THE FOOD AND REPRODUCTIVE CYCLES OF THE CENTIPEDES LITHOBIUS VARIEGATUS AND LITHOBIUS FORFICATUS IN A YORKSHIRE WOODLAND

Lithobius variegatus and L. forficatus occupy similar ecological niches and frequently occur together although there are differences in their distribution in the British Isles. An investigation of their food and reproductive cycles, being a preliminary step towards a further understanding of their ecological relationships, is described.
Lithobiomorph centipedes have hitherto been regarded as wholly carnivorous, but it is shown that these species feed on litter as well as small litter animals, the presence of litter in the guts of these species not being connected with the presence of animal remains. Whereas L. forficatus takes litter throughout the year, L. variegatus does so mainly in the winter.
Both species appear to lay eggs for a considerable part of the year, though there appears to be only a short period of sperm transfer in spring. It is suggested that the long oviposition period may prevent the loss of the entire brood in a dry summer. The succession of epimorph stadia in L. variegatus is described.
L. forficatus was more common than L. variegatus in the drior part of the woods studied.     

The water relations of Lithobius forficatus and the role of the coxal organs (Myriapoda: Chilopoda)

The water relations of the common brown centipede, Lithobius forficatus (L.), are examined with regard to the possible involvement of the coxal organs in water uptake. Centipedes with blocked and open coxal pores are subjected to a variety of dehydration and rehydration regimes and weight change over time measured. Weight loss and regain is related to body surface area and is not influenced by the coxal organs.
The conclusion of the paper is that the coxal organs of L. forficatus do not contribute significantly to the ability of these animals to recover water lost through cuticular transpiration.     

The chemosensory behaviour of Lithobius forficatus. 1. Evidence for a pheromone released by the coxal organs (Myriapoda: Chilopoda)

The behaviour of the Common brown centipede, Lithobius forficatus (.L.) is investigated with reference to the function of the coxal organs which are a peculiar and characteristic feature of Chilopoda. Previous studies of these organs in centipedes have been largely morphological and have relied on ultrastructural comparisons with other arthropod epithelia of disparate functions. Evidence is presented which suggests that the coxal pores release a sex-specific pheromone. The nature of intraspecific interactions in L. forficatus is discussed.     

Chromosome study of Lithobius forficatus (Lithobiomorpha, Chilopoda)

The diploid number 2n = 46 and the chromosome arm number NF = 74 are described in Lithobius forficatus from Olsztyn (Poland). Analyses of silver and CMA3-stained mitotic chromosomes suggest that a single chromosome pair has active NORs which correspond to G-C-rich (CMA3-positive) chromatin. Heteromorphism of the largest metacentric chromosome pair was observed. The sex chromosomes were not identified. Size polymorphism of the first chromosome pair was found.     

The degenerating processes of germinal cells during oogenesis in Lithobius forticatus L. (Myriapoda chilopoda)]

The ovary of Lithobius forficatus always contains some degenerating oocytes. The cytologic evolution during the oocyte degenerescence is described. Cytoplasmic lysis takes place before nuclear lysis and the vitellinic reserves resist the longest. The degenerates coming from previtellogenetic or poorly vitellogenetic cells are essentially recovered by the follicular cells. If large vitellogenetic or mature oocytes are affected, their vitellinic reserves are released into the ovarian cavity and included in the cells of the ovarian epithelium. The number of degenerating oocytes is in relation with the external conditions; it reaches a maximum at the end of the spring. The temperature may act directly or indirectly through the endocrine centers.     

Levels of progesterone, testosterone, and estradiol, and androstenedione metabolism in the gonads of Lytechinus variegatus (Echinodermata:echinoidea)

Levels of progesterone (P4), testosterone (T) and estradiol (E2) indicated significant variation among individual echinoids during the annual cycle, reflecting generally the variation in gamete development that can be observed among individuals. Testosterone and E2 levels in both the ovaries and testes were higher during the period of gonadal growth. Levels of all steroids were greatly reduced compared to those levels reported for asteroids. Differences in the levels of P4, T, and estrogens between asteroids and Lytechinus variegatus may be related to differences in gonad morphology and nutrient storage capacity between asteroids and echinoids. It was hypothesized that the low levels of steroids detected in L. variegatus reflect paracrine-like mechanisms in cell signaling as compared to endocrine-like mechanisms proposed to be involved in regulating gonad function in asteroids. Both the ovaries and testes of L. variegatus had the capacity to synthesize T and a variety of 5alpha-reduced androgens including 5alpha-androstane-3beta,17beta-diol and 5alpha-androstane-3alpha,17beta-diol (5alpha-adiols) from androstenedione (AD) in 8 h. Estrogen synthesis was not detected. The sex-specific pattern of accumulation of 5alpha-adiols in the ovaries and testes suggests that the 5alpha-adiols may affect processes related to reproduction in L. variegatus.     

