DNA markers indicate low genetic diversity and high genetic divergence in the landlocked freshwater goby, Rhinogobius sp. YB, in the Ryukyu Archipelago, Japan

Genetic diversity and genetic divergence were investigated in the landlocked goby Rhinogobius sp. YB by analysis of seven microsatellite DNA loci and the mtDNA control region sequence, and were compared with those of the closely related amphidromous species Rhinogobius sp. DA. Samples of Rhinogobius sp. YB and Rhinogobius sp. DA were collected from seven and four rivers, respectively. All pairwise Fst tests based on microsatellite DNA showed significant genetic differences, except for one pair of populations of Rhinogobius sp. DA (P<0.00064, alpha=78). The average Nei's genetic distance was 0.616 in Rhinogobius sp. YB and 0.394 in Rhinogobius sp. DA. Forty-two haplotypes were detected in both species, and almost all Rhinogobius sp. YB populations included different haplotypes. The means of allelic richness, Ho, and He in Rhinogobius sp. YB (2.057, 0.149, and 0.156, respectively) were significantly lower than in Rhinogobius sp. DA (4.868, 0.366, and 0.403, respectively; P<0.05). The high genetic divergence and low genetic diversity in Rhinogobius sp. YB may have resulted from repeated colonizations of rivers by different founders. Efforts to conserve genetic resources should take these evolutionarily significant units (ESU) of Rhinogobius sp. YB into account. The genetic markers used in this study provide simple and highly informative indicators for Rhinogobius sp. YB population management.     

Occurrence and disappearance of a non-native goby Rhinogobius sp. OR in relation to hydrological conditions in the Kamo River,southwestern Japan

Ichthyological Research - We monitored the abundance of a non-native (Rhinogobius sp. OR) and two native stream gobies (R. fluviatilis and R. nagoyae) over a decade, from 1995 to 2004, in a fixed...     

Migratory history of Rhinogobius sp. OR morphotype “Shimahire” as revealed by otolith Sr:Ca ratios

The migratory history of the Rhinogobius sp. OR morphotype “Shimahire” collected from a slower current environment in the Maruyama River, the Ibo River, and the Kako River, Japan, was studied by examining the strontium and calcium concentrations in the otoliths. The otolith Sr:Ca ratios of almost all samples showed consistently low ratios from the core to the edge, reflecting the fact that the organisms had been living in a freshwater environment their entire lives. The ratios of Rhinogobius sp. CB and Rhinogobius flumineus living in the sympatric habitats with the Rhinogobius sp. OR morphotype “Shimahire” in the Kako River showed an amphidromous and fluvial life cycle, respectively. These findings suggest that the Rhinogobius sp. OR morphotype “Shimahire” has a freshwater resident life cycle.     

Gobioecetes longibasais n. sp. (Monogenea: Dactylogyridae) from Rhinogobius similis Gill (Perciformes: Gobiidae) from Okinawa-jima Island,the Ryukyu Archipelago,southern Japan,with a new host record for Gobioecetes biwaensis Ogawa & Itoh, 2017

Systematic Parasitology - Gobioecetes longibasis n. sp. (Monogenea: Dactylogyridae) from the gills of the freshwater goby Rhinogobius similis Gill (Perciformes: Gobiidae) in the River Teima,...     

Sperm motility and cryopreservation of spermatozoa in freshwater gobies

Testicular sperm motility and methods for the cryopreservation of spermatozoa in the freshwater goby Rhinogobius sp. CB (Cross Band type) were examined. Spermatozoa were almost immotile upon dilution with 300 mOsm kg⁻¹ of NaCl, KCl and mannitol solutions but began to swim in solutions with concentrations <200 mOsm kg⁻¹. The highest percentage and longest duration of motility was obtained in the 0 and 100–200 mOsm kg⁻¹ solutions, respectively. The highest post-thaw motility, c. 50% of motility before cryopreservation, was obtained when spermatozoa were diluted with an extender of 10% methanol and 90% artificial seminal plasma, cooled at −10·0 ± 1·1° C min⁻¹ (mean ± s . e .) to −50° C and plunged into liquid nitrogen. Spermatozoa were cryopreserved in a 50 μl acrylic haematocrit tube to store the small amount of milt. As the cryopreservation method described above was applicable to the endangered Rhinogobius sp. BI (Bonin Island type), it is probable that this method can be used for other species of freshwater gobies.     

