Development of pigmentation and skeleton in ontogenesis of Fedorov eelpout <Emphasis Type="Italic">Zoarces fedorovi</Emphasis> (Zoarcidae,Perciformes) from the Sea of Okhotsk

The development of pigmentation of the Fedorov eelpout (Zoarces fedorovi) from hatching out of egg integuments to delivery is studied. In Z. fedorovi, the adult coloration develops immediately, without larval coloration, obviously, due to viviparity. Comparative analysis of the sequence of anlage and morphogenesis of elements of the cartilaginous skeleton and the bony skeleton demonstrated that the sequence of anlage of cartilaginous and bony regions of the skeleton of Z. fedorovi principally correspond to the sequence in Z. viviparus and in other perciform fishes. Morphogenesis of the bones of ethmoidal and interorbital regions of the skull, of the axial skeleton, and of the skeleton of the caudal fin is highly similar in eelpouts and other fishes of the suborder Zoarcoidei, differing from that in the generalized perciform fishes. At the same time, the larvae of Z. fedorovi in comparison with Z. vivparus are characterized by a higher rate of development of the skeleton. Advanced structural traits in structure of the skeleton of larvae of Z. viviparus in comparison with Z. fedorovi are pointed out. Differences in size at which anlage of bony elements occurs, as well as in the formation of particular bony elements seem to indicate to a rather prolonged divergence of these species.     

Observations of growth and postspawning survival of lumpfish Cyclopterus lumpus from mark‐recapture studies

Growth and postspawning survival of lumpfish Cyclopterus lumpus are described by mark‐recapture experiments using juveniles in offshore areas in the north‐east Atlantic Ocean and spawning adults in coastal Norway and Iceland. A female fish tagged as a juvenile and recaptured as an adult matured in a period of 18 months, providing the first observation on development in a wild C. lumpus. The von Bertalanffy growth function, fitted to data from recaptured fish, was used to estimate K and L_∞ and recaptured fish spawning after a year at liberty indicated a postspawning survival of c. 10% in Iceland.     

Effect of Monochamus carolinensis on the Life History of the Pinewood Nematode,Bursaphelenchus xylophilus

The development of Bursaphelenchus xylophilus in pine wood infested with and free of Monochamus carolinensis was investigated. Formation of third-stage dispersal juveniles occurred in the presence and absence of pine sawyer beetles. The proportion of third-stage dispersal juveniles in the total nematode population was negatively correlated with moisture content of the wood. Formation of nematode dauer juveniles was dependent on the presence of the pine sawyer beetle. Dauer juveniles were present in 3 of 315 wood samples taken from non-beetle-infested Scots pine bolts and 81 of 311 samples taken from beetle-infested bolts. Nematode densities were greater in wood samples taken adjacent to insect larvae, pupae, and teneral adults compared with samples taken from areas void of insect activity. Nematodes recovered from beetle larvae, pupae, and teneral adults were mostly fourth-stage dauer juveniles, although some third-stage dispersal juveniles were also recovered. Dauer juvenile density was highest on teneral adult beetles.     

Occurrence of skeletal deformities and osteological development in red porgy Pagrus pagrus larvae cultured under different rearing techniques

The present study describes the osteological development and the occurrence of skeletal deformities in red porgy Pagrus pagrus larvae in relation to the intensification of the rearing system. Eggs obtained from natural spawning were cultured under two different rearing systems: intensive (100 eggs l^?1) in 2000 l and semi‐intensive (mesocosm) system (5 eggs l^?1) in 40 000 l conico‐cylindrical tanks. Fish samples were periodically collected along the development from hatching to juveniles at 95 days post hatching (dph). Osteological development, meristic counts and the presence of skeletal deformities were evaluated. Despite the external appearance of the juveniles being similar to wild standards, X‐ray studies revealed a high number of fish (semi‐intensive: 37·8%; intensive: 45·5%) with skeletal deformities. Regardless of the rearing system, no significant interaction was found between the per cent of the most common deformities, axial deviations (lordosis and presence of fused vertebrae). Cranial deformities and kyphosis incidences, however, were significantly higher in intensively cultured P. pagrus. Also, the fused vertebrae in these fish were located mainly in the caudal area instead of pre‐haemal area for semi‐intensively reared P. pagrus. Moreover, a significant interaction was found between the total number of vertebrae and the type of rearing system used; fish from the intensive system showing a higher number of fish with an extra vertebrae (10 abdominal + 15 caudal). Present results suggest a relationship among feeding sequence, osteological development and deformity incidence and location in P. pagrus larvae.     

