Widespread historical presence of Batrachochytrium dendrobatidis in African pipid frogs

Aim Amphibian chytridiomycosis, an emerging infectious disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), is associated with global amphibian population declines and species extinctions. Current evidence indicates that the pathogen has recently spread globally from an enzootic focus, with Xenopus spp. (family Pipidae) in South Africa having been identified as a likely source. The aim of this study was to investigate further the likelihood of African Xenopus spp. as the original source of Bd. Location We examined 665 museum specimens of 20 species of African and South American pipid frogs collected between 1844 and 1994 and held in the collection of the Natural History Museum, London. Methods Skin brushings taken from adult amphibians and brushings from the mouthparts, lips and developing hind limbs of larval pipid frogs were examined for the presence of Bd using real‐time PCR. Results We found six cases of Bd infection in three Xenopus spp. (from Africa), but none of the South American pipids was positive, although only 45 South American frogs were available for examination. The earliest case of Bd infection was in a specimen of Xenopus fraseri collected from Cameroon in 1933. A consistently low prevalence of infection over time indicates that a historical equilibrium existed between Xenopus spp. and Bd infection in Africa. Main conclusions Our results suggest that Bd infection was present in Xenopus spp. across sub‐Saharan Africa by the 1930s, providing additional support for the ‘out of Africa’ hypothesis. If this hypothesis is correct, it strengthens the argument for stringent control of human‐assisted movements of amphibians and other wildlife world‐wide to minimize the likelihood of pathogen introduction and disease emergence that can threaten species globally. Our findings help inform species selection for conservation in the face of the current Bd pandemic and also guide future research directions for selecting Bd isolates for sequencing and virulence testing.     

Development of the suprarostral plate of Pipoid Frogs

The rostral region of nonpipoid tadpoles has two sets of cartilages, the cornua trabeculae and the suprarostral cartilages, whereas the rostral region in pipoid larvae is occupied by a single and continuous cartilage, the suprarostral plate. The homology of this region in pipoid and nonpipoids tadpoles has been controversial. We examined the early formation and development of the suprarostral plate using serially cross‐sectioned specimens of Rhinophrynus, Xenopus, and Hymenochirus. We conclude that the cartilaginous structures present in the rostral area of pipoid and nonpipoid larvae are homologous. Furthermore, we found two different developmental patterns among pipoid larvae. The chondrocranium of Hymenochirus boettgeri is described and illustrated to understand its developmental pattern and because of its uniqueness among pipoid chondrocrania. J. Morphol. 240:143–153, 1999. © 1999 Wiley‐Liss, Inc.     

Guinea-pig Vocalizations: Their Structure,Causation and Function

Feeding, mating behaviour, communication, breeding biology, and development of Pipa carvalhoi are described. Like in other species of the genus Pipa, the eggs are laid onto the ♀ back during several turnovers, and this behaviour cau be observed even in the absence of ♂♂ Acoustic communication involves a mating call and a combat call. The biology and behaviour of Pipa carvalhoi are compared to that of other pipid frogs, and it is suggested that the specialized breeding biology of the genus Pipa evolved as an adaptation to the life in small ponds and ditches which are rich in nutrients but poor in oxygen.     

Surface mesoderm in Xenopus: a revision of the stage 10 fate map

 We have used two complementary cell labeling techniques to investigate dorsal mesoderm formation in Xenopus laevis and Hymenochirus boettgeri. Epithelial grafts from fluorescently labeled donors into unlabeled hosts demonstrate that in Xenopus, as previously shown for Hymenochirus, superficial cells of the dorsal marginal zone have the ability to invade the notochord and somite and participate in their normal morphogenesis, in a stage-specific and region-specific manner. A new method for superficial fate mapping using cell surface biotinylation confirms this result for Hymenochirus and demonstrates that in Xenopus as well, even in normal development in the absence of surgical disruption, notochord and the most posterior somitic mesoderm originate partly in the superficial epithelial layer. This finding is contrary to the widespread belief that Xenopus mesoderm originates solely in the deep mesenchymal layer. In Xenopus (but not in Hymenochirus), the amount of superficial contribution to mesoderm varies, such that in some spawnings it appears not to be present, while in others it is evident in all or most embryos. Received: 13 May 1997 / Accepted: 17 July 1997     

