Introduction to This Module

Home , Cataclysta lemnata, Chirocephalus diaphanus, Elophila nymphaeata, Parapoynx stratiotata, Raft spider

MODULE 9: ADVANCED IDENTIFICATION OF MISCELLANEOUS TAXA INCLUDING CRUSTACEA - BY TERRY GLEDHILL AND IAN WALLACE

Introduction to this module

To include: Crustacea (with tips on the identiﬁcation of zooplankton), freshwater arachnids, Bryozoa, Lepidoptera and Megaloptera and Neuroptera.

This module provides guidance on the very important groups of Crustacean arthropods and also serves as a “catch- all” for some small, but fascinating invertebrate groups which do not warrant modules of their own. These are i) the water spiders and their relatives the freshwater mites (a large group which to date are difficult to identify, but which might prove important in water quality terms in the future, ii) the moss animals or Bryozoa, iii) the moths with aquatic larvae, iv) the alderflies, aquatic lacewings and spongeflies (N.B. alderflies were covered in module 2 and will only be given a brief mention here).

As with the other modules, there are mandatory exercises which will be marked by your tutor. You can submit them by printing out this workbook and ﬁlling in the appropriate spaces by hand (but please add your name to the front of the workbook), or you can use the template appended to the introductory part and send completed exercises by email. Completion of this module will give you the Advanced Level for identiﬁcation of miscellaneous taxa including Crustacea.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 2 of 68 SECTION 1: CRUSTACEA

For this section you’ll need a copy of the following FBA Keys: British Freshwater Crustacea Malacostraca: a key with ecological notes (Gledhill et al., 1993); British Freshwater Cladocera (Scourﬁeld & Harding, 1966); A Key to the British Freshwater Cyclopoid and Calanoid Copepods (Harding & Smith, 1974).

The freshwater crustacean fauna of Britain and Ireland can be split into various groups: the small (often microscopic) planktonic and sometimes benthic cladoceran and copepod water ﬂeas and seed shrimps and the larger fairy, brine and tadpole shrimps. With the exception of the bathynellids which are c. 1mm long, the other major group comprises the larger crustaceans (Malacostraca), which includes the mysid shrimps, amphipod shrimps, water hog lice, crabs and crayﬁsh.

Some particular features that may be useful for separating these groups are: 1) Size 2) Shape 3) If alive, swimming movement 4) Colour and patterning In places, pointers will be given to identiﬁcation features. These are not deﬁnitive, but may be helpful when looking at some specimens.

It is helpful to view specimens alive where possible, and observe their movement and colour (for example, when separating the families of freshwater shrimp Gammaridae and Crangonyctidae, the former tend to be pinkish when alive and crawl or scuttle on their sides, whilst the latter are more transparent with a bluish tinge and tend to ‘walk’ in an upright position).

If looking at preserved specimens under the microscope, make sure that they are completely covered by a layer of water or preservation ﬂuid to prevent reﬂections which can produce artefacts.

Depending on the preservative used, colours may be leached or misrepresented, and therefore are not a reliable character in preserved specimens.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 3 of 68 SECTION 1: CONTINUED

1.1 Other Crustacea

Fairy shrimps, brine shrimps, tadpole shrimps, and cladoceran water ﬂeas (Class BRANCHIOPODA)

• There are four small orders: Conchostraca (clam shrimps – now split into three separate orders: Cyclestherida, Laevicaudata, Spinicaudata - which will not be covered any further in this module as they are not found wild here); Anostraca (fairy shrimps); Notostraca (tadpole shrimps) and Entomostraca (cladoceran water ﬂeas)

Fairy shrimps • One species: Chirocephalus diaphanus

• Pointers to identiﬁcation: eleven pairs of thoracic limbs (maximum length 35mm); swims with appendages uppermost and back acting as a keel; eyes are usually fairly large and carried on stalks; transparent body which often has brightly coloured parts (tips of limbs and tail may have a reddish hue) (see Fig. 1.1.1) Fig. 1.1.1 Fairy shrimp

• Only found in shallow, temporary pools e.g. in the New Forest

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 4 of 68 SECTION 1: CONTINUED

Brine shrimps • One species: Artemia salina

• Pointers to identiﬁcation: resembles Chirocephalus but much smaller (maximum length 15mm) (see Fig. 1.1.2)

• Rare, found in brackish water bodies

(a) (b)

Fig. 1.1.2 (a) Adult brine shrimps swimming, (b) juvenile brine shrimp (reproduced from Natural History of the British Entomostraca, Ray Society)

Tadpole shrimps • One species: Triops cancriformis

• Pointers to identiﬁcation: broad oval carapace (maximum length 40mm) with two long tapering tails and many pairs of limbs which they use for swimming, although these may be hidden under the carapace (see Fig. 1.1.3)

• Found in small, shallow, muddy temporary pools, rare in British Fig. 1.1.3 Tadpole shrimp Isles

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 5 of 68 SECTION 1: CONTINUED

Cladoceran water ﬂeas • There are many genera, families and species

• Pointers to identification: the characteristics used for identification include antennal length and segments, carapace shape (maximum length c. or below 4mm) and markings (see Fig. 1.1.4). Refer to FBA key to take identification further

• Many species are truly planktonic, but several families crawl and are associated with vegetation

• Predaceous cladocera can be longer than 10mm, but these are truly planktonic, very transparent, elongated with a residual carapace, and are only found in lakes Fig. 1.1.4 Cladoceran water flea

Seed shrimps (Class OSTRACODA) • Around 90 species

• Pointers to identiﬁcation: Valve shape can be used as a pointer, but identiﬁcation of genera requires dissection; do not confuse with small bivalve molluscs. The body is enclosed in an oval carapace made up of two halves, which may look like a bivalve shell (fairly transparent when they are alive), but they have jointed Fig. 1.1.5 Seed shrimp limbs and other appendages, which bivalves do not have. These appendages may not be immediately visible, or only partially showing (see Fig. 1.1.5)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 6 of 68 SECTION 1: CONTINUED

• They are generally associated with the substratum, although they can be found in the plankton. They are found in both rivers and stillwaters, and in large numbers in interstitial spaces, but you are not likely to ﬁnd many in standard net samples, though occasionally can be hugely abundant in benthic sweeps from silty substrata

• They may go through a 1mm mesh although Gigantocypris grows to over 1mm long

• Tips on preservation:

• Do not preserve in concentrated ethanol, methanol or formalin, as these can cause the shells to decalcify

• In order to preserve with open valves and show appendages use 70-80% alcohol, to preserve with closed valves (best for observing overall shape) use a solution of glycerine in 80-90% alcohol (Bronshtein, 1988)

• The British key “Freshwater Ostracods” by P.A. Henderson, (1990, Linnean Society) has been out of print for some time but can be obtained as CD ROM (Pisces Conservation Ltd, July 2002)

Ref: Z. S. Bronshtein (1988) Fresh-water Ostracoda A. A. Balkema, Rotterdam

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 7 of 68 EXERCISE 1

Find an example of a cladoceran water ﬂea and an ostracod in your samples, and note down (and draw) the morphological differences between the two

Mark = / 10

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 8 of 68 SECTION 1: CONTINUED

Copepod water ﬂeas (Class COPEPODA)

• There are three orders which share some common characteristics: Cyclopoidea; Calanoidea; Harpacticoidea. They all have five pairs of limbs, a single median eyespot, and can be planktonic or benthic, and many would pass through a 1mm mesh. In all three groups the characteristics used for identification include appendages and spines on different legs. Take care when examining organisms, as egg sacs may be dislodged from some of the individuals, so try to look at more than one. Refer to FBA key to take identification further for calanoids and cyclopoids (FBA key only covers females).

