Genetics and phylogeny of genus Coilia in China based on AFLP markers

The taxonomy of Coilia has been extensively studied in China, and yet phylogenetic relationships among component taxa remain controversial. We used a PCR-based fingerprinting technique, amplified fragment length polymorphism (AFLP) to characterize and identify all four species of Coilia in China. We examined the genetic relationships of the four species of Coilia and a subspecies of Coilia nasus with AFLP. A total of 180 AFLP loci were generated from six primer combinations, of which 76.11% were polymorphic. The mean genetic distance between pairs of taxa ranged from 0.047 to 0.596. The neighbor-joining tree and UPGMA dendrogram resolved the investigated species into three separate lineages: (1) C. mystus, (2) C. grayii and (3) C. brachygnathus, C. nasus, and C. nasus taihuensis. Phylogenetic analysis of the AFLP data is inconsistent with current morphological taxonomic systems. The AFLP data indicated a close relationship among C. brachygnathus, C. nasus taihuensis, and C. nasus. Therefore, the two species described under Coilia (C. brachygnathus and C. nasus taihuensis) are treated as synonyms of C. nasus

Fine mapping and candidate gene analysis of gynoecy trait in chieh-qua (Benincasa hispida Cogn. var. chieh-qua How)

Gynoecy demonstrates an earlier production of hybrids and a higher yield and improves the efficiency of hybrid seed production. Therefore, the utilization of gynoecy is beneficial for the genetic breeding of chieh-qua. However, little knowledge of gynoecious-related genes in chieh-qua has been reported until now. Here, we used an F2 population from the cross between the gynoecious line ‘A36’ and the monoecious line ‘SX’ for genetic mapping and revealed that chieh-qua gynoecy was regulated by a single recessive gene. We fine-mapped it into a 530-kb region flanked by the markers Indel-3 and KASP145 on Chr.8, which harbors eight candidate genes. One of the candidate genes, Bhi08G000345, encoding networked protein 4 (CqNET4), contained a non-synonymous SNP resulting in the amino acid substitution of isoleucine (ATA; I) to methionine (ATG; M). CqNET4 was prominently expressed in the female flower, and only three genes related to ethylene synthesis were significantly expressed between ‘A36’ and ‘SX.’ The results presented here provide support for the CqNET4 as the most likely candidate gene for chieh-qua gynoecy, which differed from the reported gynoecious genes

Ontogenetic development and otolith microstructure in the larval and juvenile stages of mandarin fish Siniperca chuatsi

The mandarin fish Siniperca chuatsi (Perciformes: Percichthyidae) is a commercially important freshwater fish in China. However, S. chuatsi populations have declined dramatically in most of the lake and river systems. In this study, ontogenetic development and sagittal otolith microstructure were studied for this species, and relationships between otolith microstructure patterns and life history events were established during early life history stages. Otolith growth increments were validated as being formed daily, and the first increment was formed three days after hatching (DAH), which coincided with the time of the first feeding. The relationship between body length and otolith radius was fitted by a piecewise linear regression with an inflexion point during the flexion stage at 9.0 mm body length (BLt=148.49e-e-0.04(t-36.75), r(2) = 0.97, P < 0.05, n = 460). Accessory primordium formation corresponded to metamorphosis when the fish transitioned from the post-flexion larval stage to the juvenile stage. Thus, further research can use otoliths to re-construct the early growth and development of wild S. chuatsi populations. During early life history stages, allometric growth patterns showed that the eyes, mouth and head developed with priority, suggesting the essential organs related to feeding develop first. Further research should consider the biological significance of such morpho-functional developmental patterns during the early life history stages of this species

Downstream effects of the Three Gorges Dam on larval dispersal, spatial distribution, and growth of the four major Chinese carps call for reprioritizing conservation measures

