Candidate Species For Aquaculture Research Articles

Application of GIS in Evaluating Suitable Clam Farming Site in Vembanad Lake, India

The present study identifies and quantifies appropriate sites for black clam farming in the Vembanad Lake using a geographical information system (GIS). The black clam, Villorita cpyrinoides, is the most important clam landed in India. Despite being a candidate species for aquaculture, the trials on farming of clams are very limited. The aim of this study was to select the most suitable sites for clam farming in Vembanad Lake based on the use of GIS-based models. For this, the importance of soil quality, water quality and infrastructure facilities were accessed using an analytical hierarchical process. The site suitability map was prepared using each attribute and divided into four classes, such as most suitable, moderately suitable, least suitable and poor. Water quality is found to play a major role (54%) compared to soil quality (24%) and infrastructure facilities (22%) for development of clam farms in Vembanad Lake. Salinity registered the highest importance (0.21) for the water quality suitability map as compared to other parameters like pH and dissolved oxygen. The total area covered under this study was 6471 ha out of which, 3121 ha (48%) was identified as most suitable and of the remaining 3350 ha, 1804 ha (28%) was identified as moderately suitable, 946 ha (15%) was identified as least suitable and 600 ha (9%) was identified as the poor site for clam farming in Vembanad Lake.

Temperature regulates sex determination and growth in the paralichthid flatfishCalifornia halibut.

California halibut (Paralichthys californicus) is a candidate species for aquaculture and stock enhancement. These applications rely on sex control, either to maximize the production of faster growing females or to match sex ratios in the wild. Other paralichthids exhibit temperature-dependent sex determination (TSD), but the presence and pattern of TSD is not well defined in California halibut. Juvenile California halibut were cultured at three distinct temperatures (15°C, 19°C, and 23°C) through the developmental period presumed to be thermosensitive based on findings from congeners. Sex ratios were quantified in each treatment using phenotypic sex identification techniques applied early (molecular biomarkers; 51-100 mm total length [TL]) and late (visual examination of the gonads; ≥100 mm TL) in the juvenile phase. Both techniques indicated similar sex determination trends at each temperature, with overall sex ratios assessed as 49.9% maleat 15°C, 74.5% maleat 19°C, and 98.2% maleat 23°C. Growth rates were highest at 23°C and lowest at 15°C, with intrinsically fast- and slow-growing individuals at all temperatures. At 15°C and 19°C, females comprised a higher proportion among the fast growers than they did among the slow growers. These data show that California halibut exhibit TSD, with temperatures of 19°C and 23°C masculinizing fish while 15°C appears to produce a 1:1 sex ratio. This study will help optimize sex ratios and growth in hatcheries through thermal manipulation. Furthermore, the developed biomolecular tools and identified temperature thresholds will be important in future work to understand the influence of global warming on wild population demographics.

A new species of pisang shrimp, Penaeus symplex revealed by molecular DNA analyses, as candidate species for aquaculture in Indonesia

A new species of pisang shrimp, <i>Penaeus symplex</i> revealed by molecular DNA analyses, as candidate species for aquaculture in Indonesia

Culture Potential of Mud Crab in Konkan Region of Maharashtra

The Konkan, is a western Indian coastal plain located between the Arabian Sea and the Western Ghats (east). The plain extends roughly 330 miles (530 km) from the Terekhol River between the states of Maharashtra and Goa and the union territory of Daman and Diu in the south to the Daman Ganga River to the north of Mumbai (Bombay). between 45 and 76 kilometers (28 to 47 miles) in width. The adoption of scientific and technical knowledge of ecological and resource potential studies has foreseen the proper utilization of this natural resource for sustainable development. The majority of the farms in the Indian shrimp business have been decimated by infections, primarily WSD. The main issue in shrimp farming is viral infections, which hamper the nation's social and economic development. Socioeconomic estimates of the effects of diseases include issues like losses in production, revenue, employment, investor and customer trust, food shortages, trade disruptions, or firm closure. Due to their attractive traits, such as quick growth, greater size, high fertility, disease resistance, marketability, adaptability to farming techniques, etc., mud crabs are a "candidate species for aquaculture.

