Outer Gill Research Articles

The reproductive costs of bitterling fish and zebra mussel parasitism to a unionid mussel

Unionid mussels are one of the most vulnerable groups of animals, with multitude of factors responsible for the decline of their populations in the freshwater ecosystems. Many of those causes stem from interspecific relationships. Direct data on the reproductive costs incurred to unionids through parasitism by fish and other mussel species are incomplete. We used field experiments to test whether reproduction of the swollen river mussel (Unio tumidus) is affected by parasitism by the European bitterling fish (Rhodeus amarus) and zebra mussel (Dreissena polymorpha). We documented that bitterling brood can develop in the gills of female, male and hermaphrodite mussels. Our research showed that male mussels carried more fish offspring than female U. tumidus and bitterling embryo survival appeared higher in the outer gill demibranchs. Parasitised female U. tumidus suffered reduced fecundity in terms of a reduced number of mature ovulated oocytes and increased oocyte degeneration. Our data lend clear support to the hypothesis that bitterling fish embryos parasitizing mussel gills and epibiont zebra mussel fouling unionid shells represent a major cost to the reproductive success of their host mussels. Extended gonadal activity (multiple spawning) of U. tumidus spreads their spawning time over a longer period, which may mitigate the costs of parasitism.

Reproductive cycle, fecundity and growth of the freshwater mussel Unio tumidus (Bivalvia: Unionidae) from Lake Viinijärvi, Finland

ABSTRACT Freshwater mussels have a substantial role in aquatic ecosystem function and provide valuable ecosystem services, including water filtration, nutrient cycling, habitat creation and sediment stabilization. While they face population declines globally that can negatively affect an ecosystem's health, such as reducing the water quality and increasing the turbidity, lack of information about the basic reproductive biology for most species makes their conservation much more difficult. Here, we monitored a population of Unio tumidus for a year to study its reproductive biology, gonad-dwelling parasites and growth rate in Lake Viinijärvi, Finland. Our data revealed that this species was dioecious with no evidence of hermaphroditism and was non-significantly female-biased (a male to female ratio of 1:1.3). Both sexes of U. tumidus had continuous gametogenesis during the study period with two peaks in the gonadosomatic index (GSI%) during November and May, followed by two clear declines in December and June. Gravidity period (brooding) of embryos or glochidia in the female's outer gills lasted from June to July. Therefore, this population of U. tumidus can be classified as a short-term breeder (tachytictic). The clear decline of GSI% in December might be a strategy that individuals of U. tumidus use to resorb resources back from the gonad for somatic maintenance during winter. Mean length of glochidia was 391 ± 0.049 µm, being among the largest known glochidia for Unionidae. No gonad-dwelling trematode parasites were detected and the population exhibited high fecundity (numbers of oocytes per female), with an average oocyte production of 242,000 ± 18,000. The studied population had a moderate growth rate with a maximum predicted age of 13 years and asymptotic length (the length at which growth slows down while the mussel continues to age, L∞) of 114 mm. Our study provides the first quantitative data and histological analysis of the reproductive biology of U. tumidus, serving as a basis for future research and conservation.

A new species of Yunnanilus (Cypriniformes, Nemacheilidae) from Yunnan, southwest China

A new species of Yunnanilus is described from the Nanpanjiang River, Yunnan, China. The new species, Yunnanilus polylepis, can be distinguished from other species of Yunnanilus by the following combination of characteristics: Processus dentiformis absent; eye diameter smaller than interorbital width; outer gill raker absent and 10 inner gill rakers on first gill arch; whole trunk covered by scales; nine branched dorsal-fin rays; 10 or 11 branched pectoral-fin rays; six branched pelvic-fin rays. Despite our phylogenetic analysis, which sheds light on the complex relationships among Yunnanilus species, the majority of Yunnanilus species are restricted to more localized environments and habitats. It is urgent to address the environmental threats that jeopardize their survival, especially given their generally restricted distribution.

Triplophysa ferganaensis, a new loach species from Fergana Valley in Central Asia (Teleostei: Nemacheilidae).

