ISSN 10630740, Russian Journal of Marine Biology, 2016, Vol. 42, No. 1, pp. 51–57. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © R.R. Borisov, 2016, published in Biologiya Morya.
Setae of decapod crustaceans manifest a variety of
structures and perform numerous functions, from
mechanical cleaning of the body surface and providing
water flows to chemo and mechanoreception. Quite a
large number of works have been dedicated to the
morphology and functions of setae in adult [11, 17, 19,
20, etc.], as well as in larval and juvenile decapods [8,
16, etc.]. Less is known about the pattern of changes
that mouthpart setae undergo in the course of individ
ual development [15, 18].
The red king crab
sius, 1815) is of great commercial significance both in
the Far Eastern seas and in the Barents Sea [1, 2]. It is
one of the largest members of not only the decapods,
but also arthropods. Juvenile and adult crabs differ
insignificantly in their general structural plans,
whereas the body size of individuals may increase by
100 times or more while they are growing. This makes
it possible to use the red king crab as a unique object to
study changes that occur during its ontogeny.
The goal of this work is to determine how the setal
armament on the mouthparts changes in order to
maintain the effectiveness of their functions in the
course of individual development. The results of the
study will enable us to better understand the principles
of the formation of setal armament in decapods.
MATERIALS AND METHODS
For this work, we used red king crabs of the Barents
Sea population. The structure and distribution of setae
on their mouthparts were studied in males with a car
apace width (CW) from 1.8 (first stage juveniles) to
220 mm (large mature individuals). The CW was used
as the size parameter, as it correlates well with the body
weight and is widely applied in studies of commercial
red king crab populations.
Two types of structures are found on the surface of
setae: denticles and setules . Denticles are hard,
flattened, and characterized by smooth edges; they do
not have an articulation with the setal shaft and are fre
quently arranged into two parallel rows. The appear
ance of setules is more diverse: from long and thin flat
tened filaments to short plates with the serrated or
smooth edge. As a rule, setules have an articulation
with the setal shaft.
To describe and classify setae on the red king crab
we used the system that was proposed by Garm
[10, 12] for decapods, which includes seven main
types of setae. The plumose seta bears two rows of long
setules along all of its length; this is the only seta type
in which the articulation with the cuticle is elevated.
The pappose seta has long setules that are arranged
randomly or into several rows along its length, which
grow shorter towards the end of the seta. The pappos
errate seta looks similar to the pappose type, but set
ules in its distal portion are transformed into two rows
of denticles; short setules may also be present in the
Changes of the Setae on the Mouthparts of the Red King Crab
(Tilesius, 1815) (Decapoda: Lithodidae)
R. R. Borisov
Russian Scientific Research Institute of Fisheries and Oceanography, ul. Verkhnyaya Krasnosel’skaya 17, Moscow, 107140 Russia
Received April 23, 2015
—Setae on the mouthparts of juvenile and adult red king crabs,
1815), were studied. A total of seven types of setae have been differentiated; their distribution over the mouth
parts was determined. It was established that setules and denticles on the surface of setae show a tendency to
shorten and/or disappear as the body grows; the length of the setae decreases relative to the size of the indi
vidual; the number of setae of most types increases considerably, forming dense groups of setae. These
changes are apparently related to the fact that the effectiveness of the functions that are performed by solitary
setae decreases with the growth in the size of an individual; these functions are subsequently assumed by
groups of setae.
: red king crab,
setae, morphology, ontogeny