Piscicola siddalli

source: researchgate

ABSTRACT: A new species of fish leech from England, Piscicola siddalli n. sp. (Piscicolidae), was collected in 2006 on

stones and on grayling (Thymmallus thymmallus L.) in the River Ure, North Yorkshire, Great Britain. The leech is 4(12)

annulate; gonopores are separated by four annuli. The male gonopore is much larger than the female gonopore. Seminal

receptacle consists of a round aperture, located at a distance of 3 annuli behind the female gonopore. Copulatory area on the

clitellum is in the form of a circle. Vector tissue has the form of a circular plate, below the oviduct opening.

KEY WORDS: taxonomy, United Kingdom, Clitellata, Hirudinida, Hirudinea, Piscicolidae, Piscicola siddalli n. sp.

Classification of the fish leech family Piscicolidae

Johnston, 1865 was originally based on coelomic

structure and associated respiratory organs and the

family was comprised of 3 subfamilies: Platybdellinae

Epshtein, 1970; Pontobdellinae Llewellyn, 1966; and

Piscicolinae Caballero, 1956 (Sawyer, 1986; Burreson

and Dybdahl, 1989). Epshtein (1983, unpublished

dissertation, University of Leningrad, USSR) and

Epshtein et al. (1994) divided the subfamilies into 20

tribes and 54 genera on the basis of variation in the

reproductive system. Recent molecular analyses have

questioned this classification and suggest that the

subfamilies Piscicolinae and Platybdellinae are not

monophyletic and that the Pontobdellinae is paraphyletic,

or possibly polyphyletic (Utevsky and Trontelj, 2004;

Williams and Burreson, 2006; Utevsky et al., 2007). To

date, the family contains 40 Palearctic freshwater species,

belonging to 10 genera (Sket and Trontelj, 2008).

In 2006, we collected a previously unknown leech

species from the River Ure in North Yorkshire, Great

Britain. The leeches collected belong to the Holarctic

genus Piscicola, but they are taxonomically distinct

from known species (for extensive character descrip-

tions, see Johansson, 1896; Selensky, 1907; Male´cha,

1979, unpublished thesis, Universite´ des Sciences et

Techniques de Lille; Villeneuve d’Ascq, France;

Sawyer, 1986; Epstein, 1987; Bielecki, 1997). Here,

we describe the new species and use mathematical

modelling to describe the body form of leeches as a

significant ectosomatic character that shows the limits

of space, within which topographical change of

internal organs occur (Bielecki, 1993, 1994, 1997;

Bielecki and Epshtein, 1994, 1995).

MATERIALS AND METHODS

Eleven leeches were collected 26 July 2006 from the

underside of stones in shallow, still water, approximately 2 m

from a rapid, in the River Ure, North Yorkshire, Great

Britain (54u17953.50N; 01u5398.80W). Blood was present in

the alimentary tract of some leeches. Loach, Noemacheilus

barbatulus (L.), was noted between stones, and brown trout,

Salmo trutta m. fario L.; grayling, Thymallus thymallus L.;

and chub, Leuciscus cephalus L., were common in the river.

In October 2006, 1 additional leech was collected from a

grayling in the same area.

The holotype and paratype were preserved in ethanol. The

holotype (MIZ 225896) and paratypes (MIZ 225897, MIZ

225898) of Piscicola siddalli n. sp. were deposited at the

Institute of Zoology of the Polish Academy of Sciences in

Warsaw, Poland. Additional specimens were deposited in

the Museum of Natural History, Warmin

´sko-Mazurski

University in Olsztyn, Poland, and retained in our collection.

Construction, description, and application of

the model

Based on the parameters of the body form model in

leeches proposed by Epshtein (1989, unpublished disserta-

tion, University of Leningrad, USSR), a modified and

supplemented computer model (Figs. 1–3) was constructed

(Bielecki, 1993, 1994, 1997, 2001; Bielecki and Epshtein,

1994, 1995). The model presents the leech body on a plane

as 2 ellipses (suckers) and 6 trapeziums (anterior body part,

trachelosome, 2 trapeziums; posterior body part, urosome, 4

trapeziums) situated between the ellipses (Figs. 1–3).

Transverse sections through the trachelosome and urosome
are considered as 2 ellipses (Figs. 2, 3). Abundant materia

Figures 1–3. Diagrammatic model of the leech body. 1.

General leech body. 2. Transverse section of trachelosome.
3. Transverse section of urosome.
provides evidence that the model permits a sufficiently exact

description of the body form of various leech species.

The computer model was constructed according using the

following 29 parameters.

(1–4) Parameters describing the form of the anterior sucker:

C

1

, horizontal diameter; C

1

1

, vertical diameter; R

1

, length of

anterior part of sucker; M

1

, length of posterior part of sucker.

(5–12) Parameters describing the form of the trachelo-

some: d

1

, width at sucker junction; d

2

, width at outline

narrowing; d

3

, width at border with urosome; D

1

, largest

width of trachelosome; N

1

, largest height of trachelosome;

S

1

, height of first trapezium; S

2

, height of second trapezium;

L

1

5(S

1

+S

2

), length of trachelosome.

