Fossil onychophorans from Dominican and Baltic amber: Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.g., n.sp. (Succinipatopsidae n.fam.) with a proposed classification of the subphylum Onychophora

Abstract. Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.gen., n.sp. (Succinipatopsidae n.fam.) (Lobopodia: Onychophora), the first Tertiary fossils of the Lobopodia, are described from Dominican and Baltic amber, respectively. Both families are characterized by the presence of simple legs lacking foot portions with claws and pads. Tertiapatidae is further characterized by soluble body pigments and oral papillae shorter than the legs. Succinipatopsidae is characterized by non-soluble body pigments and oral papillae longer than the legs. Nomenclatural changes include the erection of the class Udeonychophora n. nom. for terrestrial onychophorans with a ventral mouth, the order Ontonychophora n.nom. for extant onychophorans possessing legs with a differentiated "foot" portion, and the family Helenodoridae n.nom. for the genus Helenodora from the Carboniferous. The biogeographical significance of these fossils and their phylogenetic relationship with previously described onychophorans are discussed.     

Population structure and demographic inferences concerning the endangered onychophoran species Epiperipatus acacioi (Onychophora: Peripatidae)

Epiperipatus acacioi (Onychophora: Peripatidae) is an endemic species of the Atlantic rainforest in southeastern Brazil, with a restricted known distribution, found only in two nearby areas (Tripuí and Itacolomi). Mitochondrial gene COI sequences of 93 specimens collected across the known range of E. acacioi were used to assess the extant genetic diversity and patterns of genetic structure, as well as to infer the demographic history of this species. We found considerable variability within the populations, even though there has been recent environmental disturbance in these habitats. The samples from the two areas where this species is found showed significantly different COI sequences and constitute two distinct populations [exact test of sample differentiation (P = 0.0008) and pairwise F(ST) analyses (F(ST) = 0.214, P < 0.00001)]. However, there was little genetic differentiation among samples from different sampling sites within populations, suggesting that the potential for dispersal of E. acacioi greater than would have been expected, based on their cryptic behavior and reduced vagility. Mismatch analyses and neutrality tests revealed evidence of recent population expansion processes for both populations, possibly related to variations in the past distribution of this species.     

Ultrastructure of the rotifer integument: peculiarities of Sinantherina socialis (Monogononta: Gnesiotrocha)

The rotifer integument is a well‐described syncytium that contains an apical intracytoplasmic lamina (ICL) that functions for both skeletal support and muscle insertion. To date, there is limited information on the structure of the integument in species of Gnesiotrocha, a diverse subclade of Monogononta that consists of solitary, colonial, sessile, and planktonic species. In this study, we examined the ultrastructure of the integument in the colonial rotifer Sinantherina socialis to determine how it corresponds to that of other monogononts. The integument of S. socialis was broadly similar to that of other rotifers, consisting of a thickened glycocalyx, multilaminate ICL, and syncytial epidermis. However, it was different in several regards. The ICL consisted of three distinct layers from apical to basal: layer 1 consisted of at least two electron‐dense laminae; layer 2 was a thickened matrix of amorphous, electron‐dense material or was fibrous; and layer 3 was an electron‐dense lamina of varying thickness that covered the underlying syncytium. Significantly, layers 1 and 2 formed a ridge‐and‐groove like system of finger‐like projections across the trunk surface that has not been observed in other rotifers. A voluminous syncytial cytoplasm (up to 3 μm thick) was present beneath the ICL and was mostly electron lucent and with few organelles. Bundles of potential microtubules were scattered throughout the syncytium. We hypothesize that the voluminous cytoplasm with microtubules serves as skeletal support for the rotifer's sessile lifestyle, while the external ridges may function as a texture‐based deterrent to predators, or serves to trap secretions from the species' defensive glands. Basally, the epidermis was highly folded and bordered by a thin basal lamina that separated the plasmalemma from the blastocoel. Membrane‐bound vesicles were present throughout the integument's cytoplasm and are hypothesized to function in the secretion of extracellular matrix and in the maintenance of the ICL.     