External Morphology of Lophiosilurus alexandri Steindachner, 1876 during Early Stages of Development,and Its Implications for the Evolution of Pseudopimelodidae (Siluriformes)

Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens. The largest species of the family with 500 mm SL, Lophiosilurus alexandri, experiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an ideal species to observe the morphological changes during ontogeny, and to seek solid interpretations on the polarity of characters. Specimens of distinct larval periods (yolk sac, flexion and postflexion; n = 186 specimens) and juvenile stages (n = 20) were analyzed. Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. Larvae (5.7–11.2 mm standard length) had pigmentation concentrated on the head and parts of body, eyes small and pigmented, short barbels, and well-developed finfold. Juveniles (15.9–28.1 mm standard length) had body shape similar to adult, with head depressed and bearing bony ridges, large mouth, dorsally-oriented eyes, small barbels and well-developed shoulder bulges (cleithral width). The greatest morphological changes in the development of L. alexandri occurred during the postflexion larval stage. Relative to standard length, measurements of snout length, head depth and body depth are smaller in juveniles than in larvae, but body width is larger. New interpretations on the phylogenetic characters related to these changes are provided in view of the two alternative hypotheses of the evolution of Pseudopimelodidae.     

Environmental Conditioning of Skeletal Anomalies Typology and Frequency in Gilthead Seabream (Sparus aurata L., 1758) Juveniles

In this paper, 981 reared juveniles of gilthead seabream (Sparus aurata) were analysed, 721 of which were from a commercial hatchery located in Northern Italy (Venice, Italy) and 260 from the Hellenic Center for Marine Research (Crete, Greece). These individuals were from 4 different egg batches, for a total of 10 different lots. Each egg batch was split into two lots after hatching, and reared with two different methodologies: intensive and semi-intensive. All fish were subjected to processing for skeletal anomaly and meristic count analysis. The aims involved: (1) quantitatively and qualitatively analyzing whether differences in skeletal elements arise between siblings and, if so, what they are; (2) investigating if any skeletal bone tissue/ossification is specifically affected by changing environmental rearing conditions; and (3) contributing to the identification of the best practices for gilthead seabream larval rearing in order to lower the deformity rates, without selections. The results obtained in this study highlighted that: i) in all the semi-intensive lots, the bones having intramembranous ossification showed a consistently lower incidence of anomalies; ii) the same clear pattern was not observed in the skeletal elements whose ossification process requires a cartilaginous precursor. It is thus possible to ameliorate the morphological quality (by reducing the incidence of severe skeletal anomalies and the variability in meristic counts of dermal bones) of reared seabream juveniles by lowering the stocking densities (maximum 16 larvae/L) and increasing the volume of the hatchery rearing tanks (minimum 40 m³). Feeding larvae with a wide variety of live (wild) preys seems further to improve juvenile skeletal quality. Additionally, analysis of the morphological quality of juveniles reared under two different semi-intensive conditions, Mesocosm and Large Volumes, highlighted a somewhat greater capacity of Large Volumes to significantly augment the gap with siblings reared in intensive (conventional) modality.     

