Effects of Nautilus in prolonged captivity

chrono_war01

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#1
The Aquarium staff is wondering about their Nautilus exhibit, their Nautiluses are feeling a bit moody lately and not really eating.

They're wondering how much do they actually do need to feed them, the vet says twice a day, a diet of deshelled shrimp and fish. However, the guys at a aquarium in Beijing says we should feed the crabs while a website (Don't remember which) suggests that they be fed once a month.
There's also some worrying black patches appearing on the shell, is this because they're falling ill or some other reason? They've tried scrubbing the shell gently with a toothbrush but the black patches are still there and a golden powder starting appearing. What is this?

Also, we're looking to ID the species (will provide photos later at some point)

Any help will be greatly appreciated.
 

DWhatley

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#2
Try PMing Robyn if she does not see this, I remember her posting on both feeding and the black spots but the search feature is not very happy right not.
 

cuttlegirl

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#3
What is the temperature of their water? They should not be deshelling the shrimp - Nautilus need the skeleton of the shrimp for calcium. Feeding twice a day seems like a lot for Nautilus. The black patches happen often in captivity (but it's not a good thing).
 

monty

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#4
I think Greg B has mentioned doing some work to figure out what the black stuff is; I forget the results, though. In Greg and Adam's article in TFH, they say:

The most common food offered to nautiluses in captivity is shrimp (with shell), squid, various types of frozen fish, and blue crab. Several types of molts, such as lobster molts, have also been fed as enrichment food. The lobster molt is taken quickly and consumed with no problems (molts are also a great source of calcium).
and

A common and still misunderstood issue with captive nautiluses is aberrations of the shell. Over time, the shell does not grow normally and begins to degrade. Signs of this are black edging of the newly formed shell. There appears to be no adverse health issues associated with the shell malformation, and to date it is merely an aesthetic problem.
Unfortunately, their article doesn't appear to be archived on the web; it's from Tropical Fish Hobbyist June 2007 vol LV Number 10 #615. It's a pretty short article, though, so you can probably get all the info in it from asking here...
 

chrono_war01

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#5
Thanks guys, I'll be heading off to work and then dutifully reporting this to my boss.
 

robyn

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#6
I concur with all the advice offered here: Nautilus is an opportunistic scavenger with a low metabolic rate - they really don't need to be fed so frequently. I fed mine on one unpeeled, de-headed shrimp every four days or so. Even when the food was dropped (we hand-fed) it often wasn't eaten, so I doubt I was under-feeding. What is the water temperature? Warmer temps probably mean more frequent feeding may be needed. My tanks were at 15-17 degrees C.

Are the black patches you mention radiating back from the growing edge of the shell? In my experience this blackened new growth can result from overfeeding or from feeding a suboptimal diet. (the shell advances forward rapidly before it thickens, and begins to crack and splinter.) Are the fish being used as food a marine species? Freshwater fish are not as good as marine. Definitely see if you can switch their diet to shrimp with shells on - they need the calcium for proper shell formation.

The gold dust you mention may be very fine shell splinters or, more likely from your description, some of the periostracum that covers the shell. This is a natural part of the shell and shouldn't need to be removed, but I don't think removing it would do any damage. Others might have more info on that though.

Can we see pictures? I love seeing Nautilus pics! And maybe we can help with an id, too.
 

Thales

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#7
robyn;158078 said:
I concur with all the advice offered here: Nautilus is an opportunistic scavenger with a low metabolic rate - they really don't need to be fed so frequently. I fed mine on one unpeeled, de-headed shrimp every four days or so. Even when the food was dropped (we hand-fed) it often wasn't eaten, so I doubt I was under-feeding. What is the water temperature? Warmer temps probably mean more frequent feeding may be needed. My tanks were at 15-17 degrees C.

Are the black patches you mention radiating back from the growing edge of the shell? In my experience this blackened new growth can result from overfeeding or from feeding a suboptimal diet. (the shell advances forward rapidly before it thickens, and begins to crack and splinter.) Are the fish being used as food a marine species? Freshwater fish are not as good as marine. Definitely see if you can switch their diet to shrimp with shells on - they need the calcium for proper shell formation.

The gold dust you mention may be very fine shell splinters or, more likely from your description, some of the periostracum that covers the shell. This is a natural part of the shell and shouldn't need to be removed, but I don't think removing it would do any damage. Others might have more info on that though.

Can we see pictures? I love seeing Nautilus pics! And maybe we can help with an id, too.
+1
 

DWhatley

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#8
Understanding irregular shell formation of Nautilus in aquaria: Chemical composition and structural analysis
Mehdi Moini, Aoife O'Halloran, Alan M. Peters, Christine A.M. France, Edward P. Vicenzi, Tamsen G. DeWitt, Esther Langan, Tim Walsh, Robert J. Speakman 2014 (subscription)

Irregular shell formation and black lines on the outside of live chambered nautilus shells have been observed in all adult specimens at aquariums and zoos soon after the organisms enter aquaria. Black lines have also been observed in wild animals at sites of broken shell, but continued growth from that point returns to a normal, smooth structure. In contrast, rough irregular deposition of shell continues throughout residence in aquaria. The composition and reasons for deposition of the black material and mitigation of this irregular shell formation is the subject of the current study. A variety of analytical techniques were used, including stable isotope mass spectrometry (SI-MS), inductively coupled plasma mass spectrometry (ICP-MS), micro x-ray fluorescence (µXRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM) based X-ray microanalysis. Results indicate that the black material contains excess amounts of copper, zinc, and bromine which are unrelated to the Nautilus diet. The combination of these elements and proteins plays an important role in shell formation, growth, and strengthening. Further study will be needed to compare the proteomics of the shell under aquaria versus natural wild environments. The question remains as to whether the occurrence of the black lines indicates normal healing followed by growth irregularities that are caused by stress from chemical or environmental conditions. In this paper we begin to address this question by examining elemental and isotopic differences of Nautilus diet and salt water. The atomic composition and light stable isotopic ratios of the Nautilus shell formed in aquaria verses wild conditions are presented. Zoo Biol. 9999:1–10, 2014. © 2014 Wiley Periodicals, Inc.
 

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