The intertidal polychaete (Annelida) fauna of the Sitakunda coast (Chittagong, Bangladesh), with notes on the Capitellidae, Glyceridae, Lumbrineridae, Nephtyidae, Nereididae and Phyllodocidae of the “Northern Bay of Bengal Ecoregion”

Abstract Of seven species of polychaetous annelids collected from the intertidal zone of Sitakunda coast, Chittagong, Bangladesh, five were new records for the country. The seven are listed, with brief notes on these, some previously recorded! species and others housed in the collections of the Natural History Museum, London. Keys are given to the recorded species of Phyllodocidae, Nereididae, Lumbrineridae, Nephtyidae and Capitellidae of the “Northern Bay of Bengal Ecoregion”, and to the recognised species of Glyceridae from the Bay of Bengal. The worms in this Ecoregion are subject to the outflows of the Irrawaddy, Ganges, Hooghly and Mahanadi Rivers, and many of them are known to be freshwater tolerant.


Introduction
There has long been an emphasis on taxonomy in marine studies, for example Hedgpeth (1957) recommends that the first procedure in any ecological works or applied research with organisms is the exercise of systematics. No ecological investigation can be successfully carried out without a comprehensive knowledge of the taxonomy of faunal resources.
Polychaete annelids are a major group within the soft bottom macro-invertebrates (Gray and Elliott 2009) and comprise a diverse, abundant and ecologically significant functional component of the coastal ecosystem (Misra 1999). These worms are pivotal parts of food webs and form the central link between the sediment systems and higher predators. They are often diverse and highly abundant, especially in areas of anthropogenic stress (Gray and Elliott 2009) and they have diverse feeding strategies (Fauchald and Jumars 1979).
The polychaete fauna of Bangladesh is little studied, despite the importance of marine resources to the country. The largest identification works for the littoral and shallow-water polychaetes of the Indian Ocean area are Fauvel (1953) for the Persian Gulf to Myanmar and Day (1967) for southern Africa. Hartman (1974aHartman ( , 1974b) is more concerned with deep water polychaetes. There have been many smaller publications on the polychaetes of India, Thailand and Ceylon/Sri Lanka since Fauvel (1953), but only a few for Bangladesh (Mahmood et al. 1993, Belaluzzaman 1995, Alam et al. 1996, Das and Reynolds 2003, Pramanik et al. 2009) and even fewer for Myanmar (one new species each in Kirtley 1994 andGlasby 1999, one re-described species in Böggemann 2002). The most relevant recent publications are probably Misra (1999) and Pramanik et al. (2009).
The present study therefore aims to provide further information on the taxonomy of polychaetes in Bangladesh waters at two sites on the Sitakunda Upazila coast, north of the city of Chittagong (see Table 1), one of which is affected by ship-breaking activity on the shore.
The "Northern Bay of Bengal Ecoregion" of the "Bay of Bengal Province" of the "Western Indo-Pacific Realm" was devised by Spalding et al.,2007, and it is shown in map form in Claus et al (2014). The ecoregion extends from between Ye and Dawei (14.61°N,97.90°E) in Myanmar/Burma to near Konark (19.87°N 86.11°E) in Odisha/Orissa, India (Fig. 1), and reaches from the coastline to 370km offshore (or the 200m isobath if this is further offshore). It thus includes the Gulf of Martaban, the mouths of the Irrawaddy, Ganges and Hooghly Rivers, and most of the mouths of the Mahanadi River (one distributary leads to the Chilika Lake, usually referred to as Chilka Lake, which has its outlet to the sea in the neighbouring "Eastern India Ecoregion" of the "Bay of Bengal Province"). Southern Myanmar is in the "Andaman Sea Coral Coast Ecoregion" of the "Andaman Province".
In this paper, the new specimens from Bangladesh are compared with the same families of polychaetes reported from the "Northern Bay of Bengal Ecoregion", including the entire coast of Myanmar and the entire Odisha coast (to include the freshwater polychaetes of Chilka Lake). Important localities are shown in Figure 1.

