In an industrialised mealworm farm it is important to maximise the production and to know the number of mealworms in each container as early as possible in a fast and reliable way. Two experiments were performed. The first experiment assessed the influence of the number of beetles, crate surface area and oviposition time on the number produced mealworms. A full factorial design was used with 11 beetle densities (between 2.3-300 mg beetles/cm2), 5 oviposition times (from 1-14 days) and 4 different crate sizes (between 250-2,000 cm2). In the second experiment, the influence of cannibalism on the number of produced mealworms was assessed via an alternative oviposition method that prohibited cannibalism. Multiple linear regression was used to model the results. The results indicate that the number of beetles, oviposition time and surface area could predict the number of produced mealworms well. An increase in one of the three parameters increased the number of produced mealworms without reaching an optimum. Furthermore, the number of beetles and the oviposition time can be combined in one parameter, beetledays with minimal loss of predictive power of the model. Nevertheless, the number of produced mealworms per female did decline rapidly with increasing oviposition time and density. The latter is, at least in part, due to cannibalism, as the second experiment indicates that the density effect is almost eliminated when the beetles are unable to reach their eggs. In conclusion, this study indicates that it is possible to construct a formula that can be used to a priori determine the final number of produced mealworms based on the number of beetles, surface area and oviposition time and that cannibalism can greatly reduce the number of produced mealworms. Reducing cannibalism can greatly increase the efficiency and therefore production of a mealworm farm.
White discoloration of the tail is a not seldom occurring phenomenon among seahorses kept in ornamental aquaria. In this study, three sea horses (Hippocampus kuda) presenting white patches on the distal part of the trunk and greyish-white necrotic tail tips were examined. Wet mount preparations of these lesions revealed ovoid to elongated ciliated protozoan structures. These ciliates could not be identified to species level but resembled species of the genus Uronema (Scuticociliatida). Samples of the affected skin were inoculated onto Marine agar (Difco) and Flexibacter maritimus medium (FMM, according to Pazos et al., 1996). After 36h of incubation at 25°C, pale orange, convex colonies with a smooth surface appeared on both Marine agar and FMM in all sea horse tails. Gram-staining of these colonies showed Gram-negative, long (up to 8µm in length), slender bacterial cells. Biochemical tests designated these motile bacteria as non-fermenting, oxidase and catalase positive and resistant to the vibriostatic agent 0/129. Sequence analysis of the 16SrRNA gene is on-going. Histological examination of the tail of two animals showed an ulcerative dermatitis consisting of desquamation/disappearance of the epidermis covered with necrotic debris. The latter contained numerous clusters of long (up to 8µm in length) slender bacteria, which were also invading the subcutaneous tissue. At these sites, an increase of proteoglycans, mild proliferation of blood vessels, limited to absent inflammation and invasion was noted. In areas where the epidermis was still intact, neutrophilic pustular lesions without bacterial infiltration were visible. In the third seahorse tail a granulomatous dermatitis was present. Bacteria (including acid-fast bacteria in Ziehl-Neelsen stained histological sections) were not observed. Scuticociliatosis caused by ciliates belonging to the order Scuticociliatida, is recognized as an emerging problem inflicting significant economic losses in aquaculture industry worldwide, for example, in the olive flounder farms in South Korea (Harikrishnan et al., 2010). Heavy infections in Atlantic and Pacific marine fishes kept in aquaria were also reported. The significance of the isolated bacterial strain in the pathology described above remains to be elucidated and will largely depend on its ultimate identification.
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