Spermatozoa of the 'primitive type' in Scutigerella (Myriapoda, Symphyla)

The myriapod class Symphyla is of interest in that insects generally are assumed to be derived from symphylan-like ancestors. Male Symphyla form spermatophores that are picked up by the female. Both euspematozoa and paraspermatozoa are formed. In spite of the mode of fertilization their euspermatozoa were found to be of a kind that is typical of aquatic animals, so called 'primitive spermatozoa;' these are characterized by a short sperm head with a bilayered acrosome, a midpiece containing a few unmodified mitochondria, and a 9 + 2 flagellum. Scutigerella are unique among terrestrial arthropods in having 'primitive spermatozoa'; and together with horseshoe crabs they are only the second case in Arthropoda. Two further sperm plesiomorphies not found in other myriapods or insects are (1) the presence of a cytoplasmic canal housing the proximal flagellum and (2) the existence of microtubular triplets in centrioles, one of which acts as a basal body. Symphyla and Diplopoda both have a striated structure in the center of the subacrosomal material. The paraspermatozoa lack acrosome and nucleus but have a prominent crystal, a single mitochondrion, and two membrane systems. The structure of Scutigerella euspermatozoa is consistent with Symphyla being close to the stem group of Myriapoda plus Insecta.     

The complete mitochondrial genome of Scutigerella causeyae (Myriapoda: Symphyla) and the phylogenetic position of Symphyla

The first complete mitochondrial genome of a representative of the Symphyla, Scutigerella causeyae (Arthropoda: Myriapoda), was sequenced using a PCR-based approach. Its gene order shows different positions for three tRNA genes compared to the ancestral arthropod pattern. Presence of a pseudogene with partial sequence similarity to rrnS favours the duplication-random loss model as an explanation for at least one of the translocations. None of the genome rearrangements hypothesized for S. causeyae are shared by any of the other four myriapod mitochondrial genomes sequenced so far (two from Chilopoda and two from Diplopoda). Different rearrangement events must have occurred independently in the lineages leading to S. causeyae, Lithobius forficatus, Scutigera coleoptrata and Diplopoda. Phylogenetic analyses could not unequivocally elucidate the position of Symphyla among myriapods. While the nucleotide dataset of eleven protein-coding genes gives weak support for an affinity to Chilopoda, this is not recovered with the corresponding amino acid dataset.     

Zur Feinstruktur der Maxillarnephridien von Scutigerella immaculata Newport (Symphyla,Myriapoda)

Zusammenfassung Die Feinstruktur der Maxillarnephridien von Scutigerella immaculata Newport mit ihren drei Abschnitten Sacculus, Tubulus und Ausführgang wurde untersucht. Die Zellen des Sacculus sind typische Podocyten, an denen eine Ultrafiltration ablaufen kann. Möglicherweise wird die Filtration durch einen den Sacculus umgebenden Muskel unterstützt. Die Zellen des Tubulus zeigen basale Einfaltungen und im proximalen Teil auch Mikrovilli. Sowohl im Tubulus als auch im Ausführgang, dessen Zellen ebenfalls basale Einfaltungen aufweisen, werden Reabsorptionsprozesse vermutet.

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The fine structure of the maxillary kidney of the garden centipede, Scutigerella immaculata Newport (Symphyla, Myriapoda)

Summary The fine structure of the maxillary kidney of Scutigerella immaculata Newport (Symphyla) has been investigated. It may be compared with segmental organs of other Arthropoda having an end-sac which forms a primary urine by ultrafiltration. The filtration may be supported by a muscle surrounding the end-sac. The tubular part of the nephridium and the efferent duct show structures which may be involved in reabsorption.

     

Chromosome studies in nine species of Austrian Symphyla (Myriapoda,Tracheata, Arthropoda)

The chromosomes of nine species of Austrian Symphyla, namely, Scutigerella causeyae, S. sp., S. sbordonii, S. palmonii, S. carpatica, S. seposita, Hanseniella nivea (fam. Scutigerellidae), Symphylella isabellae and S. vulgaris (fam. Scolopendrellidae) were studied using Giemsa-C-banding and fluorochrome staining techniques. Male diploid chromosome numbers range from 11 to 18. The mechanism of sex determination seems to be variable within this group: S. isabellae (2n=11) might have an XO-type, whereas the other species studied have even diploid chromosome numbers in the male sex. For S. causeyae, specimens with B-chromosomes and an obviously tetraploid form have been detected.     

