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Bohai Bay, a representative semi‐enclosed bay of China, has been severely impacted in recent decades by rapid human development. Although the mantis shrimp Oratosquilla oratoria plays an important role in the Bohai Bay ecosystem and fishery, its feeding ecology and the impact of habitat changes on its feeding habits are poorly known. In this study, we sought to identify its feeding strategy through the separation of stomach contents, and to describe its trophic ecology during maturation in the Tianjin coastal zone of Bohai Bay by the DNA barcoding method using a fragment (about 690 bp) of the mitochondrial cytochrome oxidase I (CO I) gene. A total of 594 specimens were collected from March to July 2018, and 347 (58.42%) stomachs were found to have food remains. More than half of the O. oratoria individuals had poor feeding activity, and the degree of feeding of females was higher than that of males, but there was no significant difference in the visual fullness index and the fullness weight index (FWI) between sexes for each month. In addition, the feeding activity of O. oratoria was consistent across the months, suggesting in artificial breeding programs it is not worried too much about the accessional diet supplied to the female bloodstocks except maintaining their normal food. A total of 167 retrieved prey items yielded 187 readable sequences; 86.63% of these sequences could be assigned to the species level. Consequently, 25 different prey taxa covering all readable sequences were identified, showing O. oratoria is a generalist predator. In terms of percent composition by frequency of occurrences (%N), crustaceans and fishes accounted for the same and highest percentage (35.83%) in the mantis shrimp diet, followed by mollusks (24.59%) and the remaining marine organisms (3.73%) including Polychaeta (2.67%), Sagittoidea (0.53%), and Chromadorea (0.53%). The result shows the benthic fish Oxudercidae (family) appears to be an especially important food supply for O. oratoria during maturation. The degree of cannibalism decreased with an increase in diet species and the frequencies of cannibalism in this study was noticeably higher than that in previous studies, suggesting that cannibalism may be a significant feeding strategy in the mantis shrimp O. oratoria in the Tianjin coastal zone of Bohai Bay, and because of the frequently cannibalistic behavior, the high stocking density of broodstocks should be avoided. [ABSTRACT FROM AUTHOR]

Overexploitation and preliminary artificial breeding have led to an increasing interest in studying the reproductive biology and biochemical changes during gonad development in Oratosquilla oratoria. In this study, we established an accurate one-to-one correspondence between physical (and ovarian) morphology and ovarian histology during different maturity stages and improved the understanding of trophic dynamics with the progress of maturation, which will aid the aquaculture and artificial breeding techniques for this commercially important species. Based on ovarian histology and morphology, the ovaries were differentiated into six developmental stages, with five changes in color: immature stage (black), previtellogenesis (black), primary vitellogenesis (faint yellow), secondary vitellogenesis (golden yellow), maturation (light orange) and spent stage (brownish yellow). The visible colors of the median triangular structure of the telson can be used as an external morphological indicator of ovarian development status, and indicates that the females are near-ripe broods stocks when median triangular structure is almost filled with yellow. The gonadosomatic index (GSI) showed a statistically significant inverse correlation with the hepatopancreatic index (HPI) and muscle-somatic index (MSI). GSI significantly increased until stage III and HPI significantly decreased at stage II and recovered slowly thereafter. Nevertheless the MSI increased during the first two stages and decreased thereafter. A continuous decline in feeding intensity of females with ovarian development was found. The protein level in the muscle and hepatopancreas increased with protein accumulation in the ovary. Ovarian lipid concentration continued to increase, while, as in the hepatopancreas and muscle, lipid content decreased significantly at stage II and then recovered rapidly, followed by a sharp decline. Glycogen concentrations in the ovary kept steady, while in the hepatopancreas and muscle, there was a downward trend after a rise to the highest value. In conclusion, the energy for supporting ovarian development inevitably relies on energy reserves in the hepatopancreas and muscle and attention should be given to how to promote the transfer of organic reserves and energy to the ovaries during stock culture. • An accurate one-to-one correspondence between physical (and ovarian) morphology was established. • The visible colors of the median triangular structure of the telson can be used as an external morphological indicator of ovarian development status and the females are near ripe when median triangular structure is almost filled with yellow. • The gonadosomatic index (GSI) showed a statistically significant inverse correlation with the hepatopancreatic index (HPI) and muscle-somatic index (MSI). • A continuous decline in feeding intensity of females with ovarian development was found. • The energy for supporting ovarian development inevitably relies on energy reserves in the hepatopancreas and muscle. [ABSTRACT FROM AUTHOR]