Proceedings of the XIIth International Symposium on Trichoptera, June 18-22, 2006, Bueno-Soria, J., R. Barba-Álvarez, and B. Armitage (Editors), pp. 279-284. 2007 The Caddis Press. Further studies on caddisflies (Insecta: Trichoptera) collected from the Bonin Islands and the Izu Archipelago, Japan KIYOSHI SATAKE 1* AND RYOICHI B. KURANISHI 2* 1 National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan; 2 Natural History Museum and Institute, Chiba 260-8682, Japan Abstract. Further studies on the caddisfly fauna were conducted in the streams of the Bonin Islands and the Izu Archipelago, Japan during 2004-2005. As a result, eleven species belonging to nine families were identified, and besides many groups typically found in the main island of Japan are missing in these oceanic islands. Distributions of Rhyacophila shikotsuensis and Scelotrichia ishiharai were confirmed at Mikura-jima, the Izu Archipelago for the first time. As for the Bonin Islands, even though an immature Rhyacophila larva was recorded, its taxonomic status and origin is still uncertain. On the other hand, the endemic species Goera ogasawaraensis showed a decline in its larval densities, compared with previous study; however the decline could be ascribed to impacts such as disturbance on stream-bed surfaces, draughts and predation by alien lizards. Key words: Trichoptera, Bonin Islands, Izu Archipelago, Japan. Introduction The Bonin Islands and the Izu Archipelago are oceanic islands located south of the main island of Japan (Fig. 1). The former are Tertiary submarine volcanic origin, and the latter are Quaternary volcanic origin. Most of the land of these oceanic islands is designated as protected area of National Parks. In our previous study (Satake et al. 2005), twelve species of caddisflies belonging to ten families were recorded from the Bonin Islands and the Izu Archipelago, Japan, during 1991-2001. Some of the species collected from the Izu Archipelago are conspecific with those of the main island of Japan; nevertheless Goera ogasawaraensis collected from the Bonin Islands was an endemic species. Methods and Study Sites Samplings of freshwater macro-invertebrates, particularly caddisflies, were conducted in the streams of Mikura-jima, the Izu Archipelago, on October in 2004 and also in the streams of the Bonin Islands (Chichi-jima, Ani-jima and Haha-jima) on June, July, October and December in 2005 and on February in 2006, to clarify the taxonomic position of the species identified to generic level in our previous study (2005), such as Rhyacophila sp. and Scelotrichia sp., and to confirm the conservation status of the endemic species, G. ogasawaraensis. Each of field samplings was subjected to the laws and regulations, such as the National Parks Law. Specimens of caddisfly larvae and pupae were collected with D-frame nets of mesh size 0.5 mm. Specimens of caddisfly adults were collected by sweeping and with light traps. Collection sites of Trichoptera on each island are shown in Fig. 2. Mikura-jima This island is located 200 km south of Tokyo. It has an area of 20.6 km 2 and its highest point rises to 850.9 meters. Mikura-jima is a volcanic island, with a population of ca. 300 people. All the area of this island belongs to Fuji-Hakone-Izu National Park. Mk-5a: Headwaters of Ohshimawake-gawa, (33 o 52 43 N, 139 o 36 47 E), 380 m a.s.l. Mk-6: Upper reaches of Ohshimawake-gawa, (33 o 53 06 N, 139 o 37 07 E), 180 m a.s.l. Mk-16: A small stream north of the Ebine Park, (33 o 52 01 N, 139 o 35 19 E), 510 m a.s.l. Mk-17: A small stream south of the Ebine Park, (33 o 51 59 N, 139 o 35 21 E), 520 m a.s.l. 279
