Feeding and Predation
Escaping Predation
S. chloronotus seems to suffer very little from predation. This is most likely because it is highly toxic to fish (Yamanouchi 1955; Bakus 1968; Bakus 1981). Gastropods are able to prey on S. chloronotus without being affected by its toxin (Parrish 1972), and research has been conducted to determine how these sea cucumbers avoid predation. When under attack from the gastropod Tonna perdix, S. chloronotus shortens its body and bulges at the point of contact (Kropp 1983). If not completely engulfed by the predator, the sea cucumber will shed part of its body wall by forming into a u-shape and allowing a piece of the body wall to tear off (Kropp 1983). While the predator consumes the discarded bit of body wall, the sea cucumber will roll away, orient itself upright, and then bound away using direct arching peristalsis (Kropp 1983). This bounding away is achieved by a wave of contractions passing along the dorsal longitudinal musculature and then followed by a wave of contraction along the dorso-ventral musculature (Heffernan and Wainwright 1974). As the dorso-ventral contraction is ending, a new contraction passes along the ventral musculature of the body tube (Heffernan and Wainwright 1974). This movement is similar to that found in some caterpillars (see Heffernan and Wainwright 1974 for more detail). Wounds caused during experimental predation were never fatal, and larger prey were more likely to survive because they were not fully engulfed in the initial attack (Kropp 1983). The body wall is regrown following the attack. If S. chloronotus is contacted by a predator, but not attacked, the body wall will stiffen until contact is ended (Kropp 1983). Crawling speed increases significantly after contact and attack (Kropp 1983).
Feeding
Baker (1929) was the first person to publicly suggest that Stichopus chloronotus fed on sand, rather than coral. He was correct when he suggested this, and we now know that Stichopus chloronotus feeds by ingesting sediment and sorting the organic contents from it (Uthicke 1999). They only feed during the daytime hours (Uthicke 1994), and feeding is conducted by using oral tentacles to collect food and pass it to the mouth (Conand et al. 1998). There are generally 20 of these tentacles, and they are approximately 5 mm long (Conand et al. 1998). The video below shows another species of sea cucumber eating in a manner similar to that of Stichopus chloronotus. S. chloronotus exhibits patch selectivity in which they feed on sediments with high microalgal biomass (Uthicke 1999; Uthicke and Karez 1999). They may also select patches with finer sediments, although this is not definite, and the reason they would do this is unknown (Uthicke and Karez 1999). Since S. chloronotus is often found in the field with Holothuria atra, it has been suggested that patch selectivity is used as a means of niche partitioning (Uthicke and Karez 1999). The meiofauna that can be found in many sediments do not actually play a large part in the nutrition of S. chloronotus (Uthicke 1999), and it has been determined that most of their diet consists of bacteria, microalgae, and dead organic matter (Moriarty 1982). This organic matter may be of either plant or animal origin (Moriarty 1982).
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