Multiple genes and the monophyly of Ischnocera (Insecta: Phthiraptera).

Whereas most traditional classifications identify Ischnocera as a major suborder of lice in the order Phthiraptera, a recent molecular study based on one gene did not recover monophyly of Ischnocera. In this study we test the monophyly of Ischnocera using sequences of portions of three different genes: two nuclear (EF1 alpha and 18S) and one mitochondrial (COI). Analysis of EF1 alpha and COI sequences did not recover monophyly of Ischnocera, but these genes provided little support for ischnoceran paraphyly because homoplasy is high among the divergent taxa included in this study. Analysis of 18S sequences recovered ischnoceran monophyly with strong support. Sequences from these three gene regions showed significant conflict with the partition homogeneity test, but this heterogeneity probably arises from the dramatic differences in substitution rates. In support of this conclusion, Kishino-Hasegawa tests of the EF1 alpha and COI genes did not reject several trees containing ischnoceran monophyly. Combined analysis of all three gene regions supported monophyly of Ischnocera, although not as strongly as analysis of 18S by itself. In sum, although rapidly evolving genes can retain some phylogenetic signal for deep phylogenetic relationships, strong support for such relationships is likely to come from more slowly evolving genes.     

Oogenesis in Xenopus laevis (Daudin). I. Stages of oocyte development in laboratory maintained animals

Oogenesis in the anuran Xenopus laevis can be divided into six stages based on the anatomy of the developing oocyte. Stage I consists of small (50 to 100 μ) colorless oocytes whose cytoplasm is transparent. Their large nuclei and mitochondrial masses are clearly visible in the intact oocyte. Stage II oocytes range up to 450 μ in diameter, and appear white and opaque. Stage I and II are both previtellogenic. Pigment synthesis and yolk accumulation (vitellogenesis) begins during Stage III. Vitellogenesis continues through Stage IV (600 to 1000 μ), the oocytes grow rapidly, and the animal and vegetal hemispheres become differentiated. By Stage V (1000 to 1200 μ) the oocytes have nearly reached their maximum size and yolk accumulation gradually ceases. Stage VI oocytes are characterized by the appearance of an essentially unpigmented equatorial band. They range in size from 1200 to 1300 μ, are postivtellogenic and ready for ovulation. These stages of oocyte development have been correlated with physiological and biochemical data related to oogenesis in Xenopus.     

Morphological variation of chewing lice (Insecta: Phthiraptera) from different skua taxa

The lice, Haffneria grandis and Saemundssonia were extracted from their hosts, skuas (Aves: Stercorariidae). Lice were extracted from dead birds by combing feathers, while lice from live birds were extracted using a delousing chamber containing chloroform vapour. Lice were measured and the data analysed by canonical discriminant analysis. Lice show variation in morphology that is useful in identifying some of these hosts. This variation is presumably due to micro-environmental pressure provided by each host. Our interpretation is that these chewing lice have evolved to be adapted to each skua taxon; different sizes and morphologies of skua taxa result in different sizes and morphologies of Haffneria grandis and Saemundssonia.     

Critical evaluation of five methods for quantifying chewing lice (Insecta: Phthiraptera).

Five methods for estimating the abundance of chewing lice (Insecta: Phthiraptera) were tested. To evaluate the methods, feral pigeons (Columba livia) and 2 species of ischnoceran lice were used. The fraction of lice removed by each method was compared, and least squares linear regression was used to determine how well each method predicted total abundance. Total abundance was assessed in most cases using KOH dissolution. The 2 methods involving dead birds (body washing and post-mortem-ruffling) provided better results than 3 methods involving live birds (dust-ruffling, fumigation chambers, and visual examination). Body washing removed the largest fraction of lice (>82%) and was an extremely accurate predictor of total abundance (r2 = 0.99). Post-mortem-ruffling was also an accurate predictor of total abundance (r2 > or = 0.88), even though it removed a smaller proportion of lice (<70%) than body washing. Dust-ruffling and fumigation chambers removed even fewer lice, but were still reasonably accurate predictors of total abundance, except in the case of data sets restricted to birds with relatively few lice. Visual examination, the only method not requiring that lice be removed from the host, was an accurate predictor of louse abundance, except in the case of wing lice on lightly parasitized birds.     