Triplophysa ferganaensis sp. nov. is described from the Shakhimardan stream, a small tributary of the Syr Darya, which does not reach the river in Fergana Valley. It can be distinguished from other valid Triplophysa loaches based on the following combination of characters: body smooth and scaleless, lateral line complete, posterior chamber of air bladder degenerated, inner gill rakers 10-11 on the first-gill arch, outer gill rakers absent, vertebrae 4 + 35-36, 8 + 8 branched caudal-fin rays, caudal peduncle depth 2.1-2.7 times its length, two supratemporal pores, dorsal-fin origin closer to the caudal-fin base than to the snout tip, caudal fin emarginated and pelvic-fin tip reaching the anus. The new species can also be distinguished from its congeners based on the molecular analyses of mitochondrial cytochrome oxidase subunit I (coI) gene sequences. The phylogenetic position of this new species indicates that it is a sister taxon of Triplophysa tenuis.

Комплексний вплив нітратів і біотичних чинників на активність in vitro війок фронтального миготливого епітелію зябрового апарату Sinanodonta woodiana (Mollusca, Bivalvia, Unionidae)

Effects of MPC, 2 MPC, and 3MPC water solutions of potassium nitrate and biotic factors (trematode infection and “gill pregnancy”) were studied on the duration of locomotion and beat frequency of epithelial cilia of outer demibranchs of Sinanodonta woodiаna (Lea, 1834). The species has recently invaded the system of water bodies of Ukraine. It has occupied numerous water bodies in the Kiliya distributary of Danube Delta, establishing populations of density and biomass. Statistically significant differences by the studied parameters of ciliary epithelium (duration of locomotion and beat frequency of cilia) were not observed in the control group of non-infected males and latent females of S. woodiana. In females with “gill pregnancy”, the duration of ciliary locomotion decreased by 1.5 times, and beat frequency by 1.4 times (P>99.9 %). It should be noted that the outer surface of demibranchs of female mollusks was completely covered by the filled to the brim marsupial pockets. Thus, the functional load of gills is high, leading to the development of compensatory processes in experimental animals. The processes induce increased effectiveness of protective factors that counteract them. Another biotic factor negatively affecting the experimental pond mussels was the high rates of trematode infection in the hosts’ reproductive glands which contained sporocysts and cercariae of Rhipidocotyle campanula Dujardin, 1845. Prevalence of that infection ranged from 50 to 100 %. These rates of infection were associated with sharply declining functions of cilia of the gill epithelium in studied animals. The compound pathogenic influence of parasite and “gill pregnancy” factors even more affected the functional parameters of outer gill ciliary epithelium. The MPC levels of toxicant in the water medium were accompanied with the first symptom of intoxication of the Chinese pond mussel, the stage of stimulation. At that point, the functional parameters of epithelial cilia of “pregnant” females and in moderately and weakly infected mollusks of both sexes increased in response to exposure to the toxic factor. With the growing concentrations of toxicant to 2 MPC and 3 MPC, the experimental pond mussels developed the pathological process of intoxication, which progressed from the stage of depression to sublethal and lethal stages. Accordingly, the locomotion activity of ciliary epithelium increasingly declined and, in the end, stopped. The “gill pregnancy” and high rates of trematode infection exacerbated the consequences of the process.

A depth cline in deep-sea octopods (Cephalopoda: Graneledone) in the northeast Pacific Ocean

Bathyal octopods of the genus Graneledone Joubin, 1918 in the northeast Pacific differ dramatically in skin texture. To test the hypothesis that these differences are associated with geography, we quantified the skin warts and tubercles of 50 specimens collected between 36°N and 46°N from 1116 to 2850 m depth. Using Principal Component Analysis (PCA), we analyzed the numbers of mantle and head warts, mantle and web tubercles, arm suckers, and inner and outer gill lamellae, adding head width as a size proxy. We used Canonical Correlation Analysis to explicitly test the relationship of morphology to depth and latitude. Sequences of 12S rRNA, 16S rRNA, and COI genes from 12 individuals quantified genetic divergence. PCA revealed correlated variation in head width, arm suckers, and gill lamella counts opposed by skin texture on PC1; PC2 showed correlated variation in skin texture opposed by gill lamella counts. Both components correlate with depth and latitude but, as most shallow specimens came from southern localities, the correlation with latitude may be artefactual. is relationship is corroborated by the canonical correlations. Octopods from greater depths are smaller than those from shallower depths, have rougher skin texture, and fewer suckers and gill lamellae. Clades of shallow and deep octopods show 0.8% genetic divergence in COI (Kimura two-parameter distance), not inconsistent with intraspecific differentiation. We conclude that the variation is likely clinal with depth. The observed morphological differences may result from differences in food availability and oxygen saturation with depth.

Revision of the fish family Euclichthyidae (Pisces: Gadiformes) with the description of two new species from the Western Pacific.

