Histological Study of Respiratory Organ of Betta sp.

Abstract

Betta sp. is a freshwater ornamental fish which also known as a fighting fish. One of the fundamental organs to support fishes life is respiratory organ. Fighting fish is belongs to the suborder Anabantoidei which means labyrinth fishes group. The aim of the study was to know histology of the respiratory organs of Betta sp. Histological preparations were done using paraffin method, stained with Hematoxylin-Eosin (HE). The result showed that Betta sp. has a respiratory organ common fish i.e gills and additional respiratory organ structure namely labyrinth and pseudobranch that makes Betta sp can survive in a low volume of water. The gill is consists of gill arch, gill raker, gill fillament and gill lamellae. The labyrinth is consist of connective tissue and folded ephitelium. Pseudobranch according to some literature function as an additional respiratory. Functions attributed to the pseudobranch include; regulation of oxygen to the eyes, enzyme production for use in the gas bladder, osmoregulation, and many others.

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ISSN 2597-5250
Volume 2, 2019 | Pages: 181-184 EISSN 2598-232X
Histological Study of Respiratory Organ of Betta sp.
Nurul Safitri Apriliani1,2*, Hikmah Supriyati3, M. Ja’far Luthfi3
1Center for Integrative Zoology, 2Biology Department, 3Biology Education Department, Faculty of Science and Technology, UIN Sunan Kalijaga
Jl. Marsda Adisucipto No. 1 Yogyakarta 55281, Indonesia. Tel. + 62-274-540971, Fax. + 62-274-519739
1Email: nurulapriliani89@gmail.com
Abstract. Betta sp. is a freshwater ornamental fish which also known as a fighting fish. One of the fundamental organs to support fishes
life is respiratory organ. Fighting fish is belongs to the suborder Anabantoidei which means labyrinth fishes group. The aim of the study
was to know histology of the respiratory organs of Betta sp. Histological preparations were done using paraffin method, stained with
Hematoxylin-Eosin (HE). The result showed that Betta sp. has a respiratory organ common fish i.e gills and additional respiratory organ
structure namely labyrinth and pseudobranch that makes Betta sp can survive in a low volume of water. The gill is consists of gill arch,
gill raker, gill fillament and gill lamellae. The labyrinth is consist of connective tissue and folded ephitelium. Pseudobranch according to
some literature function as an additional respiratory. Functions attributed to the pseudobranch include; regulation of oxygen to the eyes,
enzyme production for use in the gas bladder, osmoregulation, and many others.
Keywords: Betta sp., Fighting fish, Histology, Labyrinth, Pseudobranch, Respiration
INTRODUCTION
Betta sp. is a freshwater fish that has a special
character, such as its aggressiveness to hold their
territory from their fellow. Betta sp. has high survivor
rates in a low volume of water with no air circulator
(aerator). The fundamental organ to support the fish in
that environment is respiratory system organ.
Respiration is a physiological process by which
organisms exchange gases (oxygen and carbon dioxide)
from the environment. It is taking place between blood
and water through the medium of respiratory. This
process is also known as an internal respiration process.
The organ who take a respiratory system work as well
is gill and other additional structure respiratory.
The gills of some fish species can compensate for
ambient oxygen changes by exhibiting morphological
and functional plasticity that give the gill the ability to
modify its structure. Previous studies reveal aquatic air-
breathing fish with accessory air-breathing organ (the
labyrinth organ).
Air-breathing fish are defined as fish that have the
ability to exchange gases directly from the aerial
environment, and these all have an accessory air-
breathing organ (Graham, 1997). They are classified
into amphibious and aquatic air-breathing fishes. The
accessory air-breathing organs are alternative gas
exchange organs that are found in many different
tissues including the labyrinth organ, skin, lungs,
respiratory gas bladders, digestive tracts and structures
derived from buccal, pharyngeal and branchial cavities
from several different phylogenetic lineages (Graham,
1997). The species in the Anabantoidei have the
labyrinth organ as an accessory air-breathing organ and
possess branchial and systemic circuits similar to a
double-circuit circulatory system (Munshi et al., 1986;
Olson et al., 1986).
