|Levels of identification and other taxonomic notes
Great Lakes Coastal Monitoring Project
By Joseph Gathman, Valerie Brady, Michelle Dobrin, and Jan Ciborowski
(Last updated 10-20-2011)
The following are recommended levels of identification of taxa for the Great Lakes Coastal Monitoring Project. Identification tips are included, but are neither universal nor exhaustive. They are based on previous sampling experience. Use the keys and don’t go by what we say is common, etc.
Recommendations for all taxa are for mature, intact specimens. Very small/immature specimens frequently cannot be taken to genus, although family is almost always possible with effort unless specimen is too damaged. It is desirable to take the time to get a family ID, but genus IDs on small/immature specimens may not be worth the effort to find out if it is possible. Be willing to take some time to try because it often pays to climb the learning curve, but err on side of caution in what you enter in the database. And if a couplet calls for measurement, measure it with a scale ocular or ruler, or else forget it. Eyeballing is unreliable, especially when ratios are called for.
If you think you’ve found a taxon not listed in the taxa list of the data entry system, check to see if it is known by other names. Do this before requesting that it be added to the taxa list on the data entry site.
Here is a list of recommended ID guides:
Merritt, Cummins & Berg 2008 (for most insects)
Thorp & Covich 2010 (for molluscs, mites, crustaceans, leeches)
Peckarsky, Fraissinet, Penton & Conklin 1990 (for molluscs, mites, crustaceans, leeches, Lepidoptera)
Klemm 1985 (A Guide to the Freshwater Annelida of North America - a favourite for leeches)
Clarke 1981 (not a key, but has great descriptions, distributions and photos of molluscs)
Larson, Alarie & Roughly 2000 (Dytiscidae)
Wiggins 1996 and Ross 1944 (Trichoptera)
Needham, Westfall & May 2000 (Anisoptera)
Westfall & May 1996 (Zygoptera)
Pennak 2001 (non-insects)
Burch 1982 (snails; but see Peckarsky et al. and Clarke)
Mackie 2007 (Psidiidae (formerly Sphaeriidae)): http://www.collegeofidaho.edu/campus/community/museum/Tools/GLMackie/Sphaeriidae/SphaeriidaeIndex.htm
For insects, please count the life stages separately (except non-aquatic adults). You will be able to specify life stage when you enter the data
Non-aquatic adult insects (e.g. Diptera, Trichoptera adults) do not need to be identified and should only be noted in the comments section.
Recommended ID levels are as follow:
Collembola – leave at order (Collembola)
Ephemeroptera – Genus. Try to get to genus, but immature specimens may be difficult. Specimens without well-developed wing pads may be too immature for genus. It’s often pointless to bother trying genus with no abdominal gills. Caution: looking at Baetidae mouthparts is difficult if your optics are sub-par or your hands are shaky. Key Baetidae using Merritt and Cummins mayfly chapter key – other keys may use different naming systems. May need to remove head and/or pull off mouthparts and look at them separately. Caenidae and Baetidae are by far the most common families we’ve seen. Heptageniidae occur in riverine and wave-swept sites. Burrowing mayflies (mostly Ephemeridae: Hexagenia and some Ephemera) are typically in deeper, soft-bottomed sites.
Odonata – Genus. Specimens without well-developed wing pads may be too immature for genus, but give them a try before giving up.
Anisoptera – Genus whenever possible, otherwise try to get to family for immature specimens. Some families (e.g., Libellulidae and Corduliidae) are difficult to tell apart, but use the keys in Merritt et al. We will consider combining these two families if everyone is struggling. If you can’t tell them apart, call them Libellulidae/Corduliidae).
Zygoptera – Family is easy. Almost all are Coenagrionidae. You typically need well-developed gills or to look at the pre-mental setae (on the INSIDE of the mentum, so you pull it out and then look down on it from above). Other families are Lestidae (uncommon) and Calopterygidae (lotic critters).
