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International Journal of Marine Science 2015, Vol.5, No.3, 1-7
http://ijms.biopublisher.ca
3
. The present swarming
occurred in the first quarter of the moon; however, the
study area is not under tidal influence.
The swarms occurred in the first quarter moon (7 days
after full moon). The swarmed individuals were
observed in the submerged concrete blocks (<10 cm
depth) in the lake shore. Density of swarmed
specimens was estimated using a quadrat (0.25m
2
)
with 15 cm height, which prevented the escape of
organisms during sampling.
Polychaetes were
collected during the sunset hours of August 31
st
, 2010
and preserved in 4% buffered formalin. Collected
samples were brought to the laboratory and sorted out.
The abundance of polychaetes was expressed in
numbers per square meter
. The samples were identified using standard
references
. Surface water
(duplicates) was collected in 125 ml DO bottle for
dissolved oxygen measurements and the rest of the
parameters such as temperature, salinity and pH were
analyzed by a Systronics water analyzer
.
2 Results
Dendronereis aestuarina
were assembled as a thick
and profuse swarm on a submerged concrete platform
located in the land-water interface at a depth of <10cm.
Following careful identification, it was found that the
swarms were constituted of only a single species:
D.
aestuarina
. Examined live individuals were reddish
brown mature worms; all female worms carrying
unfertilized eggs (Figure 2). Six random samples were
taken using a standard quadrat and we measured the
average density (Figure 3 a&b) of swarmed
polychaetes (14800 indls. m
-2
) and mean length (86 ±
16mm). Sex ratio [number of males (M) / number of
females (F)] of swarm was 3:1 among 60 specimens
analyzed. The eggs collected from the polychaetes
were 0.33 ±0.08 mm in diameter; they were spawned
in firm, irregular gelatinoid masses. Water quality
parameters such as water temperature, salinity, pH and
dissolved oxygen were measured during the sample
collection. Temperature in the water column was
27.6°C. Turbidity showed moderately low value (5.7
[NTU- Nephelometric Turbidity Units]). However,
dissolved oxygen content in the water column was
quite low (2.9 ml L
-1
) and pH slightly acidic in nature
(6.5).
Figure 2
Unfertilized eggs collected from swarmed
Dendronereis
aestuarina
Figure 3 (a) Microphotograph of
Dendronereis
aestuarina
Southern, 1921(
b) Red colored reproductive swarm of
D.
aestuarina
, August 31
st
, 2010 (Photo taken at sunset, 5.30pm)
at Periyar River, India
SYSTEMATICS
Order Phyllodocida Dales, 1962
Family Nereididae
Genus
Dendronereis
Peters, 1854
Dendronereis aestuarina
Southern, 1921
Dendronereis aestuarina
Southern, 1921 pl. XX,
Figure 4A-N, text-figs. 9a-h
Dendronereis aestuarina
is an annulated worm,
endowed with locomotive bristles or setae. Papillae
present on oral ring of pharynx. First three pairs of
branchiae pectinate and the rest bipinnate. Anterior
neuropodia with 10-12 lobes and an inferior ligule.