• Abstract and Figures
• Public Full-text

Plankton Benthos Res 8(1): 38–45, 2013 Plankton & Benthos Research © The Japanese Association of Benthology Contrasting anti-predation responses in the intertidal periwinkle Littorina sitkana: effects of chemical cue, body size and time of day HISAE OJIMA ＆ SATOSHI WADA* Laboratory of Marine Biology, Graduate School of Fisheries Science, Hokkaido University, 3–1–1 Minato-cho, Hakodate 041– 8611, Japan Received 24 August 2012; Accepted 11 February 2013 Abstract: Some animals show multiple behavioral responses after detection of chemical cues indicating a predation threat. Individuals of the high intertidal periwinkle, Littorina sitkana, showed two contrasting anti-predation re- sponses, immobile cautiousness and active fleeing, against the predatory crab, Hemigrapsus sanguineus. This study examined the combined effects of chemical cues of predation threat (crab, crushed conspecific, mixed crab and crushed conspecific, and control), body size, and time (morning, mid-day and late-evening) on the anti-predation be- haviors of L. sitkana. The cautious response of L. sitkana was strongest under the crab treatment, with the earliest fleeing response appearing when presented with the mixed chemical cue of crabs and crushed conspecifics. Time of day also affected the anti-predation responses, with a longer cautious response during late-evening than mid-day under control conditions, and no significant difference between late-evening and mid-day in response to the three types of chemical cues of predation threat. The fleeing response occurred more rapidly during late-evening than mid- day for the four types of chemical conditions; there was no significant difference between morning and mid-day under the control condition; and it occurred more rapidly during morning than mid-day under the three predation threat conditions. Larger individuals showed longer cautious responses for all conditions and remained submerged in seawater for longer under the three predation threat conditions. It is suggested that the level of predation risk may be assessed by L. sitkana and used to elicit the appropriate of the two contrasting anti-predation responses. Key words: anti-predatory response, chemical cue, Littorina, periwinkle sponses according to the level of predation risk and various Introduction external and internal factors related to the costs (Lima & Animals may protect themselves from predators in vari- Dill 1990, Mathis & Hoback 1997, Wellborn 2002). ous ways. Anti-predation strategies include morphological Animals in aquatic environments typically detect poten- structures (Lively 1986, Kishida et al. 2006, Vaughn 2010), tial predators by chemical cues released from the predator life history characters (Crowl & Covich 1990, Behrens (Chivers et al. 1996, Mima et al. 2003) and/or damaged Yamada et al. 1998) and behaviors (Hazlett & McLay conspecifics (Hazlett 1994, Higuchi et al. 2004). Some spe- 2000, Mima et al. 2003, Gristina et al. 2011), the latter cies show multiple behavioral responses in detecting being the most pervasive response against predators in ani- chemical cues (Lehtiniemi 2005, Wasson & Lyon 2005, mals (reviewed by Lima & Dill 1990). Anti-predation be- Mach & Bourdeau 2011). A freshwater snail, Physella gy- havior is associated with energetic costs (Martín & Lopez rina, has been shown to differentiate between cues from 2000, Martín et al. 2005, Iwami et al. 2007) and opportu- two different predators, crayfish and pumpkinseed fish nity costs that are related to other behaviors such as forag- (Turner et al. 1999): hiding under cover in the presence of ing and mating (Reaney 2007, Selden et al. 2009), so intui- fish; and moving to the water surface in the presence of tively it is expected that animals adjust their behavioral re- crayfish. Ichinose (2002) reported that, in response to an extract of conspecifics, small Pomacea canaliculata (fresh- * Corresponding author: S. Wada; E-mail, wadas@fish.hokudai.ac.jp water periwinkles) crawl out of the water and (under the Contrasting anti-predation responses in the intertidal periwinkle Littorina sitkana 39 same conditions) large individuals bury themselves in the 140°58E). All periwinkles were out of water when col- substrate. The body size and sex of porcelain crabs affect lected. Prior to each experiment, individual periwinkles the decision to perform two mutually exclusive tactics were kept in plastic tanks (56×39 cm, ×21 cm high) with against predators: fleeing and fighting (Wasson & Lyon running natural seawater for 12 to 24 hours under ambient 2005). These flexible anti-predator behaviors suggest that temperature and a natural light cycle. They were not fed many aquatic invertebrates somehow assess the immediate during this period, and most remained above the waterline predation risk in order to select the most appropriate re- in the tanks. sponse. Experimental seawater with chemical cues was pro- Aquatic animals show distinct activity rhythms en- duced using the following procedures about three hours trained by the physical environment, including