Host nest defense against a color-dimorphic brood parasite: great reed warblers (Acrocephalus arundinaceus) versus common cuckoos (Cuculus canorus)

We tested great reed warbler (Acrocephalus arundinaceus) discrimination against two common cuckoo (Cuculus canorus) female color morphs (gray and rufous) in two areas with different parasitism rates and proportions of the two morphs. Hosts recognized the two cuckoo morphs from a control, the feral pigeon (Columba livia), at Apaj, Hungary (where brood parasitism was heavy), whereas no significant differences among the models were recorded at Lužice, Czech Republic (where the parasitism rate was moderate). At Apaj, the hosts discriminated the rufous morph (which is slightly predominant there) better than the gray morph from the control. Between-site comparison (after controlling for background aggression) revealed that great reed warblers were more aggressive towards the rufous morph at Apaj than at Lužice, whereas their responses to the gray morph did not differ, corresponding with much higher between-site difference in the relative abundance of the rufous morph. Our results suggest that both local parasitism pressure and relative abundance of two female color morphs of a brood parasite may significantly influence host nest defenses.     

A comparative study of host selection in the European cuckoo Cuculus canorus

Certain kinds of hosts are commonly regarded as being more suitable than other for rearing European cuckoos (Cuculus canorus) – insectivores that lay small eggs and have open, shallow nests – although empirical tests of cuckoo host selection are lacking. We analysed host use by the European cuckoo in 72 British passerines that are potential hosts and for which there was information available on life-history variables and variables related to cuckoo-host coevolution, such as rate of parasitism, rejection rate of non-mimetic model eggs and degree of cuckoo-egg mimicry of host eggs. The relative population size of the host species affected parasitism rate most strongly, followed by relatively short duration of the nestling period, and the kind of nest, with cuckoos selecting open-nesting hosts. However, the effect of the nestling period could be related to host body size and the kind of nest used, because hole-nesting species normally have longer nestling periods than open-nesters. We re-analysed the data excluding hole nesters and corvid species (species with larger body mass), but the results remained identical. The European cuckoo may benefit from selecting hosts with short nestling periods because such hosts provide food for their nestlings at a very high rate. When only those species known as cuckoo hosts were analysed, the variable that best accounted for the parasitism rate was duration of the breeding season. Therefore, availability of potential hosts in both time and space is important for cuckoos in selecting hosts. Received: 16 July 1998 / Accepted: 27 October 1998     

Additions to knowledge of the Yellow-throated Glossy Cuckoo,Chrysococcyx flavigularis

Summary A series of eight specimens of the yellow-throated glossy cuckoo,Chrysococcyx flavigularis, recently collected in Bwamba Forest, western Uganda, and the field observations accompanying them give our first information on the courtship habits, call notes, and feeding range of the species, and extend our knowledge of its breeding season. It is now possible to demonstrate extensive sympatry withC. klaas, and also to present further details of its plumages.Zusammenfassung Eine unter Leitung vonR. Glen undA. Williams stehende Expedition zur Erforschung der isolierten Waldgebiete West-Ugandas konnte für das Los Angeles County Museum of Natural History im Bwamba-Urwald 8 Exemplare des noch wenig bekannten Gelbkehlkuckucks,Chrysococcyx flavigularis (Shelley), sammeln.Überdies ergab die Beobachtung der lebenden Vögel erstmals Aufschluß über Balzverhalten, Stimme und Nahrung dieses Kuckucks. Der Gonadenzustand der gesammelten Vögel legt im Verein mit den Feststellungen anderer Autoren die Annahme nahe, daß sich die Fortpflanzungszeit dieser Art über einen großen Teil des Jahres erstreckt.Chrysococcyx flavigularis kommt in einem ausgedehnten Gebiet neben der anscheinend nächstverwandten Art,Ch. klaas, vor; auch im Bwamba-Urwald leben beide sympatrisch. Die Maße der gesammelten Vögel werden angegeben und Einzelheiten der Gefiederfärbung und -zeichnung beschrieben.     

