Foods, feeding, & growth
  black dot
  Preferred foods, feeding ecology, & growth: genera R-T
 

This section continues with information on diets and feeding ecology of west-coast nudibranch & relatives genera D-G. Information on diets and feeding ecology of other west-coast genera can be found in other sections:
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA A-C,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA D-G
,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA H-M,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA N-P
,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: SACOGLOSSANS, and INGESTIVE CONDITIONING.

  black dot
 

Rostanga

  black dot
Research study 1
 

photograph of dorid nudibranch Rostanga pulchra
Adult Rostanga pulchra eat principally the encrusting sponge Ophlitaspongia pennata.  Studies at Friday Harbor Laboratories, Washington show that Rostanga can readily detect chemical cues from its prey from a distance and follow them upstream to the source.  Rhinophores are likely the means used by Rostanga to locate its prey.  Cook 1962 Veliger 4: 194

NOTE  rhinophores are apparently not used by all opisthobranchs for distance-chemical perception.  Tritonia diomedea and Aplysia spp. use theirs in this way - for location of food and mates - but other species, such as Hermissenda crassicornis, are reported to use their rhinophores for rheoreception (perception of currents)

  black dot
Research study 2
  scanning e-micrograph showing location of rhinophores in the veliger larva of the dorid nudibranch Rostanga pulchra
Research studies at Friday Harbor Laboratories, Washington reveal that Rostanga has tiny rhinophores in the veliger stage. They first appear about 1mo after hatching and are located at the base of the velar lobes.  Each has several ciliary tufts linked by nerves to a ganglion situated within the lumen of the rhinophore.  These ganglia, in turn, connect with the optic ganglia and then, in turn, with the cerebral ganglia.  Owing to an apparent lack of nerve connections from the rhinophoral ganglia to the sensory cells, the rhinophores are likely non-functional until the time of settlement and metamorphosis.  Ultimately, these larval structures transform into the adult rhinophores.  The authors note that R. pulchra is the first reported species of opisthobranch that has rhinophores in the larval stage.  Chia & Koss 1982 Cell Tiss Res 225: 235.
  black dot
Research study 3
 

photograph of dorid nudibranch Rostanga Pulchra crawling on its principal food sponge Ophlitaspongia pennataAs noted in Research Study 1 above, the nudibranch Rostanga pulchra feeds on red, carotenoid-containing sponges like Ophlitaspongia pennata.  The nudibranch sequesters the carotenoid pigments, becomes red in colour, and presumably benefits from the resulting camouflage protection.  Obviously, it would be adaptive if the nudibranch were attracted to its prey by perception of the same compounds that it sequesters.  However, the carotenoids sequestered are non-polar; hence, relatively insoluble in water. Experiments at the Bamfield Marine Sciences Centre, British Columbia using Y-tube methodology confirm that Rostanga pulchra is attracted to whole sponge Ophlitaspongia pennata (17/20 positive results).  Moreover, by extracting the sponge with methanol (to obtain the soluble polar compounds) and hexane (insoluble non-polar compounds) the authors show that in addition to being attracted to methanol (polar) extracts (19/25 positive), Rostanga is attracted to hexane (non-polar) extracts (18/22).  Overall, the nudibranchs score about 80% positive selections.  The authors note that theirs is the first report of non-polar attractants being perceived by a carnivorous gastropod.  Ong & Penney 2001 Veliger 44: 99.

NOTE  also eaten are the red sponges Esperiopsis originalis and Plocamia karykina, from which carotenoid pigments are also sequestered

NOTE  the extracts are dried and set in small agar blocks to use in the Y-tube apparatus.  CONTROLS are a chunk of clean rock when whole sponge is tested and agar (plus solvent only) when extracts are tested

  black dot
 

Tochuina

  black dot
Research study 1
 

photograph of the nudibranch Tochuina tetraquetra crawing among its prey Gersemia rubiformis
In Humboldt County, California, Tochuina tetraquetra subsists almost solely on a diet of Gersemia rubiformis.  On contacting a colony of Gersemia the nudibranch spreads its oral veil and begins eating.  After a meal, which may take hours, an individual may rest for a day or so.  The feces of Tochuina in this area consist almost entirely of spicules of Gersemia.  Wicksten & DeMartini 1973 Veliger 15: 195.

