Cambaroides Japonicus Research Articles

Cheliped Loss of the Japanese Crayfish, Cambaroides japonicus in a Stream and a Lake in Hokkaido, Japan

Cheliped Loss of the Japanese Crayfish, Cambaroides japonicus in a Stream and a Lake in Hokkaido, Japan

Genetic Identification of Mammalian Carnivore Species in the Kushiro Wetland, Eastern Hokkaido, Japan, by Analysis of Fecal DNA

To identify mammalian carnivore species distributed in the Kushiro Wetland, eastern Hokkaido, Japan, we developed molecular-genetic methods for identification of the species from fecal samples collected from the field. Species-specific primers and PCR programs were established for five native and six alien species of carnivores: Martes zibellina, Mustela nivalis, Mustela erminea, Vulpes vulpes, and Nyctereutes procyonoides as native species, and Neovison vison, Martes melampus, Mustela itatsi, Canis familiaris, Felis catus, and Procyon lotor as alien species in Hokkaido. Touchdown PCR, in which the annealing temperature is decreased 1 degrees C every cycle, was more effective for some species from which fecal DNA was not amplified species-specifically with standard PCR programs. Of 405 fecal samples collected from the Kushiro Wetland, the species of origin of 246 samples were successfully identified: 88 samples for N. vison, 140 for M. zibellina, 13 for V. vulpes, four for C. familiaris and one for F. catus. The results show the particular applicability of this method to monitoring M. zibellina and N. vison. In addition, methods to PCR-amplify DNA from two crayfish species (Pacifastacus leniusculus and Cambaroides japonicus) were developed to determine whether the carnivore fecal samples contained detectable DNA from the prey crayfishes. DNA from P. leniusculus was amplified from feces of N. vison identified in the present study, but no DNA from C. japonicus was detected. This indicates that N. vison preys on the alien species P. leniusculus.

Endangered crayfish in northern Japan: Distribution, abundance and microhabitat specificity in relation to stream and riparian environment

Japan’s only native crayfish species Cambaroides japonicus has been declining dramatically in the past few decades. For the purpose of conservation planning, twenty-two coastal streams were surveyed to investigate summer distributions of crayfish in relation to stream and riparian environment. Classification and regression trees were used to predict the occurrence and abundance of crayfish. The classification tree model with stream variables as predictors showed that crayfish would occur in swift or high gradient streams (correct classification rate = 91%). Within those streams, however, crayfish only inhabited depositional microhabitats, in which the areas are limited in availability. Crayfish were not found in gentle, low gradient streams containing abundant depositional microhabitats. This paradoxical distribution pattern was attributed to availability of boulder substrates in swift or high gradient streams. The regression tree model indicated that crayfish abundance was determined primarily by the percentage of boulder substrates and the presence of fish (observed vs. predicted r = 0.64). The classification tree model using only riparian variables indicated that the total woody plant (mainly broadleaf species) density followed by the percentage of early successional species such as alder and willow determined the splits of the tree model (correct classification rate = 95%). A leaf processing experiment on 10 riparian plant species suggested that crayfish preferred high nitrogen (or low C/N) leaves. These results suggest that swift or high gradient fishless streams associated with abundant cover in dense broadleaf forest serve conservation areas for this endangered crayfish, and that consideration of riparian composition may facilitate conservation efforts.

