Region Of Larvae Research Articles

Dynamics of the Gut Bacteriome During a Laboratory Adaptation Process of the Mediterranean Fruit Fly, Ceratitis capitata.

Laboratory adaptation process used in sterile insect technique (SIT) programs can exert a significant impact on the insect-gut microbiome relationship, which may negatively impact the quality and performance of the fly. In the present study, changes in the gut microbiota that occur through laboratory adaptation of two Ceratitis capitata populations were investigated: Vienna 8 genetic sexing strain (GSS), a long-established control line, and a wild population recently introduced to laboratory conditions. The bacterial profiles were studied for both strains using amplicon sequencing of the 16S rRNA V3-V4 hypervariable region in larvae and in the gastrointestinal tract of teneral (1 day) and adults (5 and 15 days) reared under laboratory conditions for 14 generations (F0–F13). Findings demonstrated the development of distinct bacterial communities across the generations with differences in the bacterial composition, suggesting a strong impact of laboratory adaptation on the fly bacteriome. Moreover, different bacterial profiles were observed between wild and Vienna 8 FD-GSS displaying different patterns between the developmental stages. Proteobacteria, mainly members of the Enterobacteriaceae family, represented the major component of the bacterial community followed by Firmicutes (mainly in Vienna 8 FD-GSS adults) and Chlamydiae. The distribution of these communities is dynamic across the generations and seems to be strain- and age-specific. In the Vienna 8 FD-GSS population, Providencia exhibited high relative abundance in the first three generations and decreased significantly later, while Klebsiella was relatively stable. In the wild population, Klebsiella was dominant across most of the generations, indicating that the wild population was more resistant to artificial rearing conditions compared with the Vienna 8 FD-GSS colony. Analysis of the core bacteriome revealed the presence of nine shared taxa between most of the examined medfly samples including Klebsiella, Providencia, Pantoea, and Pseudomonas. In addition, the operational taxonomic unit co-occurrence and mutual exclusion networks of the wild population indicated that most of the interactions were classified as co-presence, while in the Vienna 8 FD-GSS population, the number of mutual exclusions and co-presence interactions was equally distributed. Obtained results provided a thorough study of the dynamics of gut-associated bacteria during the laboratory adaptation of different Ceratitis capitata populations, serving as guidance for the design of colonization protocols, improving the effectiveness of artificial rearing and the SIT application.

Genetic connectivity between Atlantic bluefin tuna larvae spawned in the Gulf of Mexico and in the Mediterranean Sea.

The highly migratory Atlantic bluefin tuna (ABFT) is currently managed as two distinct stocks, in accordance with natal homing behavior and population structuring despite the absence of barriers to gene flow. Larval fish are valuable biological material for tuna molecular ecology. However, they have hardly been used to decipher the ABFT population structure, although providing the genetic signal from successful breeders. For the first time, cooperative field collection of tuna larvae during 2014 in the main spawning area for each stock, the Gulf of Mexico (GOM) and the Mediterranean Sea (MED), enabled us to assess the ABFT genetic structure in a precise temporal and spatial frame exclusively through larvae. Partitioning of genetic diversity at nuclear microsatellite loci and in the mitochondrial control region in larvae spawned contemporarily resulted in low significant fixation indices supporting connectivity between spawners in the main reproduction area for each population. No structuring was detected within the GOM after segregating nuclear diversity in larvae spawned in two hydrographically distinct regions, the eastern GOM (eGOM) and the western GOM (wGOM), with the larvae from eGOM being more similar to those collected in the MED than the larvae from wGOM. We performed clustering of genetically characterized ABFT larvae through Bayesian analysis and by Discriminant Analysis of Principal Components (DAPC) supporting the existence of favorable areas for mixing of ABFT spawners from Western and Eastern stocks, leading to gene flow and apparent connectivity between weakly structured populations. Our findings suggest that the eastern GOM is more prone for the mixing of breeders from the two ABFT populations. Conservation of this valuable resource exploited for centuries calls for intensification of tuna ichthyoplankton research and standardization of genetic tools for monitoring population dynamics.