Members of the benthopelagic fish family Euclichthyidae, also known as the Eucla cods, occur on the upper continental slopes off Australasia at 220-1040 m depths. Euclichthyids essentially differ from other gadiform fishes in a combination of two almost contiguous dorsal fins with the second much longer based, a deeply notched anal fin with its anterior portion greatly elevated, jugular pelvic fins consisting of 3 partly united filiform upper rays and 3 free filamentous lower rays, an asymmetrical caudal fin with 5 hypurals fused into two plates, and no chin barbel, or vomerine and palatine tooth patches. Additional characters attributed to the group by other published studies include: no horizontal diaphragm within the posterior chamber of the swim bladder, no swim bladder-auditory capsule connection, presence of a luminous organ, and cranial muscle adductor arcus palatini divided by a strong ligament running from the lateral ethmoid and palatine to the medial face of the hyomandibular. Widely considered to be monotypic since its erection in 1984, the group consists of a single genus and three allopatric species, Euclichthys polynemus McCulloch, 1926 (Western and southern Australia, New Zealand), and two new taxa, E. microdorsalis sp. nov. (northeastern Australia) and E. robertsi sp. nov. (eastern Australia and New Caledonia). Eucla cods are morphologically conservative with both new species superficially resembling the type species, E. polynemus. Euclichthys microdorsalis sp. nov. is the most anatomically and morphologically divergent member of the group in having a shorter first dorsal fin, longer snout, relatively small eye compared to its interorbital width, and fewer caudal-fin rays and primary rakers on the outer gill arch than its congeners. Euclichthys robersti sp. nov. differs from E. polynemus in being smaller with a more slender head, and having a smaller eye, longer anal-fin base and tail, smaller scales, fewer primary rakers on the outer gill arch, more elongate oval otoliths, and usually having a X and/or Y bone in the caudal skeleton (both absent in other Euclichthys). Little is known of their biology but available material suggest that early juveniles remain pelagic in the open ocean with adults benthopelagic near the sea floor. Diagnoses and a key are provided for the three species.

Development of Demerit Score-Based Fish Quality Index (FQI) for Fresh Fish and Shelf Life Prediction Using Statistical Models

ABSTRACTA demerit score-based fish quality index (FQI) has been developed to assess the quality/freshness of fresh fish by considering five general characteristics in the demerit score like appearance of fish outer surface, fish eye, gills, belly and vent. These characteristics were normalized in the range 0 to 1, where 0 represents excellent/best quality of the characteristic and 1 represents bad/worst quality of the characteristic since the quality assessment is based on the demerit score. The value 0 of FQI represents fish with excellent/best quality, and 1 represents fish with bad/worst quality. A theoretical model with auto-correlated errors was also developed to estimate the shelf life for a predicted value of FQI score. The developed FQI was validated with real time data on milk fish (Chanos chanos) stored in chilled condition. It was found that appearance of outer surface and fish gills were the important quality attributes affecting the quality/freshness of milk fish.

Morphological Effects of Pollution on Gill of Common Clam, Tapes decussatus Linnaeus, 1758 (Bivalvia: Veneridae)

Bivalves have been widely used as bioindicators of aquatic habitats because their filter-feeding habit leads to the accumulation of pollutants from the environment. Tapes decussatus is a common edible venerid clam bivalve in Egypt and has particular importance because its habit of penetrating sea sediments can provide information about the surrounding environment. Gill filaments have a large surface with constant contact with water and are therefore used to monitor aquatic environments. In this study, total hydrocarbons and heavy metals were measured in two sites of Egypt, Cleopatra shore (Marsa Matrouh) and Port of Suez (Suez); scanning electron microscopy (SEM) was used to examine the morphology of Tapes decussatus gill filaments and to compare the gill structure in specimens from the two sites. Cleopatra site presents low levels of heavy metals and hydrocarbons undetected, whereas Port of Suez site recorded high levels; because it was directly affected by industrial discharges and harbor pollutants. The gill filaments of T. decussatus have three types of cilia; frontal cilia, latero-frontal cilia, and lateral cilia. Structures joining the inner and outer gill lamellae were found on the abfrontal surface. By comparing the gill of the clam from the two sites; there was an aggregation of particles on the ostia, appearance of bacterial communities at the abfrontal surface of gill fillaments and accumulation of mucus on the frontal surface of the gill filaments of specimens which collected from Suez Port site.This mucus may function as a protective barrier against pollutants

Description of a new species of Alburnus Rafinesque, 1820 (Actinopterygii, Cyprinidae, Leuciscinae) from the Kolpa River in the Sava River system (upper Danube drainage), with remarks on the geographical distribution of shemayas in the Danube.