Methods
Quantitative samples were collected between April 2007 and November 2008, but the present paper only deals with the taxonomic details of polychaetes collected at those sites. Samples were collected from the intertidal zone by using a hand-held corer with a depth penetration of 15 cm. The collected samples were washed through a 0.5 mm mesh hand sieve with filtered water at the collection point to separate animals from sediment. The materials retained on the sieve were placed in plastic vials to which 5% formalin was added for fixing the organisms, and labelled. The vital stain Rose Bengal was added to the vials to help in sorting the organisms from debris. In the laboratory the materials were poured into a round transparent Petri dish and separated from debris using needle, brush and magnifying glass. Then the organisms were preserved in 75% ethyl alcohol for identification. An Olympus compound microscope with video facility was used and relevant keys (Fauvel 1953, Day 1967 were followed for preliminary identification. Identification to species necessitated the use of many other papers, which are mentioned later in this publication.
Because there are so few records from Myanmar, some specimens deposited in the Natural History Museum, London, by Professors G.E. Gates (Judson College, Rangoon) and F.J. Meggitt (University College, Rangoon) between 1931 and 1938, and only partially published by C.C.A. Monro (1931Monro ( , 1937, have been re-studied. Identification keys are given in this paper, but any identifications made using them should be checked against good descriptions or reliably identified specimens, because not only may new records or even new species be found, but some of the older reports cited here may have been mis-identifications or represent cryptic species (it is interesting that the type locality of Capitella capitata is West Greenland (Blake 2009), and for Glycera alba is Norway (Böggemann 2002)).

Annelida
The taxonomy and systematics of the Annelida have been rapidly changing in recent years. It must be recognised that the classifications used in publications such as Fauvel (1953) and Day (1967) are now very dated. The fauna given in Fauvel (1953) shares many species with his earlier work on the fauna of France (Fauvel 1923(Fauvel , 1927, but it is not now considered likely that so many species from northern Europe would also be found in the Indian Ocean. A more modern classification (although still on classical lines) can be found in Chambers and Muir (1997). More strictly phylogenetic classifications are also available, such as Rouse (2000) and Appeltans et al. (2010). Keys to identify polychaetes to family level can be found in publications such as Fauchald (1977), Chambers and Muir (1997) and Glasby and Fauchald (2000).
Polychaetous annelids are often regarded as a marine group (albeit with some freshwater tolerant species), but it should be noted that non-marine species also exist (see Glasby et al. 2009), including some from Bangladesh (Das and Reynolds 2003 list two species of Aeolosoma).

Phyllodocidae
Eteone cf. delta Wu & Chen, 1963 One specimen was found: length 15 mm, width 0.75 mm for 92 segments, but anal cirri missing. Anteriorly the height of the segments is 1mm, but posteriorly the body becomes dorso-ventrally flattened. This specimen has two pairs of tentacular cirri on the first segment, the dorsal being shorter than the ventral ones (they are both, however, small and difficult to see). The first chaetae are on the second segment. The pharynx is everted, showing a smooth surface and a ring of 12 large subglobular papillae around the opening (Fig. 2). The dorsal cirri are small and rounded, compressed against the side of the body. The ventral cirri, distally rounded, are almost as long as the chaetal lobe anteriorly, but slightly longer posteriorly. The tip of the acicula is just emergent from the chaetal lobe in the anterior part of the body, but in the posterior part of the body is much more protuberant. The specimen is colourless in alcohol except for some brown markings dorsally by the pygidium.
This specimen, especially the structure of the pharynx, displays similarities to Eteone delta Wu & Chen, 1963, which is known from the Yangtze delta, the Pearl River and Zhangjiang estuary, China (Shen andQi 1982, Chen et al. 2012). There are, however, differences such as the presence of emergent acicula. It is not considered advisable to describe this specimen as a species new to science, partly because there is only one specimen and partly because that specimen is incomplete (the shape of the anal cirri is important at the generic level for this group). It may be that this is a rare species which shows some morphological variation from one extreme of its geographic range to the other. Glasby et al. (2009) list Eteone delta as freshwater tolerant, found in the Palaearctic and Oriental regions inhabiting lake/river freshwater and estuary and coastal lagoons (fresh-brackish) including supra-littoral areas. Shen and Qi (1982) say it is "favored in normal or rich trophic waters", as opposed to over-trophic or polluted waters. This is a new record for Bangladesh, no members of the family Phyllodocidae being recorded by Pramanik et al. (2009).