Order Cyclopoidea • There are a number of genera, and depending on the authority, a variable number of species (~50)

• Pointers to identiﬁcation: tear drop shaped body and antennae which are not longer than the length of the body; segments of appendages are important for identiﬁcation; females have two egg sacs (see Fig. 1.1.6)

• They are found throughout the whole water column, some near the substratum and some in the Fig. 1.1.6 Cyclopoid copepod plankton, in both rivers and stillwaters

Order Calanoidea • Fourteen species (FBA key)

• Pointers to identiﬁcation: Antennae much longer than length of whole body; females have a single egg sac (See Fig. 1.1.7) Fig. 1.1.7 Calanoid copepod

• Generally planktonic and only found in lakes (this group is mostly marine, with only remnant species in freshwaters)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 9 of 68 SECTION 1: CONTINUED

Order Harpacticoidea • Around 40 species

• Pointers to identiﬁcation: slim, elongate body shape with somewhat parallel sides and reduced antennae; will usually go through a standard 1mm pond net mesh (see Fig. 1.1.8)

• Benthic and found in interstitial spaces, found in both rivers and stillwaters

Fig. 1.1.8 Harpacticoid copepod

Fish lice (Class BRANCHIURA) – one family

• Three species: Argulus coregoni and Argulus foliaceus are both native; Argulus japonicus has been recorded in exotic ﬁsh, but is very rare

• All are ectoparasites which drop off and swim in the plankton to ﬁnd another ﬁsh host and therefore may be found in net samples

• Pointers to identiﬁcation: the species can be distinguished by tail shape: Argulus coregoni – abdominal lobes (extensions from the back of the body) (see Fig. Fig. 1.1.9 Fish louse 1.1.9, Fig. 1.1.10) sharply pointed; Argulus foliaceus – abdominal lobes broadly rounded; Argulus japonicus – abdominal lobes narrowly rounded and twisted to the side

• Found in both rivers and stillwaters

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 10 of 68 SECTION 1: CONTINUED

(a) (b)

(c)

Fig. 1.1.10 Shape of abdominal lobes (indicated by arrows) (a) Argulus coregoni (b) Argulus foliaceus (c) Argulus japonicus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 11 of 68 SECTION 1: CONTINUED

1.2 Larger Crustacea (Class MALACOSTRACA)

All the organisms in this class have eight thoracic segments (only seven visible in amphipods as the ﬁrst is fused with the head), six abdominal segments, and a tailpiece called a telson. The telson is attached to the upper edge of the last abdominal segment and may be very small, as in Gammarus, or very large, as in the crayﬁsh. A planktonic form within the Malacostraca, Mysis, is very rare in Britain and may be extinct, although it is more common in Ireland.

Bathynella (Order Bathynellacea) - one family in Britain and Ireland

Family Bathynellidae • Two species : Antrobathynella stammeri and Bathynella natans (although the latter may be a misidentification of the first) Fig. 1.2.1 Bathynellid • Pointers to identification: very small (c. 1mm long); eyeless and almost colourless; elongate body form (see Fig. 1.2.1)

• They are rarely caught in standard net samples as they inhabit interstial spaces in riverine gravels, also found in caves and wells

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 12 of 68 SECTION 1: CONTINUED

Mysis (Order Mysidacea) – one family

Family Mysidae • One true freshwater species: Mysis relicta

• One brackish water species that can survive in freshwater: Neomysis integer

• Pointers to identiﬁcation: can be separated from amphipods and isopods by the presence of a carapace (see Fig. 1.2.2). Mysis may be confused with some decapod shrimps, but these are marine, although they may be found in brackish water – they can be separated by the structure of the limbs on the thorax, which have two branches in Mysis

• It is found in lakes and large rivers and is planktonic

• Rare in the UK, found only in Ennerdale Water in the Lake District (where it may now be extinct), more common in Ireland

• Neomysis integer is common and widespread in coastal drains and Fig. 1.2.2 Mysis relicta rivers, usually where there are brackish inﬂows, but frequently upstream of tidal sluices. It does not survive very long in full freshwater, and does not penetrate very far upstream as a result

• One invasive species: Hemimysis anomala

• Hemimysis anomala was ﬁrst recorded in the UK in 2004. Adults may be deep red to an ivory-yellow in colour. The shape of the telson is the key character for identifying this species. The telson is elongate, rectangular without any trace of a median cleft; it carries a row of short spines along the sides and a pair of longer spines at the posterior corners.

If you suspect you may have found Hemimysis anomala, please send a photo and details of location to [email protected]

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 13 of 68 SECTION 1: CONTINUED

Freshwater shrimps (Order Amphipoda) – ﬁve families

The main characteristic of this group is that they are compressed side to side in contrast to isopods which are compressed top to bottom. As with other groups, it is important to become familiar with the morphology (see Fig. 1.2.3).

epimera 2-3

Fig. 1.2.3 Body parts of typical amphipod

Note: with all the amphipods, it is easier to identify mature adult males, and you are advised to select a male specimen for species identiﬁcation. To tell if your specimen is a male, look between the last pair of walking legs or pereopods (see Fig. 1.2.3 p7), males have a pair of genital papillae (see Fig. 1.2.4a, b). Mature females have centrally-directed ﬂat plates fringed with long hairs, oostegites, on pereopods 2-5 (do not confuse with gills which are present on all the walking legs and hang downwards).

Fig. 1.2.4 (a) (a) (b) Genitalia of male amphipod showing genital papillae (circled) (b) cross section of body segment 7 showing pereopod (basis), gill and genital papillae (genitalia)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 14 of 68 SECTION 1: CONTINUED

Two families of the amphipods have obvious antennae which can be used to separate them from the other three (see below).

Family Corophidae • Two common species: Corophium curvispinum and Corophium multisetosum

• Pointers to identiﬁcation: First antenna although they are somewhat compressed side to side, they can be distinguished from other amphipods by having a more rounded body shape Second antenna and possessing very enlarged second antennae (see Fig. 1.2.5), the largest Fig. 1.2.5 Corophid shrimp showing enlarged second antenna and spike (circled) segment of which has a curved spike, the shape of this spike can be used to differentiate the species (see Fig. 1.2.6):

• Corophium curvispinum has one large curved spike with two smaller accessory processes on the same segment of the antennae (see Fig. 1.2.6a)

• Corophium multisetosum has a single large curved spike (see Fig. 1.2.6b)

• Corophium spp. are tube builders, they can also burrow into soft substrate and are associated with brackish and marine conditions. Only Corophium curvispinum is known to occur in inland freshwaters and is found in canals and slow ﬂowing rivers; Corophium multisetosum can tolerate freshwater and may be found in the lower reaches of rivers Note: Some species e.g. Corophium lacustre will occur at the downstream end of normally freshwater habitats e.g. South Forty-Foot Drain, Lincs.

Fig. 1.2.6 Close up of spikes in (a) (a) (b) Corophium curvispinum (accessory processes obscured by hairs) and (b) Corophium multisetosum with no accessory processes

Ref: R.J. Lincoln, (1979). British Marine Amphipoda: Gammaridea, British Museum (Natural History), London.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 15 of 68 SECTION 1: CONTINUED

Family Talitridae First pair of antennae • One species: Orchestia cavimana

• Pointers to identiﬁcation: can be distinguished from other amphipods by having a very short pair of ﬁrst Second pair of antennae antennae (see Fig. 1.2.7), which are less than a Fig. 1.2.7 Talitrid shrimp showing short pair of quarter of the whole length first antennae (circled) of the second antennae

• The eyes of Talitridae are completely circular compared to Gammaridae and Corophiidae

• Semi-terrestrial, occurring in burrows at the edges of rivers and canals; they escape in a series of hops when disturbed (like the talitrid sandhoppers of the seashore)

Pointers to separating the remaining amphipod families The remaining three families may look very similar. The following are some pointers which may help you to separate some of the groups: • There are two families which have eyeless members: Crangonyctidae (Crangonyx subterraneus) and Niphargidae (all are eyeless). These can be separated by looking at the gnathopod hands (the two pairs of limbs directly in front of the ﬁrst pair of walking legs) (see Fig. 1.2.3). Those of Crangonyx subterraneus are longer than broad while those of Niphargus are as long as broad i.e. more square (see Fig. 1.2.8).

Fig. 1.2.8 Gnathopod hands: (A & B) Crangonyx subterraneus; (C & D) Niphargus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 16 of 68 SECTION 1: CONTINUED

• The other groups have eyes: Crangonyx pseudogracilis resembles Gammarus pulex. However, they tend to differ in colouration and behaviour. The former are fairly transparent with a bluish tinge and tend to ‘walk’ in an upright position whilst the latter tend to be pinkish when alive, and crawl or scuttle on their sides. A characteristic of Gammarus is that it has a long breeding season and is frequently found in pairs, with the larger male carrying the smaller female. This does not occur in Crangonyx pseudogracilis where the males are much smaller than the females. In addition, under the low power microscope, the thickest segment of the ﬁrst, second and third walking legs on Crangonyx pseudogracilis have a serrated rear edge (see Fig. 1.2.9) and the upper surface of the abdomen (particularly on the urosome – at the end of the body) is generally devoid of spines. The urosome of Gammarus has obvious spines (see Fig. 1.2.13a). Crangonyx pseudogracilis is a North American species probably brought to Britain and Europe unwittingly by man, and is now widespread.