Alburnus sava, new species, is described from the Kolpa River. The Kolpa is a tributary of the Sava, a major tributary of the Danube River, in the Black Sea basin. Alburnus sava is distinguished from its congeners in the Danube drainage, A. mento and A. sarmaticus, by having 23−27, usually 24−26, gill rakers; the ventral keel usually completely covered by scales (scaleless part maximum 15% of the keel length); 15−16, mode 15, branched pectoral-fin rays; the length of the gill raker at the junction of the arch limbs 65−70% of the length of the opposite outer gill filament; and a relatively long lower jaw (37−40% HL or 112−130% interorbital width). Alburnus sava is a large-sized potamadromous shemaya known to occur in the entire Sava drainage. The taxonomic status of A. mento and A. sarmaticus is confirmed. Alburnus danubicus is discussed and as there are no new arguments, it is kept as a valid species. New details on the distribution of shemayas in the Danube drainage are presented.

Functional analysis of the musculo-skeletal system of the gill apparatus in Heptranchias perlo (Chondrichthyes: Hexanchidae).

Musculo-skeletal morphology is an indispensable source for understanding functional adaptations. Analysis of morphology of the branchial apparatus of Hexanchiform sharks can provide insight into aspects of their respiration that are difficult to observe directly. In this study, I compare the structure of the musculo-skeletal system of the gill apparatus of Heptranchias perlo and Squalus acanthias in respect to their adaptation for one of two respiratory mechanisms known in sharks, namely, the active two-pump (oropharyngeal and parabranchial) ventilation and the ram-jet ventilation. In both species, the oropharyngeal pump possesses two sets of muscles, one for compression and the other for expansion. The parabranchial pump only has constrictors. Expansion of this pump occurs only due to passive elastic recoil of the extrabranchial cartilages. In Squalus acanthias the parabranchial chambers are large and equipped by powerful superficial constrictors. These muscles and the outer walls of the parabranchial chambers are much reduced in Heptranchias perlo, and thus it likely cannot use this pump. However, this reduction allows for vertical elongation of outer gill slits which, along with greater number of gill pouches, likely decreases branchial resistance and, at the same time, increases the gill surface area, and can be regarded as an adaptation for ram ventilation at lower speeds.

Research on drag reduction performance of turbulent boundary layer on bionic jet surface

Based on the fact that jet formed in outer gill of sharks can reduce the wall friction during the breath process, a bionic jet surface model was established. The numerical simulations were carried out using shear stress transport k−ω model, and the simulation results accorded with that of experiments. First, in the case of fixed flow-velocity ratio, the drag reduction performance would be better with the smaller jet’s angle, and the impact that the angle has on the drag reduction would be greater with the increase in jet hole’s aperture. Second, in the case of fixed jet’s angle, the drag reduction had a nearly linear relationship with flow–velocity ratio. Namely, the drag reduction would be better as the flow–velocity ratio increased, and the larger the jet hole’s aperture, the better the drag reduction. In addition, compared with the case of smoothing surface, the flow structure in turbulent boundary layer was changed by jet, increasing the thickness of viscous bottom layer and decreasing the gradient of normal velocity perpendicular to wall. Finally, the drag reduction mechanism was proposed based on the increased velocity effect of turbulent core, isolation effect of wall and the increased turbulent damping effect.

Early life history of the sheepnose (Plethobasus cyphyus) (Mollusca: Bivalvia: Unionoida)

Managing a rare species can be improved with knowledge of its natural history. The sheepnose (Plethobasus cyphyus) is a freshwater mussel recently listed by the US as federally endangered. We used standard methods to study P. cyphyus brooding behaviour, host fishes in the laboratory and under natural conditions, and glochidial morphology. We monitored a population of P. cyphyus in the Chippewa River, WI during spring and summer 2007–2009 and 2011 and found brooding animals between mid-May and early August. Gravid individuals ranged between 5 and 27 yr (mean age ± 1 s.d. = 13 ± 4 yr). Plethobasus cyphyus brooded glochidia in outer gills, which varied in colour from red, orange, pink, cream, or white. We observed mature glochidia more commonly in individuals with cream or white gills and these glochidia were released in a clear, adhesive, mucus matrix. In laboratory trials we found several minnow and topminnow species (29 spp.) served as productive suitable native hosts. The mean number of juvenile mussels released per cyprinid per day was significantly higher for trials conducted at 22–25°C compared with those at 18–20°C, and 83% of trials conducted at 18–20°C using suitable host species produced no juveniles. Glochidia had a unique outline and shell morphometrics that distinguished P. cyphyus from seven other Chippewa River mussel species that produce similar sized glochidia. Using morphometrics we determined that mimic shiners (Notropis volucellus) were natural hosts for P. cyphyus, round pigtoe (Pleurobema sintoxia), and Wabash pigtoe (Fusconaia flava). Releasing mucus-bound glochidia has evolved in a variety of mussel species and may be more common than is currently realized. Our data show that P. cyphyus is a cyprinid host specialist, and propagation efforts for this species can be strengthened through improved access to mature glochidia by using females with cream-coloured gills and increased juvenile production through warmer fish holding temperatures.

