Download THE ONCHIDIUM (GASTROPODA: PULMONATA: ONCHIDIIDAE

International Journal of Zoology
and Research (IJZR)
ISSN 2278-8816
Vol. 3, Issue 4, Oct 2013, 23-30
© TJPRC Pvt. Ltd.
THE ONCHIDIUM (GASTROPODA: PULMONATA: ONCHIDIIDAE: GENUS:
ONCHIDIUM) OF THE URAN, WEST COAST OF INDIA
PRADNYA PATIL & B. G. KULKARNI
Department of Zoology, Institute of Science, Mumbai, Maharashtra, India
ABSTRACT
In India, Maharashtra state has a coastline of 720 km having all types of shores. Most of the available Reports are
on macrobenthos diversity on coast of Maharashtra. It is mainly focused on diversity of mollusc like gastropod and
pelecypoda. However, meagre data is available on diversity of Pulmonata gastropod on coast of Maharashtra. Due to such
encroachment and reclamation, a species displacement has been reported on coast of Konkan. In recent years urbanization
and industrialization in coastal belt of Konkan has resulted into modifications of topography of these areas. Present work
on assessing diversity of Onchidium species on coast of Uran has been recorded three species of Onchidium.
O. verruculatum, O. peronii, Platevindex species. The present investigation is the first report on diversity of Onchidium
species on the coast of Uran.
KEYWORDS: Diversity, O. verruculatum, O. peronii, Platevindex species
INTRODUCTION
Census of Marine Life (www.coml.org) programme proved that oceans have great diversity of life. 33 out of 34
major phyla are represented in the ocean, whereas only 15 phyla’s are presented on the land. Census of Marine Life also
proved that every niche in marine ecosystem is occupied by the life. Although every oceanic country has participated in an
international project of Census of Marine Life, a little attention has been paid on coast of India to measure the diversity of
marine life. The Census of Marine Life established a baseline of marine life diversity, distribution, and abundance against
which future change can be measured. Census of Marine Life aggregated more than 30 million of species; including 1,200
newly discovered and described species. Another 5,000 or more await formal description. Census of Marine Life created
the Ocean Biogeographic Information System, the world’s largest online repository of geo-referenced data that nations can
use to develop national and regional assessments and to meet their obligations to the Convention on Biological Diversity
and other international commitments. Census of Marine Life collaborated with the Encyclopaedia of Life to complete
~ 90,000 marine species pages and provided and continues to serve as the marine component of the Global Biodiversity
Information Facility. Census of Marine Life supported the World Register of Marine Species, which confirmed that
excluding microbes approximately 250,000 valid marine species have been formally described in the scientific literature,
with an estimated at least 750,000 more species remaining to be described.
NaGISA (http://nagisa.cbm.usb.ve) the program for assessing diversity of near shore has executed many projects
to assess diversity of intertidal zones. Reports of near shore diversity are available on webpage of NaGISA. Maharashtra
has a coastline of 720 km having all types of shores. Reports are available on macrobenthos diversity on coast of
Maharashtra. Among these reports of Parulekar et.al (1976), Parulekar (1981) Ingole et. al. (2002, 2009), Chhapgar (1958)
Zingde (1999) Jaiswar and Kulkarni (2000), Shahnawaz et.al. (2006), Jaiswar et.al. (2007), Datta et.al. (2010), Balli et.al.
(2011) are worth to mention here. Most of the available reports pertains to diversity of macrobenthos on coast of
Maharashtra mainly focus on diversity of mollusc like gastropod and pelecypoda. However, meagre data is available on
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Pradnya Patil & B. G. Kulkarni
diversity of Pulmonata gastropod on coast of Maharashtra. (Awati and karandikar, 1948; Gopinadha et.al., 1980; Datta
et.al., 2008). In recent years urbanization and industrialization in coastal belt of Konkan has resulted into modifications of
topography of these areas. Due to such encroachment and reclamation a species displacement has been reported on coast of
Konkan. (Khade and Mane 2012a,2012b,2012c).Therefore, present work on assessing diversity of Onchidium species on
coast of Uran has been undertaken, to create a data base with respect to present circumstances of human settlement on
coast of Uran.