The other characteristic of Betta sp. that enable
them to survive in the low water volume is a respiratory
modification in the form of an air chamber filled with
plates or leaflets of respiratory epithelium located
above the gills and functioning adjuncts to them in
obtaining oxygen. This adaption and variations of it are
not uncommon in organisms which have become
adapted to water which is frequently low in oxygen
content.
Until recently the classification for the Betta was
Anabantidae. Anabantid fishes are found throughout
southeastern Asia as far north as northern China and
Korea and including the Philippines and the Malayan
archipelago to, and though, southern and western
Africa. The Asian and African forms are somewhat
distinct and the African forms are not known. Genus
Betta has Asiatic distribution. Some are widely
distributed, but according to Smith (1945) Betta
splendens appears to be found in the wild state only in
Siam (Thailand). It may be that they were widely
distributed artificially for possible mosquito control at
an early date, making it difficult to accurately
determine their natural range.
Labyrinth fish are endemic to freshwaters
of Asia and Africa. In Asia, they are found throughout
East, Southeast, and South Asia, especially but not
exclusively in the warm, slow-flowing, low-oxygen
waters. In Africa, significantly smaller numbers of
labyrinth fish can be found in the southern half of the
continent, with concentrate in the rainforest waters. The
characteristics of the fish habitats are indicators of the
size of the labyrinth organ, as the organ size is
negatively correlated with the level of oxygen in the
waters. Species native to low-oxygen waters are more
likely to have larger and more complex labyrinth
organs than species found in fast-flowing, oxygen-rich
waters (Pinter, 1986).

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This paper aimed to investigated histological and
functional changes in the respiratory organs (gills and
additional organs/labyrinth) of the aquatic air-breathing
fish Betta splendens. The purpose of this research is to
know the histology of gill as main respiratory organ
and to know histology of labyrinth and pseudobranch
as an additional respiratory organ of Betta splendens.
MATERIALS AND METHODS
The animals used in this study were three Betta fishes
obtained from Market fish, Balirejo, Yogyakarta. The
material used were bouin, decal solution, toluene,
xylol, paraffin, ethanol, hematoxylin-eosin, glycerin,
and entellan. The equipment used in this study were
dissection kit, paraffin tub, flacon bottles, oven
paraffin, staining jar, cassettes, beaker 250 ml, and 50
ml, measuring cup 100ml, funnel, stirrer glass, iron
clamp, slide warmer, balance, rotary microtome,
microscope, glass slide, cover glass, and camera. The
organ was sacrificed and fixed with bouin’s solution.
Decalcifying tissue were done with decal solution for
histological process. Histological slides were made
using paraffin method with Hematoxylin-Eosin (HE)
staining.
RESULTS AND DISCUSSION
Figure 1. Histology of head part of Betta sp. (G) Gill; (Lb) Labyrinth;
(psd) Pseudobranch; (Bc) Buccal cavity. HE staining. (4x10
Magnification).
Fish living in an environment that is considerably
different from that encountered by terrestrial
vertebrates. Compared with air, water is 800 times
more dense, 60 times more viscous, has 1/30 the
capacity to hold oxygen and oxygen diffuses at 1/8000
the rate. Thus this respiratory medium is more abrasive
and oxygen depleted than air (Gary, 2000).
Most teleosts use gills as the main respiratory
surface, although accessory respiratory structures also
occur (Genten et al., 2009). The result showed that the
histology of respiratory organ of fathead Betta sp. is
consist of gill, labyrinth, and pseudobranch. In the
aquatic environment, fish gills serve multiple functions,
such as gas exchange, ionic regulation, acid-base
balance, and nitrogen excretion, for the purpose of
maintaining homeostasis (Perry, 1998; Evans et al.,
2005).
