Embryogenesis and larval development of migratory matrinchã Brycon orthotaenia Günther 1864 (Characiformes: Bryconidae)

The present study aimed to characterize the embryogenesis and larval development of matrinchã (Brycon orthotaenia), through the analysis of egg and larval morphology. Fertilized eggs had a mean diameter of 1.17 mm, with yolk occupying most of the egg (1.06 mm). Embryogenesis lasted for 15 hr at an average temperature of 27°C. At hatching, yolk-sac larvae measured 3.67 mm in mean standard length (SL). Pre-flexion, flexion and post-flexion larva had 5.01, 8.24 and 11.88 mm mean SL, respectively, with significant increases observed particularly in head length, head height, and eye diameter. The yolk persisted in the yolk-sac and pre-flexion stages (5.96 mm SL). The mouth opening could first be observed 13 hr after hatching, and cannibalism was observed 29 hr after hatching in pre-flexion larvae after absorption of the yolk sac; in such cases, the larvae had already developed teeth and a complete digestive tract. For an endangered species such as matrinchã, early life history studies are important because they provide researchers with a better understanding of critical stages of development and thus enhance captive management by rearing and restocking of the species.     

Embryogenesis of Heliconius erato (Lepidoptera,Nymphalidae): A contribution to the anatomical development of an evo‐devo model organism

This study reports on the embryogenesis of Heliconius erato phyllis between blastoderm formation and the prehatching larval stage. Syncytial blastoderm formation occurred approximately 2 h after egg laying (AEL) and at about 4 h, the cellular blastoderm was formed. The germ band arose from the entire length of the blastoderm, and rapidly became compacted occupying approximately two‐thirds of the egg length. At about 7 h AEL, protocephalon and protocorm differentiation occurred. Continued proliferation of the germ band was followed by penetration into the yolk mass, forming a C‐shaped embryo at about 10 h. Approximately 12 h AEL, the gnathal, thoracic and abdominal segments became visible. The primordium of the mouthparts and thoracic legs formed as paired evaginations, while the prolegs formed as paired lobes. At about 30 h, the embryo reversed dorsoventrally. Approximately 32 h AEL, the protocephalon and gnathal segments fused, shifting the relative position of the rudimentary appendages in this region. At about 52 h, the embryo was U‐shaped in lateral view and at approximately 56 h, the bristles began evagination from the larval cuticle. Larvae hatched at about 72 h. We found that H. erato phyllis followed an embryonic pattern consistent with long‐germ embryogenesis. Thus, we believe that H. erato phyllis should be classified as a long‐germ lepidopteran. The study of H. erato phyllis embryogenesis provided a structural glimpse into the morphogenetic events that occur in the Heliconius egg period. This study could help future molecular approaches to understanding the evolution of Heliconius development.     

Exogastrulation and interference with the expression of major yolk protein by estrogens administered to sea urchins

Although estrogens have been detected in some echinoderm species, their role is not clearly understood; so we examined the effects of estrogens administered to sea urchin embryos and larvae. A typical malformation was exogastrulation, induced by the exposure to ethynylestradiol (EER) in a defined period of 12 h from 12 h after fertilization (HAF). Morphogenesis for gastrulation was delayed in the treated embryos: protrusion of the archenteron started at 30 HAF when gastrulation had already finished in normal embryos. Exogastrulation induced by EER was cancelled by the antiestrogen chemical, ICI182,780. Feeding larvae were less sensitive to estrogens than those in early embryogenesis and, at certain concentrations, developed without abnormal morphology. The effect of estrogens was examined at the level of gene expression of the major yolk protein (MYP). MYP expression started during the larval stage and was suppressed by estrone at the six-armed stage, but not by β-estradiol, and in later stage larvae, the expression was not affected by treatment with either estrogen. Estrogens affect sea urchins in the early stage of embryogenesis, leading to abnormal morphogenesis and interference with gene expression.     

