.66%). The parasite detected the hosts very easily in the laboratory. This ability is minimised in thick canopies ofCoffea arabica L. Host colonization was brisk (90 seconds) and confined to a near absolute area of discovery, measuring 4.18±0.41 cm. The parasite reproduces gregariously with female lifespan being approximately double the male period. The parasites are very active at the age of 10 days. As they age their potential fecundity (232 oocytes) reduces drastically with oviposition.      

The influence of host distribution, sex, and size on the level of parasitism by Itoplectis conquisitor (Hymenoptera: Ichneumonidae)

Abstract. 1. Parasitism of the bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae), on red cedar was studied at Manassas, Va., U.S.A.
2. Fifteen parasitoids, five of which were hyperparasitoids, attacked the pupal stage of the bagworm. The Ichneumonid Itoplectis conquisitor alone accounted for 58% of the parasitized bagworms.
3. Parasitism by I conquisitor (Say) was inversely related to host size, but independent of host distribution within a tree. Male bagworms experienced disproportionately higher levels of parasitism than females. We conclude that it is small size that renders bagworms susceptible to parasitism rather than sex per se.
4. Ovipositor lengths of I.conquisitor were insufficient to penetrate the larger bagworm hosts (>57 mm); and in fact, as bagworm size increased, the proportion of the I.conquisitor population capable of penetrating the pupa declined abruptly. We suggest that the mechanical difficulties with oviposition, and perhaps the defensive capabilities of larger hosts, are responsible for the relationship between host size and per cent parasitism.
5. I.conquisitor could be an important selective agent for bagworm size at pupation, but it is not likely to act as a significant control agent of population density.     

Effect of modified meridic diet on the development and growth of tomato fruitworm Helicoverpa armigera (Lepidoptera: Noctuidae)

The efficacy of one new modified and two old meridic diets on Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) for rearing six successive generations was studied. Duration of larval development for insects fed on the modified diet was considerably shortened as most of them went through only five stadia before pupation, while the per cent pupation and per cent eclosion were relatively higher than on other diets. The lowest pupal mortality (6.33 ± 0.13%) was recorded in the F₁ generation reared on the modified diet, whereas the highest pupal mortality (19.49 ± 0.15%) was observed in insects reared on a natural diet in the F₆ generation. Blending of chickpea Cicer arietinum L. and red kidney bean Phaseolus vulgaris L. flours with tomato paste proved highly favorable for adult reproduction. These results suggest that the vitality of the tomato fruitworm did not decline obviously after rearing on a modified diet for several generations.     

The potential of trehalose to replace insect hemolymph in artificial media for Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae)

Insect additives have been shown to improve the value of artificial media for Trichogramma species, but at the same time maintain dependence on parallel cultures of host insects. In the present study, Trichogramma dendrolimi Matsumura was reared in vitro from egg to adult on artificial media with different contents of pupal hemolymph of Chinese oak silkmoth Antheraea pernyi (Guérin‐Méneville) and with supplements of distilled water, or of trehalose dissolved in water or in Grace's insect medium. The results indicated insect hemolymph was the key component of artificial medium. Developmental parameters, including rates of parasitism, pupation, adult emergence and normal adults, and numbers of produced adults, were increased on media supplemented with trehalose even when the proportion of pupal hemolymph was reduced. Two artificial media, the first containing 30% hemolymph and 10% trehalose in water with 98.9% parasitism rate, 77.7.0% pupation rate, 77.2% emergence rate, 80.0% normal adult rate and 333 produced adults, and the second containing 25% hemolymph and 15% trehalose in Grace's insect medium with 97.8% parasitism rate, 91.0% pupation rate, 85.2% emergence rate, 76.1% normal adult rate and 757 produced adults, were believed to hold potential to mass produce T. dendrolimi. The use of trehalose to partially replace pupal hemolymph in artificial medium of this and other Trichogramma species may contribute to a significant reduction in their production cost and may as such help to evade problems related to short supplies of lepidopteran eggs, which currently constitute the main factitious host for the mass rearing of the parasitoids.     

