Embryonic development in Clarias gariepinus under laboratory conditions

The embryonic development in Clarias gariepinus was studied under laboratory conditions. The developmental stages of eggs starting from first cleavage were examined microscopically. Photomicroscope was used to take important stages of segmentation, blastulation, differentiation of embryo and hatching. The films of the photograph were developed and printed for each stage produced. The accurate timing and detailed description of each stage was done. The results show that the blastodisc (Polar cap) appeared about 35 minutes after fertilization and the first cleavage dividing the blastodisc into two blastomeres occurs 15 minutes after polar cap formation. Details of the developmental stages of embryos and the timing from one stage to the other were described. The larva shook off the shell and emerged completely from the egg case about 22 hours after fertilization at a water temperature of 25.1 degree C. The accurate determination of the time of initiation of first mitosis is of great importance in fish culture and breeding especially in the production of tetraploids

Observations on the influence of external factors on the duration of the embryonic development and on the molting rhythm of Cyclops vicinus. [Translation from: Oecologia 7, 342-355, 1971.]

Investigations on the control of the embryonic and post-embryonic development of arthropods have formed an intensively studied field of zoological research for a long time, Here in especially favourable cases the causal chain from the operation of external factors on the influence of physiological mechanisms, eg. of the hormone variety, is known right through to its primary influences. A comparative approach to the relevant questions was in the main only made in the case of the insects. For crustacea , investigations are available almost exclusively only for the malacostraca. This study examines the influence of the factors of temperature and photoperiod on the entire development of Cyclops vicinus. Tests were made on whether the light-darkness change serves as a regulator for a possible existing molting rhythm - a question which for the entire arthropods has been settled only very rarely. The basic material for the cultures that were examined originates from Lake Constance.

Respiration and the efficiency of energy during embryonic development of Asellus aquaticus L. (Crustacea) [Translation from: Vestsi Akademii Navuk Belorusskoi SSR, Seriya Biyal. 1978(5) 112-114, 1978]

Experimental studies were carried out on the transformation of matter and energy during embryonic development of the isopod Crustacea Asellus aquaticus L. under two constant temperatures. Material for the experiments was collected in the quarry lakes of the Kurasovshchin-zone (city-Minsk) at 9°C in April and at 18°C in June, 1977. The rate of consumption of oxygen per specimen by eggs and embryos of Asellus aquaticus was observed and dynamics of the basic biological characteristics during embryonic development studied.

Description of embryonic development of Atka mackerel (Pleurogrammus monopterygius)

Atka mackerel (Pleurogrammus monopterygius) is hexagrammid fish that inhabits the temperate and subarctic North Pacific Ocean and neighboring seas (Fig. 1). This highly abundant fish is a critically important prey species (Sinclair and Zeppelin, 2002; Zenger, 2004) that supports a directed commercial trawl fishery (Lowe et al., 2006). Atka mackerel is a demersal spawner and males provide parental care to eggs (Zolotov, 1993). During breeding periods, sexually mature males aggregate on the bottom at nesting sites where they establish territories (Lauth et al., in press). Sexually mature females periodically visit male nesting territories from July to October to spawn batches of demersal egg masses (McDermott and Lowe, 1997; McDermott et al., 2007). Individual nests may consist of multiple egg masses deposited by different females, and males defend nesting territories for a protracted period lasting from the time territories are being established until all eggs within the territory are completely hatched (Lauth et al., 2007). Knowledge about the timing of the reproductive cycle and the use of spawning habitat are important for understanding population structure and the dynamics of stock recruitment, which in turn are important factors in the management of Atka mackerel populations.

A comparative study on the embryonic development of gynogen, triploid, haploid and normal diploid embryos of stinging catfish, Heteropneustes fossilis

UV irradiation and cold shock were applied on the eggs of stinging catfish, Heteropneustes fossilis, to produce haploid,. gynogen and triploid embryos. A comparative account of the various features· of embryonic development in chromosomally manipulated groups viz. haploid, gynogen and triploid and non-manipulated normal diploid group of H fossilis has been discussed. A slow development and delayed hatching were observed in gynogen and triploid embryos compared to those in normal diploid (control) groups. Mass mortality was observed in all chromosomally manipulated groups particularly during the gastrulation stage. The hatchlings of the gynogen, triploid and normal diploid were similar in overall appearance.

Captive breeding and embryonic development of honey gourami, Colisa sota (Ham.-Buch.)

Honey Gourami, Colisa sota, has high ornamental as well as food value. The natural resources of this species are gradually declining, due to destruction of its habitat, over fishing for aquarium trade and human consumption. The fish was bred in captivity under controlled environment. It laid about 200-400 eggs in bubble nest built by the male. Hatching started within 28-30hrs. after egg laying. The hatchlings became free swimming by 3rd to 4th day of hatching. The male showed territoriality and parental care by guarding the eggs and hatchlings. The larval survival was 30-35%. The breeding behavior, embryonic and post embryonic development of the fish were studied.