Using experimental ecology to understand stock enhancement: Comparisons of habitat-related predation on wild and hatchery-reared Penaeus plebejus Hess

Marine stock enhancement is often characterized by poor survival of hatchery-reared individuals due to deficiencies in their fitness, such as a diminished capacity to avoid predators. Field experiments were used to examine predation on Penaeus plebejus, a current candidate for stock enhancement in Australia. We compared overall survival of, and rates of predation on, wild P. plebejus juveniles, naïve hatchery-reared juveniles (which represented the state of individuals intended for stock enhancement) and experienced hatchery-reared juveniles (which had been exposed to natural predatory stimuli). Predation was examined in the presence of an ambush predator (Centropogon australis White, 1790) and an active-pursuit predator (Metapenaeus macleayi Haswell) within both complex (artificial macrophyte) and simple (bare sand and mud) habitats. Overall survival was lower and rates of predation were higher in simple habitats compared to complex habitats in the presence of C. australis. However, the three categories of juveniles survived at similar proportions and suffered similar rates of predation within each individual habitat. No differences in survival and rates of predation were detected among habitats or the categories of juveniles when M. macleayi was used as a predator. These results indicate that wild and hatchery-reared P. plebejus juveniles are equally capable of avoiding predators. Furthermore, exposure of hatchery-reared juveniles to wild conditions does not increase their ability to avoid predators, suggesting an innate rather than learned anti-predator response. The lower predation by C. australis in complex habitats was attributed to a reduction in this ambush predator's foraging efficiency due to the presence of structure. Ecological experiments comparing wild and hatchery-reared individuals should precede all stock enhancement programs because they may identify deficits in hatchery-reared animals that could be mitigated to optimize survival. Such studies can also identify weaknesses in wild animals, relative to hatchery-reared individuals, that may lead to the loss of resident populations.     

Comparative osteology of <Emphasis Type="Italic">Cyclopsis tentacularis</Emphasis> (Cyclopteridae,Scorpaeniformes)

The structure of the skeleton of Cyclopsis tentacularis, an endemic species from the northern part of the Sea of Okhotsk, is studied for the first time. Generally, it corresponds to that in other representatives of Cyclopteridae. The differences in structure of Cyclopsis and of other investigated cyclopterids are both plesiomorphic and apomorphic. The plesiomorphic ones are comprised of sutural articulation of pteroticum and prooticum, spiny ray in the beginning of D2, berycoid opening in ceratohyale, bony pharyngobranchiale 2, emergination in the anterior margin of scapula, and postcoracoid opening in coracoideum. The apomorphic ones are separation of parietalia, absence of bony basibranchialia, presence of emargination in the posterior margin of supracleithrum, and reduction of several last epipleural ribs. The presence of numerous plesiomorphies does not confirm Ueno’s viewpoint (Ueno, 1970) on the advanced position of Cyclopsis in the family Cyclopteridae. Final conclusions on the position of Cycloposis in the system of cyclopteridae and of the system of this family itself may be made only after proper investigation of the external morphology and osteology of all genera of Cyclopteridae.     

Manipulation of Developing Juvenile Structures in Purple Sea Urchins (Strongylocentrotus purpuratus) by Morpholino Injection into Late Stage Larvae

Sea urchins have been used as experimental organisms for developmental biology for over a century. Yet, as is the case for many other marine invertebrates, understanding the development of the juveniles and adults has lagged far behind that of their embryos and larvae. The reasons for this are, in large part, due to the difficulty of experimentally manipulating juvenile development. Here we develop and validate a technique for injecting compounds into juvenile rudiments of the purple sea urchin, Strongylocentrotus purpuratus. We first document the distribution of rhodaminated dextran injected into different compartments of the juvenile rudiment of sea urchin larvae. Then, to test the potential of this technique to manipulate development, we injected Vivo-Morpholinos (vMOs) designed to knock down p58b and p16, two proteins involved in the elongation of S. purpuratus larval skeleton. Rudiments injected with these vMOs showed a delay in the growth of some juvenile skeletal elements relative to controls. These data provide the first evidence that vMOs, which are designed to cross cell membranes, can be used to transiently manipulate gene function in later developmental stages in sea urchins. We therefore propose that injection of vMOs into juvenile rudiments, as shown here, is a viable approach to testing hypotheses about gene function during development, including metamorphosis.     

