Sexual dimorphism, extrapair fertilizations, and operational sex ratio in great frigatebirds (Fregata minor)

Across taxa, the presence of sexual ornaments in one sex isusually correlated with disproportionately great parental effortby the other. Frigatebirds (Fregatidae) are sexually dimorphic,with males exhibiting morphological and behavioral ornaments,but males and females share in all aspects of parental effort.All other taxa in a clade of 237 species exhibit biparentalcare, but only frigatebirds exhibit pronounced sexual dimorphism. We tested for the presence of two factors that could contributeto the evolution of male ornaments in great frigatebirds: ahigh frequency of extrapair fertilizations and a male-biasedoperational sex ratio. In 92 families sampled over two breedingseasons, there was only one extrapair fertilization. However,in both seasons, there were more males than females availablefor mating, and the sex ratio among individuals actively engagedin mate-acquisition behavior was strongly male biased, withtypically five or six males available per female. Our resultssuggest that extrapair fertilizations are not responsible forthe exaggeration of sexual ornaments in male frigatebirds,and that operational sex ratio may be related to sexual dimorphismin this species. Further work is needed to determine whetherthe male-biased operational sex ratio creates the variancein male reproductive success that would be needed to drivethe evolution of male ornaments.     

Combining Methods to Describe Important Marine Habitats for Top Predators: Application to Identify Biological Hotspots in Tropical Waters

In tropical waters resources are usually scarce and patchy, and predatory species generally show specific adaptations for foraging. Tropical seabirds often forage in association with sub-surface predators that create feeding opportunities by bringing prey close to the surface, and the birds often aggregate in large multispecific flocks. Here we hypothesize that frigatebirds, a tropical seabird adapted to foraging with low energetic costs, could be a good predictor of the distribution of their associated predatory species, including other seabirds (e.g. boobies, terns) and subsurface predators (e.g., dolphins, tunas). To test this hypothesis, we compared distribution patterns of marine predators in the Mozambique Channel based on a long-term dataset of both vessel- and aerial surveys, as well as tracking data of frigatebirds. By developing species distribution models (SDMs), we identified key marine areas for tropical predators in relation to contemporaneous oceanographic features to investigate multi-species spatial overlap areas and identify predator hotspots in the Mozambique Channel. SDMs reasonably matched observed patterns and both static (e.g. bathymetry) and dynamic (e.g. Chlorophyll a concentration and sea surface temperature) factors were important explaining predator distribution patterns. We found that the distribution of frigatebirds included the distributions of the associated species. The central part of the channel appeared to be the best habitat for the four groups of species considered in this study (frigatebirds, brown terns, boobies and sub-surface predators).     

Long-term isolation of a highly mobile seabird on the Galapagos

The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds (Fregata magnificens) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and morphological variation across the distribution of magnificent frigatebirds. Concordant with predictions from life-history traits, we found signatures of extensive gene flow over most of the range, even across the Isthmus of Panama, which is a major barrier to gene flow in other tropical seabirds. In contrast, individuals from the Galapagos were strongly differentiated from all conspecifics, and have probably been isolated for several hundred thousand years. Our finding is a powerful testimony to the evolutionary uniqueness of the taxa inhabiting the Galapagos archipelago and its associated marine ecosystems.     

Does a calmodulin-dependent Ca2+-regulated Mg2+-dependent ATPase contribute to hepatic microsomal calcium uptake?

Solubilization of microsomal proteins followed by calmodulin affinity chromatography resulted in the separation of two distinct Ca2+-Mg2+-ATPases (Ca2+-regulated Mg2+-dependent ATPases), one being insensitive to calmodulin (ATPase-1), the other being stimulated about 5-fold by calmodulin (ATPase-2). ATPase-2 accounts for only 8% of total microsomal Ca2+-Mg2+-ATPase-activity. ATPase-1 and -2 can also be distinguished by different pH optima, different sensitivity towards inhibition by vanadate and LaCl3, and different apparent Mr values of the phosphoenzyme intermediates (115,000 and 150,000 for ATPase-1 and ATPase-2 respectively). ATPase-1 from liver co-migrated with Ca2+-Mg2+-ATPase from rat skeletal-muscle sarcoplasmic reticulum, whereas ATPase-2 from liver co-migrated with calmodulin-dependent Ca2+-Mg2+-ATPase derived from rat skeletal-muscle sarcolemma. After separation of parenchymal and nonparenchymal liver cells, a calmodulin-dependent Ca2+-Mg2+-ATPase of Mr 150,000 was found only in the non-parenchymal cells. The kinetic parameters of ATPase-2 and the similarity of the apparent Mr of its phosphoenzyme intermediate to that of skeletal-muscle sarcolemma Ca2+-Mg2+-ATPase makes it likely that the calmodulin-sensitive Ca2+-Mg2+-ATPase found in rat liver microsomal fractions reflects a contamination with plasma membranes (possibly from non-parenchymal cells) rather than a true location in the endoplasmic reticulum of parenchymal liver cells.     