Alien vs. endemic crayfish: roles of species identity in ecosystem functioning

In northern Japan, an alien crayfish species (signal crayfish; Pacifastacus leniusculus) is replacing Japan's only native crayfish species (Cambaroides japonicus) that is endemic to the country. We tested experimentally if these two crayfish species had similar roles in terms of ecosystem functioning in stream habitats. Experiments were performed to examine the impacts of alien and endemic crayfish on detritus-based food webs. During the experiment, neither crayfish species affected rates of breakdown of microbially conditioned oak leaves. In contrast, the amphipod Jesso-gammarus jesoensis, which dominated the non-crayfish invertebrate biomass, was significantly reduced in the presence of the two crayfish species. Thus, effects of crayfish on leaf breakdown were probably masked by the leaf processing activities of these large amphipods in the absence of crayfish. Overall, per-unit biomass impacts of Pacifastacus on leaf processing and invertebrate colonisation of leaves were comparable to those by Cambaroides. Laboratory experiments were performed to test whether rates of leaf processing of 10 riparian plant species, particulate organic matter (POM) production and nutrient excretion differed between crayfish species in the absence of other invertebrates. Although POM production rates did not differ between crayfish species, crayfish impacts on leaf processing differed depending on plant species reflecting differential leaf preference. Comparisons of individual nutrient excretion rates revealed that ammonia and phosphate excretion rates were higher in Cambaroides compared with Pacifastacus. Further, ammonia excretion rates were proportional to crayfish biomass in Cambaroides but not in Pacifastacus. Taken together, the two crayfish species had similar roles in stream food webs when biomass was similar. However, their roles as leaf processors and excretion rates of nutrients differed when there was a choice among different riparian species as sources of leaf litter. Species replacement between alien and endemic crayfish may therefore result in differential consequences for ecosystem processes.

移入種ブラウントラウトが淡水産甲殻類に及ぼす影響:絶滅危惧種ニホンザリガニへの捕食

移入種ブラウントラウトが淡水産甲殻類に及ぼす影響:絶滅危惧種ニホンザリガニへの捕食

Asymmetry in Mutual Predation between the Endangered Japanese Native Crayfish Cambaroides Japonicus and the North American Invasive Crayfish Pacifastacus Leniusculus: A Possible Reason for Species Replacement

Asymmetry in mutual predation can be important in species replacement between native and invasive species. Mutual predation between the endangered Japanese native crayfish species Cambaroides japonicus and the North American invasive crayfish Pacifastacus leniusculus was studied to assess the potential impact of P. leniusculus on C. japonicus. We made laboratory experiments to examine mutual predation (i) between individuals in pairs of the same and different species and (ii) among a group comprising single and mixed species. We also made field surveys to clarify the frequency of cannibalism of the two species. In laboratory experiments, the frequency of cannibalism was low by both two species, but predation by P. leniusculus on C. japonicus was severe and most P. leniusculus survived both in different species pairs and in mixed species groups. In field surveys, remains of the two crayfish species, which may have been caused by predation by the same species, i.e., cannibalism, were scanty. The results suggest that asymmetry in mutual predation can be an important cause of species replacement of the native C. japonicus by the invasive P. leniusculus in the field.

Fecundity of the Japanese crayfish, Cambaroides japonicus: ovary formation, egg number and egg size

Ovary formation, egg number and egg size was studied to examine the fecundity of the Japanese crayfish Cambaroides japonicus. From histological observations of ovaries, the ovarian eggs of C. japonicus developed as asynchronous oocytes. Many well-grown oocytes were in the ovary after spawning, as well as before spawning. The smallest carapace length of ovigerous females was 15.2 mm. The pleopodal egg number ranged from 22 to 75 and significantly increased with female body size. Both egg diameters (2.13–2.50 mm) and weights (0.009–0.017 g) also significantly increased as the female body size increased, but were variable even for the same size crayfish. We conclude that larger females should be used for seed production of C. japonicus because of its high fecundity and large eggs. Mature females spawn only once a year in natural habitats, but multiple spawning can be artificially induced within 1 year because of well-grown oocytes that remain in the ovary after spawning. Thus, we recommend that an effective technique for artificial induction of multiple spawning be developed from our results.