Assessment of Ceratitis capitata (Diptera,Tephritidae) pupae killed by heat or cold as hosts for rearing Spalangia cameroni (Hymenoptera: Pteromalidae)

In this work, we study the suitability of using dead medfly Ceratitis capitata pupae, killed by heat- or cold-shock, for the mass rearing of Spalangia cameroni, a pupal parasitoid of key pests. 100% mortality of medfly pupae could be accomplished with cold-shock at –20°C for 60 min or with heat-shock at 55°C for 30 min. Neither parasitism percentage nor sex ratio of the offspring differed significantly among heat-shocked, cold-shocked and untreated pupae. In addition, there was no significant difference in the percentage of parasitoids that aborted (♂♂ or ♀♀) among pupal treatments. Some of the pupae were covered with peat because the third larval instar of the medfly buries itself before pupation. However, the buried pupae were not parasitised at a greater or lesser rate than those not covered with peat. The percentage of parasitism was also unaffected by whether the pupae had been killed recently or had been stored at between 4°C and 6°C over 15 or 30 days. The use of dead hosts and later storage permitted the following: (a) the use of hosts over long periods of time; (b) a rapid increase in parasitoid numbers and (c) the availability of pupae killed at the most suitable postpupation times for the production of parasitoids. Furthermore, in biological control projects, the use of dead parasitised pupae in the field avoids the risk of enhancing the pest and allows an increase in parasitism in the field through the use of pupae treated with cold- or heat-shock.     

Coastal ecosystems on a tipping point: Global warming and parasitism combine to alter community structure and function

Mounting evidence suggests that the transmission of certain parasites is facilitated by increasing temperatures, causing their host population to decline. However, no study has yet addressed how temperature and parasitism may combine to shape the functional structure of a whole host community in the face of global warming. Here, we apply an outdoor mesocosm approach supported by field surveys to elucidate this question in a diverse intertidal community of amphipods infected by the pathogenic microphallid trematode, Maritrema novaezealandensis. Under present temperature (17°C) and level of parasitism, the parasite had little impact on the host community. However, elevating the temperature to 21°C in the presence of parasites induced massive structural changes: amphipod abundances decreased species‐specifically, affecting epibenthic species but leaving infaunal species largely untouched. In effect, species diversity dropped significantly. In contrast, four degree higher temperatures in the absence of parasitism had limited influence on the amphipod community. Further elevating temperatures (19–25°C) and parasitism, simulating a prolonged heat‐wave scenario, resulted in an almost complete parasite‐induced extermination of the amphipod community at 25°C. In addition, at 19°C, just two degrees above the present average, a similar temperature–parasite synergistic impact on community structure emerged as seen at 21°C under lower parasite pressure. The heat‐wave temperature of 25°C per se affected the amphipod community in a comparable way: species diversity declined and the infaunal species were favoured at the expense of epibenthic species. Our experimental findings are corroborated by field data demonstrating a strong negative relationship between current amphipod species richness and the level of Maritrema parasitism across 12 sites. Hence, owing to the synergistic impact of temperature and parasitism, our study predicts that coastal amphipod communities will deteriorate in terms of abundance and diversity in face of anticipated global warming, functionally changing them to be dominated by infaunal species.     

Dependence of juvenile hormone activity on haemolymph factor in Tenebrio molitor pupae

Morphogenetic response of Tenebrio molitor pupae to juvenile hormone (JH) varies with age, it being low during the first 6 hr after pupal ecdysis and reaching a peak at about 18 hr after ecdysis. Parabiosis of 6-hr pupa to a 18-hr-old pupa causes a higher morphogenetic response in 6-hr pupa to JH. A similar increase in morphogenetic response was not noticeable when a 0·45 μm Millipore filter was placed between the parabiotic partners, suggesting that the factor(s) may be macromolecular. This view is further supported by the observation that the Millipore filter did not prevent transport of ecdysterone another agent that enhances morphogenetic response of pupae to JH.     

Cost of strepsipteran macroparasitism for immature wasps: does sociality modulate virulence?

