Sex ratio, gonadal and condition indexes of the Asiatic hard clam, Meretrix meretrix in Marudu Bay, Malaysia

Duisan L, Salim G, Ransangan J. 2021. Sex ratio, Gonadal and Condition indexes of the Asiatic Hard Clam, Meretrix meretrix in Marudu Bay, Malaysia. Biodiversitas 22: 4895-4904. Asiatic hard clam, Meretrix meretrix is one of the important shellfishery resources in Marudu Bay, Sabah, Malaysia. It is among the most popular clam species being widely traded in the local wet markets around Sabah, Malaysia. Unfortunately, the shellfishery management for this species has not been well established. In addition to overexploitation, habitat destruction is also one of the significant threats to this species due to the extensive land use of the coastal areas in Sabah. Hence, conservation and breeding efforts for this species are greatly required. Therefore, the current study was conducted to examine the sexual maturity of the clam with respect to shell length classes for artificial seed production purposes. For this study, a total of 86 clam specimens were randomly collected from mudflats in Marudu Bay. The specimens were utilized for gonad histological and condition analyses. The clams were grouped into three shell length classes; (3.00-4.99) cm, (5.00-6.99) cm, and (7.00-8.99) cm prior to the analyses. Results showed the natural stock of the Asiatic hard clams in Marudu Bay was dominated by females (1.39:1) over males with no hermaphroditism observed. The gonadal index was recorded higher among clams with shell lengths between 5.00 and 6.99 cm. The condition index analysis also recorded high (>4.0) for clams in all the shell length classes. The findings of this study suggest that the clams with shell lengths between 5.00 cm and 7.00 cm are already fully matured and can be utilized as a broodstock candidate for an artificial breeding program in the hatchery.

A comparative study on the effects of ultrasound and some growth factors on somatic embryogenesis and artificial seed production in cucumber (Cucumis sativus L.)

Cucumber (Cucumis sativus L.), a popular vegetable crop of the family Cucurbitaceae, is cultivated in different parts of the world and is of great economic importance. Ultrasound is known as a physical stimulus that can affect living systems. At the right frequency and exposure period, these waves have desired effects. In the present study, 2-week-old plants, were put in an ultrasonic bath with a nominal frequency of 40 kHz, a central frequency of 34/722 kHz and a bandwidth of 320 Hz for 0, 5, 10 and 15 minutes. Hypocotyl pieces were used as explants and cultured in Murashige and Skoog medium supplemented with 0/5 mg/l each of 2,4-dichlorophenoxyacetic acid, 1-Naphthalene acetic acid, kinetin and 6-benzylaminopurine. The use of ultrasonication at a nominal frequency of 40 kHz for 10 minutes showed better results as compared with the samples treated for 0, 5 and 15 minutes, in terms of the shape, maturity of the embryos, and also the germination of artificial seeds and maturing to flowering stage. Since the cucumber of Esfahan is very famous for its aroma and taste and it is somewhat at risk of extinction, we studied the production of artificial seeds of this valuable plant using somatic embryos and apical buds. This research is the first report on investigation of the positive effect of ultrasound on somatic embryogenesis and artificial seed production. our results clearly showed that this method is a practical method to accelerate seed germination and flowering stage.

Investigation of the Factors Affecting Artificial Seed Sowing Success and Seedling Survival in Pinus brutia Natural Stands in Middle Elevations of Central Cyprus

The aim of this study was to analyze the germination of Pinus brutia Ten. seeds, in the field, in relation to factors such as period of sowing, light environment, and watering, in sites of different productivity in the middle elevations in central Cyprus. Two sowing experiments were conducted in three sites of different productivity. In the first experiment P. brutia seed sowing took place in February 2009 in two sowing environments which were gap and under canopy environments. The shade conditions in those environments were determined using hemispherical photographs. Also, the influence of watering on the seed germination was checked. In the second experiment, which was established in the same areas as in the first experiment, the seed sowing took place in December 2009. However, in this case, no watering was applied during the germination period. Moreover, the survival of the seedlings from both sowing periods were monitored up to the end of 2010. During the period of monitoring, the influence of watering was checked. The germination rates of seeds from the February sowing were very low. On the contrary, from the December sowing, the germination rates of seeds were very high in both sowing environments in all studied sites. In the case of seedling survival from the February and December sowing, mortality rates were relatively high in all sites except from the under-canopy sowing environment where watering was applied in the medium productivity site. From the December sowing, from a practical point of view, the number of survived seedlings, in all the plots of the three sites can be considered adequate for the successful regeneration of P. brutia.

Seed production of giant freshwater prawn (Macrobrachium rosenbergii) in Mekong Delta, Vietnam.

Artificial seed reproduction of giant river prawn (Macrobrachium rosenbergii) has been studied in Vietnam since the early 1980s, especially since 1998. Most of this work has been done to obtain suitable broodstock sources, water sources, stocking densities, feed types and rearing scales for different rearing systems. These studies have contributed significantly to the development of prawn seed production technology for commercial practice in Vietnam, especially the Mekong Delta region, which had 91 hatcheries in 2003 compared to only 1 hatchery in 1999. The most popular production system is the modified static green water system, which is used by 88% of the hatcheries in the region. The total production of prawn seed in 2003 was 77.7 million post-larvae (PLs).

Artificial seed production of Pangasiid catfish in the Mekong Delta, Vietnam.

The two pangasiid catfish, Pangasius bocourti and P. hypophthalmus, are widely cultured in the Mekong Delta, Vietnam. However, seed supply until recently was dependent on fry and fingerlings caught from the Mekong River. In 1994, a research programme was carried out on artificial seed production of these two species in captive conditions. In 1995, about 30,000 fingerlings were first produced in An Giang and Can Tho provinces and a proper technique of induced breeding, progressive human chorionic gonadotropin (hCG) treatment, was determined. This technique, involving two steps of hCG injections, successfully induced ovulation in 66% of 67 treated females of P. bocourti. Application of this technique to other pangasiid catfish species such as P. conchophilus, P. hypophthalmus, P. mekongensis, and P. larnaudii also resulted in breeding success. Research on larval rearing has also been conducted to improve the growth and survival of pangasiid larvae. Extension of research findings of induced breeding and larval rearing has allowed mass seed production of pangasiid catfish in the Mekong Delta.

Study on Artificial Seeds of Plants

The establishment and development of artificial seed technology is to quickly reproduce excellent varieties or hybrids, which can be applied to hybrid generation seeds produced by the three-two line method. For some varieties that are difficult to propagate with seeds or plant species with unstable genetic traits and poor fertility, artificial seed technology can also be used for mass reproduction. In particular, some new plants created through genetic engineering, such as somatic hybrids or transgenic plants, can be propagated or maintained by artificial seed technology. In addition, artificial seed technology can be used for the maintenance and rapid propagation of virus-free seedlings. Compared with ordinary test tube seedlings, artificial seeds have low cost, convenient transportation, and to a certain extent reduce vitrified seedlings. In particular, the production of artificial seeds does not occupy a large amount of soil. It can be produced all year round. Therefore, the research on artificial seeds has developed rapidly in the world.