MATERIAL AND METHODS
The selected sites were visited during low tide for collection of the Onchidium species. The animals collected
manually from respective sites were washed with sea water and brought to the laboratory for taxonomical studies. The
morphological characters of Onchidium are extremely variable within the populations, and therefore the diagnoses and
identification keys are based on type specimens when available. The identification of Onchidium species was done as per
reports of Fretter (1943); Awati and Karandikar (1948) and Dayrat (2009). The dorsal eyes morphology is used by many
authors to distinguish between species. Table 1 shows the mainly characters used in the keys.
Species Diversity
Topography of Selected Sites
A Preliminary survey of Uran coast was carried out to locate niche of Onchidium species. It has been noticed that
usually marshy areas in mangrove zones are habituated by Onchidium species. Furthermore, population of Onchidium
species was also recorded at rocky shore covered with mud near, marshy areas of mangroves. After thorough survey of
Uran coast Site-I named as Pirwadi beach and Site - II called as Dookar khadi were selected for collection of Onchidium
species
Site-I Uran Pirwadi
Geographically, Uran city (Latitude 180 50’ 20” N and Longitude 720 57’ 5” E) is located on the coast of Arabian
Sea along the eastern shore of Mumbai harbour opposite to Colaba. Total length of Uran coast is approximately 16 km and
it is marked by rocky, muddy and sandy substratum. Most of the coast is rocky towards the sea side and Marshy towards
upper middle zone. Pirwadi site located 7 km away from Uran city. The moderate cover of mangrove exists at Pirwadi Site.
Site II: Uran Dookar khadi
Dookar creek of Uran city opens on one side into the sea near Bori is located at (Latitude: 18° 48' 20" N
Longitude: 72° 59' 33" E). A dense cover of mangrove trees (Avicennia marina) is present in most of the creek. Presence of
loamy mud substratum is one of the favourable factors for habitat of Onchidium species in this creek. Since the creek is in
proximity of Uran city, it is used as dumping ground and therefore heaps of garbage is frequently seen on shore of the
creek.
During present survey three species of Onchidium were collected from both the sites during low tide. Among the
three species Onchidium verruculatum was abundantly found at Site I where most of the area is marshy and of loamy
substratum. During collection the animals were observed to creep on the substratum exposed to the atmosphere. Creeping
trail of O. verruculatum was followed to locate the species. At the time of high tide it was observed that animals were
hiding themselves in crevices of the rocks present on the shore. However, two animals of O. verruculatum found to follow
each other in a straight line during copulation. Further, more than two animals were found in group showing courtship
behaviour Juveniles of O. verruculatum found to hide in burrows of the fiddler crab. Although Onchidium peronii was
The Onchidium (Gastropoda: Pulmonata: Onchidiidae: Genus: Onchidium) of the Uran, West Coast of India
25
available at both the Sites, the percentage of availability of O. peronii was maximum at Site II where mangroves
(Avicennia marina) are abundant. It was observed that O. peronii camouflage with the substratum present near the
mangroves. A group consist of 7-8 O. peronii was observed near the mangroves. The density of O. peronii was recorded
right from upper part of intertidal zone to the lower part of intertidal zone. Platevindex species was collected from both the
sites. However, at site I higher density of Platevindex species was observed than that at Site II. Platevindex species was
also observed to live in a group of 5-6 animals. Since dorsal eyes are absent in Platevindex species it is not prominently
seen against the background of substratum. Therefore, this species is to be collected after careful observation. It has been
noticed that during dusk time Platevindex species density was higher at Site I.
RESULTS
Three species of Onchidium mainly collected from different sites were brought to the laboratory for
morphological studies. Onchidium species were maintained under laboratory conditions in aquaria with sufficient sea water
(25cm×25cmX25cm). External morphological characters were observed in fresh as well as in preserved specimens. The
basic plan of morphological characters is found to be uniform in all three species of Onchidium. However, variations in
certain morphological characters were noticed in all three species of Onchidium.
The basic plan of morphology includes presence of mantle on the dorsal surface. The mantle is thickly covered
with tubercles or body warts. These tubercles are in wide variety of form, size and structure ranging from minute granules
to large protuberances scattered all over the dorsal surface. It has been noticed that tubercles located at posterior side of the
mantle are irregularly branched and have in general a bushy appearance which are commonly known as ‘Gill trees’.
