Gene Expression Profiles in Two Razor Clam Populations: Discerning Drivers of Population Status

With rapidly changing marine ecosystems, shifts in abundance and distribution are being documented for a variety of intertidal species. We examined two adjacent populations of Pacific razor clams (Siliqua patula) in lower Cook Inlet, Alaska. One population (east) supported a sport and personal use fishery, but this has been closed since 2015 due to declines in abundance, and the second population (west) continues to support commercial and sport fisheries. We used gene expression to investigate potential causes of the east side decline, comparing razor clam physiological responses between east and west Cook Inlet. The target gene profile used was developed for razor clam populations in Alaska based on physiological responses to environmental stressors. In this study, we identified no differences of gene expression between east and west populations, leading to two potential conclusions: (1) differences in factors capable of influencing physiology exist between the east and west and are sufficient to influence razor clam populations but are not detected by the genes in our panel, or (2) physiological processes do not account for the differences in abundance, and other factors such as predation or changes in habitat may be impacting the east Cook Inlet population.

Research on Whipping and Jetting Combined Swimming Behavior of Solen strictus Gould

Solen strictus Gould are mainly cave dwellers, using their axe feet to dig caves. The Solen strictus Gould also exhibit escape-swimming behavior when food, environment, and so on changes. In this paper, Solen strictus Gould were captured on a high-speed camera as they escaped, and it was found that the Solen strictus Gould whipped while the water spout between the axe foot and the mantle sprayed water outwards. The combined propulsion of these two methods allows the Solen strictus Gould to advance rapidly in a short time. It is calculated that the swimming speed of razor clams is positively correlated with their size and that the adult Solen strictus Gould can travel up to 12 times their body length per second. This study enriches the data on the behavioral characteristics of Solen strictus Gould and is of interest regarding Solen strictus Gould in artificial farming, marine fishing, offshore ecological restoration, and underwater bionic robot development.

Brain mass explains prey size selection better than beak, gizzard and body size in a benthivorous duck species

Prey size selection in some bird species is determined by the size of the beak. However, we assumed for bird species swallowing whole prey that a cognitive process may be involved. As cognitive feature, brain mass was used. We hypothesized that the mass of the brain was more strongly positively correlated with prey size than morphological features such as beak volume, gizzard mass and body mass. We tested this hypothesis on eiders Somateria mollissima that swallow the prey whole, by using mean and maximum size of nine prey categories. Eiders were collected at the main wintering grounds in Denmark. As index of brain mass we used head volume, which is positively correlated with brain mass (r2 = 0.73). Head volume of eiders was significantly, positive correlated with mean and maximum size of blue mussels Mytilus edulis, razor clams Ensis directus and all prey sizes combined and the maximum size of draft whelk Hinia reticulata and conch Buccinum undatum. Gizzard mass was also significantly positively correlated with maximum size of draft whelk and conch. Beak volume and body mass was not significantly correlated with the size of any of the nine food items. Analyses of effect size for organs showed that head volume was positively related to prey size, whereas beak volume, gizzard mass and body mass did not show a significant positive relationship. These results indicate that cognitive processes connected to brain mass may be involved in prey size selection by eiders.

Variation in radical antioxidant capacity and the total amount of carotenoids in razor clams, Ensis marginatus (Pennant, 1777), from the Çanakkale Strait (Abidealtı), Turkey

Metabolic activities such as breathing and digestion, resulting from natural functions of the body through oxidation, lead to the formation of free radicals that cause cancer, premature cardiac aging and some chronic diseases. Antioxidants are substances that remove free radicals and prevent cell damage. Seafood significantly contributes to the elimination of free radicals, especially owing to its high quality nutrient content. In this context, the objective of the study was to determine the radical antioxidant capacity and the total amount of carotenes in razor clams. The IC50 (mg g−1) value of the DPPH radical sweeping effect varied over the months (p < 0.05), showing the highest value in June, gradually decreasing from September and reaching the lowest level in February. The total amount of carotenoids also varied, with the highest value in September (p < 0.05). The total amount of chlorophyll ranged from 6.15 μg g−1 in August to 66.71 μg g−1 in December.

Phylogeography and distribution of the freshwater razor clams Novaculina myanmarensis and N. gangetica in Myanmar, with notes on two doubtful nominal taxa described as Novaculina members (Bivalvia: Pharidae)

The razor clam genus Novaculina Benson, 1830 (Bivalvia: Pharidae: Pharellinae) is a group of secondary freshwater bivalves. Four allopatric species in this genus are distributed throughout Asian freshwater drainages from the Ganges River in India to the Yangtze River in China. Here, we present several new occurrences of Novaculina myanmarensis and N. gangetica from Myanmar that were confirmed by means of a molecular approach. These occurrences expand our knowledge on the ranges of both species. Furthermore, we compiled an updated distribution map for all the species in this genus. Our phylogeographic research suggests that Novaculina myanmarensis colonized the Ayeyarwady Basin from rivers of the Salween Estuary (Donthami and Ataran rivers) during the Late Pleistocene. Conversely, Novaculina gangetica populations from Myanmar does not demonstrate any clear phylogeographic structure. At first glance, this pattern can also be caused by a (sub)recent (Pleistocene) immigration into coastal rivers of western Myanmar from the Ganges Basin, although this preliminary hypothesis is yet to be confirmed using DNA sequences of samples from India and Bangladesh. Finally, the taxonomic status of two doubtful nominal taxa initially described as Novaculina members is discussed, i.e. N. gangetica theobaldi Hanley & Theobald, 1874 and N. andamanensis Preston, 1908. These taxa are considered junior subjective synonyms of the estuarine bivalve species Cultellus maximus (Gmelin, 1791) (Pharidae) and Azorinus coarctatus (Gmelin, 1791) (Solecurtidae), respectively.