Fig. 1.2.9 Rear edge of walking leg in (A) Crangonyx pseudogracilis, showing serrations and hairs, and (B) Gammarus pulex, showing only hairs

Family Crangonyctidae • Two species: Crangonyx subterraneus and Crangonyx pseudogracilis

• Pointers to identiﬁcation:

• These two species can be easily separated from each other by the presence or absence of eyes. Crangonyx subterraneus is eyeless and Crangonyx pseudogracilis has eyes

• Crangonyx subterraneus is known only from subterranean waters

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 17 of 68 SECTION 1: CONTINUED

• Crangonyx pseudogracilis is common in standing and slow-ﬂowing waters in much of Britain, having extended its range

• The male of Crangonyx pseudogracilis is smaller than the female

• More tolerant of low oxygen conditions than gammarid species

Family Niphargidae • Four species: Niphargus glenniei, Niphargus aquilex, Niphargus fontanus and Niphargus kochianus kochianus (Niphargus kochianus irlandicus has been recorded from caves, wells, lake bottoms and other subterranean waters in Ireland)

• Pointers to identiﬁcation: all British and Irish species in this family are eyeless and found in subterranean waters

• Characteristics which help separate the four species are body shape, maximum size, shape of the gnathopod hands, shape of the telson and shape of the epimera (the part of the abdomen that carries the pleopods)

• The epimera of Niphargus aquilex have the most rounded rear margins (see Fig. 1.2.10b). This species is also the most slender (see Fig. 1.2.11), and is the species of Niphargus most often found in surface waters

• Niphargus glenniei is very small (maximum length c. 3mm) and has, so far, only been found in Devon and Cornwall

Fig. 1.2.11 Niphargus aquilex (photo courtesy of Terry Gledhill, FBA)

Fig. 1.2.10 Second and third epimera of: (B)Niphargus aquilex showing rounded rear margin (indicated by arrow), (C) Niphargus fontanus, (D) Niphargus kochianus kochianus, (E) Niphargus kochianus irlandicus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 18 of 68 SECTION 1: CONTINUED

Family Gammaridae • Five species: Gammarus pulex, Gammarus lacustris, Gammarus duebeni, Gammarus zaddachi and Gammarus tigrinus.

• Be aware of the invasive species: Dikerogammarus villosus (often referred to as the killer shrimp)

Pointers to separating the species in the gammarid family • Colour:

• Grey/dirty brown/pink – G. lacustris, G. duebeni and G. pulex (Note on preservation: G. pulex and G. duebeni go orange when put in dilute formaldehyde whilst G. lacustris remains a grey/ dirty brown/pink colour)

• Stripey – G. zaddachi (this may also have orange spots, but don’t confuse these with the orange parasite spot - larval stage of the thorny-headed worm parasite, Acanthocephala, which has a ﬁnal host in ﬁsh - often seen in gammarids). G. zaddachi and G. tigrinus are both brackish water species, and tend to be larger and more hairy than freshwater ones. A potentially unreliable distinction between these two species is that in G. tigrinus the stripes are in the middle of each thoracic segment, whilst in G. zaddachi the stripes are at the junction of segments

• Eye shape (see Fig. 1.2.12):

• Kidney bean shaped (twice as long as broad) - G. zaddachi, G. duebeni and G. tigrinus (see Fig. 1.2.12b)

Fig. 1.2.12 Eyeshape of (A) Gammarus pulex and (B) Gammarus duebeni

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 19 of 68 SECTION 1: CONTINUED

• Not notably kidney bean shaped i.e. more rounded - G. lacustris and G. pulex (see Fig. 1.2.12a)

Fig. 1.2.13 Urosome of: (a) Gammarus lacustris (b) Gammarus duebeni showing ‘humped’ appearance

Pointers to separating G. zaddachi, G. duebeni and G. tigrinus • Epimera (ﬁrst three segments of the abdomen, behind the segments that carry walking legs, each carries a pair of pleopods) and pereopod spine/s (spine on inside of largest (basal) segment of last walking leg):

• Epimeron 2 and 3 more right angled and spines not present on base of pereopod 7 - G. duebeni

• In side view the dorsal edges of the urosome segments are somewhat ‘humped’ (see Fig. 1.2.13b) - G. duebeni

• Epimeron 2 and 3 acutely angled and two spines present on pereopod 7 (although one may be missing), generally hairy all over especially the antennae - G. zaddachi and G. tigrinus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 20 of 68 SECTION 1: CONTINUED

• Antennae:

• Antenna 1 slightly longer than antenna 2 with long straight hairs on antennae of large males - G. zaddachi

• Antenna 1 slightly shorter than antenna 2 with long curled hairs prominent on antenna 2 in large males but absent in females - G. tigrinus

Pointers to separating G. lacustris and G. pulex • This is actually quite a difﬁcult thing to do

• Habitat:

Fig. 1.2.14 Setation on the mandible palps of Gammarus spp.

• G. lacustris is more often found in lakes and rarely found in rivers, and is generally a northern species in the UK, but both G. lacustris and G. pulex can be found in lakes

• Pereopod spine (spine on inside of last walking leg) and epimera:

• Spine not present on basal (large) segment of pereopod 7 and epimeron 2 posterior corner as acutely produced as that of epimeron 3 - G. lacustris

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 21 of 68 SECTION 1: CONTINUED

• Pereopod 7 with the largest segment possessing a spine on the inside and epimeron 2 posterior angle is sub-acute and squarish with angle of 90o - G. pulex

Setation on the mandible palps of Gammarus spp. The number and grouping of setae on the mandibular palps is a useful character that is reliable and diagnostic for immature as well as adult specimens of both sexes (see Fig. 1.1.14, Table 1). Table1. Distribution of lateral lines or groups of setae on the outer face of the mandible palp article 3, and number of setae on the ventral margin of article 1, in five Gammarus species found in Britain.

Species No. of lateral lines on article 3 No. of setae on article 1 G. duebeni 1 1-2 G. lacustris 10 G. pulex 10 G. tigrinus 1-2 0 G.zaddachi 3-5 1-4

Note: Echinogammarus is a species only found in the Channel Islands, it is very hairy, refer to FBA key for further notes.

Identification of Dikerogammarus villosus Dikerogammarus villosus (often referred to as the killer shrimp) is an amphipod native to south-eastern Europe, which has recently spread to western Europe. In September 2010 it was found in Grafham Water, Cambridgeshire. Size and colour are useful aids to identification, but the projections on the urosome are definitive. If you suspect you may have found Dikerogammarus, please send a photo and details of location to [email protected]

Maximum body length: Crangonyx pseudogracilis: 10 mm Gammarus species: 20 mm Dikerogammarus villosus: 30 mm

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 22 of 68 SECTION 1: CONTINUED

Body colour: Crangonyx pseudogracilis: Bluish-white (when live) Gammarus species: Striped or uniform Dikerogammarus villosus: Striped or uniform Features on urosome: Crangonyx pseudogracilis: Urosome generally smooth (short ﬁne setae may be present) Gammarus species: Dorsal setae or spines present on all three segments Dikerogammarus species: Urosome segments 1 and 2 each with a dorsal projection

Crangonyx pseudogracilis Gammarus sp.

Dikerogammarus villosus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 23 of 68 EXERCISE 2

Find the genital papillae in a mature male amphipod and take a photograph

Mark = / 5

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 24 of 68 EXERCISE 3

Identify a Gammarus pulex and ﬁnd the spine on the inside of the last walking leg, take a photo or make a drawing

Mark = / 5

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 25 of 68 EXERCISE 4

Remove the mandible and mandible palp of a specimen and draw the setation (pattern of hairs) of the outer face and name the species

Mark = / 10

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 26 of 68 SECTION 1: CONTINUED

Water hog lice (Order Isopoda) – one family

The main characteristic of this group is that they are compressed top to bottom in contrast to amphipods which are compressed side to side (see Fig. 1.2.15). They have seven pairs of jointed limbs (walking legs) and look like woodlice.