Stage dependent habitat use under conflicting predation pressure: An experimental test with larval and juvenile two-spotted gobies, Gobiusculus flavescens Fabricius

The effect of size, predator types and presence of multiple predators on the microhabitat use of larvae and juveniles of a sublittoral, semipelagically schooling fish, the two-spotted goby (Gobiusculus flavescens), was tested in two experiments. Larvae (15 and 25 days old, Experiment I) and juveniles (mean ± 1 S.E.: small, 15.9 mm ± 1.28; medium, 19.2 mm ± 1.43; and large, 23.4 mm ± 1.67, Experiment II) were allowed to choose between two sections of the tanks; an upper, representing a water column habitat, and a lower, artificially vegetated, representing the hyperbenthic habitat. Position of larvae or juveniles and the activity level of juveniles were recorded. Predator treatments were: (I) no predators (control), (II) a pelagic predator, the jellyfish Aurelia aurita L., (III) a hyperbenthic predator, the mysid Praunus flexuosus O.F. Müller or (VI) both predator types simultaneously. In Experiment I predators were restricted to the habitat which they were chosen to represent, while goby larvae could move freely. In Experiment II both predators and juvenile gobies were allowed to move freely between compartments.Increasing age caused larval gobies, but not juveniles to shift downwards. Only 25-day-old larvae and small juveniles avoided the mysid by shifting upwards. Larval response to A. aurita was also size dependant: 25-day-old larvae avoided medusae by shifting downwards, while 15 day olds did not. Emergent multiple predator effects were found for the vertical distribution of 15-day-old larvae and small juveniles. Larger juveniles were more active than smaller, both in the upper and the lower sections of tanks. P. flexuosus caused juvenile gobies in their vicinity (i.e. in the lower section) to increase their activity level, while small juveniles (but not medium-sized or large) increased their activity level even when further away (i.e. in the upper section). The presence of A. aurita led to a reduction in activity of small juveniles in its vicinity (i.e. in the upper section), while no response was observed among older juveniles or juveniles further away from the predator (i.e. in the lower section). Emergent multiple predator effects on the activity level of juveniles were not observed.     

Vertical Transmission of a Phylogenetically Complex Microbial Consortium in the Viviparous Sponge Ircinia felix

Many marine demosponges contain large amounts of phylogenetically complex yet highly sponge-specific microbial consortia within the mesohyl matrix, but little is known about how these microorganisms are acquired by their hosts. Settlement experiments were performed with the viviparous Caribbean demosponge Ircinia felix to investigate the role of larvae in the vertical transmission of the sponge-associated microbial community. Inspections by electron microscopy revealed large amounts of morphologically diverse microorganisms in the center of I. felix larvae, while the outer rim appeared to be devoid of microorganisms. In juveniles, microorganisms were found between densely packed sponge cells. Denaturing gradient gel electrophoresis (DGGE) was performed to compare the bacterial community profiles of adults, larvae, and juvenile sponges. Adults and larvae were highly similar in DGGE band numbers and banding patterns. Larvae released by the same adult individual contained highly similar DGGE banding patterns, whereas larvae released by different adult individuals showed slightly different DGGE banding patterns. Over 200 bands were excised, sequenced, and phylogenetically analyzed. The bacterial diversity of adult I. felix and its larvae was comparably high, while juveniles showed reduced diversity. In total, 13 vertically transmitted sequence clusters, hereafter termed “IF clusters,” that contained sequences from both the adult sponge and offspring (larvae and/or juveniles) were found. The IF clusters belonged to at least four different eubacterial phyla and one possibly novel eubacterial lineage. In summary, it could be shown that in I. felix, vertical transmission of microorganisms through the larvae is an important mechanism for the establishment of the sponge-microbe association.     