Haemoproteus iwa in Great Frigatebirds (Fregata minor) in the Islands of the Western Indian Ocean

Blood parasites of the sub-genus Haemoproteus have been reported in seabirds, in particular in species in the Suliformes order. These parasites are transmitted by hippoboscid flies of the genus Olfersia; strong specificity has been suggested between the vector and its vertebrate host. We investigated the prevalence of Haemoproteus infection in Suliformes and hippoboscid flies in two oceanic islands of the Western Indian Ocean: Europa and Tromelin. In total, 209 blood samples were collected from great frigatebirds (Fregata minor), masked boobies (Sula dactylatra) and red-footed boobies (Sula sula). Forty-one hippoboscid flies were also collected from birds. Seventeen frigatebirds and one fly collected on Europa tested positive for the presence of Haemoproteus parasites by polymerase chain reaction. Phylogenetic analyses based on partial sequences of the Cytochrome b gene showed that parasites were closely related to Haemoproteus iwa reported from frigatebirds in the Pacific Ocean and in the Caribbean. Plasmodium was also detected in a frigatebird on Europa; however, its placement on the phylogenetic tree could not be resolved. We provide strong support for transmission of blood parasites in seabirds in the Western Indian Ocean and suggest that migrations between the Pacific and the Indian oceans could favor the large-scale distribution of Haemoproteus iwa in frigatebird populations.     

Barriers acting on the genetic structure of a highly aerial seabird: The magnificent frigatebird

The sometimes-distant association between dispersal movements and mating strategies may govern seabird ecology. Despite their large dispersal capability, pelagic seabirds are subject to the influence of physical and non-physical barriers that may limit the magnitude of realized effective dispersal and gene flow. The Magnificent Frigatebird (Fregata magnificens) is a widespread, tropical, pelagic, sequentially monogamous seabird capable to breach physical barriers, such as land masses. Nevertheless, Mexican frigatebirds have shown movement preferences by sex (female migration and high male site fidelity), which, along with the complex female mate choice behavior, may promote breeding isolation. In order to ascertain if levels of population structure are influenced by physical or non-physical barriers, we analyzed mitochondrial DNA variation of adult Magnificent Frigatebirds breeding in the main nesting colonies in Mexico, three in the eastern Pacific Ocean and one in the Caribbean Sea. Control region sequences revealed significant genetic structure between Pacific and Caribbean frigatebirds (AMOVA, Φ_SC = 0.105, P < 0.0001), but none among Pacific breeding colonies (non-significant pairwise Φ_ST). Whereas the C-haplotype was shared by Pacific and Caribbean frigatebirds, the T-haplotype was absent in the Caribbean. Genetic differentiation between ocean basins and available evidence of Mexican frigatebird movements suggest that in spite of the capability of frigatebirds to breach physical barriers, movement preferences by sex and mate selection acting in a large inter-oceanic scale are the prime behaviors promoting population structure, which is highly consequential for their conservation.     

Carotenoids and throat pouch coloration in the great frigatebird (Fregata minor)

Carotenoid pigments are a common source of red, orange, and yellow coloration in vertebrates. Animals cannot manufacture carotenoids and therefore must obtain them in their diet to produce carotenoid-based coloration. Male great frigatebirds (Fregata minor) display a bright red inflated gular pouch as part of their elaborate courtship display. The basis of this coloration until now has not been investigated. Using high-performance liquid chromatography (HPLC), we investigated the types and concentrations of carotenoids that great frigatebirds circulate in their plasma and whether male gular pouch coloration was carotenoid-based. Great frigatebird plasma collected during the breeding season contained three carotenoid pigments in dilute concentrations-tunaxanthin, zeaxanthin, and astaxanthin-with astaxanthin accounting for nearly 85% of the carotenoids present. Astaxanthin was the only carotenoid present in gular pouch tissue, but the concentration is the highest reported for any carotenoid-pigmented avian tissue. Throat pouch reflectance curves were measured with a UV-VIS spectrophotometer, revealing a complex pattern of one UV peak (approx. 360 nm), two absorption valleys (approx. 542 and 577 nm), followed by a plateau at approx 630 nm. The reflectance curve suggests a role for additional pigments, in particular hemoglobin, in the production of color in this ornament.     