Fig. 1.2.15 Typical amphipod showing top to bottom compression

Family Asellidae • Four species: Proasellus cavaticus, Asellus communis, Asellus meridianus and Asellus aquaticus

• Pointers to identiﬁcation:

• Eyeless, slender body shape and without pigment, usually found in subterranean waters - Proasellus cavaticus (see Fig 1.2.16a)

• Two pale head spots (see Fig. 1.2.16b) - Asellus aquaticus and Asellus communis (best to look at several individuals when looking for this feature), Note: A. communis has only been recorded from a single location in the UK, Bolam Lake in Northumberland

• One continuous white patch on head (see Fig. 1.2.16c) (this pattern may be obscured by detritus, so use a needle to clean it off before making observations) - Asellus meridianus

Fig. 1.2.16 Head markings of: (A) Proasellus cavaticus, (B) Asellus aquaticus and Asellus communis and (C) Asellus meridianus

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 27 of 68 SECTION 1: CONTINUED

Shrimps, crabs and crayﬁsh (Order Decapoda) – ﬁve families

This group has some very distinctive body shapes which help with initial separation of families. All have ﬁve pairs of jointed limbs, the front two of which have distinct claws (except in the shrimps). The Palaeomonidae are shrimps and shrimp-shaped, the Astacidae and Cambaridae are crayﬁsh and shaped like a small lobster, and the Grapsidae and Portunidae are crabs and crab-shaped! All have prominent compound eyes on stalks.

Remember that the larger benthic Crustacea (crayﬁsh and crabs) will often be under-represented in kick samples and other active sampling methods; they are most effectively caught using baited traps or using the “standard method” (Peay Methodology, Peay, 2003). Note that trapping and handling the crayﬁsh requires a licence.

Ref: Peay S (2003). Monitoring the White-clawed Crayﬁsh Austropotamobius pallipes. Conserving Natura 2000 Rivers Monitoring Series No. 1, English Nature, Peterborough.

Family Palaeomonidae (shrimps) • Brackish water shrimps which have a wide salinity tolerance i.e. a tolerance of changing conditions rather than being an estuarine animal

• There are several species which ﬁt into this category including Crangon crangon (common shrimp) which is frequently found in brackish waters, and Palaemonetes varians and Palaemon longirostris which have been found in large rivers in the southern half of Britain

• Pointers to identiﬁcation: they have a carapace (see Fig. 1.2.17) but can be distinguished from mysid shrimps as the latter have limbs on the thorax which are two branched

Fig. 1.2.17 Palaeomonid shrimp

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 28 of 68 SECTION 1: CONTINUED

Family Astacidae (crayfish) • Five species: Austropotamobius pallipes (white-clawed native crayfish), Pacifastacus leniusculus (signal crayfish), Astacus leptodactylus (Turkish long-clawed crayfi sh), Austropotamobius torrentium (stone crayfish) and Astacus astacus (red-footed or noble crayfish)

• Eight species of crayfish have been recorded in Britain (five in the family Astacidae and three in the family Cambaridae). Of these, only the white clawed crayfish, (Austropotamobius pallipes) is native and only one other, the signal crayfish (Pacifastacus leniusculus) is widespread. Both species are in the family Astacidae.

• Pointers to identiﬁcation: The two families are distinguished by examining the inner margin of the small segment immediately behind the claw (see Fig. 1.2.18). A large curved spine indicates that it is in the Cambaridae; if there is no Fig. 1.2.18 Spine of Cambaridae spine, it is in the Astacidae.

• Note: some large males of the native crayfish can have one or more relatively strong spines in the same position, which may be mistaken for a spur. Confirmation of identification should be made using additional characteristics.

• White clawed crayfish have been designated a BAP priority species and are protected by legislation. It is therefore important to note the location of any native crayfish found. They are under threat from the signal crayfish which out-competes the smaller native species and also carries a fungus (crayfish plague) to which it is immune but which is devastating to native populations.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 29 of 68 SECTION 1: CONTINUED

• White-clawed crayﬁsh - One pair of spines behind the eyes (see Fig. 1.2.19a); spines along the front of the thorax (see Fig. 1.2.19b); sides of rostrum smooth and converging towards the front (see Fig. 1.2.19c); Body generally brown, dark or olive. Claws rough; undersides of Fig. 1.2.19 White-clawed crayfish claws whitish (can have a slight pinkish tinge), lighter than uppersides.

• Signal crayﬁsh - Two pairs of spines behind the eyes (see Fig. 1.2.20a); no spines on thorax (see Fig. 1.2.20b); sides of rostrum smooth and more or less parallel (see Fig. 1.2.20c); Body, generally bluish-brown to reddish-brown. Claws Fig. 1.2.20 Signal crayfish smooth on their dorsal side, with a prominent white to turquoise patch (“the signal”) on upperside of the claw at the ﬁnger joint, and bright red on the underside.

• The Turkish crayﬁsh (Astacus leptodactylus) has toothed sides to the rostrum, spines on the carapace and long slender claws and may be a threat in the future. It is highly plague-susceptible, in common with all European species.

Family Cambaridae (crayfish) • Three species: Procambarus clarkia (red swamp or Louisiana crayfish), Orconectes limosus (striped or American crayfish) and Orconectes virilis (northern virile crayfish)

• Pointers to identiﬁcation:

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 30 of 68 SECTION 1: CONTINUED

• Orconectes limosus has characteristic dorsal chestnut marks/ stripes on the abdomen, prominent lateral spines in front of the cervical groove, a prominent spur on the carpus (penultimate segment of the big claws) and glossy claws which feel smooth to the touch. Tips of chelae (claws) orange with black band below. This species has now been recorded in ponds in the upper River Slea (Lincolnshire)

• Orconectes virilis - chelae broad and ﬂat with yellow tips, chelipeds (ﬁrst pair of pereopods that carries the claws) and walking legs have distinct orange wart-like tubercules. Recorded in the River Lee system of North London

• Procambarus clarkii - chelae red on both surfaces. Makes holes in the banks of rivers

Family Grapsidae (crabs) • One species: Eriocheir sinensis (Chinese mitten crab)

• Pointers to identiﬁcation: this species can be recognised by the thick mat of hairs on the claws (see Fig. 1.2.21)

• This is a marine species which can tolerate, and prefers to moult in, freshwater, but can not lay eggs in low salinities and must return to the sea to breed. It burrows into soft banks and has been found in the lower reaches of the Thames and other slow-ﬂowing rivers. In fully freshwater environments, only the mitten crab is likely to be encountered

Note: one species, Callinectes sapidus, in the family Portunidae is a marine species that has been found in the River Trent and is widespread in European coastal waters

Fig. 1.2.21 Chinese mitten crab showing furry front claws (circled) (photo courtesy of Terry Gledhill, FBA)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 31 of 68 SECTION 2: ARACHNIDA

• Characteristics of the group:

• Eight jointed limbs

Spiders (Order Araneae) • One species is truly aquatic

• One species: Argyroneta aquatica

• Pointers to identification: Body divided into two joined parts (there may be difficulty in distinguishing between true aquatic specimens and others that live in damp places). The body can appear silvery when underwater and the spider constructs a bell shaped web which is filled with a bubble of air from the surface

• Found in stillwaters and wetlands

• The raft spider (Dolomedes ﬁmbriatus), the wolf spider (Pirata piraticus) and the fen raft spider (Dolomedes plantarius), a BAP species, are found around water.

A key which includes all spider families likely to be found (in the Palaearctic) directly on the water surface, in vegetation in the water or in vegetation close to the shore is provided by Jager, P. (2007).

