Original Article
Fish Aquat Sci 15(4), 299-303, 2012
Histological Observations and Regeneration of Barbels in
Juveniles of the Chinese Longsnout Catfish Leiocassis
longirostris
In-Seok Park1*, Chi-Hong Kim2 and Jae Wook Choi1
Division of Marine Environment and Bioscience, College of Ocean Science and Technology, Korea Maritime University,
Busan 606-791, Korea
2
Inland Fisheries Ecological Research Institute, National Fisheries Research and Development Institute, Gapyeong 477-815, Korea
1
Abstract
Barbel structure and regenerated barbel length in the juvenile Chinese longsnout catfish Leiocassis longirostris (Günther), were
evaluated. The barbles consisted of an epidermis, a dermis, and a central rod. The epidermis harbored taste buds, granular cells and
epidermal cells. The taste buds were basophilic and situated along the distal portion of the epidermis. The dermis was composed
of loose connective tissue containing blood vessels pigment cells. The innermost central region was cartilage enclosed within layers of muscle layers. After 30 days, the regenerated barbel length measured 0.92 ± 0.404 mm at 15°C (regenerated growth curve:
y = 0.5085x + 4.0678, r² = 0.9654, where y is regenerated length and x is experimental period in days), 1.88 ± 0.521 mm at 20°C
(y = 0.1806x + 4.808, r² = 0.9822), and 6.44 ± 0.751 mm at 25°C (y = 0.0914x + 4.9918, r² = 0.9944). Fifteen days after amputation, the regenerated length was significantly longer at 25°C than at 15 or 20°C (P < 0.05). The barbels of the Chinese longsnout
catfish was the tender and flexible type, and our experimental findings provide evidence of temperature-dependent regeneration.
Additional investigation of the behavior and physiology of the Chinese longsnout catfish is needed, particularly histological studies of regenerated barbels and the measurements of the numbers of taste buds per barbel under various environmental conditions.
Key words: Leiocassis longirostris, Chinese longsnout catfish Barbel, Histology, Regeneration
Introduction
2001; Park and Kim, 2005; Park et al., 2005, 2006).
Barbels also have the ability to regenerate after amputation,
similar to the tails of salamanders. Nerves in the barbel are
likely related to the regenerative ability. In a study of the effects of nerves on the maintenance of taste buds, Olmstead
(1920) reported that injured barbels did not regenerate completely when denervated.
The Chinese longsnout catfish Leiocassis longirostris
(Günther) is a benthic freshwater fish that inhabits the sandy bottoms of lakes throughout China and Korea (Kim and
Park, 2002). It was not found in Korea prior to 2007 because
A wide variety of marine and freshwater fish possess externally situated appendages, which are referred to as the barbels.
Barbels are accessory feeding structures, that harbor sensory
organs and perform functions important to the daily activities
of fish (Kapoor and Bhargava, 1967; Park et al., 2005, 2006).
The number, length, and position of barbels vary markedly
(Park et al., 2005), and their histological structures have been
compared among several fish species (Satō and Kapoor, 1957;
Nagar and Mathur, 1958; Srivastava and Sinha, 1961; Agarwal and Rajbanshi, 1965; Rajbanshi, 1966; Kapoor and Bhargava, 1967; Singh and Kapoor, 1967; Satō, 1977; Kim et al.,
Open Access
Received 3 January 2012; Revised 9 November 2012
Accepted 3 December 2012
http://dx.doi.org/10.5657/FAS.2012.0299
This is an Open Access article distributed under the terms of the Creative
Commons Attribution Non-Commercial License (http://creativecommons.
org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use,
distribution, and reproduction in any medium, provided the original work
is properly cited.
