Krem Bylliat: The Harbour of Precedent Cavernicolous Representatives from the Jaintia Hills, Meghalaya, India
Daniel B. Harries
The subterranean mode of life always needs a high degree of biological adaptation. The cavernicolous species usually get selected from those which are preadapted with biological traits suitable for cave life and finally occupied a separate taxonomic status. With the ever going exploration of subterranean passages in Jaintia hills, till date several troglobitic species have been recorded from this particular area. Cave biota survey with respect to the explored subterranean passages of the area was conducted in February 2011. Krem Bylliat (cave) is one of them, measure horizontally 600 m having several openings. The cave is situated in the boundary of two major rock formations, nearer to one of the main tributary of river Kopili. Though, the cave is harbour of rich biodiversity, it was found to be relatively impoverished in terms of troglomorphic taxa. Possible factors, obviating the evolution of troglomorphy in this cave have been discussed.
August 09, 2011; Accepted: October 22, 2011;
Published: December 10, 2011
Perpetual darkness, sporadic supply of nutrients, near constant environmental
conditions and high CO2 percentage are some of the common features
for almost all the subterranean caves. Although all these together make caves
inhospitable, many organisms inhabit subterranean caves successfully. High degree
of physiological adaptations, behavioural adjustments and phenotypic alterations
are needed to establish a population permanently in such conditions (Vandel,
1965; Gunn, 2004; Biswas, 2009,
2010) and due to which the most common characters appears
in them are absence of pigment, reduction of the optic apparatus (eyes), elongation
of appendages and developments of extra sensory organs often referred as troglomorphic
traits. On the other hand, low predation pressure, high humidity, easy availability
of prey and even the negligible effects of natural environmental calamities
(Biswas and Shrotriya, 2011) are some of the other factors
of the same cave that altogether attract many opportunistic species to exploit
these habitats. In general cave dwelling/adapted organisms usually evolve from
ancestral species with pre-adapted biological traits, favouring the cave life
(Vandel, 1965; Gunn, 2004). Conclusively,
two types of organisms could be found inside any cave; (1) the animals once
trapped accidentally or get intentionally into the cave start successfully their
phylogenetic race inside the cave, referred as obligatory type, (2) the animal
frequently visiting or almost settled inside the cave for fulfillment of their
certain needs of life, such as feeding, roosting, hibernating, breeding etc.
can be referred as opportunistic. Opportunistic types are often seen to depend
on their ambient external environment for some of their biological needs. However,
the opportunistic cave dwellers are often acting as empirical models of natural
selection and adaptation in the subterranean environment (Kane
and Culver, 1992; Sahu et al., 2011).
State Meghalaya contains some of the most significant areas of karst within
the Indian subcontinent. The limestone is of Cretaceous to Miocene age and it
forms an almost continuous outcrop along the border with Bangladesh on the southern
margin of Meghalaya (Fig. 1b). Much of this area has high
elevation and the limestone deposits can have a depth potential up to 500 m.
The state is also well known for its high rainfall with southern Meghalaya receiving
more than 10,000 mm rainfall per year (Rai, 2010). The
well developed limestone deposits and high rainfall has resulted in the development
of numerous and extensive subterranean drainage passages.
The Jaintia Hills district of state Meghalaya is of particular importance as
a cavernous area due to the large extent of karst and general high elevation
(up to 1200-1500 m). The area is mostly composed of Tertiary rocks of the Jaintia
Group and the group itself represents the entire eocene shelf sediments of Meghalaya
||(a) Subcontinent India; indicating the location of state Meghalaya
(b) State Meghalaya; indicating the location of district Jaintia Hills alongwith
the existing outcrop Limestone belt (c) District Jaintia Hill; indicating
the karst-complex location and where the cave Krem Bylliat exist
(d) Location where Krem Bylliat and few other caves exists and (e) Map of
Krem Bylliat, locating each and every entrance, water canals and dripstone
Many hundreds of caves have been recorded within the Jaintia Hills and some
are internationally significant in terms of extent (e.g., passage lengths up
to 30 km and depth range up to 300 m). Each year further caves are added to
the records and many kilometers of additional cave passages are mapped. The
full extent of cavernous habitat in the Jaintia will not be established for
many years. However, the biospeleology of the region is poorly known (Kottelat
et al., 2007; Biswas, 2009; Harries
et al., 2008; Disney, 2009) and only few
caves have been subject to detailed biological study.
In the present study, a biotic survey report of Krem Bylliat; one of the recently explored cave of Jaintia hills has been documented. Its biotic components reflect almost the same picture which has already been documented earlier from the various subterranean passages of that area. However, the lacks of degree of troglomorphism in such taxa are of great interest. The possible factors suppressing the process of such evolution has been tried to correlate with the adjacent abiotic factors.
