Foods, feeding, & growth
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Preferred foods, feeding ecology, & growth: genera D-G

 

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 these sections:
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA A-C,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA H-M,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA N-P,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: GENERA R-T,
PREFERRED FOODS FEEDING ECOLOGY & GROWTH: SACOGLOSSANS, and INGESTIVE CONDITIONING

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Dendronotus

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Research study 1
 

photograph of aeolid nudibranch Dendronotus rufus courtesy Jan Kocian, Washington
photograph of aeolid nudibranch Dendronotus irisMost species of Dendronotus feed on hydroids.  Two exceptions are D. iris (photo on Left) which feeds on burrowing anemones, and D. rufus which apparently favours jellyfish scyphistomae when it can get them.  Robilliard 1970 Veliger 12: 433. Photo courtesy Jan Kocian, Washington and seaslugforum.


Dendronotus iris 0.2X

 

Dendronotus rufus 0.3X

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Research study 2
 

photograph of burrowing anemone Pachycerianthus fimbriatus
photograph of radula of nudibranch Dendronotus iris courtesy modified from Shaw 1991 Can J Zool 69: 2805.photograph of biting edge of jaw of nudibranch Dendronotus iris modified from Shaw 1991 Can J Zool 69: 2805.Dendronotus iris
is one of the largest opisthobranchs on the west coast, reaching sizes of up to 30cm in length.  It generally inhabits sand/mud bottoms where it feeds almost exclusively on burrowing anemones Pachycerianthus spp.  Two studies at Friday Harbor Laboratories, Washington and Bamfield Marine Sciences Centre, British Columbia provide details on its feeding behaviour.  On contact with the anemone’s tube, Dendronotus rises up, and waves its head back and forth.  When it touches the anemone's tentacle its head withdraws momentarily, then extends and waves back and forth in ever-decreasing arcs as it homes in on its prey.  This manouvre centres the head for the attack to follow.  Dendronotus then rears back and rapidly lunges at the anemone with its buccal mass extended well beyond the mouth opening. 

The jaws grasp one or more tentacles, the radula moves upwards and pulls the tentacles past the serrated edges of the jaws, and the tentacles are severed. The tentacle bits are pulled into the mouth by radular movements and swallowed.

It takes about 1min for Dendronotus to position itself, centre its head, and lunge.  The first strike may be followed by repeated lunges down the anemone’s tube.  Although not noted by either author the anemone’s quick withdrawal into its tube may aid in severing the tentacles caught up in the nudibranch’s radula and jaws.  Robilliard 1970 Veliger 12: 433; photos of radula and jaw modified from Shaw 1991 Can J Zool 69: 2805.

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Research study 3
 

photograph of Dendronotus iris crawling up the tube of a burrowing anemone Pachycerianthus fimbriatus in order to attack it courtesy Wobber 1970 Veliger 12: 383

An earlier publication also provides a good description of Dendronotus iris eating Pachycerianthus sp. in Monterey Bay.  There are several feeding modes: 1) an individual (usually small-sized) may crawl up the tube and slowly enter the ring of marginal tentacles.  If the anemone pulls down into its tube, a Dendronotus may follow it down and feed for several minutes or hours; 2) a Dendronotus (usually larger sized ones) will bite firmly with jaws and radula and, when the prey pulls down, the predator is dragged down the tube where it feeds for a time; and, 3) a Dendronotus may crawl down an open tube to feed.  An isolated tentacle of Pachycerianthus dangled in front of and in contact with a crawling Dendronotus will elicit a bite-strike just as though an intact anemone had been encountered.  Interestingly, if a Dendronotus is guided onto the tentacles of an anemone Urticina sp. by a SCUBA-diver, the opisthobranch may be pulled in and eaten. In contrast, the nematocysts of Pachycerianthus appear to offer little or no defense.  The only defense appears to be a passive one, where if the anemone pulls in and the soft tube collapses in on itself, the predator may be prevented from entering.  In that the tentacles are rarely eaten in their entirety and those that are eaten usually regenerate within a few days, the 2 species appear to coexist in kind of a host-parasite relationship.  Wobber 1970 Veliger 12: 383.

NOTE this description is applied commonly to predators that graze on their prey rather than eat them up (for example, herbivorous species); the use of the expression "host-parasite" by authors may be more for novelty than an attempt to be strictly scientific

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photograph of a nudibranch Dendronotus iris attacking a burrowing anemone Pachycerianthus fimbriatus taken from a video

CLICK HERE to see a video of 2 different individuals of Dendrontous iris vigorously attacking a favoured prey, the burrowing anemone Pachycerianthus fimbriatus. Although it's hard to see, in both cases the prey anemone appears to withdraw without loss of a tentacle.