Oogenesis in Fundulus heteroclitus: I. Preliminary observations on oocyte maturation in vivo and in vitro

During the breeding season, the ovary of Fundulus heteroclitus contains follicles of all sizes up to around 1.8 mm in diameter and continuously ovulates eggs (1.7 mm) into the ovarian lumen. Vitellogenic follicles appear to extend up to 1.3 mm, while those larger than 1.4 mm are undergoing hydration concomitant with maturation. If feeding ceases, vitellogenesis appears to stop and maturational stages flush out of the ovary. Refeeding causes reappearance of maturational stages. A culture procedure was developed for dissected F. heteroclitus follicles and a size range (1.3–1.4 mm) was defined which responded to added hormones by undergoing the same maturational changes (germinal vesicle breakdown, fusion, and peripheral detachment of oil droplets, appearance of activability) as occurs in vivo, although the extent of hydration was not quite as extensive. Ovulation, however, did not consistently occur in vitro. Both 11-deoxycorticosterone and progesterone are potent inducers of maturation in vitro, with median effective doses being 10–20 ng/ml. Hydrocortisone is about one-tenth as active. Human chorionic gonadotropin promotes maturational changes in about 25% of the follicles over a broad concentration range (1–100 IU/ml). The environmental and hormonal mechanisms which influence oocyte maturation in teleosts are discussed in relation to our findings for F. heteroclitus.     

Ultrastructural Studies on Gametogenesis of the Prawn Palaemon serratus (Pennant). I. Oogenesis

The oogenesis of the common prawn P. serratus is described. The reproductive cycle is annual and there is little evidence for a second spawning period. Oogenesis under the electron microscope follows a typical crustacean pattern and has been divided into seven stages according to the structure of the oocytes. The production of yolk is mainly intra-oocytic, with a small extra-oocytic contribution. Yolk, in the form of small granules, arises within the lamellar elements of the rough endoplasmic reticulum. These were then transformed into finely granular yolk bodies. Lipid droplets, as in other crustacean species, arise de novo in the cytoplasm and there is no association between lipids and cell organelles.     

Reduced taxonomic richness of lice (Insecta: Phthiraptera) in diving birds

Avian lice occupy different habitats in the host plumage that the physical environment outside the host body may affect in several ways. Interactions between host plumage and water may be an important source of such effects. Here, we use a comparative approach to examine the effect of a host's diving behavior on the taxonomic richness of its lice. Louse genera richness was significantly lower in clades of diving birds than on their nondiving sister clades. Species richness of host and body mass did not differ significantly between these clades; thus, these factors did not bias our results. This study suggests that the hosts' diving behavior can effectively influence ectoparasite communities.     

Dramatically elevated rate of mitochondrial substitution in lice (Insecta: Phthiraptera)

Few estimates of relative substitution rates, and the underlying mutation rates, exist between mitochondrial and nuclear genes in insects. Previous estimates for insects indicate a 2-9 times faster substitution rate in mitochondrial genes relative to nuclear genes. Here we use novel methods for estimating relative rates of substitution, which incorporate multiple substitutions, and apply these methods to a group of insects (lice, Order: Phthiraptera). First, we use a modification of copath analysis (branch length regression) to construct independent comparisons of rates, consisting of each branch in a phylogenetic tree. The branch length comparisons use maximum likelihood models to correct for multiple substitution. In addition, we estimate codon-specific rates under maximum likelihood for the different genes and compare these values. Estimates of the relative synonymous substitution rates between a mitochondrial (COI) and nuclear (EF-1alpha) gene in lice indicate a relative rate of several 100 to 1. This rapid relative mitochondrial rate (>100 times) is at least an order of magnitude faster than previous estimates for any group of organisms. Comparisons using the same methods for another group of insects (aphids) reveals that this extreme relative rate estimate is not simply attributable to the methods we used, because estimates from aphids are substantially lower. Taxon sampling affects the relative rate estimate, with comparisons involving more closely related taxa resulting in a higher estimate. Relative rate estimates also increase with model complexity, indicating that methods accounting for more multiple substitution estimate higher relative rates.     

Remarkable levels of avian louse (Insecta: Phthiraptera) diversity in the Congo Basin

Although the Democratic Republic of the Congo is considered a megadiverse country, the Congo Basin is not recognized as a conservation priority because of gross underestimates of species diversity and endemism, especially for invertebrate taxa. Examining ectoparasitic chewing lice parasitizing birds in this region could provide valuable information pertaining to the diversity of invertebrate taxa as well as host–parasite interactions within the Congo Basin. In this study, we used molecular and morphological data to examine avian louse diversity. From 60 parasitized birds, we documented 39 new host associations, and at least 12 and 17 species of amblyceran and ischnoceran chewing lice, respectively. Morphologically, we identified a minimum of 13 new species. Due to a lack of available reference material, we were unable to identify some specimens and it is likely many, if not all of these, represent new species. Our sampling efforts, morphological examinations and molecular analyses reveal an astounding amount of louse diversity in the Congo Basin.     

