Observation on the reproductive behavior and embryo of the daisy’s ricefish, Oryzias woworae in laboratory condition

Oryzias woworae is an endemic ricefish from Muna Island, Southeast Sulawesi, traded as an ornamental fish. Information on the biology of these fish is very lacking, including their reproductive. These fish also face the threat of population decreasing in the wild. The research aimed to examine the spawning behavior and embryonic of O. woworae as the basis for aquaculture. Fish spawning was carried out using 1 male: 1 female ratio, which was repeated three times. The observed spawning behavior was pre-spawning, mating process, egg number, and morphology. Behavioral observations were carried out for five days of spawning. Observation of embryos was carried out to see the stages of embryo development until hatching. The results obtained on pre-spawning behavior were changes in body color and blackened fins in males, which did not occur in female fish. Males actively swim by approaching their dorsal and anal fins while chasing females. The female releases the eggs and is attached to the substrate, rapidly fertilized by the male fish. There is a phenomenon of females carrying eggs on the genital pore before being released to the substrate (non-pelvic brooder). Spawning only occurs during the day, and spawning is getting faster, which is at 09:00 AM on the fifth day. Oryzias woworae eggs have a diameter of 1.3 ± 0.2 mm, equipped with attaching and non-attaching filaments. Observations of O. woworae embryos showed that embryo hatching occurred at seven days 23 hours post-fertilization.

Biological Aspects of Waanders’s Hard-lipped Barbs (Osteochilus waandersii) in Tambatan River, North Sumatera, Indonesia

Background: Waanders’s hard-lipped barbs or scientifically known as Osteochilus waandersii belong to the family Cyprinidae with the potamodromous category. This fish can be found in the Tambatan river. It has the potential for commercial consumption or ornamental fish. Methods: This study was conducted in the Tambatan river from November to January 2021. The determination of three research stations was carried out using a purposive sampling method. Sampling was undertaken using cast nets. Furthermore, data analyzed were growth patterns, condition factors, and gonad maturity levels. Results: The growth patterns of male (1.944) and female (2.379) Osteochilus waandersii were in a negative allometric category. Besides, The Fulton's condition factor for male fish ranged from 0.42 - 3.43 with an average of 1.05, while that for female fish ranged from 0.59 - 3.67 with an average of 1.47. The result of the observation on the gonad maturity level for male and female O. waandersii in the Tambatan river indicated that they were dominated by fish with gonad maturity stage I (immature). Conclusions: Waanders’s hard-lipped barbs O. waandersii found were in the stage towards the mature level.

A Time-Saving Strategy to Generate Double Maternal Mutants by an Oocyte-Specific Conditional Knockout System in Zebrafish

Maternal products are those mRNAs and proteins deposited during oogenesis, which play critical roles in controlling oocyte formation, fertilization, and early embryonic development. However, loss-of-function studies for these maternal factors are still lacking, mainly because of the prolonged period of transgenerational screening and technical barriers that prevent the generation of maternal (M) and maternal and zygotic (MZ) mutant embryos. By the transgenic expression of multiple sgRNAs targeting a single gene of interest in the background of a transgenic line Tg(zpc:zcas9) with oocyte-specific cas9 expression, we have successfully obtained maternal or maternal–zygotic mutant for single genes in F1 embryos. In this work, we tandemly connected a maternal GFP marker and eight sgRNA expression units to target dvl2 and dvl3a simultaneously and introduced this construct to the genome of Tg(zpc:zcas9) by meganuclease I-Sce I. As expected, we confirmed the existence of Mdvl2;Mdvl3a embryos with strong defective convergence and extension movement during gastrulation among outcrossed GFP positive F1 offspring. The MZdvl2;MZdvl3a embryos were also obtained by crossing the mutant carrying mosaic F0 female with dvl2+/−;dvl3a−/− male fish. This proof-of-principle thus highlights the potential of this conditional knockout strategy to circumvent the current difficulty in the study of genes with multiple functionally redundant paralogs.