A Pictorial Key for the Symphylan Families and Genera of the Neotropical Region South of Central Mexico (Myriapoda,Symphyla)

A pictorial key in English and Portugese is given for 2 families and 6 genera of the class Symphyla currently known from the Neotropical region, viz. Central America south of central Mexico, the Caribbean and entire South America.     

Morphological study of the ovary in Hanseniella caldaria (Myriapoda; Symphyla): The position of oocyte-growth and evolution of ovarian structure in Arthropoda

In Arthropoda, the ovary is classified into Chelicerata-type and Mandibulata-type, based on the oocyte-growth position within the ovary. By contrast, oocytes of Diplopoda and Chilopoda grow within the hemocoelic space. However, as the position of oocyte-growth in Symphyla and Pauropoda has not been confirmed, whether the hemocoelic nature of oocyte-growth is common among myriapods remains ambiguous. This study described the ovarian structure of Hanseniella caldaria to reveal the oocyte-growth position in Symphyla. The oocyte is surrounded by the follicle epithelium, and the inner surface of the follicle epithelium, i.e., the space between follicle cells and oocytes, is lined with a basement membrane. The follicle epithelial layer continues to the ovarian epithelium via the follicle extension with a continuous layer of basement membrane. Data on the architecture of the follicle suggest that the follicle pouch opens to the hemocoel. Hence, the oocyte of H. caldaria grows within the hemocoelic space. Based on our findings in H. caldaria and previous studies in a millipede and in centipedes, the hemocoelic nature of oocyte-growth is considered as a common feature among myriapods and a synapomorphy of the Myriapoda for which morphological synapomorphies have been ambiguous.     

Contributions on cardiac physiology in Diplopoda (Myriapoda)

Investigations into cardiac physiology in Myriapoda are rare, but heart beat generation is not considered to be uniform throughout this taxon. Although cardiac automatism in Chilopoda is neurogenic, superimposed onto a myogenic automatism, the present study reveals, on the basis of electrophysiological experiments including electrocardiograms and the first intracellular recordings from dorsal vessel muscle cells of Archispirostreptus gigas Peters, 1855 (Diplopoda: Spirostreptida, Spirostreptidae), that heartbeat generation in Diplopoda is clearly myogenic. Experiments with tetrodotoxin confirm this result, and also show that proctolin, acetylcholine and octopamine have no effect. The results are discussed from the perspective of comparative cardiac physiology in arthropods.     

Antennal sensilla of triatominae (Hemiptera,Reduviidae): A comparative study of five genera

The paper analyses the antennal sensilla pattern of 22 species of triatomine bugs (Hemiptera, Reduviidae). The pedicels of species from tribe Rhodniini differ from species of Cavernicolini and Triatomini, mainly by the absence of trichoid and basiconic sensilla and by a greater number of Bristles I. Fifth-instar nymphs of T. sordida and R. pictipes show several differences in sensilla patterns compared with their respective adults. They lack basiconic sensilla and thin-and thick-walled trichoid sensilla over the first flagellar segment and over the proximal half of the second flagellar segment. T. sordida nymphs also lack these sensilla on the pedicel. There appears to be a significant sexual dimorphism in relation to trichoid sensilla in T. sordida, but not in R. pictipes. There exists a remarkable correlation between the density of basiconic and trichoid sensilla on the pedicels of different species, and a crude estimation of habitat range assessed as number of habitat types reported for each species.     

Coxal organs of Lithobius forficatus (Myriapoda,Chilopoda)

Summary In Lithobius forficatus each of the coxae of the four posterior trunk segments bear a pore field with several coxal pores. The surrounding single-layered epithelium is composed of four different cell types: the main epithelial cells having a fine-structural organization of transport cells with deep apical and basal folds of the cell surfaces and plasmalemma-mitochondrial complexes, junctional cells, exocrine glands, and the wall cells of the pore channel. The entire epithelium is separated from the hemolymph by an inner cellular sheath. It is assumed that the coxal organs participate in fluid uptake.     

