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Chapter six: Diet and nutrition
source. Metabarcoding makes use of modern high-throughput DNA sequencing (HTS)
technology which has simultaneously decreased the costs and increased the number of
samples that can be analyzed concurrently as well as the efficiency by which samples can
be processed (Deagle et al. 2009). DNA metabarcoding uses generic primers to amplify
regions of the genome which are preserved across animal phyla. These regions are then
sequenced using a HTS platform. The resulting sequences are then matched using bioinformatic techniques such as Basic Local Alignment Search Tools (BLAST) that interrogate
databases for similar sequences from known taxa. As such, DNA metabarcoding offers the
potential to generate genetic sequences of the complete diet of a predator and a relatively
inexpensive means to conduct repeated sampling over time. However, despite the obvious
benefits of DNA metabarcoding providing a much more accurate portrayal of the niche
breadth of a predator, these techniques are also temporally restricted to dietary intake
represented by the fecal sample obtained.
6.4.2.4 Video and digital recording
Video-data loggers (“crittercams”) attached to free-ranging cetaceans and pinnipeds
can be used to capture cryptic feeding events (prey–capture, predator–prey interactions) and characterize foraging strategies. Other devices such as synchronous motion
and acoustic recording tags (DTAG) are also been increasingly used. A recent study
used DTAGs to describe bottom side-roll feeding behavior in humpback whales along
the seafloor (Ware et al. 2014).
Glossary
Baleen: Rows of plates made of dense, hair-like material (keratin), which hang from the
upper jaw of whales in the Mysticeti order (the baleen whales). Baleen functions
as a filter-feeding apparatus, allowing whales to filter small prey items (e.g., plankton) from surface waters.
Benthic: Living on the seafloor.
Biomass: A measure of the amount of biological (plant or animal) matter from living or
recently living organisms in a given context or system.
Carnivorous: Feeding on other animals.
Cephalopod beaks: Chitinous mandibles or jaws of cephalopods (including squid, cuttlefish, and octopus); commonly referred to as “beaks” due to their resemblance
to the beaks of parrots. Cephalopod beaks are hard, indigestible structures and
consequently, they tend to be the only identifiable parts of cephalopod prey left in
predator stomachs (pinnipeds and cetaceans).
Chitin: A highly insoluble nitrogen-containing polysaccharide, which forms a tough,
semitransparent substance. Like cellulose, chitin functions as a structural polysaccharide and is the main component of arthropod exoskeletons and cephalopod
beaks. Chitin is also found in the cell walls of some fungi and algae.
Cusped: Raised point or projection on the grinding surface of teeth.
Demersal: Living near the bottom of the sea.
Diel: Occurring on a 24 h cycle.
Digestion: The process whereby food and nutrients are rendered soluble and capable of
being absorbed by an organism or by a cell.
Echolocation: Locating objects and investigating the surrounding environment by sensing the echoes returned by high-frequency sound waves emitted by an animal.
Chapter six: Diet and nutrition
source. Metabarcoding makes use of modern high-throughput DNA sequencing (HTS)
technology which has simultaneously decreased the costs and increased the number of
samples that can be analyzed concurrently as well as the efficiency by which samples can
be processed (Deagle et al. 2009). DNA metabarcoding uses generic primers to amplify
regions of the genome which are preserved across animal phyla. These regions are then
sequenced using a HTS platform. The resulting sequences are then matched using bioinformatic techniques such as Basic Local Alignment Search Tools (BLAST) that interrogate
databases for similar sequences from known taxa. As such, DNA metabarcoding offers the
potential to generate genetic sequences of the complete diet of a predator and a relatively
inexpensive means to conduct repeated sampling over time. However, despite the obvious
benefits of DNA metabarcoding providing a much more accurate portrayal of the niche
breadth of a predator, these techniques are also temporally restricted to dietary intake
represented by the fecal sample obtained.
6.4.2.4 Video and digital recording
Video-data loggers (“crittercams”) attached to free-ranging cetaceans and pinnipeds
can be used to capture cryptic feeding events (prey–capture, predator–prey interactions) and characterize foraging strategies. Other devices such as synchronous motion
and acoustic recording tags (DTAG) are also been increasingly used. A recent study
used DTAGs to describe bottom side-roll feeding behavior in humpback whales along
the seafloor (Ware et al. 2014).
Glossary
Baleen: Rows of plates made of dense, hair-like material (keratin), which hang from the
upper jaw of whales in the Mysticeti order (the baleen whales). Baleen functions
as a filter-feeding apparatus, allowing whales to filter small prey items (e.g., plankton) from surface waters.
Benthic: Living on the seafloor.
Biomass: A measure of the amount of biological (plant or animal) matter from living or
recently living organisms in a given context or system.
Carnivorous: Feeding on other animals.
Cephalopod beaks: Chitinous mandibles or jaws of cephalopods (including squid, cuttlefish, and octopus); commonly referred to as “beaks” due to their resemblance
to the beaks of parrots. Cephalopod beaks are hard, indigestible structures and
consequently, they tend to be the only identifiable parts of cephalopod prey left in
predator stomachs (pinnipeds and cetaceans).
Chitin: A highly insoluble nitrogen-containing polysaccharide, which forms a tough,
semitransparent substance. Like cellulose, chitin functions as a structural polysaccharide and is the main component of arthropod exoskeletons and cephalopod
beaks. Chitin is also found in the cell walls of some fungi and algae.
Cusped: Raised point or projection on the grinding surface of teeth.
Demersal: Living near the bottom of the sea.
Diel: Occurring on a 24 h cycle.
Digestion: The process whereby food and nutrients are rendered soluble and capable of
being absorbed by an organism or by a cell.
Echolocation: Locating objects and investigating the surrounding environment by sensing the echoes returned by high-frequency sound waves emitted by an animal.