Biodiversity
Biodiversity (jib-baichitra) the wealth of life forms found on earth including the millions of plants, animals and microorganisms, the genes they contain, and the ecosystems they form. It is considered at three different levels genetic diversity, species diversity, and ecosystem diversity. Genetic diversity is the variability within a species, measured by the variation in genes within a particular species, variety, subspecies or breed. Species diversity is the variety of living organisms on earth, measured by the total number of species in the world or in a given area. Ecosystem diversity is a measure of the variety of the ecological complexes of organisms and is related to physical and ecological variations in an area.
Scientists have variously estimated that there are from 3 to 30 million extant (living) species, of which 1.4 million have been classified, including 2,50,000 plants, 7,50,000 insects, and 41,000 vertebrates; the remainder are invertebrates, fungi, algae, and microorganisms. It is estimated that over 50% of the world’s species are found in the moist tropical forests which cover only 5-7% of the earth’s land area.
Biological diversity helps prevent extinction of species and helps preserve the balance of nature. At the 1992 United Nations Conference on Environment and Development, over 150 nations, including Bangladesh, signed a treaty to preserve the planet's biological diversity. Unfortunately there is no proper inventory of the biological diversity of the country and the primary data for most of the flora and fauna are far from complete. However, the available data on the diversity of the biological resources of Bangladesh, both at species and ecosystem level, are discussed below:
Flora Bangladesh has been endowed with a rich plant diversity base because of its fertile alluvial land, warm and humid climate. More than 6000 plant species occur in Bangladesh, of which 300 or so species are exotic and 8 are endemic. Ninety-five vascular plants have been rated as threatened, of which 92 are angiosperms, and 3 gymnosperms. About 2000 species and varieties of algae have been recorded. The fungal flora has been recorded. There are about 250 species of bryophytes in the country.
Of the 195 species of pteridophytes that occur in Bangladesh, 230 are ferns. There are 3611 species of flowering plants (angiosperm) in the country. Bangladesh has 7 species of gymnosperms; of these 3 are threatened (1 cycas, 2 gnetum). The country has 3 species of rice, of which there are about 10,000 varieties.
The genus Nymphaea (Nymph in Greek mythology: the beautiful goddess of water) has about 50 species worldwide. Bangladesh has two species: N. nouchali (blue variety) and N. pubescens (white variety). The white variety is regarded as the national flower. Another nymphaceous plant is the lotus, Nelumbo nucifera; flowers are rose pink to white and fragrant. Hindus use this flower in the Durga Puja festival; it is also used in the indigenous system of medicine; and its ripe seeds are edible. jackfruit (Artocarpus heterophyllus) of the family Moraceae, is the national fruit of Bangladesh. It is a large fruit, contains 100-500 large, oily seeds. It originated in the forests of the Western Ghats (India), where it still grows in the wild. It is grown throughout Bangladesh but Naogaon, Dinajpur, Savar (Dhaka), Madhupur (Tangail) and Sylhet are important areas for producing this fruit.
The main types of forests that occur in Bangladesh are the following: (i) Tropical evergreen and semi-evergreen; (ii) Tropical moist deciduous (inland soil forests); (iii) Tidal swamp forest; and (iv) Fresh water swamp forest. The tropical evergreen and semi-evergreen forests are more prevalent on the lower slopes of the hills from the plain land up to 600 metres in the NE and SE of the country. Tropical moist deciduous forests are a mixture of several species in the top canopy. Shorea robusta is the dominating species. Terminalia and Albizia are the common associates. It occurs in the north, northwestern and central parts of the country. The most easterly occurrence of sal forest is in Comilla. In the northwest, the belt extends to several districts, and as it runs towards the southeast through Mymensingh, Tangail, and Gazipur districts it gets much narrower and finally runs into the Tipperah hills of India. A tidal swamp forest or mangrove forest is typically a closed evergreen forest, 6 m or more in height, composed of trees especially adapted to survive on tidal mud, which is permanently wet with moderately salt water and submerged at every tide. Some species, particularly among the Rhizophoraceae, grow on stilt roots and send up knees (Heritiera) or pointed pneumatophores (Sonneratia, Carapa, Amoora), whilst Litsea sp. has long bifurcating aerial roots.
Mangrove forest is limited to the Ganges delta in the south (Sundarbans) and the chakaria sundarban (now heavily degraded) in the delta of the matamuhuri River, south of Chittagong in the SE. Freshwater swamp forests, completely inundated during the rainy season, are often called ‘reedlands’ (locally known as Pajuban) due to the predominance of reeds like Nal (Phragmites karka), Khagra (Saccharum spontaneum), and Ekra (Eranthus ravannae). Tree species include Hijal (Barringtonia acutangula), Jarul (Lagerstroemia speciosa), and Bhurii/Pitali (Trewia nudiflora). These forests are found in the low-lying areas (haors) of Sunamganj and North Sylhet in the NE of the country.
