Abstract Biogenic structures of Architectonica laevigata (Gastropod: Architectonicidae) were studied along the lagoon of the Modwa spit area, Mandvi, Gulf of Kachchh. The traces are bilobed in cross-section, forming complex meandering trails, while their burrows are closely packed small holes about 1-2 mm in diameter. The traces are produced during low tides and are concentrated in specific areas within the intertidal zone, and also show substrate preference. These traces and burrows are intimately associated with each other, which reflect their behaviour modification to avoid steep thermal gradients and desiccation stress during low tide conditions in the lagoon and intertidal area. Similar traces are comparable with the ichnogenera Gyrochorte and Scolicia, which are abundant from Precambrian times to recent. Such traces, if preserved, serve as a good indicator for paleo-environmental conditions

Bhawanisingh G Desai

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Open access e-Journal Earth Science India, Vol. 3 (IV), October, 2010, pp. 242-247 
http://www.earthscienceindia.info/; eISSN: 0974 – 8350 
242 
 
Biogenic Sedimentary Structures Produced by 
Architectonica laevigata (Gastropod: Architectonicidae), 
Mandvi Intertidal Zone, Gulf of Kachchh, Western India 
 
 Bhawanisingh G Desai 
School of Petroleum Technology, Pandit Deendayal Petroleum University, 
Raisan Village, Gandhinagar-382009 
Email: bhawanigd@gmail.com 
 
 
Abstract 
 
  Biogenic structures of Architectonica laevigata (Gastropod: Architectonicidae) 
were studied along the lagoon of the Modwa spit area, Mandvi, Gulf of Kachchh. The 
traces are bilobed in cross-section, forming complex meandering trails, while their 
burrows are closely packed small holes about 1-2 mm in diameter. The traces are 
produced during low tides and are concentrated in specific areas within the intertidal 
zone, and also show substrate preference. These traces and burrows are intimately 
associated with each other, which reflect their behaviour modification to avoid steep 
thermal gradients and desiccation stress during low tide conditions in the lagoon and 
intertidal area. Similar traces are comparable with the ichnogenera Gyrochorte and 
Scolicia, which are abundant from Precambrian times to recent. Such traces, if 
preserved, serve as a good indicator for paleo-environmental conditions. 
 
Key Words: Biogenic structures, Gastropod, Architectonicidae, traces, burrows, Gulf of 
Kachchh. 
 
Introduction 
 
The intertidal zone is considered to be a “stressed” area (Vermiji, 1978), and those 
organisms dwelling in this zone are considered to be “stress tolerant species” (sensu stricto 
Vermeij, 1978). The organisms often undergo intense environmental and physiological 
stress, leading to behavioural switching (Faulkes, 2005) and behaviour modification. The 
stress factors include the thermal gradient and desiccation, along with competition. The 
behaviour of any organism is reflected in the biogenic sedimentary structures produced by 
them within the sediment or on surface. Biogenic sedimentary structures are the dominant 
features of modern as well as ancient soft-sediment intertidal environments (Patel and 
Desai, 2009). In the ancient rock record, morphological patterns preserved in the form of 
traces, burrows, and borings are good indicators of the behavioural strategy adopted by 
organisms during changing conditions (Desai, 2003). Biogenic structures made by intertidal 
gastropods are particularly interesting as they give insights into the behaviour of stress-
tolerant species that are adapted to behavioural switching. Some of these structures are 
rarely preserved as they are made at the sediment-water interface and are commonly 
destroyed by erosion.  
 
The soft-sediment intertidal zone of the Mandvi area, Western India (Fig. 1) registers 
varied behavioural activities and their resultant traces produced by the gastropod 
Architectonica laevigata Lamarck, 1816 (Architectonicidae). A. laevigata is a common 
intertidal gastropod of the Gulf of Kachchh (Hornell, 1909; Gopalkrishnan, 1970), having 
broad and conical shells that vary in size from minute to 50 mm or larger, with a varying 
umbilicus width. The protoconch of the Architectonicidae grows upside down, with the 
Biogenic Sedimentary Structures Produced by Architectonica laevigata (Gastropod: Architectonicidae), 
Mandvi Intertidal Zone, Gulf of Kachchh, Western India: Desai 
 
 
umbilicus facing upwards and hence appearing to be coiled sinistrally, although the animal 
is organized dextrally (Bieler, 1993).  
 