The production of five genera of Chironomidae (Diptera) in Lake Norman,a North Carolina reservoir

The production of five genera of chironomids collected at 4- and 8-m depths at four stations in Lake Norman, North Carolina, was estimated using the size-frequency method. To correct for multivoltinism, the estimates were adjusted by multiplying by 365/Cohort Production Interval. Ranges of production estimates (P) in milligrams dry mass m^-2 yr^-1 and production/mean annual biomass ratios (P/B ratios) for each genus over both depths were: Tanytarsus, P = 744 to 8788, P/BB = 66 to 176; Cladotanytarsus, P = 74 to 2387, P/B = 69 to 100; Stempellina, P = 19 to 412, P/ B = 74 to 132; Chironomus, P = 166 to 7293, P/ B = 50 to 70; Cryptochironomus, P = 92 to 398, P/ B = 71 to 221. These estimates are among the highest reported for chironomids, due primarily to the rapid larval development times estimated for these genera.     

Beitrag zur Kenntnis der Sinnesorgane von Symphylen (Myriapoda)

Zusammenfassung Das Tömösvárysche Organ von Scutigerella immaculata wurde elektronenmikroskopisch untersucht. Es liegt in einer Epidermisinvagination direkt hinter der Basis der Antenne. Die Grube des Organs ist mit Kutikula ausgekleidet und steht durch eine rundliche Öffnung mit der Außenwelt in Verbindung. Zwei Drittel des Grubenraumes sind angefüllt mit einem Gitterwerk kutikulärer Stäbe, die distale Fortsätze von Sinneszellen enthalten. Unterhalb der Grube liegen mehrere Sinneszellen. Jede Sinneszelle formt proximal und distal einen schmäleren Fortsatz. Jeder distale Fortsatz läuft in zwei Zilienstrukturen aus, die unter Verzweigung in das Gitterwerk eintreten und sich auch dort weiter verzweigen. Die Sinneszellen werden von drüsigen Hüllzellen umfaßt. An ihnen können trichogene und tormogene Zellen unterschieden werden. Das Sekret der Hüllzellen umgibt die distalen Fortsätze der Sinneszellen von den Zilienstrukturen an bis in das Gitterwerk hinein. Die Kutikula des Gitterwerkes ist sehr dünn und von winzigen Poren durchsetzt.Nach einem Vergleich mit Sinnesorganen von Insekten muß vermutet werden, daß es sich beim Tömösváryschen Organ um ein Geruchssinnesorgan handelt, das vielleicht auch als Hygrorezeptor fungiert.

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Sense organs of symphyla (Myriapoda)II. Ultrastructure of the temporal organ of Scutigerella immaculata Newport

Summary The temporal organ of Scutigerella immaculata is situated in a pit just behind of the antenna. The pit represents an epidermal invagination. It is coated by cuticle and corresponds to the outside by a circular opening. More than half of the pit is filled up with a complicated network of branching and anastomosing cuticular protuberances. The cuticle of the protuberances is very thin and perforated by tiny pores. There are about ten sense cells situated under the pit, each of which forms a distal as well as a proximal process. Each distal process shows two ciliary structures. After branching they enter the cuticular protuberances and branch inside of it, as well. The sense cells are surrounded by glandular sheath cells, in which trichogen and tormogen cells can be distinguished. The secretion product of the sheath cells surrounds the distal parts of the sense cells inside of the cuticular protuberances. By comparison to sense organs of insects it must be presumed that the temporal organ represents an olfactory organ which may also function as hygroreceptor.

Ich danke Herrn Rau (Zentralinstitut für Elektronenmikroskopie der Technischen Universität Berlin) für die Durchführung der Arbeiten am Raster-Elektronenmikroskop und Frau Friedemann für die Anfertigung der Zeichnung.     

Taxonomy and nomenclature of five hitherto inadequately-known genera of mealybugs (Homoptera: Coccoidea: Pseudococcidae)

Abstract The type-species of four genera of Pseudococcidae are studied. Fonscolombia Lichtenstein is redefined, the type-species, Fonscolombia graminis Lichtenstein is assigned to the Pseudococcidae, redescribed and a lectotype designated. Laboulbenia Lichtenstein is accepted as an objective synonym of Antonina Signoret. Tetrura Lichtenstein ( non : Lesson) is accepted as an objective synonym of Coccura Sulc. The adult female of the material of this species which Lichtenstein misidentified as Tetrura rubi (Schrank) is redescribed and illustrated. Brevennia Goux is redefined, and the type-species Ripersia (Brevennia) tetrapora Goux redescribed. The characteristics of Asphodelococcus Morrison are discussed, the type-species Ripersia asphodeli Bodenheimer redescribed and a neotype designated; A.meoconcitae Tranfaglia & Marotta is a new synonym of A. asphodeli .     