Larval drift and dispersal are critical processes that affect recruitment success for many riverine fishes. Hypolimnetic discharge from the Three Gorges Dam (TGD) lowers river temperature and reduces downstream nutrients, inducing distinct shifts in habitat conditions downstream of the dam. The inflow of major tributaries buffers these influences and creates physiochemical gradients according to the distance from the dam. We investigated the abundance, feeding, and growth of larvae of four major Chinese carps in three sections of the middle Yangtze River. Water temperature and transparency showed clear spatial gradients. Larvae in the river section closest to the dam tended to be lower in abundance and temporally delayed peak abundance and showed lower feeding intensity, poorer condition, and slower growth than those further from the dam. Our results demonstrate that physiochemical gradients influenced by the TGD have strong effects on abundance, feeding, and growth of the drifting larvae. We recommend that river sections farther from the TGD, particularly around the mouth of Poyang Lake, should become high-priority conservation areas to enhance protection of critical aquatic species.</p

Opportunistic-tended life history traits of Siniperca kneri in the Three Gorges Reservoir, China: potential responses to impoundment

Reservoir impoundment changes original fluvial habitats into lentic environments. Fish species adapted to lentic habitats may take the advantage of such habitat changes and show typical life history traits might facilitate the population increase. Siniperca kneri rarely occurred in fishery landing in the Three Gorges Reservoir (TGR) area before its impoundment in 2003, but it is now a dominant species. In this study, a total of 438 females of S. kneri were collected monthly during September 2012 through January 2014 using gill nets in the TGR. The age, growth, and reproductive biology were then investigated, and compared with other S. kneri populations. The standard length at age 1 was 149.9 mm in the TGR, which is larger than the three compared populations (i.e., Sandaohe Reservoir, Xinfengjiang Reservoir, and North River), but smaller than one (the Guishi Reservoir). The youngest mature female in the TGR was age 1, which is younger than that of the two compared populations (i.e., Xinfengjiang Reservoir and the North River). The relative fecundity in the TGR was 140 eggs/g, which is higher than that of the only available compared population (Xinfengjiang Reservoir, 96 eggs/g). Our results demonstrated that S. kneri in the TGR tended to have faster growth in the first year, a younger age at first maturation, and higher reproductive effort. We suggest that such opportunistic-tended life history traits might facilitate rapid increase of the population.</p

Longitudinal recovery gradients of drifting larval fish assemblages in the middle reach of the Yangtze River: impact of the Three Gorges Dam and conservation implementation

Drifting larval fish assemblages were investigated at three sections in the middle reach of the Yangtze River downstream of the Three Gorges Dam to reveal recovery gradients and to identify the major environmental factors influencing their temporal and spatial patterns. Larval fish in the river section closest to the dam showed lower abundance, later occurrence, narrower temporal niche breadth, and more pairs of dominant species with high niche overlap than those further from the dam. Water temperature, transparency, and discharge significantly influenced the larval fish assemblages. They showed longitudinal gradients of increased water temperature, decreased transparency, and increased discharge in a downstream direction. Our results suggested that hypolimnetic and clean water discharge from the dam heavily impacted larval fish assemblage in the river section near the dam. With an increased distance to the dam and the input of some major tributaries, this impact was gradually buffered, thus forming the longitudinal recovery gradients. We suggest that priority for conservation should shift from river sections closer to the dam to those further from the dam

Water transfer determines the regional spread dynamics of non-native fish species

Interbasin water transfer projects (IBWT's) have emerged as dispersal corridors for aquatic species. However, little is known about how water transfer affects regional spread dynamics, or shapes the genetic diversity patterns of non-native populations. Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many well-established populations in IBWT's. Here, we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China. Our objectives were to (1) reveal the genetic diversity patterns of the Shimofuri Goby during regional spread, and (2) identify its mode of spreading in water transfer systems. We observed (1) a high level of genetic diversity in non-native populations without evidence of bottleneck effects, (2) that non-native populations with a longer water transfer times had a higher private allele richness, and (3) that non-native populations showed a highly mixed genetic structure, low level of genetic differentiation, and no significant relationship between geographical and genetic distances. Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae, and are probably related to propagule pressure caused by the construction of water transfer. To manage the non-native populations of T. bifasciatus, preventive actions and physical removal should be implemented in IBWT's