Reproduction of the Alien Crayfish Species Pacifastacus Leniusculus in Lake Shikaribetsu, Hokkaido, Japan

The reproduction of the alien crayfish species Pacifastacus leniusculus inhabiting Lake Shikaribetsu, Hokkaido, Japan, was studied from August 2002 to August 2003. Spawning was for a short period after mating in mid October. The eggs developed to eyed stage in June the following year and hatched in mid July. After remaining with their mother for several weeks, the juveniles became independent between late July and August. The egg numbers attached to pleopods of this crayfish significantly increased with the female body size. The time of spawning in Lake Shikaribetsu was similar to that of this crayfish living in North America and Europe reported by previous studies, but the time of egg hatching was later in Lake Shikaribetsu compared with some populations in North America and Europe. A comparison of our results of the reproduction of P. leniusculus with that of the endangered Japanese endemic crayfish species Cambaroides japonicus reported by previous studies showed that P. leniusculus has a markedly higher reproductive ability than C. japonicus in terms of egg numbers.

Artificial incubation of Japanese crayfish (Cambaroides japonicus) eggs by using a simple, easy method with a microplate

We developed a simple, easy method with a microplate to artificially incubate Japanese crayfish (Cambaroides japonicus) eggs for their cultivation. We prepared 6-, 12-, 24-, 48-, and 96-well microplates containing sterile water heated to 5, 10, 15, and 20 °C. Fourteen experimental groups for each water temperature were prepared for each of different water volumes (0.125–10 ml) in each well. One embryonic egg was placed in each well. Experiments were also conducted with water collected from the lake where the eggs were harvested from and held at 15 °C. In the microplates with sterile water, high proportions of eggs hatched (60–100%) at 15 °C in all volumes of water, although the proportions of hatching were low (0–20%) at 5, 10, and 20 °C. All eggs died in the experiments that used lake water. We conclude that the 96-well would be the most effective size to hatch crayfish eggs in, because of its convenience. This method using a microplate is simpler and easier compared with methods of previous studies to artificially incubate crayfish eggs, and therefore it might be useful to incubate eggs of other freshwater crayfish species. © 2004 Elsevier B.V. All rights reserved.

Water velocity in artificial habitats of the Japanese crayfish Cambaroidesjaponicus

: The appropriate water velocity in artificial burrows for theJapanese crayfish species Cambaroides japonicus was studied.An experimental system of two artificial burrows (burrows A and B)of the same size was set in a large tank. The velocity of burrowA was 0 cm/s and that of burrow B was varied andset at 0 cm/s, 5 cm/s, 10 cm/s,20 cm/s and 30 cm/s. The selectionof these two burrows by C. japonicus was observed. No animalsselected burrow B significantly more than burrow A above 10 cm/s.At 20 cm/s, some crayfishes were swept away andcould not return to burrows because of the high water velocity.At 30 cm/s, most animals were swept away. We concludethat the appropriate water velocity for the suitability of artificialburrows and the immediate foraging area adjacent to the burrowsshould be as low as 5 cm/s.

Competition for Shelter of Preferred Sizes between the Native Crayfish Species Cambaroides Japonicus and the Alien Crayfish Species Pacifastacus Leniusculus in Japan in Relation to Prior Residence, Sex Difference, and Body Size

Abstract Intra- and inter-specific competition for shelter, in relation to prior residence, sex differences, and body-size effects, was studied in the laboratory to assess the potential impact of the alien crayfish species Pacifastacus leniusculus on the endangered Japanese endemic crayfish species Cambaroides japonicus. The resident was placed in an aquarium, which contained a single shelter of preferred size for both C. japonicus and P. leniusculus. After 24 h, the intruder was introduced into the aquarium. In the experiments using different sex pairs of crayfish of approximately equal size, male residents had a significant prior residence effect against female intruders in both crayfish species in the intraspecific contests. However, residents of P. leniusculus dominated C. japonicus regardless of the sex in interspecific contests. In experiments using male crayfish pairs of different sizes, larger individuals had more successful possessions of the shelter against smaller individuals regardless of cray...