SATAKE AND KURANISHI island is an uninhabited island located approximately 1040 km south of Tokyo. The island is made of submarine volcanic products. All the area of Ani-jima belongs to Ogasawara National Park. Cz-1: A stream of Takino-ura Bay, (27 o 07 04 N, 142 o 12 31 E), 20 m a.s.l. Cz-2: A stream of Mansaku-hama Beach, (27 o 06 44 N, 142 o 13 09 E), 10 m a.s.l. Haha-jima The name of this island has a meaning of the island of mother in Japanese, probably because it is the second largest island in the Bonin Islands. Haha-jima has an area of 20.8 km 2 and its maximum altitude is 462.6 meters. This island is located approximately 1100 km south of Tokyo, with a population of ca. 450 people. The island is made of submarine volcanic products. About three quarters of the area of Haha-jima belongs to Ogasawara National Park. Ha-3: Upper reaches of Nagahama River, near Nagahama Bridge, (26 o 40 25 N, 142 o 09 00 E), 130 m a.s.l. Ha-9: Upper reaches of Chibusa Dam, (26 o 38 54 N, 142 o 09 45 E), 85 m a.s.l. Figure 1. Map around Japan, showing the locations of the Izu Archipelago and the Bonin Islands. Chichi-jima The name of this island has a meaning of the island of father in Japanese, probably because it is the largest island in the Bonin Islands. Chichi-jima has an area of 24.0 km 2 and its maximum altitude is 326.0 meters. This island is located approximately 1050 km south of Tokyo, with a population of ca. 1900 people. The island is made of submarine volcanic products. About three quarters of the area of Chichi-jima belongs to Ogasawara National Park. Ch-1: Upper reaches of Okumura-gawa, (27 o 05 57 N, 142 o 12 41 E), 50 m a.s.l. Ch-2: A head-water stream of Yasse-gawa, (27 o 03 55 N, 142 o 13 08 E), 210 m a.s.l. Ch-13: Tokoyo Fall, (27 o 03 27 N, 142 o 12 21 E), 10 m a.s.l. Ch-17: A head-water stream of Naka-kaigan Coast, (27 o 03 03 N, 142 o 12 46 E), 190 m a.s.l. Ch-18: A stream of Higashi-kaigan Coast, (27 o 03 47 N, 142 o 13 30 E), 175 m a.s.l. Ch-23: A stream of Tenno-ura Bay, (27 o 02 34 N, 142 o 13 10 E), 100 m a.s.l. Ani-jima The name of this island has a meaning of the island of elder brother in Japanese. Ani-jima has an area of 7.9 km 2 and its maximum altitude is 253.9 meters. This Results The arrangement of families follows Wiggins (1996), and genera and species are arranged alphabetically within each family. Material which was only identified to generic level was nevertheless treated as individual species. Collector s name is abbreviated as follows: KS; Kiyoshi Satake. In the following list, eleven species are recorded from the Bonin Islands and the Izu Archipelago. These are classified into nine families as follows. A single species was recorded for each of the Glossosomatidae, Philopotamidae, Psychomyiidae, Lepidostomatidae, Apataniidae, Goeridae and Helicopsychidae, and two species were recorded for the Rhyacophilidae and Hydroptilidae. The materials collected by KS are deposited in the National Institute for Environmental Studies, Tsukuba (NIES), unless otherwise stated. The other materials are deposited in the Natural History Museum and Institute, Chiba (CBM). Suborder Spicipalpia Family Rhyacophilidae 1. Rhyacophila shikotsuensis Iwata, 1927 Material examined. Mk-5a, one male and seven 280
Further studies on caddisflies collected from the Bonin Islands and the Izu Archipelago, Japan Figure 2. Maps of islands with study sites and contour lines. Jima means island in Japanese. larvae, 14.X.2004, KS leg.; Mk-6, five larvae, 12.X.2004, KS leg. Distribution. Izu Archipelago (Mikura-jima), Hokkaido, Honshu, Shikoku, Kyushu, Okinawa, Kuril Islands (Kunashir). Remarks. In a previous study (2005), four Rhyacophila larvae were collected from the same stream of Mikurajima. Taxonomic position of Rhyacophila shikotsuensis is confirmed by morphological observation of a male adult collected in this study. At present, the distribution of R. shikotsuensis in this island is restricted to Ohshimawakegawa, which originates from a spring and is one of the largest streams in the island. 2. Rhyacophila sp. Material examined. Ha-9, one larva, 18.VI.2005, KS leg. Description. CBM-ZI 131743. An immature larva. Body length: 4.8 mm. Head length (HL): 0.76 mm. Head width (HW): 0.47 mm. HL/HW: 1.61. 281
