Reproductive and Developmental Alterations on Zebrafish (Danio rerio) Upon Long-Term Exposure of Di-ethyl phthalate (DEP), Di-isononyl phthalate (DINP) and Di (2-ethylhexyl) phthalate (DEHP).

Di (2-ethylhexyl) phthalate (DEHP), di-ethyl phthalate (DEP) and di-isononyl phthalate (DINP) are all endocrine disrupting chemicals (EDCs) for organisms. However, little research has been done on the effects of long-term EDC exposure. The present study found that the zebrafish barely grew during the 7 months of DINP exposure. The fecundity rate (%) of female spawning was lower in the DEHP treatment by 4 months compared to other exposure groups. Zebrafish treated with 12.5-25.0 ppm of DEP for 4 months presented no spawning. Gonadal-somatic index (GSI) levels significantly decreased, and there were more oocytes in the atresia and peri-nucleus stage compared to the control group. In addition, the hatching rate of embryos were 71.02%, 56.92%, and 21.70% for females treated with DINP, DEHP and DEP, respectively. There were also abnormal craniofacial chondrogenesis development on 72 hpf embryos upon females treated with the three EDCs. In conclusion, long term exposure of DEHP, DINP, and DEP did not only affect the reproductive capacity of female zebrafish, but the 3 plasticizers also influence craniofacial cartilage development of its offspring.

Suction feeding biomechanics of Polypterus bichir: investigating linkage mechanisms and the contributions of cranial kinesis to oral cavity volume change.

Many fishes use substantial cranial kinesis to rapidly increase buccal cavity volume, pulling prey into the mouth via suction feeding. Living polypterids are a key lineage for understanding the evolution and biomechanics of suction feeding because of their phylogenetic position and unique morphology. Polypterus bichir have fewer mobile cranial elements compared with teleosts [e.g. immobile (pre)maxillae] but successfully generate suction through dorsal, ventral and lateral oral cavity expansion. However, the relative contributions of these motions to suction feeding success have not been quantified. Additionally, extensive body musculature and lack of opercular jaw opening linkages make P. bichir of interest for examining the role of cranial versus axial muscles in driving mandibular depression. Here, we analyzed the kinematics of buccal expansion during suction feeding in P. bichir using X-ray Reconstruction of Moving Morphology (XROMM) and quantified the contributions of skeletal elements to oral cavity volume expansion and prey capture. Mouth gape peaks early in the strike, followed by maximum cleithral and ceratohyal rotations, and finally by opercular and suspensorial abductions, maintaining the anterior-to-posterior movement of water. Using a new method of quantifying bones' relative contributions to volume change (RCVC), we demonstrate that ceratohyal kinematics are the most significant drivers of oral cavity volume change. All measured cranial bone motions, except abduction of the suspensorium, are correlated with prey motion. Lastly, cleithral retraction is largely concurrent with ceratohyal retraction and jaw depression, while the sternohyoideus maintains constant length, suggesting a central role of the axial muscles, cleithrum and ceratohyal in ventral expansion.

Skeletal kinematics of the hyoid arch in the suction-feeding shark Chiloscyllium plagiosum.

White-spotted bamboo sharks, Chiloscyllium plagiosum, generate strong suction-feeding pressures that rival the highest levels measured in ray-finned fishes. However, the hyostylic jaw suspension of these sharks is fundamentally different from the actinopterygian mechanism, including more mobile hyomandibulae, with the jaws and ceratohyal suspended from the hyomandibulae. Prior studies have proposed skeletal kinematics during feeding in orectolobid sharks from indirect measurements. Here, we tested these hypotheses using XROMM to measure cartilage motions directly. In agreement with prior hypotheses, we found extremely large retraction and depression of the ceratohyal, facilitated by large protraction and depression of the hyomandibula. Somewhat unexpectedly, XROMM also showed tremendous long-axis rotation (LAR) of both the ceratohyal and hyomandibula. This LAR likely increases the range of motion for the hyoid arch by keeping the elements properly articulated through their large arcs of motion. XROMM also confirmed that upper jaw protraction occurs before peak gape, similarly to actinopterygian suction feeders, but different from most other sharks in which jaw protrusion serves primarily to close the mouth. Early jaw protraction results from decoupling the rotations of the hyomandibula, with much of protraction occurring before peak gape with the other rotations lagging behind. In addition, the magnitudes of retraction and protraction of the hyoid elements are independent of the magnitude of depression, varying the shape of the mouth among feeding strikes. Hence, the large variation in suction-feeding behavior and performance may contribute to the wide dietary breadth of bamboo sharks.

Maternal effect and dietary supplementation of estradiol-17ß on female zebrafish (Danio rerio) affects the swimming behavior and stress-coping styles of its offspring.

Extrinsic estradiol-17ß (E2) is an environmental hormone. Female fish exposure to waterborne E2 might affect the development of craniofacial cartilage of its offspring. The present study investigates the effects of maternal E2 on larval craniofacial cartilage development by administering oral feed containing E2 (F-E2) to female zebrafish, and examines whether the swimming behavior and their stress coping style are influenced by maternal E2. The results showed that E2 contents responded to dosage and time in male fish after being fed with a diet containing E2. In addition, the E2 contents in female ovaries showed a significant increase after 250 mg of E2/kg treatment for 14 d. On the other hand, the fecundity rate of F-E2 group was lower around 2 folds than FC (female fed 0 mg of E2/kg) group. Craniofacial chondrogenesis on 72 hpf (hours of post fertilization) of F-E2 larvae were abnormalities, and a recovery to a normal developmental pattern was observed at the 96 hpf stage. The swimming speed was slower for F-E2 larvae compared to the FC larvae; and the F-E2 juvenile seems to be less responsive to cortisol (LRC) after cold stress. According to the results, we suggested that F-E2 larvae might have worse environmental adaptability than FC larvae.

Cloning of zebrafish Mustn1 orthologs and their expression during early development.

Mustn1 is a small nuclear protein that is involved in the development and regeneration of the musculoskeletal system. Previous work established a role for Mustn1 in myogenic and chondrogenic differentiation. In addition, recent evidence suggests a potential role for Mustn1 in cilia function in zebrafish. A detailed study of Mustn1 expression has yet to be conducted in zebrafish. As such, we report herein the cloning of the zebrafish Mustn1 orthologs, mustn1a and mustn1b, and their expression during zebrafish embryonic and larval development. Results indicate a 44% nucleotide identity between the two paralogs. Phylogenetic analysis further confirmed that the Mustn1a and 1b predicted proteins were highly related to other vertebrate members of the Mustn1 protein family. Whole mount in situ hybridization revealed expression of both mustn1a and 1b at the 7-somite stage through 72hpf in structures such as Kupffer's vesicle, segmental mesoderm, head structures, and otic vesicle. Additionally, in 5day old larva, mustn1a and 1b expression is detected in the neurocranium, otic capsule, and the gut. Although both were expressed in the neurocranium, mustn1a was localized in the hypophyseal fenestra whereas mustn1b was found near the posterior basicapsular commissure. mustn1b also displayed expression in the ceratohyal and ceratobranchial elements of the pharyngeal skeleton. These expression patterns were verified temporally by q-PCR analysis. Taken together, we conclude that Mustn1 expression is conserved in vertebrates and that the variations in expression of the two zebrafish paralogs suggest different modes of molecular regulation.