Determinants of reproductive success in the Rufous Bush Robin(Cercotrichas galactotes)

Summary Over a 3-year period, we studied determinants of reproductive success in a population of the migratory Rufous Bush Robin (Cercotrichas galactotes) parasitized by the Common Cuckoo (Cuculus canorus). Seasonal reproductive success (as measured by the number of fledglings produced) depended on the number of successful broods raised. Many breeding attempts failed owing to predation, probably by cuckoos, which mainly affected first and replacement clutches. Clutch size did not follow the general trend for multi-brooded species (mid-season peak), but showed a maximum early in the season, perhaps a consequence of delayed arrivals due to the negative effects of nest predation and parasitism through cuckoos. Interannual differences in several variables of breeding success might be explained by marginally significant between year differences in the number of nests depredated and/or parasitized. Breeding success appeared to be independent of parental body size, but female condition (as measured by the number of light bands) had a powerful effect, with females in poor condition having less fledglings in the season, and lower fledging success (proportion of nestlings that fledged) and nesting success (proportion of eggs that produced fledglings), than females in prime condition. Furthermore, age influenced breeding success, with old individuals producing more and heavier fledglings in the season than did yearlings. Poor breeding success or partner condition were unlikely to initiate divorce, but rates of nest predation, which are probably linked to the male contribution in nest defence, appeared to increase the probability of divorce.

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Der Bruterfolg in einer Population des Heckensängers(Cercotrichas galactotes)

Zusammenfassung Von 1993 – 1995 wurde in einer vom Kuckuck (Cuculus canorus) parasitierten Population des Heckensängers (Cercotrichas galactotes) im südliche Spanien untersucht, welche Faktoren den Bruterfolg bestimmen. Der Gesamtreproduktionserfolg (Anzahl flügge Jungvögel) war abhängig von der Anzahl erfolgreicher Bruten. Viele Brutversuche blieben wegen Prädation, wohl durch den Kuckuck, erfolglos, was vornehmlich Erst- und Ersatzbruten betraf. Die Gelegegröße war nicht, wie bei anderen Mehrfachbrütern, zur Mitte der Brutzeit am größten, sondern zu Beginn. Ursache hierfür könnte eine verspätete Rückkehr der Vögel ins Brutgebiet sein, die ihrerseits eine Folge der frühen Nestprädation und der Parasitierung durch den Kuckuck sein könnte. Jährliche Unterschiede werden mit Unterschieden in der Prädationsrate und/oder der Parasitierungsrate erklärt. Der Bruterfolg war unabhängig von der elterlichen Körpergröße. Die Kondition der Weibchen, gemessen an den Wachstumsstreifen im Großgefieder, hatte jedoch einen starken Einfluß. Schwächere Weibchen hatten einen signifikant geringeren Schlüpf-, Ausfliege- und Gesamtbruterfolg als konditionell stärkere Weibchen. Zudem hatten ältere Vögel einen besseren Bruterfolg und kräftigere Junge als Jungvögel in ihrem ersten Brutjahr. Nestprädation, aber nicht geringer Bruterfolg oder physische Kondition der Partner, erhöhte die Scheidungsrate von Paaren.

     

The Diachasmimorpha longicaudata complex: Reproductive isolation and geometric patterns of the wing

Diachasmimorpha longicaudata is an endoparasitoid of Tephritid fruit fly larvae and is regarded as an important biocontrol agent. However, it is likely that under this specific name several biological species may be contained, the correct identification of which is essential for effective use in control programs. In this paper, three populations (DLA, DLB and DLBB) of D. longicaudata designated according to geography and/or natural hosts were reared in the same laboratory. They were tested for reproductive compatibility and characterized by morphometric analyzes. Forced-contact mating technique showed either complete lack of inter-population reproductive compatibility or the production of rare, sterile female offspring. The three populations, indistinguishable on the basis of morphological characters alone, were readily identified by the geometry of the wing. Results strongly suggest that the DLA, DLB and DLBB are distinct biological species, and highlight the usefulness of wing geometry to distinguish them.     