pISSN: 2234-1749 eISSN: 2234-1757
Copyright © The Korean Society of Fisheries and Aquatic Science
*Corresponding Author
E-mail: [email protected]
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Fish Aquat Sci 15(4), 299-303, 2012
of pollution and development (Kim and Park, 2002), but the
Chinese longsnout catfish was recently re-introduced to Korea
from Chinese stocks. In 2007, artificial breeding succeeded,
suggesting that aquaculture of this species would soon be
possible. The Chinese longsnout catfish harbors four pairs of
barbels. According to Kapoor and Bhargava (1967), its barbel is a tender and flexible type. Similar to the barbels of the
striped eel catfish, Plotosus lineatus, and the amblycipitidae
Liobagrus andersoni, both of the Siluridae family, the barbels
of the Chinese longsnout catfish offer gustatory sensibility and
function in locating prey (Park et.al., 2005, 2006). However,
barbel structure and regeneration in the Chinese longsnout
catfish have yet to be elucidated. The objective of the present
work was to determine the structure and regeneration properties of the barbel of the Chinese longsnout catfish a member of
the Bagridae family.
A
B
Materials and Methods
In the present study, we used juvenile specimens of the
Chinese longsnout catfish Leiocassis longriostris, which were
acquired from the Central Inland Fisheries Research Institute,
National Fisheries Research and Development Institute (NFRDI) in Korea. The mean standard length of the study fish was
15.6 ± 2.11 cm (n = 35).
Fig. 1.
The Chinese longsnout catfish Leiocassis longriostris with four
pairs of barbells. (A) Dorsal view of head. (B) Ventral view of head showing
3 pairs of Barbells. The arrows indicate a pair of mandibular barbells. Scale
bars = 10 mm.
Histological observations
Eight specimens were used for histological observations.
Specimens were fixed in 10% neutral-buffered formaldehyde.
Barbels were dehydrated via a standard ethanol series to 100%,
cleared in xylene, and then embedded in paraffin. Sections of
6-μm thickness were deparaffinized and stained using Mayer’s
hematoxylin and eosin. Observations and evaluations were
conducted under a light microscope (Serien-Nr: 3109000586
Axiostar Plus; Carl Zeiss, Oberkochen, Germany).
Statistical analysis
One-way ANOVA and Duncan’s multiple range test (Duncan, 1955) were used to assess the significance of differences
among the mean lengths at the three temperatures. Statistical
analyses were performed with SPSS version 9.0 (SPSS Inc.,
Chicago, IL, USA).
Regeneration of barbels
Results
The Chinese longsnout catfish harbors four pairs of barbels
(Fig. 1), but regeneration was observed only for the longest
barbel, which was proximal to the mandibular snout (a in Fig.
1B). Twenty-seven fish were acclimated in nine 40-L tanks,
each of which held three fish. The fish were provided food pellets daily. Barbel regeneration was observed at three different
temperatures (15, 20 and 25°C), with three replicate tanks for
each temperature. The mean mandibular snout barbel length
was 13.1 ± 0.32 mm prior to amputation. Amputation was accomplished by clipping 5 mm from the upper side of the basal
barbel. Barbel length was then measured every 3 days over a
30-day period, using digital vernier calipers (CD-20CP; Mitutuyo, Kawasaki, Japan).
http://dx.doi.org/10.5657/FAS.2012.0299
We noted no structural differences among the barbels of the
Chinese longsnout catfish Leiocassis longriostris. All barbels
consisted of three principal layers: an epidermis, a dermis, and
a central axis of cartilage (axial rod) (Fig. 2A). As shown in
Fig. 2, the epidermal layer was composed of stratified epidermal cells having a spherical or ovoid shape in the surface layer
and a columnar in shape in the basal layer.
In the surface of the epidermis, a number of taste buds were
scattered among the epidermal cells (Fig. 2B and 2C). The
taste buds varied in size and were flush with or even crossed
the periphery, lying closer to the distal portion than the proximal portion of the barbel. The taste buds were basophilic. Also
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Park et al. (2012) Histology and Regeneration of Barbel in L. longirostris
among the epidermal cells, we noted granular cells with deeply stained nuclei and small quantities of faintly stained cytoplasm. The dermis was separated from the epidermal layer by
a basement membrane and was composed of loose connective
fibers that harbored abundant blood vessels and pigment cells
(Fig. 2D-2F). The pigment cells were scattered throughout the
superficial dermis (Fig. 2D).