Embryonic and early development of the Zagros tooth‐carp,Aphanius vladykovi (Actinopterygii: Cyprinodontidae)

The embryonic and early larval development of laboratory reared Zagros tooth‐carp, Aphanius vladykovi Coad, 1988, are described and illustrated. Development and embryogenesis start with the external fertilization of sticky, transparent and spherical telolecithal/macrolecithal eggs with a mean diameter of 1.61± 0.12 mm and it continues with meroblastic/radial cleavage, blastulation/blastula formation, epibolic cell migration during gastrulation and organogenesis resulting in a newly hatched larvae of 5.23 ± 0.09 mm in length with attached yolk sac at about 164 hr (at 24 ± 1°C) after fertilization.     

Growth and morphological development of laboratory-reared larval and juvenile three-spot gourami <Emphasis Type="Italic">Trichogaster trichopterus</Emphasis>

Morphological development, including the body proportions, fins, pigmentation and labyrinth organ, in laboratory-hatched larval and juvenile three-spot gourami Trichogaster trichopterus was described. In addition, some wild larval and juvenile specimens were observed for comparison. Body lengths of larvae and juveniles were 2.5 ± 0.1 mm just after hatching (day 0) and 9.2 ± 1.4 mm on day 22, reaching 20.4 ± 5.0 mm on day 40. Aggregate fin ray numbers attained their full complements in juveniles >11.9 mm BL. Preflexion larvae started feeding on day 3 following upper and lower jaw formation, the yolk being completely absorbed by day 11. Subsequently, oblong conical teeth appeared in postflexion larvae >6.4 mm BL (day 13). Melanophores on the body increased with growth, and a large spot started forming at the caudal margin of the body in flexion postlarvae >6.7 mm BL, followed by a second large spot positioned posteriorly on the midline in postflexion larvae >8.6 mm BL. The labyrinth organ differentiated in postflexion larvae >7.9 mm BL (day 19). For eye diameter and the first soft fin ray of pelvic fin length, the proportions in laboratory-reared specimens were smaller than those in wild specimens in 18.5–24.5 mm BL. The pigmentation pattern of laboratory-reared fish did not distinctively differ from that in the wild ones. Comparisons with larval and juvenile morphology of a congener T. pectoralis revealed several distinct differences, particularly in the numbers of myomeres, pigmentations and the proportional length of the first soft fin ray of the pelvic fin.     

Small-scale patterns in distribution and feeding of Atlantic mackerel (Scomber scombrus L.) larvae in the Celtic Sea with special regard to intra-cohort cannibalism

Short-term variability in vertical distribution and feeding of Atlantic mackerel (Scomber scombrus L.) larvae was investigated while tracking a larval patch over a 48-h period. The patch was repeatedly sampled and a total of 12,462 mackerel larvae were caught within the upper 100 m of the water column. Physical parameters were monitored at the same time. Larval length distribution showed a mode in the 3.0 mm standard length (SL) class (mean abundance of 3.0 mm larvae =75.34 per 100 m³, s=34.37). Highest densities occurred at 20–40 m depth. Larvae <5.0 mm SL were highly aggregated above the thermocline, while larvae ≥5.0 mm SL were more dispersed and tended to migrate below the thermocline. Gut contents of 1,177 mackerel larvae (2.9–9.7 mm SL) were analyzed. Feeding incidence, mean number (numerical intensity) and mean dry weight (weight-based intensity) of prey items per larval gut were significantly dependent on larval size. However, while weight-based feeding intensities continued to increase with larval length, numerical intensity peaked at 4–4.9 mm SL, indicating a shift in the larval diet. While first-feeding larvae relied most heavily on copepod nauplii and eggs, larvae ≥5.0 mm SL initiated piscivorous feeding. All identifiable fish larvae were Atlantic mackerel. Thus, the piscivory was cannibalism. Larval feeding incidence and numerical feeding intensities peaked during daytime and were reduced at night. Daily ration estimates for first-feeding mackerel larvae <4.0 mm SL were extremely low = 1.43% body dry weight, but increased dramatically at 5.0 mm SL, i.e., at the onset of cannibalism, reaching >50% body dry weight in larva ≥8.0 mm SL. Received in revised form: 31 October 2000 Electronic Publication     

