Embryonic and Early Larval Development of the Pacific Razor Clam (Siliqua patula).

AbstractThe Pacific razor clam, Siliqua patula (Sugpiaq: Cingtaataq, Dixon, 1789), is vital to commercial, recreational, and subsistence fisheries across the Pacific Northwest Coast of North America. Despite the species' status as one of the most popular shellfish species harvested in the Pacific Northwest, British Columbia, and Alaska, its larval development has never been fully characterized. Generating a developmental times series, and describing development fully, is crucial for guiding targeted management, developing a mariculture strategy for the species, and providing a more pointed avenue for studies examining the response of S. patula to ocean change. This study presents the first photographic documentation of larval development in S. patula, including the timing of key transitions during embryogenesis and early larval development. Scanning electron microscopy revealed that the larval shell forms via a concretion, a process typically documented in early gastropod development. This novel characterization is pertinent, as it conveys the need for the inclusion of alternative bivalve development processes, such as a concretion, in bivalve research. This study also compared development in S. patula to a global assortment of bivalve species, including two other members of the Pharidae family, determining that the timing to D-veliger and trochophore stages was similar to the majority of bivalves surveyed. While bivalve response to climate change is a topic of great interest, not all species of concern have undergone comprehensive developmental assessments, a requisite benchmark for designing climate change studies that examine early life history sensitivity to such changes. This research supports the use of comprehensive developmental studies as prerequisites for designing climate change experimentation, establishes the necessity of high-magnification and high-resolution scanning electron microscopy within developmental assessments, and provides information about the development of a cornerstone bivalve species.

On the Frontline: Tracking Ocean Acidification in an Alaskan Shellfish Hatchery.

The invasion of anthropogenic carbon dioxide (CO2) into the ocean is shifting the marine carbonate system such that saturation states of calcium carbonate (CaCO3) minerals are decreasing, and this is having a detrimental impact on early life stages of select shellfish species. The global, secular decrease in CaCO3 saturation states is occurring on top of a backdrop of large natural variability in coastal settings; progressively shifting the envelope of variability and leading to longer and more frequent exposure to adverse conditions. This is a great concern in the State of Alaska, a high-latitude setting vulnerable to rapid changes in the marine carbonate system, where an emerging shellfish industry plans major growth over the coming decades. Currently, the Alutiiq Pride Shellfish Hatchery (APSH) in Seward, Alaska is the only hatchery in the state, and produces many shellfish species with early life stages known to be sensitive to low CaCO3 saturation states. Here we present the first land-based OA measurements made in an Alaskan shellfish hatchery, and detail the trends in the saturation state of aragonite (Ωarag), the more soluble form of CaCO3, over a 10-month period in the APSH seawater supply. These data indicate the largest changes are on the seasonal time scale, with extended periods of sub-optimal Ωarag levels (Ωarag < 1.5) in winter and autumn associated with elevated water column respiration and short-lived runoff events, respectively. The data pinpoint a 5-month window of reprieve with favorable Ωarag conditions above the sub-optimal Ωarag threshold, which under predicted upper-bound CO2 emissions trajectories is estimated to close by 2040. To date, many species in production at APSH remain untested in their response to OA, and the data presented here establish the current conditions at APSH as well as provide a framework for hatchery-based measurements in Alaska. The current and expected conditions seen at APSH are essential to consider for this developing Alaskan industry.