Genetic stock identification in Perna viridis (Linnaeus1758) from the Indian Peninsula by using microsatellite markers.

Perna viridis (Linnaeus, 1758), the Asian green mussel, is native to the Asia-Pacific region. The species is extensively distributed in the Indian subcontinent and is a candidate species for aquaculture in the Southeast Asian region. Availability of genetic information on wild populations is essential for the effective conservation and management of Perna species. The present study assessed the genetic variation and population structure across the distribution range of this species from the Indian peninsula by using microsatellite markers to determine the genetic structuring among the species. A total of 15 microsatellite loci with M13 labeling were used for the genetic characterization of P. viridis along Indian waters. Genotyped data were analyzed using analytical software to determine the genetic stocks and understand the genetic variability across the populations. We identified 15 polymorphic markers to understand the genetic stocks and variability across Perna populations. The mean value of the observed heterozygosity (Hobs: 0.741) for all populations was closer to the expected heterozygosity (Hexp: 0.75). The pairwise Fst values between the west and east coasts of India varied significantly, indicating the existence of significant genetic structure between the populations. Genetic stock identification using software analysis exhibited two distinct stocks, one along the west coast (Arabian Sea) and another along the east coast (Bay of Bengal). Bottleneck analysis indicated the genetic stability of species in the wild. P. viridis is a commercially vital species in Indian peninsular regions. The present study suggests the adoption of stock-specific relaying programs of the species from Indian waters in future studies.

Arsenic Bioaccumulation and Identification of Low-Arsenic-Accumulating Food Fishes for Aquaculture in Arsenic-Contaminated Ponds and Associated Aquatic Ecosystems.

Arsenic-contaminated food including farmed fish is one of the main routes of human exposure. Fish farmed in contaminated environment accumulates arsenic in different tissues with great variability. Thus, it is utmost important to quantify the risk associated with different farmed fish species in arsenic-contaminated aquaculture systems. In the present study, arsenic content was measured in twelve fish species (Labeo rohita, L. catla, Cirrhinus mrigala, Oreochromis niloticus, O. mossambicus, Liza tade, Puntius javanicus, L. calbasu, Glossogobius giuris, Macrobrachium rosenbergii, Ctenopharyngodon idella, and Bellamya bengalensis (gastropod)) collected from arsenic-contaminated aquaculture systems. Among the studied finfishes, C. idella was found to accumulate the lowest amount of arsenic (< 0.05 ± 0.00mgkg-1) whereas the highest accumulation was noticed in O. mossambicus (1.0 ± 0.18mgkg-1). However, the estimated carcinogenic and non-carcinogenic risks of human were found to be low for all the studied fishes. The calculated target hazard quotient (THQ) value for adults ranged from 0.01 to 0.08 whereas for children it ranged from 0.05 to 0.27 for low-arsenic-accumulating fishes (arsenic conc. < 0.5mgkg-1). Based on these findings, C. mrigala, C. idella, and M. rosenbergii could be recommended as the candidate species for aquaculture in the arsenic-contaminated areas as farming of the low-arsenic-accumulating food fishes would also lower the risk of human exposure through food chain.

Comparative Ecology of Feeding and Digestion of Two Notopterid Fishes Inhabiting River Punarbhaba in India

Resource partitioning among coexisting species leads to divergent changes in morphological, behavioural and physiological characteristics of animals providing insights in niche availability. Chitala chitala (Hamilton-Buchanan, 1822) and Notopterus notopterus (Pallas, 1769) are two Notopterid fishes belonging to order Osteoglossiformes found to coexist in Indian waters. Both the species command high market demand not only as food fish but also as aquaria fishes making them new candidate species for aquaculture. Feeding ecology of these species were studied through prey electivity analysis, calculation of Index of Relative Importance of food items, estimation of digestive enzymes accompanied by morphometric study. Toothed jaw and higher relative gape width makes C. chitala an efficient predator whereas N. notopterus with obliquely placed and slightly upturned mouth, prominent lower jaw, higher head and body depth, well-developed stomach establish N. notopterus as an omnivore. The results also highlight N. notopterus having larger niche breadth surviving on wide prey base in nature could justifiably be a more common species found in wider area of South East Asia whereas C. chitala being carnivorous, having smaller niche breadth enjoys relatively restricted geographical distribution.

