Reproduction efficiency of the Horse Leech,Haemopis sanguisuga (Linnaeus, 1758)

The aquaculture sector has recently focused on alternative food sources due to increased costs and limited resources. Live food sources, such as invertebrates, have important roles in digestion processes of fish. It was aimed to determine the reproduction efficiency of the horse leech, Haemopis sanguisuga, which is expected to be used as an alternative live nutritional source in aquaculture in this study. The study was conducted at ambient temperature in the laboratory conditions for three months. A total of 25 gravid leeches with an average body mass of 6.91 ± 2.20 g were used. The leeches lost up to 75% of their body mass and laid 4.30 ± 1.49 cocoons at 12.0 ± 8.2 days interval during cocoon laying period. Leeches stopped laying cocoon when the temperature fell to 16 °C. The average of offspring hatched from the cocoons was 6.45 ± 2.86. The length–body mass relationship of the offspring was exponential (W = 0.012L^2.809, R² = 0.898). The results from the current study indicate that the basic biological parameter affecting the reproduction efficiency of H. sanguisuga is the size of the broodstock leeches, and reproduction activity weakens the broodstocks.     

A design-oriented STEM activity for students’ using and improving their engineering skills: the balance model with 3D printer

Abstract

This study involves the development and implementation of a STEM activity containing 3?D printer technology, which is commonly used in STEM education. Out of school STEM courses were organized with seven middle school students studying in the 7th grade and the activities in the course were carried out with a 3D printer. One of the activities in the course is the Balance model. The study reveals the skills students used in the Balance Model activity, which is a 3D STEM activity. The students’ engineering skills were effective through the STEM activity, and they actively used skills such as planning, designing, explaining the design process, creating a realistic product, and testing and evaluating product performance. In addition, it was concluded that the students use their academic and technical skills effectively. The study presents in detail the preparation and implementation process of this activity, which we think may help educators uncover and improve students’ engineering skills.