SATAKE AND KURANISHI Ground color of sclerites on body reddish brown to brown. Head with black spots on postero-lateral corners, without distinct dot on dorsum (Fig.3A). Pronotum with black posterior margin (Fig.3B). Fore legs slightly darker than other legs. Head oblong, setae FC6 and P1 longer and seta A2 a little longer than others. Labrum rounded at anterior margin. Thorax without gill. Pronotum with anterior margin slightly wider than the posterior, similar length of four long setae on dorsum. Fore leg short and massive, tibia with short and thick, spine-like, posterior disto-ventral seta (Fig.3C). Mid and hind legs slender. Abdomen without gill. Anal proleg with a dark brown dorsal hump on postero-dorsal corner; anal claw with a black hump at basodorsal corner, without ventral tooth (Fig.3D). Remarks. In this study, a Rhyacophila species was recorded from the Bonin Islands for the first time. On the occasion of finding, an immature larva was collected from a rapid of a swiftly flowing small stream approximately 1 km north of Oki-mura Village, which is the only village inhabited by people at present in Haha-jima. In spite of our efforts to identify this larva, the taxonomic position of the larva is still uncertain. As for whether this species is indigenous species or not, it is a controversial issue. Further investigations are needed. Family Hydroptilidae 3. Scelotrichia ishiharai Utsunomiya, 1994 Material examined. Mk-5a, four pupae and one larva, 14.X.2004, KS leg.; Mk-6, one male and one female, 14.X.2004, KS leg. Distribution. Izu Archipelago (Mikura-jima), Hokkaido, Honshu, Shikoku, Kyushu. Remarks. In a previous study (2005), three final-instar larvae of Scelotrichia sp. were collected from the same Figure 3. Larva of Rhyacophila sp., A, head, dorsal; B, pronotum, lateral; C. fore leg, lateral; D. anal proleg, lateral. 282
Further studies on caddisflies collected from the Bonin Islands and the Izu Archipelago, Japan stream of Mikura-jima. The taxonomic position of Scelotrichia ishiharai is confirmed by morphological observation of a male adult collected in this study. The distribution of S. ishiharai in this island is restricted to Ohshimawake-gawa, which is one of the largest streams in the island. 4. Hydroptila sp. Material examined. Ch-1, 12 pupae and 85 final instar larvae, 27.VI.2005, KS leg.; two females, 1.VII.2005, KS leg.; Ch-2, two males and ten females, 28.X.2005, KS leg.; 12 females, 9.XII.2005, KS leg.; 13 males, 19.II.2006, KS leg.; Ch-13, one male and two females, 27.X.2005, KS leg.; Ch-17, two cases, 28.VI.2005, KS leg.; Ch-18, one pupa and one young larva, 27.VI.2005, KS leg.; Ch-23, ten final instar larvae, 28.VI.2005, KS leg.; Cz-1, four cases, 23.VI.2005, KS leg.; Cz-2, two larvae, 23.VI.2005, KS leg.; Ha-3, one larva, 17.VI.2005, KS leg. Distribution. Bonin Islands (Chichi-jima, Ani-jima, Haha-jima). Remarks. Although the morphological observations of both males and females of this species were conducted, the taxonomic position of the species is kept uncertain until morphological comparison with its closely related species is completed. Further investigations are needed. Family Glossosomatidae 5. Glossosoma sp. Material examined. Mk-6, one larva, 12.X.2004, KS leg. Suborder Annulipalpia Family Philopotamidae 6. Chimarra sp. Material examined. Mk-6, one larva, 12.X.2004, KS leg.; Mk-16, one larva, 14.X.2004, KS leg. Family Psychomyiidae 7. Psychomyiidae gen. sp. Material examined. Mk-17, one larva, 13.X.2004, KS leg. Suborder Integripalpia Family Lepidostomatidae 8. Lepidostoma japonicum (Tsuda, 1936) Material examined. Mk-5a, one case, 14.X.2004, KS leg.; Mk-16, one male, two females and two larvae, 14.X.2004, KS leg.; Mk-17, one male and ten larvae, 13.X.2004, KS leg. Distribution. Izu Archipelago (Kouzu-shima, Mikurajima, Hachijyo-jima), Hokkaido, Honshu, Sado, Kyushu, Yaku-shima. Family Apataniidae 9. Apatania sp. Material examined. Mk-5a, one larva, 14.X.2004, KS leg.; Mk-17, five cases, 13.X.2004, KS leg. Family Goeridae 10. Goera ogasawaraensis Kuranishi, 2005 Goera sp., Tomokuni and Sato, 1978, 117-118, larvae and case. Goera ogasawaraensis, Satake et al., 2005, 378-379, male and female. Material examined. Ch-17', one larva, 28.VI.2005, KS and T. Sasaki leg.; Cz-2, one larva, 23.VI.2005, KS leg. Distribution. Bonin Islands (Chichi-jima, Ani-jima). Remarks. According to our previous study (Satake et al. 2005), the mean density of the larvae including the pupae of Goera ogasawaraensis in three headwater streams of Chichi-jima during 1998-2000 was estimated as ten individuals per square meters; however