Relationships Among Trophic Niche Width, Morphological Variation, and Genetic Diversity of Hemiculter leucisculus in China

According to the niche variation hypothesis (NVH), the populations with wider niches are phenotypically more variable than those with narrow niches. Giller expanded the NVH, suggesting that the niche width, morphological variation, and genetic diversity are all positively correlated. However, the hypothesis has been a subject of debate and discussion. In the present study, the NVH was tested by analyzing the relationships among trophic niche width, morphological variation, and genetic diversity of Hemiculter leucisculus, a widespread cyprinid fish. The fish samples were collected from six sites across Haihe, the Yellow, and the Yangtze River basins in China. The relationships among trophic niche width, morphological variation, and genetic diversity were analyzed using Pearson correlation at the inter-population level. Our analysis indicated that trophic niche width is significantly positively correlated with morphological variation, which corroborates the NVH. Morphological variation was significantly correlated to genetic diversity. However, no relationship was observed between trophic niche width and genetic diversity. We inferred that the dietary niche of H. leucisculus might change due to the plastic response toward environmental changes rather than due to the genetic variation. We also suggest that the effects of environment and heredity on the niche of the freshwater fish should be quantified separately in further studies.

Thực trạng nhiễm ấu trùng sán lá nhỏ trên cá nước ngọt tại một số điểm nghiên cứu của tỉnh Bình Định và Bắc Giang

Với thiết kế cắt ngang và cỡ mẫu 400, nghiên cứu đã bước đầu đánh giá thực trạng nhiễm ấu trùng sán lá nhỏ (SLN) trên cá nước ngọt tại sáu xã của tỉnh Bắc Giang và tỉnh Bình Định từ năm 2016 đến 2017. Kết quả cho thấy: tỷ lệ nhiễm ấu trùng SLN ở Bắc Giang trên cá Mè trắng (Hypophthalmichthys molitrix) là 70%, trên cá Diếc (Carassius auratus) là 62,5%, trên cá Mương xanh (Hemiculter leucisculus) là 25%, trên cá Tép dầu (Toxabramis houdemeri) là 95%, trên Cá Thiểu (Cultrichthys erythropterus) là 85%, trên cá Trắm cỏ ( Ctenopharyngodon idellus) là 12,5% và trên cá Chép (Cyprinus carpio) là 62,5% và tỷ lệ nhiễm ấu trùng SLN ở Bình Định trên cá Mè trắng (Hypophthalmichthys molitrix) là 42,5%, trên cá Diếc (Carassius auratus) là 95%, trên cá Mương xanh (Hemiculter leucisculus) là 20%.

The situation of metacercariae infection in freshwater fishes in Binh Dinh and Bac Giang province, 2016 - 2017

A cross-sectional study was applied in oder to evaluate the situation of metacercariae infections in freshwater fishes in six communes of Bac Giang and Binh Dinh province from 2016 to 2017. The sample size was of 400 freshwater fishe samples. The results showed that: (1) In Bac Giang province, metacercariae was found in 70% of Hypophthalmichthys molitrix, 62.5% of Carassius auratus, 25% of Hemiculter leucisculus, 95% of Toxabramis houdemeri, 85% of Cultrichthys erythropterus, 12.5% of Ctenopharyngodon idellus and 62.5% of Cyprinus carpio samples; and (2) In Binh Dinh province, metacercariae was found in 42.5% of Hypophthalmichthys molitrix, 95% of Carassius auratus, and 20% of Hemiculter leucisculus samples.

Redescription of Paradiplozoon hemiculteri (Monogenea, Diplozoidae) from the type host Hemiculter leucisculus, with neotype designation

Paradiplozoon hemiculteri (Ling, 1973), a member of the Diplozoidae, parasitizes the gills of Asian fish. Not only is the type material unavailable for this species, the original description was poor and somewhat conflicting, and adequate molecular data were not available. What is more, the available morphological and molecular data are inconsistent and fluctuate significantly. Here, we present a redescription of P. hemiculteri based on morphological and molecular data from new isolates collected from the type host, the sharpbelly Hemiculter leucisculus (Basilewsky, 1855), captured at the neotype locality (Shaoguan, Guangdong Province, southern China); a neotype for P. hemiculteri was designated from this collection. The length and width of the body, buccal suckers, pharynx, attachment clamps, sickle and the central hook handle were all measured and the shape of the anterior and posterior part of the median plate and anterior and posterior joining sclerites accurately documented. Phylogenetic analyses based on the sequences of the second rDNA internal transcribed spacer (ITS2) indicated that all new samples clustered together and differed clearly from sequences attributed to P. hemiculteri, which are deposited in GenBank. Our results confirm that P. hemiculteri is the only diplozoid that has demonstrably been found on the gills of H. leucisculus to date.