Ultrastructure of the protonephridia in Pycnophyes kielensis (Kinorhyncha,Homalorhagida)

Summary Pycnophyes kielensis possesses one pair of protonephridia. The single excretory organ of a female consists of 25 cells: 22 terminal cells, 2 canal cells, and 1 nephroporus cell. Generally, all cells exhibit two cilia, the only exception being the nephroporus cell, which contains a diplosome instead. The slashed peripheral cytoplasmic walls of the 22 terminal cells altogether constitute one compound filter and a common filtration area. The protonephridia discharge via cuticularized cavities and six cuticularized tubes. Two accessory cells with modified cilia penetrate the nephroporus cell. These cells are considered to be receptor cells. The protonephridium of the first juvenile stage of P. kielensis is built up of only 5 cells: 3 terminal cells, 1 canal cell, and 1 nephroporus cell. It opens to the outside via 1 cuticularized tube. The protonephridia within both the Kinorhyncha and the Bilateria are discussed. Presumably excretory organs with compound filters developed independently within Bilateria.Abbreviations bb basal body - c canal cell - ca cuticularized cavity - ci cilium - cu cuticle - d dictyosome - de desmosome - di diplosome - dl dorsal longitudinal muscle - dv dorsoventral muscle - ecm extracellular matrix - ep epidermal cell - ex excretory organ - fc filter cleft - fi filter - fm fastening muscle cell - he hemidesmosome - i intestine - if intercellular fluid - m mitochondrium - mv microvilli - n nephroporus cell - nu nucleus - r ciliary rootlet - re accessory cell (presumable receptor cell) - sj septate junction - t terminal cell - tu cuticularized tube - v vesicle - w peripheral cytoplasmic wall     

Ultrastructure of the cephalic sensory organs of adult Pycnophyes dentatus and of the first juvenile stage of P. kielensis (Kinorhyncha, Homalorhagida)

 The ultrastructure of the paired cephalic sensory organs of adult Pycnophyes dentatus and of the first juvenile stage of P. kielensis (Kinorhyncha, Homalorhagida) was investigated by TEM. In both species, each sensory organ is composed of one receptor cell and one enveloping cell which border a common intercellular lumen. A single receptor cilium extends from the receptor cell into this lumen. The cilium expands behind the basal body and branches into numerous processes. A pair of cephalic sensory organs with these characteristics belongs to the ground pattern of, at least, the Pycnophyidae. The sensory organs of these Kinorhyncha correspond closely with the anterior cephalic organs of the Gastrotricha, but differ from the known cephalic receptors of other Nemathelminthes. Currently, it cannot be evaluated conclusively whether the last common ancestor of the Nemathelminthes possessed cephalic sensory organs and, if it did, what these organs looked like. Accepted: 3 December 1996     

Postembryonic development of Paracentrophyes praedictus (Homalorhagida): neoteny questionable among the Kinorhyncha

The postembryonic ontogeny of the kinorhynch Paracentrophyes praedictus is described by light microscopy and scanning electron microscopy. The development of head scalids and trunk Characteristics has been studied. The first of 6 juvenile stages possesses 11 segments already. One segment each is added both in stages 2 and 5. The number of head scalids increases during development. Every scalid becomes visible as a spinose anlage in one stage and differentiates in the next stage. All head scalids in stage 1 represent anlagen of scalids. Late juvenile stages J-5 and J-6 express two different scalid patterns which do not seem to depend on the gender. Scalids and trunk segments develop in a subfrontal and a subcaudal growing zone, respectively. The presumed neotenic status of P. praedictus is rejected because this species exhibits the same number of juvenile stages as observed in all other Kinorhyncha studied. It is suggested that a weakly sclerotized, juvenile-like trunk cuticle as found, e.g. in adult P. praedictus represents the plesiomorphic characteristic within the Kinorhyncha; a thickened cuticle has probably evolved independently within both the cyclorhagid and the homalorhagid Kinorhyncha.     