NOTE  the video replays automatically

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Research study 4
  photograph of the radula of a nudibranch Dendrontotus frondosus courtesy Lambert 1991 Biol Bull 181: 248photograph of a nudibranch Dendronotus frondosus courtesy Kevin Lee, Fullerton, California
Dendronotus frondosus
ranges in size from 5-10cm.  It eats hydroids: Tubularia, Sertularia, and many other genera.  As it hunts it may withdraw on contact with the stinging cells of its prey, then home in, envelop the polyp with its mouth, and chop it free of its stalk with jaws and radula (photo on Right). Small-sized Dendronotus (<5mm body length) may create a hole in the hydroid’s perisarc and insert its radula.  Robilliard 1970 Veliger 12: 433. Radula photo from Lambert 1991 Biol Bull 181: 248. Colour photo of D. frondosus courtesy Kevin Lee, Fullerton, California diverkevin.
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Diaulula

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Research study 1
 

photograph of Diaulula sandiegensis with eggsA study at the Bamfield Marine Sciences Centre, British Columbia shows that Diaulula sandiegensis eats several species of sponges in Barkley Sound, with a preference for Myxilla incrustans and to some extent Hamacantha hyalodermaPenney 2013 J Moll Stud 79: 64.

 

 

 

Diaulula sandiegensis with an egg mass, possibly its own. The polyps are
a colony of corallimorpharian Corynactis californica - not a usual habitat
for this nudibranch species, but visible beneath its foot appears to be a patch
of yellow sponge, perhaps edible and perhaps explaining its presence there 0.6X

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Dirona

 

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Research study 1

 

photograph of a nudibranch Dirona albolineata crawling on some of itd prey bryozoansOnly a few nudibranchs feed on molluscs, and those that do tend to eat other opisthobranchs.  Dirona albolineata is unusual, then, in preying on at least 3 species of shelled snails, Lacuna carinata, Pupillaria pupillus, and Margarites helicinus in addition to bryozoans.  Analysis of feces from 31 Dirona at Friday Harbor Laboratories, Washington reveals the presence of opercula and shell fragments from Lacuna in all 31, from Pupillaria in 4, and from Margarites in 5.  Additionally, shell plates of barnacles Balanus sp. are noted in the feces of one Dirona, a byssus thread from a scallop Chlamys (1/31), parts of a hydroid Aglaeophenia (1/31), and bivalve shells and bryozoan tests (4/31).  Does Dirona have a preference for one snail over another?  Yes. Laboratory preference tests show that Lacuna is selected 79% of the times versus 14% for Margarites and 7% for Pupillaria.  A Dirona of 7cm body length can consume 5 Lacuna and most of a Margarites in a day.  Because other regions of the digestive tract are soft, the author assumes that the jaws and powerful muscles of the buccal mass crush the shells.  Robilliard 1971 Pac Sci 25: 429.

Dirona albolineata crawling on growths of bryozoans 0.5X

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Research study 2
 


photograph of a nudibranch Dirona picta courtesy Jeff Goddard, Santa Barbara, California
In the Punta Gorda region of northern California Dirona picta lives on and eats the arborescent bryozoan Scrupocellaria californica.  Goddard 1987 Veliger 29: 267. Photo courtesy Jeff Goddard, Santa Barbara, California and seaslugforum.

 

 

 


Dirona picta crawling on its prey bryozoan Scrupocellaria californica 1.5X

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Research study 3
 

MORE WEST-COAST NUDIBRANCHS EATING BRYOZOANS and OTHER ENCRUSTING INVERTEBRATES (top row, L. TO R.):

Polycera atra eating the encrusting Membranipora sp. Photo courtesy Kevin Lee, Fullerton, California .diverkevin

Polycera atra eating the arborescent bryozoan Bugula sp. Photo courtesy Kevin Lee, Fullerton, California diverkevin

photograph of 2 nudibranchs Polycera atra eating bryozoans Membranipora sp. courtesy Kevin Lee, Fullerton, California photograph of a nudibranch Polycera atra eating the bryozoand Bugula sp. courtesy Kevin Lee, Fullerton, California
photograph of a nudibranch Flabellina triophina crawling on a bryozoan
photograph of a nudibranch Dirona albolineata crawling on a colonial phoronid Phoronis ijima

BOTTOM ROW (L. to R.):

Flabellina triophina crawls on an unidentified bryozoan 1.3X

Dirona albolineata crawling on and perhaps eating the colonial phoronid Phoronis ijimai 1X

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Doris

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Research study 1
 


photograph of a nudibranch Doris montereyensis with its egg ribbon

photograph of several nudibranchs Doris odhneriSponges are eaten by many nudibranch species, including the Doris spp. shown here and the 3 species shown below.  No matter how strong a fidelity to sponges, however, most spongivorous species include other bottom-dwelling prey such as bryozoans in their diets.  Cook 1962 Veliger 4: 194; Bloom 1976 Veliger 18: 289; Elvin 1977 Veliger 19: 194; Bloom 1981 Oecologia 49: 305.


