Title

Analysis of sediments carried by a tropical intertidal sea cucumber, Holothuria inornata

Presentation Type

Poster

Abstract

On the Pacific coast of Costa Rica, the sea cucumber Holothuria inornata is typically found covered by natural sediments acquired from its surroundings in the rocky intertidal zone. Very little is known about this behavior, and even the most basic data about how much and what kinds of sediments are carried are unknown. We examined the composition of substrate on individuals captured at San Miguel Biological Station in Cabo Blanco Absolute Reserve, Costa Rica in order to learn more about this understudied behavior.

We collected 30 individuals ranging from 94-193 mm in length at low tide from June- July 2012. At the time of capture, all sea cucumbers were entirely covered by sediments tightly adhered to the back of the animal. We removed the sediments from the back of each sea cucumber, dried the sediments, sorted them according to material, and weighed them. H. inornata at this location carried shell fragments, pebbles, sand, and other small items. The dry weight of sediments carried by an individual sea cucumber reached a maximum of 23.7 g. The mean composition BY WEIGHT of sediments, taking into account the three principal sediment types, was 45% shell, 30% pebble, and 25% sand, although individual compositions varied greatly (16.0-67.4% shell; 0.8-69.0% pebble; 11.4-69.1% sand). A simulation model showed that this degree of variation is not expected from random selection of sediment; the sea cucumbers exhibited individual selectivity.

Background sediment composition was assessed by random point sampling in the field. The composition of sediments in the field with 95% confidence intervals, taking into account the three principle sediment types, was 24% (19.74-28.81%) shell, 38% (33.02-43.26%) pebble, and 38% (33.02-43.26%) sand. The difference between environmental composition and average composition carried by sea cucumbers is further evidence that sea cucumbers may be exhibiting some degree of selectivity.

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Apr 12th, 3:00 PM Apr 12th, 4:00 PM

Analysis of sediments carried by a tropical intertidal sea cucumber, Holothuria inornata

UC Ballroom

On the Pacific coast of Costa Rica, the sea cucumber Holothuria inornata is typically found covered by natural sediments acquired from its surroundings in the rocky intertidal zone. Very little is known about this behavior, and even the most basic data about how much and what kinds of sediments are carried are unknown. We examined the composition of substrate on individuals captured at San Miguel Biological Station in Cabo Blanco Absolute Reserve, Costa Rica in order to learn more about this understudied behavior.

We collected 30 individuals ranging from 94-193 mm in length at low tide from June- July 2012. At the time of capture, all sea cucumbers were entirely covered by sediments tightly adhered to the back of the animal. We removed the sediments from the back of each sea cucumber, dried the sediments, sorted them according to material, and weighed them. H. inornata at this location carried shell fragments, pebbles, sand, and other small items. The dry weight of sediments carried by an individual sea cucumber reached a maximum of 23.7 g. The mean composition BY WEIGHT of sediments, taking into account the three principal sediment types, was 45% shell, 30% pebble, and 25% sand, although individual compositions varied greatly (16.0-67.4% shell; 0.8-69.0% pebble; 11.4-69.1% sand). A simulation model showed that this degree of variation is not expected from random selection of sediment; the sea cucumbers exhibited individual selectivity.

Background sediment composition was assessed by random point sampling in the field. The composition of sediments in the field with 95% confidence intervals, taking into account the three principle sediment types, was 24% (19.74-28.81%) shell, 38% (33.02-43.26%) pebble, and 38% (33.02-43.26%) sand. The difference between environmental composition and average composition carried by sea cucumbers is further evidence that sea cucumbers may be exhibiting some degree of selectivity.