Characterization of the host-defense peptides from skin secretions of Merlin's clawed frog Pseudhymenochirus merlini: Insights into phylogenetic relationships among the Pipidae

The family Pipidae comprises the genera Hymenochirus, Pipa, Pseudhymenochirus, Silurana, and Xenopus but phylogenetic relationships within the family are unclear. Peptidomic analysis of norepinephrine-stimulated skin secretions from Pseudhymenochirus merlini Chabanaud, 1920, the single species within the genus Pseudhymenochirus, led to identification of 13 host-defense peptides with antimicrobial activity. Two peptides (hymenochirin-1Pa and -1Pb) show structural similarity to hymenochirin-1B from Hymenochirus boettgeri and eight peptides (hymenochirin-5Pa, -5Pb, -5Pc, -5Pd, -5Pe, -5Pf, 5Pg and -5Ph) are structurally similar to each other and to hymenochirin-5B from H. boettgeri. Two peptides differing by a single amino acid (IKIPSFFRNILKKVGKEAVSLM/I AGALKQS), termed pseudhymenochirin-1Pa and -1Pb, and pseudhymenochirin-2Pa (GIFPIFAKLLGKVIKVASSLISKGRTE) do not resemble host-defense peptides previously isolated from pipid frogs. Hymenochirin-5Pe was the most abundant peptide in the secretions and hymenochirin-1Pa the most potent against Staphylococcus aureus (MIC = 2.5 μM) and Escherichia coli (MIC = 10 μM). The data support a close phylogenetic relationship between Hymenochirus and Pseudhymenochirus that is distinct from the Xenopodinae (Xenopus + Silurana) clade with Pipa sister-group to all other extant pipids.     

Functional response of suspension feeding anuran larvae to different particle sizes at low concentrations (Amphibia)

The influence of particle size, initial particle concentration and larval stage on the ingestion rate, ‘retention efficiency’, and filtering rate of anuran larvae with varying filter apparatus anatomy and different life histories was investigated for four species. Larvae of premetamorphic Stages 28 and 32 and prometamorphic Stage 40 were selected for filtering experiments on the basis of their different growth rates. Three different sizes of silica gel particles were offered as mock food. Particle concentration was measured photometrically. The Michaelis-Menten model was used to describe the dependency of ingestion rate, filtering rate, and ‘retention efficiency’ upon initial particle concentration, and to calculate maximum ingestion rate, threshold concentration, and the half-saturation constant. (1) The highest ingestion rates, filtering rates and ‘retention efficiencies’ were achieved by Xenopus laevis larvae, followed by Bufo calamita larvae. Bufo bufo larvae lay at the opposite end of the scale. Rana temporaria larvae were placed between B. calamita and B. bufo larvae. This order is attributed to differences in life histories, especially the different breeding environments in which these larvae occur. (2) The larger the particle size and the older the stage, the greater the tendency toward saturation of the ingestion rate, filtering rate and ‘retention efficiency’. These filtration parameters are graded according to particle size. The ingestion rate (number of particles), filtration rate and ‘retention efficiency’ are greatest for PS3. Ingestion volume is greatest for PS 1. The difference between PS3 and PS2 on the one hand, and PS1 on the other, is often great; for Stage 28 X. laevis it is very great. This shows that larvae ingest large particles more effectively, and that the most effective ingestion takes place at Stages 28 and 32, owing to the growth function of these stages. The ability of larvae to ingest large particles effectively is possibly a very basic phylogenetic characteristic. (3) The threshold concentration is lowest when the particles are at their largest. In accordance with conclusions drawn by other authors, threshold feeding is attributed to regulation by buccal pumping and mucus production. Considerable importance is attributed to threshold feeding with respect to larval adaptation to oligotrophic environments.     