Bangladesh has been tentatively divided into 30 agroecological zones, which have been subdivided into 88 agroecological sub-regions. These have been further subdivided into 535 agro-ecological units. Following are the important plant groups' of Bangladesh:
Algae The group of plants belonging to the most primitive subkingdom, Thallophyta, that lack true roots, stems, leaves and flowers. Unlike the Fungi, the other large group of thallophytes, it has chlorophyll. They are worldwide in distribution and form the chief aquatic plant life both in the sea and in freshwater. In fact all seaweeds are marine algae. The blue-green algae and green algae include most of the fresh water forms. Algae, the major food of fish, are a keystone in the aquatic food chain of life; they are the primary producers of the food that provides the energy to power the whole system. They are also important for supplying oxygen to aquatic life through photosynthesis. Seaweeds have long been used as a food, especially in the Orient.
In Bangladesh algal species could be subaerial (grows on tree trunks, walls of buildings, rocks and stones, tins, metallic poles, etc), terrestrial (grows on damp soils), and aquatic. The aquatic forms occur in freshwater (ponds, ditches, lakes, rice-fields, rivers, beels, haors), brackish water (in the Sundarbans), and seawater (marine habitat). In Bangladesh the algal species include both benthic and phytoplankton members of Cyanophyceae, Chlorophyceae, Charophyceae, Euglenophyceae, Rhodophyceae, Bacillariophyceae, Chrysophyceae, Xanthophyceae and Chloromonadinae. More than 300 species and varieties of freshwater algae have been recorded from Bangladesh.
Fungi A kingdom of plantlike organisms lacking chlorophyll, and largely live as parasites or saprophytes. Like algae, fungi lack the vascular tissues (phloem and xylem) that form the true roots, stems, and leaves of higher plants. It may be separated into two groups: the slime molds (Myxomycota) and the true fungi (Eumycota). The true fungi are divided into 4 classes: the algal-like fungi (Phycomycetes), the sac fungi (Ascomycetes), the basidium fungi (Basidiomycetes), and the imperfect fungi (Deuteromycetes). About 100,000 species of fungi have so far been recorded worldwide.
The fungal flora in Bangladesh has not yet been fully recorded. However, the humid climate of the country is congenial for fungal organisms and a rich fungal biodiversity is expected to occur in the country. As agriculture is the mainstay of Bangladesh, many fungal plant pathogens have been described that infect major crops such as rice, sugarcane, jute, tea, potato, tomato, brinjal, chilli, wheat, maize etc. Economically important fungi include the yeast and edible mushrooms.
Lichen Slow-growing plant of simple structure, composed of blue-green or green algae and of fungi living together in a symbiotic relationship. They commonly grow on rocks, trees, fence posts, and similar objects. Its typical greenish grey colour is due to the combination of the chlorophyll of the algae with the colourless fungi, although the thallus sometimes may be red, orange, or brown. The fungi obtain food from algal cells and, in turn, absorb and retain water that is partially used by the algae for photosynthesis. They usually reproduce simultaneously. The fungi produce acids that disintigrate rock, giving the lichen a better hold and aiding weathering processes, which usually turn rock into soil.
Lichens can withstand great extremes of temperature and are found in arctic, antarctic, and tropical regions. They are often the pioneer forms of life. Before the discovery of aniline dyes, lichens were much in use for dying silk and wool. The blue and purple dyes, litmus and archil are still obtained from species of lichens. Others have been used in perfume manufacturing and brewing. About 20,000 species of lichens occur worldwide. The algal components mostly belong to Cyanophyceae or Chlorophyceae. In the majority of the lichens the algae are unicellular. The common algae are Nostoc, Stegonema, Rivularia, Gloeocapsa and Trebauxia. The fungal components are mostly Actinomycetes group. The common lichens found in Bangladesh are the species under the genera Parmelia, Usnea, Dermatocarpon, Phaeographina, Leptogonium, Lecanora and Anaptychia.
Bryophyte A division of green land plants that includes the mosses (class Bryopsida), the liverworts (class Marchantiopsida), and the hornworts (class Anthocerotopsida). They differ from ferns, cone-bearing plants, and flowering plants in that they lack a vascular system for the transportation of water. Since their cells must absorb water directly from the air or the ground, nearly all bryophytes grow in moist places. The mosses are generally divided into three orders, the order Bryales being most prominent. The bryophytes are important because they are pioneer plants and soil builders on surfaces lacking other vegetation. Sphagnum moss is used as packing material and as peat. It is now believed that the bryophytes descended from green algae by way of now extinct ancestors (the Rhyniophyta).