  black dot
Research study 2
 
photograph of a nudibranch Tochuina tetraquetra close to its prey sea pen Ptilosarcus guerneyi Also favoured as food by Tochuina tetraquetra are sea pens Ptilosarcus gurneyi (Left) and other alcyonarians such as Alcyonium sp. (Right) photograph of the nudibranch Tochuina tetraquetra crawling on its prey Alcyonium sp.
  black dot
 

Triopha

  black dot
Research study 1
 

photograph of nudibranch Triopha catalinae
Around San Diego, California and perhaps elsewhere Triopha (carpenteri) catalinae eats several species of bryozoans.  McBeth 1971 Veliger 14: 158.

In the Punta Gorda region of northern California Triopha catalinae preys on arborescent bryozoans Scrupocellaria californica and foliaceous bryozoans Dendrobeania lichenoides.  Goddard 1987 Veliger 29: 267.

 

 

 

Triopha catalinae crawls near to, and perhaps eats, some bryozoans 3X

  black dot
Research study 2
 

photograph of nudibranch Triopha catalinaeStudies at San Diego, California show that colours of many nudibranchs, including the bryozoan-eating Triopha catalinae and the sponge-eating Anisodoris nobilis, Dendrodoris fulva, and Doriopsilla albopunctata are dietarily derived carotenoids. The carotenoids isolated from these and other species appear little changed from those in their foods; hence, the nudibranchs appear to lack the biochemical ability to modify carotenoid structures.  The author therefore concludes that nudibranchs tend to produce their striking colour patterns exclusively from the pigments available to them in their dietsMcBeth 1972 Comp Biochem Physiol 41B: 55.

NOTE  the main pigment in Triopha catalinae is an acetylene apo-carotenoid called triophaxanthin (C31H42O2)

NOTE  this subject is considered in more detail elsewhere in the ODYSSEY: NUDIBRANCHS & RELATIVES: DEFENSES AGAINST PREDATORS: SECONDARY METABOLITES

  black dot
Research study 3
 

photograph of two Triopha maculata feeding on encrusting bryozoans growing on a kelp frond courtesy Kevin Lee, Fullerton, CaliforniaTwo Triopha species, T. catalinae and T. maculata, are sometimes abundant intertidally at Asilomar Beach near Monterey, California.  Both species eat bryozoans and the question arises as to whether they compete for food.  Investigation, however, shows that T. maculata primarily eats 2 species of encrusting bryozoans, while T. catalinae primarily eats several species of arborescent bryozoans.   Correlative with these dietary differences are somewhat different radular structures and esophageal morphologies, suggestive of differing dietary specialisations.  On the basis of these observations, the authors suggest that significant competition for food does not occur.  Nybakken & Eastman 1977 Veliger 19: 279. Photo courtesy Kevin Lee, Fullerton, California diverkevin.

NOTE  lit. "like a tree" L.

 

Two Triopha maculata feed on encrusting bryozoans growing on a kelp frond 1X

  black dot
 

Tritonia

  black dot
Research study 1
 

photograph of nudibranch Tritonia festiva crawling on a prey octocoral Cryptophyton goddardi courtesy Jeff Goddard, CaliforniaAround La Jolla, California the tritoniid Tritonia festiva eats gorgoneans Lophogorgia chilensis.  The author has not observed feeding in the field (only in the laboratory), but has identified characteristic gorgonean spicules in gut contents and feces of field-collected Tritonia.  In Puget Sound T. festiva feeds mainly on sea pens Ptilosarcus gurneyi.  Gomez 1973 Veliger 16: 163.photograph of a nudibranch Tritonia festiva investigating a prey sea pen Ptilosarcus guerneyi

Tritonia festiva investigates a
partially withdrawn sea pen
Ptilosarcus gurneyi
0.6X

Juvenile Tritonia festiva crawls on the soft coral (octocoral) Cryptophyton goddardi, one of its several food species 1X. Photo courtesy Jeff Goddard, UC Santa Barbara and seaslugforum

  black dot
Research study 2
 

photograph of Tritonia festiva courtesy Ron Lon, SFU
In the Punta Gorda region of northern California Tritonia festiva eats and lives near the octocoral Clavularia sp. The accompanying photos show another food species of T. photographs of colonies of Alcyonium rudyi courtesy Jeff Goddard,
Californiafestiva in California, the octocoral Alcyonium rudyi.  Goddard 1987 Veliger 29: 267. Photo of T. festiva courtesy Ron Lon, SFU.