Expression of the decapentaplegic ortholog in embryos of the onychophoran Euperipatoides rowelli

The gene decapentaplegic (dpp) and its homologs are essential for establishing the dorsoventral body axis in arthropods and vertebrates. However, the expression of dpp is not uniform among different arthropod groups. While this gene is expressed along the dorsal body region in insects, its expression occurs in a mesenchymal group of cells called cumulus in the early spider embryo. A cumulus-like structure has also been reported from centipedes, suggesting that it might be either an ancestral feature of arthropods or a derived feature (=synapomorphy) uniting the chelicerates and myriapods. To decide between these two alternatives, we analysed the expression patterns of a dpp ortholog in a representative of one of the closest arthropod relatives, the onychophoran Euperipatoides rowelli. Our data revealed unique expression patterns in the early mesoderm anlagen of the antennal segment and in the dorsal and ventral extra-embryonic tissue, suggesting a divergent role of dpp in these tissues in Onychophora. In contrast, the expression of dpp in the dorsal limb portions resembles that in arthropods, except that it occurs in the mesoderm rather than in the ectoderm of the onychophoran limbs. A careful inspection of embryos of E. rowelli revealed no cumulus-like accumulation of dpp expressing cells at any developmental stage, suggesting that this feature is either a derived feature of chelicerates or a synapomorphy uniting the chelicerates and myriapods.     

Expression of the decapentaplegic ortholog in embryos of the onychophoran Euperipatoides rowelli

The gene decapentaplegic (dpp) and its homologs are essential for establishing the dorsoventral body axis in arthropods and vertebrates. However, the expression of dpp is not uniform among different arthropod groups. While this gene is expressed along the dorsal body region in insects, its expression occurs in a mesenchymal group of cells called cumulus in the early spider embryo. A cumulus-like structure has also been reported from centipedes, suggesting that it might be either an ancestral feature of arthropods or a derived feature (=synapomorphy) uniting the chelicerates and myriapods. To decide between these two alternatives, we analysed the expression patterns of a dpp ortholog in a representative of one of the closest arthropod relatives, the onychophoran Euperipatoides rowelli. Our data revealed unique expression patterns in the early mesoderm anlagen of the antennal segment and in the dorsal and ventral extra-embryonic tissue, suggesting a divergent role of dpp in these tissues in Onychophora. In contrast, the expression of dpp in the dorsal limb portions resembles that in arthropods, except that it occurs in the mesoderm rather than in the ectoderm of the onychophoran limbs. A careful inspection of embryos of E. rowelli revealed no cumulus-like accumulation of dpp expressing cells at any developmental stage, suggesting that this feature is either a derived feature of chelicerates or a synapomorphy uniting the chelicerates and myriapods.     

Developing embryo and cyclic changes in the uterus of Peripatus (Macroperipatus) acacioi (Onychophora,Peripatidae)