Bryophytes are distributed from the Polar Regions to the tropics. There are about 24,000 species of bryophytes worldwide. Most are small, usually 2 to 5 cm tall, the smallest one in Bangladesh is about 4 mm. A few bryophytes are about 30 cm long. Bangladesh's hot and humid climate is appropriate for the luxuriant growth of bryophytes. They grow especially on hills and forests throughout the year. In Bangladesh there are about 250 species of bryophytes, in 92 genera, 34 families, 14 orders, and 3 classes. Riccia, Marchantia, Cyathodium, Dumortiera, Pallavicinia, Plagiochasma, and Chiloschyphus are common and grow on soil, old damp bricks, etc. Lejeunea, Frullania and Jungermannia are common epiphytes.
Ricciocarpus natans and Riccia fluitans are the only two aquatic hepatics reported from Bangladesh. Anthoceros and Notothylas of the class Anthocerotopsida are usually found on soils along the streams and rivers or on moist soil. Semibarbula orientalis and Hyophila involuta grow on walls and bricks and Calymperes, Taxithelium and Erpodium grow on the bark of trees. Other common mosses in Bangladesh are Fissidens, Bryum, Splachnobryum, Hydrogonium, Physcomitrium, Philonotis, Garckea, Gymnostomiella, Leucophanes, Octoblepharum, Isopterigium, Vesicularia, Glossodelphus, and Plagiothecium.
Pteridophyte These are simple type of vascular plants. The pteridophytes comprise 4 classes: the Psilosida, including the most primitive vascular plants, found mainly in the tropics; the Lycopsida, including the club mosses; the Sphenopsida, including the horsetails; and the Pteropsida, including the ferns. They are mainly terrestrial, non-flowering plants characterized by the presence of a vascular system; the possession of true stems, roots, and leaves; and by a marked alternation of generations, with the sporophyte forming the dominant generation in the life cycle.
They do not produce seeds. Today there are about 12,500 pteridophytes distributed mostly in tropical and subtropical regions; most are ferns (about 11,000 spp.). About 900 species grow in the subcontinent; of these about 50% are endemic. Bangladesh has 195 species of pteridophytes, which grow either as epiphytes, mesophytes, lithophytes or hydrophytes.
Angiosperm Flowering plants in which the ovules, or young seeds are enclosed within an ovary (that part of the pistil specialized for seed production), in contrast to gymnosperms, in which the seeds are not enclosed within an ovary. The angiosperms constitute the division Magnoliophyta and include all agricultural crops (including the cereal grains and other grasses), all garden flowers and most horticultural plants, all the common broad-leaved shrubs and trees, except conifers, and all the usual field, garden, and roadside weeds. They are the most economically important group of all plants. It is estimated that there are 3611 angiosperm species in Bangladesh, including both wild and exotic plants. Of these 92 species have been rated as threatened. Of the above mentioned 5000 species of angiosperms, 8 are endemic to Bangladesh.
Gymnosperm Plants whose seeds are exposed, ie not enclosed within an ovary. No carpels are present, and there are no vessels in the xylem tissue. The major surviving group is the conifers, which are characterized by needle-like leaves and cones. Gymnosperms are represented by about 725 species in 70 genera. These plants are considered the transition plant group in the evolutionary line between the non-flowering plants (pteridophytes: ferns), and closed seeded plants (angiosperms), since they have resemblances in their characters with both these groups. About 350 million year-old fossil gymnosperms have been found in rocks. They are predominantly distributed as temperate, subalpine or subhimalayan plants.
In Bangladesh 7 species in 3 genera occur in the eastern hilly regions. Of these 3 are threatened, 1 cycas, 2 gnetum. The main threats are habitat destruction and exploitation by local people for various uses. Different species of exotic pine (Pinus carribeana) are grown in the hilly regions and as ornamental plants in gardens. Exotic gymnosperms like Pinus, Cycas, Araucaria, Cupressus, and Thuja are now well-adapted and are prized garden plants.
Agricultural biodiversity Biological resources that are used in the agricultural programmes. Because of the agro-ecological variations of the country people over the centuries have been cultivating, preserving, and using more than 1364 plant species coming from both endemic and exotic origins, for about 85 diverse uses. There are about 175 species of medicinal herbs. Many varieties of rice, jute, sugarcane, cotton, linseed, mustard, cucumber, bean, gourd, banana, mango, etc have also been selected and raised by the people who have been living in this area for about 8-10 thousand years. A large number of flora are being cultivated in the homesteads.
