Anatomical Variation in the Olfactory Apparatus of Marine Teleosts

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Anatomical variation in the olfactory apparatus of marine teleosts

Keywords: Olfactory, Rosette, Scombridae, Carangidae, Platycephalidae, etc.

ABSTRACT: The olfactory apparatus of marine teleosts viz., Rastrelliger kanagurta, Scomberoides commersonianus and Platycephalus scaber belonging to the family of Scombridae, Carangidae and Platycephalidae respectively has been fixed in 10% formaldehyde solution for 24 h and anatomically examined under light microscope (LM). Anatomical variation regarding the nostrils, olfactory rosette, occurrence of accessory nasal sacs, olfactory lobes, length of the olfactory nerve tracts, etc. are observed. These morphological variations may denote species specific and may decisive for several biological functions.

742-748 | JRB | 2013 | Vol 3 | No 1

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Authors:

Biswas S1, Datta NC2,

Sarkar SK1 and De SK1.

Institution:

1. Department of Zoology,

Vidyasagar University,

Midnapore (West) - 721102,

West Bengal, India.

2. 110/20 B. T. Road,

Kolkata - 700108, West

Bengal, India.

Corresponding author:

Subrata Kumar De.

Email:

[email protected]

Phone No:

+91 03222 275329

Web Address: http://www.jresearchbiology.com/

documents/RA0304pdf.

Dates: Received: 08 Nov 2012 Accepted: 20 Nov 2012 Published: 09 Jan 2013

Article Citation: Biswas S, Datta NC, Sarkar SK and De SK. Anatomical variation in the olfactory apparatus of marine teleosts. Journal of Research in Biology (2013) 3(1): 742-748

Journal of Research in Biology An International Open Access Research Journal

Original Research

INTRODUCTION

Olfaction is an important type of chemoreception

which is mediated through well developed, complex and

organized olfactory system in vertebrates (Freitag et al.,

1999). This system generally develops from the

specialized tissue, called olfactory placode (von Kupffer,

1894). In the early stage of development, placodes are

formed from the preplacodal ectoderm of the anterior

region of the embryo, medial to epidermis and lateral to

both neural crest and neural plate (Knouff, 1935).

The developmental process leading to the formation of

fish olfactory organ, is little diverse (Hansen and

Zielinski, 2005). The peripheral olfactory organ is the

first chemosensory organ to develop in fish preceding the

systems of solitary chemosensory cells (Kotrschal et al.,

1997) and taste (Hansen et al., 2003). Fish generally

possesses a paired olfactory organ located at the anterior

part of the head (Derivot, 1984; Hansen and Zeiske,

1998; Døving, 2003; De and Sarkar, 2009). The olfactory

chambers, olfactory rosette, accessory nasal sacs,

olfactory bulbs, olfactory nerve tracts and brain are the

major components of fish olfactory apparatus

(Hamdani and Døving, 2007). The anatomy of the

olfactory apparatus shows wide range of structural

diversity regarding the shape and size of the olfactory

rosette, number of the olfactory lamellae, occurrence of

accessory nasal sacs, etc. among the teleostean groups

(Kleerekoper, 1969). The anatomical details of the

olfactory apparatus in several species belonging to the

diverse teleostean taxa with respect to their habitat are

still an obscure part in sensory biology. The sensory

systems of fishes show notable adaptations according to

habitat and mode of life in comparison with the higher

vertebrates (Bone and Moore, 2008). The present study

focused on the true anatomy of the olfactory apparatus in

three species of different ecological habitat viz.,

Rastrelliger kanagurta (Cuvier, 1816), a marine

oceanodromous fish; Scomberoides commersonianus

(Lacepede, 1801), a brackish water amphidromous fish

and Platycephalus scaber (Linnaeus, 1758), an estuarine

amphidromous fish to unfold their structural components

and functional significance in olfaction.

MATERIALS AND METHODS

Adult, sex-independent specimens of

R. kanagurta, S. commersonianus and P. scaber were

collected from the coastal regions of Bengal, India.

Specimens were preserved in 10% formaldehyde

solution for 24 h and brought to the laboratory. The

olfactory apparatus of these species were dissected out

and separately mount on grease free slide by using

glycerine. The olfactory apparatus of respective species

was examined under light microscope (LM).