the diurnal before each of the trials. Predator cue water was prepared light cycle, tidal rhythms and temperature. For example, by placing five H. sanguineus into three liters of seawater many crabs and sea urchins have a nocturnal activity (crab treatment). Crushed conspecific cue water consisted rhythm and are less active during daylight (see, for exam- of mixing five crushed L. sitkana into 3l seawater (conspe- ple, Skajaa et al. 1998, Yoshimura & Motokawa 2010). cific treatment). Mixed cue water was composed of five H. Since predation and the efficacy of anti-predation behav- sanguineus and five crushed L. sitkana in 3l seawater iors are considered to vary with the physical environment, (within which the H. sanguineus always vigorously ate the the environmental rhythms of potential prey animals affect crushed L. sitkana). Preliminary trials showed that these predation risk (Jacobsen & Stabell 1999, Sakamoto et al. cue concentrations were sufficient to initiate responses in 2006). However, few studies have investigated the effects L. sitkana. Control water was natural seawater without ad- of environmental rhythms on anti-predator responses. ditional chemical cues. The present study investigates the combined effects of Behavioral trials were carried out using the same proce- chemical cues of predation threat, body size and time of dure for all experiments under laboratory conditions analo- day on the anti-predator behaviors of the intertidal peri- gous to those in which the periwinkles were maintained, winkle, Littorina sitkana. This species is a herbivorous using small plastic containers (10×14 cm, ×5 cm high) on gastropod commonly found in sheltered locations high in the underneath of which a circle of 2 cm diameter was the intertidal zone. Although high densities of L. sitkana drawn. At the start of each trial, 150 ml of one of the cue are found in tidal pools in some study sites (Jones & solutions, or control water, was introduced to each con- Boulding 1999), there is a difference in intertidal distribu- tainer (corresponding to a depth of 1.07 cm). For each trial, tion among populations: Behrens Yamada et al. (1998) a periwinkle was placed within the circle marked on the compared three populations of L. sitkana and found that container, and its behavior was observed for ten minutes. the one with the highest predation risk has the highest in- During preliminary observations, L. sitkana showed two tertidal distribution. When L. sitkana individuals from the contrasting behavioral responses to the chemical cues: (1) a high intertidal zone were transferred to the low intertidal cautious response, in which they moved very slowly and zone, they displayed a strong and consistent tendency to stayed within the circle, not withdrawing inside the shell; move shoreward (Rochette & Dill 2000). This species has and (2) a fleeing response in which they moved quickly out been shown to respond to chemical cues indicating preda- of the circle to the edge of the container and climbed up tion threat (Behrens Yamada et al. 1998), and a difference above the waterline. in escape behavior between populations has also been ob- The duration of the cautious response was defined as the served: upward migration of individuals from rocky period from the start of the trial to when the periwinkle shores; and hiding in crevices by individuals on a mud flat moved outside the circle. The fleeing response was defined (Behrens Yamada et al. 1989). In preliminary observations as the period between the end of the cautious response and in the present study, L. sitkana individuals collected from when the individual climbed vertically above the waterline the study site showed two contrasting anti-predation re- of the container, which marked the end of the trial. Trials sponses against the shore crab, Hemigrapsus sanguineus: were also ended if after a total of 10 min. the periwinkle immobile cautiousness and active fleeing,. Hemigrapsus is remained within the circle and/or under the water surface. a common nocturnal predator on periwinkles along rocky The shell length of each periwinkle was measured with shores in northern Japan. calipers to the nearest 0.05 mm. Three trials were con- ducted at three times each day (i.e. morning, 7:30–9:30; mid-day, 11:45–13:45; and late-evening, 20:45–22:45), from Materials and Methods mid-day on 7 August to the morning of 11 August 2006. A The study was conducted between 7 and 11 August series of trials at each time was conducted for all treat- 2006. Individuals of the periwinkle L. sitkana (6.3– ments, using 15 periwinkles for each treatment combina- 16.3 mm in shell length) and the sympatric predatory shore tion at each time per day, for a total of 720 individuals. crab, H. sanguineus, were collected from the intertidal Since observations often ended before observing either zone in Usujiri, Minami–Kayabe, on the Pacific rocky of the two behavioral responses (i.e., cautious response coast of south Hokkaido, northern Japan (41°57N, and/or fleeing response), the experiment produced cen- 40 H.

Load more

  8

Copy Link