Female reproductive tracts of the viviparous neo-tropical onychophoran Peripatus acacioi have been examined at different times throughout the year, and the altering relationship between the developing embryo and the uterus is described. Depending on her age and time of year, the female may have one or two generations of embryos within her uterus. The uterine wall consists of a thin outer epithelium and basal lamina, three layers of muscles, and a thick basal lamina beneath an inner epithelium lining the uterus lumen. These layers are consistent along the length of the uterus apart from the inner epithelial lining, which varies according to position in the uterus and the developmental stage of embryos contained in the uterus. Early embryos are positioned along the length of the uterus and therefore have space in which to grow. During cleavage and segment formation, each embryo is contained within a fluid-filled embryo cavity that increases in size as the embryo grows. Morulae and blastulae are separated by lengths of empty uterus in which the epithelial lining appears vacuolated. Until the process of segment formation is complete, the embryos are attached to a placenta by a stalk and remain in the same part of the upper region of the uterus. As these embryos grow, the lengths of vacuolated cell-lined uterus between them decrease. Each embryo cavity is surrounded by the epithelial sac, the maternal uterine epithelium, which becomes overlaid by a thin layer of cells, the embryo sac, which is believed to be of embryonic origin. The placenta is a syncytial modification of the epithelial sac located at the ovarian end of each embryo cavity covered by the embryo sac and is analogous to the mammalian noninvasive epitheliochorial placenta. Segment-forming embryos have their heads directed toward the ovary. As the embryo gets longer during segment formation, its posture changes from coiled to flexed. Once segment formation is complete, the embryo loses contact with its stalk, an embryonic cuticle forms, and the embryo turns around so that its head is directed toward the vagina. The embryo escapes from its embryo sac and moves to the lower part of the uterus. In the lower part of the uterus, the straightened fetuses are first unpigmented but subsequently become pigmented as the secondary papillae on the body surface form and an adult-type cuticle forms beneath the embryonic cuticle. While the embryos are contained within their embryo cavities, nutrients are supplied by the placenta. Throughout development the mouth is open and in the mature fetus the gut is lined by peritrophic membrane and material is present in the gut lumen. Trachea have been observed only in fetuses that were ready for birth. Insemination, cyclical changes in the uterine epithelium, and the nature of the cuticle shed at parturition are discussed. © 1995 Wiley-Liss, Inc.     

Ecdysteroid levels and integument changes in post-embryonic stages of Anastrepha suspensa

Ecdysteroid levels in larvae and pupae of Anastrepha suspensa (Diptera: Tephritidae) were measured by radioimmunoassay. These levels were correlated with histological changes throughout the development of the post-embryonic stages. Ecdysteroid levels increase rapidly throughout the last-larval instar and on the last day of this stage are 283 pg equivalents of 20-hydroxyecdysone per insect (14.5 ng/g) when wandering behaviour is initiated. At the end of this period the puparium is formed and within 24 h, the ecdysteroid rises to its highest peak (625 pg equivalents of 20-hydroxyecdysone/insect). Larval-pupal apolysis is initiated within 24 h later and the pupal cuticle is then secreted. Two days later, the ecdysteroids reach their lowest levels (75 pg equivalents of 20-hydroxyecdysone/insect or 0.6 ng/g) and most of the larval fat body and other tissues have been histolysed. In 5- to 10-day old pupae ecdysteroid levels again increase and remain relatively high throughout. During this period the larval epidermis is replaced by imaginal epidermis, imaginal discs begin to proliferate and the adult cuticle is secreted. Ecdysteroid levels finally fall 2 days prior to adult emergence. HPLC determinations indicate that 20-hydroxyecdysone is the predominant free ecdysteroid, and along with ecdysone, is readily detectable in all postembryonic stages of this species. An unusually high and unexplained peak of 20-hydroxyecdysone occurs in the pharate adult. This peak probably consists of ecdysone metabolites with retentions similar to that of 20-hydroxyecdysone and to which the antiserum is sensitive.     

Diflubenzuron-Induced alterations during in vitro development of Tenebrio molitor pupal integument

The effects of diflubenzuron (DFB) in Tenebrio molitor pupae were first investigated on cuticle secretion induced by 20-hydroxyecdysone in vitro. The sternal integuments were treated by DFB either 3 days before culture or during culture. DFB, when applied before culture, did not prevent the molting hormone from inducing a new cuticle deposition by integument explants in vitro. However, this cuticle showed several architectural alterations and a thickness reduction. When applied during the culture in the presence of 20-hydroxyecdysone, DFB at high dose (≥ 20 μg/ml) was able to inhibit cuticle secretion, but lower doses (? 10 μg/ml) resulted in epicuticle deposition. These observations confirm in vivo studies showing antagonistic effects of DFB and ecdysteroids at the level of epidermal cells. In another series of experiments, the DFB effects were analyzed without addition of exogenous molting hormone in vitro. Because it had been observed in previous studies that pupal epidermal explants of Tenebrio secrete low but significant amounts of ecdysteroids in the culture medium, this in vitro secretion was measured by radioimmunoassay after DFB treatment. It was observed that DFB, when applied either before or during culture, significantly reduced the hormonal secretion in vitro. This reduction, observed at the level of epidermal cells, could be homologous with the diminution of the endogenous ecdysteroid peak previously described after in vivo DFB treatment in Tenebrio pupae.     

