''Mizuhopecten yessoensis'' (Yesso scallop, giant Ezo scallop) is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of marine bivalve

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Pectinidae, the scallops. Its name Yesso/

Ezo (also spelled Yezo or Yeso) is the Japanese term historically used to refer to the lands to the north of the Japanese island of Honshu. It included the northern Japanese island of Hokkaido, which changed its name from "Ezo" to "Hokkaidō" in 18 ...

refers to its being found north of Japan. Its tissues

bioaccumulate Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

algal

yessotoxin Yessotoxins are a group of lipophilic, sulfur bearing polyether toxins that are related to ciguatoxins. They are produced by a variety of dinoflagellates, most notably ''Lingulodinium polyedrum'' and '' Gonyaulax spinifera''. When the environm ...

s and are studied extensively.

Description

The Yesso scallop (''Mizuhopecten yessoensis'') is a cold water marine bivalve species. The valves have a convex center with a smooth exterior shell. On one side it is white and on the other dark brown.

Habitat

The Yesso scallop is widely distributed along the cold coast of Northern Japan. Scallop cultivation is located in the northern islands of

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island se ...

and

Hokkaido is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The lar ...

, with the Sea of Okhotsk, Saroma Lake and Funka Bay in Hokkaido accounting for more than 80% of the scallop production during the period of 1991 to 2002.

Ecology and behavior

Temperature plays a key role in the timing of spawning and larvae settlement of the Yesso scallop. Generally, the scallops spawn between May 1 to June 9 over the span of 10 days. It was found that the timing for the commencement of spawning is shifted to a later date when the surface temperature of the water remains below 0

°C The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...

for a prolonged period. In addition, lower temperatures throughout April could potentially influence the onset timing of scallop spawning. Furthermore, the shortening of pre-spawning period (dates between the surface water temperature rise above zero to May 1) may be another contributing factor to the later dates of spawning. On the other hand, the timing of scallop spat settlement is closely related to water temperature too; the colder the pre-spawning period, the later the larvae settlement. The commencement of the Yesso Scallop larvae settlement is typically between June 4 to July 5 over the period of 15 days. The upper limit for scallop development was found to be 18

Development

The growth of scallops also varies with the water temperature. When the water is warm and below 18

, the scallops tend to grow most rapidly between the age of 2 and 4. On the other hand, they often reach the peak of their growing ability between 3 to 5 years of age in colder environments. Consequently, it was established that the Japanese scallop ''Mizuhopecten yessoensis'' experiences the lowest

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...

between the age of 2 and 5. Starting from the age of 6 to 7, the

rises dramatically.

Predation

The main predators of the Yesso scallops are the sea stars '' Asterias amurensis'' and '' Distolasterias nipon''. The scallops are preyed on one after the other, and it was found that smaller scallops are preferred over larger ones. Scallops found in warmer waters are also more likely to be preyed upon. Due to the morphological differences between ''D. nipon'' and '' A. amurensis'', ''D. nipon'' had a much greater influence on the predation of the Yesso scallops.

Diet

The scallops depend on sinking organic matter for food, with detritus being their main source of food. These organic matter are from rivers being drained nearby. Another source of food for the scallops are

dissolved organic carbon Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called partic ...

from phytoplankton production.

References

{{Taxonbar, from=Q1132485 Pectinidae Commercial molluscs Bivalves described in 1857