Doris odhneri 0.4X

 

 

Doris montereyensis with egg ribbon 0.8X


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Research study 2
 

In a study at the Bamfield Marine Sciences Centre, British Columbia a researcher claims that “Doris montereyensis… consumed one species almost exclusively…” in Barkley Sound, bu tthe tabulated data actually indicate that 9 individuals spread their dietary preferences among 6 species of sponges, which does not support the claim. Penney 2013 J Moll Stud 79: 64.

NOTE  the author makes a similar claim for Doris odhneri in the same study. In this case, of 14 individuals whose diet can be indentified at 3 sites, 7 eat Halichondria panicea and 7 spread their attentions among 4 other species; again, results not matching the author’s claim

   
  Other sponge-eating dorid nudibranchs (refer to their generic listings in these food sections for more information:
 
photograph of dorid nudibranch Cadlina luteomarginata courtesy Paul Young
Cadlina luteomarginata 1X. Photo courtesy Paul Young and the seaslugforum
photograph of 2 nudibranchs Diaulula sandiegensis copulating among a growth of sponge
Diaulula sandiegensis copulating among a growth of sponge, possibly a prey species 0.8

A pair of sponge-eating Peltodoris (Anisodoris) nobilis engaged in copulatory behaviour
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Fiona

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Research study 1
 

photograph of nudibranch of Fiona pinnata courtesy seaslugforum.netphotograph of goose barnacles Lepas sp. Although essentially pelagic, the nudibranch Fiona pinnata may be found on flotsam in nearshore areas or stranded on the shore with its prey barnacle Lepas anatifera.  Fiona attacks its prey at the upper part of the peduncle (stalk).  The jaws hold the tissue while the radula scrapes a hole.  At this time the barnacle may twist back and forth to dislodge the predator.  When the peduncle is breached, a toxin must be released because the barnacle relaxes and gapes its valves.  Fiona then enters between the tergal and scutal plates and begins to feed.  In laboratory tests Fiona does not eat the goose barnacle Pollicipes polymerus, nor does it eat dead Lepas.  Growth is fast on a diet of the barnacle, with a 900% increase in live mass being evidenced over a 24-d period.  Holleman 1972 Veliger 15: 142. Photo of Fiona pinnata courtesy Bill Rudman, Australia seaslugforum

 

 

Lepas sp. 0.5X

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Flabellina (Coryphella)
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Research study 1
 

photograph of aeolid nudibranch Flabellina verrucosaWest-coast specimens of Flabellina verrucosa  are reported to eat a wide variety of hydroids.  In Massachusetts (if it is the same species) it is noted to feed on the ascidean Botryllus schlosseri.  Morse 1969 The Nautilus 83: 37.

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Geitodoris & other dorids

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Research study 1
 

photograph of dorid nudibranch Geitodoris heathi courtesy Jeff Goddard, Santa Barbarahistogram of distribution of 6 species of dorid nudibranchs in the San Juan Islands, Washington showing depths inhabited and type of digestive systemResearch studies at Friday Harbor Laboratories, Washington show that sponge prey are partitioned along a gradient of skeletal structure between 2 guilds of dorid nudibranchs – on the one hand, a guild that has feeding and digestive adaptations suited to poorly-organised skeletons (caecate) and, on the other, a guild suited to eating sponges with well-organised skeletons (acaecate).  Species co-occurring at specific depths tend to partition the food resources based on type of skeleton. For example, Doris montereyensis and Diaulula sandiegensis, share an intertidal habitat but, while the former specialises on Halichondria panicea, a species with a poorly-organised skeleton, Diaulula sandiegensis eats somewhat more of Haliclona permollis and Myxilla incrustans, sponges with more well-organised skeletons.  Where several dorids share the same habitats, their foods tend to be partitioned within each guild (see accompanying histogram).  Measurements of food-conversion efficiencies of an individual dorid species on different sponges show that growth rates tend to be highest on the “guild-specialised” foods, even though as just much of other sponge species may be consumed.  The study, which is a good one, shows that food resources are partitioned by the dorids, not from competitive interactions, but from self-stabilising feeding and digestive specialisations.  Bloom 1981 Oecologia 49: 305. Photo courtesy Jeff Goddard, UC Santa Barbara and seaslugforum. Photos of the other species used in this Research Study can be found in PREFERRED FOODS, FEEDING ECOLOGY, & Growth: GENERA A-D.

NOTE a “poorly-organised skeleton” is one in which the spongin fibers and spicules are independent of one another (e.g., Halichondria).  The challenge here for the nudibranch is to pass the spicules through the digestive tract without harming its gut lining.  Dorids eating this type of diet have radulae with fine cusps, a cecum in the floor of the stomach which packages the loose spicules into mucous ropes, and a ciliated intestine.  A “well-organised skeleton” is one in which the spongin and spicules are bound in interconnected ropes (e.g., Myxilla and Mycale).  Here the challenge is to break apart the spicule-mucus ropes mechanically to get at the digestible soft cellular material.  Dorids eating this type of diet tend to have large-cusped radulae, stomachs without ceca, and a muscular intestine that moves material peristaltically.  These represent 2 distinct guilds of sponge-eating dorids

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