Aquatic Macroinvertebrates Brazoria NWR (Big Slough and Crosstrails Pond) Nov. 2015 - Nov. 2016 Photos by Pete and Peggy Romfh
SCUD (SIDE-SWIMMERS) Arthropoda, Sub-Phylum Crustacea, Class Malacostraca, Order Amphipoda Size 3-10 mm Sowbugs have bodies that are flattened from side to side, giving them the name side-swimmers. They have two pairs of antennae and lack a carapace. Their compound eyes are not on stalks. They have 7 pairs of walking legs, one on each segment of the thorax, and short appendages on the abdominal segments. Their gills are located on the thorax.
CRAWFISH Arthropoda, Sub-Phylum Crustacea, Class Malacostraca, Order Decapoda Pygmy Crawfish - Cambarellus spp. Size 18-25 mm One morph (pattern) shows dark blotches from back of carapace to to tail fin. Second morph shows two dark, parallel stripes from behind the eyes to the pre-fan segment. Both show a slightly bowed, dark stripe that spans the tail from side to side.
AQUATIC SOWBUGS (ISOPODS) Arthropoda, Sub-Phylum Crustacea, Class Malacostraca, Order Isopoda Bottom Right: ventral view of sowbug (note that sowbug is missing parts of appendages) Size <15 mm Sowbugs have 7 pairs of long walking legs, one on each segment of the thorax. They have two pairs of antennae with one set much longer than the other. At the end of the abdomen, there are two forked, tail-like appendages. Sowbugs absorb oxygen using gills located on the underside of the abdomen.
OSTRACODS (SEED SHRIMP) Arthropoda, Sub-Phylum Crustacea, Class Ostracoda Top image photographed from projection microscope video view. Size <2 mm; bi-valve crustaceans found in fresh water. Ostracods have five pairs of appendages (including antennae) on their heads but only 1-3 pairs of appendages on the rest of the body. They have a bivalve-like carapace that is shed with each molt, so there are no growth rings as in mollusks. They have no gills and take in oxygen through plates on the body surface.
COPEPODS Arthropoda, Sub-Phylum Crustacea, Class Maxillopoda - Copepoda Top Copepods: photographed from projection microscope video view Top Left: Cyclops copepods with egg sacs Bottom Left: Cyclops copepod with egg sacs; with 2 water fleas Bottom Right: Calenoid Copepod Size 1 mm Most copepods absorb oxygen directly into their bodies. They have a thin exoskeleton and two pairs of antennae.
WATER FLEAS Arthropoda, Sub-Phylum Crustacea, Class Branchipoda, Sub-Order Cladocera Water Fleas (Daphnia spp.); size 1-2 mm Top Row right: photographed on paper towel Cladocera have a head that is angled downward, a single black compound eye, and two pairs of antennae. The second antennae are used for swimming in most species. The body has a folded carapace which covers the thorax and abdomen. Oxygen is taken up through the body surface.
SPIDERS Arthropoda, Sub-Phylum Chelicerata, Class Arachnida Size: <25 mm Six-spotted Fishing Spider (Dolomedes triton); AKA Yellow Fishing Spider These spiders may be seen scampering across the surface of the water.
WATER MITES Arthropoda, Sub-Phylum Chelicerata, Class Arachnida, Sub-Class Acari - Mites and Ticks Hydrachnidia - Water Mites Water Mites species may be several different colors. Size 2 mm Top: Red water mite. The larva of this species is a parasite on the water boatman. The mite looks like a fat spider with a bright red, round body. It has 8 small legs attached near the front end of its body. The two pairs of eyes are set far apart. Bottom: Blue water mite
PREDACEOUS DIVING BEETLES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Coleoptera Family Dytiscidae Predaceous Diving Beetles (Laccophilus spp.) Size 5 mm Adults have filiform antennae. Their hind legs are modified for swimming and they move their hind legs together like oars. Adult predaceous diving beetles breathe air from an air bubble carried under their front wings. Note - underside is oval (convex).
