Abstract
The effects of temperature on an exotic aquatic snail Pomacea canaliculata (Lamarck, 1819) collected from the Shatt Al-Arab intertidal zone were investigated. A series of laboratory experiments were conducted during the summer period of 2017. Individuals of new born snails hatched in the laboratory from adult snails were collected from Shatt Al-Arab intertidal zone, and subjected to five fixed temperatures: 15, 25, 35, 40 and 45 Cº, after short term thermal acclimation. The heartbeats (HB) were counted at each temperature level. The results showed significant direct increase of HB from 15 Cº (19.8 HB/min) up to 25 Cº (76 HB/min) (P<0.05) as well as from 25 Cº to 35 Cº (93 HB/min). At 40 Cº the snail HB shows only slight insignificant increase (79 HB/ min). At 45 ºC the HB became irregular and showed negative thermo cardiac activity (HB dropped to 50.4/min). The minimum HB rate of 11/min was recorded at 15 Cº and the maximum value of 119 HB/min was recorded at 40 Cº. The study concluded that P. canaliculata can be highly stressed when exposed to extreme temperature experienced during the prolonged summer months and will no longer tolerate living in the intertidal zone of Shatt Al-Arab.
Highlights
The snail P. canaliculata (Lamarck, 1819)is a freshwater species, originally native to South America tropical and subtropical regions
As an exotic species to the intertidal zone of Shatt Al-Arab river system, the snail may be causing great impacts on the other native gastropods living in the habitat [8] due to the fact that the Mollusca's community of Shatt AlArab is comprised of several gastropod's species namely; Neritina schlaeflii, Theodoxus jordani, Melanoides tuberculata, Melanopsis praemorsum and Radix auricularia [9], all of them are much smaller in size and have less active mobility than P. canaliculata
The results showed that cardiac activity of the snail is a direct positive function of temperature at the thermal limits between 15-40 oC, in general
Summary
The snail P. canaliculata (Lamarck, 1819)is a freshwater species, originally native to South America tropical and subtropical regions. In Iraq the species has been reported in the recent ten years (2007-2017) in Baghdad and Shatt Al-Arab [5, 6], to the best of our knowledge its existence in small rivers and canals of agricultural farms is indicated in Babylon during 1990-1991. At that time, it was used in fish aquariums and large numbers of the snail were transferrted to Basrah city and subsequently the species invaded Shatt Al-Arab habitat. As an exotic species to the intertidal zone of Shatt Al-Arab river system, the snail may be causing great impacts on the other native gastropods living in the habitat [8] due to the fact that the Mollusca's community of Shatt AlArab is comprised of several gastropod's species namely; Neritina schlaeflii, Theodoxus jordani, Melanoides tuberculata, Melanopsis praemorsum and Radix auricularia [9], all of them are much smaller in size and have less active mobility than P. canaliculata
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