Chewing Lice (Insecta: Phthiraptera) from Migratory Birds of the Curonian Spit

The fauna of chewing lice (Insecta: Phthiraptera) from migratory birds was studied in 2008–2009 and 2017 on the Curonian Spit, at Rybachy Biological Station of the Zoological Institute, Russian Academy of Sciences. Altogether, 35 species of chewing lice were collected off 2010 birds of 65 species. An annotated list of species is presented, including 11 species new to the Russian Federation, 29 species new to the Northwest of Russia, and 2 new host records: Menacanthus eurysternus from Carduellis carduellis and Ricinus frenatusfromCarduellis spinus.     

Oogenesis in the terrestrial hermit crab Coenobita clypeatus (decapoda,anomura). I. Previtellogenic oocytes

Ultrastructural study of previtellogenic oocytes found in cystlike clusters scattered throughout the length of the bilobed ovary of the hermit crab Coenobita clypeatus shows a high nuclear:cytoplasm ratio. Large, round nuclei containing synaptinemal complexes serve as good temporal markers for identification of previtellogenic oocytes. The cytoplasm contains many smooth-membraned vesicles filled with granules and probably of nuclear origin. In addition to its complement of Golgi complexes, endoplasmic reticulum, mitochondria, and free ribosomes, the cytoplasm also contains stacks of annulate lamellae, a feature not previously described for decapod oocytes. Typically, the previtellogenic oocyte with its accumulation of ribosomes has the appearance of a nonsynthetic cell preparing to go through a metabolic transition.     

Morphological and histochemical observations on the intestinal epithelium of Ascardia galli (Nematoda: Ascaridida).

The intestinal epithelium of Ascardia galli has been studied with various cytological and cytochemical techniques. It consists of large epithelial cells resting on a thick collagenous basal lamina. Their luminal surface is provided with microvilli. The intestinal cells store considerable amounts of glycogen and neutral lipids. Some intracellular granular inclusions, which stain for proteins, phospholipids and lipoproteins, are distributed throughout the cytoplasm. The brush border is composed of microvilli whereas the outer surface coat consists of saliva resistant PAS-positive material. The detailed histochemical analysis of surface material has revealed that it is composed of nonacetylated acid mucopolysaccharides rich in hyaluronic acid with carboxylate polyanions. The brush border shows intense activities of acid phosphatase and glucose-6-phosphatase, moderate of ATPase, and lipase, weak of 5'-nucleotidase. Acid phosphatase-positive intracellular structures are seen in the intestinal epithelium which form distinct aggregations.     

Oogenesis in Campodea sp. (Insecta,Diplura): Chorion formation and the ultrastructure of follicle cells

During advanced vitellogenesis the follicle cells of Campodea sp. are well developed and contain numerous electron-dense secretory vacuoles. In the postvitellogenic phase the contents of these vacuoles are released from follicle cells and give rise to a thin chorion on the oocyte surface. Concurrently, segregation of yolk spheres takes place in the ooplasm: small spheres migrate to the oocyte periphery and come to lie in the so-called peripheral zone of cytoplasm, whereas large spheres remain in the cell centre.     

Transmission ratio distortion in the human body louse, Pediculus humanus (Insecta: Phthiraptera)

We studied inheritance at three microsatellite loci in eight F, and two F2 families of the body (clothes) louse of humans, Pediculus humanus. The alleles of heterozygous female-parents were always inherited in a Mendelian fashion in these families. Alleles from heterozygous male-parents, however, were inherited in two different ways: (i) in a Mendelian fashion and (ii) in a non-Mendelian fashion, where males passed to their offspring only one of their two alleles, that is, 100% nonrandom transmission. In male body lice, where there was non-Mendelian inheritance, the paternally inherited set of alleles was eliminated. We interpret this pattern of inheritance as evidence for extreme transmission ratio distortion of paternal alleles in this species.     

