Hangkyo Lim

<i>Tanakia</i> is a bitterling genus with six species found in Far East Asia. Our aim was to construct the standard DNA barcode database available for the identification of six <i>Tanakia</i> species by comparing the range of intra- and inter-specific genetic distances, identifying the phylogenetic placement of each <i>Tanakia</i> species and providing the unique barcode characteristics that are specific to each species, using cytochrome oxidase I (COI) and cytochrome b (cyt <i>b</i>). Both loci failed to create a perfect barcoding gap between the ranges of inter- and intra-specific genetic distances, though interspecific COI distances were sufficiently greater than intraspecific values with only a few exceptions. In our phylogenetic analyses, <i>T. koreensis</i> and <i>T. signifer</i> did not form a monophyletic cluster of haplotypes in both loci. COI provided clear nucleotide characteristics that distinguish each species, whereas relatively fewer informative sites were found within the range of cyt <i>b</i>. Overall, COI could be regarded as appropriate species identification solution in <i>Tanakia</i>. Our analyses yielded some taxonomic issues that need the further investigation, and are expected to be helpful in the examination for the conservation status of <i>Tanakia</i> species that are on the verge of being endangered.

Different species of water striders match leg speeds to their body sizes to maximize their jump take off velocity without breaking the water surface, which might have aided evolution of leg structures optimized for exploitation of the water surface tension. It is not understood how water striders achieve this match. Can individuals modify their leg movements based on their body mass and locomotor experience? Here we tested if water striders, Gerris latiabdominis, adjust jumping behaviour based on their personal experience and how an experimentally added body weight affects this process. Females, but not males, modified their jumping behaviour in weight-dependent manner, but only when they experienced frequent jumping. They did so within the environmental constraint set by the physics of water surface tension. Females’ ability to adjust jumping may represent their adaptation to frequent increases or decreases of the weight that they support as mating bouts, during which males ride on...

Kichulchoia multifasciata, a small-sized loach (Family Cobitidae) inhabiting only the Nakdong River on the Korean Peninsula, is generally found around well-oxygenated minor tributaries. Despite the scarcity, this species is not yet a legally protected species in South Korea, and the spatial pattern of genetic diversity, which is essential to create management strategies, has never been studied. In this study, three mitochondrial loci and ten microsatellites were used to analyze the genetic diversity and the structure among eight K. multifasciata populations collected from different tributaries. K. multifasciata populations showed a high level of mitochondrial variability, with above 0.9 of average haplotype diversity in all three loci analyzed. A substantial microsatellite polymorphism was also found. Weak genetic structuring among populations and isolation by distance were clearly revealed in both mitochondrial and microsatellite data, indicating the high levels of gene flow among the tributaries. However, a few of the populations exhibited a genetic signature that they have experienced the historical size decline. Our data suggest that unequal gene flow might be one of the causes; nevertheless, the possibility of effective population size reduction by other factors could not be completely excluded. Our genetic evidence can be the critical information needed to protect the populations from the genetic erosion in the Nakdong River that has been destroyed and fragmented with increasing anthropogenic interferences.

Tanakia is a bitterling genus with six species found in Far East Asia. Our aim was to construct the standard DNA barcode database available for the identification of six Tanakia species by comparing the range of intra- and inter-specific genetic distances, identifying the phylogenetic placement of each Tanakia species and providing the unique barcode characteristics that are specific to each species, using cytochrome oxidase I (COI) and cytochrome b (cyt b). Both loci failed to create a perfect barcoding gap between the ranges of inter- and intra-specific genetic distances, though interspecific COI distances were sufficiently greater than intraspecific values with only a few exceptions. In our phylogenetic analyses, T. koreensis and T. signifer did not form a monophyletic cluster of haplotypes in both loci. COI provided clear nucleotide characteristics that distinguish each species, whereas relatively fewer informative sites were found within the range of cyt b. Overall, COI could b...

A series of laboratory experiments tested the hypothesis that the Silver Carp (Hypophthalmichthys molitrix), an invasive river carp from China, employs a prostaglandin F2α-derived sex pheromone that is attractive and species-specific. Using electro-olfactogram recording (EOG), we found that the olfactory system of this species is acutely sensitive to three F-series prostaglandins (PGFs) at picomolar concentrations and that this sensitivity is enhanced when juveniles are masculinized using androgens, consistent with expectations of a sex pheromone. Individual PGFs had behavioral activity but it was low, suggesting a mixture might be important. To pursue this possibility, we implanted carps with osmotic pumps containing prostaglandin F2α (PGF2α), a treatment previously shown to elicit release of a PGF-based spawning pheromone in the Common Carp. We found that PGF2α-implanted Silver Carp released a species-specific odor that contained a blend of PGF2α and two of its metabolites, which ...