Bangladesh has 3 species of rice: Oryza sativa, O. coaractata, and O. rufipogon and there are about 10,000 varieties of rice in the country. In the sundarbans and the Chittagong Hill Tracts, there are wild species of rice. The low basin areas of Gopalganj and Sylhet are considered to be the centre of origin of the deepwater rice varieties. Many indigenous rice varieties have been lost due to the introduction of high-yielding varieties (HYVs). Wheat, Triticum aestivum, is now the second staple food crop of the country. Except for one indigenous strain all the plant genetic resources (PGR, 15,730) of common wheat have been introduced. Most minor cereals are of an endemic nature. There are a small number of foxtail millets, proso millets, and others. In case of jute there are 958 accessions of Corchorus capsularis (Titapat/Sadapat/Bogipat). There are 10 annual oilseed crop species having more than 1200 plant genetic resources (PGR). Brassica campestris (mustard) and B. juncea (rapeseed) are of both endemic and exotic origins. About 500 PGR of the species that are available are being used for the development of newer varieties. In addition, B. napus, B. carinata and B. nigra were introduced to Bangladesh during the early 1970s. Groundnut (420 PGR), soybean (145 PGR), and sesame (132 PGR) are the three other species of oilseeds. Soybeans of American types were introduced to Bangladesh during the early 1970s. Wild indigenous soybean PGR could be found in the Chittagong Hill Tracts. Recently oil palm has been introduced into the country. Of the 7099 PGR of pulses and food legumes, 3463 are of local origin from 8 species, the rest imported. Bangladesh is known as the centre of origin of sugarcane which has yielded many genetic resources: 459 Saccharum officinarum and 26 S. spontaneum PGR.
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There are 33 common fruit species with a high number of PGR. A total of 463 variants of mango, pomelo, guava, and jackfruit have been recorded in different institutes and orchards. The minor fruits usually come from 54 species that have 298 variants, of which 207 are of local origin. There are 52 species of fruit trees in the country that are wild in nature. There are three types of PGR that produce vegetables from roots and tubers (11 species), leaves (8 species), and fruits (20 species). These 39 species have more than 1000 PGR. The local collections of clones of tea are 246, and the introduced varieties amount to about 28. Coffee has three species but it is not yet a commercial crop in the country.
Forest flora About 3611 species of flowering plants occur in Bangladesh. Of these about 700 are forest trees. Of the woody taxa, family Leguminosae contains the highest number of trees, followed by Euphorbiaceae, Moraceae, Lauraceae, Verbenaceae, and Myrtaceae. The first category of trees in the forests of the Chittagong Hill Tracts are Dipterocarpus turbinatus, D. costatus, Artocarpus chama, Swintenia floribunda, Protium serratum, Toona ciliata, Canarium resiniferum, Calophyllum polyanthum, Michelia champaca, Pterygota alata, Tetrameles nudiflora, Amoora chittagonga, Aphanamixis polystachya, Chukrasia tabularis, Podocarpus neriifolius, Syzygium spp., etc. Some of the deciduous trees are Albizia procera, Bombax ceiba, B. insignis, Garuga pinnata, Adina cordifolia, Hymenodictyon orixensis, Duabanga grandiflora, Dillenia pentagyna, Gmelina aborea, and Terminalia spp. The common bamboo species are Melocanna baccifera, Bambusa burmanica, B. polymorpha, B. tulda, Schizostachyum dullooa and Dendrocalamus longispathus.
The top storey of the Sylhet forest comprises Artocarpus chama, A. lacucha (=A. lakoocha), Elaeocarpus robustus, Holigarna caustica, and Dysoxylum spp. The middle storey is formed by Mesua ferra, Amoora wallichii, Palaquium polyanthum Sapium baccatum, Chisocheton spp., Lagerstroemia speciosa, Duabanga grandiflora, Schima wallichii, etc. The deciduous species are Bombax ceiba, Adina cordiflia, Hymenodictyon orixensis, Spondias pinnata and Ficus spp.
The major tree species of scrub forests are Schima wallichii, Sterculia villosa, Vitex peduncularis and Engelhardtia spicata. Members of dwarf fan-palm, Licuala spp. are found in the Jaflong area.
Sal (Shorea robusta) is the dominant species of the moist deciduous sal forests and usually forms 25% to 75% of the upper canopy. Its associates are other deciduous species like Adina cordifolia, Albizia procera, Bombax ceiba, Butea monosperma, Lagerstroemia parviflora, Dillenia pentagyna, Garuga pinnata, Hymenodictyon orixensis, Semecarpus anacardium, Miliusa velutina, Schleichera oleosa, Terminalia bellerica.
The dominant tree species of the Sundarbans is ‘Sundari’ (Heritiera fomes) which forms mixed stands with Excoecaria agallocha, and in varying proportions with species of Bruguiera sexangula, B. gymnorrhiza, Avicennia alba, A. officinalis and Sonneratia apetala, Xylocarpus mekongensis, X. granatum, Lumnitzera racemosa, Rhizophora mucronata, Ceriops decandra, Cynometra ramiflora and Amoora cucullata. The Nipa palm (Nypa fruticans) generally occurs along the banks of the rivers and streams, and needs regular inundation.