An axial rod consisting of cartilaginous tissue was located
at the innermost region of the barbel (Fig. 2B and 2E) and
formed a “supporting rod” for the barbel. The cartilage cells
had irregular shapes with a nucleus in the center (Fig. 2E), and
the cartilaginous tissue contained a small amount of ground
substance contatining dispersed fibers. The axial rod was ensheathed by an inner circular layer of muscle and several bundles of longitudinal muscle, which were in turn surrounded by
a circular layer of smooth muscles (Fig. 2E and 2F).
A
B
C
D
E
F
Fig. 2. Structure of barbel of Chinese longsnout catfish Leiocassis longirostris. (A) Cross section of the mandibular barbel showing the structure of the axial
rod of cartilage, dermis, and epidermis. (B) Longitudinal section of the maxillary barbell. (C) Taste bud and basement membrane. (D) Dermis and pigment
cell. (E) Axial rod of cartilage, loose connectine tissue, and smooth muscle layer. (F) Blood vessel. ar, axial rod of cartilage; bm, basement membrane; bv, blood
vessel; ct, loose connective tissue; d, dermis; ep, epidermis; ml, smooth muscle layer; pc, pigment cell; tb, taste bud. Scale bars: A, B = 40 μm, C-F = 10 μm.
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Fish Aquat Sci 15(4), 299-303, 2012
tions, the barbel of the Chinese longsnout catfish is the tender
and flexible type.
In catfishes, including the striped eel catfish, tender and
flexible barbels have gustatory sensibility and function in
the location of prey (Singh and Kapoor, 1967, Park and Kim
2005). The epidermis of the Chinese longsnout catfish barbel
contains taste buds buried among the epidermal cells. Typically, taste buds control gustatory secretions by mucous and
club cells. However, the Chinese longsnout catfish did not
appear to have mucous cells or club cells. Consequently, the
barbels of Chinese longsnout catfish are probably restricted to
gustatory functions.
Singh and Kapoor (1967) demonstrated that mucous cells
in the barbels secrete mucus for protection and escape from
predators. Taste buds and club cells in the skin of the barbel
have been described in the marine catfish Arius thalassinus
(Kapoor and Bhargava, 1967). In addition, taste buds, mucous cells and club cells have been observed in the barbels
of Callichrous bimaculatus, Heteropneustes fossilis, Clarias
batrachus and Rita rita (Satō and Kapoor, 1957; Srivastava
and Sinha, 1961; Singh and Kapoor, 1967). Taste buds were
also detected in the barbels of Bagarius bagarius and Blepsias
cirrohosus draciscus (Nagar and Mathur, 1958; Satō, 1977).
Taste buds, mucous cells, and club cells were not detected in
the barbels of Mystus vittatus; thus, the barbels were restricted
to tactile, and not gustatory, functions (Agarwal and Rajbanshi, 1965).
The regeneration of fish barbels has been well documented.
After amputation catfish barbels regenerate nerves, cartilage,
connective tissue, epidermis, and taste buds, all of which
are dependent upon the regeneration of nerves (Kamrin and
Singer, 1953, 1955). A recent study has shown that the small
chin barbell of Lota lota can regenerate several millimeters
in length within 3 months following transection at the base
(Cochran, 1987). Whitear (1990) demonstrated that within 2
days following the amputation of the barbell in H. fossilis, the
stump was covered by epidermis; by the third day, regenerated tissues were detected. After 5 days, 1-1.5 mm of regenerated tissue were detected; after 7-8 days, 2.4-3.5 mm were
observed, corresponding to approximately 0.5 mm of growth
per day (Whitear, 1990). The axis harbored blood vessels, regenerated nerves with Schwann cells, fibroblasts, and collagen, but no cartilaginous skeleton. Tissue remodeling included
simultaneous phagocytosis and the synthesis of collagen by
fibroblasts (Whitear, 1990). Although the regenerated region
in the present study was not examined histologically its regenerative capacity was similar to that of other species, considering that the Chinese longsnout catfish was a juvenile.
