Postembryonic development of Antygomonas incomitata (Kinorhyncha: Cyclorhagida)

Postembryonic development in the kinorhynch species Antygomonas incomitata was examined using scanning electron microscopy. The morphology of the six juvenile stages, J‐1 to J‐6, varies at numerous details, but they can also be distinguished by a few key characters. Juvenile stage 1 by its composition of only nine trunk segments; J‐2 by the combination of possessing 10 trunk segments, but no cuspidate spines on segment 9; J‐3 by the presence of cuspidate spines on segment 9, but only one pair of cuspidate spines on segment 8; J‐4 by the combination of 10 trunk segments only, but having two pairs of cuspidate spines on segment 8; J‐5 by possessing 11 trunk segments and same spine compositions as adults but is still maintaining postmarginal spiculae; J‐6 specimens closely resemble adults and are most easily identified by their reduced trunk lengths. New segments are formed in a growth zone in the anterior part of the terminal segment. The complete number of segments is reached in J‐5. Development of cuticular head and trunk structures are described through all postembryonic stages and following developmental patterns could be outlined: the mouth cone possesses outer oral styles from J‐1, but in J‐1 to J‐3, the styles alternate in size. Scalids of the introvert are added after each molt, and scalids appear earliest in the anterior rings, whereas scalids in more posterior rings are added in older postembryonic stages. The early J‐1 stage is poor in spines and sensory spots and both structures increase in number after each molt. The complete spine composition is reached in J‐4, whereas new sensory spots appear after all molts, inclusive the final one from J‐6 to adult. Sensory spots in the paraventral positions often appear as Type 3 sensory spots but are through development transformed to Type 2. This transformation happens earliest on the anterior segments. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

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.     

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 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 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 cervicothoracic muscles of Euborellia annulipes (Lucas) (Dermaptera: Labiduridae)

The cervicothoracic muscles of nymphal and adult Euborellia annulipes (Lucas) are described, the former for the first time. In the adult, eight new muscles are identified, while the nymphs possess a further seven muscles that disappear at maturation or before. Otherwise the same muscles occur in nymphs as in adults, though some nymphal muscles are less clearly separated from one another than their adult homologs. The attachment sites of certain muscles show a number of slight differences between nymphs and adults. The work emphasizes the necessity of taking the immature musculature into account in assessing the muscular pattern represented in an insect order.     

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.     

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.     

Postembryonic development of dorsoventral and longitudinal musculature in Pycnophyes kielensis (Kinorhyncha, Homalorhagida)

We investigated the development of dorsoventral and longitudinalmusculature in all postembryonic stages of the kinorhynch Pycnophyeskielensis. Although the earliest stages have only 8 externallyseparated trunk segments, they already possess dorsoventralmuscles for 10 (prospective) trunk segments. The last, 11th,pair is added in the third juvenile stage. Longitudinal musculature,in contrast, is slower to develop and reaches its full lengthonly in the adult. In several juvenile individuals, single fibersproject from the longitudinal musculature into the followingsegments. In all juvenile stages, longitudinal muscles are continuousbetween segments, whereas in adults they are segmentally separatedfrom each other. Such late occurrence of a segmental patternin the longitudinal musculature is in contrast to patterns ofmuscle development in arthropods and annelids.     

Factors determining the development of algal and bacterial blooms in the Dead Sea: a study of simulation experiments in outdoor ponds

Abstract To simulate the occurrence of bacterial and algal blooms in the Dead Sea, we filled 5.6 m³ outdoor ponds with mixtures of Dead Sea water and Mediterranean water, at different seasons, and studied the effect of salinity and of addition of glycerol, glucose and different concentrations of phosphate on the rate and extent of bacterial and algal growth. Addition of phosphate appeared to be essential for the development of mass blooms of both the green alga Dunaliella and of the red halobacteria. In the presence of phosphate the growth rates were high only when the Dead Sea water was diluted by at least 25–35% with Mediterranean water. Also, at low temperatures (14–17°C) mass blooms of bacteria and algae occurred, but growth rates were reduced, and the maximal salinity at which growth was observed shifted to a lower value. Glucose, glycerol and a Dunaliella bloom all proved to be suitable carbon sources for mass development of halobacteria.     

