That Fish Blog – Aquarium Advice and Information

Please welcome back Patty Little to That Fish Blog. Patty has previously written such articles as Water Gardening in Natural Ponds & Preparing Your Pond Plants After Winter. Please welcome Patty Back to That Fish Blog.

As aquarists, we may find ourselves in a constant quest to find the next unique and interesting creature to enhance our underwater display.   We may not always consider shrimp when we ponder species to add, but if you’re looking for something new, particularly if you have a planted community, freshwater shrimp species may be just what you’re looking for.  Shrimp are not only fun to observe, but in many cases they serve as efficient cleaners.

There are several species of freshwater shrimp offered commonly in the aquarium hobby, some more often than others.  Let me introduce you to the first two species you may encounter in your quest.  I’ll talk about some others in my future blogs.

Ghost Shrimp

Ghost shrimp, aka glass shrimp, are probably the most common shrimp offered in the trade, but they are usually offered as a live food source or treat for predators, both marine and freshwater.   These guys are terrific additions to the home aquarium, as they serve as scavengers as well as consumers of soft algae on rock, wood, and other surfaces.  These shrimp, Palaeomonetes sp., are hardy, inexpensive, and low maintenance.  They are virtually translucent, though some may be slightly more opaque with a hint of white or green to their exoskeleton, and a small orange or yellow dot adorns the tail.  The contents of their stomach, or at least the color of their last meal is quite visible.  They have ten pairs of legs, the front 2 tipped with small claws for feeding. Ghost shrimp grow to about 2 inches, and they tend to grow quickly.
They do not tend to have long lives, maybe about a year or so.  Be sure to ask your source if they are housed in freshwater, as there are some species that are brackish or marine, and will not tolerate full freshwater for extended periods. Otherwise, they are fairly undemanding.  They prefer a clean environment with low to neutral Ph, and temperatures ranging from the low 60’s to the mid 80’s.  They like plenty of cover like plants and caves, and will be perfectly happy scavenging leftover flake food and algae.  Ghost Shrimp can be housed in groups or singly in smaller tanks, and they can be housed with peaceful community fish, particularly small tank mates like tetras, rasboras, and other non-predatory fish.

Amano Shrimp

Amano Shrimp, sometimes offered as Japanese Marsh Shrimp or Yamoto Numa-Ebi, were introduced and popularized by Takashi Amano, whose planted aquaria are world renowned.  These little shrimp are about 2 inches at maturity, and are prized by aquarists with planted tanks for their algae-eating habits.  Algae and decaying plant matter is their primary diet, though as with most shrimp, they will greedily eat flake food when offered, and may eat some soft plants like java moss if algae is in short supply.  They are attractive shrimp, with light brown bodies and a tan stripe down the middle of the back.  They have reddish-brown markings along their sides.  They are relatively long lived, and absolutely safe in community environments.
Amano Shrimp are not tolerant of ammonia, nitrate, and nitrite levels, and the aquarium housing them must be well maintained.  They prefer a Ph of 6.0-7.5 and temps from the high 50’s to the high 70’s.  If your algae issue is significant, feed flakes sparingly to steer them to the soft algae.  They will not be successful with tougher algae like spot algae and the infamous Black Brush Algea.

Thanks for the great article Patty,

Until next time,

Dave

Surprising new information about aquatic invertebrates is uncovered every day…the following is a small sample, which I’ll add to from time to time.  Please see Part I of this article as well.

Good and Bad Pets

The venom of the tiny blue-ringed octopus, Hapalochlaena maculosa, is one of the most toxic known, with the amount delivered in a single bite being sufficient to kill an adult person.  Yet this creature occasionally appears for sale in the pet trade – learn to identify and avoid it!

Giant water bugs (Family Belostomatidae) can be collected throughout the USA and make interesting, if aggressive (they can inflict a painful bite), aquarium subjects. The males of many species carry the eggs about on their backs.  A species I collected in Venezuela topped 4 inches in length, and regularly consumed small frogs.  Another I came across at Japan’s Kaiyukan Aquarium easily subdued a 3 inch long minnow.  Please look for my future article on aquatic insects.

Most corals rely upon minute creatures for their food and are difficult to maintain in aquariums.  However, tooth coral (Cynarina spp.) accept pieces of shrimp and other large food items, and should be considered as a first choice by those new to coral-keeping.

Jellyfishes are not usually available in the pet trade, and are quite delicate in captivity.  One exception is the upside-down jellyfish, Cassiopeia andromeda.  In contrast to all others, it rarely swims but rather rests in a “head down” position, with the tentacles trailing above.  Given intense lighting (it relies upon symbiotic algae) and plenty of brine shrimp, it often thrives in the aquarium.