A New Species of Kinorhynchus (Homalorhagida, Pycnophyidae) from Australia with a Redescription and Range Extension of Other Kinorhyncha from the South Pacific

Kinorhynchus phyllotropis sp.n., from Sydney Harbour, is the first species of the phylum Kinorhyncha to be described from Australian coasts. It appears to be most closely related to K. anomalus (Lang, 1953) from the Chilean coast and possibly, but to a lesser extent, to K. spinosus (Lang, 1949) from the Falkland Islands in the South Atlantic. Kinorhynchus anomalus is rede-scribed and, along with the new species, is compared with the South Atlantic species, the two species known from the Northeast Pacific and the remaining four members of this genus from the North Atlantic, Mediterranean Sea and Black Sea. Cateria styx Gerlach, 1956, is reported from beaches north of Valparaiso, Chile, the first report of this mesopsarnmic cryptorhagid kinorhynch from the Pacific Ocean.     

Postembryonic development of Tisbe gracilis (T. Scott) (Copepoda, Harpacticoida)

All six naupliar and five copepodite stages of Tisbe gracilis (T. Scott, 1895) are described. A key for the identification of the nauplius stages is given. The oral appendages of all copepodite stages are described. Sexual dimorphism is visible from the copepodite IV stage on.     

Postembryonic development of Phyllodiaptomus blanci (Guerne & Richard, 1896) (Copepoda,Calanoida)

All the postembryonic developmental instars of Phyllodiaptomus blanci (Guerne & Richard, 1896), reared in the laboratory, are described and illustrated. The larval affinities of this species vis-a-vis certain other diaptomid species are mentioned.     

The musculature of Draculiciteria tessalata (Chaetonotida, Paucitubulatina): implications for the evolution of dorsoventral muscles in Gastrotricha

The muscular system of the marine interstitial gastrotrich Draculiciteria tessalata (Chaetonotida, Paucitubulatina) was analyzed with fluorescent phalloidin. Muscles in circular, longitudinal, helicoidal and dorsoventral orientations were found. Circular muscles were present as discreet rings on the pharynx only. Five pairs of longitudinal muscles were found in dorsal, lateral and ventral positions. One of the two pairs of lateral muscles is newly described for the species. Helicoidal muscles, external to the circular muscles and some longitudinal bands, spiraled around the pharynx and anterior portion of the intestine. Two pairs of segmentally-arranged dorsoventral muscles were also present. Lateral dorsoventral muscles extended from the base of the pharynx to the anterior part of the caudal furca. Medial dorsoventral muscles extended from the pharyngeal-intestinal junction into each ramus of the caudal furca. A hypothesis on the evolution of dorsoventral muscles in D. tessalata is proposed which includes a splitting of circular muscles into separate somatic and splanchnic components with a further displacement of both muscle sets into a dorsoventral orientation.     

A new kinorhynch genus,Mixtophyes (Kinorhyncha: Homalorhagida), from the Guinea Basin deep-sea,with new data on the family Neocentrophyidae

A new homalorhagid genus and species, Mixtophyes abyssalis gen. et sp. nov., is described from the deep-sea of the Guinea Basin in the Atlantic Ocean. The new genus and species was collected during the R/V Meteor Diva2 M63/2 Cruise, and it is characterized by a trunk with segment 1 consisting of a tergal and a single sternal plate, without any subdivisions or differentiations, segment 2–10 of one tergal and two sternal plates and segment 11 of a tergal and a sternal plate. Lateral terminal spines are present in both sexes. As part of the study of the new taxon, the type material of Neocentrophyes intermedius and N. satyai was re-examined, and new information is provided for both species. Based on the information from Mixtophyes abyssalis gen. et sp. nov. and re-examination of the two Neocentrophyes species, emended diagnoses for Neocentrophyes and Neocentrophyidae are proposed, and an updated identification key to homalorhagid genera and species of Neocentrophyidae is provided. Mixtophyes abyssalis gen. et sp. nov. is tentatively assigned to Neocentrophyidae, but evaluation of our current hypotheses about homalorhagid evolution and phylogeny also indicated that the family most probably is paraphyletic and that revision of homalorhagid classification is required when new results from phylogenetic analyses become available.     