A new species ofRhinogobius (Teleostei: Gobiidae) from Fujian Province, China

A new freshwater goby,Rhinogobius xianshuiensis sp. nov. was collected from the upper Mulan River basin of Xianyou County, Fujian Province, eastern China. The species is distinguished from related species in the region by 3–7 predorsal scales, 27 vertebrae, cephalic lateralis canals always always with 2 derived post-orbital pores (ε1) in adults, a reddish-brown vertical line below the anterior margin of the eye, and a red netlike pattern on the opercle. A key to species ofRhinogobius with higher vertebral numbers (27–29) from eastern China, Taiwan and Japan is provided.     

中国广东省虾虎鱼一新种——周氏吻虾虎鱼(Rhinogobius zhoui)(鲈形目:虾虎鱼科)

记述了分布于广东省海丰县莲花山溪流中的吻虾虎鱼属一新种,定名为周氏吻虾虎鱼Rhinogobius zhoui。该新种可由如下特征区别于相近种：第二背鳍条I, 8—9;臀鳍条I, 7—8;胸鳍条16—18;纵列鳞29—31;背鳍前鳞10—12;椎骨数10+16=26;成年雄性个体第一背鳍无黑斑,各奇鳍具宽大的亮白色边缘,颊部与鳃盖膜无斑纹,体侧具6—8个红色斑块。     

Predominance of cross-predation between lateral morphs in a largemouth bass and a freshwater goby

The predator-prey relationship between largemouth bass, Micropterus salmoides, and freshwater goby, Rhinogobius spp., in Lake Biwa, Japan, was examined with respect to their morphological antisymmetry (laterality). Largemouth bass and Rhinogobius gobies exhibited lateral dimorphism in the height of the mandible and the length of the dentary, respectively. Populations of both species were composed of both left-developed and right-developed individuals. Each predation event was categorized as either cross-predation (a predator caught prey of the opposite morph) or parallel-predation (a predator caught prey of the same morph). Stomach contents analysis revealed that cross-predation events predominated over parallel-predation. Annual sampling for eight years demonstrated that in both largemouth bass and Rhinogobius gobies, the ratio of right-developed individuals in the population fluctuated temporally around 0.5. As the predominance of cross-predation was found in the relationship between the exotic largemouth bass and an endemic goby, the predominance may be caused by a kinematical interplay at each predation event.     

Genetic variations estimated from PCR-RFLP analysis of two morphs of the freshwater goby <Emphasis Type="Italic">Rhinogobius</Emphasis> in the Lake Biwa water system

The freshwater goby Rhinogobius is the most abundant fish in the shore area of Lake Biwa, Japan. Recently, it has been reported that two morphs of Rhinogobius inhabit this lake. In this study, genetic variations in Rhinogobius sp. OR (Orange-type) and Rhinogobius sp. BW (Biwa-type) in the Lake Biwa water system have been investigated using polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analysis of mitochondrial DNA, including the variable D-loop region. Samples of Rhinogobius sp. OR were collected from the middle sites of three rivers, two outlets, and two lakeshore sites, whereas samples of Rhinogobius sp. BW were taken from two lakeshore sites. Rhinogobius sp. OR and Rhinogobius sp. BW did not share any haplotypes, suggesting that PCR-RFLP analysis is effective for distinguishing between these species of goby. The haplotype diversity of Rhinogobius sp. OR (0.214–0.543) was lower than that of Rhinogobius sp. BW (0.543–0.682). There were no significant differences in haplotype frequencies between Rhinogobius sp. BW groups from the two localities. In addition, haplotype frequencies in Rhinogobius sp. OR did not differ significantly among samples from the middle sites of rivers, the outlets, and the shores. These results indicate that in Rhinogobius sp. OR there is frequent gene flow among fish inhabiting different sites, and that this species of goby consists of a single population throughout the Lake Biwa water system.     

