Arthropods

Phylum Arthropoda

The phylum Arthropoda (arthro = “joint”; poda = “foot”) includes insects, chelicerates, and crustaceans.  Arthropods characteristically have jointed appendages and an exoskeleton, or external skeleton.  The body of an arthropod is separated into three regions:  head, thorax, and abdomen.  These regions are not always distinct, particularly in decapods.  Finally, while many insects pass through the marsh, we chose to focus solely on the grasshopper, which directly interacts with Spartina alterniflora.

Chelicerata – Horseshoe crabs are divided into three regions:  the prosoma (front), the opisthosoma (rear), and telson (tail).  Located under the prosoma are 14 appendages; one pair are small pinchers (“chelicerae”), others are walking and pushing legs.  Horseshoe crabs must shed their exoskeleton to grow, in a process called molting, and will crawl out the front of their split exoskeleton.

Crustacea – Crustacea is a sub-phylum of Arthropoda which includes a wide ranging group of organisms including decapods.  Many animals in the order Decapoda (“ten feet”) are found in the salt marsh-tidal creek ecosystem, primarily crabs, shrimp, and hermit crabs.  Decapods have five pairs of legs on the thorax; in “true” crabs, the first pair are modified into claws used for feeding and protection.  While shrimp and hermit crabs have very distinct regions, “true” crabs have a fused head and thorax region called the cephalothorax.

Insecta – Insects are divided into three regions:  the head, with a pair of antennae, the thorax with three pairs of legs and usually wings, and the segmented abdomen.  Insects in the salt marsh-tidal creek ecosystem aid in decomposition of organic matter and the recycling of nutrients.

Zooplankton H

Characteristics:
Tiny animals in water column with limited mobility, forms link between phytoplankton and larger organisms

Characteristics:
Tiny animals in water column with limited mobility, forms link between phytoplankton and larger organisms
Range:
Worldwide
Size:
Microscopic
Habitat:
Fresh and salt water
Fun Fact:
Holoplankton continue as plankton their entire life; meroplankton start as zooplankton and grow into a larger animal
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Amphipod H

Characteristics:
Laterally compressed body; species vary greatly in size, shape, and color

Characteristics:
Laterally compressed body; species vary greatly in size, shape, and color
Range:
Worldwide
Size:
Less than 0.5in (1cm) in length
Habitat:
Tidal creek intertidal areas in a variety of sediment types
Fun Fact:
Amphipods serve as a critical food resource for many birds and small fish
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Atlantic mud crab O

Panopeus herbstii

Characteristics:

Trapezoidal carapace, brown to gray; five teeth behind eye sockets; claw tips black or brown

Characteristics:

Trapezoidal carapace, brown to gray; five teeth behind eye sockets; claw tips black or brown

Range:

Atlantic coast of the U.S.

Size:

Carapace width up to 2.5in (6cm)

Habitat:

Estuaries up to 70ft (21m) deep, tidal creeks, low marsh

Fun Fact:

Dominant mud crab in salt marshes; capable of crushing small juvenile oysters

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Squareback marsh crab D

Armases cinereum

Characteristics:
Square carapace brown to olive; last segment of the fourth walking leg has black spines

Characteristics:
Square carapace brown to olive; last segment of the fourth walking leg has black spines
Range:
MD to FL and the Gulf of Mexico
Size:
Carapace width up to 1in (3cm)
Habitat:
High marsh, vegetated upland border
Fun Fact:
Often feeds on insects that consume marsh elder leaves, thus reducing herbivory on the plant
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Mud fiddler crab D

Uca pugnax

Characteristics:

“H” depression in middle of the carapace; eyestalks long

Characteristics:

“H” depression in middle of the carapace; eyestalks long

Range:

Atlantic coast of U.S.

Size:

Carapace width up to 1.5in (4cm)

Habitat:

Muddy substrate

Fun Fact:

Males wave large claw to attract females

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Sand fiddler crab D

Uca pugilator

Characteristics:

Pink-purple body, purple dot in center

Characteristics:

Pink-purple body, purple dot in center

Range:

Atlantic coast of U.S. and Gulf of Mexico

Size:

Carapace width up to 1.5in (4cm)

Habitat:

Sandy intertidal

Fun Fact:

Bristles on claws remove food bits from sand

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Red-jointed fiddler crab D

Uca minax

Characteristics:

Larger than other Uca, red joints on male’s large claw

Characteristics:

Larger than other Uca, red joints on male’s large claw

Range:

Atlantic coast of U.S., Gulf of Mexico

Size:

Carapace width up to 1.5in (4cm)

Habitat:

Low salinity to freshwater

Fun Fact:

Withstands anoxia

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Blue crab C

Callinectes sapidus

Characteristics:

Last pair of legs paddle-like for swimming; edge of shell with 9 teeth on each side; four teeth between the eyes

Characteristics:

Last pair of legs paddle-like for swimming; edge of shell with 9 teeth on each side; four teeth between the eyes

Range:

Atlantic coast of the U.S. and the Gulf of Mexico

Size:

Carapace width up to 9in (23cm)

Habitat:

Nearly every type of estuarine and near shore habitat

Fun Fact:

Some harvest regulations differ by state, but all harvested females with eggs must be released

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Lesser blue crab C

Callinectes similis

Characteristics:

Similar to C. sapidus, but six teeth between eyes (innermost two can be very small); claws tinted with fuchsia

Characteristics:

Similar to C. sapidus, but six teeth between eyes (innermost two can be very small); claws tinted with fuchsia

Range:

DE to FL and the Gulf of Mexico

Size:

Carapace width up to 5in (13cm)

Habitat:

Sand and mud in lower estuaries and tidal creeks with moderate to high salinity

Fun Fact:

Often compete for resources with C. sapidus

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Florida stone crab C

Menippe mercenaria

Characteristics:
Carapace brown to red with light spots; toothed claws often unequal in size, tips black; legs with red bands

Characteristics:
Carapace brown to red with light spots; toothed claws often unequal in size, tips black; legs with red bands
Range:
NC to FL and the Gulf of Mexico
Size:
Carapace width up to 6in (15cm)
Habitat:
Tidal creeks, oyster reefs, sand and mud
Fun Fact:
Claws crush prey, such as oysters; harvest rules vary across states regarding claw harvesting
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Thinstripe hermit crab C

Clibanarius vittatus

Characteristics:
Two claws and eight legs, last two designed to cling to an empty shell; brown legs with thin, white stripes

Characteristics:
Two claws and eight legs, last two designed to cling to an empty shell; brown legs with thin, white stripes
Range:
VA to FL and the Gulf of Mexico
Size:
Hard part of carapace up to 1.25in (3cm) long
Habitat:
Mud or sand beaches and tidal creek; up to 72ft in depth
Fun Fact:
Hermit crabs retract deep into the shell; as they grow, hermit crabs will select and move into larger shells
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White shrimp O

Penaeus setiferus

Characteristics:
Antennae 2.5–3 times body length; body white with black speckles; eyes kidney shaped

Characteristics:
Antennae 2.5–3 times body length; body white with black speckles; eyes kidney shaped
Range:
Atlantic coast of the U.S., the Gulf of Mexico
Size:
Up to 4in (10cm) long in tidal creeks, 4-8in (10-20cm) long in open water
Habitat:
Transient, estuaries, tidal creeks
Fun Fact:
More active during the day than brown shrimp
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Brown shrimp O

Penaeus aztecus

Characteristics:
Conspicuous ridges that extend the length of the head; brown-green body; eyes kidney shaped

Characteristics:
Conspicuous ridges that extend the length of the head; brown-green body; eyes kidney shaped
Range:
Atlantic coast of the U.S. and the Gulf of Mexico
Size:
Up to 4in (10cm) long in tidal creeks, 4-8in (10-20cm) long in open water
Habitat:
Transient; estuaries, tidal creeks, primarily mud bottom
Fun Fact:
Usually burrow in response to lower temperatures
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Big-clawed snapping shrimp C

Alpheus heterochaelis

Characteristics:
One large chela (claw), with dark translucent green body and a small rostrum (shark projection off the head)

Characteristics:
One large chela (claw), with dark translucent green body and a small rostrum (shark projection off the head)
Range:
From NC to FL
Size:
Up to 2.5in (6cm)
Habitat:
Tidal creeks, common around oyster beds
Fun Fact:
The large claw can snap and create a loud popping sound that can stun or kill prey
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Grass shrimp O

Palaemonetes vulgaris

Characteristics:
Clear shrimp with long rostrum bearing sharp teeth and round eyes at the end of conspicuous stalks

Characteristics:
Clear shrimp with long rostrum bearing sharp teeth and round eyes at the end of conspicuous stalks
Range:
Atlantic coast of the U.S. and the Gulf of Mexico
Size:
Up to 2in (5cm) in length
Habitat:
Shallow estuaries, abundant in tidal creeks
Fun Fact:
Tolerates changing conditions; can be found in waters with salinities ranging from 2 to 36 ppt
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Horseshoe crab C

Limulus polyphemus

Characteristics:

Brown carapace; two compound eyes and set of simple eyes on the prosoma; three distinct body regions

Characteristics:

Brown carapace; two compound eyes and set of simple eyes on the prosoma; three distinct body regions

Range:

Atlantic coast of the U.S. and the Gulf of Mexico

Size:

Females 18-19in (46cm) head to tail; males 14-15in (36cm)

Habitat:

Beaches, tidal creeks, estuaries

Fun Fact:

Horseshoe crabs lack antennae, jaws, and have seven pairs of legs, making them related to spiders and scorpions

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Salt marsh grasshopper D

Orchelimum fidicinium

Characteristics:

Similar to common garden grasshopper; green with two long antennae; camouflages very well with Spartina

Characteristics:

Similar to common garden grasshopper; green with two long antennae; camouflages very well with Spartina

Range:

Atlantic coast of the U.S.

Size:

Averages 1in (3cm) in length

Habitat:

Among vegetation on marsh platform to upland border

Fun Fact:

Tends to feed on different areas of Spartina blades to avoid competition with the periwinkle snail

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