Postembryonic development in Diaphanosoma brachyurum (Lievin, 1848) (Crustacea: Ctenopoda: Sididae)

Postembryonic females and males Diaphanosoma brachyurum from Lake Glubokoe (Moscow) have 3–4 and 3 juvenile instars, respectively. Females and males of the first three postembryonic instars can be identified by the different number of setae and setal rudiments on the proximal and distal segments of the exopodite of the swimming antennae: 3 + 7; (i + 3) + 7; 4 + (i + 7), respectively (i = rudiment of seta). The subsequent instars have 4 + 8 long plumose setae on these segments, but the fourth instar has the proximal lateral seta of the distal exopod segment slightly shorter and thinner than the others. The antennules and copulatory appendages of males are instar-specific. Diaphanosomas show small increments in body length during the postembryonic molts. The largest increments (about 115 m) occur during the first or second molts. The allometric equation of Huxley (1924) was used for a comparison of the relative growth rate of different body parts. In the middle of summer, the head and swimming antennae with the body and the antennal exopodite with the antennal basipodite grow in isometry. At the same time, the branches of the swimming antennae and their setae show allometric growth: the exopodite and distal setae grow faster than the endopodite and the lateral setae, respectively.     

Postembryonic development of the unique antenna of Mantophasmatodea (Insecta)

The postembryonic antennal development and life cycle of a member of the insect order Mantophasmatodea (Lobatophasma redelinghuysense) was investigated using a series of annulus counts and a time sequence of head capsule measurements. The life cycle comprised six instars. Females achieved significantly larger head capsules from instar 2 onwards, resulting in adult females having a larger mean head capsule diameter (2.58 mm) than males (2.27 mm). Antennae of first instar larvae comprised a smooth four-segmented basiflagellum and a seven-segmented, sensilla-rich distiflagellum. Lengthening of the basiflagellum was achieved by the addition of two annuli per moult, generated by division of the basal annulus (meriston). Annulus number and the unique annulation pattern of the distiflagellum remained constant until adulthood. The segmentation pattern of adult antennae (comprising a basiflagellum and a distiflagellum of 14 and seven annuli respectively) and mode of antennal elongation was consistent for all 11 species examined. Subdivisions in basiflagellar annuli were observed in adults of all species examined, although they are not considered to be true annular divisions. The structure of the mantophasmatodean antenna appears to be autapomorphic within Insecta, bearing little resemblance to that of Grylloblattodea, Dictyoptera or Phasmatodea, all putative sister groups of the Mantophasmatodea. However, the mode of flagellar elongation most closely resembles that of Isoptera, Blattaria and Dermaptera.     

Unique patterns of longitudinal body-wall musculature in the Acoela (Plathelminthes): the ventral musculature of Convolutriloba longifissura