Discussion of Northern Bay of Bengal Phyllodocidae
Two specimens from Maungmagaun, Myanmar, in the Natural History Museum, London, (NHMUK ANEA 1935.1.31.34 andNHMUK ANEA 1937.1.4.4) have been identified as Phyllodoce castanea by C.C.A. Monro. On both of these specimens many of the head appendages are missing or regenerating, but the identifications are probably correct. The species is now known as Nereiphylla castanea (see synonymy in Alós et al. 2004). Fauvel (1932) records Phyllodoce madeirensis and Eulalia (Pterocirrus) magalhaensis from a depth of 2 fathoms (3.658 m) in the Mergui Archipelago.
Two species of Eteone are recorded from West Bengal (Misra 1999, Das et al. 2009. Eteone barantollae Fauvel, 1932, is now regarded as a member of the genus Hypereteone (see Wilson 1988). Eteone ornata Grube, 1878, has been referred to the genus Mysta, but may be a misidentification (Uschakov, in Wilson 1988).
In Odisha, Anaitides madeirensis, Eteone (Mysta) ornata and Eteone barantollae have been recorded from estuaries by Misra (1999) and . Anaitides madeirensis is now generally referred to as Phyllodoce madeirensis, and has a very wide distribution in temperate and tropical waters (Alós 2004).
These species from northern Bay of Bengal waters can be keyed out as follows, but any identifications must be checked against reliable descriptions as many other species are known from the Indo-Pacific area. The pharynx is often not everted in preserved material, but the jaws and any paragnaths/ papillae present may be seen by making a mid-ventral cut backwards from the mouth, cutting through the ventral surface of the pharynx as well as the body wall for several segments, and folding the resulting flaps to the side to reveal the complete jaw apparatus.
Neanthes chingrighattensis (Fauvel, 1932) One specimen was found. This species could be regarded as a typical nereidid, having paragnaths on the pharynx and four pairs of tentacular cirri (Fig. 3). The arrangement of the paragnaths agrees with that depicted by Fauvel (1953). Falcigerous chaetae are entirely absent in this species. It is a new record for Bangladesh according to Pramanik et al. (2009). The type locality is Kolkata, West Bengal, and Misra (1999) states that the species is endemic in Indian waters.

Lycastonereis indica Rao, 1981
This species has no paragnaths on the pharynx and only three pairs of tentacular cirri (Fig. 4). It is, however, not a member of the genus Namanereis because it has parapodia with two distinct branches (notopodium and neuropodium) each with chaetae.

Discussion of Northern Bay of Bengal Nereididae
Many of these species have had their names changed for taxonomic reasons, or are otherwise worthy of comment.
The genus Ceratonereis has been revised by Hartmann-Schröder (1985), who places the species Ceratonereis burmensis in the subgenus Composetia. Composetia has now been raised to generic level, but more work is needed on this grouping (Bakken and Wilson 2005).
Leonnates jousseamei has been synonymised with L. indicus by Qiu and Qian (2000), who also correct L. persica to L. persicus. Glasby (1999) states that Namanereis quadraticeps is restricted to the Subantarctic and temperate shores of the Southern hemisphere, and Glasby et al. (2009) refer it to the Namanereis quadraticeps (Blanchard in Gay, 1849) species group. Glasby (1999) accepts Lycastis indica as a member of the genus Namalycastis, and also places Namalycastis meraukensis in the Namalycastis abiuma (Grube, 1872) species group.
Nereis falcaria was reduced to a subspecies of Nereis jacksoni by Hartmann-Schröder (1974) but the two species were separated again by , see Wu et al. 1985. Wilson (1984) accepts Nereis caudata as a member of the genus Neanthes. Most members of the genera Neanthes and Nereis need to have their type specimens compared with the descriptions in Bakken and Wilson (2005) before their generic placement can be confirmed.
Perinereis nuntia has been studied by Glasby and Hsieh (2006), Wilson and Glasby (1993) and Yousefi et al. (2011), and as Alam et al. (1996) did not give a full description of their specimens, it would be better to refer them to the Perinereis nuntia (Savigny, 1818) species group. The specimen 1937.1.4.43-44 from Maungmagaun, Myanmar, has been studied and identified as P. nuntia as defined by Glasby and Hsieh (2006). Perinereis helleri was kept separate from Perinereis cultrifera by Hutchings et al. (1991), but was synonymised with it by Khlebovich (1996). Problems with species of Perinereis were also discussed by Muir and Bamber (2008).
The very similar species Pseudonereis trimaculata and Pseudonereis variegata have been kept separate by Bakken (2007) and Villalobos-Guerrero and Tovar-Hernández (2013). Most characters seem to overlap completely, but in P. trimaculata the dorsal cirrus, rather being sub-terminal, is attached to the notopodium terminally from about chaetiger 40, and the ventral ligule of the neuropodium is 0.5-0.8 times as long as the acicular ligule in anterior chaetigers. In P. variegata only the last few dorsal cirri are attached terminally, and the ventral ligule of the neuropodium is as long as the acicular ligule in anterior chaetigers (it is as long as the acicular ligule in posterior chaetigers in both species). It is not surprising, therefore, that Monro labelled sample 1932.11.25.2-3 in the NHM as Pseudonereis trimaculata = variegata. The four samples from Myanmar have now been re-examined, and while some are definitely P. trimaculata, others have the longer ventral ligule of the neuropodium in anterior chaetigers of P. variegata while also having the dorsal cirrus attached to the notopodium terminally in the last quarter of the body. We are treating all the Myanmar specimens as P. trimaculata, but mentioning both species in the key.
The relevant species mentioned above can be keyed out as follows, but any identifications must be checked against reliable descriptions as many other species are known from the Bay of Bengal and other Indo-Pacific areas.