Linking functional morphology and feeding performance in larvae of two coral-reef fishes

Despite the well acknowledged phenomenon that the biology of marine teleost fish larvae is much different from that of juvenile and adult conspecifics, very little is known about the changes in design of the feeding apparatus as larvae develop from hatching through metamorphosis. Furthermore, our understanding of the consequences of these developmental changes for feeding performance is very limited. In this study, we examined the relationship between the development of the feeding apparatus and feeding performance in larvae of Amphiprion ocellaris and Pseudochromis fridmani using cluster analysis, multi-dimensional scaling (nMDS), and canonical correspondence analysis (CCA). Several patterns emerge from our analyses. First, the state of development of the feeding apparatus increased in complexity through ontogeny, from a simple, hyoid-driven system at the onset of exogenous feeding to a more complex feeding system involving all adult functional elements of the cranium just prior to metamorphosis. Although the feeding apparatus converged to the hyoid-opercular-mandible linkage state around metamorphosis in both species, P. fridmani had a lesser developed hyoid-mandible linkage system relative to A. ocellaris at the onset of first-feeding. Second, first-feeding larvae fed on smaller, less elusive zooplankton. In contrast, larvae that survived beyond the first-feeding stage fed on more diverse prey types, including larger, more elusive zooplankton. Third, intra- and inter-specific variation in the development of the feeding apparatus is associated with variation in feeding performance. The post-hatch developmental trajectory in both species showed a pattern consistent with stage (i.e., ontogenetic state)-specific shifts in morphology and performance. Furthermore, the number of developmental transitions in both feeding functional morphology and feeding performance differ between species that exhibit contrasting incubation periods.     

Effects of hind limb denervation on the development of appendicular ossicles in the Dwarf African Clawed Frog,Hymenochirus boettgeri (Anura: Pipidae)

Sesamoids and other appendicular ossicles are common in other classes of vertebrates but comparatively rare in amphibians. The pipid frog Hymenochirus boettgeri (Boulenger, G. A. 1899. On Hymenochirus, a new type of aglossal batrachians. – Annals of the Magazine of Natural History Series 7: 122–125) is unusual among anurans in having seven (or more) appendicular ossicles in each hind limb. Sesamoids are often associated with muscles and tendons, and their development is usually regarded as mediated by or correlated with function. This study investigated the effects of paralysis (loss of function) on development of ossicles in the hind limb of Hymenochirus. Complete denervation of the right sciatic nerve was performed at developmental stages 63 and 66, and the animals maintained for a further 6–7 or 12–13 weeks. Specimens were cleared and double stained for cartilage and bone. There were no gross morphological differences between control and sham operated groups. The lunulae were not affected by paralysis, whereas the fabella arose later and/or regressed in some specimens. The distal os sesamoides tarsalia (OST) was shorter in paralysed individuals, and both the distal OST and cartilagines plantares showed delayed maturation. Denervation of the hind limb thus affected the timing of appearance, maintenance and rate of maturation of some sesamoid bones in Hymenochirus, but had no effect on others.     

The cranial osteology and hyolaryngeal apparatus of Rhinophrynus dorsalis (Anura: Rhinophrynidae) with comparisons to recent pipid frogs

The cranial osteology (including the hyolaryngeal apparatus) of Rhinophrynus dorsalis (Anura: Rhinophrynidae) is described from whole skeletons and serial cross sections. Some unique features of the extensively ossified skull include the enlarged and protracted olfactory region, for which the nasals form part of the septum nasi; the relatively short maxillaries and broad premaxillaries, and the immense quadratojugal; the extreme forward position of the quadrate; the lack of a firm articulation of the pterygoid and quadrate with the neurocranium and crista parotica; the quadrate lacking the distinct processes typical of other frogs; a single foramen for Nn. II–VII; a large, distinct operculum; and a bipartite hyale. Rhinophrynus shares other unusual cranial characteristics with the other pipoid frogs, Xenopus, Pipa, Hemipipa, and Hymenochirus. Among these features are the presence of a single frontoparietal in the adult, and the absence of parasphenoid alae, palatines, and mentomeckelian bones. Rhinophrynus differs from the pipids in the lack of a columella and a palatine process on the premaxilla, and in the possession of a quadratojugal, parahyoid bone, paired prevomers, olfactory eminence, massive quadrate that lacks distinguishable processes, a modified squamosal, and a bipartite hyale. Although the cranium of Rhinophrynus is distinctive, the evolutionary significance of its unusual features will remain obscure until comparable data are gathered from other closely related groups, the Discoglossoidea and the Pelobatoidea.     