Growth and morphological development of laboratory-reared larval and juvenile Pangasianodon hypophthalmus

The morphological development, including the fins, body proportions and pigmentation, of laboratory-reared larval and juvenile Pangasianodon hypophthalmus was described and their behavioral features were observed under rearing conditions. Body lengths (BL) of larvae and juveniles were 3.0 ± 0.2 (mean ± SD) mm just after hatching, and 12.9 ± 1.1 mm on day 13, reaching 23.4 ± 1.8 mm on day 25 after hatching. Aggregate fin ray numbers (for caudal fin, principal soft ray number) attained their full complements in specimens larger than 12.8 mm BL. Notochord flexion began in yolksac larvae on day 0 (10.5 h after hatching), with teeth buds and barbels appearing with jaw formation in yolksac flexion larvae on day 1. Melanophores on the body increased with growth, with a broad vertical band forming on the lateral line and an oblique band extending from above the pectoral fin base towards the forepart of the anal fin during the postflexion larval and juvenile stages. Body proportions became relatively constant in juveniles, except for maxillary barbel length (MBL), which continued to decrease. Yolksac flexion larvae started feeding on day 2 with the onset of intense cannibalism. Yolks were completely absorbed by day 3, and cannibalism ended by day 6. Subsequently, fish displayed a schooling behavior with growth, preferring relatively dark areas during the juvenile stage.     

Maternal effects,flight versus fecundity trade-offs,and offspring immune defence in the Speckled Wood butterfly, <Emphasis Type="Italic">Pararge aegeria</Emphasis>

Background  

Maternal condition can generate resource-related maternal effects through differential egg provisioning, and can greatly affect offspring performance. In the present study, the speckled wood butterfly Pararge aegeria (L.) was used to investigate whether (after controlling for egg size) maternal age, and increased flight during the oviposition period, resulted in changes in egg provisioning and whether this contributed to variation in offspring performance, i) early in development (egg stage and early post-hatching development), and ii) later in larval development after being exposed to the model viral pathogen system; the baculovirus Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV).     

Early life history of mebaru,sebastes inermis (scorpaenidae), in sendai bay, japan

The early life history of the viviparous scorpaenid,Sebastes inermis, in Sendai Bay, Japan, was studied and early development described. Newborn preflexion larvae ofS. inermis were about 5.2 mm BL. Notochord flexion occurred at 5.4–8.0 mm BL and transformation at 14–20 mm BL. Preflexion and flexion larvae ofS. inermis were distinguished from similar larvae by the pigmentation pattern along the dorsal and ventral midlines of the tail. Pigmentation inS. inermis was light throughout the larval and early juvenile periods. Planktonic larvae were particularly abundant in coastal waters of Sendai Bay but not offshore. Vertical and horizontal larval sampling indicated that early larvae occupied near surface waters and horizontal larval sampling indicated that early larvae shift to a benthic habitat occurred at about 12 mm BL, at the end of the postflexion larval period.Sebastes inermis do not have a distinct pelagic juvenile stage, unlike many North Pacific species ofSebastes.     