The fish gill has become a multifunctional organ
designed to deal with the vagaries of an aquatic
medium. The gill is not only the primary site for
respiration, it is also the principal, and often exclusive,
site for osmoregulation, acid-base balance, and
metabolism of circulating hormones and perhaps
xenobiotics (Maetz, 1971; Hughes and Morgan, 1973;
Heisler, 1984; Payan et al., 1984). The anatomy of gill
tissue and its vasculature is as diverse and specialized
as the function it performs and the gill might be the
most highly differentiated of any vertebrate organ
(Gary, 2000).
Figure 2. Histology of fathead of Betta sp. (Sm) Striated muscle; (T)
Teeth; (Psd) Pseudobranch; (G) Gill; (Bc) Buccal cavity. HE staining.
(10x10 Magnification).
Teleost fish have eight-gill arches arranged in four
pairs on either side of the buccal cavity. An additional
primordial gill hemiarch, the pseudobranch, is also
present in most species, notable exceptions are the
catfish. Structurally, the pseudobranch resembles a
vestigial gill arch (Laurent and Dunel-Erb, 1984). It
contains filaments similar to those on other gill arches,
but they are generally covered by a relatively thick
epithelium that prevents direct communication with the
environment. Furthermore, the vascular supply to the
pseudobranch is derived from the post-branchial
(systemic) circulation (Gary, 2000).
Figure 3. Histology of gill of Betta sp. (Ga) Gill arch; (Gf) Gill
fillament; (GL) Gill lamellae; (HM) Hypaxial muscle; (Bc) Buccal
cavity; (Ty) Thymus; (Opr) Operculum. HE staining. (10x10
Magnification).

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Nurul Safitri Apriliani, et.al. – Histological Study of Respiratory Organ of Betta sp
Most fish (teleost) have four pairs of gill arches
extending from the floor to the roof of the buccal
cavity. Each of the four pairs is supported by a
cartilaginous and/or bony skeleton facilitating
movement of gills to favorable respiratory positions.
The gills are covered and protected by an operculum
(Genten et al., 2009).
The four pairs of branchial arches in fish consist of
many filaments and lamellae covered with epithelial
cells. Basal wall, mitochondria-rich cells, mucous cells,
and undifferentiated cells are the four major cell types
in the gill epithelia (Perry, 1997; Evans, 1999). MRCs
are generally distributed in the filaments and inter- and
basal-lamellar regions and are believed to be the site of
ionic extrusion in seawater fish and ionic uptake in
freshwater fish (Perry, 1998; Evans, 1999; Evans et al.,
2005; Hwang and Lee, 2007).
The inner surfaces of the gill arches carry one or
more rows of stiff strainers called gill rakers. They
serve to sort and aggregate particulate food material
and to position larger food items before the food is
passed into the esophagus and then into the stomach or
intestine. The rakers tend to be long, slender, and
tightly packed in planktivorous fishes and particle
feeders (such as anchovies, herrings, alewife and
certain scombrids) (Genten et al., 2009). Each gill raker
is composed of an osseous or cartilaginous lamella
supporting the pharyngeal pluristratified epithelium and
connective tissue.
The purpose of the structures of gill lamellae is to
provide a large surface area that supports respiratory
and excretory functions. The efficiency of exchange,
which in the case of oxygen is roughly 50-80%, is
largely a function of the countercurrent exchange
between blood and water (Genten et al., 2009).
Figure 4. Histology of labyrinth of Betta sp. (mv) Microvilli; (mc)
Mucous cell; (gc) Goblet cell. HE staining. (10x10 Magnification).
The labyrinth organ, a defining characteristic of fish
in the suborder Anabantoidei, is a much-folded
suprabranchial accessory breathing organ. It is formed
by vascularized expansion of the epibranchial bone of
the first-gill arch and used for respiration in the air
(Pinter, 1986). This states is same with Munshi and
Graham that Anabantoidei is aquatic-breathing fishes
and have a labyrinth organ protruding from the first-gill
arch on both sides of the branchial cavity to assist in
gas exchange (Munshi et al., 1986; Graham, 1997).