Two overlapping genes in bovine mitochondrial DNA encode membrane components of ATP synthase.

Two hydrophobic proteins have been purified to homogeneity from a mixture of about 13 proteins that are extracted from bovine mitochondria with a chloroform:methanol mixture. Sequence analysis shows that the smaller is a protein of 66 amino acids and is the product of a mitochondrial gene, A6L. The larger, a protein of 226 amino acids, is ATPase-6, a membrane component of ATP synthase, also encoded in mitochondrial DNA. The protein sequences determined establish that the genes for the two proteins overlap by 40 bases and indicate that translation of the second gene, ATPase-6, is initiated within the coding region of A6L. The A6L and the ATPase-6 proteins have also been isolated from the ATP synthase complex and so appear to be bona fide components of the enzyme. The function of A6L is unknown. However, weak structural homology suggests a functional similarity to the yeast mitochondrial protein, aapI, which is required for assembly of the fungal ATP synthase complex. Homologies between ATPase-6 and subunit a of the Escherichia coli ATP synthase complex indicate that the ATPase-6 protein has a similar role in the mitochondrial complex to its bacterial counterpart, being essential for the formation of an active proton channel.     

Phosphorus-31 nuclear magnetic resonance studies of bioenergetics in wild-type and adenosinetriphosphatase(1-) Escherichia coli cells

By use of 31P NMR, the transmembrane pH gradient (delta pH) and the intracellular levels of phosphorylated metabolites were measured in aerobic suspensions of wild-type Escherichia coli cells in the presence and absence of the adenosinetriphosphatase (ATPase) inhibitor dicyclohexylcarbodiimide (DCCD); the same parameters were also determined in E. coli mutants deficient in ATPase activity under both anaerobic and aerobic conditions. A method is described by which dense suspensions of E. coli cells (approximately 3 X 10(11) cells/mL) were oxygenated so that steady-state O2 levels in the suspensions were far greater than the Km for O2 consumption. Under these conditions, in wild-type MRE600 cells, the intracellular concentrations of PI, NTP, and NDP were measured to be 3.0 +/- 1.5, 8 +/- 1, and 1.2 +/- 1 mM, respectively, while the intracellular pH was approximately 7.5 over the external pH range studied (6 to approximately 7.0). Upon treatment with DCCD, the intracellular NTP level was drastically reduced and intracellular Pi concentration increased in respiring wild-type cells; in the same cells, however, DCCD did not affect the intracellular pH and the delta pH. During respiration in the presence of lactate, ATPase- cells established a delta pH but failed to synthesize any detectable levels of NTP. Conversely, ATPase- cells accumulated high levels of NTP but did not generate a delta pH during glycolysis under anaerobic conditions. These results are in complete agreement with the generally accepted chemiosmotic hypothesis. 31P NMR data on intact ATPase- NR70 cells were in agreement with the previously proposed [Rosen, B. P., Brey, R., & Hasan, S. (1978) J. Bacteriol. 134, 1030] existence of a proton leak in this strain which is sealed by DCCD or by spontaneous mutation into strain NR71. However, the NMR data also indicated that other major differences exist between NR71 and NR70 cells.     

Novel Haemoproteus species (Haemosporida: Haemoproteidae) from the swallow-tailed gull (Lariidae), with remarks on the host range of hippoboscid-transmitted avian hemoproteids