Fauna Bangladesh possesses a wide range of invertebrates and vertebrates in its aquatic and terrestrial habitats. The invertebrate (any animal lacking a backbone ie all animals except the vertebrates and lower chordates) fauna of the country has not yet been fully recorded. However, the warm and humid climate of the country is favourable to lower organisms, especially the insect fauna. There has been a fairly good stocktaking of the vertebrate (animals with a backbone) fauna (fishes, amphibians, reptiles, birds and mammals).
hilsa (Tenualosa ilisha) of the family Clupeidae, order Clupeiformes, is recognized as the national fish of Bangladesh. The fish is locally known as ilish. Its related species is T. toli. The fish is anadromous, ie it moves towards a riverine environment from a marine environment during the breeding season. Hilsa constitutes the largest single fishery in the open waters of Bangladesh in both inland and marine sectors. Magpie-robin or Oriental Magpie Robin (Copsychus saularis), locally known as Doel of the family Muscicapidae, order Passeriformes, is the national bird of Bangladesh. This trim black-and-white bulbul-sized, cocked tail bird is found throughout the country. The male is brighter than the female. The bengal tiger (Panthera tigris tigris), locally known as Bagh, of the family Felidae, order Carnivora, is the largest living cat on earth. It is regarded as the national animal of Bangladesh. It was once found in all the forests of Bangladesh, but is now confined to the mangrove forests of the Sundarbans in the SW, and is treated as a critically endangered animal.
Invertebrate fauna Of the homopteran insects only about 30 aphid species under 20 genera have so far been listed in the country. This group is of major economic importance both for the direct damage they cause to crops and for the viral diseases they transmit. Winged adults are dispersed by wind currents. Many other homopteran and hemipteran insects have been recorded from Bangladesh.
Bees are hymenopteran insects, characterized by many branched hairs on the body. The group contains both solitary and social forms, but all feed on nectar and pollen. There are about 20,000 species of bees under 19 families worldwide. In Bangladesh 18 species have so far been reported, of which 4 are honey bees: Apis cerana indica, A. dorsata, A. florea, and A. mellifera, and 2 are bumlebees: Bombus. eximius, reported from Sylhet and B. montivagus, reported from the Chittagong Hill Tracts.
Beetles are the insects belonging to the order Coleoptera. In terms of number of species, Coleoptera is the largest order in the animal and plant kingdoms. The order contains some of the largest insects (eg Goliath and Hercules beetles, over 15 cm in length), as well as some of the smallest (ptiliid beetles less than 0.5 mm in length). The different groups of beetles are named as bark beetle, bombardier beetle, cardinal beetle, carrion beetle, chick beetle, deathwatch beetle, dermestid beetle, diving beetle, firefly, ground beetle, ladybird beetle, leaf beetle, long-horned beetle, rove beetle, scarabaeid beetle, tenebrionid beetle, weevil, whirligig, woodworm, etc.
About 35 species under 8 genera of scarab dung beetle fauna have so far been reported from Bangladesh, mostly of genus Onthophagous. About 30 species of leaf-eating scarabeids have also been recorded from Bangladesh. Over 4200 species of ladybird beetles under 490 genera have been described worldwide. About 80 species of beneficial ladybirds, and about 13 species of phytophagous ladybirds have so far been reported from Bangladesh. Some common genera in the crop fields of Bangladesh are Micraspis, Coccinella, Harmonia, Menochilus, Cheilomenes, Propylea, and Brumus. firefly is a small, nocturnal, luminescent, carnivorous beetle of the family Lampyridae, order Coleoptera. There are about 2000 species of firefly worldwide belonging to 100 genera and seven subfamilies; about 280 species occur in Asia. In Bangladesh about 20 species have been reported including Lamprophorus tenebrous, Lampyris marginella, Luciola chinensis, and L. ovalis.
fly is a common term applied to numerous flying insects. More specifically, however, the name is given to the 'true' flies of the order Diptera. Worldwide there are over 85,000 described species of dipterans. In Bangladesh the common indoor fly species are the house fly (Musca domestica), the lesser house fly (Fannia canicularis), the biting house fly or stable fly (Stomoxys), the blue bottles or blow flies (Calliphora), the green bottles (Lucilia), and the flesh flies (Sarcophaga). Outdoor flies include the black flies, the deer flies, the horse flies, the hover flies, the daddy long legs or crane flies and many muscoids. The sand flies (Phlebotomus) are common both indoors and outdoors. So far 5 species of fruit flies have been recognized: (i) Dacus (Zeugodacus) cucurbitae, (ii) D. (Z.) tau, (iii) D. (Hemigymnodacus) diversus, (iv) D. (Bactrocera) dorsalis, and (v) D. (B.) zonatus.
mosquito is a blood sucking insect belonging to the order Diptera, family Culicidae. Important genera are Anopheles, Culex, Aedes, Mansonia, Psorophora, and Haemagogus. Only the female mosquitoes suck blood from different vertebrate hosts, since a blood meal is essential before laying eggs. Males suck plant juices. Over 1600 species of mosquitoes are known worldwide; 113 species have so far been recorded from Bangladesh. An. dirus, An. philippinensis, An. minimus, and An. sundaicus are the malaria vectors. Filariasis is transmitted by Culex quinquefasciatus and Mansonia sp.); Aedes aegypti and Ae. albopictus are responsible for spreading Dengue; Japanese Encephalitis is transmitted by Cx. tritaeniorhynchus.