Peroxisome proliferator-activated receptor alpha is involved in the temperature-induced sex differentiation of a vertebrate

Medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system, similar to that of mammals. However, under high temperature conditions, XX medaka is masculinised by elevation of cortisol, the major teleost glucocorticoid. In this study, to identify novel factors in the gonads acting downstream from cortisol during sexual differentiation, we performed RNA sequencing (RNA-seq) analysis using the gonadal regions of larvae reared at normal temperature with and without cortisol, and at high temperature. The RNA-seq and real-time PCR analyses showed that expression of some peroxisome proliferator-activated receptor α (PPARα) signalling-targeted genes was increased by cortisol. PPARα agonist treatment induced masculinisation of XX medaka in some cases, and co-treatment of the agonist with cortisol further induced masculinisation, whereas treatment of pparaa knockout medaka with cortisol or the agonist did not induce masculinisation. This study provides the first evidence that PPARα is involved in environmental sex determination in vertebrates.

Temperature and salinity influence the chemistry in the pre-hatch otolith region of capelin, Mallotus villosus, during lab and field egg incubation experiments

Identifying the natal origin of marine fish is important to understand connectivity and productivity among populations residing in different habitats. Capelin, Mallotus villosus, is a key marine forage fish species that spawns at both beach (warmer, less saline) and deep-water (15–40 m; cooler, more saline) habitats along the northeast Newfoundland coast. Currently, the contribution from each habitat to the spawning population is unknown. Previous research, where capelin eggs from known families were lab-reared, identified family-based otolith chemical signatures in the pre-hatch (embryonic) region of larvae. In this study, we investigated whether temperature and salinity influenced embryonic otolith chemistry to determine whether variation in environmental conditions would result in habitat-specific signatures, thereby overwhelming family-based signatures and allowing the identification of natal origin. Capelin eggs from many families were incubated together under controlled temperature (4, 8, 10 °C) and salinity (10, 20, 30 psu) treatments in the lab and uncontrolled conditions within each habitat in the field. Elemental concentrations (i.e., Sr, Ba, Mg, Mn) in the pre-hatch region of 1-day old larvae were quantified via LA ICP-MS. Elemental concentrations varied among individuals reared under identical conditions, likely due to family-based chemical signatures. Despite this variation, mean elemental concentrations differed when mean temperatures varied by ≥4 °C between treatments (lab) and rearing habitats (field), resulting in high treatment- and habitat-specific classification success (~73–88%) of individuals. In contrast, embryonic otolith chemistry did not vary consistently with salinity. Temperature differs consistently between rearing habitats and, thus, these findings suggest that when capelin rearing habitats differ by ≥4 °C within a year, chemical signatures in the embryonic otolith may be used to determine the natal origin of individuals.

The scanning electron microscopic study of the infection and conidial development of Aspergillus tamarii Kita on its host, the silkworm, Bombyx mori Linn.

AbstractDevelopment of Aspergillosis on the integument of the silkworm, Bombyx mori Linn., was examined by scanning electron microscopy. Aspergillosis is a fungal disease caused by an insect mycopathogen Aspergillus tamarii Kita, which infects the silkworms in countries where sericulture (the rearing of silkworms)is prevalent. The present study showed the course of infection and the conidial development of A. tamarii on the integument of B. mori. Five different strains (KA, NB18, NB4 D2, NB7 and PM) of B. mori were inoculated on their body surface with ca. 1 × 106 conidia/ml. Among the five breeds tested, the conidial germination was greatest on the larval surface of KA breed, and least on PM. Most of the conidia germinated on the cuticle approximately 8–12 hours after inoculation, forming a suctorial appressorium within 24 hours. The hyphae reached the hemocoel, where they grew and multiplied extensively, forming a mycelial complex and causing death of the host larva in about 5–6 days. The death of the host was followed by growth of the fungus through mesodermal and epidermal tissues, leading to larval mummification about 6–7 days post-inoculation. Extensive aerial outgrowths of the fungus followed, mostly through the intersegmental regions of larvae. Abundant branched conidiophores developed, forming a confluent yellow brown mat over the entire host body 7 days after inoculation. Each conidiophore had an apical vesicle bearing numerous phialides from which conidia were developed in long chains.