Hemiptera – Genus for adults. Family for most larvae. Note that larvae/nymphs lack wings, but there are also wingless adults in the families Gerridae, Veliidae, Mesoveliidae, and possibly Hebridae. Larvae typically have reduced tarsal segment numbers (only 1 or 2 tarsal segments on each leg), though some genera can be figured out due to characteristic body shapes (e.g. Belastoma, Ranatra) or because there’s only one local genus within the family. Any bug that keys to Macroveliidae is probably a terrestrial, because this family supposedly only occurs in the West. Beware of bugs that key to Saldidae; they are difficult to catch and tend to be found in non-wetland habitats. So if something keys to Saldidae, double-check that you aren’t looking at a terrestrial bug.
Trichoptera – Genus. Even family can be difficult at times. Caution: Molannidae can look like Leptoceridae (Leptos have long (for a trichop) antennae); Dipseudopsidae looks like Polycentropodidae and somewhat like Psychomyiidae. Hydropsychidae and Glossosomatidae (and possibly some others) occur in our riverine and wave-swept sites. Limnephilidae and Phryganeidae have a prosternal horn and should occur in more lentic, protected areas. Most Phryganeidae are very large when mature. The Polycentropodid Cernotina has not been noted from the Great Lakes; these are most likely Polycentropus. Wiggins recommends that Ceratopsyche remain a subgenus of Hydropsyche; given the difficulty in separating the two, we will call them all Hydropsyche.
Coleoptera – Genus, with certain exceptions: 1. Curculionidae (weevils) only to family – there is no larva key and the adults seem to be quite difficult unless we get expert advice; 2. Chrysomelidae only to family – there is no larva key and adults are non-aquatic; 3. Dytiscidae and Hydrophilidae to genus if at all possible.
Diptera (other than Chiro.) – Genus for Nematocera and some Brachycera. Caution: some Ceratopogonidae require wet mounting and viewing under a compound microscope to see anal setae and head capsule collar region. We will combine the difficult to separate genera Bezzia & Palpomyia. Brachycera larvae should be keyed to family whenever possible, despite the effort required. In some cases it may not be possible, due to morphological diversity in this group. Genus is pretty easy in some families (e.g., Tabanidae), difficult in some others, and impossible (no key or limited key, e.g. Ephydridae) for yet others. Stratiomyidae: We will combine the difficult to separate genera Odontomyia & Hedriodiscus. Do not key Muscidae and Ephydridae past family. Use tissue clearing fluid to see cephalopharyngeal skeletal structure. Once a specimen’s family is determined, future specimens can usually be ID’d with less effort. Non-Brachycera pupae can be taken to family using M&C. All Diptera adults should be reported in the comments section and not entered as true data.
Diptera (Chironomidae): ID to tribe. Hopefully we can be reasonably accurate without slide-mounting the larvae.
Megaloptera, Plecoptera, Neuroptera, Lepidoptera – Genus. Megaloptera and maybe Neuroptera larvae are easily first confused for beetles, but once seen should not be mistaken again. Plecoptera nymphs can be confused for mayflies. All of these are uncommon. Neuroptera (spongilla flies) live in sponges and have long sucking mouthparts. Megaloptera: Sialidae are the smallest and most lentic members of this order. Other Megaloptera and all Plecoptera occur in riverine and wave-swept sites. However Corydalis can occur in deeper organic sediments.
Oligochaeta – Leave at this level. Convert all more specific identifications to “Oligochaeta”.
Acari – Leave at “Hydracarina”.
Hirudinea – Family or genus (where relatively easy (e.g. mature Glossiphoniidae)). Most specimens belong to the families Glossiphoniidae or Erpobdellidae. Eyes and gonopores can be obscured, making ID nearly impossible in some cases. Use clearing fluid to better see the eyes if necessary. Some Glossophoniidae can easily be taken to species (e.g., Helobdella stagnalis)
Amphipoda – Genus. Hyalella, Gammarus, Echinogammarus, Crangonyx, and Diporeia (formerly Pontoporeia; genus Monoporeia no longer exists). Mature specimens of Gammarus should be taken to species to check for G. tigrinus (another invasive). You will have to look at many of the distinguishing features anyway in order to distinguish between Echinogammarus and Gammarus. Diporeia typically occurs below the thermocline, so be suspicious if something keys to this genus. We should keep an eye out for Corophium, an invasive that looks nothing like the others. Also watch for the invasive blood red shrimp (Hemimysis anomala); it looks like a shrimp.