Population distribution and zoonotic potential of gastrointestinal helminths of wild rats Rattus rattus and R. norvegicus from Jamaica

The population distribution and zoonotic potential of gastrointestinal helminths in a naturally infected population of wild rats (Rattus rattus and Rattus norvegicus) in Jamaica are described. One hundred and thirty (29.7%) of 437 rats captured in the study were infected: 104 (35%) of 297 R. rattus compared with 26 (18.6%) of 140 R. norvegicus. Nine species of gastrointestinal helminths were recovered: Raillietina sp. (0.2%), Trichuris sp. (0.2%), Rictularia sp. (0.7%), Syphacia obvelata (1.1%), Strongyloides ratti (1.4%), Hymenolepis diminuta (3.8%), Protospirura muricola (4.3%), Moniliformis moniliformis (11.2%), and Nippostrongylus brasiliensis (14.2%). In a logistic model, the single risk factor identified for both M. moniliformis and P. muricola was R. rattus, compared with R. norvegicus (OR = 8.369 and 9.714, respectively). In comparison, the risk factor predicted for infection with N. brasiliensis was the northeastern section of Jamaica (OR = 11.000) compared with western Jamaica. Rictularia sp. represents a new geographic distribution record for the Caribbean region. Hymenolepis diminuta, M. moniliformis, Raillietina sp., and Rictularia sp. are potentially zoonotic, but only human infection with H. diminuta has been previously reported in the Caribbean.     

Female preference for nest size in the stream goby Rhinogobius sp DA

Females of the stream goby Rhinogobius sp. DA with paternal care favor males courting in fast water currents, whereby they mate males of high parental ability. Here we examined female choice of male nest size of this goby in laboratory. The dichotomous choice experiment clearly indicated that females prefer large nests. Spawning at large nests seems to improve egg survival rates in natural habitats in this goby. We discuss the possibility of multiple criteria in mate choice of this goby.     

Distribution of hydroids along fronds of the kelp Ecklonia radiata

A full understanding of life history characteristics of invasive species is a fundamental prerequisite for the development of management strategies. Two introduced goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) have established highly abundant populations in Lake Erhai (China). In the present study, we examined the reproductive biology of these two species with the aim of improving the efficiency of management strategy. The results indicated that R. cliffordpopei spawned from February to June, whereas R. giurinus spawned from April to August. Rhinogobius cliffordpopei showed higher gonado-somatic indices and had larger eggs than R. giurinus. The adult sex ratio of R. cliffordpopei was female skewed, but that of R. giurinus was equal. Rhinogobius cliffordpopei showed a male-skewed sexual size dimorphism, whereas the body size of R. giurinus varied only slightly between males and females. The different reproductive traits appear as a crucial biologic aspect for developing control programs. Specifically, control measures should be implemented and/or intensified from September to February for R. cliffordpopei and from January to April for R. giurinus. The body size of the smaller R. cliffordpopei females is the determinant for minimal mesh size of the nets used in physical removals of R. cliffordpopei.     

Feeding of a benthic goby in a river where nektonic fishes are absent

The social structure and feeding behaviour of the benthic goby Rhinogobius sp. DA (dark type) were investigated in a small river in Shikoku, Japan, where nektonic fishes are absent. The gobies had overlapped home ranges but were often aggressive against conspecifics, especially of the same sex and similar body size. Their diet consisted mainly of aquatic invertebrates, but terrestrial invertebrates were also an important item. This contrasted with few terrestrial invertebrates in the diet of the conspecifics in an adjacent river harbouring a nektonic cyprinid fish. An increase in flow level greatly changed their feeding behaviour; on high flow days, a greater portion of the population appeared from the interstices of the bottom and more often rose into the water column to catch drift than on normal flow days. Plasticity of their feeding behaviour is discussed in terms of ecological release.     