UV reflectance of eggs of brown-headed cowbirds (Molothrus ater) and accepter and rejecter hosts

Many hosts of obligate brood parasites accept parasitic eggs despite the high costs of parasitism. Acceptance is particularly perplexing in brown-headed cowbird (Molothrus ater) (hereafter “cowbird”) hosts because the eggs of cowbirds and most hosts do not appear to match closely in visual characteristics detectable by humans. However, recent evidence suggests that parasite and host eggs may match in their ultraviolet (UV) reflectance, undetectable by humans, and that birds may use UV signals for egg discrimination. We determined whether egg colour matching in UV reflectance separates accepters and rejecters of cowbird parasitism by comparing the total UV (300–400 nm) reflectance of the eggs of 11 host species to cowbird eggs. Eggs of three of five accepter species and five of five rejecter species differed significantly from cowbird eggs in UV reflectance. We found no significant difference in the UV reflectance of the eggs of three closely related pairs of accepter and rejecter species. There also was no significant difference in the UV reflectance of cowbird eggs laid in nests of five host species, and the UV reflectance of cowbird eggs was not significantly correlated with that of host clutches. Thus, we found no support for the UV-matching hypothesis in brown-headed cowbirds and UV reflectance does not appear to separate accepters and rejecters of parasitism. Differences in UV reflectance between cowbird and host eggs, however, provide potential cues for use in egg discrimination. Experimental testing is needed to determine the relative importance of UV reflectance compared to other visual cues.     

Reproductive biology of the predator Macrolophus caliginosus: Effect of age on sexual maturation and mating

Macrolophus caliginosus is a polyphagous mirid bug native to the Mediterranean area where it is widely used as a biological control agent, both in protected and open-field vegetable crops. Its reproductive biology remains largely unknown and a better understanding of it will improve mass rearing and release strategies. In the present work, we studied the development of reproductive organs in females and males and how age conditioned receptiveness to mating in both sexes.Females with mature eggs in their ovarioles appear 3–4 days after adult molt with a similar pattern of ovary maturation in virgin females as in females that were kept with males of the same age. Newly molted males were found to already have active sperm in their seminal vesicles but their accessory glands did not completely develop until 3 days later. Receptivity for copulation paralleled ovarian and accessory gland maturation.     

Micro-evolutionary change and population dynamics of a brood parasite and its primary host: the intermittent arms race hypothesis

A long-term study of the interactions between a brood parasite, the great spotted cuckoo Clamator glandarius, and its primary host the magpie Pica pica, demonstrated local changes in the distribution of both magpies and cuckoos and a rapid increase of rejection of both mimetic and non-mimetic model eggs by the host. In rich areas, magpies improved three of their defensive mechanisms: nest density and breeding synchrony increased dramatically and rejection rate of cuckoo eggs increased more slowly. A stepwise multiple regression analysis showed that parasitism rate decreased as host density increased and cuckoo density decreased. A logistic regression analysis indicated that the probability of changes in magpie nest density in the study plots was significantly affected by the density of magpie nests during the previous year (positively) and the rejection rate of mimetic model eggs (negatively). These results are consistent with a hypothesis (the intermittent arms race hypothesis) of spatially structured cyclic changes in parasitism. During periods of parasitism, host defences continuously improve, and as a consequence, the fitness gains for parasites decrease. When host defences against parasites reach a high level, dispersing parasites have a selective advantage if they are able to emigrate to areas of low resistance. Once parasites have left an area hosts will lose their defensive adaptations due to their cost in the absence of parasitism. The scene is then set for re-colonization by great spotted cuckoos. Received: 7 May 1998 / Accepted: 24 August 1998     