Structure of the sea urchin U1 RNA repeat.

The genes coding for U1 RNA in the sea urchin L. variegatus are present in a 1400 base pair tandem repeat. One member of the repeat has been cloned and its sequence determined. The repeat unit contains a single copy of the gene for L. variegatus U1 RNA. This gene encodes an RNA which is 75% homologous to mammalian U1 RNA. The L. variegatus U1 RNA could assume a secondary structure similar to that proposed for other U1 RNAs. In addition the L. variegatus U1 RNA is precipitated by anti-SM and anti-RNP antisera. Analysis of the L. variegatus genomic DNA using the cloned U1 gene as a probe reveals a major and a minor type of repeat unit. The two repeated units are the same length but differ in a number of restriction enzyme sites clustered 200-500 bases down-stream from the gene. The monomer we have cloned and sequenced is a representative of the minor repeat. A sequence (GATAA) which is -41 to -37 bases 5' to the gene has homology to the putative RNA polymerase II promoter. Fifteen bases 3' of the gene is a sequence (CAAAGAAAGAAAA) which is very similar to the sequence found 3' of the sea urchin histone genes. The two Hha I, Hpa II and Ava I sites in the repeat are all unmethylated in sperm DNA.     

The effects of organic and inorganic phosphates on fertilization and early development in the sea urchin Lytechinus variegatus (Echinodermata: Echinoidea)

The embryos of the sea urchin Lytechinus variegatus are capable of surviving chronic exposure to inorganic sodium phosphate and organic triethyl phosphate concentrations as high as 6 and 1000 mg l(-1) seawater, respectively. However, chronic exposure to sub-lethal concentrations of these phosphates may cause arrested or abnormal embryonic development. We measured fertilization success and percentages of normal, arrested and abnormal embryos exposed to low, medium and high sub-lethal concentrations of inorganic and organic phosphate. Fertilization success was significantly reduced in all phosphate treatments. After attaining the 4-cell stage, embryos exposed to the highest phosphate concentrations displayed arrested development. Percentages of abnormally developing embryos showed a strong concentration dose-response with a significant increase in abnormal embryonic development with increasing phosphate concentration. Overall, these results indicate that the gametes and embryos of L. variegatus may provide a rapid and sensitive model bioassay for the evaluation of phosphate pollutants in marine systems. Our findings also indicate that shallow-water populations of L. variegatus spawning in areas subjected to inorganic and organic phosphate pollutants may suffer detrimental effects on fertilization and embryonic development.     

Lack of age-associated telomere shortening in long- and short-lived species of sea urchins

The red sea urchin, Strongylocentrotus franciscanus, can live in excess of 100 years while the sea urchin Lytechinus variegatus has an estimated lifespan of only 3-4 years. In an effort to understand the molecular mechanism underlying the difference in their longevity we characterized telomere biology in these species of sea urchins. Telomerase activity was found throughout early stages of development in L. variegatus and is maintained in adult tissues of L. variegatus and S. franciscanus. Terminal restriction fragment analysis indicated a lack of age-associated telomere shortening. These data suggest that long- and short-lived sea urchins do not utilize telomerase repression as a mechanism to suppress neoplastic transformation.     

Function of a sea urchin egg Src family kinase in initiating Ca2+ release at fertilization

Egg activation at fertilization requires the release of Ca(2+) from the egg's endoplasmic reticulum, and recent evidence has indicated that a Src family kinase (SFK) may function in initiating this signaling pathway in echinoderm eggs. Here, we identify and characterize a SFK from the sea urchin Strongylocentrotus purpuratus, SpSFK1. SpSFK1 RNA is present in eggs, and an antibody made against a SpSFK1 peptide recognizes an approximately 58-kDa egg membrane-associated protein in eggs of S. purpuratus as well as another sea urchin Lytechinus variegatus. Injection of both species of sea urchin eggs with dominant-interfering Src homology 2 domains of SpSFK1 delays and reduces the release of Ca(2+) at fertilization. Injection of an antibody against SpSFK1 into S. purpuratus eggs also causes a small increase in the delay between sperm-egg fusion and Ca(2+) release. In contrast, when injected into eggs of L. variegatus, this same antibody has a dramatic stimulatory effect: it causes PLCgamma-dependent Ca(2+) release like that occurring at fertilization. Correspondingly, in lysates of L. variegatus eggs, but not S. purpuratus eggs, the antibody stimulates SFK activity. Injection of L. variegatus eggs with another antibody that recognizes the L. variegatus egg SFK also causes PLCgamma-dependent Ca(2+) release like that at fertilization. These results indicate that activation of a Src family kinase present in sea urchin eggs is necessary to cause Ca(2+) release at fertilization and is capable of stimulating Ca(2+) release in the unfertilized egg via PLCgamma, as at fertilization.     