The ventral musculature of Convolutriloba longifissura (Acoela) has been studied using electron microscopy and fluorescently labeled whole mounts to demonstrate filamentous actin. Attention was directed to the reorganization and renewal of musculature during asexual reproduction and the adaptation of muscle sets for special predatory behavior. Three ventral subepidermal muscle layers could be distinguished in adult C. longifissura: (1) outer circular muscles that encircle the body, (2) intermediate modified longitudinal muscles with concentric pattern around the mouth and V-shaped orientation in the posterior part of the animal, and (3) inner special pore muscles with radial alignment fanning out from the mouth. Additionally, a few very fragile muscles were found at the anterior margin of the animal. The anterior ventral muscle system built a funnel with the mouth opening as organizing center. The special radial muscles and the antagonistically concentric muscles are perfectly adapted to catch prey in such a way that the funnel is put over the prey to press it through the mouth into the digestive syncytium. Convolutriloba longifissura shows a unique way of asexual reproduction by a two-step fission which results in three individuals. Immediately after separation from the mother animal, daughter individuals are missing the concentric and the radial muscle sets around the mouth completely, but within 30 h these sets are renewed for the most part. Two to three days after separation, the mouth opening is visible and the animals move for capturing prey. The peculiar course of longitudinal muscles in C. longifissura with concentric rings anteriorly and a V-shape muscle layer posteriorly shows that the pattern of body-wall musculature in such basal Plathelminthes as the Acoela may be highly modified from the original pattern of longitudinal and circular muscles.     

Introvert,mouth cone,and nervous system of Echinoderes capitatus (Kinorhyncha,Cyclorhagida) and implications for the phylogenetic relationships of Kinorhyncha

Summary The introvert, mouth cone, and nervous system of Echinoderes capitatus were examined by transmission and scanning electron microscopy. The introvert bears seven rings of primarily quincunxial sensory scalids, including type 1 and 2 spinoscalids as well as trichoscalids; the latter two types are additionally provided with glandular cells. The mouth cone bears one ring of decamerous sensory oral styles and three rings of quincunxial sensory pharyngeal styles. The intra- to basiepithelial, bilateral nervous system consists of a circumentric nerve ring in the introvert, a terminal and proximal nerve ring in the mouth cone, a ventral chain of ganglia, one in each trunk zonite, and a caudal ganglion. The introvert, the neck, and the trunk zonites are innervated from the forebrain; the mouth cone and the pharyngeal bulb are innervated from the hindbrain. The monophyly of the Kinorhyncha is based upon the following autapomorphic characters: (1) a mouth cone, (2) a neck with 16 placids, (3) a trunk with 11 zonites, (4) scalids of three types: type 1 and type 2 spinoscalids, and trichoscalids, (5) an anteriormost ring of ten type 1 spinoscalids (sensory organs divided into a basal and a terminal part), (6) a posteriormost ring of 14 trichoscalids (glandular sensory organs which are undivided), (7) rings in between the anteriormost and posteriormost are type 2 spinoscalids (glandular sensory organs divided into a basal and a terminal part), (8) a mouth cone with a terminal and a proximal nerve ring, (9) nine sensory oral styles with decamerous symmetry (the dorsal style is missing) and (10) three rings of sensory pharyngeal styles with, from anterior to posterior, ten, five, and five styles with quincunxial arrangement. The following characters are assumed to be autapomorphic for the taxon Nematoda+Gastrotricha+Kinorhyncha+Loricifera+Priapulida: (1) a basiepithelial circumentric brain and (2) a neuropileous nerve ring in a subterminal position. The following characters are assumed to be autapomorphic for the taxon Kinorhyncha+Loricifera+Priapulida: (1) a neuropileous nerve ring in a terminal position, (2) an introvert with scalids, (3) an eversible foregut and (4) tanycytes.The unpublished doctoral thesis of B. Neuhaus [1991 Zur Ultrastruktur, Postembryonalentwicklung und phylogenetischen Verwandtschaft der Kinorhyncha. PhD thesis. University of Götingen, Germany] was finished simultaneously with the completion of this study.     

