Pictorial Key to Decapod Zoeae of the Mid-Atlantic Coast

Bill Johnson, Goucher College, Towson, MD

CONTENTS (Use hyperlink or Go To PP slide numbers in red )

• Scope and Caveats 2• Approach used for Identifications and Guide to Navigation 3• Additional Resources 4• Basic Anatomy of decapod zoeae 5

– Telsons 6• Begin Identifications HERE 7

Please send comments, corrections to bjohnson090@gmail.com. Better photos appreciated

Coverage and Caveats

• This guide is based on extensive samples collected off of Assateague Island, VA in June of 2006, 2008, and 2009. It only contains the more abundant decapod zoeae present at that time. You may encounter species not covered here. If you do not find your specimen, try sources listed in Additional Resources 4

• Decapod zoeae change with each molt. If your specimen differs from those shown here you may have a different stage from those shown- or a different species.

Approach used for Identifications and Guide to Navigation

• This is an ‘artificial” key based on the characters that are usually most visible, not those used in formal classification.

• To go to the next step in identification• In Slideshow View in PowerPoint- Click on the BLUE hyperlink• In Normal View- go to the slide number specified in the preview pane to the left. If your

choices lead you astray, use the slide numbers to back up.

• There are many PURPLE hyperlinks to specific pages in http://www.zpkonline.com where you will find additional illustrations, ID tips and information associated with species that you have identified.

– When you are done, just go back to PowerPoint. Hint use the alt-tab (Microsoft) or command-tab (mac) keyboard shortcuts.

Additional Resources1. Johnson WS, Allen DM. 2012. Zooplankton of the Atlantic and Gulf Coasts: a guide to their

identification and ecology, Second Edition. Johns Hopkins University Press, Baltimore, MD, 453 pages.

– Covers many additional species, often just the first zoeal stage– Line drawings illustrate many identification features and distinguish between similar species.– Contains extensive information on the biology of decapod larvae in general and that of individual species. – Gives references to research articles and original descriptions. – It is the only published guide to decapod shrimp larvae of this region. – Provides tips on collecting, observing, and preserving zooplankton.

2. Bullard SG. 2003. Larvae of anomuran and brachyuran crabs of North Carolina. Crustaceana Monographs 1:1-142.

– Pictures all zoeal stages AND the megalopae. – Some more northern species present on the mid-Atlantic may be absent.

Basic Anatomy. The head and thorax are enclosed (sometimes loosely) in a carapace followed by the abdomen that terminates in a telson. Telsons are important in identification. See More telsons

Abdomen (3)

Carapace (1)

shrimplike Not shrimplike- crab larvae

Rostrum (2): an anterior projection from the carapace

Telson (4)

Dorsal spine (5)on carapace

Lateral spine (6)on carapace

1

15

4

3

1

2

56

1

2

3

1

2

4

3

1

21

4

1

6

5

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TelsonsTelsons are often diagnostic. They differ between the shrimp-like decapod zoeae and the crabs.

Shrimplike zoeae telsons GO TO 7Crab Zoeae telsons GO TO 16

Simple early zoeae telson (1) without a tail fan

Later zoeae telson with a tail fan- a central telson (1) flanked laterally by two pair of uropods (2)

THIS IS A MYSID (“opossum shrimp”) distinguished from decapod larvae by the bubble-like statocyst (3) at the base of the uropods. Mysids are not decapods but GO TO

Abdomen (4)

Telson (1)

1

1

4

1

4

12

12

3

With large “reversed” claws (1). Mantis shrimps (stomatopods)

Lacking large “reversed” claws

Mantis shrimp

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Stomatopods are not decapods, but are included here because they are frequently caught in plankton collections.

Several families of mantis shrimps have an earlier larval stage, the “antizoeae” that lacks claws.

Body plan not shrimplike

Abdomen (arrows) much narrower than thorax (or carapace) GO TO 16

Body plan more or less shrimplike

Abdomen (arrows) and thorax of roughly similar width. 9

Shrimp or not

B. Shrimplike: Dorsal spine on abdomen- BELOW

A. Large dorsal abdominal spine (1)-median spine on telson

B. Small spine on abdomen (may be hard to see.)- no median spine on telson

median spine on telson(all stages)

A. Shrimplike: NO Dorsal spine on abdomen GO TO 10

Ghost shrimpBiffarius biformis

1Seven-spine bay shrimpCrangon septemspinosa

Telson- late zoeaTelson- early zoea

Shrimplike: NO Dorsal spine on abdomen

A. With large abdominal swimming appendages (1): Peneid and sergestid shrimpsBELOW

B. Abdomen (b) lacking large abdominal swimming appendages GO TO 11

B. 4 long legs lacking clawsAcetes americanusNot shown-Need photo

C. Claws on first 3 legsPostlarvae of commercial shrimps (brown, pink and white. not shown. Need photo

“Head” (carapace) extremely long, thin. (2)Lucifer faxoni

a b

b

b

2

1

Hermit crabs: Many species of adult hermit crabs are in the area, but the `was by far the most common hermit crab larva in our collections.