Beitrag zur Kenntnis der Sinnesorgane von Symphylen (Myriapoda)

Zusammenfassung Am Präanalsegment von Scutigerella befindet sich ein Paar Trichobothrien, das komplizierter gebaut ist als entsprechende Sinnesorgane anderer Arthropoden. Die distalen Fortsätze von sechzehn Sinneszellen stehen mit der Gelenkmembran des nach allen Seiten beweglichen Sinneshaares in Verbindung. Aus ihrer Anordnung kann geschlossen werden, daß Scutigerella mit Hilfe des Trichobothriums mindestens acht verschiedene Richtungen unterscheiden kann. Der adäquate Reiz für die Trichobothrien dürften Luftbewegungen sein.

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Sense organs of symphyla (Myriapoda)I. Ultrastructure of the trichobothrium of Scutigerella immaculata newport

Summary One pair of trichobothria is situated on the lateral portions of the preanal segment of Scutigerella. They are rather complicated compared to similar organs of other Arthroods. The distal portions of 16 sense cells are connected to the elastic membrane of the sense hair which can be turned in every direction. From the arrangement of the distal parts of the sense cells it may be concluded that Scutigerella can distinguish at least eight different directions. Probably movements of the air are the adequate stimulus for the trichobothrium.

Für technische Mitarbeit danke ich Frl. M. Genehr und Fr. G. Schröer, für die Anfertigung der Zeichnung Fr. C. St. Friedemann.     

The ultrastructure of the midgut epithelium in millipedes (Myriapoda,Diplopoda)

The midgut epithelia of the millipedes Polyxenus lagurus, Archispirostreptus gigas and Julus scandinavius were analyzed under light and transmission electron microscopies. In order to detect the proliferation of regenerative cells, labeling with BrdU and antibodies against phosphohistone H3 were employed. A tube-shaped midgut of three millipedes examined spreads along the entire length of the middle region of the body. The epithelium is composed of digestive, secretory and regenerative cells. The digestive cells are responsible for the accumulation of metals and the reserve material as well as the synthesis of substances, which are then secreted into the midgut lumen. The secretions are of three types – merocrine, apocrine and microapocrine. The oval or pear-like shaped secretory cells do not come into contact with the midgut lumen and represent the closed type of secretory cells. They possess many electron-dense granules (J. scandinavius) or electron-dense granules and electron-lucent vesicles (A. gigas, P. lagurus), which are accompanied by cisterns of the rough endoplasmic reticulum. The regenerative cells are distributed individually among the basal regions of the digestive cells. The proliferation and differentiation of regenerative cells into the digestive cells occurred in J. scandinavius and A. gigas, while these processes were not observed in P. lagurus. As a result of the mitotic division of regenerative cells, one of the newly formed cells fulfills the role of a regenerative cell, while the second one differentiates into a digestive cell. We concluded that regenerative cells play the role of unipotent midgut stem cells.     

The allometry of metabolism in southern African millipedes (Myriapoda: Diplopoda)

Abstract. We determined standard metabolic rate at 25°C in forty-eight species of millipede from southern Africa and compared these data with confident measures of standard metabolic rate previously published for other arthropod groups.Metabolic rate in millipedes was not significantly different from that in beetles, ants or spiders once body mass effects had been accounted for, but was significantly higher than that in ticks.The exponent for the mass scaling of metabolic rate did not vary significantly between the five arthropod orders.Our best estimate for the relationship between standard metabolic rate (μl O₂ h^-1) and body mass (mg) in non-tick arthropods was 0.86 mass^0.73.     

Spatial organization of the antennal lobe in Cylindroiulus punctatus (Leach) (Myriapoda : Diplopoda)

The topography of the antennal afferent pathway has been studied in detail for the first time in a myriapod, Cylindroiulus punctatus, by cellular staining, following localized application of cobalt chloride to the cut end of one antenna. At the lateral entrance of the sensory antennal nerve into the deutocerebrum, 3 main groups of tracts have been distinguished. In the antennal lobe, there are two groups of glomeruli: a ventral group of 3 glomeruli and a dorsal group of 15 or 16 glomeruli. The number, position and dimensions of the glomeruli indicate that the glomerular organization is globally invariant (5 individuals).