Surveyed cave description: Krem Bylliat (N 25°2542.70;
E 92°3606.50 (WGS84); altitude 732 m above sea level) is situated
in Pala-range of Jaintia Hills within 50 m of the banks of the River Kopili.
The total length of the cave has been mapped as 624 m with a vertical range
of about 4.5 m (Fig. 1e) by Meghalayan Adventurers Association.
The northern entrance (Entrance 2) of the cave is located at the base of a 3
m deep doline which is densely vegetated by bamboo trees (Fig.
2a). The cave begins as a phreatic tube; the passage floor from the entrance
(Entrance 2) to the end of twilight zone is laterally divided into two parts
(Fig. 2b). On the left the floor is dry and mostly covered
by flowstone deposits whereas on the right there is a stream bedded by mud-clay,
alluvial gravel and sandstone pebbles. The structure of the cave passage deeper
within the cave remains broadly similar to this entrance area.
||Images of Krem Bylliat. (a) Entrance-2; surrounded by bamboo
trees (b) Twilight zone (Entrance-2) clearly indicating the path divided
into two parts; left flawstone formation; right water passage. Roof and
side walls are clearly indicating two different formations and (c) One after
one rimstone pools nearer to the Entrance 2
A small stream from the river tributary flows continuously through the cave
and it appears that significant flooding occurs on a seasonal basis. About ~40
m within the cave from Entrance 2 there is a deep (approx. 2 m) canal (Fig.
1e). The twilight zone ends at this canal because three consecutive rimstone
dams cross the canal and come sufficiently close to the ceiling to cut out the
remaining light (Fig. 2c). Beyond the canal and dams the passage
becomes considerably larger. At about 300 m within the cave there are three
additional openings to the surface with associated twilight zones (Fig.
1e). Beyond these entrances the passage continues through areas with prominent
calcite dripstone formations suspended from the ceiling before terminating at
a sump at the southern end of the accessible cave.
Humidity and temperature were measured by digital thermo-hygrometer (Pacer® TH 402) and were found to be constant throughout the cave; i.e., 100% humidity and the atmospheric temperature 16°C.
Faunal components of the cave: In February 2011 the first author participated in an international cave mapping expedition (organized by Meghalayan Adventurers Association). The base camp was located in the Pala range of the Jaintia Hills in close proximity to Krem Bylliat. Over a fifteen day period the first author spent each day; three to four hours within the cave directly recording the fauna. All sub-habitats and crevices were carefully scrutinized and the fauna was photographed in situ. Aspects of their ecology, distribution, behaviour and response to disturbance were noted where appropriate.
NOTES ON BIOTA
Vertebrates: Myotis longipes Dobson, 1873, the microchiropteran
bat is commonly known as the Kashmir cave-bat, because it was initially thought
to be restricted to the caves of Kashmir (India). Subsequently, the species
was reported from caves in adjacent countries such as Nepal and China (Talmale
and Pradhan, 2009; Bates and Harrison, 1997). In Krem
Bylliat; M. longipes was found roosting on cave walls in the twilight
zone of Entrance-2. This area of the cave has a relatively low ceiling and frequent
observations of partially consumed bat corpses indicate that they are vulnerable
to predation (Fig. 3a). Similar reports of apparent bat predation
have earlier been noted from Dandak cave of Chhattisgarh, India (Biswas
and Shrotriya, 2011). M. longipes appears to have a wide distribution
in Meghalaya and has previously been reported from Mawsmai Cave in the East
Khasi Hills and Siju Cave in the South Garo Hills (Sinha,
1999a, b). Further, a small colony of rhinolophid
bats (unidentified) was noted roosting in the roof of the passage well within
the dark zone of the cave.
A small population of about 8-10 individuals of frog; Odorrana chloronota
Günther, 1875 (Fig. 3b), was always apparent at the edges
of the rimstone pools close to Entrance-2. The species is endemic to the Northeastern
part of India and adjacent Southeast Asian countries (Bain
et al., 2003; Stuart et al. 2006).
Characteristic features include a spectacular vivid green dorsal colour and
a peculiar odoriferous skin secretion. This frog was not found to respond any
disturbance so quickly. Epigean populations of this frog are known to be nocturnal
and occur in wet habitats. Presumably the combination of low light and damp
conditions at this transition zone of the cave are favourable to the species.
The outer canal of the twilight zone near Entrance-2 contained a number of
unidentified fish species including loach, carp and a species of Glyptothorax.