Lack of physiological improvement in performance of Callosamia promethea larvae on local host plant favorites

Summary As a species, the promethea silkmoth, Callosamia promethea (Saturniidae: Lepidoptera) exhibits a wide host range on 6–10 families of plants, although specific populations are known to have local foodplant favorites. We tested the hypothesis that larvae from a particular host plant lineage would show physiological adaptations to this host compared with larvae from other host plant lineages. We found no evidence that larval survival and growth was any better for larvae fed the natural plant of the parental population than for larvae from other host lineages. These natural host lineages include: black cherry (Prunus serotina Ehrh.), tuliptree (Liriodendron tulipifera L.), sassafras (Sassafras albidum (Nutt.) Nees) and spicebush (Lindera benzoin (L.) Blume). The only apparent manifestation of physiological specialization was the inability of tuliptree lineages of C. promethea to survive on paper birch (Betula papyrifera Marsh), although this may reflect the geographical pattern of adaptation to birch, rather than a negative correlation with adaptation to tuliptree. These results suggest that for C. promethea larvae, growth performance and survival is primarily influenced by plant nutritional quality, rather than physiological adaptations to the locally preferred host plant.     

Comparison of gregariousness in larvae and adults of four species of zetoborine cockroaches

Insects observed in groups in nature may be gathered either by attractants from the environment or by conspecifics. Field distribution data alone are thus insufficient to assess congregation by conspecifics and complementary laboratory tests of spacing patterns are required. Such tests were performed in four species of Zetoborinae (Insecta, Blattaria), for which field studies showed differences in spatial distribution (Schultesia lampyridiformis Roth, Phortioeca nimbata Burmeister, Lanxoblatta emarginata Burmeister and Thanatophyllum akinetum Grandcolas). Gregariousness, mobility, and sticking to shelters were compared between these four species. Tests were performed on pairs of adults of the same sex and opposite sexes, and also on first instar larvae, either in isolation or in groups of two and four individuals. In S. lampyridiformis, adults were strongly gregarious, whereas larvae dispersed early after birth and were very mobile during the first instar. In P. nimbata, larvae and adults were gregarious, while in L. emarginata larvae were weakly gregarious, and gregariousness decreased when density increased. Adults of L. emarginata seemed to be indifferent to each other. Larvae and adults of T. akinetum were solitary and they actively dispersed. The varying levels of gregariousness among species are discussed according to the known ecological habits in Zetoborinae.     

Temporal and developmental aspects of diet-induced food preferences in larvae of the tobacco hornworm, Manduca sexta

Diet‐induced changes in food preferences in an oligophagous caterpillar were studied in order to characterize the conditions under which this induction occurs. The time course of acquisition and extinction of induced food preferences by larvae of the tobacco hornworm, Manduca sexta (Johan.) (Lepidoptera, Sphingidae), was examined by varying the food and duration of larval food experience. Larvae were given feeding experience with the host plant tomato, Lycopersicon esculentum (Mill.) (Solanaceae), or the acceptable non‐host plant cowpea, Vigna unguiculata (Walp.) (Fabaceae), or switched from one to the other during different instars. Food preferences for V. unguiculata by the fourth or fifth instar larvae were measured individually in two‐choice tests with discs of V. unguiculata and moist filter paper. The acquisition or extinction of an induced food preference for V. unguiculata was indicated by larvae preferring V. unguiculata to filter paper or the reverse, respectively. Results showed that: (1) the period required for the acquisition of induced preference for V. unguiculata can be short (36 h), (2) food experience in either the third or fourth instar period is sufficient, and (3) the most recent feeding experience appears to be important. In contrast, the period required for extinction of induced preference for V. unguiculata appeared to be longer (1–3 instars), and both the most recent feeding experience and total duration of larval experience with the inducing food seem to play a role. Experience is not restricted to a particular instar period to acquire or extinguish such an induced food preference. The induced food preference for V. unguiculata was not very rigid and could be reversed by having one instar of feeding experience on L. esculentum. The findings indicate that diet‐induced food preferences in M. sexta contains elements of habituation and associative learning, but do not support food imprinting and induction of oligophagy.     