Parasite fauna of introduced pumpkinseed fish Lepomis gibbosus: first British record of Onchocleidus dispar (Monogenea)

A survey of pumpkinseed Lepomis gibbosus from a stillwater fishery in southern England revealed infections by the ancyrocephalid monogenean Onchocleidus dispar at 100% prevalence. Host specificity of O. dispar to North American centrarchid fish suggests that it is a non-native parasite, introduced to Britain with L. gibbosus. Mean intensity of O. dispar was significantly higher in male (25.5 parasites) compared to female (15) and immature (7) hosts, but was not influenced by host standard length or sampling time. This sex-biased parasitism is likely to be related to both ecological and physiological factors, such as differential exposure to infective stages during nest building, or higher susceptibility to infection due to enhanced host stress levels. O. dispar significantly dominated the external surfaces and the outer gill arches. Analysis of the spatial distribution of the parasite between the 9 regions of gill surface determined that as density increased, higher numbers of parasites were found on the anterior and central gill regions compared to posterior (distal) regions. Apparent microhabitat selection is discussed in terms O. dispar life cycle, maximising oxygen availability, avoiding unstable areas and increasing intraspecific contact. The absence of O. dispar in the gills of roach, rudd and gudgeon sampled from the same fishery supports the assumption that this parasite is currently of little threat to native fish populations.

Genetic monitoring of two decades of hybridization between allis shad (Alosa alosa) and twaite shad (Alosa fallax)

Habitat alteration has been implicated in driving hybridization between the sympatric migratory shads Alosa alosa and Alosa fallax. Morphological and molecular evidence is consistent with hybridization across the overlapping range of these species, but the temporal extent of hybrid occurrence and genetic consequences for populations have not been explored. Using eight nuclear microsatellite loci and samples collected between 1989 and 2008 in the Solway Firth (UK), we genetically identified hybrids, studied temporal changes in their frequency, and explored changes in allele frequencies of parental populations. These molecular data confirmed the hybrid status of individuals identified using morphology (number of rakers on the outer gill arch), and enabled separation of hybrids from purebred individuals. Mitochondrial cytochrome-b sequencing revealed the presence of two haplogroups, each predominantly occurring in one species. Heterospecific haplotypes were found in 22.3 and 12.8% of A. alosa and A. fallax individuals, respectively, consistent with backcrossing and suggesting that hybrids are fertile. On average, microsatellite-identified hybrids comprised 12.7% of all samples, but when individuals with cytonuclear discordance were also considered introgressed on average 25.4% of individuals were of hybrid ancestry. Overall, allelic richness remained largely unchanged within species, but there were declines in the inbreeding coefficient (FIS) of both species and episodes of significant temporal allelic frequency change. Hybrids sampled between 2004 and 2008 showed no evidence of lower fecundity relative to purebred individuals. Together, results suggest that hybridization between shad species in northern Europe is prevalent, and has been ongoing over at least two decades. The challenge is now to understand the extent to which observed patterns are linked to immigration from other populations, and the mechanisms that have prevented species collapse despite apparent hybrid fertility and longstanding introgression of neutral markers.

Remarks on the taxonomy of Megapodagrionidae with emphasis on the larval gills (Odonata)

A list of genera presently included in Megapodagrionidae and Pseudolestidae is provided, together with information on species for which the larva has been described. Based on the shape of the gills, the genera for which the larva is known can be arranged into four groups: (1) species with inflated sack-like gills with a terminal filament; (2) species with flat vertical gills; (3) species in which the outer gills in life form a tube folded around the median gill; (4) species with flat horizontal gills. The possible monophyly of these groups is discussed. It is noted that horizontal gills are not found in any other family of Zygoptera. Within the Megapodagrionidae the genera with horizontal gills are, with the exception of Dimeragrion, the only ones lacking setae on the shaft of the genital ligula. On the basis of these two characters it is suggested that this group is monophyletic.

