Indian Journal of Geo Marine Sciences
Vol. 46 (06), June 2017, pp. 1098-1104
Comparative taxonomic evaluation of Thais species (Order:
Gastropoda; Family: Muricidae) of Mollusca from Maharashtra coast of
India
Ravi Kumar1, A.K. Jaiswar1, S. Jahageerdar1, S.K. Chakraborty1, A. Pavan Kumar1 & Laxmi Prasad2
1
Central Institute of Fisheries Education (ICAR), Mumbai, Maharashtra - 400061, India
Narendra Dev University of Agriculture & Technology, Kumarganj, Faizabad, U.P. -224229, India
2
[Email- akjaiswar@cife.edu.in]
Received 17 December 2014 ; revised 15 November 2016
Based on shell morphology alone, it was difficult to differentiate the species belonging to genus Thais because of large
amount of plasticity, observed in the shell characters. The colour of the shells was poorly defined as species identifying character
in Thais species. The morphometric and meristic characters of the shell along with radular characters can solve the taxonomic
ambiguities in Thais species (Thais lacera; T. blanfordi; T. tissoti; T. rudolphi; T. bufo and T. subnodulosa). The radular
morphology was found to be different in each species except in T. rudolphi and T. blanfordi and hence these two species were
differentiated based on radular morphology where the first denticle on outer base of the lateral cusp was smaller than other five
denticles in T. rudolphi but in T. blanfordi, all were same in size. A deep ‘V’ shaped notch was present between inner denticle
base of lateral cusp and central cusp in T. blanfordi, which was found to be a species specific character.
[Keywords: Thais, Muricidae, Gastropods, Mollusca, radular]
Introduction
Molluscs have been evolved about 500
million years ago during the Cambrian period1.
Among the classes of Mollusca, Gastropoda is
most diverse group consisting of 80 per cent of all
the molluscs numbering to around 80,000-100,000
species. Appukuttan, reported 3271 species
belonging to 220 families and 591 genera,
including 1900 species of gastropods, 1100
pelecypods, 210 cephalopods, 41 polyplacophores
and 20 scaphopods from India2. Among the
gastropods, muricids shell exhibits highest degree
of variations with regards to shell morphology and
sculptural patterns, which demonstrate its
evolutionary importance3.
Taxonomic studies of the gastropods have
been carried out by researchers using shell
morphology, sculpture, micro-structure, radula
and anatomical characters, operculum structure
and meristic counts. In Thais species the radula
is stenoglossan (rachiglossan) type and usually
has three cusps and smaller denticles. Radular
characters have also been widely used in species
diagnosis4,and, considered as valid indicators
of phylogeny for Thaidid gastropods5. In India
molluscan fishery is contributing significantly in
total marine fishery. They form an important part
of food of coastal population, in preparation of
decorative items and in lime industry, and are
important link in marine food web. However, the
previous studies did not explain in detail
taxonomy for majority of Thaidids, which aid to
differentiate them easily. In view of this, the
present study attempted to describe the
identification of six Thais species occurring along
the Maharashtra coast of India based on shell
morphology and radular structure.
Materials and Methods
For the present study, a total of 177 specimens
belonging to six different species of Thais
comprising of Thais lacera (41); T. blanfordi (50);
T. tissoti (50); T. rudolphi (20); T. bufo (10) and
T. subnodulosa (6) were collected from different
coastal areas, Juhu Kolivada, Bandstand, Aksa
beach, Versova beach, Shrivardhan, Alibaug and
Ratnagiri along the Maharashtra coast of India.
The species were identified by using identification
INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017
keys and publications1, 2-10. A total of seven
morphometric characters, shell length (SL), shell
width (SW), body whorl length (BWL), aperture
length (APL), aperture width (APW), shell weight
(SWT) and animal weight (AWT) were measured
from the collected specimens. Similarly, four
meristic traits like number of whorls (NW),
number of primary spiral cords bearing
nodules/tubercles on body whorl (NPBW),
number of ridges or teeth inside of outer lip of the
aperture (NRL) and number of tubercles in first
spiral row on shoulder of body whorl bearing
nodules/tubercles (NT) were counted. The length
(mm) variables were measured using digital
Vernier callipers and weight (g) with a digital
weighing balance.