Isopoda – Genus. Caecidotea/Asellus all called Caecidotea. Lirceus is the only other genus.
Gastropod and Bivalvia: Empty shells should NOT be counted or identified, even if they look “fresh”. Do not ID, do not count, do not enter in database.
Gastropoda – For all families except Hydrobiidae, identify to genus unless too immature (less than ~3.5 whorls) or damaged. Immatures should be left at family unless genus is obvious (e.g. Promenetus, Valvata tricarinata, Physa). We may find invasive snails if we are watchful. Notes for each family follow:
Family Hydrobiidae (w/operculum): Leave at family level. Small size distinguishes this family from Viviparidae. Paucispiral operculum retracted well into shell distinguishes it from Bithyniidae. Teardrop-shaped, paucispiral operculum distinguishes from Valvatidae.
Family Pleroceridae (Prosobranch – w/operculum): ID to genus, though we’ve seen too few to be sure if this is always possible. Uncommon family. Easily distinguished from all others by elongate, smooth-sided spire (totally-flat to slightly-inflated whorls – look at pictures to see what I mean).
Family Viviparidae (Prosobranch – w/operculum): Genus, though immatures can be tricky, even though they are fairly large. Adults are very large and can have many whorls. Includes the giant invasive Cipangulopaludina, which has an outer angle, or crest, on exposed whorl only when it is immature. T&C key generally adequate, though we have seen too few to be certain. Distinguish from Bithyniidae by retracted operculum (and large size if mature). Distinguish from Hydrobiidae and Valvatidae by concentric operculum and much larger size (unless very young).
Family Bithyniidae (Prosobranch – w/operculum): Genus. Only the invasive Bithynia tentaculata is in the Great Lakes. Easily distinguished from all others by teardrop-shaped, calcareous (hard, whitish), and concentric operculum found right at the aperture lip – never retracted into body whorl. Often there are one or two very obvious concentric growth rings on operculum. Overall shell shape is neatly conical – neither especially elongate or wide. Size of mature (~4 whorls, up to 15 mm) always larger than Hydrobiidae.
Family Valvatidae (Prosobranch – w/operculum): Genus (all are Valvata). Distinguished from all other families by the following features. Total shell shape is small (hence, not Viviparidae) and wider than it is high (i.e. low spire), approaching shape of Planorbidae at times. Operculum is very round, nearly circular, and multispiral. V. tricarinata and V. bicarinata very obvious by their ridges.
Family Physidae (Pulmonata – w/o operculum): Genus. Most common genus is Physa, but Physella and Aplexa may also be present. Caution: In Peckarsky et al., the couplet separating Physa from Physella contains a typo. Use Thorp and Covich for this distinction.
Family Planorbidae (Pulmonata – w/o operculum): Genus. Mature specimens can be distinguished partly by size. Large snails (~2 cm diameter when fully mature) are Helisoma or Planorbella. Small-to-intermediate (~6-8 mm) mature snails are usually Planorbula. Small genera include Gyraulus, Promenetus, Menetus, Armiger. Be very careful with immatures. Small Planorbula are distinguished from Gyraulus etc. by aperture shape (aperture height >= aperture width; whereas Gyraulus aperture width > aperture height, and whorl height not increasing with age). When Helisoma and Planorbella are small, their shape is quite different from the adult form, and from Planorbula and Gyraulus shapes. Best to leave at family level when in doubt. When mature, the two large genera are distinguished by careful use of T&C key characters (keep in mind that “left side” and “right side” refer to the animal’s left and right side in its natural posture).
Family Lymnaeidae (Pulmonata – w/o operculum): Genus. Small snails that are fully mature are usually Fossaria. Acella is freakishly long and skinny, and Radix has a freakishly flared aperture. Pseudosuccinea has a very high aperture relative to spire height, a thin shell, and the animal can’t fully retract into shell, so its foot sticks out even when preserved. Stagnicola can be difficult. It can look like Fossaria when small. Usually differs from mature Lymnaea by being more narrowly elongate and often having noticeable criss-cross texture on shell, unlike Lymnaea with its more flared aperture (relative to spire width) and smooth shell (see picture for comparison).