Lumbrineridae
The Lumbrineridae used to be regarded as part of the family Eunicidae (e.g. Fauvel (1953), Day (1967)), but is now regarded as a separate family alongside the Eunicidae and various others in the Order Eunicida (see George and Hartmann-Schröder (1985), Carrera-Parra (2006a)). The pharynx is usually not everted in preserved material, but the maxillae may be seen by making a lateral cut (not a mid-ventral cut as used for nereidids) backwards from the side of the mouth, cutting through the side of the pharynx as well as the body wall for several segments, and folding the resulting flap to the side to reveal the complete jaw apparatus. If it is necessary to dissect the pharynx in this way, the anterior chaetae should be studied first.

Gesaneris malayensis (Rullier, 1969)
Six specimens of this species (Fig. 5) were found. The species, originally published as Lumbriconereis malayensis, was redescribed by Carrera-Parra (2006a) and transferred to a new genus. It is a new record for Bangladesh according to Pramanik et al. (2009). It is very similar to the description of Eranno papillifera (Fauvel, 1918) by Oug (2002). This latter species was also first published as a Lumbriconereis species. The most important difference is that in Gesaneris the maxillary apparatus has four pairs of maxillae, whereas in Eranno there are five pairs of maxillae.
The collections of the Natural History Museum, London, contain a previously unpublished specimen (NHMUK ANEA 1937.3.10.15) collected by Prof. F.J. Meggitt at Maungmagaun, Myanmar, which can be identified using the key in Fauvel (1953) as Lumbriconereis sphaerocephala. This species has not been re-studied by recent taxonomists but it is similar to Lumbrineris inflata Moore, 1911 (see Carrera-Parra 2006b). Das et al. (2009) record Lumbrineris heteropoda, L. polydesma and L. notocirrata from West Bengal.
In Odisha, the species Lumbrineris heteropoda, Lumbrineris notocirrata and Lumbrineris polydesma have been recorded from coasts and estuaries, while Lumbrineris polydesma and L. simplex were found in Chilka Lake (Misra 1999, Rao 1995. Lumbrineris heteropoda has been transferred to the genus Kuwaita by Carrera-Parra and Orensanz (2002) and to the genus Scoletoma by Budaeva (2005). The species appears to have a wide geographic range (Sea of Okhotsk to Red Sea) and may well be sub-divided after further study, but for the moment we shall accept the name Kuwaita heteropoda, as Carrera-Parra and Orensanz (2002) studied a specimen from Japan, the type locality.
Lumbrineris tetraura is accepted as a member of the genus Lumbrineris by e.g. George and Hartmann-Schröder (1985) who say it is a cosmopolitan species, but Diaz-Castaneda and Rodriguez-Villanueva(1998), place it in the genus Scoletoma, the members of which only have simple hooded hooks, whereas Lumbrineris species possess both simple and composite hooded hooks. Lumbrineris polydesma may also be better placed in the genus Scoletoma, but it is not formally transferred here because the type specimens have not been studied.
Lumbrineris simplex, having no hooked chaetae and no antennae, is better placed in the genus Arabellonereis.
Lumbrineris notocirrata has been transferred to the genus Ninoe by Fauchald (1970), because of the presence of small branchiae.
The species Lumbriconereis pseudobifilaris Fauvel, 1932, has been recorded from 250 fathoms (about 450 m) depth off Akyab, Myanmar (Fauvel 1932), and from a sewage-fed fish culture pond near Calcutta, West Bengal, India (Mitra and Roy 2010). This species has no hooked chaetae but it does have two very long maxillary carriers. It is not included in the key because these characters make it a member of the family Oenonidae.
Lumbrinereis and Lumbriconereis are incorrect spellings of the generic name Lumbrineris. The northern Bay of Bengal ecoregion species of Lumbrineridae can be keyed out as follows, but any identifications must be checked against reliable descriptions as many other species are known from the Bay of Bengal and other Indo-Pacific areas.