Fig 1. (A). T. Lacera (i). six whorls, (ii). two spiral ridges on body
whorl bearing strong triangular tubercles. (B) (i). two grooved sulcus
instead of anal sulcus, (ii). Well developed umbilical chink; (2). T.
rudolphi (C) (i).five whorls, (ii). Five primary spiral cords on body
whorl, (D) (i).primary spiral cords bearing alternate brown and white
nodules; (3). T. subnodulosa (E) (i).six whorls, (ii). A white spiral
strip between third and fourth spiral cords on body whorl (F) (i). four
ridges or teeth inside of outer lip of the aperture; (4). T. tissoti (G)
(i).five whorls, (ii). secondary grooved spiral cords in between of the
each primary spiral cord on body whorl, (H) (i). four primary spiral
cords, (ii). five ridges or teeth inside of outer lip of the aperture; (5).
T. bufo (I) (i).five whorls, (ii).two primary spiral cords bearing blunt
tubercles; (6). T. blanfordi (J) (i).five whorls, (K) (i). ). six ridges or
teeth inside of outer lip of the aperture.
Extraction of radula
Live specimens were anesthetized by injecting
7.5% of MgCl2 to relax, loosen the muscles
attached to the inner shell surface, facilitated easy
1099
removal of animal out of shell without any
damage. In case of any difficulty to draw out the
animal from shell, the shells were kept in deep
freeze at -200C for 24 hours resulting in shrinkage
of muscle part. It is necessary to thaw them for
15-20 minutes in tap water before pulling out
animal from frozen shells. Subsequently the
extracted animals were washed and cleaned
thoroughly; an incision was made on dorsal
surface of the head with the help of scalpel and
scissor, a few millimetres away from the base of
tentacles or mouth opening to expose out radular
sac. The sac was lifted out carefully with the help
of forceps and transferred to 20% NaOH solution.
Later the solution was boiled for 5-8 minutes at
1000C in order to dissolve the attached tissue that
resulted in release of radula into the solution. The
radula was picked up from solution with the help
of forceps and washed in distilled water and
absolute alcohol for 2-3 times to dehydrate and
clean the radula. For further examination, the
radulae were mounted on a clean glass slide with
a drop of glycerine and examined under
compound microscope. The radula was
photographed by fixing the target at maximum
resolution with provided zooming power (10X &
40X) followed by fixing the lens of digital camera
on the eyepiece of compound microscope.
Fig. 2 Characteristics of radula, 1. T. blanfordi, 2.T. bufo, 3.
T. lacera, 4. T. rudolphi, 5. T. subnodulosa and, 6. T. tissoti
cc- central cusp, lc- lateral cusp, idlc- inner
denticle on lateral cusp, mc-marginal cusp, ddenticles between marginal and lateral cusp.
Statistical analysis
PROC MEANS procedure (SAS Institute,
2012) was used to estimate the descriptive
statistics. PROC FREQ procedure was used to
create frequency and cross-tabulation tables for
meristic traits.
1100
KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS
Table.1: Descriptive statistics of the morphometric traits
Statistics
Mean±SE
Minimum
Maximum
Variable T. subnodulosa
T. tissoti
SL
18.25±1.306 18.15±0.400
BWL
12.23±0.745
9.84±0.282
SW
9.27±0.769
11.31±0.189
OPL
10.49±0.637
9.40±0.299
OPW
3.46±0.279
5.12±0.128
SWT
1.78±0.401
1.12±0.088
AWT
0.19±0.030
0.16±0.011
SL
14.23
10.84
BWL
9.92
6.86
SW
6.85
7.14
OPL
8.42
6.31
OPW
2.66
3.67
SWT
0.63
0.21
AWT
0.10
0.06
SL
21.78
26.27
BWL
13.97
14.97
SW
11.41
15.92
APL
12.19
14.75
APW
4.31
7.39
SWT
3.19
3.59
AWT
0.27
0.39
Species
T. lacera
41.82±1.367
29.99±1.043
26.65±1.006
24.97±0.713
11.33±0.364
13.19±1.0458
2.17±0.154
25.55
18.75
17.02
17.19
7.42
2.58
0.87
58.76
41.54
39.68
32.91
15.72
22.43
4.07
T. rudolphi
45.18±3.134
37.08±2.481
28.45±1.752
33.60±2.209
14.09±0.887
13.49±2.035
3.68±0.682
27.14
20.91
17.04
19.49
6.62
2.94
0.59
70.57
53.07
41.58
47.65
20.07
35.92
8.83
T. blanfordi
26.03±0.373
18.22±0.281
15.42±0.207
15.55±0.207
6.76±0.118
3.09±0.125
0.36±0.015
19.11
14.58
12.18
12.75
5.06
1.35
0.14
29.83
21.96
19.05
18.45
8.32
4.59
0.56
T. bufo
38.64±3.893
32.22±3.723
27.16±3.413
29.52±3.417
12.97±1.641
12.71±4.588
3.31±1.620
27.14
20.91
17.04
19.49
6.62
2.94
0.59
60.85
53.89
47.56
47.61
22.49
47.31
15.91
Where, SL (Shell Length), SW (Shell Width), BWL (Body Whorl Length), APL (Aperture Length), APW (Aperture
Width), SWT (Shell Weight) and AWT (Animal Weight)
Table 2. Comparative statement of meristic traits of Thais species
Characters
T.
