International Journal of Marine Science 2016, Vol.6, No.30, 1-8
1
Research Article Open Access
Occurrence of Mass Swarming of Family Acartiidae (Calanoid Copepods)
(Zooplankton) in Ashtamudi Estuary, Kerala
K.S. Santu
, S. Bijoy Nandan, K. Athira
Department of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Cochin 682 016,
Kerala, India
Corresponding author email:
International Journal of Marine Science 2016, Vol.6, No.30 doi
Received: 21 Jul., 2016
Accepted: 02 Sep., 2016
Published: 05 Sep., 2016
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Santu K.S., Nandan S.B. and Athira K., 2016, Occurrence of Mass Swarming of Family Acartiidae (Calanoid Copepods) (Zooplankton) in Ashtamudi Estuary,
Kerala, International Journal of Marine Science, 6(30): 1-8 (doi
Abstract
Aggregation and swarming of different species of zooplankton has been reported worldwide from estuaries and coastal
systems. But such swarming behaviors are seldom reported from tropical water bodies. Mass swarming and aggregation of
Acartia
species (91%) in mesozooplankton were observed in Ashtamudi estuary on the west coast during late monsoon season (2015). The
mesozooplankton density recorded was 106578 ind.m
-3
; composed of calanoid copepods dominated by females (97%), fish eggs
(2.4%) and cyclopoids (0.2%). Even though swarming of copepods appears to be a common phenomenon in temperate shallow
waters, reports from tropical estuaries are less. Here, females were outnumbering males, with sex ratio of 1:3 (male to female) and
observed with spermatophore in the collections suggesting aggregation of copepods that might be for mating purpose. Since the
males are usually short lived, swarming will facilitate high rate of fertilization and it helps the copepods in existence and propagation.
They are also able to disperse easily by producing resting eggs leading to their sudden appearance in water column when temperature
rises and salinity increases. Presence of such swarms indicates habitat shifts due to climatic change, water pollution and
eutrophication issues in the coastal environment.
Keywords
Mass swarming;
Acartia
species; Ashtamudi estuary; Zooplankton
1 Introduction
Swarming of zooplankton at various temporal and spatial scales has been observed generally; aggregative
behavior has been well studied in larger aquatic organisms (fish, krill) and terrestrial animals (birds, insects), but
little is known for copepod aggregation. Even though swarming behavior of copepods in temperate region is
available, estuarine region in the tropics has remained almost unknown for many reasons. Furthermore, there is
little quantitative knowledge available on the reasons for aggregations in zooplankton and the purpose of these
aggregations. Several reports are available on the swarming of zooplankton like amphipods along the west coast
of India, (Nair 1972) and ostracods, salps, medusa and pelagic amphipods from off Kutchh region, Gujarat
(Paulinose and Aravindakshan 1977).
In aquatic zooplankton community, copepoda is the most dominant and second largest crustacean taxa,
representing 70% of the oceans biomass; consumed by a wide range of predators forming the important
phytoplankton and micro zooplankton grazers, which is a major trophic link to many predatory invertebrates and
fishes (Atkinson 1996). Among the calanoids, members of the genus
Acartia
are the major constituents of the
holoplankton communities in coastal zones, estuaries and other semi-enclosed marine areas (Conover 1956,
Abraham 1969, Alcaraz 1983, Lakkis 1994). Family Acartiidae is distributed worldwide and are mostly common
and abundant in estuarine and coastal waters. The most commonly occurring calanoid copepods, especially
A.
southwelli
and
A. centrura
, are the inhabitants of estuaries that have the capacity to grow fast and breed
continuously with high reproductive capacity.
Acartia
southwelli
, the only representative of the subgenus
Euacartia
that was the major component of the swarm reported; originally described incompletely by Sewell from
Kilakarai (9°25' N, 78°50' E), Tamil Nadu, South east coast of India (Sewell 1914).