Whereas, unbranched types of tubercles are flattened at their free end on which the mantle eyes are situated. Therefore,
these tubercles are also called as ‘ocular papillae’. These mantle eyes either located singly or in groups consisting of two or
more on each ocular tubercle. The largest ocular group observed to contain six eye spots. However, three to four eye
groups were commonly observed. The fleshy elongated foot present on the ventral side of the body. The foot is surrounded
by all the sides by peripheral extension of the mantle known as hyponotum. The hyponotum is distinguished as per its
location into the right, left, front, and the hind hyponotum regions. The mouth is situated ventrally at anterior end of body
between foot and front hyponotum. The mouth is surrounded laterally by fleshy lobes called as labial palp which are also
known as oral lappets or oral lobes. A pair of conical retractile tentacles carrying cephalic eyes at the tips is present in the
antero-lateral corners of the labial palp. The male genital opening of the slug is located on right side between tentacle and
labial palp. Between the foot and hyponotum three apertures are situated at the hind end of ventral side of the body. Out of
these three, one aperture called as anus is placed in the median line and the female genital aperture lies right of the anal
opening continuous to peripodial groove, the third aperture which is as large slit is located posterior to the anus and it leads
the pulmonary chamber of the slug.
Colour: In live condition general body colour is brown to that of mud colour where animal lives. The ventral
surface is light yellowish grey, whereas foot sole is more yellowish.
Skin: Skin of Onchidium species is generally thick muscular with dorsal tubercles scattered all over of it as
mentioned in morphology characteristics. When skin layer was observed under the compound microscope it shows
presence of various types of pores In Onchidium verruculatum two types of pores are seen. A pore through which dorsal
eye protrude is wide with conical opening, whereas other pores are long and cylinder with the triangular opening. Similar
types of pores are also seen on the skin of Onchidium peronii. However, these pores are oval in shapes and other pores
26
Pradnya Patil & B. G. Kulkarni
have narrow opening. In Platevindex species all over the skin dark black circular shaped spots are present with narrow
openings.
Internal Anatomy: When species of Onchidium dissected out to observe the body organ arrangement, it shows
that viscera are located in specious body cavity. The reproductive organs consisting male and female genital organs are
also seen in the body cavity.
CONCLUSIONS
Position of various organs in three species of Onchidium is given in (Table 2)
Radula: One of the distinctive features of Onchidium species is presence of radula in the buccal mass as of other
gastropods After dissecting out the radula it is clearly noticed that the radula varies with respect to structure, size and shape
in all three species of Onchidium. In case of Onchidium verruculatum center of radula is pointed, anterior sides are
semicircular and posterior sides are curved. In case of Onchidium peronii centre of radula is pointed, anterior sides are
slanting downwards and posterior sides are conical. In Platevindex species radula is acutely pointed, anterior side are
markedly slope downward and posterior sides are cuboidal. The radular teeth of O. verruculatum are large than that of
O. peronii and Platevindex species. In O. verruculatum distinct central rachis of radula is observed whereas in case of
O. peronii and Platevindex species central rachis is not visible. The arrangement of radular teeth is compact in case of
O. peronii
Onchidiids have a worldwide distribution, with the exception of the Arctic and Antarctic (Hoffmann 1928, 1929).
Most species are marine and live in the upper intertidal zone, either in rocky, sandy, or muddy habitats, including
mangroves. However, two species live in brackish habitats and tolerate fresh water: Onchidium typhae (Buchannan, 1800),
and Labella ajuthiae (Labbé, 1935). Three terrestrial species have also been described from high-elevation rainforests:
Semperella montana (Plate, 1893), from Sibugan Island, Philippines; Platevindex ponsonbyi (Collinge, 1901), from
Borneo; and Platevindex apoikistes (Tillier, 1983), from Mindoro, Philippines. Although Onchidium species are reported
widely, Onchidiidae is a poorly known taxon in many regards. Systematics of Onchidiidae has been revised by many
investigators. Anatomical studies of Onchidiids are also not reported adequately. Most of the literature on Onchidiids was
published before 1940’s. Few studies have been published since then (e.g Fretter 1943, Awati and karandikar 1948, Marcus
1978, 1979, Tiller 1983, Britton 1984, Hyman 1990, Weiss Wagele 1998, Dayrat 2009) who have reviewed systematics of
Onchididiiae with a checklist of nominal species. A checklist of all 143 species names available in Onchididiiae is a first
step towards systematic revision. As per this checklist and revision on Onchididiiae species, three species as Onchidium
verruculatum, Onchidium peronii and Platevindex species are reported.
