Dr. Stuart R. Gelder, Emeritus Professor of Biology at the University of Maine at Presque Isle, recently spent 12 days in Japan conducting research with two of his international colleagues. Dr. Gelder is one of the world’s leading researchers of branchiobdellidan annelid (crayfish worms).
The research team consisted of Dr. Gelder, Prof. Akifumi Ohtaka, a long-time colleague who teaches at Hirosaki University, Aomori Prefecture, in northern Honshu Island, and Prof. Itsaru Koizumi, at Sapporo University, Hokkaido Prefecture, Japan. Dr. Gelder’s visit was supported by a grant from the Watershed Ecology Research Fund of Japan, to Prof. Ohtaka.
Japan has one native crayfish and that is now listed as endangered due in part to increased urbanization and the introduction of North American crayfishes. Japanese crayfish support 11 species of crayfish worms unique to northern Honshu and Hokkaido, whose futures are also in doubt. The current project was designed to collect samples of all the Japanese crayfish worm species so that two particular genes could be sequenced. These data will be used to ascertain their nearest relatives on the mainland (China and Korean Peninsula) and then how the various species evolved within Japan.
Dr. Gelder’s contribution was to remove live crayfish worms from the crayfish and identify the species by taking a semitransparent individual and examining it under a microscope at 200x magnification. The slide with an identified individual was placed under a dissecting microscope (10x) and the specimen flooded in 70% ethanol. Before the ethanol evaporated, the posterior third of the body was severed with a scalpel, and transferred with very fine tweezers to a plastic vial for subsequent molecular sequencing. The anterior portion was transferred into a separate vial for later mounting onto slide as a permanent preparation.
As some of the specimens were about a millimeter long, the process was challenging. The permanently mounted anterior body contains all the organs needed for species identification and it becomes the permanent reference for the subsequent gene sequences. This method, developed by Dr. Bronwyn W. Williams of the North Carolina Museum of Natural History, Raleigh, NC, is not often used because of the smallness of the worms. Many other studies on similar sized organisms prefer to use separate individuals, but this raises the possibility of introducing errors into the protocol.
In addition, collections made for this study have provided valuable information on the distribution of these worms. The current work is the first comprehensive distribution study of native crayfish worms since the published work of Prof. Yamaguchi in 1934. Initial results found crayfish at a number of sites but without worms, where previously they had been reported. Dr. Gelder explained that no reasons for these absences are apparent at the moment.
During Dr. Gelder’s visit, a typhoon passed over the island. Although it missed Sapporo, it devastated an area to the southeast where some of the most productive collecting sites for crayfish and their worms were completely washed away. Dr. Gelder said that monitoring the recovery of these areas will provide important information necessary for the development of conservation strategies to protect this important symbiosis of native species.
Dr. Gelder was invited to present a research seminar on crayfish worm biology to biology and environmental graduate students at Sapporo University. A crayfish expert and long-time colleague, Dr. Tadashi Kawai, of Wakkanai Fisheries Experimental Station in Hokkaido, also arranged for a presentation entitled, “Friends of Crayfish” to the Hokkaido Prefecture conservation group, which is part of the Ministry of Land, Infrastructure, Transport and Tourism.
Dr. Gelder’s visit to Japan provided an opportunity for him and Dr. Ohtaka to discuss the latest draft of a manuscript describing the first record of a North American crayfish worm and other invasive species in Japan. This manuscript will be submitted to an international peer-reviewed journal for publication by the end of the year.
Photo description: Pictured is the introduction slide to Dr. Gelder’s power point presentation given in Sapporo, Japan, featuring the Japanese crayfish worm, Cirratodrilus cirratus Pierantoni, 1905. This was the first species to be described from East Asia. The specimen shown was collected by Prof. M. Yamaguchi in 1932 and deposited in ethanol in the Hamburg Museum, Germany. It survived the Hamburg firestorm in World War II and was placed in the archives of the rebuilt Museum. It was recognized by Dr. Gelder in 1985 during his visit to the museum, which was part of the 3rd International Symposium of Aquatic Oligochaetes. Three specimens were brought back to UMPI; one was made into a permanent slide mount and the other two were sectioned. The results provided the first detailed description of the internal anatomy of the species and were published in the symposium proceeding. The slides were then returned to the Hamburg Museum.