May (1925) demonstrated that after nerve section, the regeneration of taste buds begins only after the regenerated
barbel nerve reaches the area of the degenerated taste buds;
a nerve factor was thought to have influenced the growth and
integrity of the taste buds. This was also demonstrated by Kamrin and Singer (1955) for the regeneration and maintenance
11
15˚C : y = 0.5085x + 4.0678
r2 = 0.9654
10
Regenerated length (mm)
*
*
20˚C : y = 0.1806x + 4.808
r2 = 0.9822
9
*
25˚C : y = 0.0914x + 4.9918
r2 = 0.9944
8
*
*
*
7
6
5
0
3
6
9
12
15
18
21
24
27
30
Experiment period (days)
Fig. 3. Regenerated growth curve of barbel of Chinese longsnout
catfish Leiocassis longirostris during 30 days at 15, 20 and 25°C. Vertical
bars indicate standard deviations. Superscripts are significantly different (P
< 0.05).
After the 30-day experimental period, the length of the barbel regenerated at 15°C was 0.92 ± 0.404 mm (regenerated
growth curve: y = 0.5085x + 4.0678, r² = 0.9654, where y
is the regenerated length, and x is the experimental period in
days) (Fig. 3). The regenerated barbel length was 1.88 ± 0.521
mm at 20°C (regenerated growth curve: y = 0.1806x + 4.808,
r² = 0.9822) and 6.44 ± 0.751 mm (regenerated growth curve:
y = 0.0914x + 4.9918, r² = 0.9944) (Fig. 3). Fifteen days after
amputation, the regenerated length was significantly longer at
25°C than at 15 or 20°C (P < 0.05).
Discussion
The barbels of fish are fleshy and elongated structures that
harbor tactile and chemosensory receptors, and some speciesspecific differences have been observed (Bond, 1996). In particular, the movable barbels of some catfishes appear to serve
an important function in food localization (Singh and Kapoor,
1967). The substantial gustatory sensitivity of the barbels extends the usefulness of these chemoreceptors a reasonable distance from the fish, which presumably facilitates the location
of food in murky water (Moyle and Cech, 2000).
Kapoor and Bhargava (1967) classified barbels into two
types: 1) tender and yielding barbels, which lack an axial cartilaginous rod and have a dermis harboring a network of blood
vessels and 2) stiff barbels which can be motionless or flexible. Motionless stiff barbels have a supporting axis of true
bone, whereas flexible stiff barbels contain a cartilaginous
axis. The barbels of the Chinese longsnout catfish Leiocassis
longirostris have an epidermis with taste buds and epidermal
cells, a dermis containing plentiful blood vessels, and an axial
cartilaginous rod. In accordance with the above classifica-
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Park et al. (2012) Histology and Regeneration of Barbel in L. longirostris
of the barbel of catfish. Kamrin and Singer (1955) used normal
regeneration of the barbel as a control for comparison with
regeneration of denervated and amputated barbels and denervated but not amputated barbels. Their results confirmed the
regenerative abilities of barbels and the dependence of regeneration upon nerve supply. Moreover, barbels that were denervated but not amputated regressed in the absence of nerves
(Kamrin and Singer, 1953).
These previous results were verified by Olivo (1928) and
Torrey (1934, 1936), who demonstrated that low temperature
inhibits nerve regeneration and hence the reappearance of the
taste buds. The optimal temperature for this process was determined to be 20°C, Suggesting that the causative factor may be
an enzyme. Temperature-dependent barbel regeneration also
occurred in the present study; low temperature inhabited nerve
regeneration in the barbels, and barbel regeneration at 25°C
was attributed to active metabolism, most notably enzymatic
activity.
Based on the present study, the barbels of the Chinese
longsnout catfish are the tender and flexible type, and exhibit
temperature-dependent regeneration. However, these results
do not fully elucidate the physiology of barbels in the Chinese
longsnout catfish, and future work should include histological studies of regenerated barbels and measurements of the
numbers taste buds per barbel under various environmental
conditions.
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Kapoor BG and Bhargava SC. 1967. A study on the barbels of a marine
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Kim IS, Kim SY and Park JY. 2001. Histological observation of the
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Acknowledgments
This research was funded through project No. 20100021293 of the National Research Foundation of Korea. Comments from anonymous reviews greatly improved the quality
of this manuscript.
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