An important factor modulating parasite virulence is the level of extrinsic mortality experienced by hosts. Where it is high, parasites are expected to grow or reproduce quickly to complete their lifecycle before their host is killed, whereas virulence is expected to be less under low extrinsic mortality, where growth/reproduction can be slower. A prominent example of a low mortality environment for parasites are immature social insects. Here we examined the cost of parasitism, i.e. virulence, experienced by larval and pupal stages of Polistes wasps following infection by endoparasitic Strepsiptera (under starvation conditions). We found that there was no difference in virulence between infected and uninfected individuals for the seven days following infection; either measured as host mortality or mass loss. Likewise, there was no observed cost of parasitism during the first seven days of the pupal stage of the host. Growth of the endoparasitic stages appeared the same between starved laboratory individuals and field caught samples. Strepsipteran parasites apparently enter a lag phase until the later stages of host pupal development, which we speculate reduces the negative impact of parasitism during the hosts' critical developmental stages. Our results highlight the need for further inquiry into the influence of sociality upon the evolution of parasite virulence.     

Changes in abundance of native and introduced parasites (Hymenoptera: Braconidae), and of the target and non-target plant bug species (Hemiptera: Miridae), during two classical biological control programs in alfalfa.

High numbers of tarnished plant bugs [Lygus lineolaris (Palisot)], were once common in alfalfa, as was a low level of parasitism (9%) by the native Peristenus pallipes (Curtis). After the bivoltine European parasite Peristenus digoneutis Loan became well established, average parasitism of the first and second generations increased to 64%, and tarnished plant bug numbers dropped by 65%. This reduced host density eventually caused a decline in total parasitism by both parasite species to 22%. A few P. digoneutis also attacked the alfalfa plant bug, Adelphocoris lineolatus (Goeze), but did not reduce this pest or increase its parasitism rate. At another location, where P. digoneutis is not established, parasitism of first generation alfalfa plant bugs, an adventive (accidently introduced) pest, was increased to 21% by the introduced univoltine parasite, Peristenus conradi Marsh, and a slight reduction in the pest may have resulted. P. digoneutis did not parasitize the meadow plant bug, Leptopterna dolabrata (L.), an adventive pest of forage grasses, so did not affect this mirid or its parasite. Neither introduced parasite eliminated the native parasites of the tarnished or alfalfa plant bugs. The narrow host ranges of the braconid parasites of mirid nymphs are contrasted with the broad host range of the native tachinid parasite [Phasia robertsoni (Towns.)] of adult mirids. The major changes in mirid abundance and their mortality by parasites that slowly occurred during this 19-year study demonstrate the need for long-term field research, to adequately document and understand these complex interactions.     

Development of European corn borer larvae on Event 176 Bt corn: influence on survival and fitness

European corn borer larvae, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) that have completed development on Event 176 Bt corn hybrids have survived exposure to sublethal doses of the Cry1Ab Bt toxin or are exploiting plant tissues that do not express the toxin. To evaluate the impact of such exposure, diapausing larvae were collected from Event 176 and conventional hybrids and compared for rates of pupation, parasitism, fitness (pupal weight, longevity, and fecundity) and susceptibility to the Cry1Ab toxin. Larvae completing development on Event 176 corn exhibited approximately 10% higher survival rates and correspondingly lower parasitism rates than larvae completing development on conventional hybrids. No significant differences were detected in pupal weight, fecundity, longevity or susceptibility to the Cry1Ab Bt toxin. These results indicate that survival on Event 176 corn are not adversely affect fitness and does not cause increased tolerance to the Cry1Ab toxin in subsequent generations.     

A correlated response of a parasite’s virulence and life cycle to selection on its host’s life history

We demonstrate a correlated response of the virulence and the mode of transmission of the microsporidian parasite Edhazardia aedis to selection on the age at pupation of its host, the mosquito Aedes aegypti. We selected three lines of mosquitoes each for early or late pupation and exposed the larvae after zero, two and four generations of selection to a low and a high concentration of the parasite’s spores. Before selection the parasites induced a similar level of mortality in the six lines; after four generations of selection mortality was higher in the mosquitoes selected for late pupation than in those selected for early pupation. Overall, parasite-induced mortality was positively correlated with the mean age at pupation of the matching uninfected line. When they died, mosquitoes selected for early pupation harboured mostly binucleate spores, which are responsible for vertical transmission. Mosquitoes selected for late pupation were more likely to harbour uninucleate spores, which are responsible for horizontal transmission. The parasite enhanced this tendency for horizontal transmission by prolonging the larval period in the lines selected for late pupation, but not in the ones selected for early pupation. These results suggest that the genetic basis of the mosquito’s age at pupation helps to determine the parasite’s mode of transmission: parasites in rapidly developing mosquitoes are benign and transmit vertically, while parasites in slowly developing mosquitoes are virulent and transmit horizontally. Thus, as the host’s life history evolves, the parasite’s performance changes, because the host’s evolution changes the environment in which the parasite develops.     