Biological control potentials of insect-parasitic nematode Rhabditis blumi (Nematoda: Rhabditida) for major cruciferous vegetable insect pests

Pathogenicity of Rhabditis blumi Sudhaus against major cruciferous insect pests was evaluated in the lab and greenhouse. In Petri-dish tests against the insects, including Artogeia rapae L., Mamestra brassicae L., and Plutella xylostella L., insect mortality by R. blumi and its associated bacteria was dose and time dependent, which increased with dose (0?C80 dauer juveniles/larva) and time increments. Pathogenicity against fourth-instar larvae was higher than the rate of corresponding third-instar larvae. The highest insect mortality rate was observed in fourth-instar larvae of P. xylostella, followed by A. rapae, and M. brassicae, with mortality rates of 93.5, 88.2, and 77.8?%, respectively. Lethal dose values at 50?% (LD₅₀) of R. blumi were 25.7 dauer juveniles/larva on P. xylostella; 28.0 dauer juveniles/larva on A. rapae; and 40.6 dauer juveniles/larva on M. brassicae, respectively. In greenhouse tests, P. xylostella larvae were most susceptible to nematodes, with insect reduction rate of 88.0?%. The rate varied with vegetable species and persistence time of live nematodes on vegetable leaves after spraying. Nematodes established in cadavers showed positive correlation with nematode dose, whereas nematode persistence on the leaf was inversely related to hours after treatment.     

Pecularities of bony skeleton development in Asian clawed salamanders (Onychodactylus, Hynobiidae) related to embryonization

We studied skull, vertebral column, and limb skeleton development in Japanese clawed salamander Onychodactylus japonicus (Hynobiidae). The study is based on the ontogenetic series of embryos and larvae obtained from wild-captured adults by artificial induction of breeding using hormonal stimulation. The first stages of the skeleton formation in O. japonicus are shifted to the late embryonic period and hatching larvae already possess a well-ossified vertebral column, large number of skull ossifications and show signs of ossification in the forelimb skeleton. Compared to the primitive pattern of the skeleton development typical for other hynobiid salamanders, O. japonicus shows a number of heterochronies related to embryonization. In particular, this species is characterized by an earlier ossification of the vertebral column compared to that of the skull and by the delayed development and early reduction of the coronoid. Our results, along with the previously reported data on the skeleton development in the Fischer’s clawed salamander O. fischeri (Smirnov and Vassilieva, 2002), indicate that the genus Onychodactylus is characterized by the loss or reduction of several skeletal features typically found at early larval stages in other Hynobiidae species. In particular, provisional bones (especially the coronoid) and their dentition are underdeveloped. In addition, it is corroborated that the first tooth generation is absent in Onychodactylus, whereas such monocuspid nonpedicellate tooth generation normally develops at the early larval stages of other caudate amphibians. Since similar patterns of skeleton ontogeny are observed in other caudate groups with different extent of embryonization, it is proposed that, in different lineages of Urodela, the evolution of ontogeny followed similar pathways and was accompanied by the same changes in skeletogenesis.     

Colonization of floating seaweed by pelagic and subtidal benthic animals in southwestern Iceland

Coastal floating seaweed, originating from the intertidal, is colonized by various pelagic and subtidal benthic animals. At southwestern Iceland, common macrofaunal colonizers include the fish Cyclopterus lumpus L., the harpacticoid Parathalestris croni (Krøyer), the amphipods Calliopius laeviusculus (Krøyer), Gammarellus angulosus(Rathke), Dexamine thea Boeck and Ischyrocerus anguipes (Krøyer), and the isopod Idotea baltica Pallas. The colonization patterns of these species were studied by collecting samples from experimental and natural clumps of floating seaweed at approximately monthly intervals for ca. 18 months. The occurrence of colonizers was highly seasonal with maximum numbers between April and September. For most species, numbers were correlated with weight of clumps. The relationship of density (numbers/100 g algae) to weight of clump and distance from shore varied between species. The algal species composition of clumps appeared to influence some colonizers. Only juvenile C. lumpus were found, while all P. croni were sexually mature; juveniles predominated in other species. The different colonization patterns of the species can be explained partly by their biological traits. The clumps are vital for the breeding of P. croni and are used for feeding by C. lumpus fry. Other species possibly colonize floating algae accidentally, being programmed to seek attached vegetation. Floating clumps may, nevertheless, serve to disperse these species.     