Our previous research has determined that invasive bighead and silver carp are responsive to conspecific pheromones. They avoid alarm pheromones present in skin extracts as a means of avoiding predators, and they are attracted to chemicals released by groups of conspecifics as a means of maintaining schooling under turbid water conditions. Sex pheromones are olfactory signals that mediate conspecific reproductive interactions. The Asian carp sex pheromones are likely hormonal metabolites, as described in common carp and goldfish, which synchronize sexual readiness within the population and induce specific behaviors such as attraction, nest preparation, and spawning behaviors. Physiological screening assays (electro-olfactograms) indicated very high sensitivity of the carp olfactory system for hormone metabolites associated with sex pheromones. Behavioral assays verified behavioral attraction to these hormone metabolites. Proof-of-concept studies were initiated to determine if attrac...

Our previous research has determined that invasive bighead and silver carp are responsive to conspecific pheromones both physiologically and behaviorally. Asian carp avoid alarm pheromones present in skin extracts as a means of avoiding predators, and are also attracted to chemical cues released by groups of conspecifics as a means of maintaining schooling behavior in turbid water conditions. Sex pheromones are olfactory signals that mediate conspecific reproductive interactions. Physiological screening assays (electro-olfactograms) have indicated high sensitivity of the olfactory system for certain hormonal metabolites associated with the sex pheromones and behavioral assays verified an attractant response to those certain hormonal metabolites. We conducted a series of “proof-of-concept” pond studies to determine if attractive sex pheromone production could be hormonally induced in females with the aim of using caged hormonally implanted females as a source of attractive pheromone ...

Since its introduction forty years ago in Arkansas, the silver carp, Hypophthalmichthys molitrix, has been steadily advancing northward while destroying vast areas of river habitat whose biomass it comes to dominate. Because of its elusive nature, monitoring presence and movement of this fish is extremely difficult. Pheromones, chemical signals that pass between conspecifics, play essential roles in carp social behavior and are presently being used to sample and remove adult common carp, Cyprinus carpio. This species, like most fishes, uses unique complexes of hormone-derived products as sex pheromones. This study explored this possibility in the silver carp by examining its sensitivity to over 200 steroid hormones and F prostaglandins (PGFs). We discovered that the silver carp olfactory system detects a unique combination of 9 sex steroids and 3 PGFs at picomolar concentrations with high specificity and the sensitivity of masculinized fish to PGFs is especially pronounced. Behavior...

Many species of teleost fish detect and release F prostaglandins (PGFs), but the specific identities of these compounds and how they function as species-specific pheromones have yet to be resolved. This study addressed these questions in the common carp. An initial set of experiments established that mature male common carp were attracted to chemicals released by ovulated conspecifics, whereas the odor of female goldfish, a close relative, was less attractive. Tests of fractionated holding water from ovulated carp revealed that only the non-polar fraction was attractive on its own. Mass spectrometry and immunoassay next demonstrated that the non-polar fraction contained large quantities of prostaglandin F(2α) (PGF(2α)), 15keto-prostaglandinF(2α), and 13,14-dihydro-15keto-prostaglandin F(2α) (100 g fish released over 1 μg of all 3 PGFs per h at a ratio of 1.0: 1.7: 0.7). Ovulated goldfish released the same three PGFs but at a slightly greater rate and in a different ratio. Tests of synthetic mixtures of these PGFs revealed that the carp-specific mixture attracted male carp but was no better than the goldfish-specific mixture or PGF(2α) alone and that PGF(2α) was just as attractive as mixture of all three PGFs. A final set of attraction tests revealed that although PGF(2α) could explain all of the activity of the non-polar portion of female carp holding water, it could not explain the entire activity of female water but that a mixture of PGFs and the polar fraction could. We conclude that ovulated female carp release a multi-component sex pheromone complex that is comprised of PGF(2α) and unknown species-specific polar compound(s) that synergize the activity of the former. The pheromone also might be useful in controlling this invasive species. The observation that a fish hormonal sex pheromone incorporates bodily metabolites in addition to relatively common hormonal products demonstrates a mechanism by which species specificity may be conferred to this common type of sex pheromone.

Perception of the female sex pheromone in Utetheisa ornatrix (Lepidoptera: Arctiidae) is responsible for induction and adjustment of calling by females and the collective phenomenon termed "female pheromonal chorusing". We found five olfactory-active compounds in the U. ornatrix female gland. When females were exposed to the entire pheromone or to two of its (synthetically prepared) components, (Z,Z,Z)-3,6,9-eicosatriene and (Z,Z,Z)-3,6,9-heneicosatriene, they were more likely to call during a given night, begin calling earlier, and briefly increase signal frequency with which they extrude their abdomen, an observable indication of calling in this species. Some females even initiated calling during photophase when exposed to the pheromone components. In general, female U. ornatrix are more sensitive to the complete blend of pheromone than to its individual compounds. We also tested the hypotheses: 1) that abdominal extrusion per se increases the rate of pheromone release; and 2) that greater abdominal pumping rhythm increases pheromone release rate. Contrary to our expectations: 1) females did not respond more strongly to a pulsed pheromone stimulus than to the constant release of pheromone at the same average release rate; and 2) we did not find a relationship between the frequency of abdominal pumping and pheromone release rate. Possible explanations for these unexpected findings are discussed.