The filter apparatus of Rana temporaria and Bufo bufo larvae (Amphibia,Anura)

Summary In larvae of Rana temporaria and Bufo bufo the location of filter apparatus within the larval organization, the arrangement of the morphological parts as branchial food trap, ventral velum, and filter rows, as well as their surface anatomy, are similar to that of other species of Orton's larval type IV. The means by which mucous with its entrapped food particles is transported from the filter rows to the esophagus is finally resolved. The dorsally positioned ciliary cushion extends far ventrally between the filter plates. From their contact with the filter rows, the cilia transport the mucous to Kratochwill's caudally positioned Flimmerrinne and from there to the esophagus. The original chordate principle of mucous entrapment and ciliary transport is thus retained by these anuran larvae. The only modification specific to the latter is the division into a ventral filter apparatus, whose epithelia serve for mucus entrapment, and a dorsal ciliary area.Six different types of cell may be distinguished ultrastructurally: (1) The ubiquitous squamous epithelium with merocrine extrusions; (2) the large supporting cells of the filter rows and of the ventral velum; (3) the ciliary cells of the ciliary cushion; (4) three different types of mucous producing secretory cells: (a) A type of cell similar to the goblet cell is found in the ciliary cushion (merocrine extrusion); (b) The secretory pits of the ventral velum and the secretory ridges have similar bottle-shaped merocrine secretory cells; (c) The merocrine apical cells of the filter rows are the final kind. It is evident that the ciliary cushion epithelium resembles that of both the manicotto glandulare of anuran larvae and the trachea and bronchus of Mammalia.Supported by the Deutsche Forschungsgemeinschaft-DFG     

Suspension feeding of anuran larvae at low concentrations of Chlorella algae (Amphibia,Anura)

Summary Ingestion and filtering rates in larval Xenopus laevis, Bufo calamita, Rana temporia and Bufo bufo fed suspensions of Chlorella fusca were investigated. Concentrations were measured with a Coulter Counter. (1) For all species, filtration occurred at concentrations far below those reported by other authors for Rana sylvatica feeding on Chlorella pyrenoidosa. For Bufo bufo, only larvae near metamorphosis showed ingestion at low particle concentrations. Since buccopharyngeal ventilation continues even in the absence of food particles, this threshold feeding behaviour in the younger larvae must be due to different mechanisms to those found in Daphnia and Calanus studied by other authors: probably reduction of the buccal pumping rate and the mucus production of the filter apparatus. (2) For B. calamita, R. temporaria and X. laevis the highest suspension feeding efficiency was at early tadpole stages, corresponding with the high growth rate of these stages. (3) The life histories of the species provide the basis for understanding their different retention efficiencies and functional responses.Supported by the Deutsche Forschungsgemeinschaft-DFG     

Influence of toxic and non-toxic phytoplankton on feeding and survival of Dreissena polymorpha (Pallas) larvae

Grazing and survival of larvae of the zebra mussel, Dreissena polymorpha, on a green alga and cyanobacteria were studied in laboratory experiments. Clearance rates of the larvae were determined for Chlamydomonas reinhardtii (green alga), two non-toxic and two toxic Microcystis aeruginosa strains (Cyanobacteria). Clearance rates of larvae on non-toxic Microcystis were significantly higher than on toxic Microcystis. The clearance rate on Chlamydomonas reinhardtii was in between the clearance rates on toxic and non-toxic Microcystis strains and not significantly different from them. Effects of toxicity of Microcystis on the survival of zebra mussel larvae was investigated in a short-term experiment. Survival of larvae fed toxic Microcystis was lower than that of larvae fed non-toxic Microcystis, but higher than that of starved larvae. This may imply that, for survival of zebra mussel larvae, it is better to have bad quality (toxic) food than no food.     

Dytiscus latissimus and D. circumcinctus (Coleoptera,Dytiscidae) larvae as predators on three case-making caddis larvae

The predacious behaviour of Dytiscus circumcinctus and D. latissimus larvae was studied experimentally. When offered different prey simultaneously, D. latissimus larvae preferred cased caddis larvae relative to mayfly nymphs and isopods, whereas in D. circumcinctus the preference order was reversed. Notonectid nymphs and tadpoles were consumed in higher numbers by D. circumcinctus than by D. latissimus larvae. D. circumcinctus larvae and instar III larvae of D. latissimus most frequently captured caddis larvae through the case wall, whereas the instar I and II larvae of D. latissimus normally attacked the thorax of the exposed larva from above the front opening of the case. Limnephilus borealis, L. nigriceps and L. rhombicus caddis larvae differed in case structure, and they were all successfully captured by D. latissimus and D. circumcinctus instar II and III larvae. Neither capture success nor ingestion efficiency varied significantly between the two Dytiscus species or between different prey species. Instar II and III D. circumcinctus larvae had shorter reaction times than those of D. latissimus. The larger L. borealis and L. rhombicus larvae were preferred by the two last Dytiscus larval instars, and the handling time of these two prey was longer than that of L. nigriceps larvae.     