Family Ancylidae (Pulmonata – w/o operculum): Genus. Don’t need shell. Look at pseudobranch under mantle edge on left rear portion of animal. Ferrissia has a single, simple flap, while Laevapex has complex, folded flap(s).
Bivalvia – Genus when possible.
Psidiidae (formerly Sphaeriidae): Family. For proper genus ID, valves must be separated so cardinal teeth can be viewed. If shells are dissolved or too thin, you can often identify genus Pisidium by its noticable asymmetry (but not all species). If you have mature individuals with intact shells, Musculium can often be determined by the presence of umbo “caps”, and Sphaerium can sometime be distinguished by its size, being the largest of the three genera. See key by Mackie.
Corbiculidae: The invasive Corbicula fluminea is properly distinguished from Psidiidae/Sphaeriidae by looking at cardinal and lateral (a.k.a. “hinge”) teeth, but it is a much larger animal, so mature individuals may be distinguishable by its size (>2.5 cm). Rare in our samples but empty shells can be found, especially in western Lake Erie.
Dreissenidae: Genus, species whenever possible. Easy enough to distinguish family by shape. We may have Mytilopsis as well as Dreissena. Checking on this. Please note species in comments if possible. D. polymorpha distinguished from D. bugensis by more triangular shape. Polymorpha should sit up on flat bottom, while bugensis fall over and do not have a flat “bottom”.
Unionidae: Genus. Shouldn’t be in samples, but can be taken to genus if found.
Crayfish – Take mature specimens to genus; immatures that are difficult to identify can be left at family.
Do not identify unless noted below.
Zooplankton: we are NOT counting or IDing zooplankton because our sampling method is not geared to sampling these properly. Doubtless many will appear in our samples because it’s sometimes hard not to pick them in the field. Do not count, do not ID, do not enter in database (but you can keep an eye out for the weird invasives Cercopagis, and others, and note these in the notes section of the database (see notes below)).
Misc. funky-looking taxa that may perplex:
Difflugia and other testacean protists – Do not identify or note. Amoeboid protozoa with balloon-shaped tests (cases usually made of tiny sand grains or proteinaceous plates. Tests are large enough to see, tough enough to survive rough handling and preservative, and occasionally occur in samples.
Sponges – Note as present, common, abundant. Small sponges and fragments, as well as star-shaped spicules, are easily overlooked, but should be noted as present, common, or abundant. Not at all uncommon in Great Lakes habitats. Where there are sponges, there may also be spongilla fly larvae (Neuroptera: Sisyridae). See M&C.
Bryozoa – Note presence. Not uncommon but often overlooked coral-like colonial animals. Statoblasts (resting cell clusters in characteristic cases) are common in samples. Far less common are colonies, which may be clusters of jelly-coated individuals or may be small, branching bits easily mistaken for plant parts. Presence should be noted. See T&C and Pennak for pictures of statoblasts.
Cnidaria – Identify if possible. In addition to the common Hydra, watch for: 1) the invasive hydrozoan Cordylophora (reported from the Detroit River and Lake Erie). It differs from Hydra in the location of its tentacles (the tentacles occur all the way up the body rather than being restricted to the oral end), and in the fact that it is often a branched, colonial animal. It could occur as a colony or individual polyp in samples. Note pictures in T&C and Pennak for comparison; 2) the freshwater jellyfish Craspedacusta (also see pictures in reference books), which occurs in the region, though it is highly unlikely to occur in Great Lakes habitats (we haven’t seen it).
Turbellaria – Leave at this level. If it is flat (-ish), soft, non-segmented, and generally featureless (no suckers, no segments, no chaetae/setae), it’s probably a flatworm. Note that most of our turbellaria have mid-ventral mouths, but some have terminal mouths.
Nemertea – A.k.a. “proboscis worms”. Supposedly there are small species in the Great Lakes, but I don’t know if/how we would recognize them, unless their proboscis is extruded. They would most likely be mistaken for oligochaetes.