This organ allows labyrinth fish to
take oxygen directly from the air, instead of taking it
from the water in which they reside through use
of gills. The labyrinth organ helps the inhaled oxygen
to be absorbed into the bloodstream. As a result,
labyrinth fish can survive for a short period of time out
of water, as they can inhale the air around them,
provided they stay moist.
Labyrinth in fishes is not initially functional at
immature individual (or at early life). The development
of the organ is gradual and most labyrinth fish breathe
entirely with their gills and develop the labyrinth
organs later in life (Pinter, 1986).
Figure 5. Histology of Pseudobranch (psd) of Betta sp. (G) Gill; (HM)
Hypaxial muscle; (Opr) Operculum; (Br) Branchiostegal rays. HE
staining. (10x10 Magnification).
The pseudobranch is a red, gill-like structure
derived from the first-gill arch and located on the inner
surface of the operculum. It is composed of gill
lamellae, connective tissue, and blood vessels. The
lamellae consist of pseudobranchial cells on an
underlying basement membrane. This latter is applied
to a network of parallel blood capillaries which can be
supported by thin cartilaginous rods. The pseudobranch
has a direct vascular connection with the choroid of the
eye, which is composed of similar arrays of capillaries
(rete mirabile) alternating with rows of fibroblast-like
cells. The pseudobranch is not present in all teleosts.
Those fish which do not possess such structure (some
Siluridae, Ictaluridae, Notopteridae, Cobitidae,
Anguillidae) invariably also lack a choroid rete.
Although it is considered to have an endocrine and
regulatory function as well as a hyperoxygenation
function for the retinal blood supply, these are still to
be defined in full.
In teleosts, pseudobranch occurs bilaterally along
the interior of the opercula anterior to the first pair of
gill arches. While morphologically similar to the gills,
pseudobranchiae have a single row of filaments and
receive oxygen-rich blood from the first efferent
arteries (and are therefore unlikely to serve a
respiratory function). In Cyprinidae,
including Pimephales promelas, the pseudobranch is

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completely covered by the opercular epithelium.
Lamellae, lacking any contact with the external
medium, are fused to each other forming a "glandular
pseudobranch" (Laurent and Dunel-Erb, 1984). The
epithelium is comprised predominantly of
pseudobranchial cells which are morphologically
similar to chloride cells (but unique to the
pseudobranch). Functions attributed to the
pseudobranch include; larval respiration before
maturation of gill arches, regulation of oxygen to the
eyes, enzyme production for use in the gas bladder,
osmoregulation, and many others. In a review of
pseudobranch morphology and function, Laurent and
Dunel-Erb (1984) found none of these explanations
completely satisfactory, concluding that a likely
function "should be at least partly sensory." These
authors believe the pseudobranch, which is richly
innervated, functions primarily in maintaining blood
pressure.
Other from being assisted with labyrinth organ,
Betta sp. also assisted by pseudobranch organ which
has the same function to support respiration process in
fishes. So the fishes can survive in lack of oxygen
(environment). Pseudobranch only assisted in some
species. In fact, Betta sp. is indeed have this
pseudobranch. In some literature, the explanation about
pseudobranch is still had the different meaning of the
function. Other literature reported that pseudobranch
functions to respiration, but the other explained that
pseudobranch function to take oxygen into blood vessel
to choroid eye.
CONCLUSIONS
Betta sp. as an ornamental fish has a special character,
besides as a fighting fish, it has an ability to live in the
low volume of water. It makes Betta sp. can survive in
low-oxygen environment, as it has an additional
respiratory organ (labyrinth, pseudobranch).
Histologically, labyrinth is consist of connective tissue
and folded epithelium. Pseudobranch according to
some literature function as an additional respiratory.
Functions attributed to the pseudobranch include;
regulation of oxygen to the eyes, enzyme production
for use in the gas bladder, osmoregulation, and many
other.
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