(13–25) Parameters describing the form of the urosome:

width at places of outline distortion (bases of consecutive

trapeziums); d

4

, base of first trapezium; d

5

, base of second

trapezium; d

6

, base of third trapezium; d

7

, base of fourth

trapezium (width at sucker junction); D

2

, largest width of

urosome; N

2

, largest height of urosome; L

2

,(S

3

+S

4

+S

5

S

6

), urosome length (height of consecutive trapeziums); S

3

,

height of first trapezium; S

4

, height of second trapezium; S

5

,

height of third trapezium; S

6

, height of fourth trapezium; K

1

,

distance from d

3

to D

2

;K

2

, distance from D

2

to d

7

.

(26–29) Parameters describing the form of posterior sucker:

C

1

2

, horizontal diameter; C

2

, vertical diameter; M

2

, length of

anterior part of sucker; R

2

, length of posterior part of sucker.

Body shape and size are presented in the plate (Figs. 4–7)

and in Tables 1 and 2. The 19 body proportion indices

(invariants) are as follows:

(1) Index describing L/D

2
, relative body lengthFigures 4–7.
Diagrammatic comparison of Piscicola

siddalli n. sp. and Piscicola respirans.4. Piscicola siddalli,

general body form. 5. Piscicola siddalli, relative transverse

sections of trachelosome and urosome. 6. Piscicola

respirans, general body form. 7. Piscicola respirans,
relative transverse sections of trachelosome and urosome.
Indices describing anterior sucker: (2) C

1

1

/d

1

, ratio of

horizontal diameter of sucker to trachelosome width at

sucker junction; (3) C

1

1

/D

1

, ratio of horizontal diameter of

sucker to greatest width of trachelosome; (4) R

1

/M

1

, ratio of

dorsal part of sucker to its ventral part; (5) C

1

1

/C

1

, ratio of

horizontal diameter of sucker to its vertical diameter.

Indices describing trachelosome: (6) L

1

/D

1

, ratio of

trachelosome length to its greatest width; (7) D

1

/N

1

, ratio of

greatest trachelosome width to its greatest height; (8) S

1

/S

2

,

index describing position of greatest width of trachelosome.

Indices describing urosome: (9) L

2

/D

2

, ratio of urosome

length to its greatest breadth; (10) D

2

/N

2

, ratio of greatest

urosome width to its greatest height; (11) K

1

/K

2

, ratio

describing position of greatest width of urosome.

Indices describing posterior sucker: (12) C

1

2

/d

7

, ratio of

horizontal diameter of sucker to urosome width at sucker

junction; (13) C

1

2

/D

2

, ratio of horizontal diameter of sucker

to greatest body height; (14) R

2

/M

2

, ratio of dorsal part of

sucker to its ventral part; (15) C

1

2

/C

2

, ratio of horizontal

diameter of sucker to its vertical diameter.

Indices describing relations between urosome and trache-

losome: (16) L

2

/L

1

, ratio of urosome length to trachelosome

BIELECKI ET AL.—PISCICOLA SIDDALLI N. SP. 221

Table 2. Mean value of 19 body proportion indices in 21 species of Piscicolinae.

Species

Body proportion indices

L/D

2

C

1

1

/d

1

C

1

1

/D

1

R

1

/M

1

C

1

1

/C

1

L

1

/D

1

D

1

/N

1

S

1

/S

2

L

2

/D

2

D

2

/N

2

K

1

/K

2

C

1

2

/d

7

C

1

2

/D

2

R

2

/M

2

C

1

2

/C

2

L

2

/L

1

D

2

/D

1

N

2

/N

1

C

1

2

/C

1

1

Cy. mammillatus 3.0 1.6 0.9 2.0 1.0 1.0 2.3 2.0 2.4 4.0 0.3 5.2 1.6 1.0 1.0 4.3 1.8 1.0 3.3

A. volgensis 4.2 1.6 0.9 4.0 1.0 2.1 1.3 0.9 3.2 1.0 1.0 1.2 0.6 2.0 1.0 3.3 2.1 1.9 1.5

Ca. fadejewi 7.4 1.5 1.2 4.0 1.0 3.0 1.0 0.9 5.5 1.1 1.2 1.3 1.0 1.7 0.9 2.9 1.6 1.4 1.3