A. Laevigata shows a great variety of behavioural adaptation at the sediment-water 
interface, which includes substrate-specific locomotion, dwelling and feeding activities 
(Desai, 2003). Two basic interrelated behavioral activities are studied, namely burrowing 
and locomotion. Both activities are commonly observed in modern environments and are 
governed by stress acting in the intertidal zone during tidal fluctuations. Like other intertidal 
organisms, A. Laevigata takes refuge in and makes locomotion excursions into the surficial 
sediments during low tide.  
Area of Investigation 
 
The Mandvi area (Fig. 1a) has a semi-diurnal tide-affected coastline situated at the 
southernmost tip of the Kachchh Peninsula. The intertidal zone here has a soft substrate 
with sediments ranging from medium sand to fine silt along with different proportions of 
clay and mud. Geomorphologically, there is a dominance of ridge-and-runnel systems (RRS) 
in the area (Patel et al., 2001). The western part of the study area is dominated by RRS, 
giving way to a tidal flat environment towards the east. It also comprises two small 
intertidal lagoons, one situated at Rawal Pir and the other at Modwa. The present study was 
carried out in the Modwa spit lagoon, which is shallow and elongated in nature and 
connected to the open sea towards the southeast. During low tide, it partially drains, leaving 
about 50% of the lagoonal area exposed. The remaining 50% of the lagoon area is 
comprised of thick algal mats. The sediments are fine-grained, with a peat layer 5-7 cm 
below the sediment-water interface. This zone is also inhabited by other benthic organisms 
such as crustaceans, polychaetes, bivalves and nemertea along with the abundant 
gastropod Architectonica laevigata.  
 
Observed Habitat of Architectonica 
 
Architectonica is found in a soft substrate of fine sand in the aerobic environment, 1-
2 mm below the sediment-water interface (Fig.1b). It communicates with the external 
environment through a pair of highly active siphons by which it performs all vital 
physiological activities. It extends a siphon from the aperture upward towards the sediment-
water interface, which creates a definite pattern on the surface. Miller (1974) suggested 
that gastropods living in sandy substrates have diverse locomotion modes and possess a 
long foot, often moving in a discontinuous way with the foot totally or partially buried.  
 
The gastropod communities comprise about 500-600 individuals per m2 area. The life 
position of each individual inside the burrow is with its long axis parallel to the bedding and 
its aperture nearly vertical. It was observed that the animal excavates a tunnel by its 
slender foot in an oblique manner, thus the opening is located on the surface slightly away 
from the shell and linked to the former by a tiny inclined tunnel 5-8 mm in length. Field 
observations during various tides on the Modwa spit suggest that the gastropods do not 
leave the burrow during high tides, unless they are eroded and relocated elsewhere by 
stronger tides. However, during receding tides they do come to the surface and move 
about, thus constructing locomotion traces. Several trails with blunt, burrowed ends were 
observed in the intertidal zone just after the area became exposed during low tide. These 
traces were abundant (up to 25 individuals per m2) and of varied lengths, often crossing 
each other. However, according to the density of individual gastropods, less than 0.05% 
actually produces traces. The production of traces thus seems to be the exception rather 
than the rule. 
Open access e-Journal Earth Science India, Vol. 3 (IV), October, 2010, pp. 242-247 
http://www.earthscienceindia.info/; eISSN: 0974 – 8350 
244 
 
 
 
 
Biogenic Sedimentary Structures Produced by Architectonica laevigata (Gastropod: Architectonicidae), 
Mandvi Intertidal Zone, Gulf of Kachchh, Western India: Desai 
 
 
Fig. 1: (a) Location map of the Mandvi intertidal zone; (b) Architectonica laevigata in life 
position; (c) Burrows of A. Laevigata. Red cap is 15 mm in diameter; (d) V-shaped 
locomotion trace of gastropod during low tide. Arrow indicates raised rim of 
temporary burrows. Coin is 24 mm in diameter; (e) Trace fossil Gyrochorte from the 
Jurassic (Jhuran Formation) of the Jara Dome in Kachchh. Coin is 24 mm in 
diameter; (f) trace fossil, cf Archaeonassa- a bilobed trace from the early Cambrian 
Nigalidhar section of Himalayas.  
 
Morphology of Trails and Burrows 
 
Trails: 
These gastropods produce generally smooth, bilobed trails (Fig. 1d), with a 
prominent V-shaped morphology in cross-section. As they move about on the sediment-
water interface, loose sediments along the lateral margins of the trail collapse outward after 
their passage. The resultant morphology of the trails is shallow (<1 cm), narrow and bilobed 
without any transverse ridges. They show rims of about 3-4 mm thick, with a total width of 
about 16-18 mm, the latter remaining constant throughout the trail. The trails show a low 
order of meandering and are often found criss-crossing each other. The end of each trail is 
marked with a semi-circular, rimmed depression. The substrate preferred for locomotion is 
slightly firm, medium-grained sediments. The depressions in the end of the trail are 
morphologically different from the burrows. These depressions may or may not be 
connected to the actual burrows. The orientation also differs significantly. In case of 
depression, the axis of orientation is coinsides with the trail and is at very small angle with 
respect to substrate. 
 
Burrows: 
 Cylindrical, unlined burrows, with circular cross section, showing surficial expression 
as closely packed small holes of about 1-2 mm diameter are often seen all along the lagoon 
of the Modwa spit area (Fig. 1c). Each hole is associated with a near-vertical, cylindrically 
shaped, straight burrow of nearly 1-3 mm in length. The end of the burrow coincides with 
the aperture of the shell of Architectonica laevigata.  
 
