A Study of the Morphological and Histological Structure of the Caudal Fin of the Female Swordtail Fish Xiphophorus helleri and the Effect of Hydrocortisone on it

The caudal fin is one of the most important types of fins used in the movement of fish and is important in studying the effect of various factors on bone, especially medicines and drugs. The females of the Xiphophorus helleri were obtained from aquarium fish shops. The mature females were divided into two groups, each containing 14 fish, placed in 60 liter glass aquarium, the first group treated as control group, while the second group was treated with Hydrocortisone Sodium Succinate (Roxcortisone) with a concentration of 2.5 mg/1. After a month of experimentation, the samples were fixed by a Formalin 10% in order to prepare them for the whole-mount loading method and the normal tissue sections. The results of the phenotypic study of the caudal fins of female X. helleri showed that they consist of three types of fin rays, which are unsegmented and unbranched, segmented and unbranched,  and segmented and branched. These three types differ in terms of shape and structure , as histological structures showed that the first type rays, i.e.  unsegmented and unbranched, and the first ray of the second type, i.e. segmented and unbranched, have pear shaped. The cavity between the two halves of rays is filled with connective and neural tissue, while the other rays of second type have a heart shape and  filled with  muscle tissue. The shape of the  third type, i.e. segmented and branched, varies depending on their location in the fin. The results of the study of  morphological of the caudal fin of females treated with hydrocortisone showed that there was an irregularity in the fin rays in general, which led to a difference in the branching positions of the branched rays compared to the control group. It was also noticed that there was a fusion in the rays composing the fin and another fusion of internodes composing the one fin in comparison to control group. Keywords: Xiphophorus helleri, caudal fin ,fin rays ,hydrocortisone hormone DOI: 10.7176/JNSR/9-4-0

Digitalization of learning in Saudi Arabia during the COVID-19 outbreak: A survey

Following the outbreak of the novel coronavirus (COVID-19) in China in late December 2019, more than 217 countries became almost immediately infected in the resulting pandemic. Consequently, many of them decided to close their educational institutions as a way of preventing the spread of this virus. For many of them, though, the closure made them unable to deliver learning materials to students owing to their inability to provide the right technology for the purpose. To assist with the digitalizing of learning during this time, this study reviews the most common technologies used in the delivery of learning materials, with the experience of most infected countries being considered. Major challenges in online learning are discussed in this study as well. Further, Saudi Arabia was considered as a case study for the effectiveness of distance learning during the 2020 spring semester, where 300 undergraduate students were surveyed on their opinions of distance learning. The responses to the survey indicated that distance learning was effective in providing the required knowledge to the students during the outbreak of COVID-19. The findings showed that although the lack of interaction and poor internet connections were factors affecting comfortable and successful learning of physics and mathematics, 63% of students were satisfied with learning management systems, 75% of students found it easy to understand course materials, and 67% of students found it easy to understand assignments and could deal with them comfortably. The study findings can encourage educational institutions to digitalize their learning materials in the future