Spiders are members of the order Araneae, class Arachnida, having four pairs of legs, a large abdomen, and a combined head and thorax. Most of the spiders are terrestrial and predatory in habit. Worldwide about 37,296 species of spiders have so far been recorded in 3,450 genera, and 106 families. In Bangladesh more than 400 species of spiders have been recorded in 134 genera, and 22 families. Most of the Bangladesh spiders belong to Araneidae (90) and Salticidae (83), followed by Thomisidae (48), Theridiidae (36), Tetragnathidae (35), Clubionidae (22), Lycosidae (19) and Oxyopidae (18).
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Crustaceans are predominantly aquatic; a few live in moist places on land, and a few are parasitic. The class Crustacea includes the crabs, shrimps, lobsters, barnacles, water fleas, fish lice, hermit crabs, sow bugs, and pill-bugs. Crustacea comprises some 42,000 species. Many commercially important fresh and marine-water crabs, shrimps and lobsters are abundantly found in Bangladesh. Of the four species of freshwater and 11 species of marine crabs recorded from Bangladesh, the most commercially exploited species of the coastal area is Scylla serrata (mud crab). Neptunus pelagicus, N. sanguinolentus, and Gelasimus annulipes are also commercially important marine crabs. Of the four species of freshwater crabs Paratelphusa lamelliforns is used as food. There are about 10 species of freshwater shrimps/prawns and 19 species of marine shrimps in Bangladesh. The freshwater species, Macrobrachium rosenbergii is commercially important. Six penaeid species viz, Penaeus merguiensis (banana shrimp), P. monodon (tiger shrimp), P. indicus (white shrimp),' P. semisulcatus (green tiger shrimp), Metapenaeus monoceros (brown shrimp), and M. brevicornis are of commercial importance. Six species of lobsters are found to occur in the bay of bengal: Panulirus polyphagus and Thenus orientalis are the two most commercially important species.
Daphnia, Cypris and several copepods are important zooplankters in the freshwaters, and are the food of many fish and other crustaceans. The parasitic fish lice Argulus infests a wide variety of freshwater fishes. Of the marine zooplankters about 20 species of copepods are predominant.
Crabs have a reduced abdomen concealed beneath a short broad cephalothorax, and the first pair of limbs is modified as pincers. There are more than 4500 species of decapod crustaceans worldwide. There are about 16 species of crabs so far reported from Bangladesh waters, of which some species are commercially important.
Echinoderms are marine invertebrates of the phylum Echinodermata. The phylum comprises about 6000 species including starfishes or sea stars, sea urchins, sand dollars, sea cucumbers, brittlestars, sea lilies and feather stars, characterized by a pentamerous body, radial symmetry and a water-vascular system. The taxonomy of the echinoderms is poorly studied in the Indian subcontinent including Bangladesh. Two species of starfishes have been reported from Bangladesh. Many members of sand dollars, sea cucumbers, and sea-urchins are found in good numbers in the coastal belt of Bangladesh.
Vertebrate fauna It includes the animals with a backbone ie the fishes, amphibians, reptiles, birds, and mammals. Today some 22,000 species of fishes, 5,000 amphibians, 7,400 reptiles, 9,000 birds and 4,500 mammals are known worldwide. Bangladesh also possesses a rich diversity in vertebrate fauna, specially in the forested and wetland areas. The country has about 1600 species of vertebrate fauna (Table), of them 653 are fishes: 251 inland and 402 marine; 34 amphibians; 154 reptiles; 620 birds and 113 mammals: 110 inland and 3 marine.
The country has lost more than a dozen vertebrate fauna during the last century. The IUCN-Bangladesh (2000) reviewed the status of the vertebrate fauna. It is reported that 54 inland fishes, 8 amphibians, 58 inland reptiles, 41 resident birds, and 40 inland mammals have come under different categories of threats. A large number (n = 323) remained as data deficient, which could not be evaluated due to paucity of data.
Table Vertebrate fauna of Bangladesh.
| Group | Total no. of living species | Total |
| Fishes | 251 (fresh-water and brackish water) 402 (marine) | 653 |
| Amphibians | 34 (inland) - | 34 |
| Reptiles | 109 (inland) 17 (marine) | 126 |
| Birds | 301 (resident) 176 (migratory) | 477 |
| Mammals | 110 (inland) 3 (marine) | 113 |
| Total | 805 598 | 1403 |
Fishes There are about 22,000 species of fishes worldwide, in about 450 families. Almost 40% of the species live in fresh water. In Bangladesh there are 402 species of marine fishes, Of these species, 56 are cartilaginous fishes (class Chondrichthyes), in 3 orders and 15 families; and rest are bony fishes (class Osteichthyes). There are 251 species of inland fishes (in freshwaters and brackish waters).