Haemoproteus (Haemoproteus) jenniae n. sp. (Haemosporida: Haemoproteidae) is described from a Galapagos bird, the swallow-tailed gull Creagrus furcatus (Charadriiformes, Laridae), based on the morphology of its blood stages and segments of the mitochondrial cytochrome b (cyt b) gene. The most distinctive features of H. jenniae development are the circumnuclear gametocytes occupying all cytoplasmic space in infected erythrocytes and the presence of advanced, growing gametocytes in which the pellicle is closely appressed to the erythrocyte envelope but does not extend to the erythrocyte nucleus. This parasite is distinguishable from Haemoproteus larae, which produces similar gametocytes and parasitizes closely related species of Laridae. Haemoproteus jenniae can be distinguished from H. larae primarily due to (1) the predominantly amoeboid outline of young gametocytes, (2) diffuse macrogametocyte nuclei which do not possess distinguishable nucleoli, (3) the consistent size and shape of pigment granules, and (4) the absence of rod-like pigment granules from gametocytes. Additionally, fully-grown gametocytes of H. jenniae cause both the marked hypertrophy of infected erythrocytes in width and the rounding up of the host cells, which is not the case in H. larae. Phylogenetic analyses identified the DNA lineages that are associated with H. jenniae and showed that this parasite is more closely related to the hippoboscid-transmitted (Hippoboscidae) species than to the Culicoides spp.-transmitted (Ceratopogonidae) species of avian hemoproteids. Genetic divergence between morphologically well-differentiated H. jenniae and the hippoboscid-transmitted Haemoproteus iwa, the closely related parasite of frigatebirds (Fregatidae, Pelecaniformes), is only 0.6%; cyt b sequences of these parasites differ only by 1 base pair. This is the first example of such a small genetic difference in the cyt b gene between species of the subgenus Haemoproteus. In a segment of caseinolytic protease C gene (ClpC), genetic divergence is 4% between H. jenniae and H. iwa. This study corroborates the conclusion that hippoboscid-transmitted Haemoproteus parasites infect not only Columbiformes birds but also infect marine birds belonging to Pelecaniformes and Charadriiformes. We conclude that the vertebrate host range should be used cautiously in identification of subgenera of avian Haemoproteus species and that the phylogenies based on the cyt b gene provide evidence for determining the subgeneric position of avian hemoproteids.     

Testosterone levels and gular pouch coloration in courting magnificent frigatebird (Fregata magnificens): variation with age-class, visited status and blood parasite infection

Male magnificent frigatebirds (Fregata magnificens) possess a seasonally expressed skin ornament, namely the red and inflatable gular pouch, and are, therefore, a convenient model for the study of some theories related to the evolution of possible testosterone-dependent sexual skin coloration. Here we report the findings of a study performed over four consecutive mating seasons in the Mexican national park Isla Isabel. We investigated differences in testosterone level and gular pouch coloration in courting males in relation to the categories: age-class, visited status and blood parasite infection. Gular pouch color saturation increased with age-class. Investigated frigatebirds were infected only with Haemoproteus iwa (Haemosporida, Haemoproteidae), with an overall prevalence infection of 15.5%. Prevalence of the infection increased with birds' age-class. Testosterone levels were significantly higher in infected males, who also had lighter colored gular pouches. In non-infected males, those visited by a female had higher testosterone levels than non-visited males. Gular pouch lightness and redness were negatively correlated but only redness in non-visited non-infected males was positively correlated with testosterone levels. Gular pouch saturation in visited and infected males was positively correlated with body mass, which also increased with age-class. Mated males had lower testosterone levels and lighter, less red and saturated gular pouch coloration than courting males. In summary, we found that coloration of the male skin ornament could reflect age-class (saturation), parasite infection (lightness) and mated status (all), together with indications of condition and testosterone dependency of ornament expression.     

Diversity of migration strategies among great frigatebirds populations

Migratory behavior varies extensively between bird taxa, from long distance migration to purely sedentary behavior. Variability in migratory behavior also occurs within taxa, where individuals within some species, or even populations, show mixed strategies. The same variability occurs in seabird species. We examined the migratory behavior of distinct populations of great frigatebirds Fregata minor in three distant oceanographic basins. Great frigatebird populations showed extensive variation in post‐breeding migratory behavior. Birds from Europa Island (Mozambique Channel) made long‐distance migration to numerous distinct roosting sites in the Indian Ocean, New Caledonia birds made shorter distance migrations to roosting sites in the southwestern Pacific Ocean, and Galapagos birds were resident within the archipelago year round. Juvenile birds from Europa Is. and New Caledonia dispersed widely whereas Galapagos juveniles were resident year round. The migratory behavior of Europa Is. and New Caledonia resulted in complete separation of foraging grounds between breeding adults, non‐breeding adults, and juveniles, whereas in the Galapagos the overlap was complete. We suggest that population variability in migratory behavior may have arisen because of different environmental conditions at sea, and also depends on the availability of suitable roosting sites on oceanic islands. The results also highlight the capacity of frigatebirds to remain airborne most of the time even outside the breeding season when they have to molt.     

