CEI 2010 Research presentations

Group 1 Artificial breeding of horseshoe crabs and conservation

Cheung Tsz Yan, Chu Sing Yung, Ng Yuk Lun, Wong Chun Hei, Wong Ying Chi

Horseshoe crab is the common name of Limulidae. It has its nickname because its prosomatic carapace really looks like a horseshoe. It is a relative of spider and scorpion instead of crab because it has no jaws or antennae. Horseshoe crab is the only surviving member of marine chelicerates in phylum arthropods. Horseshoe crabs have pincer-like limbs and pages-like book-gills. There are six pairs of joined limbs on the ventral side, this shows a similar characteristic among the horseshoe crabs and the spiders and scorpions. (Agriculture, Fisheries and Conservation Department Hong Kong, 2006)

At its prosoma, there is a pair of large compound eyes with large optic nerves on it, thus, they have been used in many eye researches and play a very important role in the study of eyes. At the opisthosoma, there are six pairs of torn gills which look like pages of a book for breathing, and six pairs of joined limbs aforementioned. At the telson, there is a long pointed tail. The tail is important for the survival of this animal as it helps this animal to turn over if it gets upside-down in waves and stranded on a beach.

In this project, fifty horseshoe crabs are artificially bred for six months. By comparing the difference in growth rate between artificial breeding and natural breeding, the advantages and disadvantages of artificial breeding are investigated. In the present study, factors affecting the growth of horseshoe crabs will be explored through continuous measurement on temperature, salinity, dissolved oxygen and NOx values.

Through artificial breeding experiment and literature review, the present study provides a framework for the protection of horseshoe crabs. It is hoped that this study would help conservation and allow a better understanding on the habitat of this valuable marine wildlife.

Group 2 Chinese culture and the extinction of horseshoe crabs

Chan Weng Hong, Lee Ka Yu, Tang Chung Yau, Wong Cheuk Yin

There were over hundreds species of horseshoe crabs living on the Earth for at least 300 million years, long before the dinosaurs appeared. Together with their unchanged basic body structure, they are thus nicknamed ‘living fossils’. However, the number of species has a big decline during the past million years. There are only four species left today, namely Tachypleus gigas, Limulus polyphemus, Carcinoscorpiusrotundicauda and Tachypleus tridentatus.

A number of reasons have resulted in such a great decline. Firstly, coastal development causes loss of nursery grounds. Secondly, serious water pollution results in lower reproduction and survival rates of horseshoe crabs. Lastly, there is over-harvesting of horseshoe crabs as foodstuff for Chinese cuisine, especially for their eggs. Chinese believe that horseshoe crabs are good to health (World Wide Fund, 2006), and it is found that horseshoe crabs are largely fished (Li, 2008).

In the case of Hong Kong, horseshoe crab has also become an endangered species under rapid urbanization. As more mudflats are used for the construction of urban facilities, together with the rapid consumption of horseshoe crabs as foodstuff, these slow-growing species is facing a threat of extinction.

In the current research, we are going to investigate the impact of Chinese culture on the population of horseshoe crabs, as well as the values of horseshoe crabs as a foodstuff and herbal medicine in Chinese culture. Nowadays, many of the horseshoe crab habitats have been damaged by urban development, and the population of horseshoe crabs in Asia is rapidly declining. Through literature review and questionnaire survey, we would like to make a study on the relationship between the extinction of this marine animal and threats resulted from Chinese culture.

We believe that, throughout this project, by raising the awareness of the general public on the ecology and the factors affecting the growth of this animal, its conversation work can be more successful.