Reproductive biology and female parental care in the cockscomb prickleback,Anoplarchus purpurescens (Pisces: Stichaeidae)

Synopsis Reproduction and parental care in the cockscomb prickleback, a Pacific coast intertidal fish, were examined using a combination of field and laboratory observations. The sexes were dimorphic, particularly during the breeding season, and males competed with other males for access to females. Males performed lateral and spasm displays. In the wild, the breeding season extended from January to March on cobblestone beaches. Assortative mating was positive with respect to body size. Females exhibited solitary parental care of the eggs. Each female coiled around, guarded and fanned a single egg mass that likely represented her total reproductive effort for the year. The number of eggs in the mass increased linearly with female size (weight or length). Males did not remain after spawning. Aquarium observations revealed that males spawn with more than one female given the opportunity. It is not known whether this occurs in the wild. Incubation to hatching took 29 days. Upon hatching, the young swam towards the surface. Parental care did not extend beyond hatching.     

Origin and early evolution of the vertebrates: new insights from advances in molecular biology, anatomy, and palaeontology

Recent advances in molecular biology and microanatomy have supported homologies of body parts between vertebrates and extant invertebrate chordates, thus providing insights into the body plan of the proximate ancestor of the vertebrates. For example, this ancestor probably had a relatively complex brain and a precursor of definitive neural crest. Additional insights into early vertebrate evolution have come from recent discoveries of Lower Cambrian soft body fossils of Haikouichthys and Myllokunmingia (almost certainly vertebrates, possibly related to modern lampreys) and Yunnanozoon and Haikouella (evidently stem-group vertebrates). The earliest vertebrates had an unequivocally marine origin, probably evolved mineralised pharyngeal denticles before the dermal skeleton, and evidently utilised elastic recoil of the visceral arch skeleton for suction feeding. Moreover, the new data emphasise that the advent of definitive neural crest was supremely important for the evolutionary origin of the vertebrates.     

Reproductive biology,oogenesis and early development in the brood-caring sea anemoneActinostola spetsbergensis (Anthozoa: Actiniaria)

Summary 1.Actinostola spetsbergensis Carlgren from different Atlantic and Pacific localities has been found to reproduce sexually during the arctic summer.2. Oogenesis of the remarkably few eggs proceeds inside the conspicuous and histologically altered layers of mesogloea and endoderm.3. The fertilized egg and all subsequent developmental stages up to the 24 septa stage are surrounded by a peculiar non-cellular envelope by means of which they adhere in the upper part of their mother's interior.4. Cleavage is superficial and endoderm seems to be formed by combined processes of invagination and multipolar immigration.5. The elaborate brood-care is assumed to be of special importance for achieving successful development inA. spetsbergensis.6. By contrast to other brooding anemones there are special brood caring mechanisms, including particular precautions for the developing egg.7. The reproductive and brooding particularities ofA. spetsbergensis have adaptative significance in respect to the ecological conditions of the arctic region.

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Fortpflanzungsbiologie, Oogenese und frühe Larvalentwicklung der brutpflegenden AktinieActinostola spetsbergensis (Anthozoa: Actiniaria)

Kurzfassung Während der Fortpflanzungszeit im arktischen Sommer erzeugen die vonA. spetsbergensis Carlgren Oocyten, die durch ihre Hülle aus umfangreicher Mesogloea und histologisch stark verändertem Ovarial-Endoderm auffallen; die Anzahl der sich pro Weibchen entwickelnden Eier ist ungewöhnlich gering. Das befruchtete Ei löst sich aus dem Ovar, verläßt jedoch das Muttertier nicht, sondern wird mit Hilfe seiner nichtzelligen Hülle im oberen Teil des Körpers befestigt. Dort verläuft die Embryonal- und Larvalentwicklung bis zu fortgeschrittenen Larvenstadien (meist bis zum 24-Septen-Stadium). Die Furchung ist eine modifizierte Superfizialfurchung, das Endoderm scheint durch eine Kombination von Invagination und polarer Immigration zu entstchen. Im Gegensatz zu anderen brutpflegenden Aktinien besitztA. spetsbergensis besondere Einrichtungen, die der Brutpflege dienen, wobei die Fürsorge für die Nachkommen schon während der Oogenese beginnt. Die ökonomische Eiproduktion in Verbindung mit einer hochspezialisierten Brutpflege läßtA. spetsbergensis besonders gut an die ökologischen Bedingungen arktischer Lebensräume angepaßt erscheinen.