PREDACEOUS DIVING BEETLES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Coleoptera Family Dytiscidae Left: Predaceous Diving Beetles (Liodessus spp.); size 3 mm Right: Dingy Diver (Laccophilus maculosus)
WATER SCAVENGER BEETLES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Coleoptera Family Hydrophilidae Left: Water Scavenger Beetles (Tropisternus spp.); size 10 mm Right: Water Scavenger Beetles Water scavenger beetles swim by moving their legs alternately. Antennae are club-shaped. Note - underside is concave. They store air as a bubble under the wings and as a thin layer held in non-wettable hairs on the bottom of the body.
BURROWING WATER BEETLES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Coleoptera Family Noteridae Burrowing Water Beetle (Hydrocanthus atripennis); size 4-5 mm Burrowing water beetles have a distinctive platform underneath in the form of a plate between the second and third pair of legs. Their legs are short and stout and are adapted for burrowing. They tend to be relatively convex dorsally and ventrally flattened.
FLIES and MOSQUITOES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Diptera Left: Midge Pupa (Chironomid); size 12-14 mm Bottom left: Midge pupa being ingested by water beetle. Right: Crane Fly Larva (Family Tipulidae); size 10 mm The skin of crane fly larvae often has fleshy lumps. The end of the abdomen is surrounded by several pairs of short, fleshy lobes.
FLIES and MOSQUITOES Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Diptera Left: Mosquito larva (Family Culicidae). Size 4-18 mm. The larvae breathe air from just below the water surface via a short breathing tube on the rear of the abdomen. They use brushes found on the front of the head to set up currents to direct algae, bacteria, detritus, etc. into their mouth. Right: Soldier fly larva (Family Stratiomyridae). Size 5-35 mm. The larvae breathe by means of 2 spiracles at the end of their abdomen. The spiracle chamber is often surrounded by non-wettable hairs.
MAYFLY NYMPHS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Ephemeroptera Size 10-25 mm Mayfly nymphs have gills that attach to the sides of the abdomen. The gills are either flat plates or filaments. There are usually 3 long, thin tails (sometimes two) on the end of the abdomen. Mayflies are indicator species for a clean, unpolluted water environment.
GIANT WATER BUGS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Belostomatidae Top Left: Giant Water Bug Adult; size 15-25 mm Top Right: Giant Water Bug Nymph Giant water bugs often hang approximately vertically in the water, head down, with two short breathing 'straps' at the end of the abdomen reaching out to obtain air. Air is also stored under the wings for prolonged dives. They deliver a painful bite if mishandled. They are climbers and swimmers.
WATER BOATMEN Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Corixidae Left: Water Boatman Adult; size 5 mm Right: Water Boatman Nymph; size 2 mm Water boatmen swim head down along the bottom. They swim in a quick, darting manner with oar-like movements of their hind legs. Water boatmen breathe from an air bubble trapped under the wings and around the abdomen.
VELVET WATER BUGS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Hebridae Left: Velvet Water Bug (Merragata hebroides), Size 1.5 mm. Right: Velvet Water Bug (Merragata spp.), small-winged form Velvet water bugs are semiaquatic insects that live on floating vegetation in ponds. They move across water surfaces at a walk or run but do not skate. The wings lack distinct veins. They have a layer of short, dense hairs that covers their bodies except for the abdomen and legs giving them a velvety appearance.
WATER TREADERS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Mesoveliidae Water Treader (Mesovelia spp.); size 4 mm; green; wingless Water treader antennae are longer than their heads. They have long slender legs. They are found on the surface of still bodies of water and crawl on mats of algae or floating vegetation.
CREEPING WATER BUGS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Naucoridae Creeping Water Bugs (Pelocoris femoratus); size 10 mm. Note color difference in creeping water bug on left vs. right. Creeping water bugs are crawlers, climbers, and swimmers. Creeping water bugs obtain air from an air bubble held under the wings. Some air is also held in short, fine hairs on their underside. They can inflict a painful bite with their beak if mishandled.
