Brachyuran Crab Fauna Character Estimated from Marine Water of Bangladesh and Noted New Record (Crustacea: Decapoda) as Distribution

As habitat and distribution, in the study a total of 18 crab species were identified, belonging to 10 families (Calappidae, Epialtidae, Gecarcinidae, Grapsidae, Matutidae, Ocypodidae, Panopeidae, Sesarmidae, Varunidae, and Xanthidae) order Decapoda under subphylum crustacean with relevant distin-guish morphological and meristic character and geographical position. We investigated crab species of Bangladesh from December 2013 to October 2014. All species samples were collected by hand picking on a baseline survey in Saint Martin’s Island (the only coral island of Bangladesh) and adjacent marine water body of Bay of Bengal, Satkhira area (brackish and freshwater) and mangrove forest area (Sundarban). Among 18 species, 10 crab species from Family Epialtidae (1 species), Gecarcinidae (2 species), Ocypodidae (1 species), Panopeidae (1 species), Sesarmidae (1 species) and Xanthidae (4 species) were newly occurred in the Bay of Bengal, Bangladesh. Cardisoma armatum and Zosymus aeneus species were larger than other enlisted species.


Introduction
Intertidal area is an important environment that is challenging for living organisms in Saint Martin Island. Marine organisms are affected by humans because of this area's easy accessibility whereas meeting land and sea [1]. The rocky intertidal area is one of the physically particularly extreme environments around the sea area. Brachyuran crabs belonging to the Order Decapoda are the most diverse animal of crustaceans [2]. In the world, the infra class Brachyura contains about 70 families under Decapoda [3]. In India, a total of 226 species of brachyuran crabs belonging to 130 genera and 39 families reported from different maritime states of the west coast [4]. According to marine species identification portal a total of 1250 species and subspecies of brachyuran crabs recorded from Japan [5]. As aquaculture and traditional food, crab fishery has an important economic value around Asia and in Bangladesh. In the aquatic habitat crustaceans are the most abundant and diverse group. Last decades many researches from different parts of the world focused on taxonomic decapod crustaceans that have enriched crab list and biodiversity [6] [7] [8] but study on crab in marine water very limited research has been done in Bangladesh. This country is a data deficit area in marine crab taxonomic field which leads to limited contribution into the world crab taxonomic and distribution area. Very few researchers have done the taxonomic study on crab [9], freshwater crab in some wetland ecosystem [10], crab in coast and estuary [11] and some marine crab from the Bay of Bengal in Bangladesh [12]. Thus, taxonomic with distribution study has not been widely reported yet from Bay of Bengal marine water. However, the aim of the present investigation is to increase the knowledge on the brachyura fauna family, wise species identification from mainly Bay of Bengal and freshwater of Saint Martin's Island and mangrove forest area in Bangladesh.

Study Area, Sites and Time
In the study, we investigated at five sites of Bangladesh. Selected study area is

Sample Collection and Preservation Procedure
Crab samples were collected by hand picking from beach and fish landing centers, and some were obtained from fishermen. Several samples were collected from fishing nets in shallow coastal areas and the deep sea. The samples were washed with pure water after collecting, preserved and photo session. Photographs of the crabs were taken by Nikon USA D3300 digital SLR Camera before Open Journal of Marine Science their color changed. Fresh specimens were separated and placed in the ice box for preservation. All specimens were carried out to the fisheries Lab, Department of Zoology, Jagannath University. After observations and measurements, specimens were reserved and preserved with 6% -10% formalin in the Zoological Museum of Jagannath University, Dhaka.

Species Measurement, Identification and Analysis
All morphological and meristic characteristics were measured by the digital calipers scale as millimeter (mm) [13]. Species were identified using pictorial, diagnostic characters as well as morphological and meristic characteristics such as color of body part, external features, shape of the carapace, dorsal surface, cheliped and legs, shape of anterolateral margins, antennule and antenna, eye shape, and pereiopod [14]. The following the references for the species identification

Results and Discussion
In the study, a total of 18 crab species recorded belongs to 10 families (Calappidae, Epialtidae, Gecarcinidae, Grapsidae, Matutidae, Ocypodidae, Panopeidae, Sesarmidae, Varunidae, and Xanthidae) order Decapoda under subphylum crustacean. As a result of distribution, nine crab species were recent newly added to the crab list of Bangladesh. Major Morphometric and meristic key of crab species were estimated as millimeter scales that are represented in Table 1 and Table 2, and Figure 2 and Figure 3 for species identification and calculation.

Estimated Weight and Morphometric Character
Among all crab species maximum wet weight was 181.88 g for the crab species Zosymus aeneus. Carapace length and breadth measured as a major identification key that observed maximum length 68 mm and breadth 88 mm in Z. aeneus. Posterior border length: 18 mm; frontal margin length: 18 mm; antennule length: 13 mm; antenna length: 6 mm; eye stalk length: 3 mm; eye diameter: 2 mm (Table 1).