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Member of the Taxonomische Arbeitsgruppe at the Biologische Anstalt Helgoland.     

Reproductive biology of Fopius ceratitivorus (Hymenoptera: Braconidae), an egg–larval parasitoid of the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The reproductive biology of Fopius ceratitivorus Wharton, a recently discovered African parasitoid, was studied in quarantine in Hawaii to facilitate its mass production for biological control of the Mediterranean fruit fly, Ceratitis capitata. Mean longevity of host-deprived and ovipositing females was 17.3 ± 0.9 d and 16.2 ± 0.5 d, respectively. Ovarian maturation peaked at 61.6 mature eggs per female on the fifth day after eclosion and declined thereafter. Mean number of offspring produced per day by mated females was 5.1 ± 0.4, and realized fecundity expressed as total eggs deposited during the female’s life time was 107.8 ± 12.8. Females were more attracted, to and reproduced significantly more, in fruit substrates containing odors of adult flies and eggs rather than fruit substrates artificially inoculated with fly eggs. Our findings suggest that F. ceratitivorus is a promising new parasitoid for biological control of C. capitata in Hawaii.     

Morphological,Molecular, and Phylogenetic Characterization of Nosema ceranae,a Microsporidian Parasite Isolated from the European Honey Bee,Apis mellifera1

ABSTRACT. Nosema ceranae, a microsporidian parasite originally described from Apis cerana, has been found to infect Apis melllifera and is highly pathogenic to its new host. In the present study, data on the ultrastructure of N. ceranae, presence of N. ceranae-specific nucleic acid in host tissues, and phylogenetic relationships with other microsporidia species are described. The ultrastructural features indicate that N. ceranae possesses all of the characteristics of the genus Nosema. Spores of N. ceranae measured approximately 4.4 × 2.2 μm on fresh smears. The number of coils of the polar filament inside spores was 18–21. Polymerase chain reaction (PCR) signals specific for N. ceranae were detected not only in the primary infection site, the midgut, but also in the tissues of hypopharyngeal glands, salivary glands, Malpighian tubules, and fat body. The detection rate and intensity of PCR signals in the fat body were relatively low compared with other examined tissues. Maximum parsimony analysis of the small subunit rRNA gene sequences showed that N. ceranae appeared to be more closely related to the wasp parasite, Nosema vespula, than to N. apis, a parasite infecting the same host.     

Brood size, sex ratio and egg load of Metaphycus lounsburyi (Hymenoptera: Encyrtidae) when parasitizing adult females of black scale Saissetia oleae (Hemiptera: Coccidae) in the field

Black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae) is a widespread olive pest in California and Europe. Metaphycus lounsburyi (Howard) (Hymenoptera: Encyrtidae) is often one of its main parasitoids. Augmentative releases of M. lounsburyi have been proposed in those areas in which biological control is ineffective. In this paper, we study the relationship between black scale and M. lounsburyi in the field. According to our data, M. lounsburyi parasitizes mainly ovipositing females of black scale. Parasitism rates of ovipositing females reach high levels. In those scales, M. lounsburyi develops as a gregarious parasitoid, with an average of 13 and a maximum of 40 parasitoids developing per scale. The secondary sex ratio is female biased (proportion of males = 0.13) and appears to be brood size dependent. Metaphycus lounsburyi eggs are encyrtiform; however, its egg load is much higher than other Metaphycus that also parasitize black scale. The implications of these results on the behavioral ecology of M. lounsburyi and its use in biological control of black scale are discussed.     