Postembryonic development of teratogen-induced supernumerary eyes in Acheta domesticus (L.) (Orthoptera : Gryllidae)

Supernumerary compound eyes were generated in the cricket Acheta domesticus (L.) (Orthoptera : Gryllidae) by applying the insect teratogen biquidone (benz[g]isoquinoline-5, 10-dione) and partially characterized teratogenic mixtures to eggs within 24 hr following oviposition at 31 ± 0.5°C. Postembryonic development of supernumerary eyes was compared with that of normal compound eyes, using light and scanning electron microscopy. All elements of the dioptric apparatus were present in supernumerary eyes of nymphs, but no axonal connection to the brain was found. Supernumerary eyes deteriorated during successive instars. Occasionally, these eyes were sloughed off before the adult stage was reached; more frequently, eyes appeared as highly pigmented protrusions not readily identifiable as adult eye tissue. Teratogen-induced supernumerary eyes are probably not functional light receptors in A. domesticus nymphs or adults.     

蛙的早期胚胎发育

根据多年来对一些经济蛙类的繁殖习性及胚胎发育的观察,并结合国内外有关的研究报道,介绍了两栖动物的繁殖类型及蛙类早期胚胎发育的过程,为教学提供有益的参考资料。     

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.     

Postembryonic development and homology of external genitalia in Galloisiana nipponensis (Caudell et king) (Notoptera : Grylloblattidae)

The postembryonic development of genital and postgenital segments of Galloisiana nipponensis (Notoptera : Grylloblattidae) have been described in detail. The coxite, stylus, epiproct and paraproct are already observed in the first nymphal instar, but the sexual characters are almost indistinguishable in the 1st to 4th nymphal instars, because the genital segments in these stages are not yet differentiated. In the 5th nymphal instar in the male, the paired primary phallic lobes start to appear at the hind margin of the 9th sternum. The rudiments of ventral valvulae in the female originate at the hind margin of the 8th sternum. In the 6th nymphal instar, the rudiments of inner valvulae begin to appear on the 9th sternum, in addition to the ventral valvula rudiments. The long dorsal valvulae are formed from the extension of nymphal coxite, while the nymphal styli are more reduced than those of younger instars.The ventral valvulae of the 8th abdominal segment are thought to be homologous with the inner valvulae of the 9th segment, judging from their site and mode of development. Further, the inner valvulae may also be homologous with the primary phallic lobes (phallomeres) of the male. The external genitalia in G. nipponensis originate from 2 structures: the dorsal valvulae (considered of appendicular origin), and the phallomeres; ventral and inner valvulae are regarded as mere integumentary outgrowths.     

Venue and outcome in ecological experiments: manipulations of larval anurans

The choice of venue is believed to be a critical decision for ecologists conducting experiments, yet the existence of tradeoffs in design and the impact of venue on outcome have not been quantitatively evaluated. To these ends we reviewed a set of 227 comparisons from 52 studies designed to quantify the effect of density on the growth performance of larval anurans. We predicted that both design and outcome would be related to experimental venue (laboratory, mesocosm, and field). We found that, in contrast to our predictions, laboratory experiments did not include more factors or yield more precise estimates of responses compared with mesocosm and field manipulations. In partial support of our prediction, we found that laboratory experiments did utilize somewhat larger numbers of replicates and included more levels per factor compared to the alternative venues. In addition we found that, as predicted, raising tadpoles at higher densities of conspecifics, or in the presence of heterospecifics tended to decrease growth. This effect, consistent with competition, was strongly dependent on experimental venue. In particular, we found that interspecific effects were much stronger in mesocosm versus field manipulations. This result is particularly relevant because conceptions of amphibian assemblages have included interspecific competition as integral to natural patterns of amphibian distribution. We conclude that hypothesized tradeoffs among experimental venues have not acted in a particularly strong way in shaping the design of tadpole density manipulations. However, venue may mediate strong effects on the outcome of such experiments. Quantification of such methodology based biases will help ecologists more effectively match the goals of their experiments with decisions regarding venue.