The population genetics of host specificity: genetic differentiation in dove lice (Insecta: Phthiraptera)

Some species of parasites occur on a wide range of hosts while others are restricted to one or a few host species. The host specificity of a parasite species is determined, in part, by its ability to disperse between host species. Dispersal limitations can be studied by exploring the genetic structure of parasite populations both within a single species of host and across multiple host species. In this study we examined the genetic structure in the mitochondrial cytochrome oxidase I (COI) gene of two genera of lice (Insecta: Phthiraptera) occurring on multiple sympatric species of doves in southern North and Central America. One genus, Columbicola, is generally less host-specific than the other, Physconelloides. For both genera we identified substantial genetic differentiation between populations of conspecific lice on different host species, generally 10-20% sequence divergence. This level of divergence is in the range of that often observed between species of these two genera. We used nested clade analysis to explore fine scale genetic structure within species of these feather lice. We found that species of Physconelloides exhibited more genetic structure, both among hosts and among geographical localities, than did species of Columbicola. In many cases, single haplotypes within species of Columbicola are distributed on multiple host species. Thus, the population genetic structure of species of Physconelloides reveals evidence of geographical differentiation on top of high host species specificity. Underlying differences in dispersal biology probably explain the differences in population genetic structure that we observed between Columbicola and Physconelloides.     

Phylogeny of the lice (Insecta, Phthiraptera) inferred from small subunit rRNA

There has been much argument about the phylogenetic relationships of the four suborders of lice (Insecta: Phthiraptera). Lyal's study of the morphology of lice indicated that chewing/biting lice (Mallophaga) are paraphyletic with respect to sucking lice (Anoplura). To test this hypothesis we inferred the phylogeny of 33 species of lice from small subunit (SSU) rRNA sequences (18S rRNA). Liposcelis sp. from the Liposcelididae (Psocoptera) was used for outgroup reference. Phylogenetic relationships among the four suborders of lice inferred from these sequences were the same as those inferred from morphology. The Amblycera is apparently the sister-group to all other lice whereas the Rhynchophthirina is apparently sister to the Anoplura; these two suborders are sister to the Ischnocera, i.e. (Amblycera (Ischnocera (Anoplura, Rhynchophthirina))). Thus, the Mallophaga (Amblycera, Ischnocera, Rhynchophthirina) is apparently paraphyletic with respect to the Anoplura. Our analyses also provide evidence that: (i) each of the three suborders of lice that are well represented in our study (the Amblycera, Ischnocera, and Anoplura) are monophyletic; (ii) the Boopiidae is monophyletic; (iii) the genera Heterodoxus and Latumcephalum (Boopiidae) are more closely related to one another than either is to the genus Boopia (also Boopiidae); (iv) the Ricinidae and Laemobothridae may be sister-taxa; (v) the Philopteridae may be paraphyletic with respect to the Trichodectidae; (vi) the genera Pediculus and Pthirus are more closely related to each other than either is to the genus Pedicinus ; and (vii) in contrast to published data for mitochondrial genes, the rates of nucleotide substitution in the SSU rRNA of lice are not higher than those of other insects, nor do substitution rates in the suborders differ substantially from one another.     

Morphological and histochemical characterization of the pectoral fin muscle of batoids

Batoids differ from other elasmobranch fishes in that they possess dorsoventrally flattened bodies with enlarged muscled pectoral fins. Most batoids also swim using either of two modes of locomotion: undulation or oscillation of the pectoral fins. In other elasmobranchs (e.g., sharks), the main locomotory muscle is located in the axial myotome; in contrast, the main locomotory muscle in batoids is found in the enlarged pectoral fins. The pectoral fin muscles of sharks have a simple structure, confined to the base of the fin; however, little to no data are available on the more complex musculature within the pectoral fins of batoids. Understanding the types of fibers and their arrangement within the pectoral fins may elucidate how batoid fishes are able to utilize such unique swimming modes. In the present study, histochemical methods including succinate dehydrogenase (SDH) and immunofluoresence were used to determine the different fiber types comprising these muscles in three batoid species: Atlantic stingray (Dasyatis sabina), ocellate river stingray (Potamotrygon motoro) and cownose ray (Rhinoptera bonasus). All three species had muscles comprised of two muscle fiber types (slow-red and fast-white). The undulatory species, D. sabina and P. motoro, had a larger proportion of fast-white muscle fibers compared to the oscillatory species, R. bonasus. The muscle fiber sizes were similar between each species, though generally smaller compared to the axial musculature in other elasmobranch fishes. These results suggest that batoid locomotion can be distinguished using muscle fiber type proportions. Undulatory species are more benthic with fast-white fibers allowing them to contract their muscles quickly, as a possible means of escape from potential predators. Oscillatory species are pelagic and are known to migrate long distances with muscles using slow-red fibers to aid in sustained swimming.