Ref: Jager, P. (2007). 1. Order Araneae. In: R. Gerecke (ed.) Chelicerata: Araneae: Acari 1. Susswasserfauna von Mitteleuropa 7/2-1. Elsevier Spektrum Akademisher Verlag, München, pp 1-13.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 32 of 68 SECTION 2: CONTINUED

Mites (Order Acari) • C. 300 species in Britain

• Pointers to identiﬁcation: the body is generally round and not divided into two parts (see Fig. 2.1), they are usually very small; characteristics used for identiﬁ cation include: mouthparts; colour (only applicable to non-preserved specimens); body shape; size; genital area; degree of scleritization; setation (patterns of hairs); to distinguish freshwater Fig. 2.1 Typical mite species from terrestrial ones that may have dropped in you need to use a microscope; water mites are often extremely colourful, particularly the stillwater forms; mites can be divided into two groups based on locomotion, swimmers or crawlers; the body shape can be globular, round, compressed top to bottom or side to side, or elongated and worm-like (see Fig. 2.2, Fig. 2.3)

• They may be very useful in the future for determining water quality, when an appropriate methodology has been developed

• They are found in both still and ﬂowing waters and also the interstitial habitat

• Life cycle: egg>larvae>resting stage>nymph>resting stage>adult

• Adults and nymphs have eight jointed legs

• Larvae have six jointed legs (they may be mistaken for an insect larvae at this stage, but because they are so tiny, they are generally not seen) and are generally parasitic (often on aquatic insects such as midges, damselﬂies etc.)

• Larvae, nymphs and some adults will pass through a 1mm mesh

• Adults and nymphs are free-living and predaceous

• Eight superfamilies

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 33 of 68 SECTION 2: CONTINUED

• In general those that occur in standing water are globular and capable of swimming by using fringes of long swimming hairs on the legs

• Some may also be side to side compressed with the legs sticking out in front

• Most running water species are somewhat compressed top to bottom and crawl (although they can still have swimming hairs)

Fig. 2.2 Range of mites showing different body shapes and markings

• Superfamily Halacaroidea – (a single family – the Halacaridae) mainly marine mites, but some have entered freshwaters; they are small and sluggish; the ﬁrst two pairs of legs point forwards and the hind ones project backwards; in true freshwater mites (most of the ones you will ﬁnd), the legs radiate all around the body, many halacarids are interstial, exclusively benthic and between 150-2000μm.

• Many larvae of terrestrial parasitengonid mites which are associated with ‘aquatic’ biotopes are similar in shape to water mite larvae

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 34 of 68 SECTION 2: CONTINUED

Tips on preservation • It is best to preserve specimens before attempting to identify them

• Do not use alcohol or formaldehyde for preservation as this makes dissection very difﬁcult

• Koenike’s fluid is generally used for preservation (two parts glacial acetic acid, five parts glycerine and three parts water) but colour is lost in this fluid so take note of this first

• Drop the specimen straight into the ﬂuid, it will scrunch up initially and then relax over three to four days, so you can examine them later, the longer you leave them the better

• The ﬂuid destroys all the internal organs allowing dissection

A comprehensive account dealing with morphology, anatomy life-histories, ecology etc., of the water mites together with keys to the eight currently accepted superfamilies and the families, genera and species of the superfamilies Stygothrombioidea, Hydrovolzioidea, Eylaoidea and Mydrachnoidea can be found in Davis et al. (2007).

Ref: Davis, C., Di Sabatino, A., Gerecke, R., Gledhill, T., Smith, H. and van der Hammen, H. 2007. 7. Acari: Hydrachnidia. In: R. Gerecke (ed) Chelicerata: Araneae, Acari 1. Susswasserfauna von Mitteleuropa 7/2-1. Elsevier Spektrum Akademisher Verlag, München, pp 241-376.

Fig. 2.3 Range of mites showing different body shapes and markings

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 35 of 68 SECTION 3: BRYOZOA

For this section you will need a copy of the FBA key - A New Key to the Freshwater Bryozoans of Britain, Ireland and Continental Europe, with notes on their Ecology (Timothy S. Wood and Beth Okamura, 2005).

Bryozoans, often referred to as moss animals (or moss animalcules), live in colonies comprised of small (1mm), physiologically connected individuals (zooids) (see Fig. 3.1).

Bryozoans can superﬁcially resemble colonial hydroids with which they could be confused. Freshwater bryozoans comprise representatives from two very distinct taxonomic groupings: the exclusively freshwater Class Phylactolaemata and the mainly marine Class Gymnolaemata – in which the only freshwater members occur in the mostly marine Subclass Ctenostomata.

Animals of this group Fig. 3.1 Zooids of Plumatella emarginata showing major occur commonly but anatomical features (modified from Wood, 1989). From Wood are often overlooked & Okamura, 2005. because they grow in cryptic habitats. Colonies are often small and can be found attached to artiﬁcial or natural hard surfaces, such as the undersides of boats, pier pilings, plastic litter, submerged tree roots and branches and sometimes on macrophytes. They grow best in places where low light levels prevent overgrowth by algae and where they are protected from siltation.

Bryozoan colonies often grow together with freshwater sponges but the latter lack the body form of Bryozoa, having no sign of zooids. Sponges also feel gritty (due to internal spicules). Bryozoan colonies can be gelatinous, in which case they may be confused with snail eggs, or comprised of tubular branches when they can resemble moss.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 36 of 68 SECTION 3: CONTINUED

Fig. 3.2 Range of lophophore structure (a) Fredericella; (b) Plumatella; (c) Cristatella (modified from Wood, 1989). From Wood & Okamura, 2005.

Each zooid possesses a food gathering organ called a lophophore which consists of ciliated tentacles which surround the mouth, its shape being a diagnostic character. Most phylactolaemates (exclusively freshwater class) have a U-shaped lophophore, with an outer row of longer tentacles, and an inner row of shorter tentacles (Fig. 3.2b, c, Fig. 3.3) when viewed from above. Species of Fredericella have a simple, circular lophophore, with a single ring of tentacles (Fig. 3.2a).

Bryozoans are suspension feeders and the mouth leads into a U- shaped gut which ends at the anus, opening outside the perimeter of the lophophore. The conspicuous and characteristic asexual reproductive bodies (statoblasts) appear as white discs when young, turning brown as they mature and can eventually be seen free in Fig. 3.3 Side view of U-shaped lophophore of Plumatella the body cavity of the emarginata (modified from Wood, 1989). From Wood & colony. The appearance Okamura, 2005. of the statoblasts is seasonal, so they are not always present, but they are very important for identiﬁcation, particularly of Plumatella – the most diverse and difﬁcult genus to identify to species level. The gelatinous forms are generally easy to identify on the basis of colony features (e.g. Cristatella).

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 37 of 68 SECTION 3: CONTINUED

The colonies are diverse in form and size, and grow through the budding of zooids. Zooids in some are budded to form branching tubules (e.g. Fig. 3.3). Zooids in gelatinous colonies are budded in a common matrix. This can result in caterpillar-like (e.g. Cristatella) or fan-like (e.g. Lophopus) colonies. In the right conditions colonies can grow rapidly, blocking pipes and creating nuisances in cooling waters of power plants and irrigation systems for golf courses.

There are 13 species in 6 families of these benthic, suspension-feeding invertebrates, widely distributed in Britain and Ireland. In most species, colonies degenerate as temperatures drop in autumn and can appear as bags or tubes full of statoblasts. However, two species can be found throughout the winter (Fredericella sultana and Lophopus crystallinus). Statoblasts are dormant and highly resistant stages, which are the main means of persistence during unfavourable conditions and of dispersal between water bodies. They range in size from 0.3-1 mm, depending on species (see Fig. 3.4).