Isolation and characterization of developmentally regulated sea urchin U2 snRNA genes

Genes encoding the U2 snRNA have been isolated from the sea urchins, Strongylocentrotus purpuratus and Lytechinus variegatus. Representatives of tandemly repeated gene sets have been isolated from both sea urchin species and a unique U2 gene has also been isolated from L. variegatus. The sequence of the U2 snRNA encoded by the tandemly repeated genes differs in two nucleotides between S. purpuratus and L. variegatus. The unique U2 gene from L. variegatus encodes the same U2 RNA as the tandemly repeated genes. There is a change in the U2 genes expressed between morula and pluteus embryos as judged by a change in the U2 RNA sequence in S. purpuratus embryos. The tandemly repeated genes were expressed at a higher rate in blastula than in gastrula stage relative to the single-copy gene, when the two genes were injected into sea urchin zygotes.     

Aspects of reproduction in ruffed lemurs (Lemur variegatus).

Results of breeding of ruffed lemurs (Lemur variegatus) at the Duke Primate Facility provide information concerning estrous cycle, sexual behavior, age of first conception, gestation period, parturition, litter size. L. variegatus differs from other Lemur species in these respects.     

Speciation on the coasts of the new world: phylogeography and the evolution of bindin in the sea urchin genus Lytechinus

Abstract Beginning with E. Mayr's study in 1954, tropical sea urchins have played an important role in studies of speciation in the sea, but what are the processes of cladogenesis and divergence that give rise to new species in this group? We attempt to answer this question in the genus Lytechinus. Unlike the majority of other tropical sea urchin genera, which have circumtropical distributions, Lytechinus is mostly confined to the tropics and subtropics of the New World. We sequenced a region of mitochondrial cytochrome oxidase I and the entire molecule of nuclear bindin (a sperm gamete recognition protein) of nearly all species in the genus, and we assayed isozymes of three partially sympatric closely related species and subspecies. We found that in both mitochondrial DNA (mtDNA) and in bindin the genus Lytechinus is paraphyletic, encompassing Sphaerechinus granularis as the sister species of L. euerces. The rest of the species are arranged in an Atlantic clade composed of L. williamsi and L. variegatus, and a Pacific clade containing L. anamesus, L. pictus, L. semituberculatus, and L. panamensis. Divergence between these clades suggests that they were separated no later than the closure of the Isthmus of Panama, and possibly before this time. Our data confirm that L. anamesus and L. pictus from California are a single species, and provide no evidence of differentiation between L. variegatus variegatus from the Caribbean and L. variegatus atlanticus from Bermuda. Lytechinus variegatus variegatus mtDNA is distinct from that of L. variegatus carolinus from the North American seaboard and the Gulf of Mexico, whereas their bindins are very similar. However, there is clear evidence of introgression of mtDNA between the two subspecies and they share alleles in all sampled isozyme loci. Lytechinus williamsi from the Caribbean shares mtDNA haplotypes with L. variegatus variegatus, and they also share isozymes in all assayed loci. Their bindin, however, is distinct and coalesces within each morphospecies. A private clade of mtDNA in L. williamsi may be indicative of former differentiation in the process of being swamped by introgression, or of recent speciation. Recent sudden expansions in effective population size may explain the predominance of a few mitochondrial haplotypes common to the two species. Despite the high divergence of bindin (relative to differentiation of mtDNA) between L. variegatus and L. williamsi, comparison of amino acid replacement to silent substitutions by various methods uncovered no evidence for positive selection on the bindin of any clade of Lytechinus. With the possible exception of L. williamsi and L. variegatus, our results are consistent with a history of allopatric speciation in Lytechinus. The molecular results from Lytechinus, along with those of other similar studies of sea urchins, suggest that the general speciation patterns deduced in the middle of last century by Mayr from morphology and geography have held up, but also have uncovered peculiarities in the evolution of each genus.     