Catching and Storing Food

Surprisingly, some spiders have adopted an aquatic lifestyle, and several of these adapt well to aquarium life. North America’s fishing spiders, Dolomedes spp., float on the water’s surface and dangle a leg below to lure small fish within reach.  The European diving bell spider, Argyroneta aquatica, takes aquatic life a step further – it lives in a submerged, air-filled retreat from which it launches attacks on passing fish and invertebrates.  Please look for my future article on these unusual creatures.

Several crabs have interesting ways of “planning for the future”.  Atlantic spider crabs, Libinia emarginata, stuff marine algae into crevices on their shells, effectively camouflaging themselves and storing food at the same time (those I have kept abandon this habit when they reach 3 inches in size).  The ever-popular arrow crab, Sterorhynchus seticornis, impales bits of food, to be consumed in the future, on the pointed end of its carapace.

How Big…How Old?

Crabs, lobsters and their relatives (Order Decapoda) are among the most important aquarium and food-trade invertebrates.  The legs of the Japanese spider crab, Macrocheira kaempferi, the largest of the group, may span 13 feet.  Both it and the American lobster, Homarus americanus (at 60+ pounds, the heaviest Decapod) may live for 100 years. The largest freshwater species is the 9 pound New Zealand crayfish, Astacopsis gouldi.

At 4.5 feet across and up to 750 pounds in weight, the South Pacific’s giant clam, Tridacna gigas, is the largest of the world’s 6,000+ bivalves (clams, oysters and relatives).  It relies upon commensal green algae for much of its food, and produces the world’s largest pearls – one of which weighed in at 14 pounds!

Many mollusks (snails, clams and their relatives) lay down growth rings, which appear as irregularly-spaced lines on the shell.  Much as with trees and turtles, these lines can often be used to determine these creatures’ ages.

Defense and Survival

Although largely aquatic, several species of North American crayfish, known as chimney crayfish, exploit terrestrial habitats.  They live in wet meadows and dig tunnels, which may exceed 10 feet in length, to the water table.  Recently, it was discovered that these water-filled retreats provide vital breeding sites for salamanders during droughts.

Sea urchins are interesting aquarium inhabitants, but most aquarists find them rather unresponsive.  However, they react immediately to the shadow thrown by a hand or other object passing overhead by orienting their spines towards the disturbance.  This is a defensive reaction, designed to direct the sharp spines towards an oncoming fish or other predator.

I look forward to hearing about your own observations concerning aquatic invertebrates, and to answering your questions.  Thanks…until next time, Frank.

A great deal of interesting information concerning marine, fresh water and terrestrial in invertebrates of the Pacific Basin is available at the following web site:

http://pbin.nbii.gov/marinverts/index.asp

Knowing where to start and stop when it comes to writing about invertebrates is a real problem – any single group could keep one occupied for a lifetime. Today I’d like to highlight some interesting facts concerning a few commonly kept types and their relatives. I’ll add to this from time to time.

General
Invertebrates (animals without backbones) account for approximately 97% of the world’s animal species, yet we have no idea of their total numbers. The smallest are invisible to the naked eye while the largest, giant squid, may exceed 60 feet in length.

Nearly every injectable drug manufactured in the USA is tested for bacterial contamination with a chemical extracted from horseshoe crab blood (synthetics do not work as well). Several states are restricting the collection of these animals (often used as fertilizer!) and requiring that they be released after blood specimens are taken.

Invertebrates have colonized every habitat imaginable, from freezing Antarctic seas to the boiling hot water of geysers. The sponges, crabs, tubeworms and others living near deep sea vents form the only animal community that does not rely upon photosynthesis as the basis of the food chain (bacteria that consume methane function as “plants”).

Despite being a creature of legend for centuries, the giant squid, Architeuthis sp., was not captured on film until 2004. Two years later, the same Japanese scientists that filmed the animal caught a specimen on a fishing line, thus giving the world its first view of a living giant squid.

Eating and Being Eaten
Despite radically different appearances, jellyfishes, sea anemones and corals are closely related (Phylum Cnideria). All gather food and excrete wastes through a common opening, and overcome their prey with stinging cells.

Jellyfish, although comprised largely (95%) of water, are able to snare prey as large as small fishes. Surprisingly, they form the bulk of the diet of many huge sea creatures, including the world’s biggest turtle, the leatherback.