 Locally, the gastropods also make temporary inclined burrows close to the surface at 
the end of the trail, as discussed earlier. The surficial expression of the burrows is in the 
form of elevated semicircular mounds about 1-2 mm high. The substrate preferred for 
burrowing is loose, fine-grained sediments.  
 
Discussions 
 
 The present study describes modern Architectonica laevigata traces formed in a 
lagoon/intertidal setup. From a paleo-ecological point of view, the narrow, V-shaped 
meandering trail, if preserved, would be classified as Repichnia (locomotion traces). 
However, if the burrows were to be preserved, it would resemble small Skolithos.  
 
The surfacial trace made by Architectonica laevigata in the lagoon of the Mandvi 
area, if preserved in the rock record, may be identical to the ichnogenera Gyrochorte or 
Archaeonassa (Fig. 1e, f). Gyrochorte is a common and abundant trace fossil of Mesozoic 
deposits in Kachchh (Patel et al., 2008). These traces, which show a low order of 
meandering and cross-over structures, are frequently observed in the Jurassic Jara Dome 
Open access e-Journal Earth Science India, Vol. 3 (IV), October, 2010, pp. 242-247 
http://www.earthscienceindia.info/; eISSN: 0974 – 8350 
246 
 
(Desai et al., 2008) and can also be interpreted to have formed in an intertidal 
environment. Similarly the ichnogenus Psammichnites, a gastropod locomotion trace, is 
significant in Precambrian deposits of the Himalayas (Tal Group, Mussoorie area). 
Psammichnites, a Palaeozoic trace is also similar to the present form, but is interpreted to 
be constructed by hydraulically operated push-and-pull action of Gastropod (Seilacher, 
2007). Fenton and Fenton (1937) also described similar bilobed trails, Ichnogenus 
Archaeonassa and their associated burrows from the recent sand and compared them with 
Cambrian occurrences of similar forms from British Columbia.   Badve and Bhonsle (1987) 
studied similar burrowing habits of Umbonium in intertidal zones. However, in the case of 
Umbonium the burrows are inclined, whereas Architectonica burrows are nearly vertical. 
  
Several studies have shown that the locomotion of intertidal dwelling gastropods is 
related to rhythmic tidal fluctuations, whereby these gastropods are adapted to rhythmic 
zonal migration synchronised with the tides (Naylor, 1987; Chelazzi et al., 1987).  
  
Architectonica is considered to be among the fastest burrowing gastropods, although 
its shell morphology does not reveal any burrowing behaviour (Savazzi, 1994). Two distinct 
types of activites were studied here, namely burrowing and locomotion. In the former 
activity, the nature of the burrows is in the form of short siphon tubes, suggesting that the 
gastropod is a suspension feeder. The close association of these gastropods suggests that 
they are non-aggressive and non-competitive, but still opportunistic.  
 
Studies have suggested that in intertidal areas with extensive tidal oscillations, 
organisms are active during one phase and inactive during the other phase of tidal activity 
(Naylor, 1987). In the present study, burrowing/feeding activity is interpreted to be related 
to high tide, thus enabling the gastropods to suspension feed. During low tide the intense 
thermal gradient and desiccation might instigate the gastropods to undertake excursions, 
during which meandering locomotion traces are produced. The burrow at the end of the 
trace is interpreted to be a temporary resting burrow made in order to avoid the thermal 
gradient.  
 
Conclusions 
 
Architectonica, the fastest burrowing gastropod, inhabits intertidal stress zones. 
Their activities are governed by tidal fluctuations.  
 
1) During high tides, burrows are stabilized and the animal does not come out of its 
burrow, being a suspension feeder. 
2) The dense burrow systems indicate non-aggressive, non-competitive behaviour.  
3) During low tides, the gastropods leave the burrow and undertake short random 
excursions. 
4) Due to extreme exposure and to avoid desiccation, they make inclined temporary 
shelters at the end of the traces, which have raised rims.  
 
Acknowledgement: Author is grateful to Director-School of Petroleum Technology for providing 
opportunity. Part of the work was done at M. S. University of Baroda during the doctoral work for 
which author is thankful to Dr. Satish J. Patel (MSU).  
 
 
 
 
Biogenic Sedimentary Structures Produced by Architectonica laevigata (Gastropod: Architectonicidae), 
Mandvi Intertidal Zone, Gulf of Kachchh, Western India: Desai 
 
 
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Biogenic Sedimentary Structures Produced by Architectonica laevigata (Gastropod: Architectonicidae), Mandvi Intertidal Zone, Gulf of Kachchh, Western India

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Biogenic Sedimentary Structures Produced by Architectonica laevigata (Gastropod: Architectonicidae), Mandvi Intertidal Zone, Gulf of Kachchh, Western India

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