lacera
5-6
7-11
T.
bufo
5
9-11
T.
tissoti
5
10-14
T.
rudolphi
5
12-13
T.
blanfordi
5-6
9-11
T.
subnodulosa
6
10-12
No. of primary spiral
cords on body whorl
bearing tubercles
2
2 or 4
4
3-5
2-4
4
No. of ridges or teeth
inside of outer lip of the
aperture
0
0
4-5
26-29
4-8
4-5
No. of inner lateral
denticles (radula)
1
1
1
1
1
1
No. of denticles
between lateral and
marginal cusps
5
7
3
6
6
1
Plain grayish
or yellowish
tan, inside of
aperture pale
orange
light
brown
to gray
in
colour
Light
brown,
with
dark
brown
tubercles
and
aperture
whitish
Chocolate
brown with
white spaces
between
beads on the
beaded cords
aperture and
columella
white
Light
brown,
interior
white, dark
blotches on
columella
chocolate
brown with
dark brown
tubercles
No. of whorls
No. of tubercles
in first spiral cord on
shoulder of the body
whorl
Colour
INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017
Results
Based on our present findings six species of
Thais are described below.
T. lacera (Born, 1778) Fig. 1(A & B)
Shell with 5-6 whorls, body whorl largest.
Secondary spiral cords (8-12) present between
first two well developed tuberculated primary
spiral keels on body whorl. Umbilical chink
surrounded by a broad thickened rim. Aperture
ovate, inside of the outer lip smooth and siphonal
canal short. Two grooved sulcus present instead of
anal sulcus, where keeled spiral ridges ended on
outer lip. Colour: Shell surface plain greyish or
yellowish tan, inside of aperture pale orange,
juveniles had darker lines in grooves on inner side
of the outer lips.
The radula with a triangular pointed central
cusp; lateral cusps bear single inner lateral
denticle; edge of the inner lateral denticle
serrated; base of the inner lateral denticle wider,
five denticles present between marginal and
lateral cusps. The length of lateral cusp about half
of the total length of central cusp.
T. rudolphi (Lamarck, 1822) Fig. 1 (C&D)
Shell thick with large body whorl, aperture
more expanded with a short siphonal canal, four
whorls, short conical apex, spiral growth lines
well developed and aperture canaliculated both
the ways. Surface sculptured with spiraled, widely
beaded cords with plain spiral cords between.
Columella almost straight, a longitudinal deep
notch in middle region of anterior portion of
columella is present. 4-5 flat but feebly raised
spiral ridges on the body whorl, alternatively
banded with white and dark brown nodules. Outer
lip thin, inner surface finely grooved in brown and
yellowish line with the outer fine spiral ridges.
Columella and parietal wall heavily calloused and
yellowish in colour but, inner margin of columella
towards aperture dark brown in appearance.
Umbilicus reduced. Colour: Chocolate brown with
white spaces between beads on the beaded cords;
aperture and columella white.
Six denticles present between lateral and
marginal cusps; first denticle on outer base of the
lateral cusp smaller than other five denticles; a
single inner lateral denticle; central cusp straight
and pointed. The base of lateral cusp wider than
central cusp.
T. subnodulosa (Gravely 1942) Fig. 1 (E & F)
Shell slender, spire longer than the body
whorl; aperture opening narrow. The Body whorl
consisted of a white band between the third and
1101
fourth row of tubercles, visible inside of the
aperture. Aperture with four to five denticles, the
posterior two denticles lead to raised ridges inside
the aperture. Spire consists of five angulated
whorls, with two spiral cords of compressed
tubercles on each whorl. Body whorl bears 4-5
spiral chords of compressed round tubercles.