Comparison of Electronic Length Frequency Analysis (ELEFAN) for Estimation of Growth Parameters for Lollyfish, Holothuria (Holothuria) atra and Sand Sea Cucumber, Holothuria (Thymiosycia) arenicola (Holothuroidea: Echinodermata) in the North Arabian Sea, Pakistan

To estimate the growth parameters, the non-seasonal von Bertalanffy and Hoenig seasonal von Bertalanffy models were fitted to the length frequency data of Holothuria atra and H. arenicola obtained from coastal areas of Karachi in the northern Arabian Sea, Pakistan between January and December 2014. The Hoenig seasonal von Bertalanffy growth parameters were estimated as L∞=36.1 cm total length (TL), K=0.75 year-1 for H. atra and as L∞=34.9 cm TL, K=0.70 year-1 for H. arenicola. H. atra individuals reached 73.9% of their maximum total length at the one year old. For H. arenicola it was calculated as 72.7%. Monthly mean growth rate of H. atra at the same ages was calculated higher than H. arenicola. The seasonal oscillation in growth rate for H. atra (C=0.50) was larger than it was for H. arenicola (C=0.37). The time of the year when the growth is slowest corresponded to the middle of April (WP=0.30) in H. atra and at the beginning of August (WP=0.60) in H. arenicola may be the result of the extended both reproduction and poor nutrition periods due to monsoonal effects on the marine environment. The relatively high growth rates (K&amp;gt;0.7 year-1) of these two species may have important implications for high survival rate, particularly in environmental condition where cause biological stress and marine confusion but may also increase their potential as a candidate species for aquaculture.

The microanatomy of the central nervous system and brain of the Indo-Pacific seahorse, Hippocampus barbouri, during development

The central nervous system (CNS) of Teleostei is a complex system of self-governance and its morphology is reflected in the physiological and reproductive behaviors. The Indo-Pacific seahorse, Hippocampus barbouri Jordan &amp;amp; Richardson, 1908, is a new candidate species for aquaculture in Thailand. In this study, we investigated the brain morphology of H. barbouri across various developmental windows. Light microscopic observations of adult brains revealed a large optic tectum in the mesencephalon, whereas the cerebral hemispheres and the cerebellum are of medium size. The detailed brain structures were generally similar to those of other teleosts; however, only five distinct layers were present in the optic tectum, including the stratum marginale, stratum opticum, stratum album central, stratum griseum central, and stratum periventriculae, versus six layers observed in other fish. One day after birth (1 DAB) the brain was a packed structure without any clear sub-structures. The number of capillaries in the optic tectum began to increase at 6 DAB, and at 14 DAB several features, including small blood vessels in the optic tectum and Purkinje cells, became noticeable. By 35 DAB, the optic tectum became highly vascularized and included five layers. Additionally, large Purkinje cells were developed in the cerebellum. Based on the brain development pattern, we speculate that the predatory ability of this fish starts to develop from 6 to 14 days after birth.

Squamous Cell Carcinoma (SCC) in Brown meagre (Sciaena umbra Linnaeus, 1758), a new candidate species for aquaculture in Mediterranean

A case of epithelial tissue tumors on the body of two adult Brown meagres (Sciaena umbra Linnaeus, 1758) is reported. Brown Meagre population of 20.000 was imported to sea cages on September of 2003 at 3g, to check the potential use of this species as a new candidate in Mediterranean aquaculture. The population had been kept for 8 years to serve as a genetic pool for further zootechnical investigation. The main pathology observed after 8 years in the sea cages were mainly ocular lesions (cataract) possibly due to natural aging and/or long culture period under high natural light intensity (UV radiation) and/or net injuries at a percentage of 1,32% of total cultured population. Apart from that, on two fish, reddish- white tumorous growths were evident on skin, macroscopically. Histologically, the timorous growths were diagnosed as Squamous cell carcinoma. Numerous rounded pearls and nests of epidermal proliferated cells were evident, some of which had a non-cellular center. There were also foci of necrosis and irregular deposits of keratin within the tumor tissue. Special stains (Ayoub-Shklar, Haematoxylin-Eosin &amp; Schiff’s Periodic Acid) were applied to the tissue for comparison. To our knowledge this is the first presented report of SCC in this species.