Nematomorpha – Leave at this level. A.k.a. “horshair worms”. Sort of like freakishly long (e.g. 10 cm), black nematodes. With tough cuticle, but external features lacking, except small bifurcation at anal end. Usually endoparasites of insects, only reproductive adults are free-living. Very long, thin, tough, stiff, unsegmented, and dark compared to any oligochaetes.
Manayunkia speciosa – Identify. The only Polychaete (Annelida) worm occuring in the Great Lakes. Small worm (up to 5 mm). Head with broad crown of branched tentacles; builds a tube of fine sediment and could be mistaken for a tiny chironomid if one doesn’t examine the head.
Chaetogaster – Identify as an oligochaete. A predaceous naided worm with conspicuous body regionalization, rather than regular ring segments. Small (typical Naidid size), and generally transparent in samples. Can reproduce by budding, like other Naidids, so may look even weirder if caught in the act.
Dero – Identify as an oligochaete. Naidid worm with short anal tentacle-like gills.
Branchiura – Identify as an oligochaete. Large tubificid worm with conspicuous feather-like fringe of gill filaments on opposite sides of body at posterior end.
Branchiobdellida – Do not identify. Crayfish parasites formerly grouped with leeches. Unlikely to occur in samples unless crayfish were taken as well (the worms may detach and crawl free in the preservative). With leech-like anal sucker, but body is cylindrical and may have dorsal projections. See references for pictures.
Leptodora, Polyphemus, Bythotrephes, Cercopagus – Note presence. Notify Val if Cercopagus found in Lake Superior (Sea Grant needs to know). Strange-looking Cladocera best described with pictures. The last two are invaders and may not be described in reference books. Google ‘em.
Argulus – Do not identify. A.k.a. “fish lice”. Formerly considered a copepod. They are ectoparasites of fish and are best described with a picture. It’s not so odd to find them detached from their fish hosts.
Freshwater shrimp – Identify to genus. Not really weird, but it should be noted that they occur in Lake Erie and Lake St. Clair, and are distinct from crayfish. Palaemonidae (genus Palaeomonetes) is the only family we would find. See T&C. Again, keep an eye out for the invasive gammarid, Hemimysis anomala, which has been found in lakes Michigan, Erie, and Ontario, and is likely spreading rapidly. It does not seem to favour wetland habitat, but we may find them in our samples.
Echinogammarus – Identify to genus. Also not weird, but a common invasive Gammarid amphipod that looks much like Gammarus and is not in the reference books. Distinguish by presence of very large outer ramus (exopod) on third uropod, with very small, scale-like inner ramus (endopod). Telson lobes are quite short and have small spines at the ends. Very characteristic shape. Best to see a picture.
Corophium – Identify to genus. An invasive amphipod that looks a bit like an isopod – somewhat dorsoventrally flattened. More of a marine-like body shape. We haven’t seen it yet.
Misc. funky-looking things that may be attached to invertebrates: Note presence and abundance (present, common, abundant) for some types
Stalked ciliates (e.g. Vorticella) and rotifers: note presence and abundance. Often appear as round, white things in small groups attached by thin stalks to various parts of various animals. Very typically occur on faces of baetid mayfly nymphs.
Fungal filaments can extend from the bodies of various animals, giving a somewhat hairy appearance. These are probably usually an indication that the animal was dead (or very sick) when collected.
Immature stages of aquatic mites: Note presence and abundance. These are parasitic, and appear as whitish, teardrop-shaped objects stuck to insects. A pair of eyes is often the only distinguishable external feature, but even these may be absent. Legs are usually absent, but may occur in rudimentary form. The pointed end of the “teardrop” is usually affixed to a vulnerable part of the insect, such as the non-sclerotized tissues between segments.
Various mineral and organic deposits and precipitates can occur on a variety of animals. The outer layer of mollusc shells is a proteinaceous periostracum, which often “attracts” such deposits, such as rust-colored iron oxides. Some animals are hairy (e.g. Odonata: Libellula nymphs) or secrete mucous coverings (e.g. many chironomid larvae), which allows them to camouflage themselves by holding a covering of dirt/detritus.