A University of Maine at Presque Isle Emeritus Professor of Biology and Zoology is working on a manuscript regarding 12 days spent in Japan conducting research with two of his international colleagues. Dr. Stuart R. Gelder is one of the world’s leading researchers of branchiobdellidan annelid, commonly known as crayfish worms. 

Dr. Stuart Gelder, emeritus professor of biology at the University of Maine at Presque Isle

Japan has just one native crayfish, the Zarigani, which is now listed as endangered due in part to increased urbanization and the introduction of North American crayfishes.

Zaragani (YouTube/TheGreenMoj)

Dr. Gelder says Japanese crayfish support 11 species of crayfish worms unique to northern Honshu and Hokkaido futures. The future of those worms is also in doubt.

Gelder and his team collected samples of all the Japanese crayfish worm species so that two particular genes could be sequenced. These data will be used to determine their nearest relatives on the mainland of the China and Korean Peninsula, and then how the various species evolved within Japan.

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Dr. Gelder’s removed live crayfish worms from the crayfish and identified the species under microscope. Each identified species was placed under a dissecting microscope 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. Gelder says 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, he says the process was challenging.

Since the permanently-mounted anterior body contains all the organs needed for species identification, it becomes the permanent reference for the subsequent gene sequences. Gelder says 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 utilized separate individuals, but Gelder says such treatment raises the possibility of introducing errors into the protocol.

Gelder says the current work is the first comprehensive distribution study of native crayfish worms since the Yamaguchi Study in 1934. Initial results found crayfish at a number of sites, but now without worms where previously worms had been reported. The study did not find the cause of the worm disappearances.

Gelder says a typhoon passed over Hokkaido Island while he was in Japan. Although it missed Sapporo, it devastated an area to the southeast, and some of the most productive collecting sites for crayfish were completely washed away, as were their worms. He hopes monitoring the recovery of these areas will provide important information necessary for the development of conservation strategies to protect the symbiosis of this 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.

Stuart Gelder/UMPI

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.

Sapporo University

The research team consisted of Dr. Gelder, Professor Akifumi Ohtaka, a long-time colleague who teaches at Hirosaki University, Aomori Prefecture, in northern Honshu Island, and Professor 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.

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.


Portions of this article were submitted as part of a press release from The University of Maine at Presque Isle. If you would like to share your community news or event with our audience, please email newspi@townsquaremedia.com.