Chiton integument: Metamorphic changes in Mopalia muscosa (Mollusca,Polyplacophora)

Summary The larval integument and juvenile girdle integument of Mopalia muscosa (Mollusca: Polyplacophora) were studied by light microscopy. Within 24 h of settlement, eight distinctive changes occur that characterize metamorphosis: loss of the functional prototroch and apical tuft, secretion of a cuticle over the mantle field followed by the secretion of calcareous shell plates and the extrusion of spicules into the cuticle, a 20% decrease in length, secretion of chitinous hairs and the incorporation of the lateral ciliated bands into the pallial grooves. Similar changes which were often not recognized as metamorphic have been reported for other species. Evidence for metamorphosis being a common developmental feature of chitons is presented.     

Ultrastructure and fate of the nephridial anlagen in the antennal segment of Epiperipatus biolleyi (Onychophora, Peripatidae)—evidence for the onychophoran antennae being modified legs

In this study, new ultrastructural data on the nephridiogenesis in Epiperipatus biolleyi (Onychophora) are provided, and the general distribution of nephridial organs, their vestigia, and derivatives within the onychophoran body is revised. Transient anlagen of nephridial organs proved to be present in the anteriormost segment bearing the antennae. These nephridial anlagen were never found to open to the exterior in any developmental stage studied, but are nevertheless equipped with well-developed cilia. The ciliated nephridial canals are situated at the antennal bases, hence in a more dorsal position than in the remaining body segments. In postantennal segments, the nephridial anlagen constantly arise at the bases of the presumptive legs or their derivatives. These results provide the first evidence that onychophoran antennae are modified legs that retained the original arrangement of the nephridial anlagen at their bases, despite the evolutionary change in position and function of these legs. Current assumptions are accordingly confirmed that the onychophoran antennae and the first antennae in Mandibulata (Euarthropoda) are non-homologous, since they have to be attributed to different head segments. Although the fate of the homologue of the onychophoran antennae in the Euarthropoda remains to be clarified, insights obtained in the present study question previous claims that an ocular segment is absent in extant Mandibulata.     

The extensible integument of Rhipicephalus sanguineus female ticks in different feeding stages: a morphological approach

Ticks are among the most important pathogen vectors worldwide, and the knowledge of their internal and external morphology may provide relevant information that will allow an adequate control of these animals. In this sense, the integument gains prominence, not only because of its wide capacity of expansion, but also due to the fact that this region is usually the first site of contact with natural and synthetic acaricides. Therefore, this study aimed to describe the morphology of alloscutal integument of R. sanguineus female ticks in three different feeding stages by means of histological and ultramorphological analysis. Significant differences were observed in all stages, with respect to the size of cells and layers, and to cuticle unfolding throughout the feeding process. Cuticle is divided into two main layers, the epicuticle and the procuticle, and is separated from a unistratified epithelium by a subcuticular layer. Procuticle, in turn, is divided into two layers, the endocuticle and exocuticle. Unfed female ticks showed cuticle with numerous folds, which decrease in quantity as the feeding expansion of the whole animal occurs. Opening of dermal glands and presence of setae also differed among groups.     