Postembryonic development of the ovary in the penicillate diplopod,Eudigraphis nigricans (Miyosi) (Diplopoda,Penicillata)

Postembryonic development of the ovary through the larval stages was studied in a penicillate diplopod, Eudigraphis nigricans. In the first instar larva a single young cell cluster, consisting of about 20 spherical gonial cells and some smaller interstitial cells, exists beneath the alimentary canal in the third body segment. The gonadal epithelium encompasses the upper surface of this young cell cluster by the end of the first instar. The epithelium then extends forward and backward to form a single long sac-like gonad, leaving the young cell cluster on the center of the gonadal floor as a mound-shaped germarium. In an early second-instar larva, very early previtellogenic oocytes accompanied by some interstitial cells appear in the front and rear surfaces of the ovarian germarium. During the period from the third through the seventh (the last) larval instar, some cell clusters containing several previtellogenic oocytes and interstitial cells successively separate forward and backward from the germarium to form a series of paired patch-shaped vitellarial areas on the extending ventral ovarian epithelium. In each vitellarial area, some of the interstitial cells surround the oocytes to form the follicles. In the seventh instar, the ovarian lumen is extremely expanded, and the late previtellogenic oocytes in the vitellarial areas encroach upward into the ovarian lumen. These oocytes floating in the ovarian lumen are still connected with their own vitellarial areas by partial extensions of their follicles. Some phylogenetic implications of the basic characteristics in structure and postembryonic development of the ovary are discussed. © 1995 Wiley-Liss, Inc.     

Sensory Spots of Echinoderes capitatus (Zelinka, 1928) (Kinorhyncha,Cyclorhagida)

The sensory spots of Echinoderes capitatus from the Gulf of Trieste were examined by transmission and scanning electron microscopy. Their arrangement is bilaterally symmetrical and is species-specific. At the cuticle surface the sensory spot appears as a rounded to ovoid area of small cuticular papillae in which two pores open. The sensory organ consists of two different sensory cells, the monociliary receptor and the collar receptor, and one sheath cell. The course of the axons and their connections to the nervous system are described. A survey of collar receptors among invertebrates is given. A comparison of the sensory spots within Kinorhyncha and a comparison with the flosculi of Priapulida and the N-flosculi of Loricifera is made. A possible homology of these three structures is discussed.     

Postembryonic development of the spider Enoplognatha ovata (Clerck) (Araneae:Theridiidae)

The postembryonic development of the three colour varieties of Enoplognatha ovata (CI.) was studied in the field and in the laboratory for two generations. Native and European spiders of this species were compared. Estimates of the number and duration of each stage were obtained from laboratory mating studies and verified by field studies. Males and females matured after five instars. Males matured faster than females but did not live as long. Each instar was characterized by several measurable parameters. All varieties over-winter in the second instar. Sexes could be easily separated at the fourth instar by comparing the ratio of the tarsal to patellar width of the pedipalps. Sexual dimorphism occurs at maturation ecdysis. Filial and mating studies indicate that the three colour varieties belong to a single species.     

Postembryonic development of Drescheriella glacialis Dahms & Dieckmann (Copepoda,Harpacticoida) reared in the laboratory

Summary All 6 naupliar and 5 copepodite stages of Drescheriella glacialis, a tisbid from Antarctic fast ice, are described. A key for the identification of the naupliar stages is given. Sexual dimorphism makes its first appearance in the copepodid IV. The setae configuration of the exopod of the second antenna in copepodid I is considered to be an ancestral state, and subsequent ontogenetic reductions are proposed to be apomorphic processes.     

Postembryonic development of anurans in ponds littered with metal-containing refuse (simulation experiments)

The effect of pond pollution with lead- and iron-containing alloys on the morphogenesis of brown frog (Rana temporaria), moor frog (Rana arvalis), and common toad (Bufo bufo) tadpoles was studied in simulation experiments. Observations showed that metal particles were ingested by tadpoles and produced a significant effect on their body dimensions. Tadpoles developing in water polluted with iron had an increased body size, while lead pollution resulted in retarded growth of tadpoles, and they were significantly smaller than in the control group. However, water pollution with metal alloys had no effect on the proportionality of their development.     

Postembryonic development of the cervicothoracic skeleton of Euborellia annulipes (Lucas) (Dermaptera: Labiduridae)

The nymphal and adult cervicothoracic skeleton of Euborellia annulipes (Lucas) is described and discussed.