Watering Pot Shell, Brechites penis (Linnaeus, 1758), a new record to India (Mollusca: Bivalvia: Anomalodesmata)
Deepak Samuel Vijay Kumar 1, Thangaiyan Anbalagan 2, Manickam Nithyanandan 3 & Naveen Namboothri 4
1 Energy & Environment Unit, United Nations Development Programme, GoMBRT, 102/26, Jawan Bhawan, Devipattinam Road, Kenikarai, Ramanathapuram, Tamil Nadu 623504, India
2 Gulf of Mannar Biosphere Reserve Trust (GoMBRT), 102/26, Jawan Bhawan, Devipattinam Road, Kenikarai, Ramanathapuram, Tamil Nadu 623504, India
3 Environmental Department, “Sabah Al Ahmad Sea City”, La Ala Al Kuwait Real Estate Co. K.S.C., Souk Al Kuwait, 6th Floor, Office No. 613, P.O. Box 22964, Kuwait 13090.
4Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka 560012, India
1 email@example.com (corresponding author), 2 firstname.lastname@example.org, 3 email@example.com, 4 firstname.lastname@example.org
The watering pot shells and pepper pot shells are rare and interesting bivalves under the Family Clavagellidae, typical filter-feeder encased in a tube of its own secretion. Beginning life as a tiny bivalve, the shell develops into a calcareous tube with the embryonic valves attached to its outer surface and its base is a perforated, raised disc, fringed with small tubes (Dance 1992). Another species of this family, Brechites dichotomus was recorded by Gravely (1941), Hornell (1921) from Madras and by Sathyamurthi (1956) from the Gulf of Mannar, which is available in the museum collection of Central Marine Fisheries Research Institute (CMFRI), Mandapam. Palk bay lies on the southeastern coast of India extending from Point Calimere in the north to Rameswaram Island in the south, it has diversified habitats like seagrass, mangroves and coral reefs. Bottom trawling an important fishing method practiced by the fisher folk in this region brings ashore enormous quantities of benthic molluscs as bycatch. The present record of the rare bivalve, B. penis from Palk Bay (Image 1) is new to the molluscan fauna of India.
Materials and Methods: We collected unusual bivalve shells from bycatch of bottom trawls operated in the Palk Bay region. A single individual of Brechites penis collected was preserved in 70% alcohol and identified, based on Sathyamurthy (1956) and Morton (2006b). The collected specimen was deposited in the museum of Zoological Survey of India (ZSI), Marine Biology Regional Centre (MBRC). Another species of genus Brechites available in the collection of Central Marine Fisheries Research Institute (CMFRI), Mandapam was examined for comparison.
Bivalvia Linnaeus, 1758
Heterodonta Neumayr, 1884
Anomalodesmata Dall, 1889
Family Clavagellidae d’ Orbigny, 1843
Genus Brechites Röding, 1798
Brechites penis (Linnaeus, 1758) (Image 2A)
Material examined: ZSI/MBRC M542, 28.iii.2011, Palk Bay landing centre at Mandapam (9017’9.50’’N & 7909’19.80”E), one specimen, true shell 4mm and adventitious tube length 74mm, collected at 5–15 m depth from trawl net bycatch by Dr. V. Deepak Samuel; Single specimen, Brechites dichotomus (Chenu) reg.no. M.333 (Image 3 A), shell on display at the CMFRI museum, Mandapam, collection details unknown, true shell 6mm and adventitious tube length 78mm.
Description: Both the left and right shell valve measured 4mm (Table 1), whereas in species like the Japanese Watering Pot Shell, Stripulina ramosa the right valve is 16mm in size and the left valve is 9mm in size (Morton 2006a). In B. dichotomous, the true shell measured 6mm for both valves. Tubules arising from the periphery of the disc were 44 in total while eight tubules were forked and further branched to form a single radiating branch (Image 2B). A marked difference was noted in the case of pore distribution at the basal disc (37 in B. penis and 114 in B. dichotomus). In B. penis pores were concentrated more on the periphery but hardly any in the centre. Absence of forked tubules (biramus tubules) was noticed in B. dichotomus, while B. penis had eight forked tubules. Adventitious tube of B. penis was almost straight when compared to the small curvature at the anterior end for B. dichotomus.
In B. dichotomus, the tube had a perforated anterior end, with a slightly elevated margin leaving a convex appearance in the middle, bearing a fringe of tubules (Sathyamurthi 1956). The sample of Verpa (=Brechites) penis collected from Shangi had a tube length of 120mm (Tan et al. 2011) whereas the basic tube length for this species is not more than 100mm. Penicillus philippinensis has a varying tube length between 66–99 mm (Morton 2006b) while for B. attrahens, the tube length is 213mm with 18mm width (Gab-Alla 1999).
Remarks: A new record to India. We understood from interaction with fishermen that the specimen of B. penis was collected from trawl net operated in seagrass beds of Palk Bay. The habitat is supposedly similar to that of B. attrahens from the Red Sea (Gab-Alla 1999).
The presence of embryonic shell valves on the side of the tube represents the mature form of this aberrant bivalve (Morton 2002b). A pedal gape aids in pumping of water into the mantle cavity as an ancestral feeding mechanism (hence the name watering pot shell). The life history of these curious, warm-water molluscs is almost completely unknown except for the biology carried out by Purchon (1956). However, reports on functional morphology of Humphreyia strangei and Stripulina ramosa by Morton (2002a, 2006a) and certain new records from the Miocene period (Yates 2011) widens our understanding of this rare family of bivalve molluscs. Status of B. penis is unclear throughout the Indo-Pacific region. In Singapore, B. penis is listed as “presumed nationally extinct” on the Red List of threatened animals (Tan et al. 2011). In India, there is enough scope to collect scientific data to understand the diversity, distribution, biology, ecology and population characteristics of this rare bivalve mollusc for efficient management.
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