Comparative evaluation of metabolic enzymes activities in different tissues of striped catfish, Pangasianodon hypophthalmus (Sauvage, 1878) fingerlings reared at ambient and higher temperature

A 60-days feeding trial was conducted to study the effect of higher temperature (32°C) in comparison to ambient temperature on different metabolic enzyme namely, Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Adenosine triphosphatase (ATPase), Acid Phosphatase (ACP) & Alkaline Phosphatase (ALP) activities in different tissues of Pangasianodon hypophthalmus. AST activity differs significantly (P 0.05). The ALT activity differs significantly (P 0.05) whereas ATPase activity in the liver at different temperature differ significantly (P<0.05). ACP activity does not vary significantly at different temperature whereas, ALP activity varies significantly at different temperature in liver and intestine tissues. The present study clearly shows that there is a temperature dependent change in the activity of the different metabolic enzyme in different tissue studied in comparison to the control at ambient temperature fed with different energy level diet. The finding of the present study suggests that the metabolic responses are variable at different temperature and different energy level which can affect the growth performances of this new candidate species for aquaculture.

Reproductive performance of asian catfish ( Hemibagrus wyckii Bleeker, 1858), a candidate species for aquaculture.

Background:Hemibagrus wyckii Bagridae is one of the important economic fish species that lives in the rivers and reservoir in Riau Province, Indonesia. The present study aimed to determine the reproductive performance of H.wyckii under culture conditions. Methods: A total of 10 female and 10 male fish were selected, and weight, length, characteristics of egg and sperm, and hatchery performance were measured. Eggs were fertilized using the dry method. Egg weight and egg diameters were measured for 50 eggs per female. Egg size (50 eggs for each fish) was measured using Labo microscope model L-711 using software camera 3. Then, saline solution was added over the eggs, followed by the addition of pooled sperm from 10 males. Results: Average relative fecundity, egg weight and egg diameter were 2060±512 eggs/kg fish, 29.86±1.21 mg and 2.67±0.26 mm, respectively. The fertilization rate and hatching rate were 60.91±4.68% and 42.91±2.92% respectively. Sperm characteristics such as volume per fish (mL), pH, concentration (per mL), motility (%) and duration of motility (second) were 0.82±0.20, 7.15±0.12, 3.68±0.15, 72.77±1.46 and 47.5±4.84, respectively. Conclusion: The study results and scientific observations regarding reproductive performance suggest that H. wyckii can be considered a new candidate species for aquaculture.

Broodstock development, induced breeding and larval rearing of Indian pompano, Trachinotus mookalee, (Cuvier, 1832) – A new candidate species for aquaculture

The present study describes the first trial on broodstock development, induced breeding and larval rearing of Indian pompano, Trachinotus mookalee. Indian pompano fingerlings were collected from wild and raised to adults having an average size of 2.84 ± 0.10 kg weight and 47.6 ± 1.43 cm length. These adult fishes were stocked in 125 t capacity circular tank having re-circulatory facility for broodstock development. The fishes were fed with squid along with clam meat and matured in four months. Mature females with >500 μm ova and oozing males were selected in the ratio of 1:2 (female:male) and were induced with single dose of hCG at the rate of 350 IU /kg body weight. Three trials with same sex ratio and hormonal doses were tried. The fish spawned after 36–38 h of induction at a temperature 29 ± 1 °C. Eggs were collected and treated with iodophore and stocked in 1 t FRP tank for hatching. The eggs hatched out after 18–20 h of incubation at a temperature of 29 ± 1 °C. The overall fertilization and hatching rate was found to be 69 ± 1.55% and 87.67 ± 0.81%, respectively. Larval rearing was carried out in 2 t capacity fibre reinforced plastic (FRP) tanks using green water system. The newly hatched larvae was 2.12 ± 0.02 mm in total length, with an oval shaped yolk sac of 0.55 mm2 and an oil droplet of 0.06 mm2 in area. The mouth opening was formed 40–46 h post hatch with mouth gape measuring 228.10 ± 1.31 μm. A systematic and overlapping regime of live feed beginning from copepod nauplii, rotifer, Artemia nauplii and artificial pellet were utilized during larval rearing. Weaning of larvae to inert diet was started from 15th day post hatching (DPH) onwards. Larvae started metamorphosis by 17th DPH onwards and was completed by 21st DPH, when the larvae reached 27.33 ± 0.10 mm. The larval rearing protocol resulted in an average survival rate of 21.53 ± 1.45% till complete metamorphosis. The present study showed T. mookalee to mature in captive conditions. The potential for induced spawning in captivity and larval rearing with a survival rate of 21.53% makes Indian pompano an excellent candidate for mariculture. This forms the first report of broodstock development, induced breeding and larval rearing of this species in captivity. The results of this study would facilitate mass scale seed production of Indian pompano in captivity, which is essential for its aquaculture.

