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When restoring shallow lakes, the recovery of submerged macrophytes is of vital importance to obtain clear water conditions. However, post-restoration recovery of small omnivorous fish can increase water nutrient concentrations through excretion. The impact of these recycled nutrients on submerged macrophytes is not well-studied, and it may depend on fish food of varying nutrient contents. We studied the effects of Acheilognathus macropterus on the growth and nutrient stoichiometry of Vallisneria denseserrulata and Hydrilla verticillata. The experiment had six treatments: two controls without recycled nutrients and two nutrient treatments for each of the plant species, respectively. We found that fish released more phosphorus after consuming low N:P food and more nitrogen after high N:P food. The recycled nutrients significantly promoted the growth of both macrophyte species. Interestingly, macrophytes showed higher growth rates in treatments with nutrients from the low N:P food source. Our study, therefore, suggests that nutrient subsidy from fish excretion can significantly stimulate the growth of submerged macrophytes, the magnitude of the effect being determined by the N:P ratio of the fish food. The realization of this growth potential, however, also depends on the phytoplankton response to these nutrients, that expectedly will be weaker at high macrophyte coverage. [ABSTRACT FROM AUTHOR]

In this study, thirty-six individuals of Acheilognathus macropterus were collected from the Heilongjiang River, the Yangtze River, and the Nandujiang River. Partial mitochondrial cytochrome b gene region (636 base pair) was sequenced to these samples and 22 haplotypes were found. With A. chankaensis and A. tokinensis as outgroups, their relationships were analyzed. The p-distances were calculated with Mega software and a molecular phylogenetic tree was constructed using the neighbor-joining (NJ) method. The proportions of main morphological characters were compared as well. P-distances showed that the genetic differences in A. macropterus samples were far smaller than those between these samples and the outgroups. The molecular phylogenetic tree shows that samples with barbels and those without barbels were intermingled. There was no distinctive difference in proportions of morphological characteristics among them. These results suggested that samples with barbels and those without barbels (formally identified as A. taenianalis) are the same species; A. taenianalis is synonymous with A. macropterus. The thirtysix individuals were grouped into five clades and the positions of the samples in the clades were correspondingly grouped within their geographical distributions. Among the five clades, clades 1 and 5 included samples from the Heilongjiang River and Nandujiang River respectively. The samples from the Yangtze River scattered into clades 2, 3, and 4. There were distinctive genetic differences (>5%) among them. Interestingly, the distributions of the 21 samples in these three clades were not correlated to their geographical distributions. It is postulated that these genetic differences were due to the bitterlings’ mating choice mechanism, the prozygotic isolation. The genetic differences between the fish from Nandujiang River and those from the mainland indicated that they were separated early. However, the small genetic differences among the samples and the positions of the fish from the Heilonjiang River in the molecular phylogenetic tree indicate that fish in Heilongjiang River might have dispersed from the Yangtze River to that area much later. [ABSTRACT FROM AUTHOR]

Acheilognathus macropterusbelongs to the family Acheilognathinae. In the present study, we obtain the complete mitochondrial genome of the Chinese bitterlingA. macropterusby PCR amplification and DNA sequencing. It is a circular double-stranded DNA molecule of 16,773 bp in length, containing 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and two main non-coding regions (the control region and the origin of the light strand replication). The gene composition and order of which are similar to most other vertebrates. Compared withAcanthorhodeus macropterus, they share 98.90% nucleotide sequences similarity, and the biggest nucleotide sequence discrepancy between homologous genes are observed inND5gene. The molecular data we presented here could provide useful information for the studies on species identification, evolutionary relationships and population genetics of the Acheilognathinae. [ABSTRACT FROM AUTHOR]