Preference and Motivation Tests for Body Tactile Stimulation in Fish

We tested whether territorial fish (Nile tilapia) perceive body tactile stimulation as a positive or negative resource. Individual male fish were placed for eight days in an aquarium containing a rectangular PVC frame, which was filled with vertical plastic sticks sided with silicone bristles in the middle of the tank. Fish passing this device received a tactile stimulus. The fish then underwent a preference test by choosing between areas half-with and half-without tactile bristles. Then, fish were submitted to a motivation test where they had to pass an aversive stimulus (bright light) to access the device. Fish were, then, paired to settle social rank, which occurs by way of fights (social stressor), and were assigned again to preference and motivation tests. A group without social stress was used as a control. Contrary to our expectations, fish preferred the area without tactile bristles, although subordinate fish reached tactile stimulation more than the dominant one. Social stress did not affect the preference and motivation, suggesting that fish do not perceive tactile stimulation as a stressor reliever. However, as fish did not avoid the stimulation, reached the device spontaneously, and faced an aversive stimulus to access it, we conclude that tactile stimulation is not a negative condition and, therefore, can be used in further studies regarding fish welfare.

Reproduction Control in Coptodon zillii using Abrus precatorius Root Bark Diets as Fertility Inhibitor Agent

The antifertility effects of Abrus precatorius root bark meal (APRB) on Coptodon zillii juvenile was determined by a 42 days feeding experiment, with the inclusion levels of 0g, 6g, 12g, 18g and 24g/kg diet. Water volume of 20 litres in a plastic tank (50cm x 27cm x 35 cm dimension) was maintained throughout the period of experiment. Coptodon zillii was fed at 4% body weight. In male fish, testis weight, milt volume, milt count and motility duration reduced with increase in inclusion level and there were significant differences (P<0.05) in the treatments used. Histology of testis at 0g of APRB/kg diet showed primary and secondary spermatocytes in the seminiferous tubule, connective tissue was clearly seen. In treatments 6g, 12g, 18g and 24g APRB/kg diets, there were increase in interstitial cell, eroded connective tissue and necrosis. In female fish, ovary weight, fecundity, relative fecundity and gonadosomatic index reduced with increase in the concentration of treatments used. Histology of the ovary at 0g APRB/kg diet showed developing oocytes while treatments 6g, 12g, 18g and 24g revealed reduced oocytes, increase in interstitial cell, alteration in ovary development and necrosis. The research revealed that Abrus precatorius root bark meal may be effective in controlling reproduction in Coptodon zillii.

Reproduction biology of Abe's flyingfish, Cheilopogon abei Parin, 1996 in Geser East Seram Strait Waters

Eco-biological information of Cheilopogon abei in Geser Streit is unknown. The objective of this research is to observe the sex ratio, first size maturity, gonad maturity and gonado somatic index (GSI) with fecundity of flying fish Ch abei in Geser East Seram Strait waters. Sampling was done for ten months started from February to November 2018, using gill net measuring 1.50 inch. All fish samples were measured in fork length and weighted so dissected to make observations on the level of gonad maturity and the number of eggs in female fish. A total of 682 flying fish was found during the study with a fork length range of 182.6-243.3 mm and a weight of 73.98-115.45 g. The results of the analysis showed that the proportion of the number of male fish was less than that of the female fish for almost every month of observation. The first size gonad mature of male and female is 210.5 mm and 214.1 mm FL. The gonad maturity index of male fish ranges from 0,963-7,967 and female fish ranges 1,315-8,069, the total fecundity is 2321-9438 eggs. Gonads of ripe fish in each month of observation. The spawning peak of Ch abei takes place in June-July and it is hoped that no arrests will be made in both months, to ensure the sustainability of the stock.