Life History and Demographics of the Endangered Birdwing Pearlymussel (Lemiox rimosus) (Bivalvia: Unionidae)

Abstract The life history and population demography of the endangered birdwing pearlymussel (Lemiox rimosus) were studied in the Clinch and Duck rivers, Tennessee. Reproducing populations of L. rimosus now occur only in the Clinch, Duck and Powell rivers, as the species is considered extirpated from the remaining portions of its range in the Tennessee River drainage. Females are long-term winter brooders, typically gravid from Oct. to May. Glochidia are contained in the outer gills and are released in association with a mantle-lure that resembles a small freshwater snail. Estimated fecundity, based on 8 gravid females collected from the Clinch and Duck rivers, ranged from 4132 to 58,700 glochidia/mussel. Seven fish species were tested for suitability as hosts for glochidia, and five darter species were confirmed through induced infestations: Etheostoma blennioides, E. camurum, E. rufilineatum, E. simoterum and E. zonale. Ages of L. rimosus shells were determined by thin-sectioning and ranged from 3 to 15 ...

Host mussel utilization of the Itasenpara bitterling (Acheilognathus longipinnis) in the Moo River in Himi, Japan

Bitterling are fishes that use freshwater mussels for oviposition. The pattern of mussel utilization of an endangered bitterling species, Acheilognathus longipinnis, which spawned in autumn, was investigated in a lowland river. Six Unio douglasiae nipponensis (1.5% of total 388 individuals) hosted A. longipinnis embryos consistently in their outer gills, and they inhabited areas along the river bank where mussel density was relatively high on a less compacted mud substrate. Unexpectedly low rates of host utilization and the rare occurrence of juvenile (shell length, <40 mm) hosts (<0.8% of total individuals) suggest the need for greater attention to the conservation of A. longipinnis.

Adaptive spatial utilization of host mussels by the Japanese rosy bitterling Rhodeus ocellatus kurumeus

The spatial pattern of resource utilization for oviposition in the Japanese rosy bitterling Rhodeus ocellatus kurumeus was investigated in two field experiments. The distribution of rosy bitterling eggs deposited in the four demibranchs of the gills of the test mussel species, Anodonta woodiana, differed with mussel reproductive state in pair spawnings, but not in group spawnings. In pair spawnings, female rosy bitterling may have had more time to select the site of oviposition in the gill in relation to the sex and reproductive state of the mussel, thereby maximizing embryo survival. Thus, the inner gill of female mussels may have been selected in preference to the outer gills to avoid mortalities of eggs due to the presence of the mussel's own embryos (glochidia) in the outer gill chambers. In male mussels, female rosy bitterling distributed their eggs equally among all parts of the mussel gill, thereby minimizing density‐dependent mortality of embryos. During group spawnings, however, female rosy bitterling may have been more constrained in their decision making, ovipositing in the inner gills irrespective of mussel sex.

Embryonic and larval development of a Japanese spinous loach,Cobitis takatsuensis

The embryonic and larval development ofCobitis takatsuensis, a mountain stream spinous loach, was surveyed by incubating artificially inseminated eggs. The mean diameter of the inflated eggs and mean total length of newly-hatched larvae were 2.7 mm and 5.7 mm, respectively. The eggs were spherical, transparent and unpigmented, with a pale yellow yolk and no oil globule. The daily cumulative temperature to hatching was estimated to be 70–110°C. day. Hatched larvae were unpigmented with outer gill filaments on their cheeks, as in otherCobitis species, but the melanophores were comparatively less obvious at each developmental stage. The larvae started feeding eleven days after hatching yolk absorption being completed sixteen days after hatching. All the fin rays were fully developed and the juvenile stage reached at 16 mm TL, 38 days after hatching. Embryonic and larval developmental traits ofC. takatsuensis, such as egg size, clutch size and larval pigmentation, were similar to the Korean species,Niwaella multifasciata, that lives in the upper reaches of the Nak-tong river, andN. delicata, which inhabits Japanese mountain streams, rather than to its congeners. Among cobitine fishes, the spawning of a small number of larger eggs yielding larger larvae without pigmentation, characteristics shared byC. takatsuensis, N. multifasciata andN. delicata, is attributable to adaptation to cold mountain streams.