Reproductive performance of asian catfish ( Hemibagrus wyckii Bleeker, 1858), a candidate species for aquaculture

Background: Hemibagrus wyckii Bagridae is one of the important economic fish species that lives in the rivers and reservoir in Riau Province, Indonesia. The present study aimed to determine the reproductive performance of H.wyckii under culture conditions. Method s: A total of 10 female and 10 male fish were selected, and weight, length, characteristics of egg and sperm, and hatchery performance were measured. Eggs were fertilized using the dry method. Egg weight and egg diameters were measured for 50 eggs per female. Egg size (50 eggs for each fish) was measured using Labo microscope model L-711 using software camera 3. Then, saline solution was added over the eggs, followed by the addition of pooled sperm from 10 males. Results: Average relative fecundity, egg weight and egg diameter were 2060±512 eggs/kg fish, 29.86±1.21 mg and 2.67±0.26 mm, respectively. The fertilization rate and hatching rate were 60.91±4.68% and 42.91±2.92% respectively. Sperm characteristics such as volume per fish (mL), pH, concentration (per mL), motility (%) and duration of motility (second) were 0.82±0.20, 7.15±0.12, 3.68±0.15, 72.77±1.46 and 47.5±4.84, respectively. Conclusion: The study results and scientific observations regarding reproductive performance suggest that H. wyckii can be considered a new candidate species for aquaculture.

Reproductive performance of asian catfish (Hemibagrus wyckii Bagridae), a candidate species for aquaculture

Background: Hemibagrus wyckii Bagridae is one of the most important economic fish species that lives in the rivers and reservoir in Riau Province, Indonesia. The present study aimed to determine the reproductive performance of H.wyckii under culture conditions. Methods: A total of 10 female and 10 male fish were selected, and weight, length, characteristics of egg and sperm, and hatchery performance were measured. Eggs were fertilized using the dry method. Egg weight and egg diameters were measured for 50 eggs per female. Egg size (50 eggs for each fish) was measured using an Olympus microscope (CX40). Then, saline solution was added over the eggs, followed by the addition of pooled sperm from 10 males. Results: Average relative fecundity, egg weight and egg diameter were 2060±512 eggs/kg fish, 29.86±1.21 mg and 2.67±0.26 mm, respectively. The fertilization rate and hatching rate were 60.91±4.68% and 42.91±2.92% respectively. Sperm characteristics such as volume per fish (mL), pH, concentration (per mL), motility (%) and duration of motility (second) were 0.82±0.20, 7.15±0.12, 3.68±0.15, 72.77±1.46 and 47.5±4.84, respectively. Conclusion: The study results and scientific observations regarding reproductive performance suggest that H. wyckii can be considered a new candidate species for aquaculture.