Among the inland fishes, the family Cyprinidae (order Cypriniformes) includes the largest number of species: 57 species under 23 genera; these include carps (Rui, Catla, Mrigel, Kalibaus, etc); barbs (Punti, Mahashol, etc); and minnows (Darkina, Chela, Mola, etc). About 55 species of catfishes (Tengra, Air, Shingi, Magur, etc), are found in the freshwaters of Bangladesh. Loaches (Rani, Gutum, Puiya, Panga, etc) are the least explored fish species (about 11 species). Once abundant in the wetlands, the snakehead fishes (Shol, Taki, Gajar etc) are now becoming rare. Of the five species of the family Channidae three are threatened: the Barca snakehead (Pipla shol), Channa barca, is critically endangered, the Giant snakehead (Gajar), Channa marulius, is endangered, and the Asiatic snake-head (Telo Taki), Channa orientalis, is vulnerable. Of the eels (usually with two lateral gill-openings), the Gangetic Mudeel (kuicha), Monopterus cuchia, is unique in possessing a single gill-opening on the ventral side. Once abundant, the species is now a vulnerable species. Another beautiful eel, the one-stripe spinyeel (Tara Baim), Macrognathus aral, is also now vulnerable. The snake-eels (2 species), Pisodonophis species., are not usually eaten by the local people, and face no threats at the moment. The largest eel is the Indian Longfin Eel (Bamosh/ Bamchara/Bao Baim/Telkoma), Anguilla bengalensis, found in the estuaries and freshwaters. Of the gars or crocodile fishes (Kaikka, Kumerir Khil), the Deocata Pipefish, Microphis deocata, is now endangered.
Some 76 species of fishes are often included both as freshwater and marine in Bangladesh. The most important (culturally and economically) is the Hilsa (Ilish), Tenualosa ilisha. It is the largest single species fishery from the major rivers, and currently the hilsa fishery contributes significantly to production from inland sources. Carps are the major fishes in pond culture. The most preferred fish (because of its taste) in Bangladesh is the Climbing Perch (Koi), Anabas testudineus (family Anabantidae, order Perciformes). Although most of the perciforms are marine, the majority enter the estuaries and rivers, such as Pony fishes (Tak-chama), Jew fishes (Poa), thread-fins (Tapasi), mullets (Bata), pomfrets (Rupchanda), etc.
Amphibians There are about 5000 species of amphibians worldwide. Frogs and toads alone are included in 28 families, 338 genera and about 4360 species, which have the widest distribution, especially the members of the family Ranidae. In Bangladesh the class Amphibia is represented only by the members of the order Anura (frogs and toads).
The order Gymnophiona (caecilians; 5 families, 34 genera, 156 species) and the order Caudata (salamanders and newts; 10 families, 63 genera, 440 species) have no representatives in Bangladesh. The country has 34 species of amphibians of which 8 are listed as threatened. The country earned about US $ 26 million by exporting bullfrog legs (Hoplobatrachus tigerinus) during 1988-1993. Frog leg export is now banned.
Reptiles Cold-blooded vertebrates of the class Reptilia, comprising the turtles and tortoises, lizards, worm lizards, snakes, crocodilians, and the tuatara; primarily tetrapod (4-legged), but the legs are lost in snakes and in some lizards. Dinosaurs are also reptiles that dominated the land for more than 100 million years, until their extinction about 65 million years ago.
Other major groups of reptiles, about 7,400 species, have survived until today. More than half the number (about 4,300 species) consists of lizard species. The total number of reptile species in Bangladesh is 154. Of the inland reptiles 2 are crocodilians. The marsh crocodile (Crocodylus palustris) is no longer found in the wild. Among the inland reptiles 58 face different categories of threats: 12 (2 crocodilians, 7 turtles and tortoises, 1 lizard, and 2 snakes) are critically endangered, 24 (11 turtles and tortoises, 2 lizards and 11 snakes) are endangered, and 22 (2 turtles and tortoises, 5 lizards, and 15 snakes) are vulnerable. The status of the marine reptiles could not be evaluated locally due to paucity of data. However, all the 5 species that are found in Bangladesh waters are globally threatened: the Hawksbill Turtle Eretmochelys imbricata is critically endangered; and the Loggerhead Turtle Caretta carett, Green Turtle Chelonia mydas, Olive Ridley Turtle Lepidochelys olivacea, and Leatherback Turtle Dermochelys coriacea are endangered.
Turtle and tortoise The order Testudines is divided into 12 families and comprises about 250 species and 90 genera of turtles and tortoises distributed worldwide in tropical and temperate zones. In Bangladesh turtles and tortoises (order Testudines) are divided into 5 families (3 inland and 2 marine) with 27 species (22 inland and 5 marine).