ニホンザリガニＣａｍｂａｒｏｉｄｅｓ ｊａｐｏｎｉｃｕｓの成長に対する水深の影響

ニホンザリガニＣａｍｂａｒｏｉｄｅｓ ｊａｐｏｎｉｃｕｓの成長に対する水深の影響

Lethal limits of high temperature for two crayfishes, the native species Cambaroides japonicus and the alien species Pacifastacus leniusculus in Japan

: Lethal limits of high temperature were studied to clarify the effects on the survival of the endangered Japanese crayfish species Cambaroides japonicus and the alien species Pacifastacus leniusculus. After the acclimation period for 2 weeks at 16°C, the temperature was raised at a rate of 1°C per week. As a result, the ultimate upper lethal temperatures of C. japonicus and P. leniusculus were 27.0 and 31.1°C, respectively, and the lethal temperature for P. leniusculus was significantly higher than for C. japonicus. The natural distributions of these two species are discussed in terms of the temperature tolerance.

BEHAVIOR OF JUVENILES OF THE JAPANESE ENDEMIC SPECIES CAMBAROIDES JAPONICUS (DECAPODA: ASTACIDEA: CAMBARIDAE), WITH OBSERVATIONS ON THE POSITION OF THE SPERMATOPHORE ATTACHMENT ON ADULT FEMALES

Abstract The behavior of juveniles of the Japanese endemic crayfish Cambaroides japonicus (Decapoda: Cambaridae) was observed in the field and in the laboratory. In addition, the occurrence and placement of spermatophores on adult females is described from specimens inhabiting small brooks at Otaru and Hamamasu, Hokkaido, Japan, sampled from 1998 to 1999. The second stage juveniles left their mother permanently after some exploration behavior. In adult females, spermatophores were attached to the surface of the seminal receptacle (annulus ventralis), which is situated at the posterior margin of the seventh thoracic sternite. In C. japonicus the invagination of the annulus ventralis is not deep enough to hide the male spermatophores. Previous studies of the Astacidae reported that juveniles left their mother at the second stage, that spermatophores were attached to the surfaces of sternal plates of the last three pereopods, and that an annulus ventralis did not exist. In contrast, Cambaridae juveniles norm...

Aspects of embryonic and postembryonic development of the Japanese freshwater crayfish Cambaroides japonicus (Crustacea, Decapoda) including a hypothesis on the evolution of maternal care in the Astacida

AbstractLittle is known about the biology of the East Asian freshwater crayfish of the genus Cambaroides. Furthermore, the phylogenetic relationships of Cambaroides are controversial. To gain more information about East Asian crayfish and to shed some light on the phylogeny and evolution of freshwater crayfish, some aspects of the embryonic and postembryonic development of the Japanese freshwater crayfish species Cambaroides japonicus are described. The general appearance of the embryo and the growth zone consisting of about 40 ectoteloblasts correspond with the apomorphic pattern described for all other freshwater crayfish species. The occurrence of eight mesoteloblasts is a typical malacostracan character. In addition to the occurrence of freshwater crayfish apomorphies, such as a telson thread, the postembryonic development of C. japonicus follows the ground pattern of the Northern Hemisphere Astacoidea. In particular, some characteristics are in common with the postembryonic development of the Astacidae. These concern the shape of the telson of the juvenile stage 1 and the occurrence of plumose telson setae in juvenile stage 2. Furthermore, the recurved hooks of the hatchlings are lost in the juvenile stage 2, indicating an early independence of the juveniles from the mother. On the other hand, the early appearance of a spermatheca (annulus ventralis) is shared between C. japonicus and the other (American) Cambaridae. The hypothesis is developed that the evolutionary success of the different freshwater crayfish taxa might be related to the stepwise extension of maternal care as an adaptation to the freshwater environment.

