Breeding and larval rearing in hatchery of Macrobrachium vollenhovenii (Herklots, 1857) in a perspective of biological control against human Schistosomiasis in tropical area

As part of an effort to use biological control against human schistosomiasis, post-larval production of the prawn Macrobrachium vollenhovenii was carried out in a hatchery. This species is a freshwater native and is fond of mollusks, intermediate hosts of schistosomes that transmit human diseases in the wild. The larval production of this species occurred in six (06) tanks - two 200 L and four 600 L. The management of brood stock took place in fresh water, with a ratio of one male to four females. Each fertilized female produced thousands of eggs attached to the abdomen until hatching about two weeks later. The larvae resulting from this reproduction were raised to the post-larval stage in brackish water at a salinity of 15 ppt. The larvae must undergo a molt between each stage. We identified 15 morphological stages between stage 1 and the post-larval stage. The duration from stage 1 until onset of the first post-larval stage in the six (06) tanks was on average 54 days after hatching. The success of larvi culture is defined by the rate of metamorphosis of the larvae into post-larvae, which, in our case, varied between 0.17% and 3.08%, depending on the production tanks, with an average of 2.8%. These results show that the production of M. vollenhovenii in hatchery is possible, presenting a possibility for aquaculture production of this species as well as for biological control against schistosomiasis in a tropical area

Pelagia noctiluca jellyfish: Can lesions and symptoms be prevented or ameliorated?

Objective: Pelagia noctiluca is a very common jellyfish found on European and Mediterranean coasts. Its venom can induce small to severe skin lesions and systemic toxicity. Hypertonicity and modulation of pH could prevent more nematocysts from discharging and relieve symptoms. Methods: This open-label observational study was performed on Mediterranean beaches by rescuers under the authorization of the Ministère de l’Interieur en France (French Ministry of the Interior). Lesions were evaluated for size, general appearance, erythema, pain, and edema. A hypertonic amphoteric solution, Jellywash® solution (Laboratoire Prevor, Valmondois, France), was used for decontamination regardless the delay. Results: 64 victims were exposed to Pelagia noctiluca jellyfish. 78% were > 30 years old, with 27 females and 37 males. 83% of the lesions were small (less than 50 cm2). 78% of the exposed victims were treated within the first 40 minutes. Decontamination had positive results for general appearance in 80% of the victims. Pain decreased in 97% of cases with complete relief in 58% and no effect in 3%. Decontamination was followed by decreased edema in 86% of cases, had a minor effect in 8%, and no effect in 6%. Conclusion: Decontamination with a hypertonic amphoteric solution can potentially help ameliorate or prevent development of lesions and symptoms due to contact with Pelagia noctiluca jellyfish.

Addition of Vertical Enrichment Structures Does Not Improve Growth of Three Salmonid Species during Hatchery Rearing

Environmental enrichment is the placement of structure or other modifications in typically sterile hatchery rearing units.This study investigated the use of vertically-suspended aluminum rod arrays in covered circular tanks on the rearing performance of brown trout (Salmo trutta), Chinook salmon (Oncorhynchus tshawytscha), and Atlantic salmon (Salmo salar) in separate trials lasting 59, 78, and 125 days respectively. No significant differences were observed in gain, feed conversion ratio, individual fish total length, or individual fish weight between the enriched and unenriched treatments in any of the three trials.In addition, vertically-suspended structure had no significant effect on Atlantic salmon relative fin length. These experiments are the first to indicate no benefits during the rearing of salmonids using vertically-suspended enrichment.

Effects of Four Anesthetics, Clove Extract, Thyme Extract, Lidocaine, and Sodium Bicarbonate on the Blood Parameters and Cortisol Amount in Grass Carp (Ctenopharyngodon Idella)

The anesthetic effects of two chemical compounds, lidocaine and sodium bicarbonate, and two natural compounds, clove and thyme extracts, were examined on the Red Blood Cells (RBC), White Blood Cells (WBC), hemoglobin, hematocrit, and blood cortisol levels of Grass carp at two times of 10 minutes and 24 hours after anesthesia. RBC counts had no significant increase in the samples of 10 min and 24 h after induction of anesthesia with clove extract only compared to the control group (p > 0.05). The number of WBC increased significantly in the samples from 10 min and 24 h after anesthesia with sodium bicarbonate only and it was not different from control samples in other treatments 24 h after anesthesia. The amount of hemoglobin indicated an increase with all treatments compared to the control in 10 min after anesthesia. The increases were not significant in thyme and clove extract (P > 0.05). Samples treated at 24h after anesthesia exhibited non statistical hemoglobin elevations with thyme extract only. Hematocrit increased significantly in the samples from 10 min after anesthesia with lidocaine and sodium bicarbonate but, at 24h after anesthesia, hematocrit amount with thyme and clove extracts and lidocaine treatments were not different from the control significantly (P > 0.05). Also, Cortisol level was significantly higher in both sampling times for lidocaine and sodium bicarbonate treatments than the control group. Accordingly, the use of natural anesthetics (thyme and clove extracts) will result in better outcomes than the synthetic compounds (sodium bicarbonate and lidocaine) in the Grass carp.