Polyculture of Juvenile Dog Conch Laevistrombus canarium Reveals High Potentiality in Integrated Multitrophic Aquaculture (IMTA)

Laevistrombus canarium, also known as dog conch, is a marine gastropod mollusk widely distributed in the Indo-Pacific region. It is an economically crucial species; however, its population has been declining due to overfishing and overexploitation. In this study, the suitable salinity for juvenile L. canarium was between 20 and 35‰. Diatoms and biological detritus by using flow-water from the fish pool were the most favorable diets for newly metamorphosed and 10 mm juveniles. In the polyculture experiment, L. canarium was cultured with whiteleg shrimp, tilapia, small abalone, purple sea urchin, and collector urchin. Better growth was found in all co-culture groups except with whiteleg shrimp. We also found that the polyculture system with or without substrates significantly affected the growth of juveniles. Additionally, we observed that water temperature was the most crucial factor for growth and survival; a water temperature of less than 10 °C might cause the death of L. canarium. We have proposed a novel polyculture and water-flow method for mass production of L. canarium and evaluated the feasibility and benefits of polyculture with other species. The findings from this work reveal the potentiality of L. canarium in integrated multitrophic aquaculture (IMTA) and its implication for aquaculture and resource restoration.

First Report on the Diversity of Epizoic Algae in Larval of Shellfish Gastropod Aliger gigas

Epibiosis occur frequently on the shells of some marine crustaceans, which often serve as substrate for various species of algae, there is few information on the associations between these. The objective of this study was to determine if the gastropod mollusk Aliger gigas (formerly Lobatus gigas) in larval had some sort of the association with algal. To the above was carried out collecting egg masses in the environment, the larvae were cultivated in seawater filtered 5 μm. The algal material found was observed in electron microscopy, for its identification and quantification. We analyzed 60 larvae aged 2–44 days for analyzing the structure of the shell and its epibionts. Of the larvae analyzed, 50 larvae presented epizoic. The algae community consisted of 28 taxa, and composed of 25 diatoms (Bacillariophyta) and three cyanophytes (Cyanobacteria). The H´ diversity values fluctuated between 0.2 a 1.2. The dominant and frequent species were formed by diatoms: Nitzschia panduriformis var. minor, Halamphora sp. and Cyclophora sp.

Light-insulating apparatus of the camera-like eye of the terrestrial gastropod mollusk Arion rufus (Heterobranchia, Stylommatophora)

The cellular composition, the morphology of the components, and the screening function and evolutionary changes of the light-insulating apparatus of the camera-like eye of the terrestrial gastropod pulmonate mollusk Arion rufus were studied and evaluated using light and electron microscopy. According to all the considered characteristics, the light-insulating apparatus of A. rufus is typical for terrestrial pulmonate mollusks. Evolutionary transformations of the light-insulating apparatus, caused by the change in the mollusks' environment, are insignificant and affect the cellular composition, the morphology of pigmented cells and the isolation of the light-sensitive parts of photoreceptor cells from each other.