Deciphering demographic history and fine-scale population structure of cobia, Rachycentron canadum (Pisces: Rachycentridae) using microsatellite and mitochondrial markers

Cobia, Rachycentron canadum is a candidate species for aquaculture, distributed across the Indo-Pacific waters to the southern Atlantic Ocean. Information on genetic diversity and population structure of cobia is crucial for sustainable utilization and management of the species in natural waters. In the present study, we used 14 polymorphic microsatellite loci and mitochondrial cytochrome b gene (980 bp) to investigate the genetic diversity and population structuring of R. canadum along the Indian coast. Microsatellite analysis suggests a relatively high level of genetic diversity of cobia in the Indian region, with a mean Ho and He of 0.76 and 0.73. The PIC was also highly informative (0.841), with a mean no. of alleles of 11.304. Hierarchical AMOVA and genetic differentiation co-efficient between the populations was found to be low, but significant (FST = 0.035, P < 0.001), indicating fine scale structuring in the region. Pair-wise FST, neighbor-joining tree, principal coordinates analysis, and Bayesian analysis depict three populations of cobia in Indian waters: two in the Arabian Sea and one in the Bay of Bengal. The mitochondrial gene analyses showed discordant findings in comparison with microsatellite markers. However, both the markers yielded no inference of historical demographic bottleneck. Multi-modal mismatch distributions and ragged index, non-significant Tajima’s D and Fu’s FS, and L-shaped distribution pattern of the allele frequencies, indicated the lack of bottleneck events of the species in the recent past. Based on mitochondrial gene analysis, the population expansion was inferred to have occurred 0.046 Myrs ago, corresponding to the late Pleistocene.

Prey Capture, Ingestion, and Digestion Dynamics of Octopus vulgaris Paralarvae Fed Live Zooplankton.

Octopus vulgaris is a species of great interest in research areas such as neurobiology, ethology, and ecology but also a candidate species for aquaculture as a food resource and for alleviating the fishing pressure on its wild populations. This study aimed to characterize the predatory behavior of O. vulgaris paralarvae and to quantify their digestive activity. Those processes were affordable using the video-recording analysis of 3 days post-hatching (dph), mantle-transparent paralarvae feeding on 18 types of live zooplanktonic prey. We show for the first time in a live cephalopod that octopus paralarvae attack, immobilize, drill, and ingest live cladocerans and copepods with 100% efficiency, which decreases dramatically to 60% on decapod prey (Pisidia longicornis). The majority (85%) of successful attacks targeted the prey cephalothorax while unsuccessful attacks either targeted the dorsal cephalothorax or involved prey defensive strategies (e.g., juvenile crab megalopae) or prey protected by thick carapaces (e.g., gammaridae amphipods). After immobilization, the beak, the buccal mass and the radula were involved in exoskeleton penetration and content ingestion. Ingestion time of prey content was rapid for copepods and cladocerans (73.13 ± 23.34 s) but much slower for decapod zoeae and euphausiids (152.49 ± 29.40 s). Total contact time with prey was always <5 min. Contrary to the conventional view of crop filling dynamics observed in adult O. vulgaris, food accumulated first in the stomach of paralarvae and the crop filled after the stomach volume plateaued. Peristaltic crop contractions (~18/min) moved food into the stomach (contractions ~30/min) from where it passed to the caecum. Pigmented food particles were seen to enter the digestive gland, 312 ± 32 s after the crop reached its maximum volume. Digestive tract contents passed into the terminal intestine by peristalsis (contraction frequency ~50/min) and defaecation was accompanied by an increased frequency of mantle contractions. Current results provide novel insights into both, O. vulgaris paralarvae—live prey capture strategies and the physiological mechanisms following ingestion, providing key information required to develop an effective rearing protocol for O. vulgaris paralarvae.

Observation of Wild Seaweed Species in Labuhanbua Waters, Indonesia: a preliminary assessment for aquaculture development