B. Rostrum small or moderateGO TO 12

A. Long rostrum

Shrimplike, no dorsal spine or swimming legs on abdomen

Naushon mud shrimp (Naushonia crangonoides)

A. Abdomen with ventral paired, fleshy “hooks” on each segment.

Note the next several shrimplike zoeae are similar and may require some

manipulation to see critical characters. Using a combination of features is

more reliable than using one alone.

Shrimplike, no dorsal spine or swimming legs on abdomen. Rostrum small or moderate

B. Abdomen without ventral paired, fleshy “hooks” on each segment. GO TO 13

A. Without a hump (note: grass shrimps, may have a bend) GO TO 14B. Always with decided bend or “hump” in the abdomen (2) Broken-back shrimp BELOW.

Broken-back shrimp (Hippolyte pleuracanthus)Later stages have small claws (1)Distinctive eyes (3) anda telson where the spines (4) are of markedly unequal lengths

4

3

1

Shrimplike, no dorsal spine or swimming legs on abdomen. Rostrum small or moderate (continued)

A. Rostrum flattened at the base (arrow).You may have to roll the specimen to see this. No spines on rostrum.

B. Rostrum not flattened at the baseGO TO 15

Coastal mud shrimp (Upogebia affinis)

Early telson Late telson

Shrimplike, no dorsal spine or swimming legs on abdomen. Rostrum small or moderate (continued)

Rostrum slender, pointed slightly upward. Grass shrimps Palaemonetes spp.

Rostrum lacks teeth

Later zoeae have 1 or 2 teeth (arrow) at the base of the rostrum.

Later zoeae have a tail fan. Only the telson is shown here (Uropods not shown.)The telson is slender and narrows toward the tip.

No tail fan. Telson broad, straight across.Spines continue around the “corner” (arrow). No uropods. (compare with Coastal Mud Shrimp)

Early zoea Late zoea

Shrimplike, no dorsal spine or swimming legs on abdomen. Rostrum small or moderate (continued).

Last shrimp-like slide

Not shrimplike> no dorsal spine. BELOW

A. Rostrum long

Rostrum extremely long and delicate.Delicate spines on the posterior of the carapace. Porcelain Crabs.

B. Rostrum small or moderate

Rostrum robustLong lateral spines on the carapace.Sand Crabs (Emerita talpoida- later zoeae)Rostrum robust.Long spines on the posterior of the carapace directed outwards. Mole Crabs (Lepidopa websteri)

Rostrum tiny or lacking.Oyster Pea CrabZaops ostreum

Not shrimplike> With a dorsal spine on the carapace. GO TO 17

telson

Crablike 1

Rostrum small.Sand Crab (Emerita talpoida) first zoeaBAD LinK

Crablike, dorsal spines present on carapace but no lateral spines BELOW

B. Dorsal spine and rostrum shorter than carapaceA. Dorsal spine (1) and

rostrum (2) longer than carapace

Crablike, dorsal spines AND lateral spines present on carapace. GO TO 18

Green Shore Crab (Carcinus maenas)

2. Rostrum and dorsal about equal in lengthFiddler crabs (Uca spp),

ANDMarsh crabs Armases/Sesarma-

1. Rostrum much shorter than dorsal spine. Spider crabs (Libinia spp.)

telson

Crablike 2

2

1

A. Rostrum (1) long, directed ventrally, flanked by a pair of equally long antennules (2).

B. Rostrum medium to shortNo long antennulesGO TO 19

1. Rostrum (1) curved upward. Say’s mud crab (Dyspanopeus sayi)

2. Rostrum straight, distinctive bump (3) on “forehead”.. Smooth mud crab (Hexapanopeus angustifrons)

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2

2

3

Not shrimplike> carapace with both dorsal and lateral spines

Mud (xanthid) Crabs. Many mud crabs occur in the region. These two mud crab larvae are common in the plankton

With dorsal spines. Lateral spines (1) short to moderate; no long antennulesA. Lacking a small spine on the telson margin. GO TO 20

1. very small larvaeBlue crabs (Callinectes sapidus) and close relatives (other Callinectes species and Portunus.)

2. Larvae not small.Distinctive spine (3)on last abdominal segment. Lady crab (Ovalipes ocellatus)

0.5 mm

2

1

13

3

2

B. Small spine on outer margins of telson (2); Swimming Crabs) BELOW

Crablike- short lat spines

A. Lateral spines (1) short to moderate B. Lateral spines long

1. Rostrum (2) directed forwardFleshy lateral projections (3) at telsonPea crabs Pinnixa spp.

2. Rostrum (1) directed ventrally. Mussel pea crab. (Tumidotheres maculatus)

Note: The Ghost Crab (Ocypode quadrata) is common, but its rather similar larvae were not collected in June. They may be present later, but are not shown here.

Asian Shore Crab (Hemigrapsus sanguineus)

telson

telson2

2

3

1 1

This is the last crab page.

No spine on outer margin of the telson; Lateral spines on carapace directed down. BELOW

Common Mysid “shrimps” with statocysts (1) on uropodsTelsons are diagnostic

Note: These are shrimplike but NOT decapods

Neomysis americana

Americamysis bigelowi

Metamysidopsis swifti

Neomysis telson-

Americamysis Telson (2)

Metamysidopsistelson

Note “claw”- absent on other local mysids

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