Estimated Cheliped and Pereiopod
Each crab species has two (left and right) cheliped (Table 1). Pereiopod is a key character of the leg of the crab species and it includes six parts that are represented in Figure 2 and Figure 3.
Coxa: Its small segment of the leg that connects to the body. This is the first part of cheliped and pereiopod from the body of crab species. In cheliped, maximum size of coxa was 15 mm (left) and 18 mm (right) recorded whereas in pereiopod coxa average size was 9.25 ± 2.98 mm for Z. aeneus.  Basi-ischium: Its second part that situate between coxa and merus in cheliped and pereiopod of crab species. In cheliped, large size of basi-ischium was 18 mm (left) and 16 mm (right) whereas in pereiopod average size was 14.25 ± 2.87 mm present in C. armatum.
Merus: Its third part that situate between basi-ischium and carpus in cheliped and pereiopod of crab species. In cheliped, maximum size of merus is 37 mm (left) for Z. aeneus and 28 mm (right) for C. armatum whereas in pereiopod, maximum average size was 35.00 ± 2.44 mm recorded from C. armatum.  Propodus: Its 5th part of cheliped and pereiopod that position between carpus and dactylus in cheliped and pereiopod of crab species. In cheliped, height size of propodus was 67 mm (left) and 73 mm (right) for C. carnifex whereas average highest size of propodus was 18.50 ± 3.03 mm in pereiopod of C. armatum.
Dactylus: Its last part of cheliped and pereiopod that join with only propodus in cheliped and pereiopod of crab species. In cheliped, maximum size of dactylus was 35 mm (left) and 32 mm (right) for C. armatum whereas average maximum size was 19.75 ± 3.20 mm in pereiopod of Lophozozymus pictor.

Estimated Meristic Character
We measured the meristic characters of 18 crab species in Table 2. Large species C. armatum, counted anterolateral spine: i pair; number of teeth: xv + xiv; merus of cheliped contains i spine in dorsa side and i spine in the ventral side; each propodus of the last four periopods contains ii spines in the dorsal side; dactylus of the 2nd periopod contains xviii spines in the dorsal side and iv spines in the ventral side; dactylus of 3rd periopod contains xviii spines in the dorsal side and ii spines in the ventral side; dactylus of the 4th periopod contains xiv spines in the dorsal side and iv spines in the ventral side; dactylus of 5th periopod contains xx spines in the dorsal side. Open Journal of Marine Science

Species Remark with Sex and Color
In the study crab species were remark with sex and color through observation.
In the world, Bangladesh is the climatically vulnerable country for fisheries [28]. Researcher, twenty eight species reported from marine and freshwater [9] and most of the species used for human consumption [25] but still incomplete study with distinguishing morphometric and meristic character that has impact in the environment for long term sustain with other species. In crab culture have emerged employment and income opportunities [29] [30], but species introducer as distribution and character evolution is very few study happened in South East Asia. Species Criocarcinus superciliosus (Linnaeus, 1758) from china seas [31], Cardisoma armatum from Cape Verde and Senegal to Angola [32], Cardisoma carnifex (Herbst, 1796) from Kenyan mangrove swamp [33], Ocypode pallidula from Leigh Marine Reserve, New Zealand [34] but as distribution first time we find in marine water of Saint Martin's Island. Panopeus lacustris has been introduced in Hawaii in the 1950s [35], Indian River Lagoon [36], Brazil [37] but as distribution for the first time we found in marine water of Saint Martin's Island. Species Pseudosesarma bocourti under Sesarmidae family recorded from Japan [38], Kagoshima [39]; Thailand -Bangkok [40] but first time we found in marine water of Saint Martin's Island that is very extensive and important for ecology and environment to develop history and sustainable cultural in the coastal region.
Xanthidae family Species Atergatis floridus recorded from Sri Lanka [41], Hainan Island and Paracel Islands in China [42], Indian Pacific Ocean [43], Lophozozymus pictor fromnorth-eastern Taiwan, Thailand [44] Hainan Island in Singapore [41], China [42]; Xantho poressa reported from Bulgaria and Turkey coasts. [45], and Zosymus aeneus reported from Okinawa in Japan [46], Hainan Island and Paracel Islands in China [42], Durban in South Africa [47] but as distribution first time introduced with distinguishing character in this South East Asia region of Bangladesh. Habitat modification and introduction of crab species combined to cause loss of biodiversity occurred through anthropogenic activities. However, due to habitat loss, climatic conditions, poor transportation, limitation and lack of funds and resources many species unidentified in marine and freshwater of Bangladesh. Lack of studies on crustacean species identity and importance in South East Asia these results could be significant for next generation researchers around the world with Bangladesh. Therefore, biological investigation and an improved understanding of crab species by local people, fishermen regarding the importance of marine ecosystem of crabs in the South East Asia.

Conclusion
As a crucial investigation, a total of 18 crab species were recorded with morphometric and meristic characters. This original paper will be helpful for the further creation of suitable research plans to conserve marine crab populations, proper identification and investigation to enrich the brachyuran fauna of Bangladesh. All crab species have significant values in fishery, tourism, local economy, human health, socio-economic activities and biodiversity.