Responses of juvenile terrestrial salamanders to introduced (Lithobius forficatus) and native centipedes (Scolopocryptops sexspinosus)

When introduced species invade ecosystems, alterations in community structure can emerge from the competitive and predatory interactions that occur between introduced and native guild members. Because a number of recent studies have shown that large predatory invertebrates can both compete with and prey on small vertebrates and because introductions of non-native species may play a role in amphibian declines, the effects of introduced centipedes Lithobius forficatus and native centipedes Scolopocryptops sexspinosus on juveniles of the red-backed salamander Plethodon cinereus were examined. In laboratory arenas, juvenile salamanders exhibited submissive behaviour in response to the odours of both species of centipede. There were no significant differences in salamander response to the two centipede odour treatments, but compared to controls, juveniles of P. cinereus spent significantly more time in escape and in a flattened submissive posture when presented with native centipede odours. Despite significant size differences between centipedes and juvenile salamanders, no predation of salamanders by either species of centipede occurred in any pairings. Juveniles exhibited more chemosensory behaviour towards native centipedes and towards their odours and exhibited marked reductions in aggressive posturing when centipedes were present. Field and laboratory data suggest that juveniles of P. cinereus and centipedes were negatively associated. In laboratory trials, the native centipede excluded juvenile salamanders from cover objects and we found fewer instances of co-occurrence in the field than expected. These studies are the first to examine the behavioural interactions between juveniles of P. cinereus and invertebrate predators, one introduced and one native, of eastern deciduous forest-floor food webs.     

Comparison of the bindin proteins of Strongylocentrotus franciscanus, S. purpuratus, and Lytechinus variegatus: sequences involved in the species specificity of fertilization.

Bindin is the sea urchin sperm acrosomal protein that is responsible for the species-specific adhesion of the sperm to the egg. Two new bindin cDNA sequences that contain the entire open reading frame for the binding precursor are reported: one for Strongylocentrotus franciscanus and one for Lytechinus variegatus. Both contain inverted repetitive sequences in their 3' untranslated regions, and the S. franciscanus cDNA contains an inverted repetitive sequence match between the 5' untranslated region and the coding region. The middle third of the mature bindin sequence is highly conserved in all three species, and the flanking sequences share short repeated sequences that vary in number between the species. Cross-fertilization data are reported for the species S. purpuratus, S. franciscanus, L. variegatus, and L. pictus. A barrier to cross-fertilization exists between the sympatric Strongylocentrotus species, but there is no barrier between the allopatric Lytechinus species.     

Induced inflammatory process in the sea urchin Lytechinus variegatus

Abstract. In vitro and in vivo studies confirmed endocytic activity of free phagocytic amebocytes in Lytechinus variegatus . Amebocytes in the perivisceral coelom were labeled with injected ferritin, and ferritin-labeled amebocytes were found in the peristomial connective tissue only one hour after injection of India ink or yeast into this tissue. The presence of ferritin inside the amebocytes indicates that these cells migrated from the perivisceral coelom to the peristomial connective tissue. After 24 hours, particles of India ink or yeast were observed inside the ferritin-labeled amebocytes, indicating the amebocytes' ability to respond to an inflammatory stimulus. These were the only inflammatory cells found in L. variegatus , using the above mentioned stimuli and time spans.     

Acetylcholinesterase in the sea urchin Lytechinus variegatus: characterization and developmental expression in larvae

Acetylcholinesterase (AChE) in the echinoid Lytechinus variegatus has been characterized. Kinetic parameters V(max), K(m), K(ss), and b were 2594+/-1048 nmol ATCh hydrolyzed/min/mg tissue wet weight, 185+/-11 microM, 308+/-100 mM, and 0.2, respectively for the substrate ATCh and 17.8+/-6.87 nmol BTCh hydrolyzed/min/mg tissue wet weight, 654+/-424 microM, 36+/-31 mM, and 0.6, respectively for BTCh. Pharmacologic analyses were performed with four inhibitors of cholinesterases, physostigmine, BW284c51, ethopropazine, and iso-OMPA, and yielded IC(50) values of 106+/-4 nM, 718+/-118 nM, 2.57+/-0.6 mM, and >0.0300 M, respectively. Both kinetic and pharmacologic results confirmed the existence of AChE in larval L. variegatus. Dimeric and tetrameric globular forms (determined by velocity sedimentation on sucrose gradients) were present in L. variegatus larvae. Activity of AChE increased significantly as larvae progressed in development from embryos to eight-arm larvae. Acetylcholinesterase activity of F1 larvae derived from sea urchins collected from wild populations and of F1 larvae derived from sea urchins cultured in the laboratory and fed two different diets suggest that the nutritional and/or environmental history of the adult sea urchin affect the developmental progression of AChE activity in the F1 offspring.