Of the 22 inland species, 20 face different categories of threats. Seven are critically endangered, 11 endangered, and 2 vulnerable. The status of the remaining two could not be assessed due to paucity of data. The critically endangered species are Bora Kaitta, River Terrapin (Batagur baska); Dhoor Kasim, Three-striped Roof Turtle, (Kachuga dhongoka); Halud Pahari Kasim, Elongated Tortoise (Indotestudo elongata); Pahari Kasim, Asian Giant Tortoise (Manouria emys); Bostami Kasim, Bostami Turtle/Black Soft Shell Turtle (Aspideretes nigricans); Sim Kasim, Asiatic Soft Shell Turtle/Narrowheaded Soft Shell Turtle (Chitra indica); and Jata Kasim, Bibron's Soft Shell Turtle (Pelochelys bibroni).
Lizards About 4,300 species of lizards belong to 420 genera and 26 families occur worldwide. In Bangladesh the lizards (order Lacertilia) are divided into 4 families (Gekkonidae, Agamidae, Scincidae and Varanidae) with 18 species (all inland). Of the 18 species, 8 face different categories of threats. One (Flying Lizard/ Draco Draco blanfordii) is critically endangered, 2 (Ram Godi/kalo Gui, Ring Lizard/ Monitor Lizard/Two-banded Monitor Varanus salvator, and Gui/Sona Gui /Holdey Shap, Yellow Monitor/Common Lizard Varanus flavescens) are endangered, and 5 are vulnerable.
Snakes About 2,700 species, of snakes belonging to about 450 genera and 18 families, occur worldwide, mostly in the tropics. In Bangladesh the 79 (inland: 67, marine: 12) species of snakes (order Serpentes) are divided into 7 families (6 inland and 1 marine). Of the 67 inland species 15 are venomous, belonging to the Elapidae (10 species) and Viperidae (5 species); all marine species are venomous. In Bangladesh the critically endangered snakes are Golbahar/Ajagar, Reticulated Python Python reticulata, and Chandrobora, Russell's Viper Vipera russellii. Eleven species are endangered, and 15 are vulnerable.
Crocodile and Gharial These carnivorous reptiles belong to the order Crocodilia. The order has 3 families; Crocodylidae: crocodiles, 13 species; Alligatoridae: alligators, 2 species, and caymans 5 species; and Gavialidae: gharials, 2 species found in tropical and subtropical regions. Bangladesh has 1 species of crocodile (one is no longer in the wild) and one species of gharial.
The largest of all crocodiles is the saltwater crocodile, Crocodylus porosus, found in the Sundarbans. The marsh crocodile, or mugger (C. palustris), is a freshwater species of India and Sri Lanka. In Bangladesh the species no longer exists in the wild; however, a few (4/5) are still surviving in a pond near the shrine of the saint Khan Jahan Ali in a southern district, Bagherhat.
The family Gavialidae contains two species of extremely thin-snouted crocodilians. Bangladesh has one species, the gharial (Gavialis gangeticus). It occurs in the northern part of Bangladesh in the river padma.
Birds Belong to the class Aves, and consist of approximately 10,000 species, grouped into 24 orders. The order Passeriformes (known as passerines or songbirds) contains more than half of the known bird species. The remaining orders are known collectively as non-passerines. Over 1200 bird species occur in the Indian region. Bangladesh has 620 species of birds of which 301 are resident and 319 are migratory. Sarus Crane (Grus antigone) is the largest (standing about 1.75 m) bird in the subcontinent, but it is now rare in Bangladesh. A few flowerpeckers and sunbirds, smaller than the sparrow, are perhaps the smallest. The bird population in Bangladesh is shrinking fast. Today about 41 species are threatened in Bangladesh, of which 19 are critically endangered, 18 endangered and 4 are vulnerable. The Pinheaded Duck (Rhodonessa caryophyllacea), the Nukta or Comb Duck (Sarkidiornis melanotos), the Common Peafowl (Pavo cristatus), and the Burmese Peafowl (P. muticus) which were more or less widely distributed until 70 or 80 years ago, have virtually disappeared from Bangladesh.
Mammals Members of the class Mammalia, including humans. Today there are some 4,500 species of mammals worldwide, of which roughly a tenth occur within the Indian subcontinent. In Bangladesh there are 121 species of mammals. They range in size from tiny shrews and pipistrelle bats, which weigh only a few grams, and measure a few centimetres, to elephants that stand over 3 metres at the shoulder and can weigh over 4 metric tons.
The largest mammal, the Blue Whale, is nearly 30 metres in length and weighs up to 150 metric tons. Of the inland mammals, 40 have come under different categories of threats: 21 critically endangered, 13 endangered, and 6 vulnerable; 53 species could not be evaluated due to paucity of data. [Md Anwarul Islam]