Structure of the Cuticle of Ceramonema carinatum (Chromadorida: Ceramonenatidae)

The cuticle of Ceramonema carinatum (Chromadorida: Ceramonematidae) is described and illustrated from scanning and transmission electron microscopy. Each of ca. 200 annules is composed of a single ring with eight external flat faces (plates), which are divided by longitudinal ridges formed by pairs of parallel upstanding vanes. Vanes and plates overlap those of the adjacent annules. Longitudinal ridges extend from the cephalic capsule to the tail spike. On the cephalic capsule a simple ridge extends each of the eight ridges to a position just anterior to the amphid. Cuticular plates are formed from the electron-dense cortical layer and contain lacunae filled with fine fibrils. The vanes are denser, with laminations on a central core. In the annular grooves between the plates there is an electron-lucent layer, which it is suggested, by comparison with other nematodes, is the basal layer. An epicuticle overlies the cortical plates, the vanes, and the interannular lucent layer. Cuficular structure is compared with that of other Ceramonematidae and related nematodes.     

Histochemistry of the cuticle of the crab Menippe rumphii (Fabricius) (Crustacea: Brachyura) in relation to moulting

Histological and histochemical methods have been employed to study the formation and growth of the exoskeleton in relation to the moulting cycle of the crab Menippe rumphii (Fabricius). In the premoult condition the epidermal cells secrete a two-layered cuticle. Later these layers are widened by the secretions coming from the reserve cells, tegumental glands, and the Leydig cells. The fully formed cuticle of the intermoult crab is divisible into four layers, epicuticle, exocuticle, mesocuticle, and endocuticle.Histochemical observations on different cells have revealed that the tegumental glands secrete both neutral and acid mucopolysaccharides. The reserve cells are positive to PAS, BPB, Sudan Black B and Alizarin Red S techniques indicating the presence of carbohydrates, proteins, lipids, and mineral calcium. The Leydig cells are loaded with enzymes, including alkaline phosphatase, acid phosphatase, lipase, and phenoloxidase. Other histochemical tests have been employed to investigate the formation of different layers of the cuticle.     

Global diversity of nemerteans (Nemertea) in freshwater

Most ribborn worms (phylum Nemertea) are marine and only 22 of the currently named around 1,200 species are known from freshwater habitats (mainly lakes/ponds). They are all free-living benthic forms found in all continents except Antarctica. The vast majority of species have been recorded from the Palearctic region, but this may reflect sampling efforts rather than biogeography. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Structure of the Cuticle of Metadasynemoides cristatus (Chromadorida: Ceramonematidae)

Structure of the cuticle of Metadasynemoides cristatus (Chromadorida: Ceramonematidae) is examined by light, scanning, and transmission electron microscopy. The nematode has more than 600 annuli, and each annulus has eight cuticular plates. Eight longitudinal ridges, beginning on the cephalic capsule, extend the whole length of the body. Where a ridge traverses an annulus, it forms a complicated articulating structure of overlapping vanes. Within the electron-dense cortical layer, from which the cuticular plates are formed, there are spaces crossed by fine fibrillae, forming what have been termed "vacuoles" by light microscopists. There is an epicuticle and a continuous lucent basal layer. There appears to be no median layer. The cuticle lining of the esophagus and that forming the circum-oral ridge is of much simpler construction.     

Ultrastructural investigations of the female genital system of Epiperipatus biolleyi ( Bouvier 1902) (Onychophora,Peripatidae)

Brockmann, C., Mummert, R., Ruhberg, H. and Storch, V. 1999. Ultrastructural investigations of the female genital system of Epiperipatus biolleyi (Bouvier 1902) (Onychophora, Peripatidae). — Acta Zoologica (Stockholm) 80: 339–349. The female genital system of the neotropical peripatid Epiperipatus biolleyi was examined using transmission and scanning electron microscopy. Special attention is given to the two accessory organs of the paired oviducts: the receptacula seminis and the ovarian funnels (Ovarialtrichter). The latter occur only in the Peripatidae, whereas receptacula seminis may also be present in the Peripatopsidae, the only other family in the Onychophora. The ovarian funnels of E. biolleyi are thin-walled and closed from the haemocoel. This trait has also been reported from Epiperipatus trinidadensis, Macroperipatus torquatus, and Eoperipatus weldoni, whereas other peripatids have ovarian funnels which have been reported to open into the haemocoel. The occurrence of artificially opened ovarian funnels, caused by tissue rupture during specimen preparation, is discussed. The presence of spermatozoa both in the receptaculum seminis and in parts of the uterus of the female examined in this study supports the hypothesis that in E. biolleyi insemination of juvenile females occurs directly via the genital opening. The female contained one unstalked cleavage embryo in each uterus horn. Two features of the uterus were found to be unique to E. biolleyi: (1) a second cell layer overlying the uterine epithelium with a pronounced secretory activity (2) embryos are enclosed in a noncellular coat interspersed with numerous transport vesicles.     