the density declined to zero in either of these streams during the study period. In addition to this decline, the aggregation of pupae of G. ogasawaraensis observed by Dr. Miyano in 1991 (Satake et al. 2005) was not confirmed during the study period. Meanwhile one larva was collected from the other headwater stream located in southeastern part of Chichi-jima and one larva was also collected from a stream of Ani-jima. At present, the area of occupancy seems to be declined in Chichi-jima. Possibly several impacts account for this decline in larval densities and area of occupancy of G. ogasawaraensis. The disturbance on stream-bed surfaces could eliminate suitable habitats for aquatic insects like G. ogasawaraensis. Actually, in the Okumura-gawa, which is one of the previously known localities, the landslide 283
SATAKE AND KURANISHI sand and rocks associated with large woody debris had filled up the part of stream bed. As headwater stream flows on the Bonin Islands are supported by precipitation, the changes in patterns of precipitation such as droughts can have an adverse effect on stream biota. Oka et al. (2000) calculated the water balance of Chichi-jima with local climatic data from 1907 to 1943 and from 1970 to 1999. They concluded that the late 1900s were drier than the first half of the century, resulting from both warmer air temperature and less precipitation during the late 1900s. In addition to this, the annual precipitation in 2004 was as low as 900mm in Chichi-jima. In the Bonin Islands, a catastrophic decline in native insect fauna was observed recently (Karube, 2004). Karube and Suda (2004) speculated that predations by an invasive alien lizard, Anolis carolinensis unintentionally introduced from the Guam to Chichi-jima in the 1960s caused such a decline, because the decline was coincident with the range expansion of this Anolis lizard to whole the area of Chichi-jima and Haha-jima. As aquatic insects like dragonflies and damselflies were also eliminated in these two islands occupied by the alien lizard (Karube, 2004), the adults of G. ogasawaraensis would be also fed by the lizard. Kanagawa Prefectural Museum Natural History 12: 31-45 (in Japanese.) KARUBE, H. AND S. SUDA. 2004. A preliminary report on influence of an introduced lizard, Anolis carolinensis on the native insect fauna of the Ogasawara Islands. Research Report of the Kanagawa Prefectural Museum Natural History 12: 21-30 (in Japanese.) OKA, S., K. YOSHIDA, H. IWASHITA, Y. IIJIMA, AND T. SATOH. 2000. Interannual variability of hydroclimatic environment, based on the water balance at Chichijima Island in the Bonin (Ogasawara) Islands, Ogasawara Research 26: 15-33. SATAKE, K., R.B. KURANISHI, AND R. UENO. 2005. Caddisflies (Insecta: Trichoptera) collected from the Bonin Islands and the Izu Archipelago, Japan. Pages 371-381 in K. Tanida and A. Rossiter (editors). Proceedings of the 11th International Trichoptera Symposium (2003), Sakai, Osaka and Kutsuki, Shiga, Japan, Tokai University Press, Kanagawa. TOMOKUNI, M. AND M. SATO. 1978. Aquatic and semiaquatic insects of the Bonin Islands (including the Volcano Islands). Memoirs of the National Science Museum 11: 107-121 (in Japanese with English description and summary). WIGGINS, G.B. 1996. Larvae of the North American Caddisfly Genera (Trichoptera), Second Edition. University of Toronto Press, Toronto. Family Helicopsychidae 11. Helicopsyche sp. Material examined. Mk-5a, one case, 14.X.2004, KS leg.; Mk-16, two cases, 14.X.2004, KS leg.; Mk-17, one case, 13.X.2004, KS leg. Acknowledgement The first author would like to thank Mr. Ryuhei Ueno, NIES, for his encouragement and support during the study, Dr. Kazuo Horikoshi, Mr. Hajime Suzuki and Mr. Tetsuro Sasaki, Institute for Boninology, for their help and guidance in Chichi-jima, and Dr. Haruki Karube, Kanagawa Prefectural Museum of Natural History, for his help and guidance in Ani-jima. This study is partially supported by JSPS Grant-in-Aid No. 16510180 and No.17510200. Literature Cited KARUBE, H. 2004. The present situation of the endemic dragonflies in the Ogasawara Islands When and why have they declined-, Research Report of the 284