Abundances of five parasitoids attacking the scale insect <Emphasis Type="Italic">Nipponaclerda biwakoensis</Emphasis> on morphologically changed reed shoots due to damage by a stem-boring caterpillar

Abundances of the scale insect Nipponaclerda biwakoensis and its five parasitoids per shoot of the common reed, Phragmites australis, were compared between shoots damaged by a stem-boring caterpillar and undamaged shoots. Reed shoots that were damaged by the stem-borer in spring change morphologically during summer, inducing tillers from the nodes beneath the damaged part. The number of female scales per shoot did not differ significantly between damaged and undamaged shoots in the second scale generation (September), but was significantly lower on damaged shoots in the third generation (November). Three parasitoid species attacking the scale exhibited different responses to the shoot damage, with the response by each parasitoid being constant in the two scale generations: the parasitism rate by Aprostocetus sp. per shoot was higher on damaged shoots, whereas that by Astymachus japonicus was lower on damaged shoots, and no difference was detected for Boucekiella depressa. In the third scale generation, the parasitism rate by Encyrtidae sp. 1 showed no difference, with respect to shoot damage, whereas that by Encyrtidae sp. 2 was lower on damaged shoots. In three dominant parasitoids, shoot damage had no effect on the number of emerging adults per host, and the sex ratio and body size of the adults. The number of emerging adults per shoot differed significantly between damaged and undamaged shoots for four parasitoids, except B. depressa. These results suggest that shoot damage by the stem-borer exerts a delayed negative impact on the scale numbers and affects the parasitism rate of the scales by three parasitoids and the emerging adult numbers of four parasitoids.     

Evaluation of the efficacy of Trichogramma evanescens Westwood (Hym., Trichogrammatidae) inundative releases for the control of Maruca vitrata F. (Lep., Pyralidae)

Abstract: The bean podborer, Maruca vitrata (F.), is a serious pest on leguminous crops in the tropics. There are several natural enemies of M. vitrata present in the Philippines, but none of them suppress pest populations naturally below an economic threshold. The egg parasite Trichogramma evanescens Westwood is commercially available for augmentative biological control and a known parasite of podborer eggs. The objective of the present study was to evaluate the efficacy of inundative releases of the egg parasite T. evanescens for controlling M. vitrata in the Philippines. In 1999 and 2000, controlled releases of T. evanescens were made in fields of yardlong bean, Vigna unguiculata, during the dry and rainy seasons in Central Luzon, Philippines. Adult populations of M. vitrata were monitored using light traps. Population density of M. vitrata was found to be positively correlated with rainfall and was subsequently higher during the rainy season, relative to that in the dry season. In quality control experiments, emergence of locally available T. evanescens was found to be highly variable between years, 72% in 1999 and 58% in 2000. The percentage of female parasites was 54% in both years. Survival of T. evanescens in the laboratory after 7 days was found to be only 29 and 21% in 1999 and 2000, respectively. Four parasite releases (each 150 000 wasps per hectare) spaced 7 days apart during the reproductive stage of V. unguiculata were made in three 5 × 5 m plots. Host finding efficacy was identified by exposing M. vitrata eggs laid on cowpea leaves in rearing chambers for 24 h in the fields. Percentage parasitism was higher during the dry season, relative to that in the rainy seasons. In release plots, parasitism increased by 53% during dry and by 43% during rainy season compared with control plots. Despite significant reductions in larval numbers during the dry season, no difference in percentages of pods damaged was found. In the rainy season, the number of larvae per plant and the percentage of pods damaged by M. vitrata larvae were not reduced by T. evanescens releases. The experimental results are critically discussed as a possible part of an integrated pest management system.     

