Distinguishing Characteristics Proximal Middle And Distal Pecten Of

distinguishing characteristics * proximal, middle, and distal pecten of postabdominal claw all the same size. *

Distinguishing Characteristics
*
Proximal, middle, and distal pecten of postabdominal claw all the
same size.
*
Ocellus present.
*
Swimming hair at the base of the second segment of the
three-segmented ramus extends beyond tip of ramus.
*
Swimming hairs of antennae do not extend beyond posterior margins
of valves.
*
Small head and valves, no more than 1.3 mm in length.
*
Head often with small anterior point during summer.
Similar Species
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Commonly confused with D. parvula.
Geographic Distribution
Daphnia ambigua occurs in Europe and North and South America.
Populations of D. ambigua have been seen in Mexico, the Central United
States,the Appalachian range, the Atlantic and Pacific coasts. (9)
Reported Habitats
Curiously, D. ambigua is often found in cool deep water in the lower
thermocline, suggesting a tolerance to cold temperatures, but on the
other hand it is one of the most common Daphnia species found in
tropical and sub tropical regions.
Food & feeding behavior
Daphnia ambigua are the smallest daphnia species in North America.
Even with increased food concentrations, the maximum attainable length
of Daphnia ambigua is less than half that of D. pulex. D. ambigua’s
small size has been hypothesized to be due to either size selective
predation or resources allocated toward predation defense such as a
thicker carapace. (5)
Reproductive Habits
Daphnia ambigua showed optimal reproductive capability from 25-30°C.
(6)
Predation
In the laboratory setting, one-day old Daphnia ambigua were eaten by
Mesocyclops leuckarti. Larger daphnia not eaten were injured by
copepods trying to eat them. (1)
Daphnia ambigua is the smallest Daphnia species, rarely exceeding 1 mm
in body length. Its small size makes it especially vulnerable to
predation by Chaoborus larvae.
In response to Chaoborus kairomones, or chemical given off by
Chaoborus, adults & juvenile D. ambigua often form a sharp pointed
helmet on the central axis of the head, typically seen in mid to late
summer. exposed to Chaoborus larvae or larvae extract exhibited
helmets. Adults & older young had significanlty shorter helmets or no
helmet at all. (2) Helmets are only induced when juveniles are
directly exposed to the Chaoborus factor; if only exposed to Chaoborus
factor as eggs, helmets will not develop in the juvenile stages. (3)
At lower food levels, D. ambigua that have been exposed to Chaoborus
and grown helmets have reduced growth, survival and reproductive rates
than D. ambigua not exposed to Chaoborus. (4)
Competition
In a laboratory setting, Daphnia ambigua excluded the rotifer
Keratella cochlearis in high food concentrations and was able to
survive starvation much longer than the rotifer (8). D. ambigua has
been shown to suppress ciliate populations by predation and
interference competition and could possibly be a trophic link between
nanoplankton and metazon zooplankton (10).
Migration
Daphnia ambigua in monomictic, eutrophic lake El Plateado, Chile,
migrated vertically with the greatest amplitude of migration observed
in the warm season(7).
Seasonal Variations
The D. ambigua population in lake El Plateado, Chile, showed seasonal
variation, being common in the winter and absent from the water column
in the summer. (7)
D. ambigua populations in North American lakes are largest in the
spring (11).
(2)
Adults & young exposed to Chaoborus larvae or larvae extract exhibited
helmets.
(NOTE: Put this picture in at the words “sharp pointed helmet” in the
Predation section)
(5)
(NOTE: Put this picture in at the words “maximum attainable length ”
in the Food & Feeding Behavior section)
(1) CHANG, K. H. and T. HANAZATO. (2003) Vulnerability of cladoceran
species to predation by the copepod Mesocyclops leuckarti: laboratory
observations on the behavioural interactions between predator and
prey. Freshwater Biology. 48: 476-484.
(2) HEBERT, P.D. and P.M. GREWE. (1985). Chaoborus-induced shifts in
the morphology of Daphnia ambigua. Limnol. Oceanogr. 30: 1291–1297.
(3) HANAZATO, T. (1990) Induction of helmet development by a Chaoborus
factor in Daphnia ambigua during juvenile stages. Journal of Plankton
Research. 12:1287-1294.
(4) HANAZATO, T. (1991) Influence of food density on the effects of a
Chaoborus -released chemical on Daphnia ambigua . Freshwater biology.
25: 477-483.
(5) LYNCH, M. (1992) The Life History Consequences of Resource
Depression in Ceriodaphnia Quadrangula and Daphnia Ambigua. Ecology.
73:1620-1629.
(6) MALLIN, M.A. and W.E. PARTIN, WE (1989) Thermal Tolerances of
Common Cladocera. Journal of Freshwater Ecology 5: 45-50.
(7) RAMOS-JILIBERTO, R. and L. R. ZÚÑIGA. (2001) Depth-selection
patterns and diel vertical migration of Daphnia ambigua (Crustacea:
Cladocera) in lake El Plateado. Revista Chilena de Historia Natural 74:573-585.
(8) MACISAAC, H.J., and J.J. GILBERT. (1991) Competition between
Keratella cochlearis and Daphnia ambigua : effects of temporal pattern
of food supply. Freshwater biology. 25: 189-198.
(9) HEBERT, P.D., J.D. WITT, and S.J. ADAMOWICZ. (2003)
Phylogeographical patterning in Daphnia ambigua: Regional divergence
and intercontinental cohesion. Limnology and Oceanography. 48:
261-268.
(10) WICKHAM, S.A., and J.J. GILBERT. (1993) The comparative
importance of competition and predation by Daphnia on ciliated
protists. Archiv fur Hydrobiologie. 126: 289-313.
(11) ALLAN, JD. (1977) An Analysis of Seasonal Dynamics of a Mixed
Population of Daphnia, and the Associated Cladoceran Community.
Freshwater Biology 7: 505-512.