Age and Growth by Scale Analysis of Pomacanthus imperator (Teleostei: Pomacanthidae) from Dongsha Islands, Southern China

A total of 200 specimens of Pomacanthus imperator from Dongsha Islands (South China Sea), were examined for age and growth. Scale radial length (R) is linearly proportional to standard length (L) and their relationship can be expressed by the formula L=3.6+43.8R. Relationship between standard length and body weight (W) can be expressed by the formula W=1.63×10^–4L^2.77. Mean standard lengths of each age group were back-calculated from scale annuli readings and were found to be 66.4, 94.2, 120.7, 133.9, 145.6, 157.9, 170.7, 188.0, 200.9, 217.6, 222.0, 242.8, 253.0, 268.1, 277.0 and 293.0mm for age classes 1 through 16, respectively. The von Bertalanffy parameters L, K, and t_o fitted to back-calculated standard lengths were, respectively, 411.9mm, 2852.1g, 0.067years^–1, and –0.91 years. Marginal increment analysis indicated that annulus formation takes place between January and March.     

The expanding alloscutal cuticle in adults of the argasid tick Argas (Persicargas) robertsi (Acari: Ixodoidea)

The extensible cuticle of Argas (P.) robertsi is tuberculate and deeply folded when the tick is unfed but expands rapidly during feeding. During this expansion the epicuticle becomes less convoluted and the underlying endocuticle stretches but there is no significant alteration in thickness. However, the stretched cuticle has taken on a more open structure. Increase in surface area is restricted to a blister-like expansion because of an inextensible lateral suture which separates the dorsal and ventral surfaces. The cuticle is very hydrophobic, contains 9.9% chitin in the female and 8.9% in the male and the cuticular proteins are largely basic. The cuticle has similar properties to that of the ixodid tick Boophilus microplus but differs from it in fine structure. These differences appear to be related to the time sequence of cuticle synthesis and deposition and to the cycle of expansion and contraction which takes place each time A. (P.) robertsi feeds.     

The application of scanning electron microscopy to the systematics of the neotropical Peripatidae (Onychophora)

The taxonomy of the New World Peripatidae is poorly known both because of their rarity and difficulty in the determination of specimens. The distribution of papillae on the dorsal integument is an important taxonomic; character but is difficult to interpret under the light microscope. In this study the integument of a range of New World onychophoran species was studied using scanning electron microscopy. Twenty-one species were examined. Three species of Peripatopsidae were also studied for comparison. This technique revealed (a) the pattern of distribution of papillae on the integument, and (b) the morphology of the papillae. A pattern of three smaller papillae between two large was common to many species. Differences observed in some species were probably modifications of this basic pattern. There was interspecific variation in the number of scales in the apical and basal pieces of the papillae. The specimens examined fell into two main groups: (1) species with more than three scale ranks in the apical piece ( Oroperipatus and Peripatus ) and (2) species with three or fewer scale ranks ( Epiperipatus, Macroperipatus and others). The results thus support a distinction between Epiperipatus and Peripatus . However Macroperipatus is shown not to be a natural group. The relationships of some species which did not fit into this pattern are discussed. This paper shows scanning electron microscopy to be a potentially useful technique in a revision of the New World Peripatidae.