BIOLOGY AND BEHAVIOUR OF FRIGATEBIRDS FREGATA SPP. ON ALDABRA ATOLL

Both species nested in mixed colonies in mangrove trees. The tops of trees were usually occupied exclusively by minor and the lower parts by ariel, but most nests of both species were in the intermediate parts of the canopy. The main laying season for both species was July to January. A census showed about 27 000 individuals present at the height of the season (1500 breeding pairs of minor, 5350 of ariel). Seasonal variation in numbers could be accounted for almost entirely by the changes in breeding activity of a resident population. Young of both species were fed at or near the nest-site for at least four months after fledging. A recovery near Bombay of a wing-tagged immature ariel shows that this species, at least, undergoes a post-fledging dispersal; it is suggested that young minor either do not disperse, or do so later than ariel. Food samples collected from chicks showed no overall difference between the species, but a seasonal analysis showed that ariel took more squid than minor in the wet season, and in the dry season the two species took different proportions of the two commonest species of flying-fish. Chicks of ariel received smaller meals than minor chicks in the wet season, but similar-sized meals in the dry season; ariel chicks grew more slowly than minor chicks. It is suggested that the timing of the breeding season is related to the need for adults to build up fat reserves to carry them through the courtship, nest-building and laying periods, when they are tied to the colony and so have little opportunity to feed. The evidence for non-annual breeding in frigatebirds is discussed. It is concluded that while successful breeders must breed at intervals of more than 12 months, they could theoretically nest in two successive seasons and that, since breeding success is low, most individuals probably do so. Existing knowledge of the biology of four of the five recognized species of frigatebirds is summarized, and shows that the family is at least as uniform as the tropicbirds and much more so than other Pelicaniformes.     

Phylogeography of the Mekong mud snake (Enhydris subtaeniata): the biogeographic importance of dynamic river drainages and fluctuating sea levels for semiaquatic taxa in Indochina

During the Cenozoic, Southeast Asia was profoundly affected by plate tectonic events, dynamic river systems, fluctuating sea levels, shifting coastlines, and climatic variation, which have influenced the ecological and evolutionary trajectories of the Southeast Asian flora and fauna. We examined the role of these paleogeographic factors on shaping phylogeographic patterns focusing on a species of semiaquatic snake, Enhydris subtaeniata (Serpentes: Homalopsidae) using sequence data from three mitochondrial fragments (cytochrome b, ND4, and ATPase-2785 bp). We sampled E. subtaeniata from seven locations in three river drainage basins that encompassed most of this species' range. Genetic diversities were typically low within locations but high across locations. Moreover, each location had a unique suite of haplotypes not shared among locations, and pairwise φ(ST) values (0.713-0.998) were highly significant between all location pairs. Relationships among phylogroups were well resolved and analysis of molecular variance (AMOVA) revealed strong geographical partitioning of genetic variance among the three river drainage basins surveyed. The genetic differences observed among the populations of E. subtaeniata were likely shaped by the Quaternary landscapes of Indochina and the Sunda Shelf. Historically, the middle and lower Mekong consisted of strongly dissected river valleys separated by low mountain ranges and much of the Sunda Shelf consisted of lowland river valleys that served to connect faunas associated with major regional rivers. It is thus likely that the contemporary genetic patterns observed among populations of E. subtaeniata are the result of their histories in a complex terrain that created abundant opportunities for genetic isolation and divergence yet also provided lowland connections across now drowned river valleys.     

Genomic ancestry of the American puma (Puma concolor)

Puma concolor, a large American cat species, occupies the most extensive range of any New World terrestrial mammal, spanning 110 degrees of latitude from the Canadian Yukon to the Straits of Magellan. Until the recent Holocene, pumas coexisted with a diverse array of carnivores including the American lion (Panthera atrox), the North American cheetah (Miracynonyx trumani), and the saber toothed tiger (Smilodon fatalis). Genomic DNA specimens from 315 pumas of specified geographic origin (261 contemporary and 54 museum specimens) were collected for molecular genetic and phylogenetic analyses of three mitochondrial gene sequences (16S rRNA, ATPase-8, and NADH-5) plus composite microsatellite genotypes (10 feline loci). Six phylogeographic groupings or subspecies were resolved, and the entire North American population (186 individuals from 15 previously named subspecies) was genetically homogeneous in overall variation relative to central and South American populations. The marked uniformity of mtDNA and a reduction in microsatellite allele size expansion indicates that North American pumas derive from a recent (late Pleistocene circa 10,000 years ago) replacement and recolonization by a small number of founders who themselves originated from a centrum of puma genetic diversity in eastern South America 200,000-300,000 years ago. The recolonization of North American pumas was coincident with a massive late Pleistocene extinction event that eliminated 80% of large vertebrates in North America and may have extirpated pumas from that continent as well.     