Embryonic development of the threatened freshwater pipefish Microphis deocata (Hamilton, 1822)

The present study provides the first comprehensive embryonic development of the freshwater Syngnathid fish species, Microphis deocata (Hamilton), a Near Threatened pipefish endemic to the Brahmaputra River drainage in Northeast India and Bangladesh. Microphis deocata is a Gastrophori species as the males develop an abdominal brood pouch. Mature individuals were collected and maintained in well-aerated aquaria under controlled conditions to induce natural spawning. The number of eggs within the males' brood pouch ranged from 17 to 22 (for n = 10), measuring 0.7–1.0 mm in diameter. A total of 10 developmental stages could be recognized under four developmental periods namely, early embryogenesis, eye development, snout formation and juvenile. However, sensitivity, and therefore mortality, while handling of this species restricted the study from reporting the exact time intervals for stages following the blastodisc formation ~48 hr post fertilization. A newborn larvae measures ~14 mm and is free-swimming with distinct dorsal fin (with 31–32 rays) and a sector-shaped caudal fin (with 8–9 rays). The study aims to provide baseline information on the embryology of M. deocata in culture condition which will be helpful for future studies on conservation biology, population status and management of this species.     

Seasonal growth differences of larval Hyporhamphus picarti (Hemiramphidae) in the Sine Saloum estuary,Senegal

The African halfbeak Hyporhamphus picarti (Hemiramphidae) is one of the most abundant species within the ichthyoplankton community of the Sine Saloum estuary (Senegal). A year‐round occurrence of larvae suggests that the Sine Saloum is an important spawning habitat for this species. Annual fluctuations in water temperature, however, can have severe impacts on the survival probabilities of marine fish larvae. To determine whether temperature has an effect on the growth of H. picarti during its larval development, larval age at length and somatic growth rates were investigated for two contrasting spawning seasons in 2014: February (cold season, 20.8°C) and June (warm season, 26.4°C). In both months H. picarti larvae were sampled at the mouth of the Saloum River using neuston nets. Sagittal otoliths’ increments were counted to estimate the larva age at a given standard length (SL). The age of larvae ranged between 2 and 22 days, with SL of 3.86–21.68 mm, respectively. In order to describe larval age at length during the contrasting spawning seasons, two distinctive Gompertz functions were applied. Accordingly, specimens sampled in June (0.94 ± 0.17 mm per day) exhibited significantly higher somatic growth rates than those sampled in February (0.60 ± 0.06 mm per day). These findings suggest that water temperature is an important factor influencing larval growth in H. picarti. Information concerning the early life stages of H. picarti are scarce and the results of the present study may contribute to a better understanding of the species’ biology and ecology.     

Growth and morphological development of laboratory-reared larval and juvenile snakeskin gourami Trichogaster pectoralis

Morphological development, including that of fins, labyrinth organ, body proportions, and pigmentation, in laboratory-hatched larval and juvenile snakeskin gourami Trichogaster pectoralis is described. Body lengths (BL; mean ± SD) of larvae and juveniles were 2.3 ± 0.1 mm just after hatching (day 0) and 8.2 ± 0.6 mm on day 22, reaching 14.1 ± 2.3 mm on day 48. Aggregate fin ray numbers attained their full complements in juveniles >11.8 mm BL. Preflexion larvae started feeding on day 2 following upper and lower jaw formation, the yolk being completely absorbed by day 12. Subsequently, oblong conical teeth appeared in postflexion larvae >8.2 mm BL (day 16). Melanophores on the body increased with growth, with a large dark spot developing on the lateral midline at the caudal margin of the body in flexion larvae >6.1 mm BL. Subsequently, a broad vertical dark band from the eye to the caudal peduncle developed in postflexion larvae >8.9 mm BL. Proportions of head and pre-anal lengths became constant in postflexion larvae greater than ca. 9–10 mm BL, whereas those of maximum body depth, eye diameter, and snout length failed to stabilize in fish of the size examined in this study. First soft fin ray of the pelvic fin elongated, reaching over 40% BL. The labyrinth organ differentiated in postflexion larvae >7.4 mm BL (day 22). Comparisons of larval and juvenile morphology with another anabantoid species Anabas testudineus were also made, revealing several distinct differences, particularly in the numbers of myomeres and fin rays in the dorsal/anal fins, mouth location and body shape.     

