The life cycle
of the hard calm
In general, most
calms reproduce in wild similar the Northern
The hard clam can
live up to 30 years and grow to (on average) 4
inches in length.
But, like all
living things, they have to start somewhere.
Hard clams begin
their adult lives as males. In successive
years they may change their sex and produce
Sperm cells are
much smaller than eggs and require less
metabolic energy to produce. Larger clams
grow at a much slower rate so more metabolic
energy can be devoted to the production of sex
cells, thus the switch to the larger eggs.
By the time hard
clams reach harvestable size, there is about a 1
to 1 ratio of males to females.
In the spring when
the bay water temperature rises above 50°F,
clams come out of "hibernation" and begin to
feed on available
phytoplankton. In late spring into
early summer when the water temperature rises
above 68°F the adults begin to spawn.
males release sperm and females release eggs
through their excurrent siphons into the bay.
takes place in the water column as sperm and egg
unite. (right image)
the fertilized egg develops the cells divide and
Pictured from left
to right are:
cell division, the four-cell embryo and
As the embryo
grows, the next stage is a ball of cells called
It is derived from
the Latin word for mulberry, which it resembles.
development we see the growth of hair-like
and the embryo becomes a free-swimming larva
known as a trocophore.
The image on the
left depicts the early larval stage while the
image on the right shows the fully developed
this stage could take from 18 to 48 hours
depending upon water temperature
the larva begins to develop a shell and foot. In
this stage, the larva is called a veliger.
The D-shaped or
strait-hinged veliger (left image) is so called
the body side where the hinge is forming is
straight while the open valve side is rounded.
The larval shell
of the of the umbonate veliger (right
image) has the characteristic triangular shape
of the hard clam.
last phase of the veliger stage is called the
The pediveliger (ped = foot) stage.
This is the final
stage prior to settlement and eventual
metamorphosis to juveniles.
a well-developed foot that extends from the
as a juvenile, the calm has now grown enough and
is ready to continue life in the bay bottom.
The weight of the shell prevents drifting and
the clam settles to the bottom (sets) and uses
its foot to dig in and extends its siphons to
this stage from the trocophore stage may last from 8
days to 2 weeks
depending upon water temperature.
Fun Fact -
In New Jersey, the minimum size of hard clams
that may be harvested is 1 1/2 (1.5) inches in length.
Clams can reproduce at about 1 to 1 1/4
inch in length
which gives them "protected time" to breed.
Fun Fact -
The hard clam is active and grows in water
temperature between 50° and 85° Fahrenheit.
Above or below those temperatures they shut down