Induced breeding, embryonic and larval development in Heteropneustes fossilis (Bloch) in the agro-climatic conditions of Maharashtra

Heteropneustes fossilis was induced bred for the first time in the agro-climatic conditions of Maharashtra, India. The embryonic development was completed within 16-18h after fertilisation. Head and tail ends were distinguishable after 3h and 11-12 somites were visible after 6-7h. The eggs started hatching after 14h of incubation. Average hatching time was 16-18h at 26 degrees C. In first day old pro-larva, notochord was deflected upwards, eyes were darkly pigmented and alimentary canal appeared. In fourth day old post-larva intestinal coiling could be seen and yolk was absorbed. Aerial respiration started by 8th day. The 10 day old post-larva was free swimming and fed voraciously attaining a length of 20 mm in 30 days.

Fecundity, morphometry post embryonic growth and development of Caridina simoni Bouvier (Decapoda: Atyidae)

The fecundity, morphometry and the post embryonic development of Caridina simoni which is the commonest atyid shrimp in Sri Lanka were studied. The fecundity values ranged from 12-55. There was a linear relationship between the logarithmic values of fecundity and body length and the same relationship was obtained for body length and weight. It was seen that the developmental period of this species was less than six days and during development it passed through six zoeal stages.

Sexual Reproduction and Early Development in the Estuarine Sea Anemone, Nematostella vectensis Stephenson, 1935

This dissertation: 1) determines the factor(s) responsible for spawning induction in NematosteJla vectensis; 2) isolates, describes, and documents the source of jelly from egg masses of N. vectensis; and 3) describes N. vectensis' early development. Namatostella vectensis were maintained on a 7-day mussel feeding/water change regime over 159 days. Within 36 hours of mussel feeding/water change. 69.1% of females and 78.5% of males spawned reliably. Through manipulation of feeding, water change, oxygen and nitrogenous waste concentrations, spawning induction was found to be triggered by the oxygen concentration associated with water change, and not by feeding. Ammonia, anemones' major waste product, inhibited this induction in a concentration-dependent manner. Female N. vectensis release eggs in a persistent jellied egg mass which is unique among the Actiniaria. The major component of this egg mass jelly was a positive periodic acid-Schiffs staining, 39.5-40.5 kD glycoprotein. Antibodies developed in rabbits against this glycoprotein bound to jelly of intact egg masses and to granules (~ 2.8 IJm in diameter) present in female anemone mesenteries and their associated filaments. Antibodies did not label male tissues. Nematostella vecfensis embryos underwent first karyokinesis -60 minutes following the addition of sperm to eggs. Second nuclear division took place, followed by first cleavage, 90-120 minutes later. Each of the 4 blastomeres that resulted from first cleavage contained a single nucleus. Arrangement of these blastomeres ranged from radial to pseudospiral. Embryonic development was both asynchronous and holoblastic. Following formation of the 4-cell stage, 71% of embryos proceeded to cleave again to form an 8-cell stage. In each of the remaining 29% of embryos, a fusion of from 2-4 blastomeres resulted in 4 possible patterns which had no affect on either cleavage interval timing or subsequent development. The fusion event was not due to ooplasmic segregation. Blastomeres isolated from 4-celled embryos were regulative and developed into normal planula larvae and juvenile anemones that were 1/4 the size of those that developed from intact 4-celled embryos. Embryos exhibiting the fusion phenomenon were examined at the fine structural level. The fusion phenomenon resulted in formation of a secondary syncytium and was not a mere compaction of blastomeres.

An atlas of reproductive development in rockfishes, genus Sebastes

The genus Sebastes consists of over 100 fish species, all of which are viviparous and long-lived. Previous studies have presented schemes on the reproductive biology of a single targeted species of the genus Sebastes, but all appear to possess a similar reproductive biology as evidenced by this and other studies. This atlas stages major events during spermatogenesis, oogenesis, and embryogenesis, including atresia, in six species of Sebastes (S. alutus, S. elongatus, S. helvomaculatus, S. polyspinis, S. proriger, and S. zacentrus). Our study suggests that the male reproductive cycle of Sebastes is characterized by 11 phases of testicular development, with 10 stages of sperm development and 1 stage of spermatozoa atresia. Ovarian development was divided into 12 phases, with 10 stages of oocyte development, 1 stage of embryonic development, and 1 stage of oocyte atresia. Embryonic development up to parturition was divided into 33 stages following the research of Yamada and Kusakari (1991). Reproductive development of all six species examined followed the developmental classifications listed above which may apply to all species of Sebastes regardless of the number of broods produced annually. Multiple brooders vary in that not all ova are fertilized and progress to embryos; a proportion of ova are arrested at the pre-vitellogenic stage. Reproductive stage examples shown in this atlas use S. elongates for spermatic development, S. proriger for oocyte development, and S. alutus for embryological development, because opportunistic sampling only permitted complete analysis of each respective developmental phase for those species. The results of this study and the proposed reproductive phases complement the recommended scheme submitted by Brown-Peterson et al. (2011), who call for a standardization of terminology for describing reproductive development of fishes.