Early development and neurogenesis of Temnopleurus reevesii

Sea urchins are model non‐chordate deuterostomes, and studying the nervous system of their embryos can aid in the understanding of the universal mechanisms of neurogenesis. However, despite the long history of sea urchin embryology research, the molecular mechanisms of their neurogenesis have not been well investigated, in part because neurons appear relatively late during embryogenesis. In this study, we used the species Temnopleurus reevesii as a new sea urchin model and investigated the detail of its development and neurogenesis during early embryogenesis. We found that the embryos of T. reevesii were tolerant of high temperatures and could be cultured successfully at 15–30°C during early embryogenesis. At 30°C, the embryos developed rapidly enough that the neurons appeared at just after 24 h. This is faster than the development of other model urchins, such as Hemicentrotus pulcherrimus or Strongylocentrotus purpuratus. In addition, the body of the embryo was highly transparent, allowing the details of the neural network to be easily captured by ordinary epifluorescent and confocal microscopy without any additional treatments. Because of its rapid development and high transparency during embryogenesis, T. reevesii may be a suitable sea urchin model for studying neurogenesis. Moreover, the males and females are easily distinguishable, and the style of early cleavages is intriguingly unusual, suggesting that this sea urchin might be a good candidate for addressing not only neurology but also cell and developmental biology.     

First report on the spawning migration and early life development of a cyprinid species of the genus Telestes

Reproductive migration of a Telestes species is reported for the first time for the Balkan endemic Telestes pleurobipunctatus (Stephanidis, 1939) from Louros River (Northwestern Greece), while the embryonic and larval development is also described for the first time for this species and genus. Adult fish migrate in late winter upstream and spawn in a peak of 2–3 nights in the outflow of springs. Embryos at hatching measure approx. 6.0 mm notochord length (NL), flexion starts at 8.1 mm NL and food particles are noted in the digestive tract of larvae at 8.2 mm NL. The larval period is characterized by the sequential formation of fins and the development of scalation. Fin differentiation ends with the completion of pelvic fin rays and the disappearance of the pre-anal finfold at 20.0 mm. First scales appear at 17.0 mm standard length (SL) and scalation completes at 27.8 mm SL. We propose that the size at a specific ontogenetic event, the pigmentation pattern and the pre-anal myomeres' number comprise diagnostic characters that permit distinguishing T. pleurobipunctatus larvae from other sympatric cyprinids. We note the rare pattern of scale scalation and pigmentation pattern of the target species. Parapatric speciation in T. pleurobipunctatus possibly related to its spawning migration pattern, as well as the use of larval identification in monitoring and conservation programmes targeting threatened cyprinids exhibiting this type of reproductive behaviour are also discussed.     

Follicle population, cumulus mucification, and oocyte chromatin configuration during the periovulatory period in the female dog

This study was designed to describe the follicular population present on the canine ovary (Canis familiaris) during the preovulatory period and essentially the changes in oocyte size, mucification, and chromatin configuration occurring from before the luteinizing hormone (LH) surge up to postovulation. In a first experiment, ovaries of beagle bitches were collected before (n = 21) or after LH surge but before ovulation (post-LH surge/preovulation stage, n = 24) as determined using hormone (LH, estradiol, progesterone) assays and ultrasonography. All large (>2 mm) follicles were measured and punctured. The numbers of oocytes collected per follicle and the degree of cumulus mucification were recorded. In a second experiment, ovaries were similarly collected before (n = 13) and after the LH surge but before ovulation (n = 11) as well as after ovulation as determined by ultrasonography (n = 9). Chromatin configuration of the oocytes was observed by DNA staining and confocal microscopy. In Experiment 1, before the LH peak, an average of 13.5 ± 0.7 follicles per bitch (total 284 follicles) were detected, and the maximal follicle diameter reached 6.5 mm. Large follicles were observed already in this period of the cycle and as early as when progesterone was still below 0.5 ng/mL. After the LH peak but before ovulation, 11.0 ± 0.7 follicles were present (total 264 follicles). Fully mucified cumulus cells were observed only in follicles larger than 4 mm. Multi-oocytic follicles represented 7% (before LH peak) and 4% (after LH peak) of the follicular population. In Experiment 2, all the oocytes were at the germinal vesicle (GV) stage, but three chromatin configurations could be distinguished: diffuse, partly grouped, and fully grouped chromatin. The proportion of oocytes with fully grouped chromatin increased with the follicular diameter and the time in estrus, the maximum being observed after the LH peak. These results suggest that (1) before LH peak, follicles are already of large diameter, similar to the ones at ovulation; (2) the ability for cumulus mucification is acquired during the late steps of follicular growth; (3) three GV patterns may be observed during the periovulatory period.     

