Animals Introduction Page - Keys to the Aquatic Biota of the Hawaiian Islands

	CPIE Project		Page A1

	Key to Aquatic Animals

10a (1) Organism is a VERTEBRATE: fish, frog, turtle, or bird. { Paired, typical vertebrate eyes present on head. Free-swimming in or on water or on shore, or wading, or flying [25]

10b Organism is not a fish, frog, turtle, or bird. { Free-swimming, crawling, burrowing, flying, or attached. Eyes generally very simple (for example, pigment spots), with or without a lens and lacking an iris (no variable pupil size), OR eyes multi-faceted, OR eyes absent altogether [11]

INVERTEBRATES The term "invertebrates" is simply a general reference to animals which are not vertebrates. Certainly in terms of number of species, the vast majority of invertebrates in fresh or brackish water are microscopic in size (under 5 mm or 3/16 inch). These organisms might be seen with a magnifying lens or under a dissecting microscope, but many more can be examined in detail only by mounting a sample of water or submerged vegetation on a glass slide (wet mount) and viewing with a compound microscope at 100X power or greater. The identification key provided here, while in places requiring specimen magnification to determine certain organism characteristics, does not cover these "microscopic" invertebrates. A listing of Hawaiian aquatic invertebrates, including references to useful identification materials, is provided elsewhere in CPIE.


11a	(10)	Organism sessile: {attached or fixed to substratum such as a rock or plant. Animal may be a colony of individuals (called zooids) connected within a common covering (a matrix or cuticle); OR an aggregation (close together or even attached, but individuals not physiologically connected); OR an isolated individual	[12]
11b		Organism not sessile and not colonial; { may be free swimming, floating, walking, or flying; OR may be buried in soft substrata such as mud or sand, but not so attached that it cannot be removed without damage	[15]
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12a	(11)	Animal colonial or not, but without a skeleton (soft bodied) OR skeleton consisting of either a thin cuticle, internal fibers, or internal spicules (needle-like structures)	[13]
12b		Animal not colonial (although individuals may be aggregated). Having an external skeleton of some kind: jointed plates or a one or two-piece shell (valve)	[14]
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13a	(12)	Animal is a colony of individuals (zooids) connected by stolons or encased in a mass with a common covering (a matrix or cuticle) which may be hard or soft. Zooids with tentacles. Moss animals (BRYOZOA)	[45]
13b		Animal not colonial (although reproduction by budding may produce attached juveniles). Without a skeleton; soft bodied, tubular, and with tentacles. Hydras ~ Phylum CNIDARIA ~ Class HYDROZOA	[55]
13c		Animal is a mass with "individuals" not evident, more or less encrusting, with numerous voids (sponge-like). Structural skeleton consisting of either stiff internal fibers or spicules or both. Sponges ~ Phylum PORIFERA	[12]
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14a	(12)	Cone-shaped and comprised of interlocking plates surrounding an opening with two, bipartite, plated valves. Marine and estuarine, never fresh water. Barnacles ~ Phylum ARTHROPODA ~ Class CRUSTACEA, CIRRIPEDIA	[33]
14b		Cap-shaped and closely adherent but not cemented down; OR bivalved (shell having two more or less equal parts) and cemented down by one valve, or attached by a byssus (strong threads) ~ Phylum MOLLUSCA	[33]
14c		Worm-shaped: shell a white (calcareous) tube attached to hard substrata in brackish water or near the sea ~ Phylum ANNELIDA ~ Class POLYCHAETA	[see]
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15a	(11)	Animal has an external skeleton: either jointed plates which cover all of the body and limbs, or just certain parts (for example, the head); OR skeleton is a shell which is cap-like or coiled (like a snail) or hinged (like a clam)	[16]
15b		Animal soft-bodied, without an external hard covering; although internal structural supports may be present	[17]
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16a	(15)	Animal has a jointed exoskeleton; { most or all parts of body sclerotized (encased in a stiff material called chitin) which is extensively jointed for flexibility; OR at a minumum the body appears soft but the head is sclerotized ~ Phylum ARTHROPODA	[25]
16b		Essentially soft-bodied individual housed in an external shell which may be coiled, cap-like, or bipartite (two parts) ~ Phylum MOLLUSCA	[33]
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17a	(15)	Animal worm-like (vermiform) or grub-like; body segmented or annulated (constricted in rings at regular intervals; may require magnification)	[21]
17b		Animal either not worm-like, or if worm-like, then lacking multiple constrictions or repetitive external structures down the length of the body that indicate segmentation	[18]
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18a	(17) & (20)	Animal worm-like with a sucker (attachment disc) at each end. Body faintly annulated. Leeches ~ Class HIRUDINAE	[see]
18b		Animal more or less worm-like, but with no or only one attachment disc. (NOTE: in many leeches the front attachment disk is small and difficult to see without magnification)	[19]
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19a	(18)	Animal hair-like, extremely thin, several centimeters long. Diameter the same throughout, except at ends. When alive, moving by slowly writhing and coiling. Freshwater ponds and streams. Horsehair worm ~ Phylum NEMATOMORPHA
19b		Small (1 to 30 mm), distinctly flattened worm with one or more pairs of eyespots on the upper (dorsal) surface near a bluntly rounded front end	[22]
19c		Tubular and with tentacles; lacking eyespots. Usually attaching to vegetation by a basal disc. Hydra ~ Phylum CNIDARIA ~ Class HYDROZOA	[55]


© 2001 AECOS, Inc. [FILE: keys_animals.html]		Invertebrates
INSTRUCTIONS INDEX REFERENCES	10

	10a	(1)	Organism is a VERTEBRATE: fish, frog, turtle, or bird. { Paired, typical vertebrate eyes present on head. Free-swimming in or on water or on shore, or wading, or flying	[25]
	10b		Organism is not a fish, frog, turtle, or bird. { Free-swimming, crawling, burrowing, flying, or attached. Eyes generally very simple (for example, pigment spots), with or without a lens and lacking an iris (no variable pupil size), OR eyes multi-faceted, OR eyes absent altogether	[11]