The dried krill (shrimp-like creatures of the Class Brachiopoda) that you may use as fish food form the basis of the food chain in most of the world’s oceans. Also, a number of surprisingly large creatures, including whales, manta rays and basking sharks, rely upon krill as their primary diet, consuming billions each day.

Although viewed by most as sluggish creatures, many of the world’s 70,000+ species of snails and slugs (Phylum Mollusca) are quite effective predators. Various types pry open or drill through clam shells and cone snails impale fish by shooting out barbed tongues. Certain sea slugs consume anemones and incorporate the stinging cells into their own gill tufts.

Reproduction
Australia’s Great Barrier Reef, the world’s largest, is 1,250 miles long. Somehow, its untold billions of individual coral animals synchronize reproduction so that the sperm and eggs of all are released into the sea at the same time.

Banded coral shrimps, Stenopus hispidus, form long-term pair bonds, and males have been observed to share food with gravid (pregnant) females. The eggs, which are glued to the females’ swimmerets (feathery structures below her abdomen), are aerated and protected by her. Upon hatching, however, the young may be consumed by both parents!

Surviving
Sea cucumbers make interesting if occasionally unsettling aquarium inhabitants – when disturbed, they discharge their stomachs through the anus! Amazingly, these sea star relatives can regenerate the discarded stomach.

The unique tube feet of sea stars (Phylum Echinodermata) function in locomotion, respiration and as sensory organs. Water-filled canals linking the feet can, via a series of valves, build up enough pressure to enable sea stars to pry open clam shells (try that with your hands!).

The anemone hermit crab, Parurus prideauxi, places a stinging sea anemone on its shell as protection and camouflage and re-locates it when changing shells. The anemone, in turn, gets a safe anchoring place and, perhaps, access to leftovers from the crab’s meals.

Using Invertebrates – Now and Then
Over 10,000 species of sponges (Phylum Porifora) inhabit both fresh and salt water. Several types have been collected from the Mediterranean Sea since ancient times. After drying in the sun, their fibrous structural tissue (spongin) made an excellent bath sponge.

Horseshoe crabs (Phylum Chelicerata) are among the world’s most ancient creatures and have remained relatively unchanged for over 300 million years. Closely related to spiders and not crabs at all, small specimens make interesting additions to a marine aquarium.

And, Finally…An Odd Personal Tale
Octopuses (Class Cephalopoda) are the most intelligent of the invertebrates and make fascinating aquarium subjects. They are also quite well-sighted – one I kept would, according to my grandmother, “stare” at her while she worked in the kitchen. Not wishing to upset my beloved pet, she covered its tank when preparing octopus for dinner!

Well, only a few billion more facts to go! I’ll continue next week, and periodically after that. As there are so many possibilities, I would greatly appreciate your suggestions concerning invertebrate-oriented subjects that you may wish to learn more about. Thanks, until next time, Frank.

You can learn a great deal about invertebrate biology at the web site of the Australian Museum:
http://www.amonline.net.au/invertebrates/ara/index.htm

Only distantly related to shrimp, these unique, aggressive predators are actually classified within their own order, Stomatopoda. Over 400 species are known, mostly from the Indian and South Pacific Oceans. Hobbyists are often surprised to learn that one species, the 10 inch long Squilla empusa, ranges along our Atlantic Coast is for north as Cape Cod.

A flurry of new research articles on these fascinating creatures has been published recently, and it turns out that they are even more unusual than we might have suspected. I’d like to summarize some of this new information here — in my next article, I’ll write about caring for mantis shrimp in captivity.

A New and Unique Visual System
Research completed at the University of Queensland, Australia, in March of this year has demonstrated that mantis shrimp have a vision system previously unknown in any other type of animal. Utilizing precisely tilted filters in their eyes, mantis shrimp are able to perceive circular polarized light (CPL) by converted it to a linear form. CPL spirals to the left or right, and appears only as “haze” to us and other creatures (hence the need for polarized sunglasses). The filter within the mantis shrimps’ eyes functions in a similar manner to those used in certain photographic processes – only they beat us to it by about 400 million years!

CPL is reflected by male mantis shrimps’ exoskeletons, leading researchers to believe that it is used for sexual signaling. Furthermore – squid, a major mantis shrimp predator, can detect linear polarized light but not CPL. The use of CPL may, therefore, represent an ingenious strategy by which the mantis shrimp can communicate without drawing the attention of their enemies.

The World’s Most Complex Eyes
Further research in May of this year revealed that mantis shrimp possess the Animal Kingdom’s most complex eyes. Their eyes contain ten pigments sensitive to different light wavelengths, as opposed to our own three pigments. In addition to detecting CPL, mantis shrimp can also see colors ranging from ultraviolet through infrared – far more than any other creature.