The effect of development of Taenia hydatigena larvae in the peritoneal cavity of dogs on resistance to a challenge infection with Echinococcus granulosus

Activated oncospheres of T. hydatigena within filtration membrane diffusion chambers implanted intraperitoneally into dogs developed into larvae 3 mm in dia possessing a scolex anlage without hooks. Exogenous antigens released by developing T. hydatigena larvae failed to stimulate any measurable resistance in the dogs to challenge infection with E. granulosus protoscolices.     

Development of the macronuclear anlage in the ciliate Chilodonella uncinata

The development of the macronuclear anlage in C. uncinata occurs in three steps. During stage I, distinct Feulgen-positive elements are visible in the anlage. Along with the increase in the volume of the anlage, the DNA content of the latter increases from 2 C to about 32 C, indicating four cycles of replication. Simultaneously, the number of Feulgen-positive elements also increases, suggesting that these bodies represent the individual chromosomes and that after each duplication cycle, the daughter chromosomes fall apart. During stage II, the anlage increases greatly in volume and shows a diffused Feulgen stain, in which no structured elements are discernible. During stage III, small Feulgen-positive granules reappear inside the anlage, and gradually become bigger as well as more numerous; at the same time the anlage as a whole starts condensing and becomes more and more densely staining, until it attains the appearance of a vegetative macronucleus about to divide. During stages II and III, the DNA content of the macronuclear anlage goes on increasing, until it nearly reaches the G₂ value of the vegetative macronucleus, which is about 128 C. The problem as to whether there is an elimination of some DNA in between stages I and II has however not yet been resolved and needs further study.     

Patterns of development of the coldwater lacustrine-riverine form of the Drjagin charr (genus <Emphasis Type="Italic">Salvelinus</Emphasis>) from Lake Lama (the Taimyr Peninsula) during the larval period

Reproduction of the lacustrine-riverine form of the Drjagin charr (genus Salvelinus) from Lake Lama (the Noril’sk-Pyasina aquatic system on the Taimyr Peninsula) in a mountain tributary, the Bunisyak River, as well as the formation and development of skeletal elements in embryos and larvae reared under different experimental conditions are described. Patterns of the development and the heterochrony between the rates of somatic growth and osteogenesis are an adaptation to the extremely low water temperature and oligotrophic spawning habitat of the mountain stream. Still, the formation of vertebral centrae is retarded even at rather high rearing temperatures. As compared to larvae of the small normal (nondwarf) planktivorous lacustrine form of Arctic charr from Lake Davatchan (Transbaikalia) reared at 3°C, larvae of Drjagin charr from Lake Lama reared at 1°C are characterized by accelerated growth and heterochronies of osteogenesis. The divergence of the lacustrine-riverine form of Drjagin charr from the generalized form of Salvelinus alpinus in morphology begins during the larval period of the ontogeny.     

Observations on the morphology and infectivity for cattle of Babesia bovis parasites in unfed Boophilus microplus larvae after incubation at various temperatures

Dalgliesh R. J. and Stewart N. P. 1979. Observations on the morphology and infectivity for cattle of Babesia bovis parasites in unfed Boophilus microplus larvae after incubation at various temperatures. International Journal for Parasitology9: 115–120. The temperature of incubation of unfed Boophilus microplus larvae infected with Babesia bovis influenced the morphology and infectivity of the Babesia within the tick. Incubation at 37°C for 1–3 days stimulated the development of parasites morphologically similar to those usually observed in fed larvae harvested from cattle; similar forms appeared more slowly in larvae incubated at 31°C or 25°C. Extracts prepared from larvae after incubation at 37°C for 3–5 days or 30°C for 8 days were consistently infective for cattle. Prior storage of larvae at 14°C for up to 28 days enhanced the development of infectivity at 37°C; infectivity could still be produced after 65 days storage at 14°C but not after 76 days. Larvae released on a host transmitted B. bovis sooner if they had been incubated at 37°C for 4 days. It was concluded that the development of B. bovis to an infective stage in B. microplus is temperature dependent and does not require the stimulus of feeding by the host.