Descriptions of six new species of Caryospora (Apicomplexa: Eimeriidae) from Guatemalan snakes (Serpentes: Colubridae and Viperidae)

One hundred and seventy snakes were collected in Guatemala and examined for coccidia. Of these, 8 individuals representing 6 host species were positive for Caryospora spp., 6 of which are described as new species. Sporulated oocysts of Caryospora bothriechis n. sp. from Bothriechis aurifer are spheroidal to subspheroidal, 12.7 x 12.5 (12-14 x 12-13) microm, with a length/width (L/W) ratio of 1.0; they lack a micropyle (M) or oocyst residuum (OR), but 1 large polar granule (PG) is usually present. Sporocysts are ovoidal, 9.0-7.5 (8-10 x 7-8) microm, and have a L/W ratio of 1.2, and a Stieda body (SB) and sporocyst residuum (SR). Oocysts of Caryospora coniophanis n. sp. from Coniophanes imperialis are spheroidal to subspheroidal, 18.8 x 18.1 (17-20.5 x 16-20) microm, with a L/W ratio of 1.0; they lack a M and OR, but 1 large PG is usually present. Sporocysts are ovoidal, 13.2 x 9.4 (12-15 x 8-10) microm with a L/W ratio of 1.4, and a SB, substieda body (SSB), and SR. Oocysts of Caryospora conophae n. sp. from Conophis lineatus are spheroid to subspheroidal, 20.4 x 19.5 (17-26 x 17-25) microm, with a L/W ratio of 1.0; they lack a M and OR, but 1 large PG is usually present. Sporocysts are ovoidal, 13.1 x 9.8 (11-15 x 8-11) microm with a L/W ratio of 1.3 and a SB, SSB, and SR. Oocysts of Caryospora guatemalensis n. sp. from Lampropeltis triangulum are spheroidal to subspheroidal, 23.9 x 23.2 (20-27 x 20-26) microm, with a L/W ratio of 1.0; they lack a M and OR, but 1 large PG is usually present. Sporocysts are ovoidal, 14.4 x 10.6 (13-18 x 9-13) microm, with a L/W ratio of 1.4 and a SB, SSB, and SR. Oocysts of Caryospora mayorum n. sp. from Conophis lineatus are spheroidal to subspheroidal, 25.6 x 24.4 (24-27 x 24-25) microm, with a L/W ratio of 1.0; they lack a M and OR, but 1 large PG is usually present. Sporocysts are ovoidal, 16.3 x 11.9 (16-18 x 11-13) microm, with a L/W ratio of 1.4 and a SB, SSB, and SR. Oocysts of Caryospora zacapensis n. sp. from Masticophis mentovarius are spheroidal to subspheroidal, 22.5 x 21.8 (19-25 x 18-25) microm, with a L/W ratio of 1.0; they lack a M and OR, but 1 large PG is usually present. Sporocysts are ovoidal, 14.6 x 11.4 (11-16 x 10-13) microm, with a L/W ratio of 1.3 and a SB, SSB, and SR.     

Sequence length and variation in the mitochondrial control region of two freshwater gobiid fishes belonging to Rhinogobius (Teleostei: Gobioidei)

The control region (D-loop) of mitochondrial DNA (mtDNA) was amplified and sequenced for eight samples of the rhinogobies Rhinogobius maculafasciatus and R. giurinus from Taiwan and southern China. The control regions of both species are of 841–842 bp; the length of these sequences being the most compact among all known sequences in teleost fishes. Three conserved sequence blocks (CSB) were observed. The full D-loop and tRNA Phe gene sequences were determined and compared with other fishes. The interspecific sequence divergence between the two species is 11.3–11.7%; and the intraspecific variation in R. guirinus 0.8–1.8%. Results suggest that the control region of Rhinogobius is informative for phylogenetic reconstruction at both intraspecific and interspecific levels in this gobiid genus.     

Waterfalls drive parallel evolution in a freshwater goby

Waterfalls may affect fish distribution and genetic structure within drainage networks even to the extent of leading evolutionary events. Here, parallel evolution was studied by focusing on waterfall and the landlocked freshwater goby Rhinogobius sp. YB (YB), which evolved from amphidromous R. brunneus (BR). The fish fauna was surveyed at 30 sites in 11 rivers on Iriomote Island, Japan, the geography of which was characterized by terraces/tablelands with many waterfalls. We found that all YB individuals were distributed only above waterfalls (height 6.8-58.7 m), whereas BR, and other fishes, were mostly distributed below waterfalls. Mitochondrial DNA analysis showed that every YB local population above the waterfall was independently evolved from BR. In contrast, cluster analysis of nine morphological characters, such as fin color and body pattern, showed that the morphology of YB individuals held a similarity beyond the genetic divergence, suggesting parallel evolution has occurred relating to their morphology. Genetic distance between each YB local population and BR was significantly correlated with waterfall height (r(2) = 0.94), suggesting that the waterfalls have been heightened due to the constant geological erosion and that their height represents the isolation period of YB local populations from BR (ca. 11,000-88,000 years). Each local population of BR was once landlocked in upstream by waterfall formation, consequently evolving to YB in each site. Although the morphology of YB had a high degree of similarity among local populations, finer scale analysis showed that the morphology of YB was significantly correlated with the genetic distance from BR. Consequently, there could be simultaneous multiple phases of allopatric/parallel evolution of the goby due to variations in waterfall height on this small island.     