Although we have yet to understand all the reasons for the evolution of such a remarkable visual system, we have some hints. Certain of the mantis shrimps’ prey, such as sand shrimp, are transparent and very difficult to see underwater. However, these shrimp are full of sugars that reflect polarized light – making them easy targets for the mantis shrimp. As if all this were not enough, mantis shrimp can also rotate each eye independently of the other, allowing for a very wide circle of vision.

Splitting Thumbs and Shattering Glass
Of more immediate concern to marine aquarists is a recent study demonstrating that a common pet trade species, the peacock mantis shrimp, can extend its hard, club-shaped front legs at speeds of over 75 feet per second. This is the fastest kick known, and explains the why we sometimes find aquariums housing mantis shrimp shattered, and a flood on the floor – the odd creatures actually generate enough force to break glass! In fact, so much pressure is exerted that the exoskeleton at the back of the leg actually wears away over time, but is replaced when the mantis shrimp molts.

This mighty thrust is made possible by a unique hinge in the leg, and was analyzed after being recorded by a camera capable of operating at 100,000 frames per second. The deadly front legs allow mantis shrimp to crack the shells of the snails and crabs upon which they feed, and to defend themselves — indeed, divers long ago christened these colorful terrors “Thumb Splitters”.

Communicating via Florescence
Although many marine creatures fluoresce (absorb one color and emit it as another), mantis shrimp are the only ones known to use fluorescence as a means of communication. This month (May, 2008) researchers at the University of North Carolina demonstrated that the bright yellow spots of the species Lysiosquillina glabriuscula were visible even at depths of over 130 feet, allowing the animals to signal each other despite the dim blue light (which would otherwise render the yellow color indistinct).

Last but not least (“last” for now, I’m sure these oddballs are hiding other secrets!) – certain species of mantis shrimp cover ground by curling into a ball and rolling downhill.

On to captive care next time – until then, please share your own observations and questions. Thanks, Frank.

A video showing just how well a pugnacious mantis shrimp can use its kicking ability is posted at:
http://www.youtube.com/watch?v=Tt55yPxTxyA&feature=related

Seahorses have much to attract aquarists – armor plated and prehensile tailed, and with independently-moving eyes and wing-like fins, they can also change color as well as grow and discard filamentous appendages. And, of course, the males become “pregnant”.

My first contact with seahorses came in the mid 1960’s when my grandfather, long in awe of these unusual fishes, mail-ordered a group of dwarf seahorses, Hippocampus zosterae, from a dealer in Florida. The shipment included several males carrying eggs, and I was hooked – so much so that I wound up writing a book on seahorses.

Texas A&M researchers are now learning the male seahorse’s pouch is far more than a mere container for eggs, and are trying to discover just how such a unique organ managed to evolve. Tissue from within the pouch actually grows around the eggs and functions in a similar manner to a mammalian placenta. Through it the seahorse father is able to keep blood flowing around the eggs, and to provide them with oxygen and nutrition. Amazingly, he also makes minute adjustments to the salinity of the water within his pouch, gradually increasing it as the embryos’ needs change. By hatching time, the salinity of the pouch water matches precisely the salinity of the surrounding ocean.

The male seahorse fertilizes the eggs once they have been deposited into his pouch by the female. From that point on, the reproductive roles of the sexes are reversed. The researchers at Texas A&M are also looking into the effect this has had on mate selection and other aspects of seahorse reproductive behavior. In certain species of pipefish (close relatives of the seahorses) females have the bright coloration usually associated with male fishes, and they compete for access to the egg-incubating males. Seahorses are, as far as we know, monogamous. They form long-term pair bonds which are reinforced, in many species, with daily “greeting” rituals (the pair clasps tails, swims together, etc.), but much about how role-reversal has affected mate selection is unknown.

In other related news, the Georgia Aquarium has announced that one of its male weedy seadragons is carrying eggs, only the third time such has been recorded in a US aquarium. Weedy seadragons, and the larger and even more flamboyantly decorated leafy seadragons, are close relatives of the seahorses and pipefishes and also exhibit similar reproductive strategies.

You can read more about the Georgia Aquarium’s seadragon breeding program and see a seadragon video at:
http://www.georgiaaquarium.org/exploreTheAquarium/webcam-seadragon.aspx.

Please also take a look at my seahorse book if you have a chance (see above) – I would greatly appreciate your feedback.

I’ll write more about keeping seahorses and their relatives in aquariums in the future. Until then, please forward your comments and questions.

Thanks, Frank.