9. THE CLASS CRUSTACEA
315
Other information. Humes (1954a) has stated that :
T . celata would seem to be a parasite of Mytilus edulis rather than a freeswimming species accidentally introduced into the mantle cavity, since it
occurs only in the mussel and then in relatively large numbers, and since the
presence of immature stages indicates it probably breeds in the mussel.
16. Lichomolgid Copepods
Humes and Cressey (1958) described three species of the family
Lichomolgidae from the mantle cavities of pelecypods of limited
commercial importance in West Africa. These are briefly mentioned a t
this point. They described Anthessius sp. from Pinna rudis taken a t a
depth of 1 m at Pointe-Noire, Congo; Modiolicola injlatipes from
Mytilus perna attached to rocks a t Pointe-Noire ; and Lichomolgus
arcanus from Ostrea tulipa collected at Joal, Senegal, and from Pitar
tumens collected at Hann, Senegal.
B. Subclass Malacostraca
Among the malacostracans, a number of decapods are known to
live symbiotically with commercially important marine molluscs, a t
least during one phase of their life cycles. Specifically, certain species
of crabs of the family Pinnotheridae are known t o live within the mantle
cavities of oysters and other pelecypods. Although the relationships
between these crabs and their hosts are not clearly understood, a t least
certain species are believed to be parasitic (see Chapter 4, Section 11,
A, 6). Since the nature of the relationship between pinnotherid crabs
and their hosts is a t best uncertain, the following information is limited
primarily to the more common species, especially those which have been
incriminated as being true parasites. For detailed information on the
entire family, the monographs of Rathbun (1918) and Sakai (1965)
should be consulted.
1. Pinnotheres ostreum Say, 1817. (Figs. 212-215)
(Order Decapoda; suborder Reptantia; section Brachyura; superfamily
The adults and post-planktonic stages of Pinnotheres ostreum, the
oyster crab, are found primarily in the mantle cavity of the American
oyster, Crassostrea virginica, but they can also occur in Aequipecten
and Anomia simplex (Christensen and McDermott, 1958) and in Mytilus
edulis (McDermott, 1961). They need not always be associated with
pelecypods since Gray (1960, 1961) has reported finding them occasionally in Chaetopterus tubes. P. ostreum is a New World species with its
known range extending from Massachusetts to Santa Catarina, Brazil
Brachyrhyncha; family Pinnotheridae)
315
Other information. Humes (1954a) has stated that :
T . celata would seem to be a parasite of Mytilus edulis rather than a freeswimming species accidentally introduced into the mantle cavity, since it
occurs only in the mussel and then in relatively large numbers, and since the
presence of immature stages indicates it probably breeds in the mussel.
16. Lichomolgid Copepods
Humes and Cressey (1958) described three species of the family
Lichomolgidae from the mantle cavities of pelecypods of limited
commercial importance in West Africa. These are briefly mentioned a t
this point. They described Anthessius sp. from Pinna rudis taken a t a
depth of 1 m at Pointe-Noire, Congo; Modiolicola injlatipes from
Mytilus perna attached to rocks a t Pointe-Noire ; and Lichomolgus
arcanus from Ostrea tulipa collected at Joal, Senegal, and from Pitar
tumens collected at Hann, Senegal.
B. Subclass Malacostraca
Among the malacostracans, a number of decapods are known to
live symbiotically with commercially important marine molluscs, a t
least during one phase of their life cycles. Specifically, certain species
of crabs of the family Pinnotheridae are known t o live within the mantle
cavities of oysters and other pelecypods. Although the relationships
between these crabs and their hosts are not clearly understood, a t least
certain species are believed to be parasitic (see Chapter 4, Section 11,
A, 6). Since the nature of the relationship between pinnotherid crabs
and their hosts is a t best uncertain, the following information is limited
primarily to the more common species, especially those which have been
incriminated as being true parasites. For detailed information on the
entire family, the monographs of Rathbun (1918) and Sakai (1965)
should be consulted.
1. Pinnotheres ostreum Say, 1817. (Figs. 212-215)
(Order Decapoda; suborder Reptantia; section Brachyura; superfamily
The adults and post-planktonic stages of Pinnotheres ostreum, the
oyster crab, are found primarily in the mantle cavity of the American
oyster, Crassostrea virginica, but they can also occur in Aequipecten
and Anomia simplex (Christensen and McDermott, 1958) and in Mytilus
edulis (McDermott, 1961). They need not always be associated with
pelecypods since Gray (1960, 1961) has reported finding them occasionally in Chaetopterus tubes. P. ostreum is a New World species with its
known range extending from Massachusetts to Santa Catarina, Brazil
Brachyrhyncha; family Pinnotheridae)