Biological responses fish exposed to municipal wastewater treatment plant effluent in situ

Effluents from municipal wastewater treatment plants (MWTPs) are complex mixtures of chemicals including endocrine-disrupting compounds (EDCs) and 17α-ethynylestradiol (EE2). The objective of this study was to evaluate selected responses of two fish species, in two different years, exposed in situ to MWTP effluent. Biological markers of exposure (plasma vitellogenin (VTG) and antioxidant enzymes) were measured in two species of male fish, rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), caged at sites associated with wastewater outfall. The estrogenicity of the final effluent in 2010 was determined to be 17.0 + 0.4 ng/L estrogen equivalents (EEQ) and reduced to 7.5 + 2.9 ng/L EEQ after infrastructure upgrades. Pharmaceuticals and personal care products in the effluent and surface water in both years confirmed the exposures at each downstream site. Despite the presence of estrogenic compounds in the MWTP effluent, no effluent-caged male fish demonstrated plasma VTG induction. Minnows and trout that received an intraperitoneal injection of 5 mg/g EE2 showed VTG induction at both field sites. In 2012, the liver somatic index (LSI) of both species increased with exposure, as did changes in antioxidant enzymes, and reactive oxygen species (ROS) activity. Multiple biological mechanisms are modified by effluent exposure, and multiple endpoints are needed to assess risk.

Development of Induced Breeding Technique for Freshwater Fish Gobi, Glossogobius giuris (Hamilton, 1822) Using Pituitary Gland (PG) Extract

This study aimed to establish induced breeding technique of freshwater fish gobi (Glossogobius giuris), using the pituitary gland (PG) extract. Six experiments were conducted at the Department of Fisheries Biology and Genetics, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh. First breeding trial was conducted in June using 40, 45, and 50 mg PG kg-1 body weight of the female fish. None of the fish was ovulated in the 1st trial. Two more breeding trials were conducted in July and August, using 6 mg (T1), 8 mg (T2) and 10 mg (T3) PG kg-1 body weight of female, and 3 mg (T4), 4 mg (T5) and 5 mg (T6) PG kg-1 body weight of male fish. After treatment, the ovulation rates were recorded as 56.33±1.53, 82.67±2.52 and 75.33±1.53% in July and 58.00±2.65, 94.67±1.53 and 78.33±1.53% in August under the treatments T1, T2 and T3, respectively. Hatching rates of eggs were observed as 52.00±4.36, 81.67±3.21 and 72.33±6.03% in July, and 54.67±3.23, 91.67±3.06 and 73.67±5.13% in August under the T1, T2 and T3, respectively. Hatching time was ranged from 35 to 48 h and after the absorption of yolk sac (60-72 h), they were survived well when fed with tubificid worms and mixed zooplankton. The female treated with the dose of 8 mg PG kg-1 body weight in August showed the best performance so far as the ovulation, fertilization and hatching rates were concerned, while the single dose of 4 mg kg-1 body weight of PG was found to be effective for male fish in both months. The findings obtained from the present study reveals that induced breeding of G. giuris, using PG extract is successful for large scale production of quality seed in captive condition, which would further facilitate towards the aquaculture production and biodiversity conservation of this important fish species to a greater extent.

Evaluation of management factors affecting the relative success of a Brook Trout eradication program using YY male fish and electrofishing suppression

Removal of non-native fish populations can be crucial to the conservation of native species, but often presents a complex challenge for managers. The goal of Trojan Y chromosome (TYC) programs is to skew the non-native sex ratio until only males remain, leading to eradication. We present results from a simulation model used to explore effects of alternative management approaches on an in-progress mechanical removal and TYC program to eradicate non-native Brook Trout. Simulation results indicated that stocking fingerling YY males (~137 mm) was more effective than stocking catchable-sized YY males (~230 mm), although questions about inter-cohort competition warrant further investigation. Increasing the proportion of mature fingerling YY males reduced treatment time by increasing the number of YY male spawners and increasing density-dependent mortality on young, mature wild Brook Trout. Maximizing the spatial distribution of YY male releases may be crucial to program success but is also dependent upon immediate dispersal movements. Principles derived from our results can be broadly applied to the management of other aquatic invaded systems using TYC programs to eradicate non-native species.