Seaweed industry has been growing up and is supplied by either wild or cultivated seaweed crops. This study was aimed to present relevant information regarding ecological availability of wild seaweed in Labuhanbua coastal waters, Sumbawa Regency, West Nusa Tenggara and potential use of important species as candidate species for aquaculture. 46 sampling stations were determined along line transects perpendicular to coastal line; and seaweeds sampling were conducted during low tide by using 1 x 1 m2 quadrat transect. Field data consist of in-situ parameter including number of seaweed species and coverage area of each species; and ex-situ parameters consist of carbohydrate, protein, total C, total N, and total P content of seaweeds. The results showed that 33 species were found and three species has the most widely distribu tion, i.e. Padina sp., Dictyota dichotoma, and Gracilaria salicornia. Turbinaria, Dictyota, Padina, Stoechospermum, Hydroclathrus, Halimeda, and Chaetomorpha might be some important species that could be develop as aquaculture species candidates among other uncultivated species that were found along this study location. They have potencies as human food, livestock feed, neutraceuicals, cosmetics, pulp, textile, biofuel and any other industries; but conversely, they were found in lower density at Labuhanbua coastal waters. These species should be develop through aquaculture technology, involve genetic improvement and possibly genetic engineering. Commercial scale cultivation of those important seaweed species will contribute to industrial needs and prevent decreasing of wild seaweed availability in natural ecosystem.

Structure and ultrastructure of oogenic stage in short mackerel Rastrelliger brachysoma (Teleostei: Scombidae)

Abstract Introduction: Structure, ultrastructural features and degeneration of oogenesis were first investigated in female Rastrelliger brachysoma as new candidate species for aquaculture by transmission electron microscopy. Materials and Methods: Specimens were naturally collected during the breeding season from Samut Songkhram Province, Thailand. Results: The ultrastructure of female oogenesis was principally divided into five stages based on the nuclear characterization and cytoplasmic organelles; (i) oogonium; (ii) previtellogenic; (iii) lipid and cortical alveolar; (iv) early and (v) late vitellogenic stages. Initially, oogonium was present within cell nest in the epithelial compartment. Its cell was supported by prefollicular cells. The multiple nucleoli in previtellogenic stage, referring to primary growth stage were the first to appear and they were scattered around the peripheral of nuclear membrane with the increasing number of cytoplasmic organelles. Some microvilli of granulosa cell initially protruded into the vitelline envelope. A simple layer of flattened granulosa and theca cells was also observed. The lipid and cortical alveolar stage under secondary growth oocyte was accumulated with two inclusions; the lipid droplets and cortical alveoli in the ooplasm. Another characterization, the increasing of numerous microvilli was also detected in the vitelline envelope. Finally, in the vitellogenic stage, a massive uptake and processing of proteins into yolk platelets due to embedding of the numerous microvilli in the largest vitelline envelope was observed. Oocyte degeneration in R. brachysoma was novel found especially oogonial and previtellogenic stages. Conclusion: Five oogenic stages of this fish are found with the changing of the arrangement of nucleus, cytoplasmic organelles and follicular complex, which will be applied to further studies.

Selection of reliable reference genes for RT-qPCR studies in Octopus vulgaris paralarvae during development and immune-stimulation

The common octopus, Octopus vulgaris is a new candidate species for aquaculture. However, rearing of octopus paralarvae is hampered by high mortality and poor growth rates that impede its entire culture. The study of genes involved in the octopus development and immune response capability could help to understand the key of paralarvae survival and thus, to complete the octopus life cycle. Quantitative real-time PCR (RT-qPCR) is the most frequently tool used to quantify the gene expression because of specificity and sensitivity. However, reliability of RT-qPCR requires the selection of appropriate normalization genes whose expression must be stable across the different experimental conditions of the study. Hence, the aim of the present work is to evaluate the stability of six candidate genes: β-actin (ACT), elongation factor 1-α (EF), ubiquitin (UBI), β-tubulin (TUB), glyceraldehyde 3-phosphate dehydrogenase (GADPH) and ribosomal RNA 18 (18S) in order to select the best reference gene. The stability of gene expression was analyzed using geNorm, NormFinder and Bestkeeper, in octopus paralarvae of seven developmental stages (embryo, paralarvae of 0, 10, 15, 20, 30 and 34days) and paralarvae of 20days after challenge with Vibrio lentus and Vibrio splendidus. The results were validated by measuring the expression of PGRP, a stimuli-specific gene. Our results showed UBI, EF and 18S as the most suitable reference genes during development of octopus paralarvae, and UBI, ACT and 18S for bacterial infection. These results provide a basis for further studies exploring molecular mechanism of their development and innate immune defense.