Tips on preservation: • Bryozoan specimens should be relaxed before preservation so that the lophophores remain extended

• There are several agents suitable for this purpose including nicotinic acid, magnesium sulphate and a slow infusion of ethanol, but the most convenient is menthol

• Specimens can be isolated in a small amount of water and menthol chips ﬂoated on the surface, this is then left for about one hour. The procedure is complete when extended lophophores no longer respond to touch. Do not leave for too long as tentacles will curl and disintegrate

• 70% ethanol can then be used for preservation (absolute ethanol if samples are to be used for molecular work, then long term storage in a freezer)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 38 of 68 SECTION 3: CONTINUED

Tips on identiﬁcation of statoblasts: • Kidney-shaped statoblasts retained within colonies – Fredericella

• Oval statoblasts with no hooks or spines – Plumatella (see Fig. 3.4a)

• Statoblasts with ring of spines with hooks on end – Cristatella (See Fig. 3.4b), Pectinatella

• Lemon-shaped statoblasts – Lophopus

• Note: There are complications in that Plumatella produces both statoblasts that float (called floatoblasts) and statoblasts that are attached (sessoblasts). Fredericella produces statoblasts retained within dead branches of colonies. Gelatinous species all produce floatoblasts. Only floating statoblasts will be found in the drift

(a) (b)

Fig. 3.4 Examples of free statoblasts of (a) Plumatella fungosa. Scale bar = 0.1mm and (b) Cristatella mucedo. Scale bar = 0.25mm. From Wood & Okamura, 2005.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 39 of 68 EXERCISE 5

Floating statoblasts can be collected in drift areas in the same places that chironomid exuviae are often found. A x10 handlens can be used to ﬁnd free statoblasts clinging to ﬂoating objects at the waterline, or sieved and isolated from sediments. Isolate some statoblasts and draw the structure and identify to genus level (extra points for species)

Mark = / 10

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 40 of 68 SECTION 4: MEGALOPTERA AND NEUROPTERA

For this section you will need a copy of the following FBA key: Freshwater Megaloptera and Neuroptera of Britain and Ireland (Elliott, 2009). Also refer back to Module 2: Rapid identiﬁcation of species, Section 5: Alderﬂy larvae.

These two orders cover seven aquatic species in the UK, in three families (with only one genus per family); adults of all species are terrestrial.

These animals are clearly identiﬁable as insects, as they have three pairs of legs, plus distinct body parts. They are distinguished from all other insects by a combination of mouthpart morphology and, with the exception of Osmylidae, segmented abdominal gills. The families are straightforward to identify. • The Sialidae have a combination of opposable (pincer-like) mandibles and seven pairs of segmented abdominal gills attached laterally, so they stick out to the side when viewed from above or below; they also have a single long tail (see ﬁg. 4.1a). Larvae are found on the bed of ponds, lakes, streams and rivers.

• The Osmylidae lack obvious abdominal gills but have very clear forward-facing piercing jaws that look like slightly curved spears (see ﬁg. 4.1b). Larvae are found in moss at the sides of streams.

• The Sisyridae have less distinct jaws (see ﬁg. 4.1c), but have the seven pairs of abdominal gills, although in this case they are attached ventrally, so are only visible from below (see ﬁg. 4.3b). Larvae are found in the sponges which they eat.

(a) (b) (c)

Fig. 4.1 Examples of (a) Sialidae, (b) Osmylidae and (c) Sisyridae. From Elliott 2009.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 41 of 68 SECTION 4: CONTINUED

Size is a useful feature in helping to determine which family you have. All start small, of course, but Sialidae grow to over 20mm long (excluding the tail), Osmylidae reaches around 15mm while Sisyridae has a maximum size of around 6mm.

There are few other insects that could be confused with these species. Sialidae may be confused with some Coleoptera, particularly as their pincer-like jaws are reminiscent of Dytiscidae; the segmented gills are, however, diagnostic. The larvae of Gyrinidae (whirligig beetles) have superficially similar gills, but have four small hooks rather than a single long tail. The jaws of Osmylidae look a little like those of the large mayfly Ephemeridae, but in all other respects (lack of tails, no obvious abdominal gills, etc.) they are clearly not mayflies.

Elliott (2009) provides an excellent introduction to these groups, including keys to both larvae and adults, and a key to separate aquatic families from closely related terrestrial families that may fall in from time to time. This key is straightforward to follow; some hints are given here as well to facilitate identification, but Elliott often includes supplementary features to confirm identification, and should therefore be used if you have it available.

Fig. 4.2 Osmylus 1. Sialidae. This family was covered in fulvicephalus. Module 2, Section 5, which has a good From Elliott photo of a couple of the species, and is not (2009). repeated here.

2. Osmylidae. There is only one species, Osmylus fulvicephalus, so identiﬁcation should pose no problem. To recap, Osmylus lacks obvious abdominal gills but has very clear forward-facing piercing jaws that look like slightly curved spears (see ﬁg. 4.2).

3. Sisyridae. There are three species in the UK but the larva of S. dalii has never been found, so we do not know what it looks like. Of the remaining two species, Elliott (2009) provides methods for differentiation at each of the three instars. The later instars are considered here, but if you have a small individual that you suspect or know to be Sisyra, check the deﬁnitive key.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 42 of 68 SECTION 4: CONTINUED

a) Look at abdominal segments 2-6. On the dorsal side of each segment you will see a pair of sclerites, one on each side, with small hairs (setae). Each sclerite has three setae – two long outer ones and a shorter central one. If the central seta points backwards (along with the larger ones), you have Sisyra fuscata (see fig. 4.3a); if it points forwards (the opposite direction to the longer pair), you have S. terminalis. b) To confirm, flip the animal over and look at its abdominal gills. The first pair of gills of S. fuscata have only two segments, with a curious projection on the basal segment of these and all the other gills (see fig 4.3b). In S. terminalis, there is no such projection and the first pair of gills have three segments each.

(a)

(b)

Fig. 4.3 Sisyra fuscata showing (a) abdominal setae and (b) abdominal gills. From Elliott (2009).

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 43 of 68 EXERCISE 6

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 44 of 68 SECTION 5: LEPIDOPTERA

Notes on the identiﬁcation of China-mark larvae. Ian Wallace, World Museum, Liverpool

Preamble

There are ﬁve native species of UK Lepidoptera that have truly aquatic larvae. They are all in the family Pyralidae but all in separate genera. They have the common name of China-mark Moths, because a combination of white wings and dark markings is supposed to resemble decorated china, but only two of the species could be so described. There are plenty of photographs of adults on the Web, e.g. ukmoths.org.uk and in various moth books, (but not of the wingless and underwater female of Acentria ephemerella, for which see Nilsson referred to in the next paragraph, or in an excellent account of the biology of one species by Berg . K. 1941 “Contributions to the biology of the aquatic moth Acentropus niveus (Oliv.)” Vid. Meddr. dansk naturh. Foren Vol. 105 pages 59-139.).

Accepted opinion seems to be that the caterpillars are not difﬁcult to identify and there is not a separate publication to identify them. That view is reasonable for living larvae observed in the wild, but once they are free of their cases and especially if pickled in alcohol, they become much more difﬁcult to identify. A commonly used key is in Nilsson, A. 1996 “Aquatic Insects of North Europe Volume 1” Appollo Books, but I have found this does not identify all larvae easily, particularly when they are small. Many labs will also have Greenhalgh, M. & Ovenden, D. 2007 “Freshwater Life of Britain and Northern Europe” Collins Pocket Guide. This illustrates the full size larvae of all species reasonably well, but only when alive.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 45 of 68 SECTION 5: CONTINUED

In much of England and Wales, all five species are widespread and some species are very common. (They are much scarcer in Scotland with Parapoynx stratiotata apparently absent from there.) They are all found in still and slowly-flowing water where there is abundant submerged, floating and emergent vegetation. All five have been found at some sites, e.g. the Lodes at Wicken Fen. However, they are usually quite scarce in general freshwater samples. There are several reasons. The caterpillars are often firmly fixed to the aquatic plants on which they are feeding, in camouflaged shelters made of pieces of plant held on to the plant by strong silk. (One species spends most of its caterpillar life mining tunnels inside a few species of emergent plant.) As a result they are not easily detached by the net. The silk of these Lepidoptera is much stronger than that of Trichoptera and the caterpillars are much less prone to leaving their shelters on disturbance, in the way many ‘caseless’ caddis do. As a result, even those collected, because pieces of weed on which they are feeding become detached and end up in the sorting tray, may be overlooked.

A further difficulty arises from terrestrial larvae of Lepidoptera, and also sawflies (Hymenoptera) that fall into freshwater. The identification keys do not cater for them. It might be thought that at least when alive the terrestrial species would be obvious as they would show distress in water. This is not necessarily the case, and most china mark moth caterpillars have a hydrophobic covering that makes them look as if they are terrestrial insects that have fallen in. Theoretically any of the 3,300 UK species of Lepidoptera and 500 hundred sawflies could end up in the freshwater sampler’s tray. In reality it is the species that live on vegetation overhanging freshwater that are the most likely to end up as natural casualties, or be knocked off by the surveyor or his net. However, for obvious reasons, only occasionally are terrestrial caterpillars common in samples; an example would be during so-called caterpillar plagues of the Antler Moth Cerapteryx graminis on upland grassland where drifts of expired caterpillars can be found in streams. Nevertheless I was asked to try and deal with them in these guidance notes.