Glyceridae
A posterior fragment of a glycerid was found in this collection, but it is unidentifiable to species. It is, however, a new record for Bangladesh because the fragment appears to bear branchiae on the parapodia, whereas Glycera lancadivae Schmarda, 1861, the only species in Pramanik et al. (2009), does not. Böggemann (2002) says that Glycera lancadivae is a nomen dubium, but similar to Glycera brevicirris (known from Sri Lanka and the Andaman Sea) and Glycera tesselata (nearest known localities Xisha Islands and Madagascar). The collections of the Natural History Museum, London, contain a specimen of Glycera cinnamomea (NHMUK ANEA 1938.5.7.45) which was collected from Investigator station 549, at a depth of 24 fms (43.89 m), off Mergui Harbour (= Myeik, near the mouth of the Tanintharyi river, Myanmar), identified by Böggemann (2002). Fauvel (1932) records Glycera cirrata (from off Tenasserim, Burma, 50 fathoms (91.44 m)). Böggemann (2002) says this species is mixture of Glycera brevicirris (known from Sri Lanka and the Andaman Sea) and Glycera americana (nearest known localities on the coasts of South America). Das et al. 2009 record Glycera convoluta and G. rouxii from West Bengal. Glycera convoluta, Glycera lancadivae, Glycera longipinnis, Glycera rouxii, and Glycera tesselata have been reported by Misra (1999) and  from the coasts and estuaries of Odisha. According to the major revision by Böggemann (2002), G. convoluta is probably a junior synonym of G. tridactyla, G. lancadivae is a nomen dubium, G. longipinnis is a junior synonym of G. sphyrabrancha, G. rouxii is probably a junior synonym of G. unicornis, and G. tesselata is a good species. Glycinde oligodon Southern, 1921, has also been reported from the Chilka Lake, Odisha, as a glycerid by Rao (1995), but this species belongs to the family Goniadidae. Böggemann (2002) accepts 14 species of glycerid from the Bay of Bengal area. The following key to these 14 species plus G. tesselata and G. unicornis (not previously recorded from the Bay of Bengal) is derived from Böggemann (2002), which contains full descriptions of these and many other species from the Indo-Pacific region. In mid-body and posterior parapodia neuropodial postchaetal lobes more or less rounded. The single 6.5 mm long worm found (Fig. 6) is probably this species, which has been well described by Imajima (1987) under the name Nephtys oligobranchia. The species has been transferred to the genus Micronephthys by Dnestrovskaya and Jirkov (2010), although they say the family needs to be fully reviewed. Glasby et al. (2009) list N. oligobranchia as a freshwater-and saltwater-tolerant species, found in the Palaearctic and Oriental regions inhabiting lake/river freshwater, estuary and coastal lagoons (fresh-brackish) including supra-littoral areas and inland lakes. Shen and Qi (1982) say it is "favored in normal or rich trophic waters", as opposed to over-trophic or polluted waters.