Metazoan parasites of Brama australis from southern Chile: a tool for stock discrimination?

The metazoan parasites of 403 specimens of the southern ray's bream Brama australis from three localities in southern Chile (Lebu 36° 70′ S; 73° 40′ W, Calbuco 41° 50′ S; 73° 08′ W and Punta Arenas 53° 10′ S; 70° 50′ W) were recorded. More than 23 400 parasite specimens belonging to 12 taxa were registered. Metazoan parasites were dominated by the copepod Hatschekia conifera, constituting 97% of the total number of parasites; the larval cestode Hepatoxylon trichiuri was the second most important parasite (2·1% of the total number of parasites). The remaining 10 species constituted <1% of the metazoan parasites. Parasitological evidence, based on univariate and multivariate analysis, does not support the existence of discrete stocks in the studied zone.     

Regulatory processes and population cyclicity in laboratory populations ofAnagasta Kühniella (Zeller) (Lepidoptera: Phycitidae). III. The development of population models

1. Life table data for interactions between Anagasta kühniella and its ichneumon parasite Venturia canescens in two room ecosystems (A & B) have been analyzed in an attempt to explain and model each room situation. The life table data have been presented in the form of a graphical key-factor analysis, and have been further analyzed by an investigation of the density relationships between the different mortalities and the Angasta densities upon which the mortalities act.
2. In room A (1.2 gm food per container), the parasites were present throughout the interaction. Egg and early larval mortality (k₁) appeared to be directly density-dependent and was the sole stabilizing influence when introduced into the model for room A. The area of discovery of the parasite was relatively constant and its mean value was used to calculate parasitism (k₃) in the model. All other mortalities were density-independent and treated as being constant at their mean values. The model predicts a series of oscillations of decreasing amplitude which are somewhat similar to those observed in the Anagasta population during the early stages of the interaction. The observed mean densities of host and parasite were very close to those predicted.
3. In room B, the parasites were absent for the first 8 generations (1- 2gm food per container). Model B₁ covers this period and includes a direct density-dependent component describing changes in k₁, the remaining mortalities being constant. The observed mean densities approximate to the calculated densities. The parasites were present from the ninth generation and after the eleventh generation the food per container was increased to 7.2 gm. Model B₂ covers the period in room B from generation 11. The most important component of k₁ after the parasites were established is a delayed density-dependent one which appeared to be due to wounding of very small larvae by the probing activities of the parasites. Since the changes in k₁ could not be suitably predicted, the observed values were used in model B₂. This delayed component was not detected in room A due to the relatively small range of parasite densities in room A compared with the 600-fold change in densities in room B. The calculated area of discovery for the parasite population in each generation was found to vary inversely with searching parasite density, and this ‘interference relationship’ was used in the submodel for parasitism. Again, this relationship was not detected in room A due to the much smaller range of parasite densities there. Model B₂ gives oscillations in host and parasite populations arising from parasitism being a delayed density-dependent mortality. The correspondence with the observed oscillations is partly due to the actual k₁-values being used and partly because the submodel for parasitism adequately describes the observed changes in k₃. The tendency for these oscillations to decrease in amplitude is due to both the damping effect of parasite interference and the direct density-dependent component of k₁.

     

Parachordeumium amphiurae: a cuckoo copepod?

The impact of the endoparasitic copepod Parachordeumium amphiurae (=Amphiurophilus amphiurae of Goudey-Perrière, 1979) on a host population of the brooding, hermaphroditic ophiuroid Amphipholis squamata in intertidal rock pools in South Devon, UK was assessed. In August 1986 the parasite prevalence was 20.6% and the mean population intensity of infection 0.286 parasites per brittlestar. Female parasites inhabited the genital bursae of hosts and most were found in hosts that were potentially reproductively active. In such hosts brooding capacity was reduced by copepod parasitism. Infected brittlestars showed a reduction in numbers of brooded developmental stages when compared with uninfected hosts of similar size (but the mean size of brooded development stages was not affected). For the population sampled, the overall reduction in brooding capacity was about 44%. The association between Amphipholis and Parachordeumium was compared with normal brood parasitism.