Molecular cloning and expression of bovine nucleoplasmin 2 (NPM2): a maternal effect gene regulated by miR-181a

Background  

Nucleoplasmin 2 (NPM2) is an oocyte-specific nuclear protein essential for nuclear and nucleolar organization and early embryonic development. The aims of this study were to clone the bovine NPM2 gene, determine its temporal expression during oocyte development and early embryogenesis, and evaluate the potential role of miRNA-181a in regulation of its expression.     

Allometric growth and larval development in Pacific red snapper Lutjanus peru under culture conditions

Allometric growth is a common feature during fish larval development. It has been proposed as a growth strategy to prioritize the development of body segments related to primordial functions like feeding and swimming to increase the probability of survival during this critical period. In the present study we evaluated the allometric growth patterns of body segments associated to swimming and feeding during the larval stages of Pacific red snapper Lutjanus peru. The larvae were kept under intensive culture conditions and sampled every day from hatching until day 33 after hatching. Each larva was classified according to its developmental stage into yolk-sac larva, preflexion larva, flexion larva or postflexion larva, measured and the allometric growth coefficient of different body segments was evaluated using the potential model. Based on the results we can infer the presence of different ontogenetic priorities during the first developmental stages associated with vital functions like swimming during the yolk-sac stage [total length (TL) interval = 2.27–3.005 mm] and feeding during the preflexion stage (TL interval = 3.007–5.60 mm) by promoting the accelerated growth of tail (post anal) and head, respectively. In the flexion stage (TL interval = 5.61–7.62 mm) a change in growth coefficients of most body segments compared to the previous stage was detected, suggesting a shift in growth priorities. Finally, in the postflexion stage (TL interval = 7.60–15.48 mm) a clear tendency to isometry in most body segments was observed, suggesting that growth priorities have been fulfilled and the larvae will initiate with the transformation into a juvenile. These results provide a framework of the larval growth of L. peru in culture conditions which can be useful for comparative studies with other species or in aquaculture to evaluate the changes in larval growth due to new conditions or feeding protocols.     

Newly developed fungal diet for artificial rearing of the endangered long‐horned beetle Callipogon relictus (Coleoptera: Cerambycidae)

In this study, we attempted to develop an artificial diet to effectively rear the endangered long‐horned beetle Callipogon relictus Semenov to facilitate restoration efforts for this species. Fungal mycelia of the white‐rot fungus Pleurotus florida (Eager) were, for the first time, provided as an artificial diet for the larvae of C. relictus. The experiment started on August 11, 2015 with 53 larvae being provisioned with the fungal diet under laboratory conditions (25°C, 60 % RH, L:D 0:24) without diapause. During the first year, 11 adults (4 males and 7 females, 20.8 % of the 53 larvae) emerged between September 10 and October 1, 2016. The body length of the largest male was 106.8 mm, and three of the four males exceeded 100 mm in length. These results show that a fungal diet for rearing C. relictus is useful not only for reducing the larval period to approximately 1/6 of the normal larval period in nature, but also for producing large adults. These results support the notion that fungus may provide nutritional benefits during the larval development of C. relictus, and also indicate that this species is fungivorous.