Archaeal RecA homologues: different response to DNA-damaging agents in mesophilic and thermophilic Archaea

Two archaeal proteins, RadA and RadB, share similarity with the RecA/Rad51 family of recombinases, with RadA being the functional homologue. We have studied and compared the RadA and RadB proteins of mesophilic and thermophilic Archaea. In growing cells, RadA levels are similar in mesophilic Methanococcus species and the hyperthermophile Methanococcus jannaschii. Treatment of cells with mutagenic agents (methylmethane sulfonate or UV light) increased the expression of RadA (as evidenced by higher levels of both mRNA and protein) in all organisms tested, but the increase was greater in the mesophiles than in the thermophiles M. jannaschii and Sulfolobus solfataricus. Recombinantly expressed RadA proteins from the mesophile M. voltae and the thermophile M. jannaschii were similar in their ATPase- and DNA-binding activities. All the data are consistent with proposals that RadA plays the same role as eukaryotic Rad51. Surprisingly, the data also suggested that the thermophiles do not need more RadA protein or activity than the mesophiles. On the other hand, RadB is not coregulated with RadA, and its role remains unclear. Neither RadA nor RadB from a mesophile or from a thermophile rescued the UV-sensitive phenotype of an Escherichia coli recA- host.     

Lineage sorting in multihost parasites: Eidmanniella albescens and Fregatiella aurifasciata on seabirds from the Galapagos Islands

Parasites comprise a significant percentage of the biodiversity of the planet and are useful systems to test evolutionary and ecological hypotheses. In this study, we analyze the effect of host species identity and the immediate local species assemblage within mixed species colonies of nesting seabirds on patterns of genetic clustering within two species of multihost ectoparasitic lice. We use three genetic markers (one mitochondrial, COI, and two nuclear, EF1‐α and wingless) and maximum likelihood phylogenetic trees to test whether (1) parasites show lineage sorting based on their host species; and (2) switching of lineages to the alternate host species depends on the immediate local species assemblage of individual hosts within a colony. Specifically, we examine the genetic structure of two louse species: Eidmanniella albescens, infecting both Nazca (Sula granti) and blue‐footed boobies (Sula nebouxii), and Fregatiella aurifasciata, infecting both great (Fregata minor) and magnificent frigatebirds (Fregata magnificens). We found that host species identity was the only factor explaining the patterns of genetic structure in both parasites. In both cases, there is evident genetic differentiation depending on the host species. Thus, a revision of the taxonomy of these louse species is needed. One possible explanation of this pattern is extremely low louse migration rates between host species, perhaps influenced by fine‐scale spatial separation of host species within mixed colonies, and low parasite infrapopulation numbers.     

On the respiratory quotient (RQ) of termites (Insecta: Isoptera)

The respiratory quotient (RQ) at 28 degrees C was determined by Warburg manometry in 23 species of termites from the Mbalmayo Forest Reserve (Cameroon) and three sub-tropical species cultured under laboratory conditions in the U.K. or freshly collected in Australia. The data are tabulated with other recently reported RQs (determined by manometry or GC) and with measured CH(4) emission rates to provide a survey of 29 species covering both lower and higher termites in all major trophic (functional) categories. In all species, except the wood-feeding Coptotermes acinaciformis and the soil-feeding Cubitermes fungifaber, the observed mean values (with manometry corrected for known fluxes of H(2) and CH(4)) were at or well above 1.00. Soil-feeding forms (except C. fungifaber) generally showed a high apparent RQ (not corrected for H(2)), with nine species (out of 13) above 1.20 and six species above 1.30. Well-replicated laboratory experiments with Reticulitermes lucifugus showed that there was a tendency for RQ to fall with time over a 4-h incubation, although remaining greater than 1.00.The observed RQs are consistent with carbohydrate being the principal substrate supporting respiration in all trophic and taxonomic categories, with little or no contribution from the degradation of lignin or other polyaromatic materials. However, in many species (especially soil-feeders), the observed RQ is greater than that expected from known fluxes of O(2), CO(2) and CH(4) on the assumption that carbohydrate is the respiratory substrate. This presupposes that there is a large hydrogen sink (additional to CH(4) production), possibly the emission of H(2) gas, and/or the existence of unresolved digestive mechanisms or electron routings. Uncertainties in the use of manometry with termites are discussed.