 


Several colonies of Alcyonium rudyi. INSET: close-up of a colony after being attacked by T. festiva. Note
the sucked-out polyp-holes.
Photo
courtesy Jeff Goddard, UC
Santa Barbara & seaslugforum

 

  black dot
Research study 3
 

photograph of nudibranch Tritonia diomedea courtesy Russ Wyeth and Owen Woodward.
Tritonia diomedea
favours flat mud-bottoms and in some areas feeds mainly on sea whips Virgularia sp.  Laboratory tests using Y-mazes show that the rhinophores are used to track the upstream locations of Virgularia.  If the rhinophores are incapacitated, then location of a prey Virgularia in the Y-maze is by chance.  Interestingly, loss of rhinophore sensory input does not affect the ability of Tritonia to orientate to a current.  Unlike in other nudibranch species, then, which are reported to use their rhinophores mainly for current perception, T. diomedea has other structures for this.  While preference for Virgularia is strong, preference for other cnidarians such as sea pens Ptilosarcus gurneyi and burrowing anemones Pachycerianthus fimbriatus is much less (about 25%).  Attack sequence on a prey Virgularia
is presented below. Time from bite-strike to beginning of ingestion is about 1sec.  Electrophysiological studies show that the buccal ganglia mediate feeding with some input from the cerebral ganglia. Willows 1978 Mar Behav Physiol 5: 115. Photo courtesy Russ Wyeth and Owen Woodward.

NOTE  this is done by tying off the rhinophore sheaths when the rhinophores are fully retracted, thus preventing extension into the current

drawing of nudibranch Tritonia diomedea approaching a prey sea whip Virgularia Willows 1978 Mar Behav Physiol 5: 115
When approaching Virgularia, Tritonia diomedea moves its head from side to side, and makes soft contact with its oral veil
drawing of nudibranch Tritonia diomedea contacting a prey sea whip Virgularia Willows 1978 Mar Behav Physiol 5: 115
On contact, the nudibranch centres on its prey, lifts its oral veil, and opens its mouth
drawing of nudibranch Tritonia diomedea making a bite strike at a prey sea whip Virgularia Willows 1978 Mar Behav Physiol 5: 115
Tritonia strikes rapidly with open jaws, and the radula pinches the stalk
drawing of nudibranch Tritonia diomedea breaking a prey sea whip Virgularia by use of jaws and radula Willows 1978 Mar Behav Physiol 5: 115
The jaws clamp shut. Combined radula rasping and jaw grinding cut the prey in half
drawing of nudibranch Tritonia diomedea ingesting a prey sea whip Virgularia Willows 1978 Mar Behav Physiol 5: 115
The prey is drawn into the gullet with cyclical ingestive movements, 5mm at a time
  black dot
Research study 4
 

drawing of a nudibranch Tritonia diomedea eating a sea whip Virgula Audesirk 1979 J Comp Physiol 130: 71drawing of sea whip Virgularia sp.Studies at Friday Harbor Laboratories, Washington show that feeding behaviour of Tritonia diomedea is mediated by a combination of mechanical and chemical cues perceived by receptors abundantly distributed around the mouth and oral veil.  The buccal mass, from the outside in, consists of lips, oral tube, jaws, and radula (see drawing on Right).  When the buccal mass is extended during biting, the soft oral tube is stretched tautly over the jaws, and the jaws are not visible.  The oral tube has major concentrations of mechanoreceptors. 

