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Cryptonephric malpighian tubule system in a dipteran larva, the New Zealand glow-worm, Arachnocampa luminosa (Diptera: Mycetophilidae): a structural study.

The Malpighian tubules of the glow-worm are divided into four morphologically distinct regions, each composed of a different cell type. Part 3 of the Malpighian tubules of A. luminosa is intimately bound to the rectum by a layer of fat body. This association of the tubules with the hindgut is referred to as a cryptonephric system. This type of arrangement has been described in some Coleoptera and the larvae of most Lepidoptera but has never before been reported in the Diptera. In the glow-worm the cryptonephric tubules themselves are small, and adjacent to the fat body the epithelial cells are modified to form very thin windows or 'leptophragmata' (Lison, 1937). The main epithelial cells exhibit features characteristic of highly active, secretory Malpighian tubule cells. The high density of mitochondria and their association with all the microvilli is indicative of a highly active secretory cell. The high concentration of glycogen in these cells and their intimate association with the hindgut suggest that they may, in addition, have a nutrient absorptive function. The role of the cryptonephric rectal complex in the glow-worm is discussed in the light of present knowledge gained from previous studies of coleopteran and larval lepidopteran cryptonephric systems. On structural grounds a model is proposed for the regulation of the ionic environment of the rectum, and the uptake and metabolism of organic material from the rectal lumen by this cryptonephric complex.

Animals↗

Colour vision in the glow-worm Lampyris noctiluca (L.) (Coleoptera: Lampyridae): evidence for a green-blue chromatic mechanism.

Male glow-worms Lampyris noctiluca find their bioluminescent mates at night by phototaxis. There is good evidence that location of mates by lampyrid beetles is achieved by a single spectral class of photoreceptor, whose spectral sensitivity is tuned to the bioluminescent spectrum emitted by conspecifics, and is achromatic. We ask whether glow-worm phototaxis involves interactions between two spectral classes of photoreceptor. Binary choice experiments were conducted in which males were presented with artificial light stimuli that differ in spectral composition. The normal preference for a green stimulus (lambdamax=555 nm), corresponding to the bioluminescence wavelength produced by signalling females, was significantly reduced by adding a blue (lambdamax=485 nm) component to the signal. This implies an antagonistic interaction between long- and short-wavelength sensitive photoreceptors, suggesting colour vision based on chromatic opponency. Cryosections showed a band of yellow filter pigment in the fronto-dorsal region of the male compound eye, which could severely constrain colour vision in the dim conditions in which the insects signal. This apparent paradox is discussed in the context of the distribution of the pigment within the eye and the photic niche of the species.

Animals↗

Regional specialization in the Malpighian tubules of the New Zealand glow-worm Arachnocampa luminosa (Diptera: mycetophilidae). The structure and function of type I and II cells.

The Malpighian tubules of the glow-worm Arachnocampa luminosa are divided into four morphologically distinct regions (Parts 1--4) each comprised of a different cell type (Types I--IV). The ultrastructure of Type II cells is indicative of a transport function. The basal cell surface is highly invaginated and at the apical surface the lumen is lined with microvilli about 80% of which contain mitochondria. Spherites contained in these cells are formed from small vesicles produced by the Golgi apparatus. They have a central uric acid core enclosed by laminations of phosphates of calcium and magnesium. Cells of Part 2 of the tubule secrete a fluid high in potassium (173 mM) and low in sodium (18 mM). The cell is 30 mV negative and the lumen 44 mV positive to the bathing solution. This is consistent with the proposal of an apical cation pump. The secretion produced by Part 2 of the tubules is modified by the Type I cells by the reabsorption of potassium (162 mM) and the addition of sodium (24 mM) to the primary excretory fluid. Type I cells are 20 mV negative and the lumen 22 mV positive with respect to the bathing medium. From ultrastructural observations, Type I cells exhibit features characteristic of transporting cells thought to have an absorptive function. The basal and apical cell surfaces are extensively folded, and mitochondria are found in bands above the basal infoldings and below the microvilli. Mitochondria do not penetrate the microvilli. On comparative grounds, the fine structure of Type I cells suggest that they reabsorb ions from the tubule lumen. Energy for these processes may come from the breakdown of lipids by microperoxisomes contained within these cells. Alternatively, the fluid produced by Part 2 of the tubule may be modified passively by diffusional processes across Type I cells.

Animals↗

The structure and function of the smooth septate junction in a transporting epithelium: the Malpighian tubules of the New Zealand glow-worm Arachnocampa luminosa.