These notes are split into three parts:- - Is my caterpillar of a China-mark Moth?

- An easy key for when the China-mark Moth caterpillar is found in a case of plant pieces or in a shelter stuck to a plant.

- An advanced key for China-mark Moth caterpillars.

Note that most of the photographs are of preserved larvae i.e. how they will appear in a preserved sample awaiting identiﬁcation.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 46 of 68 SECTION 5: CONTINUED

Is my larva possibly a China-mark Moth caterpillar? A ﬁrst glance at the extensive notes below may seem daunting but most of it involves features that are easy to see, and remember it is an attempt to eliminate about 3,800 other possibilities that your caterpillar might be.

1. Does it have pro-legs, commonly called “false legs”, on the underneath of the abdomen, with each pro-leg ending in a group of prominent hooks. (These hooks are often called crochets because they are the same shape as the pointy end of a crochet needle.) The soft “false legs” may be retracted or sucked in, when the hooks may not be prominent, but a bit of ﬁddling with forceps should tell you if that is the case. The hooks vary in shape and arrangement and a few of signiﬁcance are shown below. The possession of these pro-legs and hooks is characteristic for all but a few primitive Lepidopteran families many of which feed internally in leaves and stems. In any case, all China-mark Moth caterpillars have conspicuous pro-legs and hooks.

Ring of hooks

Pro-legs with hooks

(Some other insect orders can have caterpillar-like larvae:- - Sawflies (Hymenoptera) are very common on overhanging and bankside vegetation. They look superficially very similar to Lepidopteran caterpillars. They usually have obvious pro-legs and move in a caterpillar-like way. However there are no strong pro-leg hooks and they may also have more than four pairs of pro-legs whereas Lepidoptera have only up to 4 (with another pair at the end). The eyes are different in that there are several separated ocelli in Lepidoptera but only one in Sawflies.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 47 of 68 SECTION 5: CONTINUED

- Coleoptera of the family Chrysomelidae are common on trees such as Alder and Willows and other bankside vegetation. They have short larvae and any pro-legs lack hooks.

- .Scorpion Flies (Mecoptera) (not illustrated) have 6 proper legs, and pro-legs but no hooks on them; these are ground-dwellers and unlikely to end in a sample.)

Another beetle larva, but with pro- legs, but no terminal hook circles

Beetle larva with no prolegs

Sawfly one ocellus

Lepidoptera several ocelli

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 48 of 68 SECTION 5: CONTINUED

Sawfly more than 4 pairs of mid abdomen pro-legs Sawfly no terminal hooks on pro-legs

2. Having decided it is a Lepidoptera larva then a number of features will discount the majority of vagrant terrestrial species. Not a deﬁnitive list of don’t haves, but covers common ones certainly. China-mark Moth caterpillars do NOT have:

Bunches of Long hairs on the abdomen

Brightly coloured bands on the abdomen

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 49 of 68 SECTION 5: CONTINUED

“looper” caterpillar with only 1 pair of mid abdomen prolegs and a terminal pair

Less than 4 pairs of mid abdomen pro-legs and a terminal pair.

Hairs on the meso and metathorax and abdomen arising from prominent black spots. These have the term pinnaculae (unless larva is really tiny body length under 3mm – instar 1 & 2 of the Small China-mark, Cataclysta lemnata)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 50 of 68 SECTION 5: CONTINUED

Prominent hairs on head and abdomen that Spiny head are about as long as segment is high

This Lime Hawk caterpillar if it fell into the river below would fail on huge size, bands of colour, pointy head, spiny head, protuberance on tail

Mystery body protuberances (except the gills in Parapoynx stratiotata)

3. If your caterpillar matches NONE of the above, then look at the hook arrangement on the pro-legs.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 51 of 68 SECTION 5: CONTINUED

China-mark Moths have what is called a biordinal arrangement which means the hooks are of two contrasting sizes and a complete ellipse or circle and arranged with s one forward facing and one backward facing row on each pro-leg which join, or more or less join to give a circular or ellipsoidal arrangement. BEWARE that a preserved larva is likely to have retracted the ﬂeshy pro-leg as it died so you may apparently have an arrangement of just a single row but careful examination will reveal two rows The two types of China-mark crochet arrangements are:-

Closed up Open

Type 1 - Both rows similar

Open

Closed

Type 2 - Rows dissimilar

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 52 of 68 SECTION 5: CONTINUED

Examples of non-china mark moths

The Swifts (Hepialidae) with several rows of varying sized hooks

So-called “macro moths” and most butterflies have hooks not in an ellipse, usually only half an ellipse a so-called penellipse arrangement.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 53 of 68 SECTION 5: CONTINUED

Case-dwelling terrestrial Lepidoptera and Leaf-miners often have very reduced hook arrangements.

A good proportion of terrestrial caterpillars found in aquatic samples should have been eliminated by now. However, there are quite a few of the Micro- Lepidoptera, that will get through due to having a complete ellipse of hooks of two sizes.

A good lot more can be dumped by looking at the arrangement of setae by the large and prominent spiracle on the side of the prothorax. Most families have three setae in front. Pyralids (including China-marks) are unusual in having only two. Of course there may be three but due to inexperience you only see two, or less (the spiracle and the setae may be very small in some e.g. China-mark Moths caterpillars – no doubt in their case related to getting oxygen through the general skin surface.) My advice is that if you can see three clearly then that is good but if you cannot see three do not assume they have only 2!

pronotum

Pro-thoracic head spiracle

3 setae in front of spiracle 2 setae above leg – (pre-spiracular setae) beware confusion with pre-spiracular setae

Front leg

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 54 of 68 SECTION 5: CONTINUED

Head

Plate with 3 pre-spiracular setae

spiracle

Plate above leg with 2 setae

If your larva is like this it should have already been ‘dumped’ due to the pinnaculae = dark spots at setal bases, but this one does also show very obviously 3 pre-spiracular setae

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 55 of 68 SECTION 5: CONTINUED

Pronotum here

2 pre-spiracular setae Spiracle

Head here

2 setae above leg

a.n. other setae

Front leg

A terrestrial Pyralid with its 2 pre-spiracular setae

Pronotum

(tiny) pre-spiracular seta (tiny) spiracle

Head (large) pre-spiracular seta 2 setae above leg

Brown China-mark (facing the other way – just to keep you on your toes)

That is likely to leave just the family Pyralidae in terms of caterpillars that have been dislodged from bankside vegetation and ended up in a sample. The deﬁnite characters to get down to China-mark Moth (subfamilies Nymphulinae and Acentropinae) are not easy and mainly involve ﬁnding further obscure small setae. It would take a lot of space to deal with this but note that only a few species of Pyralid are likely to be found on bankside vegetation and most should have been previously eliminated by having large black spots, pinnaculae, associated with the setae, or very long hairs, or bright colour patterns.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 56 of 68 SECTION 5: CONTINUED

So my advice is that if you have NOT managed to make your caterpillar into an alternative by this stage that you decide it probably is a China-mark Moth but if after having looked at the descriptions of those species it really does seem odd then put it to one side as an unidentiﬁed lepidopteran.

Only one other group of Pyralids is worth considering in any detail. The Pyralids of the sub-family Schoenobiinae. They live as leaf-miners in emergent plants of Phragmites, Glyceria maxima and Carex and move between plants by cutting out a piece of plant and ﬂoating on it, and might thus end up being confused with, for example the Beautiful China-mark Nymphula stagnata which spends most of its time as a leaf miner, or other species which make cases - Elophila nymphaeata and Cataclysta lemnata. Fortunately Schoenobiinae have a strange lump between their front legs that easily distinguishes them, but I have not obtained material to be able to take identiﬁcation further in a satisfactory way, and the few descriptions of larvae do not cover all three UK species in a comparative way.

“lump”

Instar 2 or 3

“lump”

Presumed final instar

(Figure from :- Hasenfuss, I., 1960, Die larvalsystematik der Zunsler Abhandlung zur larvalsystematik der insekten 5)

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 57 of 68 SECTION 5: CONTINUED

Full-grown China-mark caterpillars may have a “double chin” (arrowed) but it is never in the form of a rounded lump.