The major events of feeding on prey sea whips Virgularia sp. follows the pattern described in Research Study 3 above. The lips are inflated with hemolymph, and the buccal mass is photograph of Tritonia diomedea eating a sea whip Virgularia courtesy Audesirk 1979 J Comp Physiol 130: 71; Audesirk & Audesirk 1979 J Comp Physiol 130: 79.projected from the head with the jaws open and oral tube taut (see photo on Right). The radula extends through the open jaws to grip the prey and pull it into the mouth.  The jaws close and soft tissue of the prey is torn off by the radula and swallowed. The style (made of calcium carbonate) is shifted to the bottom of the mouth and forces applied, likely by the radula, to break it into pieces (see photo at Left). The pieces are swallowed and the cycle repeated.  A sea whip may be eaten in its entirety in one “sitting”. 

photograph of Tritonia diomedea eating a sea whip Virgularia courtesy Audesirk 1979 J Comp Physiol 130: 71; Audesirk & Audesirk 1979 J Comp Physiol 130: 79.Depending upon the order administered, chemical and mechanical cues elicit different responses.  For example, perfusion of sea-whip homogenate over and into the mouth elicits repeated biting.  Touch by a clean sea-whip style produces a combination of ingestive and egestive movements.  Finally, simultaneous application of both chemical and mechanical stimuli results in decreased frequency of biting, and increased frequency of swallowing.  The authors note that feeding is a complex series of events involving decision to bite, swallow, break, and ingest, based on a combination of stimuli.  Audesirk 1979 J Comp Physiol 130: 71; Audesirk & Audesirk 1979 J Comp Physiol 130: 79.

NOTE  the authors use a combination of direct observation of intact animals, and buccal mass-brain preparations with neurophysiological recordings to monitor responses of Tritonia to the different stimuli

  black dot
Research study 5
 

photograph of a colonly of soft coral Cryptophyton goddardi with a juvenile predator, the nudibrach Tritonia festiva courtesy Jeff Goddard, UC Santa Barbara photograph of aeolid nudibranch Tritonia festiva courtesy Jeff Goddard, UC Santa Barbara, CaliforniaStudies in Newport, Oregon show that aeolid nudibranchs Tritonia festiva prey on soft corals Discophyton rudyi. The predator senses its prey from up to 40cm distance, approaches until its oral veil just touches a polyp, then lunges repeatedly, using its jaws and radula to bite off polyps before they can retract into the protection of the spiculate colony mass.  An average attack lasts for less than 30sec, involves 2-4 lunges, and yields up to 12 polyps. Goddard 2006 Can J Zool 84: 66.

Colony of the alcyonium Cryptophyton goddardi
with a juvenile Tritonia festiva at the 7 o'clock
position. Tritonia reaches sizes of up to 10cm

 

  black dot
Research study 6
 

photograph of a nudibranch Tritonia diomedea approaching a prey sea pen Ptilosarcus gurneyii courtesy Russ Wyeth and Owen Woodward
Diets of Tritonia spp. in Puget Sound, Washington consist principally of sea pens Ptilosarcus gurneyi, and other cnidarians including sea whips Virgularia sp. and burrowing anemones Pachycerianthus fimbriatus.   The predators perceive their prey from scent carried in water currents to their chemosensory rhinophores.  Wyeth & Willows 2006 J Exp Biol 209: 1441.

 


 

 

Tritonia diomedea prepares for a bite-strike
on a sea pen Ptilosarcus guernyi 0.3X.
Photo
courtesy Russ Wyeth and Owen Woodward

  black dot
 
photograph of a nudibranch Tritonia diomedea approaching a prey sea pen Ptilosarcus gurneyii courtesy Russ Wyeth and Owen Woodward taken from a video

CLICK HERE to see a video of Tritonia diomedea attacking a prey sea pen Ptilosarcus gurneyi. As Ptilosarcus withdraws into its hole you will notice a torn portion of one of the leaves. Note also that following withdrawal of the prey, the predator seems slow to re-establish its location. Video courtesy Russ Wyeth and Owen Woodward.

NOTE  the video replays automatically

  black dot
  RETURN TO TOP