RESULTS

R. kanagurta (Figure 1A) possesses two pairs of

nostril viz., anterior nostril and posterior nostril

(Figure 1B). The anterior nostril is an oval shaped

structure, encircled by a thick lip like ridge of skin and

located at the dorsal region of the snout where as the

posterior nostril is situated in front of the eye.

R. kanagurta shows a slit like structure i.e., posterior

nostril which is located at a moderate distance from the

anterior one (Figure 1B). The olfactory apparatus of the

said species is present at the antero-dorsal side of the

snout in between the anterior and posterior nostril

(Figure 1C). The multilamellar olfactory rosette is oval

in shape and is situated at the floor of the olfactory

chamber (Figures 1D and 1E). The triangular olfactory

lamellae vary from 60 to 70 in number per rosette and

are arranged pinnately on the raphe (Figure 1E). The

accessory nasal sacs are clearly marked in the olfactory

apparatus of R. kanagurta. The lacrimal sac is conical in

shape and located at the antero-medial region of

lachrymal bone in association with olfactory rosette

(Figures 1C and 1D). The ethmoidal sac is connected at

the posterior part of the olfactory rosette and situated

within a groove at the antero-lateral extension of the

Biswas et al., 2013

743 Journal of Research in Biology (2013) 3(1): 742-748

frontal bone (Figures 1C and 1D). The olfactory nerve

tracts are arised from the base of olfactory rosette and the

length varies from 16 mm to 18 mm respectively. The

distal part of the olfactory nerve tracts are connected

with olfactory lobes of the brain. The size of the

olfactory lobes is comparatively small in R. kanagurta

(Figure 1C).

In S. commersonianus (Figure 2A), the nostrils

are closely associated. The anterior nostril is an oval

shaped aperture and partly guarded by a nasal flap where

as the posterior nostril is crescentric in shape

(Figure 2B). The olfactory rosette is circular in shape and

consisting of two pairs of olfactory lamellae

(Figures 2C and 2D). The number of the olfactory

lamellae ranges from 100 to 140 per rosette (Figure 2D).

The accessory nasal sacs are not distinct in the olfactory

apparatus. The olfactory nerve tracts are arised from the

base of the olfactory rosette and the length is ranges from

10 mm to 12 mm. The olfactory lobe is comparatively

large in size (Figure 2C).

Interestingly, the nostrils of P. scaber

(Figure 3A) are situated at the antero-dorsal region to the

Biswas et al., 2013

Journal of Research in Biology (2013) 3(1): 742-748 744

Figure 1A - Schematic representation of Rastrelliger kanagurta.

Figure1B - The diagram shows oval shaped anterior nostril and transverse slit like posterior nostrils of

R. kanagurta.

Figure 1C - The olfactory apparatus of R. kanagurta shows olfactory rosette (OLR), lacrimal sac (LS),

ethmoidal sac (ES), olfactory nerve (OLN), olfactory lobe (OL), cerebral hemisphere (CHS),

optic lobe (OPL), cerebellum (CBL), medulla oblongata (MO), etc.

Figure 1D - The olfactory rosette (OLR) along with conical accessory nasal sacs viz., lacrimal sac (LS) and

ethmoidal sac (ETS).

Figure 1E - The dorsal view of oval shaped olfactory rosette shows central raphe (r), two rows of

lamella (l). The olfactory lamella is triangular in shape with prominent dorsal end (de), proximal end (pe)

and ventral margin (vm).

Plate - 1

OLR

LS

ETS

eye and lying far apart from each other. The anterior

nostril is oval in shape and has a tongue like nasal flap

where as the posterior nostril is valvular (Figure 3B).

The olfactory rosette is relatively large in size and oval

in shape (Figures 3C and 3D). The number of the

olfactory lamellae varies from 50 to 76 in number per

rosette (Figure 3D). The absence of accessory nasal sacs

is noted in the olfactory apparatus of P. scaber. The

length of the olfactory nerve tracts ranges from

22 mm - 24 mm. and it is well connected with the

olfactory lobe of the brain (Figure 3C).

DISCUSSION

Olfactory systems of fish are among the most

highly developed olfactory senses of vertebrates

(Kleerekoper, 1969). The sense of olfaction is mediated

through olfactory apparatus associated with nostrils. The

nostrils are responsible for incurrent and excurrent of

water during water ventilation (Nevitt, 1991). The

structure of the anterior and posterior nostril varies

among the teleostean fishes (Kapoor and Ojha, 1972).