Marine Ranching: Proceedings of the Eighteenth U.S.-Japan Meeting on Aquaculture Port Ludlow, Washington, 18-19 September 1989

Female reproduction in penaeid shrimp is carefully regulated by several different endocrine factors. Their precise modes of action have not yet been fully elucidated. Three endocrine factors, each representing a different chemical class of hormones, have been investigated in the penaeid shrimp Sicyonia ingentis in our laboratory: ecdysteroids, vitellogenesis-inhibiting hormone (VIH) , and methyl farnesoate (MF). Ecdysteroids (the steroid molting hormones of arthropods; predominantly 20-hydroxyecdysone), are initially present in low levels (<10 ng/mg) in shrimp embryos. As development of the embryos nears time of hatch, the ecdysteroid levels increase to approximately 150 ng/ mg, indicating that they may be of embryonic origin and involved in embryonic development. An assay was developed for shrimp VIH, which presumably is a protein. Delay of onset of the next reproductive cycle was observed following injection of sinus gland extracts into shrimp that had previously had their eyestalks removed. A photoaffinity analog was synthesized for the putative shrimp reproductive hormone MF-a terpenoid. This analog, farnesyl diazomethyl ketone (FDK) , was used to demonstrate the presence of specific binding proteins for MF in shrimp hemolymph. (PDF file contains 136 pages.)

Der Fischei-Test: Ein Toxizitätstest für ökotoxikologische Untersuchungen

Zebrafish (Danio rerio) embryos have been used to quantify the teratogenic potential of environmental samples and harmful substances respectively. The short spawning interval renders this species a good test organism in toxicological research. Due to the transparency of the eggs several lethal and non-lethal endpoints can be detected in parallel after 48 h of embryonic development. Zebrafishembryos have been shown to be sensitive to a number of environmental relevant contaminants, as well as to ex-tracts from polluted sediments

Changes in body composition and fatty acid profile during embryogenesis of quillback rockfish (Sebastes maliger)

We investigated developmental changes in the body compositions and fatty acid (FA) profiles of embryos and preparturition larvae of the quillback rockfish (Sebastes maliger). Comparisons of proximate composition data from early-stage embryos with data from hatched preparturition larvae taken from wild-caught gravid females indicated that embryos gain over one-third their weight in moisture while consuming 20% of their dry tissue mass for energy as they develop into larvae. Lipid contributed 60% of the energy consumed and was depleted more rapidly than protein, indicating a protein-sparing effect. Oil globule volume was strongly correlated with lipid levels, affirming its utility as an indicator of energetic status. FA profiles of early embryos differed significantly from those of hatched larvae. Differences in the relative abundances of FAs between early embryos and hatched larvae indicated different FA depletion rates during embryonic development. We conclude that some metabolically important FAs may prove useful in assessing the condition of embryos and preparturition larvae, particularly 20:4n-6, which cannot be synthesized by many marine fish and which is conserved during embryogenesis. Variability in body composition and energy use among rockfish species should be considered when interpreting any measures of condition.

A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea

A nursery site for the Alaska skate (Bathyraja parmifera) was sampled seasonally from June 2004 to July 2005. At the small nursery site (~2 km2), located in a highly productive area near the shelf-slope interface at the head of Bering Canyon in the eastern Bering Sea, reproductive males and females dominated the catch and neonate and juvenile skates were rare. Seasonal samples showed summertime (June and July) as the peak reproductive time in the nursery although some reproduction occurred throughout the year. Timeseries analysis of embryo length frequencies revealed that three cohorts were developing simultaneously and the period of embryonic development was estimated at 3.5 years and average embryo growth rate at 0.2 mm/day. Estimated egg case deposition occurred mainly during summertime and hatching occurred during winter months. Protracted hatching times may be common for oviparous elasmobranch species and may be directly correlated with ambient temperatures as evident from a meta-data analysis. Evidence indicates that the Alaska skate uses the eastern Bering Sea outer continental shelf region for reproduction and the middle and inner shelf regions as habitat for immature and subadults. Skate nurseries may be vulnerable to disturbances because they are located in highly productive areas and because embryos develop slowly.