Determinants of male mating success in a natural population of a stream goby of the genus Rhinogobius

The mating success of individually identified males of a stream goby, Rhinogobius sp. CB (cross‐band type), was recorded over one breeding season. One to 3 year‐old males were active in mating, but 3 year‐old males, which accounted for 36% of the population, amounted to c . 70% of the total males guarding eggs in the nest. Three quarters of the breeding males had only one brooding cycle, but the others had two or three. All the latter males changed their nest sites between cycles within a riffle. In 1 and 2 year‐old males, the number of brooding cycles contributed more to the mating success than egg mass size in one brooding cycle. For mating success of 3 year‐old males, the egg mass size in one brooding cycle, which can be enhanced by spawning with a large female or multiple females, was as important as the number of brooding cycles. These male reproductive tactics could be attributed to the age‐related ability of nest construction and mate acquisition.     

<Emphasis Type="Italic">Rhinogobius biwaensis</Emphasis>, a new gobiid fish of the “yoshinobori” species complex, <Emphasis Type="Italic">Rhinogobius</Emphasis> spp., endemic to Lake Biwa,Japan

The endemic lentic goby of Lake Biwa in Japan, which has hitherto been designated informally as Rhinogobius sp. BW, is formally described as Rhinogobius biwaensis sp. nov. It is distinguished from other members of the genus by the following combination of characters: vertebral count 26 (rarely 27); pectoral fin rays 18–22 (mostly 20–21); longitudinal scales 31–36 (mostly 31–34, mode 32); predorsal scales absent or few; D1 low with non-filamentous spines, all of almost same length except for shorter 1st and 6th (last) spines in both sexes; pelvic fin disk composed of thin membranes, its frenum undeveloped with a low, thin lamella; cheek unmarked; back and sides of body with 5–6 unclear dark saddles and 6–9 dark blotches; D1 lacking blotches but melanized to greater or lesser degree along rays; dorsal edge of pectoral base with one small, dark spot tinged with blue metallic luster; in breeding males, yellow on suboperculum and branchiostegal region and on basal part of anal fin, blue on medial part of under jaw.     

Variation in behavioural response to oxygen stress by egg-tending males of parapatric fluvial and lacustrine populations of a landlocked goby

The behavioural response of egg-tending males from parapatric fluvial and lacustrine populations of a landlocked goby Rhinogobius sp. (the orange form) to oxygen stress was compared in laboratory experiments. The natural spawning locations of these populations (rapids of tributary rivers and lakeshore of Lake Biwa, respectively) differ in dissolved oxygen concentration and its variability. Males of both populations spent a longer period of time in fanning behaviour under low dissolved oxygen conditions (4·5–5·0 mg l⁻¹), where >90% of eggs without paternal care died before reaching eyed stage, relative to fully saturated dissolved oxygen conditions (8·0–8·5 mg l⁻¹). Lacustrine males, who occasionally encounter oxygen stress (<2 mg l⁻¹) in their natural habitat, fanned eggs for a longer time period than fluvial males. The time difference in fanning behaviour between the two oxygen conditions was greater for lacustrine than fluvial males. Survival rate in the lower oxygen condition was higher for eggs tended by lacustrine males than those tended by fluvial males, probably due to this difference in fanning activity. These results showed that the response to oxygen stress differs between the two populations and, moreover, as both populations behaved adaptively in responding to the reduction in dissolved oxygen, contiguous habitats may have distinct natural selective pressures. It is suggested that regulation of egg fanning activity is strongly favoured by natural selection in unpredictable environments.