Junctional complexes between the epithelial cells in the four distinct regions of the glow-worm Malpighian tubule were investigated by electron microscopy using thin sectioning, freeze-fracturing, osmotic disruption and tracer techniques. The lateral plasma membranes of all four cell types are joined by smooth septate junctions but the extent of the complex across the cell depth varies in the four different regions. The width of the septa, the interseptal spacing and the separation between the outer leaflets of the adjacent plasma membranes are different for each cell type. Gap junctions were identified only in the junctional complex between Type IV cells and were intercalated amongst large lateral sinuses. In oblique sections of lanthanum infiltrated tissue, the electron-lucent septa at the basal side of the junction are outlined by the tracer as it penetrates. In the junctional complexes of all four regions the septa appear as short, distinct, linear bars. In tangential sections of gap junctions between Type IV cells, the junctions appear as a hexagonal array of intermembrane particles with a centre to centre spacing of 18 nm. Horseradish peroxidase did not penetrate the junctional complexes very far but readily passed through the basal lamina into the spaces between extracellular invaginations of the basement membrane of the cells. Junctional complexes in all four areas of the tubule have similar freeze-fracture faces. In freeze-fracture replicas of fixed tissue continuous ridges of fused particles are seen on the P face and complementary furrows are found on the E face. Junctional response to osmotically adjusted Ringer solutions was similar in all four cell types. Distortion or 'blistering' of the intercellular space between between the septa of the unction occurred when the tissue was bathed in or injected with a hypertonic Ringer solution. The structure of these junctions, visualized by the different techniques, and the role of the septate junction in a transporting epithelium, are discussed.

Animals↗

Molecular cloning, sequence analysis, and expression of a cDNA encoding the luciferase from the glow-worm, Lampyris turkestanicus.

The first cDNA from lampyridae encoding a glow-worm luciferase from lantern mRNA of Lampyris turkestanicus has been cloned, sequenced, the amino acid sequence predicted, and the sequence reported to GenBank. The cDNA was 1644 base pairs in length and coding a 547-residue protein. The deduced amino acid sequence of the luciferase gene of L. turkestanicus showed 98.7% and 95.8% identity to Lampyris noctiluca and Pyrocoelia rufa, respectively. Phylogenetic analysis further confirmed that the deduced amino acid sequences of L. turkestanicus luciferase gene belong to the same subfamily, Lampyrinae. The cDNA encoding the luciferase of L. turkestanicus was expressed as a 62kDa band in recombinant Escherichia coli and showed green luminescence in the presence of luciferin. Amongst amino acid differences of L. turkestanicus and L. noctiluca (its clade) there are two important substitutions. Signature amino-acid sequences and motifs found in the deduced sequence are CK2-phospho site, ASN-glycosylation, myristoylation site, PKC-phospho site, microbodies C-terminal targeting signal, and AMP-binding domain.

Amino Acid Sequence↗

Sequence and biochemical similarities between the luciferases of the glow-worm Lampyris noctiluca and the firefly Photinus pyralis.

A full-length clone encoding Lampyris noctiluca (British glow-worm) luciferase was isolated from a complementary DNA (cDNA) expression library constructed with MRNA extracted from light organs. The luciferase was a 547-residue protein, as deduced from the nucleotide sequence. The protein was closely related to those of other lampyrid beetles, the similarity to Photinus pyralis luciferase being 84% and to Luciola 67%. In contrast, Lampyris luciferase had less sequence similarity to the luciferases of the click beetle Pyrophorus, at 48%. Engineering Lampyris luciferase in vitro showed that the C-terminal peptide containing 12 amino acids in Photinus and 9 amino acids in Lampyris was essential for bioluminescence. The pH optimum and the Km values for ATP and luciferin were similar for both Photinus and Lampyris luciferases, although the light emitted by the latter shifted towards the blue and was less stable at 37 degrees C. It was concluded that the molecular and biochemical properties were not sufficient to explain the glowing or flashing of the two beetles Lampyris and Photinus.

Adenosine Triphosphate↗

Structure of bacterial luciferase.

The generation of light by living organisms such as fireflies, glow-worms, mushrooms, fish, or bacteria growing on decaying materials has been a subject of fascination throughout the ages, partly because it occurs without the need for high temperatures. The chemistry behind the numerous bioluminescent systems is quite varied, and the enzymes that catalyze the reactions, the luciferases, are a large and evolutionarily diverse group. The structure of the best understood of these intriguing enzymes, bacterial luciferase, has recently been determined, allowing discussion of features of the protein in structural terms for the first time.

Bacteria↗

Sex-biased Migration and Demographic History of the Big European Firefly Lampyris noctiluca.

Differential dispersion between the sexes can impact the colonization process and demographic history of a species. Here, we explored the demographic history of the big European firefly, Lampyris noctiluca, which exhibits female neoteny. Distribution of L. noctiluca extends throughout Europe, but nothing is known about its colonization process. To investigate its demographic history, we produced the first Lampyris genome (653 Mb), including an IsoSeq annotation and the identification of the X chromosome. We collected 115 individuals from six populations of L. noctiluca (Finland to Italy) and generated whole-genome re-sequencing data for each individual. We inferred several population expansions and bottlenecks throughout the Pleistocene that correlate with glaciation events. Surprisingly, we uncovered strong population structure and low gene flow. We reject a stepwise, south to north, colonization history scenario and instead uncovered a complex demographic history with a putative eastern European origin. Analyzing the evolutionary history of the mitochondrial genome as well as X-linked and autosomal loci, we found evidence of a maternal colonialization of Germany, putatively from a farther western European population, followed by a male-only migration from south of the Alps (Italy). Overall, investigating the demographic history and colonization patterns of a species should form part of an integrative approach of biodiversity research. Our results provide evidence of sex-biased migration which is important to consider for demographic, biogeographic and species delimitation studies.

Animals↗