The route of tomato spotted wilt virus inside the thrips body in relation to transmission efficiency.

The route of tomato spotted wilt virus (TSWV) in the body of its vectors, Frankliniella occidentalis and Thrips tabaci (Thysanoptera: Thripidae) was studied during their development. First instar larvae were allowed, immediately upon hatching, to acquire virus from mechanically infected Datura stramonium plants for 24 h. The rate of transmission by adults was determined in inoculation access feeding test on Emilia sonchifolia leaf disks. Thrips tissues were analysed for infection at 24 h intervals after the acquisition-access feeding period, and assayed by the whole-mount immuno-fluorescent staining technique. The virus was initially detected in the proximal midgut region in larvae of both species, and then in the second and third midgut regions, foregut, and salivary glands. Occasionally the first infections of the salivary glands were already detected in one-day-old second stage larvae. The intensity of the infection in the various organs of the thrips of each species was positively related to the transmission efficiency. In both thrips populations good agreement was found between the percentage of second instar larvae and adults with at least one infected salivary gland lobe and the percentage of transmitting adults. These results support the contention that the virus must reach the salivary glands before thrips pupation in order to be transmitted by old second instar larvae and adults.

Corresponding defects in the dorsal fin and in the male breeding crest ofTriturus alpestris.

In a wild population ofTriturus alpestris several adult males with an incomplete breeding crest were found. Among the offspring from this population larvae with defects in the dorsal fin were observed. Neither the pigment cells nor the spinal ganglia appear affected in the deficient trunk region of larvae and adults.

Reconstitution of the spinal cord following ablation in urodele larvae.

AbstractAfter ablation of 2 mm of spinal cord in the postbrachial region in larvae of Ambystoma maculatum studies were made on the reconstitution of the cord and the return of function posterior to the ablation level.Healing of the cord at anterior and posterior transection surfaces involves migration of ependymal cells to close the open central canal and movement of cells of the gray matter over the cut surface. Dilation of the central canal occurs at each transection level to form a terminal vesicle. Its wall is made up of ependyma, cells from the gray matter and an outer layer of white matter. Anterior and posterior terminal vesicles gradually increase in length bringing about a slow advance of their tips across the ablation gap, the anterior vesicle moving more rapidly than the posterior.Nerve fibers growing out from the white matter of each terminal vesicle extend across the ablation gap and eventually join the wall of the opposite vesicle. Thus are formed bridges of intracentral fibers between anterior and posterior vesicles. Broad nerve fiber bridges become the white matter of the reconstituted spinal cord. Continued advance of the terminal vesicles across the ablation region results finally in the union of the two vesicles, restoring the continuity of the spinal cord.Recovery of the use of hind limbs for walking and of trunk and tail muscles for swimming is correlated with the extent to which nerve fiber bridges have been established, but does not involve a complete fusion of terminal vesicles. All larvae which walked normally and the majority of those which swam normally possessed fiber bridges with an average diameter of at least 0.05 mm.

Laser Effects on Two Insects

AbstractDermestid larvae, Trogoderma versicolor (Creutzer), and adult American cockroaches, Periplaneta americana (Linné), were affected by ruby laser pulses of two intensities, 0.06 ± 0.04 per 10−7 second duration and 0.57 ± 0.06 joules per 0.2 milliseconds. Laser impact areas were 1.5 mm. in diameter. The first intensity, directed at cephalic regions of dermestid larvae, caused mortality in 3–48 hours. The same intensity directed at larval mid-abdominal areas caused visible outer integument and body-hair scorching, cessation of feeding, growth rate, and movement, and loss of negative phototactic responses. Directed at posterior abdominal regions of larvae, it caused damage to the epidermal layer noticeable in four succeeding moults. It caused temporary (10-15 min.) immobility and loss of negative phototaxis when directed at pro-thoracic regions of cockroach adults. P. americana adults were more severely affected by the second laser treatment, exhibiting immobility, loss of negative phototaxis, and cessation of eating. Total mortality in the five treated specimens occurred in 8-14 days as compared with 45-68 days in controls.