Simple key to SOME China-mark Moth caterpillars

1. – Caterpillar with gills

Ringed China-mark Parapoynx stratiotata (Linnaeus, 1758)

Final instar gills

(note the gills are quite unlike the long hairs which clothe many terrestrial species such as illustrated here)

– Caterpillars without gills – 2

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 58 of 68 SECTION 5: CONTINUED

2. – Caterpillar in case made of aquatic plant – 3

– Caterpillar not in a case made of aquatic plant - use more advanced key

3. – Caterpillar in a case that is made entirely of, or incorporates, Duckweed fronds

(any “Lemna” species). Caterpillar with a dark coloured abdomen (and with a contrasting pale head at later instars).

Small China-mark Cataclysta lemnata (Linnaeus, 1758)

– Caterpillar in a case made from a single disc cut from a leaf of ﬂoating plant

e.g. Potamogeton, Water Lily, Hydrocharis, Glyceria, Polygonum and stuck ﬂat on to the same or another leaf. Caterpillar with a pale abdomen.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 59 of 68 SECTION 5: CONTINUED

Brown China-mark Elophila nymphaeata (Linnaeus, 1758)

Catepillar case stuck on leaf

Disc removed from overlying leaf to reveal caterpillar

Feeding damage on Hydrocharis

Leaf pieces removed to make cases

– Caterpillar in a case made of several pieces of plant or stuck on at an angle to the leaf - use more advanced key

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 60 of 68 SECTION 5: CONTINUED

More advanced key to China-mark Moth Caterpillars (a key for larvae of body length 3mm and under is being devised

1. – Caterpillar with gills Ringed China-mark Parapoynx stratiotata (Linnaeus, 1758)

(Note that the gills are quite unlike the long hairs which clothe many terrestrial species. The number of ﬁlaments increases at each moult starting with 1 at instar 2)

see illustrations in Simple Key (above).

(Caterpillar not usually in a case, but in a shelter of silk. However, when it pupates it does so in a case made of two or more pieces of plant.)

– Caterpilllar without gills – 2

2. – Hook arrangement on pro-legs with the anterior and posterior facing rows the same. (They both have two basic sizes of hook, large and small) – 3

rows closed together rows open

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 61 of 68 SECTION 5: CONTINUED

– Hook arrangement on pro-legs with an anterior facing row of very small hooks (of various sizes) and a posterior row having large hooks, and small ones – 4

Not needed for identification, but included for interest P. stratiotata Type 2 but not so marked

3. – The hook rows are long, each about a quarter to a third of the width of the body at that point.

The length of the largest hooks is a tenth or less the length of the whole row.

The hooks in each row get smaller to each end, and they do not join, i.e. there are two crescents rather than a complete ellipse.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 62 of 68 SECTION 5: CONTINUED

Brown China-mark Elophila nymphaeata (Linnaeus, 1758)

(Caterpillar in a case made from a single disc cut from a leaf of ﬂoating plant and stuck ﬂat on to the same or another leaf of the plant. Abdomen pale, but head and pronotum pattern very variable.) Pronotum does not have a lateral lobe. The pro-leg hook rows are not surrounded by a clear ring.)

Final instar

Instars ? 2 and 3

Another view of the final instar above

– The hook rows are short, about a sixth to a ﬁfth the width of the body at that point.

The length of the largest hook is around a sixth of the length of the whole row.

The rows join so that there is a complete ellipse.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 63 of 68 SECTION 5: CONTINUED

Small China-mark Moth Cataclysta lemnata (Linnaeus, 1758)

(Caterpillar in a case that is made entirely of, or incorporates, Duckweed fronds. They may cut a disc from another plant then attach a tube made from duckweed fronds under it and roam among their food-plant so equipped. They can cut a section of a grass stem and live in it like a caddis larva. Larger caterpillars have a dark coloured abdomen and pronotum and a contrasting pale head. Younger ones may have head, pronotum and body all dark. There is a prominent lobe at the side of the pronotum. The pro-leg hook rows are surrounded by a clear ring)

Instar ? 3 Instar 1

Instar ? 3

Pronotum lateral “lobe” Final instar

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 64 of 68 SECTION 5: CONTINUED

4. – The middle long hair on the pronotum arises from the posterior half of the plate. The hair can be very pale and its origin difﬁcult to see in dorsal view, but in side view it can be seen in proﬁle. Beware that the pronotum can be so pale that the posterior edge cannot be determined easily, and may also be overhung by the mesothorax.

Beautiful China-mark Nymphula stagnata (Donovan, 1806).

(Caterpillar only likely to be found if a sample has involved Bur-reed (Sparganium) species or Yellow Water Lily (Nuphar), but note that Unbranched Bur-reed (S, emersum) can be a bit non-descript until it develops ﬂower stems, and in Europe other emergent plants are noted as hosts. For most of its life the larva lives inside tunnels it has mined in the plants. It is therefore only likely to be recorded from about April to July, and then as a larger larva. Size is useful in distinguishing it from A. ephemerella so any larva larger than 1 cm body length and with a head width more than 1mm is likely to be this species. At the later instars, the ones most likely to be encountered, it can have a pronotum without any patches of pigment, (but with muscle attachment spots). Case made of two or more pieces of plant.)

Posterior edge of pronotum

Green arrow is the seta to look out for. Black arrows are the three front edge setae not to confuse middle arrow with.

Recessed posterior edge of pronotum

In this example of N. stagnata the pronotal plate is resting at the posterior part of the prothorax, and it is overhung by the mesothorax putting the posterior large (green) seta apparently right at the back of the segment.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 65 of 68 SECTION 5: CONTINUED

– The middle long hair on the pronotum arises from the anterior half of the plate. The hair can be very pale and its origin difﬁcult to see in dorsal view, but in side view it can be seen in proﬁle. The pronotum usually has enough pigment to enable the posterior margin to be seen, but it can be obscured by an overhanging mesothorax.

The Water Veneer Acentria ephemerella (Denis & Schiffermuller, 1775).

(Caterpillar feeds on a wide range of filamentous and small-leaved submerged plants – and is reported as also feeding on filamentous algae. It lives in a silken shelter closely fixed to the stems or leaves of its food pant and can be difficult to dislodge. Larvae can be found through-out the year. It is the smallest of the species and the maximum size reported is a body length of 1cm and head width of just over 1mm. This species does not make a transportable case, but its shelters, incorporate pieces of food-plant. There is usually some pigmentation, as well as muscle attachment spots, on the pronotum – but beware confusion with early instars, 2 & 3, of N. stagnata which also match that description.)

Pronotum posterior edge, overhung by mesonotum

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 66 of 68 SECTION 5: CONTINUED

Other ways of viewing the main distinguishing character

(Figures (modiﬁed) from Hasenfuss, I., 1960, Die larvalsystematik der Zunsler Abhandlung zur larvalsystematik der insekten 5)

N. stagnata A. ephemerella

(an additional way of considering the character is that the distance between the two front setae is about the same as the distance between them and both posterior large seta in A. ephemerella i.e. the three make an equilateral triangle; N. stagnata has a different arrangement.)

Warning Several other species have been recorded establishing themselves in aquatic plant nurseries having been imported from abroad. At present none of these have become established in the wild and most are tropical or sub-tropical. However some were found outdoors in nursery tanks, and there are several species of China-mark that have spread around the world, so it may only be a matter of time before they become an established part of the UK fauna. The late 1970s and 1980s seemed to be the heyday of these imports and they are now only occasional. However be alert for the possibility of a non-native species if a sample has been taken near an aquatic nursery or from a site known to have been stocked with nursery-grown plants. So if your China-mark caterpillar looks really weird in those circumstances….. Goater, B. 1986 British Pyralid Moths published by Harley Books discusses these non-natives.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 67 of 68 EXERCISE

Draw or photograph the pro-leg hooks of a China-mark caterpillar and then identify it to species using other characters.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace) Page 68 of 68

Acknowledgements

Terry Gledhill is extremely grateful to his colleagues Dr Melanie Fletcher and Simon Pawley for all their hard work, expertise and enthusiasm in putting together this module. Thanks also to the Council of the Freshwater Biological Association for continued support.

Module 9: Version 2, December 2010 (Terry Gledhill and Ian Wallace)