WATER SCORPIONS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Nepidae Water Scorpion (Ranatra spp.) Size 35 mm head to abdomen; 60 mm head to tip of 'tail' process Water scorpions are climbers. They are poor swimmers. Water scorpions breathe atmospheric air via a pair of long tubes on the end of their abdomen. They usually hang head down with the tubes at the surface of the water film. They capture prey by seizing it with their front legs.
BACKSWIMMERS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Notonectidae Top Row: Backswimmer (Buenoa spp.) dorsal and ventral views; size 6 mm Center Row: Backswimmer Nymph (Notonecta spp.) dorsal and ventral views; size 6 mm Bottom Row: Backswimmer Nymph (Notonecta spp.) dorsal view; size 2-3 mm All backswimmers swim with powerful oar-like movements of the hind legs. They remain upside down when swimming. Their air store is held in two troughs with fringes of hair on the bottom side of the abdomen. Additional air is carried under the wings.
PYGMY BACKSWIMMERS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Pleidaee Left: Pygmy Backswimmer (Neoplea striola) dorsal and ventral views; size 2 mm Right: Pygmy Backswimmer (Paraplea spp.) dorsal and ventral views; size 2 mm
SMALLER WATER STRIDERS Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Hemiptera Family Veliidae Smaller Water Strider (Microvelia spp.) Size 1.5 mm Wingless Microvelia spp. Veliidae are also known as broad-shouldered water striders. They skate on the surface of the water. They breathe from the air by means of spiracles. They also breathe underwater from a thin layer of air trapped in velvety hairs over their body. These water striders take on a silvery appearance under water because of the trapped air.
DAMSELFLIES (NYMPHS) Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Odonata Sub-order Zygoptera Damselfly Nymphs; size 12-18 mm Damselfly nymphs (naiads) have three, flat, long gills on the end of the abdomen. Their bodies are long and thin; their heads are wider than the thorax and abdomen.
DRAGONFLIES (NYMPHS) Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Odonata Sub-order Anisoptera Left: Dragonfly Nymph 1, dorsal and ventral views Right: Dragonfly Nymph 2, dorsal and ventral views; size 35 mm Their bodies are either long and stout or oval and somewhat flattened. Dragonfly nymphs (naiads) have gills inside the rear of their abdomens. They pump water in and out of the gill chamber to obtain oxygen. They capture prey with a unique lower lip.
DRAGONFLIES (NYMPHS) Arthropoda, Sub-Phylum Hexapoda, Class Insecta, Order Odonata Sub-order Anisoptera Left: Dragonfly Nymph 3, dorsal and ventral views Right: Dragonfly Nymph 4, dorsal and ventral views
BLADDER SNAILS Phylum Mollusca, Class Gastropoda Family Physidae Left: Physid Snail 1 Right: Physid Snail 2; size 8 mm Sinistral (left-handed) opening; large aperture; no operculum. Also known as pulmonate snails, they breathe air at the water surface. The snails have a cavity in their bodies which they can fill with air.
BLADDER SNAILS Phylum Mollusca, Class Gastropoda Family Physidae Left: Physid Snail 3; size 18 mm Top Right: Physid Snail 4; size 6-8 mm Bottom Right: Pond Snail eggs in gelatinous mass laid on submerged plants
This book was created for educational purposes in support of the volunteers at the Discovery Center, Brazoria NWR. These photos represent only some of the aquatic invertebrate species that may be seen at Brazoria NWR. As we accumulate additional species photos, this volume will be expanded. Photos and book compilation were done by Pete and Peggy Romfh. All photos were taken using standard macrophotography techniques except those noted that were taken from video projection images. Thanks to Mary Hoffman and Kelly Koch for support with specimen collection, Dave Brandes and Ed Barrios for technical support, and Tom Schneider for project support. If you identify any errors in this book, please let us know at peggy.romfh@comcast.net or pete.romfh@comcast.net. Ed 1. Jan. 2016; Ed. 2 Nov. 2016