The presence of nasal flaps in between the both nostrils

is almost common when they are closely associated

(Teichmann, 1954). The anterior and posterior nostril

probably acts as an avenue for water ventilation through

the olfactory rosette (Cox, 2008). The multilamellar

Biswas et al., 2013


Figure 2A - Schematic representation of Scomberoides commersonianus.

Figure 2B - The diagram shows anterior and posterior nostrils of S. commersonianus. Nasal flap (FL) is

distinct.

Figure 2C - The olfactory apparatus of S. commersonianus is comprises of olfactory rosette (OLR),

olfactory nerve (OLN), olfactory lobe (OL), cerebral hemisphere (CHS), optic lobe (OPL),

cerebellum (CBL), medulla oblongata (MO), etc.

Figure 2D - The circular olfactory rosette shows central raphe (r), two rows of lamella (l). The olfactory

lamella is large, triangular in shape with prominent dorsal margin (dm), dorsal end (de),

ventral margin (vm) and lingual process (lp).

Plate - 2

olfactory rosette perhaps adopt several type of

arrangement pattern (Holl, 1965). This lamellar

arrangement may help in the particular sensitivity to

certain components like amino acids, steroids,

prostaglandins, etc. (Theisen et al., 1991). Anatomically

the lamellar surface in S. commersonianus is much closer

due to the short distance between anterior and posterior

nostril than R. kanagurta and P. scaber. Therefore, the

water soluble odorants may travel short distance to

interact with comparatively greater olfactory lamellar

surface of S. commersonianus. The water ventilation is

assisted by the pumping mechanism of accessory nasal

sacs (Theisen et al., 1991) and may provide the ability

to sniff (Nevitt, 1991; Cox, 2008). R. kanagurta

possesses well developed accessory nasal sacs but

S. commersonianus and P. scaber has no accessory nasal

sacs. The movement of jaws and its associated muscles

are also very significant for the water ventilation

(Nevitt, 1991). Accessory nasal sacs may be found in the

olfactory organs of fishes with widely variable life styles

and habitats, both marine and fresh water which are not

confined to one particular situation (Cox, 2008).

The olfactory nerve may convey the chemical cues

during water ventilation to the brain (Hamdani and

Døving, 2007). The olfactory information plays an

important role in different behaviour of fish such as

Biswas et al., 2013


Plate - 3

Figure 3A - Schematic representation of Platycephalus scaber.

Figure 3B - The diagram shows anterior and posterior nostrils of P. scaber situated at a distance from each

other. Long nasal flap (FL) is also marked.

Figure 3C - The olfactory apparatus of P. scaber is comprised of olfactory rosette (OLR), olfactory nerve

(OLN), olfactory lobe (OL), cerebral hemisphere (CHS), optic lobe (OPL), cerebellum (CBL), medulla

oblongata (MO), etc.

Figure 3D - The circular olfactory rosette indicates central raphe (r) and two rows of lamella (l).

The olfactory lamella is triangular in shape with prominent dorsal margin (dm), dorsal end (de) and

proximal end (pe).

searching of foods, avoidance of predators,

discrimination between individuals of the same and

different, parental care, orientation in migration, etc.

(Hara, 1971). The olfactory system of teleosts is highly a

specialized structure for the recognition of various water

soluble chemical cues, so this may serve as a biological

model to monitor environmental health as well

as specific meagerness of the pollutants. The

xenotoxification of ocean especially the acidification

may also impair the ability of olfactory discrimination of

coastal and marine species (Munday et al., 2009). Thus,

it is necessary to examine the effect of specific toxic

agent at a subcellular level of olfactory structures in

marine teleolsts.

CONCLUSION

This comparative anatomical study on the

olfactory apparatus along with brain in three different

marine teleost belonging to the diverse ecological habitat

shows much structural variation according to the

changing environment which may be significant for

ecomorphology and evolutionary aspects of

neurobiology (Kotrschal et al., 1998). However, the

olfactory system of marine, estuarine and coastal or

migratory species may experience rapid fluctuations of

environmental inorganic ions (Hubbard et al., 2000), so

it could be an interesting part to identify the cellular

components that are involved in the ion regulation of the

olfactory apparatus in these migratory teleosts.

ACKNOWLEDGEMENTS

Authors are thankful to the Head, Department of

Zoology, Vidyasagar University, West Bengal, for

providing the necessary laboratory facilities.

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Anatomical Variation in the Olfactory Apparatus of Marine Teleosts