The carp and Glyptothorax was found to occupy the bottom level of the
canal and were very sensitive to any disturbance. The smaller fishes, especially
the loach were usually apparent at the edges of the canal. Surprisingly, not
a single specimen of any fish was found in the isolated rimstone water-pools
exist a little further into the cave (Fig. 2c). The larger
fish (especially Carp) were 15 cm or more in length, however not a single specimen
represented any trace of troglomorphy.
Invertebrates: A shrimp population; Macrobrachium cavernicola Kemp,
1924 (Fig. 3e) was highly abundant in the outer canal
of the twilight zone near Entrance-2 and smaller specimens were easily captured
near the edges of the canal. The distinctive two-segmented mandible palps helped
us to identify it as M. cavernicola. This troglomorphic species was first
recorded from Siju Cave of Meghalaya, India (Kemp, 1924).
The species has subsequently been recorded from caves throughout Meghalaya including
many of the Jaintia caves (Biswas, 2009; Harries
et al., 2008). Interestingly, the adult form of this shrimp was also
recorded in the inner rimstone pools and in further deeper zone of the cave
where no other large aquatic fauna were seen. The adults are completely albinic
and have small eyes. The juveniles were always apparent nearer the entrance
zones of all the caves surveyed by our team of that area (Fig.
The walls and roof of the Krem Bylliat was found to be occupied by Huntsman
spider; Heteropoda fischeri Jager (2005) (Fig.
3f) which are very large spiders with the leg span of adults reaching up
to 15 cm. It was 1st of all reported from the Krem Labbit which exist hardly
10 km apart from this cave.
||Organisms inhabits in Krem Bylliat. (a) Partially consumed
corpses of a bat; Myotis longipes recovered from the twilight zone
of Enterance-2, (b) Frog; Odorrana chloronota sitting in the edge
of a rimstone pool, (c) Fishes apparent in the 1st water canal exist in
the twilight zone of Entrance-2, (d) Crabs (possibly Maydelliathelphusa
falcidigitis) present in the 1st water canal exist in the twilight zone
of Entrance-2, (e) Partial troglomorphic shrimp; Macrobrachium cavernicola
present in the water canal of inner chambers, (f) Huntsman spider; Hetropoda
fischeri dominating throughout the cave, (g) Opiliones; apparent in
all the enterance zone till twilight range and (h) Cricket; nymph of Rhaphidophoridae
The predator-prey relation between this spider and the cave crickets was already
reported from other Jaintia caves (Harries et al.,
2008). Further, the juveniles of an unidentified brown cricket were abundantly
observed in the twilight zones of Krem Bylliat and even a group of these juveniles
were seen feeding upon the dead body of a bat nearer the Entrance-2. The crickets
were more sparse deeper within the cave where adults were also present.
Dark crabs; Maydelliathelphusa falcidigitis Alcock, 1910 (Fig.
3d) were noted in the twilight zone near Entrance-2 and often in some cavities
exist in the deeper zone within the cave. It is also a common species reported
from almost all the subterranean caves of Meghalaya (Biswas,
2009; Harries et al., 2008). Further, densely
aggregated dark black coloured opiliones were frequently encountered on passage
walls in every twilight as far back as the transient zones of this cave. They
were highly sensitive to any type of disturbance and rapidly dispersed in response
to small stimuli. Opiliones are usually omnivorous feeding upon materials such
as small invertebrates, detritus, fungi, carrion, guano and other fecal material.
They are adapted for life in dark conditions and use their second pair of legs
as sensory antennae. These sensory adaptations and the ability to exploit a
variety of food sources are likely to be advantageous in a cave habitat. It
is possible that they exploit shaded environments simply to avoid desiccation
and to link the cave environments is purely incidental. They have been noted
in shaded rock gullies several meters beyond cave entrances and this indicates
that the habitat preference might be for shade rather than specifically for
cave entrances. Earlier also in addition to the troglomorphic Opiliones
sp., similar aggregations of black opiliones have been recorded from the threshold
area of several other caves in Meghalaya, (Harries et
al., 2008). Surprisingly, not a single specimen of both the above species
In addition to the above organisms, time to time few additionals were also seen inside the deep passages, but due to lack of their any permanent population we considered them either habitual or accidental trogloxene for this particular cave.