Axial sculpture with 8-9 axial ribs. Denticles 4-5
inside of the outer lip of aperture. Columella with
2-3 anterior plications just above the siphonal
canal; siphonal canal short and narrow; anal
sulcus deep, inverted ‘U’ shaped. Colour: Shell
chocolate brown with dark brown tubercles,
Interior of aperture violet in colour. Columella
with dark brown patch posteriorly, anterior
portion violet in colour.
Central cusp of radula was thin, needle
shaped; 1 or 2 denticles present between lateral
and central cusps; single marginal denticle.
Marginal cusp absent.
T. tissoti (Petit, 1852) Fig.1 (G & H)
Spire elevated, body whorl large and oblong.
Aperture narrowly ovate, outer margin crenulated,
inside of the outer lip with 4-5 ridges, columella
smooth plicated anteriorly, margined posteriorly
by ridge, anal sulcus deep inverted ‘U’ shape. The
sculpture of body whorl consists of 4 thick spiral
ridges with bisulcate grooves and two narrow
cords in between of primary spiral ridges
ornamented with low tubercles, umbilicus small
almost closed; anterior canal short. 10-14
tubercles present in first spiral row on shoulder of
the body whorl. Colour: Light brown with dark
brown tubercles and aperture brownish white in
colour.
Central cusp of radula triangular in shape and
short; single inner denticle; four small pointed
denticles between lateral and marginal cusps.The
lateral cusps extending toward marginal cusp.
Marginal cusp short and blunt.
T. bufo (Lamarck, 1822) Fig.1(I & J)
Shell thick, globose in shape, heavy and solid
with short spire; body whorl largest with blunt
spines. Aperture large and canaliculated on both
anterior and posterior sides; columella broad,
smooth and extended beyond upper extremity of
outer lip. Umbilicus well developed and
surrounded by thick umbilical chink. Aperture,
relatively broader than other thaidid shells. The
body whorl liraeted with fine spiral cords and
spirally grooved structure. Outer lip margin
serrated, alternately marked by white and brown
spots but smooth inside. Body whorl wider, outer
lip thicker, tubercles comparatively well
1102
KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS
developed, widely spaced and less in number than
T. rudolphi. Colour: The shell light brown to gray
in colour. The rachidian cusp of radula sharply
pointed; single inner lateral denticle pointed
upward but slightly bent towards the lateral cusp.
Seven denticles between lateral and marginal
cusps, of which the first two denticles on outer
base of the lateral cusp poorly developed and
blunt (Fig 2).
T. blanfordi (Melvill, 1893) Fig.1 (K & L)
It neither pose bisulcate transverse groove nor
the revolving raised ridges of small nodules
equidistantly on the body whorl, as in T. tissoti.
Spire made up of 4-5 angulated whorls, body
whorls with two spiral rows of compressed
tubercles (9-11 in numbers), and two rows of
indistinct ridges, anal sulcus broad inverted ‘U’
shape margined by ridge. Inside of outer lip with
4-8 strong ridges, generally six, arranged in pairs.
Anterior canal short and broadly open. Colour:
Light brown, interior white, dark blotches on
columella.
A deep ‘V’ shape notch between inner lateral
denticle and central cusp of radula. The central
cusp pointed and slightly curved towards the right
side. Six small pointed denticles between
marginal and lateral cusp.
Descriptive analysis of shell morphometric traits
The mean shell length in the present study
ranged from 45.17±3.13 mm in T. rudolphi to
18.14±0.29 mm in T. tissoti. The overall and
species wise average of various morphometric
traits is presented in Table1.In the present study, it
was observed that the species belonging to the
genus Thais have different radular morphological
characters. The general radular formula for all
Thaidid species was same, having rachiglossan
type of radula consisting of one marginal cusp,
one lateral cusp and one central cusp, but
denticles present between lateral and marginal
cusps differed in each species. The number of
denticles between marginal and lateral cusps was
found to be different in all studied species except
in T. rudolphi and T. blanfordi, however, their
radular morphology was different. The first
denticle on outer base of the lateral cusp was
smaller than other five denticles in T. rudolphi,
but in T. blanfordi all denticles were similar in
size. A deep ‘V’ shaped notch was present
between inner denticle base of lateral cusp and
central cusp in T. blanfordi, which was found to
be a species specific character.