Discussion of Northern Bay of Bengal Nephtyidae
Nephtys oligobranchia is the only nephtyid recorded by Pramanik et al. (2009) from Bangladesh. It is also recorded by Fauvel (1932) from Mergui, Myanmar. N. oligobranchia and N. polybranchia Southern, 1921, have both been recorded from West Bengal (Misra 1999) and the Ganges river system (Nesemann et al. 2007). Das et al. (2009) record N. dibranchis and N. oligobranchia. Nephtys dibranchis was placed in the genus Aglaophamus by Hartman (1950).
The northern Bay of Bengal ecoregion species of Nephtyidae can be keyed out as follows, but any identifications must be checked against reliable descriptions as many other species are known from the Bay of Bengal and other Indo-Pacific areas. Specimens of Capitellidae, having no head appendages and usually no obvious parapodial lobes, can easily be mistaken for oligochaetes (e.g. Stephenson 1908Stephenson , 1910. Without studying the reproductive system in detail, the most useful distinguishing character is the presence of hooked chaetae with a terminal hood covering the hook, which are found on the abdomen of capitellids (absent from oligochaetes). Green (2002) gives a key to members of the genus Heteromastus found in the Indian Ocean. Unfortunately, there are variations in the descriptions of Heteromastus filiformis (Claparède, 1864) specimens described by different people. The three specimens found in this collection (Fig. 7), having expanded neuropodial lobes in the posterior abdomen and abdominal hooded hook chaetae with three teeth above the main fang, are more like those described by Day (1967) than those described by Hutchings and Rainer (1981), which had expanded notopodial lobes in the posterior abdomen and abdominal hooded hook chaetae with 11-13 teeth above the main fang. The type locality of H. filiformis is in the Mediterranean (see Green 2002), so Day's specimens from South Africa could be a different species to Claparède's. Glasby et al. (2009) list Heteromastus filiformis as freshwater tolerant, but say that multiple species may have been reported under this name. This is a new record according to Pramanik et al. (2009). Pramanik et al. (2009) give Dasybranchus caducus as the only capitellid species they know from Bangladesh. The Natural History Museum, London, has a specimen of Notomastus near latericeus Sars, 1851 sensu Green 2002(NHMUK ANEA 1933.71) and the type specimens of Parheteromastus tenuis Monro, 1937, from Maungmagaun, Myanmar (NHMUK ANEA 1937.
There follows a key to the reported species of capitellid from the Northern Bay of Bengal ecoregion, but any identifications must be checked against reliable descriptions as many other species are known from the Bay of Bengal and other Indo-Pacific areas. In particular, Green (2002) suggested earlier records of Heteromastus similis may be suspect. Also, as noted above, the type locality of Capitella capitata is West Greenland (Blake 2009). In both these cases further taxonomic work is needed, including the careful study of type specimens and probably comparisons of DNA, to see whether the Bay of Bengal specimens have been misidentified and actually represent new species (see, for example, Blake (2009), Blake et al. (2009), Wu et al. (1991).
Most keys to capitellid genera start with the number of segments in the thorax. There may be a sudden change in size or shape of the segments at the start of the abdomen, but in many cases it is easier to make a temporary whole mount of the specimen and count the segments with capillary chaetae.

General discussion
Of the seven taxa identified above, five are new records for Bangladesh. This shows that the polychaete fauna of Bangladesh is still not well known. Some earlier records of polychaetes will have to be re-studied before the fauna list of the Bangladesh area is complete, as names will change for taxonomic or nomenclatural reasons. An example of this is the genus Talehsapia, reported from the Hooghly estuary and South 24-Parganas, West Bengal by Misra (1999) and . The genus was placed in the new family Talehsapiidae Misra, 1999, but it is now known to fit into the pilargid subfamily Synelminae (see Salazar-Vallejo et al. 2001). More recently, Talehsapia has been synonymised with the genus Hermundura (see Glasby and Hocknull 2010).
It is notable that some species reported from Bangladesh have very wide reported distributions -the same species being reported from both Bangladesh and northern Europe may be the result of misidentification or an unrecognised cryptic species. It is also notable that Ghosh (2014) reports that two polychaete species first found in this ecoregion -Asychis gangeticus Fauvel, 1932 (family Maldanidae; type locality the Gangetic delta) and Pseudopolydora kempi (Southern, 1921) (family Spionidae; type locality a canal at Chingrighatta near Kolkata) -were not found by the Zoological Survey of India between 1984 and 1989, possibly due to the river flow being reduced by dams.
While the surface salinity in the open part of the Bay of Bengal oscillates from 32-34.5‰, in the coastal region it varies from 10-25‰ and at the river mouths the surface salinity decreases to 5‰ or even less (Banglapedia 2010). It is no surprise, therefore, that some of the species in this paper are listed by Glasby et al. (2009) as being freshwater tolerant.
Further work on the occurrance and abundance of the macrobenthic fauna and ecology of the Sitakunda coast, Chittagong, will be published in the future (Hossain and M. Belal in prep.).