Till date several long and deep subterranean caves have been explored and mapped
from Jaintia Hills of the state Meghalaya, India, most of them have passage
lengths of many kilometers and a depth range of well over 100 m. This ensures
an extensive dark zone and a diversity of habitats including stable
dry fossil levels as well as flood prone stream passages. In contrast; Krem
Bylliat is a relatively small cave has multiple entrances and consequently no
part of the cave is much more than 150 m from an entrance. It also has a very
limited vertical depth range (~4.5 m) and consists almost entirely of flood
prone streamway. These factors probably explain the relatively impoverished
community recorded within the cave. In the present survey, none of the taxa
in Bylliat exhibited pronounced troglomorphy. Among the tabulated ones, Krem
Bylliat found to be shared six taxa with the other Meghalayan caves, few of
which are very common. One of the Bylliat species showed partial troglomorphy
(Macrobrachium cavernicola). Earlier reports already pleaded the existence
of nine partially troglomorphic taxa in other Meghalayan caves and three of
these (a species of beetle and two isopods) occur in almost every caves (Harries
et al., 2008). In addition, few unidentified species were also noted
in the adjacent caves (Fig. 1d) during the survey period (data
unpublished). Notably, a troglobitic loach; Schistura papulifera was
recorded from the adjacent cave Hostage in the region (Fig.
1d) which is slightly longer (746 m) than Krem Bylliat but has a greater
vertical range (28 m).
Interestingly during the survey period, O. chloronota which is always present in this cave was not at all conspicuous in its adjacent caves (Fig. 1d). Possibly, the twisted and/or vertical entries of such caves act a hurdle for its establishment. Nevertheless, the lacks of its population from such caves having large entry and big water canals are of great interest. However, there is currently no evidence to suggest, they sustain stable reproducing populations within the caves.
Krem Bylliat contains many of the species that have been previously noted as
characteristic components of the Meghalayan cave communities (e.g., bats, cyprinids,
loach, Glyptothorax, Macrobrachium, freshwater crabs, Heteropoda,
brown rhaphidophorids) and it appears typical of superficial cave habitats in
the Jaintia Hills. Though, the distribution of fauna within Krem Bylliat is
broadly similar to that of other caves in the Jaintia Hills (Harries
et al., 2008), the apparent partial/complete troglomosphism in such
species are completely lacking. In Krem Bylliat the fish species were restricted
to the threshold area but previous records demonstrate that these taxa also
frequently occur deep within caves. The reason for their absence from the dark
zone of Krem Bylliat is interesting. It could be speculated that, due to having
the multiple entrances in Krem Bylliat the deep zone and/or stagnant zones are
completely lacking and due to which the required habitat for complete troglomorphy
is absent here. Further, given the degree of water flow during the rainy season
it is unlikely that the subterranean and epigean populations are spatially segregated.
The species may be sufficiently adaptable to exploit both cave and surface habitats
depending on conditions. Further study of the ecology of this species would
Macrobrachium cavernicola did occur in the dark zone of Krem Bylliat
and were also found in surface streams in the vicinity of this and other (Krem-Labbit
Ksheh, Krem-Diengjem, Krem-Shallong) caves. Earlier besides the deeper zones,
a subterrnaen Solvenian shrimps Troglocaris sp. has already been reported
to observe in the illuminated parts of the caves (Sket,
1965). Partial troglomorphism in it suggests that the species is highly
pre-adapted to dark and other geophysical conditions of subterranean mode of
life and thus could be able to adopt quickly the subterranean mode of life.
It is likely that the main energy supply to the biota of Krem Bylliat is derived from material carried on the cave stream. Like many cavernicolous species most of the taxa are probably generalist feeders able to exploit a variety of food sources opportunistically. Of course the Heteropoda are specialist predators but a plentiful food source is available in the form of the brown cave crickets and the close proximity of the surface means that occasional stray surface species are also likely to be available as prey items. The bat populations are another potential energy source and carcasses were certainly seen to provide a food source for the brown cave crickets. No significant guano deposits were found and this is true of many of the Megalayan caves presumably because guano is regularly swept away by seasonal floods. The bats themselves were seen to be subject to predation (Fig. 1a) but the identity of the predator is unknown. It is likely that bats roosting in Krem Bylliat are particularly accessible to external predators due to the limited extent and multiple entrances of the cave.
The study reinforces the conclusion that there is a degree of predictability
to the composition of the cavernicole communities in the region and illustrates
the relationships between habitat extent and cavernicole diversity and between
surface proximity and frequency of occurrence of troglomorphic species. Finally,
we have also to accept the hypothesis that the degree of troglomorphy does not
absolutely reflect the strength of the troglobiosis(Sket,
We are very grateful to Mr. Brain D Kharpran (Meghalayan Adventurers Association),
Mr. Thomas Arbenz and Swiss Society of Speleology for allowing us to use the
map of Krem Bylliat to use in this manuscript. Thanks are also due towards Dr.
Manuel Ruedi for his time to time unreserved help during the field study and
the Natural History Museum of Geneva, Switzerland, for financial support to
the 1st author conduct this survey.
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