World Register of Marine Species has described 143 species of Onchidium. Which includes Onchidium
verruculatum, Onchidium peronii and Platevindex species. Among the three species recorded at Uran coast Platevindex
species had been reported as Oncis plate (Baker 1938). Further, according the WoRMS, Platevindex species is given as
revised nomenclature for Onchidium martensi and Oncis Plate. Onchidium peronii Cuvier (1804) has also been given by
WoRMS (2010). Five synonyms are reported for Onchidium peronii as per catalogue of life and Peronia peronii is given
as accepted name. However, as per the catalogue of WoRMS (2010) Onchidium peronii has been given as correct
nomenclature. Therefore, during present investigation Onchidium peronii has been accepted nomenclature. However, in
literature on Onchidium species published recently nomenclature like Onchidium verruculatum is widely used. Therefore,
during present investigation same nomenclature has been given after studying thorough morphological characters and
comparison to data with available literature of Onchidium species. Similarly by studying morphological characters of all
27
The Onchidium (Gastropoda: Pulmonata: Onchidiidae: Genus: Onchidium) of the Uran, West Coast of India
the three species of Onchidium and comparing with available literature the identification of three species namely
Onchidium verruculatum, Onchidium peronii and Platevindex species is confirmed.
Diversity of Onchidium species on coast of oceanic countries has been well documented (Kenny and Smith, 1987;
Wu Xu -Feng et.al., 2010; WU Wen-Jian, 2010; Josephine, 2007; Tiller, 1983; Dayrat et.al., 2010a; 2010b; 2011).
However, barring few reports sufficient data is not available on distribution of Onchidium species from West and East
coast of India. (Naik et.al., 1990; Dey, 2006; Saravanakumar et.al. 2007; Mitra, 2008) and only few authors have reported
presence of Onchidium species on coast of Maharashtra (Awati and Karandikar 1948). Awati and karandikar (1948) has
reported three species of Onchidium which include Onchidium verruculatum, Onchidium simorthi, and Onchidium
martensi in several areas of island shore in and around Bombay.Of these O. verruculatum was found to inhabit rocky
places along the shore in nook and corners and under stone areas absolutely devoid of any species of so called mud
skippers. The other two species were invariably found in muddy places which were also rich in mud skipper population. In
present investigation also three species of Onchidium are collected from rocky and muddy shore of Uran coast. The present
investigation is the first report on diversity of Onchidium species on the coast of Uran.
Table 1: Comparison of Morphological Characters in Onchidium species of Uran Coast (West Coast of India)
Sr. No.
1.
Characters
Size
Onchidium verruculatum
≤ 70 mm
Oval and slightly dorsoventrally flattened.
Brown
6-7 black spot located on
each dorsal eye which are
circularly arranged.
Short and conical. Fully
retractable into the head.
Lobes of labial palp are
broad &. sensory lappets
present on each lobe
Onchidium peronii
≤ 20 mm
Oval and elongated
Platevindex species
≤ 40 mm
Oval with circular
dorsal hyponotum
Dark Black
2.
Shape
3.
Colour
4.
Dorsal eyes
5.
Tentacular
eyes
6.
Labial palp
7.
Pulmonary
aperture
Wide pulmonary aperture
extendible up to 5 mm.
Pulmonary aperture
extendible less than 1 mm.
8.
Pedal sole/
foot
Muscular large foot
smaller than hyponotum.
Muscular fleshy foot broader
than hyponotum.
9.
Ventral side
Yellowish grey
Greenish with mottled yellow
margin.
white
10.
Creeping
behaviour
Creeping marks distinctly
seen.
No creeping mark seen
No creeping mark seen
Drab grey
4-5 black spot located on each
dorsal eye which are unevenly
located on the entire body.
Short and conical. Fully
retractable into the head.
Lobes of labial palp are fused
and small.
Dorsal eyes are absent.
Long and slender. Fully
retractable into the head.
Notch present in
between lobes of labial
palp.
Prominent but small
pulmonary aperture
extendible up to 3 mm.
Narrow slender foot
smaller than
hyponotum.
Table 2: Observations on Visceral Organ of Onchidium species
Sr. No.
1.
2.
3.
Visceral Organ
Colour of Hepatopancreas
Heart
Colour of albumen gland
Onchidium verruculatum
Dark brown
Lies under the albumen gland
White
Onchidium peronii
Light yellowish brown
Not easily seen
Pinkish
Platevindex species
Light brown
Clearly observed
Yellowish
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