Descriptive statistics of meristic traits
The number of primary spiral cords on body
whorl bearing tubercles in T. tissoti and T.
subnodulosa were similar but, the number of
whorls was different. The number of primary
spiral cords on body whorl bearing tubercles was
2-4, 3-5, 2, 4, 2-4 and 4 in T. blanfordi, T.
rudolphi, T. lacera, T. tissoti, T. bufo and T.
subnodulosa, respectively.
Number of body
whorls in T. tissoti and T. bufo were found to be
similar but different in presence and absence of
ridges inside of the outer lip. They were also
found to differ in number of the tubercles present
on first spiral cord. The tubercles present on
shoulder of the body whorl were 10-14 and 9-11
in T. tissoti and T. bufo, respectively (Table
2).The number of primary spiral cords (4) and
number of ridges inside of the outer lip (4-5) was
tissoti, but difference was seen in having six and
found to be similar in T. subnodulosa and T.five
number of whorls, respectively. T. lacera has
unique meristic character as presence of only two
keeled spiral ridges bearing strong triangular
tubercles and absence of ridges inside of the outer
lip.
The PROC FREQ procedure was applied for
meristic traits analysis revealed that in T.
blanfordi 92% specimens were with 5 numbers of
whorls, while 88% of T. lacerahad6 numbers of
whorls. In, other three species i.e. T. rudolphi, T.
tissoti and T. bufo 100% specimens were with 5
numbers of whorls, while 100% specimens of T.
subnodulosa had six number of whorls (Table 3).
Discussion
Molluscs exhibit complex larval stages, frequent
cryptic taxa and substantial phenotypic plasticity;
all factors hinder morphological approaches to
identify Thais species11, 12. The phenotypic
plasticity in shell morphology which is common
in molluscs poses additional problems for their
proper identification and often leads to erroneous
results creating many synonyms and doubtful
species. In the present study, colour of the shells
of same species was found to be differed along
with their change in habitats. However, the
morphological features used most frequently for
species identification, including size, shape and
the absence or presence of blotches on the nodules
of shell surfaces and apertures etc. were highly
variable depending on the local environment.
INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017
1103
Table.3. Analysis of meristic traits by using PROC FREQ procedure
Species
Frequency of the meristic traits
NO
5
6
2
4
4
6
8
9
NT
10
11
Freq
(92%)
(8%)
(12%)
(88%)
(8%)
(82%)
(10%)
(74%)
(20%)
(6%)
2
NO
Freq
5
(12%)
6
(88%)
3
NO
Freq
5
(100%)
4
NO
Freq
5
(100%)
4
(100%)
5
NO
Freq
5
(100%)
4
(100%)
6
NO
Freq
6
(100%)
4
(100%)
1
NW
NPBW
NRL
2
(100%)
3
(10%)
4
(30%)
0
(100%)
5
(60%)
26
(20%)
27
(10%)
7
(14.6%)
28
(15%)
4
(6%)
29
(55%)
5
(94%)
0
(100%)
4
(50%)
8
(19.5%)
10
(26.8%)
12
(40%)
10
(4%)
10
(83.3%)
11
(24.4%)
13
(60%)
11
(10%)
9
(50%)
5
(50%)
9
(14.6%)
12
(8%)
13
(72%)
10
(30%)
14
(6%)
11
(20%)
12
(16.7%)
SPECIES - 1 (T. blanfordi), 2 (T. lacera), 3 (T. rudolphi), 4 (T. tissoti), 5 (T. bufo) and 6 (T. subnodulosa)
VARIABLES - NW (number of whorls), NPBW (number of primary spiral cords on body whorl), NRL (number of ridges inside of the outer lip) and NT (number of nodules/tubercles in first
spiral row on shoulder).
1104
KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS
The above studied six Thais species were
identified based on the morphological and meristic
traits along with their radular structure. The
identification of Thais species is therefore still
debated particularly on family and subfamily
level. There are few genera under the family
Muricidae i.e. Thais, Thaisella, Mancinella,
Purpura, Drupa, Rapana and Indothais making
muricids difficult to be identified.
3.
4.
5.
6.
Conclusion
The present finding will help in identification
of Thais species. Though they are not important
economically, occupy importance position in food
chain of in intertidal ecology, as food for demersal
fishes. They also help in assessing the
environmental quality and often used as indicator
species for many physicochemical parameters.
Therefore, these organisms should be protected,
conserved and managed for sustainable
management of fishery resources.
Acknowledgement
Authors are grateful to Dr. W.S. Lakra, Director
Central Institute of Fisheries Education for his
encouragement and support during the study.
7.
8.
9.
10.
11.
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