FAO Species Identification Guide for Fishery Purposes Western

Infraorder Caridea 957
Infraorder Caridea Infraorder CARIDEA
Caridean shrimps
Diagnostic characters: Very small to
large-sized, with a body length from 0.5 to
32 cm. All 5 pairs of legs well developed, the
first 2 pairs with or without a pincer, but third
leg never bearing a pincer. Second abdominal
pleuron (lateral plate) greatly expanded,
pear-shaped and overlapping
posterior part of first pleuron as well as
anterior part of third pleuron. Males and
females without large copulatory organ on
first pair of pleopods (abdominal appendages)
or posterior thoracic sternites, respectively.
Females carry the eggs on the abdomen
until hatching.
3
Habitat, biology, and fisheries: This large
infraorder contains at least 2 517 species in 28
families (the number of families in this infraorder
is controversial among crustacean taxonomists).
They can occur in all kinds of aquatic
habitats such as high mountain streams (at
altitudes of more than 2 500 m), lakes, caves, exopod
underground waters, rivers, estuaries, littoral
exopod
appendix
zones, beaches, bays, coral reefs, continental
interna
shelves, and the deep sea (at depths of at least
appendix
6 364 m, perhaps even 10 912 m for a red
interna
“shrimp” sighted by a bathyscaphe at Chal-
endopod
lenger Deep, near Guam). A few species inhabit
the upper littoral zone and are able to endopod
endure short periods of desiccation. Both ben-
appendix
male masculina
female
thic and/or pelagic (including epi- and bathypelagic)
ways of life are found in members of
second abdominal leg (pleopod)
this infraorder, and a large number of marine
species live in symbiosis with other invertebrates or fishes. The sexes are generally separated, but certain
species, such as some Pandalus, commonly first undergo a male phase and later transform into females.
The gonopores are situated at the bases of fifth or third leg in males and females, respectively. However,
as many caridean shrimps are of very small size, with the thoracic sternum being narrow, sexing caridean
shrimps by observing the position of gonopores is often difficult. A more simple way to distinguish the sexes
of caridean shrimps is to determine the presence or absence of the so-called appendix masculina on the
second pleopods (or abdominal appendages; see figure above). In females, the endopod of the second
pair of pleopods bears an appendix interna only. In males, the endopod of the second pleopods usually
has an appendix interna as well, but additionally bears an appendix masculina, which, when observed
under magnification, is distinct, even in juveniles. Besides, a remarkable sexual dimorphism (e.g. the size
of the second pincer, the curvature of the rostrum, the shape of the abdominal pleura, etc.) is present in
many species, but such a dimorphism is often specific and not necessarily the same in different species.
The females of caridean shrimps carry the eggs on the abdomen. Their larvae leave the eggs in relatively
advanced stages (i.e. lacking the nauplius stage) and some even directly as juveniles.
At present, 22 families of caridean shrimps are known to occur in the Western Central Pacific, but the
exact number of species in the area is unclear. This is mainly due to fact that most of them are without
any economic importance and therefore, have rarely been studied. However, recent extensive studies
on carideans from the Philippines and adjacent areas have shown that 528 species are found in that
region alone. Despite the large number of species, most caridean shrimps are small and do not occur in
sufficient quantities to be actively fished, and/or live in very deep sea. Therefore, they are generally of
no commercial importance in the Western Central Pacific. So far, only the giant river prawn Macrobrachium
rosenbergii is both actively fished and extensively cultured in the area. It is mainly marketed
live or fresh for local consumption, sometimes also exported. Several other fresh-water and coastal
caridean shrimps in the area also have a relatively larger size or are easy to catch, and are likely to be
used as food by natives in several countries. However, information on local use of caridean shrimps is
mostly lacking and the exact identities of the species in question are often uncertain and/or confusing in
literature. On the other hand, some deep-sea caridean shrimps, mostly belonging to the family Pandalidae
rd leg without
2
pincer
females carry eggs
on abdomen
nd pleuron
pear-shaped