Comparisons of digestive function between the European hare (Lepus europaeus) and the European rabbit (Oryctolagus cuniculus): Mastication, gut passage, and digestibility

The European hare Lepus europaeus and the European rabbit Oryctolagus cuniculus are sympatric in many areas of the world. They are medium-sized herbage-feeding lagomorphs and trophic competitors. Both species feed on twigs under extreme and perhaps limiting conditions. To ascertain whether fine niche separation mechanisms occur, several comparative tests of digestive function were undertaken on samples of animals drawn from sympatric populations. The weights of the organs constituting the abdominal alimentary canal, the rates of passage and the extent of trituration of dietary markers intended to mimic twigs, and the digestibility of fibre, protein, and fat were compared. Both the stomach and the caecum of the hare were significantly smaller as a proportion of body weight, and this would result in a higher power–weight ratio. Both species rapidly passed the digestive marker, but passage was significantly faster in the hare. The rabbit chewed twig-like material with a scissor cutting and crushing action, whereas the action of the hare included a stripping action that would more efficiently access soluble carbohydrates stored in vascular rays. Both species were poor digesters of fibre, but digestibility of hemicelluloses was significantly greater in the rabbit. The faeces of both species of lagomorphs contain nutrients that can be attractive to more efficient fermenters of plant fibre, and consumption of those faeces may confound lagomorph population surveys that rely on dung counts.     

Comparative aspects of the thermal biology of the short-tailed gerbil, Desmodillus auricularis, and the bushveld gerbil, Tatera leucogaster

1. 1. The response of oxygen consumption (VO₂), thermal conductance (C_d and C_min, body temperature (T_b), and evaporative water loss (EWL) of Tatera leucogaster and Desmodillus auricularis were measured over the range of ambient temperatures (T_a) from 5–35°C.

2. 2. Basal metabolic rate (BMR) of T. leucogaster was 0.841 ± 0.049 ml O₂ g⁻¹ h⁻¹ and lower than predicted, while that of D. auricularis was similar to the expected value (1.220 ± 0.058 ml O₂ g⁻¹ h⁻¹). D. auricularis had a high, narrow thermoneutral zone (TNZ) typical of nocturnal, xerophilic, burrowing rodents.

3. 3. D. auricularis and T. leucogaster regulated T_b over the range T_a = 5–35°C and kept EWL and dry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above T_a = 30°C.

4. 4. After comparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.

Inoculative releases of Trichogramma ostriniae for suppression of Ostrinia nubilalis (European corn borer) in sweet corn: field biology and population dynamics

The effectiveness of inoculative releases of Trichogramma ostriniae Pang and Chen for suppression of Ostrinia nubilalis (Hübner) in sweet corn was assessed. Early-season, low-density (75,000 females ha⁻¹) releases were made, and establishment, levels of parasitism and sex ratios of emerging T. ostriniae quantified. T. ostriniae established effectively for each season that they were released, but appeared to be unable to overwinter. Parasitism levels tracked egg mass numbers closely, and T. ostriniae persisted in fields even where insecticides were applied. Parasitism by indigenous Trichogramma species was 3%. Field populations of T. ostriniae were distinctly female biased (78%), with males produced in the majority of broods. Numbers of males did not increase linearly with number of O. nubilalis eggs parasitized, but appeared to remain constant above an egg mass size of about 20 eggs. A Type-I functional response to increasing egg and egg mass density was found under field conditions, where the proportion of egg masses parasitized remained constant with increasing egg mass density. A relatively consistent percentage of eggs per egg mass was parasitized, with a linear increase in number of eggs parasitized with increasing number of eggs per egg mass. These results show that T. ostriniae established viable reproductive populations in sweet corn following inoculative release, with the potential to contribute to reduced dependence on insecticides for the control of O. nubilalis in an integrated pest management program.