Behavior of Juveniles of the Japanese Endemic Species Cambaroides Japonicus (Decapoda: Astacidea: Cambaridae), with Observations on the Position of the Spermatophore Attachment on Adult Females

Behavior of Juveniles of the Japanese Endemic Species Cambaroides Japonicus (Decapoda: Astacidea: Cambaridae), with Observations on the Position of the Spermatophore Attachment on Adult Females

OBSERVATIONS ON THE MATING BEHAVIOR AND SEASON, WITH NO FORM ALTERNATION, OF THE JAPANESE CRAYFISH, CAMBAROIDES JAPONICUS (DECAPODA, CAMBARIDAE), IN LAKE KOMADOME, JAPAN

Abstract The mating behavior and season, with no form alternation, of the Japanese crayfish, Cambaroides japonicus (De Haan, 1841) (Cambaridae), was observed in Lake Komadome, Hokkaido, Japan, from 1993 to 1995. Mating pairs and females with spermatophores were found in September and October in all three years, when water temperature decreased from 20.0° to 12.5°C. Females spawn the following year, and there are six months between mating and spawning. The lengths of each mating pair were similar for both male and female. Mean carapace length in males was 21.7 mm (range: 18.6–24.9), and in females it was 20.9 mm (18.4–22.9). The male lies ventral side up below the female. The male does not use his chelae to hold the female, but rolls his tail over the abdomen of the female. Cambaroides japonicus is placed in the family Cambaridae. All members of Cambaridae in North America have form alternation (cyclic dimorphism), but C. japonicus exhibited no form alternation in its natural habitat.

Artificial burrow preference by the Japanese crayfish Cambaroides japonicus

SUMMARY: Preference for artificial burrows by the endangered Japanese crayfish species Cambaroides japonicus was studied to improve its cultivation. The occupation of artificial burrows, which were made from straight polyvinyl chloride pipes of different internal diameters (Y, mm), by crayfishes of different total lengths (X, mm) was significantly (P < 0.001, n = 56) described by a linear regression: Y = 0.49X + 3.42 (19.0 ≤X≤ 70.2). Among burrows of different lengths [crayfish total length (TL) × 1, × 2, × 3, and × 4], crayfishes significantly preferred burrows that were greater than TL × 3 (P < 0.001, n = 588).

Is invertebrate shredding critical for collector invertebrates? A test of the shredder–collector facilitation hypothesis

A laboratory experiment was conducted to test the hypothesis that leaf processing by Japanese crayfish (Cambaroides japonicus de Haan) enhances the growth and reduces the mortality of collector amphipods (Sternomoera yezoensis Ueno) through fine particulate organic matter (FPOM) production. Two treatments (crayfish shredding, no shredding control) were established using flow‐through artificial streams and permitting differential FPOM production rates. An amphipod enclosure, associated with juvenile amphipods and preconditioned leaf packs, was placed at the downstream end of each channel. During a 4‐week period, shredding by crayfish greatly increased the amount of drifting FPOM compared to that in the control channels, in which only shredder‐independent FPOM occurred. Despite the substantial contribution of crayfish to FPOM production, amphipods in both treatments grew during the 4‐week period and neither amphipod survival nor growth differed between the two treatments. Furthermore, the residual leaf mass in the amphipod enclosures did not differ between the two treatments. However, residual leaf mass in amphipod enclosures was about 20% less than that expected from the processing rates of the leaf packs in the absence of invertebrate shredding. It is likely that amphipods were directly utilizing leaf packs as their food source regardless of FPOM abundance. These results indicate that juvenile amphipods, despite their classification as collectors, were plastic in their foraging habits, and that the FPOM produced by crayfish was not critical for amphipod growth or survivorship.

Observations on the Mating Behavior and Season, with No Form Alternation, of the Japanese Crayfish, Cambaroides Japonicus (Decapoda, Cambaridae), in Lake Komadome, Japan

Observations on the Mating Behavior and Season, with No Form Alternation, of the Japanese Crayfish, Cambaroides Japonicus (Decapoda, Cambaridae), in Lake Komadome, Japan