Eighty-seven percent of specimens were diseased (Fig. 6.7b). Symptoms were
most frequent on the oral side (65 %) and in the posterior lunules (89 %). Lesions
extended to the adjacent posterior interambulacrum (Fig. 6.7b). These lesions were
found in the larger specimens (46.4 to 106.0 mm in length), with a mode (38 %) at
62.7 mm. Some specimens had small black spots with surrounding lesions on the
oral surface (Fig. 6.7a, b). The authors indicated that oils from fishing boats and
commercial crafts are common in this area, and these conditions probably lead to
lesions of the epithelium of the test of E. micropora that subsequently became
infected.
Sea Urchins
Sonnenholzner et al. (2009) studied the effects of predation by fish (the Mexican
hogfish Bodianus diplotaenia), and lobsters (red spiny lobster Panulirus penicillatus, and rocky lobster Scyllarides astori) on the herbivore E. galapagensis.
The authors sampled 10 highly fished and 10 (putatively) lightly fished shallow
rocky reefs in the southeastern area of the Galápagos Islands. Eucidaris galapagensis showed a negative association with non-coralline algae. In addition,
pencil urchins were less abundant where there were many predators indicating an
indirect positive association between predators and non-coralline algae occurred.
Fishing appeared to affect this trophic cascade. The spiny lobster P. penicillatus,
the slipper lobster S. astori, and the hogfish B. diplotaenia were significantly less
abundant at highly fished sites. Sea urchin density was higher at highly fished sites.
Non-coralline algae were nearly absent from highly fished sites, where a continuous carpet of the anemone Aiptasia sp. occurred. The algal assemblage was
mainly composed of encrusting coralline and articulated calcareous algae.
Sonnenholzner et al. (2011) conducted an experiment for measuring lobster
predation on Eucidaris galapagensis in Galápagos. Six slipper lobsters Scyllarides
astori (19.0–26.2 cm total length, 0.50–0.91 kg) and six red spiny lobsters Panulirus penicillatus (25.0–28.0 cm total length, 0.60–1.13 kg) were used as predators. The sea urchin E. galapagensis (36.7–51.6 mm test diameter, average
44.9 mm) was offered as prey to each lobster. Two treatments were used for each
species of lobster and a control treatment of sea urchins with no lobsters. Sea
urchin survivorship was measured for 3 days. Spiny lobsters ate three sea urchins
and attacked an additional four urchins. Slipper lobsters did not interact with sea
urchins. This experiment identified spiny lobsters as potential predators of urchins.
There are many other important predator–prey interactions in the system (Witman
et al. 2010). Slipper lobsters might consume sea urchins in the wild, even though
they did not prey on them in the laboratory. Predation in aquaria does not necessarily indicate predation rates or preferences in the field only that these predators
are capable of eating the prey offered to them. Still, observations in aquaria are
wholly consistent with the limited field observations of trophic interactions
(Sonnenholzner et al. 2011).
6 Echinoderms of Ecuador
213
most frequent on the oral side (65 %) and in the posterior lunules (89 %). Lesions
extended to the adjacent posterior interambulacrum (Fig. 6.7b). These lesions were
found in the larger specimens (46.4 to 106.0 mm in length), with a mode (38 %) at
62.7 mm. Some specimens had small black spots with surrounding lesions on the
oral surface (Fig. 6.7a, b). The authors indicated that oils from fishing boats and
commercial crafts are common in this area, and these conditions probably lead to
lesions of the epithelium of the test of E. micropora that subsequently became
infected.
Sea Urchins
Sonnenholzner et al. (2009) studied the effects of predation by fish (the Mexican
hogfish Bodianus diplotaenia), and lobsters (red spiny lobster Panulirus penicillatus, and rocky lobster Scyllarides astori) on the herbivore E. galapagensis.
The authors sampled 10 highly fished and 10 (putatively) lightly fished shallow
rocky reefs in the southeastern area of the Galápagos Islands. Eucidaris galapagensis showed a negative association with non-coralline algae. In addition,
pencil urchins were less abundant where there were many predators indicating an
indirect positive association between predators and non-coralline algae occurred.
Fishing appeared to affect this trophic cascade. The spiny lobster P. penicillatus,
the slipper lobster S. astori, and the hogfish B. diplotaenia were significantly less
abundant at highly fished sites. Sea urchin density was higher at highly fished sites.
Non-coralline algae were nearly absent from highly fished sites, where a continuous carpet of the anemone Aiptasia sp. occurred. The algal assemblage was
mainly composed of encrusting coralline and articulated calcareous algae.
Sonnenholzner et al. (2011) conducted an experiment for measuring lobster
predation on Eucidaris galapagensis in Galápagos. Six slipper lobsters Scyllarides
astori (19.0–26.2 cm total length, 0.50–0.91 kg) and six red spiny lobsters Panulirus penicillatus (25.0–28.0 cm total length, 0.60–1.13 kg) were used as predators. The sea urchin E. galapagensis (36.7–51.6 mm test diameter, average
44.9 mm) was offered as prey to each lobster. Two treatments were used for each
species of lobster and a control treatment of sea urchins with no lobsters. Sea
urchin survivorship was measured for 3 days. Spiny lobsters ate three sea urchins
and attacked an additional four urchins. Slipper lobsters did not interact with sea
urchins. This experiment identified spiny lobsters as potential predators of urchins.
There are many other important predator–prey interactions in the system (Witman
et al. 2010). Slipper lobsters might consume sea urchins in the wild, even though
they did not prey on them in the laboratory. Predation in aquaria does not necessarily indicate predation rates or preferences in the field only that these predators
are capable of eating the prey offered to them. Still, observations in aquaria are
wholly consistent with the limited field observations of trophic interactions
(Sonnenholzner et al. 2011).
6 Echinoderms of Ecuador
213