Diet-induced food preference by Manduca sexta larvae: acceptable non-host plants elicit a stronger induction than host plants

Diet-induced changes in food preference by fifth instar larvae of the tobacco hornworm, Manduca sexta (Johan.) (Lepidoptera, Sphingidae), were examined. Two groups of larvae with different diet experience were used: larvae reared on a host or on an acceptable non-host plant species. Each group of larvae was offered a choice between leaf discs from each rearing plant species (2-plant choice test) and food preference was measured as the consumption of one plant species relative to that of the other plant species. Diet-induced changes in preferences were larger with the host versus acceptable non-host plant pairs Solanum pseudocapsicum (L.) versus Raphanus sativus (L.), Lycopersicon esculentum (Mill.) versus Vigna sinensis (Savi), and Datura innoxia (L.) versus V. sinensis than with the host versus host plant pairs L. esculentum versus Capsicum annuum (L.) and L. esculentum versus D. innoxia. To examine how much the food preference had been altered for each test plant species alone, two other groups of larvae were offered a choice between leaf discs from a single plant species and filter paper discs laced with distilled water (1-plant choice test). Larvae preferred the dietary plant species more strongly than the non-dietary plant species in tests using the following plant species: for C. annuum with C. annuum and L. esculentum as diets, for V. sinensis with V. sinensis and L. esculentum or D. innoxia as diets, and for R. sativus with R. sativus and S. pseudocapsicum as diets. The preference for the hosts L. esculentum and D. innoxia did not change significantly after rearing larvae on different hosts or on an acceptable non-host. Thus, diet-induction by M. sexta larvae results in an enhancement of preference for the dietary plant species which is much stronger with acceptable non-hosts than with hosts.     

Monophyly of Euaesthetinae (Coleoptera: Staphylinidae): phylogenetic evidence from adults and larvae,review of austral genera,and new larval descriptions

Abstract We develop a morphological dataset for the rove beetle subfamily Euaesthetinae comprising 167 morphological characters (135 adult and 32 larval) scored from 30 terminal taxa including 25 ingroup terminals (from subfamilies Euaesthetinae and Steninae) and five outgroups. Four maximum parsimony analyses using different sets of terminals and character sets were run to test the monophyly of (1) Euaesthetinae, (2) Steninae, (3) Euaesthetinae + Steninae, (4) euaesthetine tribes Austroesthetini, Alzadaesthetini, Euaesthetini, Fenderiini and Stenaesthetini, and (5) the ten currently known austral endemic genera together. Analyses of adult and larval character sets separately and in combination recovered the monophyly of Euaesthetinae, Steninae, and both subfamilies together, with strong support. Analysis of 13 ingroup terminals for which complete data were available suggests that monophyly of Euaesthetinae is supported by 19 synapomorphies (13 adult, six larval), of Steninae by 23 synapomorphies (14 adult, nine larval), and of both subfamilies together by 24 synapomorphies (21 adult, three larval). Within Euaesthetinae, only the tribe Stenaesthetini was recovered as monophyletic based on adult characters, and in no analyses were the ten austral endemic genera recovered as a monophyletic group. Phylogenetic relationships among euaesthetine genera were weakly supported, although analyses including adult characters supported monophyly of Octavius and Protopristus separately, and of Octavius + Protopristus, Austroesthetus + Chilioesthetus and Edaphus + Euaesthetus. Steninae may include a third genus comprising two undescribed species probably possessing a ‘stick–capture’ method of prey capture, similar to that in Stenus. These two species formed a strongly supported clade recovered as the sister group of Stenus based on adult characters. Diagnoses and a key to adults are provided for the 15 euaesthetine genera currently known from the austral region (Australia, New Zealand, South Africa and southern South America). Euaesthetine larvae previously were known only for Euaesthetus, and we describe the larvae of nine more genera and provide the first larval identification key for genera of Euaesthetinae.