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
- 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
Amphipod H
- 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
Atlantic mud crab O
Panopeus herbstii
- 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
Squareback marsh crab D
Armases cinereum
- 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
Mud fiddler crab D
Uca pugnax
- 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
Sand fiddler crab D
Uca pugilator
- 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
Red-jointed fiddler crab D
Uca minax
- 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
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
- 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
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
- 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
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
- 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
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
- 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
White shrimp O
Penaeus setiferus
- 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
Brown shrimp O
Penaeus aztecus
- 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
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)
- 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
Grass shrimp O
Palaemonetes vulgaris
- 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
Horseshoe crab C
Limulus polyphemus
- 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
Salt marsh grasshopper D
Orchelimum fidicinium
- 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