I. epshteini 3.4 1.3 0.8 5.0 1.1 1.3 1.7 1.3 2.6 1.0 1.1 0.9 0.7 1.7 0.9 2.9 1.5 2.6 1.2

I. ciosi 4.0 1.6 0.9 5.0 1.0 2.3 1.5 1.0 3.1 1.0 1.9 1.5 0.5 1.6 1.0 3.1 2.3 2.5 1.4

P. geometra 13.0 2.4 1.5 2.7 1.0 3.7 1.1 0.7 10.0 1.2 0.5 2.2 1.8 2.2 1.0 2.7 1.4 1.3 1.7

P. respirans 4.4 1.6 0.9 3.0 0.8 1.5 2.4 1.9 3.4 2.8 0.9 1.9 1.0 1.6 1.0 3.7 1.7 1.4 1.7

P. siddalli n. sp. 5.8 1.6 0.8 4.0 1.0 1.7 2.3 1.2 4.3 2.6 0.6 1.7 0.9 2.5 0.9 2.7 1.3 1.2 1.4

P. fasciata 5.0 2.1 1.3 5.0 1.0 3.2 1.7 1.2 3.7 3.0 2.7 2.9 1.5 2.5 1.0 2.7 1.6 1.0 2.0

P. pojmanskae 6.7 1.1 0.7 2.7 0.8 2.1 1.1 2.2 5.3 1.0 1.8 1.4 1.0 2.2 0.9 4.0 1.6 1.6 2.5

P. annae 9.6 2.4 1.4 5.7 1.0 5.3 1.0 0.9 7.3 1.2 1.2 1.7 1.0 1.3 1.0 3.2 2.3 1.9 1.6

P. borowieci 23.0 2.0 1.3 3.0 1.0 6.0 1.2 1.1 17.6 1.0 0.3 2.1 2.1 2.0 1.0 3.4 1.2 1.4 1.9

P. pomorskii 5.6 2.3 1.6 3.3 1.0 3.1 1.7 0.9 4.3 3.1 0.8 1.6 0.8 2.6 0.9 3.5 2.5 1.3 1.2

P. witkowskii 6.5 1.8 1.0 3.0 1.0 2.2 1.1 1.5 5.2 1.2 2.9 1.3 1.0 1.0 1.0 3.9 1.7 1.6 1.7

P. kusznierzi 6.6 2.0 1.5 3.5 1.2 3.2 1.6 1.2 5.0 2.7 2.1 1.6 1.1 2.7 1.1 3.1 2.0 1.2 1.5

P. wiktori 15.0 1.0 0.8 5.0 0.6 6.2 1.7 0.9 11.7 2.5 0.9 1.1 0.9 3.5 0.8 3.8 2.0 1.3 2.3

P. niewiadomskae 6.1 2.2 1.3 4.0 1.1 3.1 1.3 0.9 4.8 0.9 0.9 1.3 0.8 2.0 1.1 3.5 2.3 2.9 1.4

P. elishebae 5.2 2.0 1.2 3.3 1.0 2.5 1.3 1.0 3.9 1.3 0.3 1.4 1.1 2.0 1.0 2.8 1.8 1.9 1.8

P. margaritae 6.5 1.3 0.8 4.0 0.8 2.4 1.4 0.9 5.5 2.5 0.3 1.4 0.7 1.3 0.8 5.3 2.3 1.3 1.9

P. jarai 11.0 1.3 0.8 6.0 1.0 3.1 2.5 1.8 8.5 2.6 0.3 1.7 1.5 1.3 1.0 3.6 1.3 1.3 2.4

Pa. stenosa 19.6 1.7 1.2 4.0 1.2 6.3 2.0 1.2 14.1 1.4 3.3 1.3 1.4 1.7 1.0 2.6 1.2 1.7 1.4

P. brylinskae 7.0 1.5 0.7 4.0 1.5 2.7 2.7 1.0 5.4 2.8 0.2 1.6 0.9 2.7 1.3 3.5 1.7 1.7 2.2

L/D

2

– relative body length, C

1

1

/d

1

– ratio of horizontal diameter of sucker to trachelosome width atsucker junction, C

1

1

/D

1

– ratio of horizontal diameter of sucker to greatest width of trachelosome,R

1

/M

1

– ratio of dorsal

part of sucker to its ventral part, C

1

1

/C

1

– ratio of horizontal diameter of sucker to its vertical diameter, L

1

/D

1

– ratio of trachelosome length to its greatest width, D

1

/N

1

– ratio of greatest trachelosome width to its greatest

height, S

1

/S

2

– index describing position of greatest width of trachelosome, L

2

/D

2

– ratio of urosome length to its greatest breadth, D

2

/N

2

– ratio of greatest urosome width to its greatest height, K

1

/K

2

– ratio describing

position of greatest width of urosome, C

1

2

/d

7

– ratio of horizontal diameter of sucker to urosome width at sucker junction, C

1

2

/D

2

– ratio of horizontal diameter of sucker to greatest body height, R

2

/M

2

– ratio of dorsal part of

sucker to its ventral part, C

1

2

/C

2

– ratio of horizontal diameter of sucker to its vertical diameter, L

2

/L

1

5ratio of urosome length to trachelosome length, D

2

/D

1

– ratio of greatest width of urosome to greatest width of

trachelosome, N

2

/N

1

– ratio of greatest height of urosome to greatest height of trachelosome, C

1

2

/C

1

1

– ratio of horizontal diameter of posterior sucker to horizontal diameter of anterior sucker.

222 COMPARATIVE PARASITOLOGY, 79(2), JULY 2012

level of the first pair of pulsatile vesicles; 6 or fewer

pairs of testisacs (usually 5). Seminal vesicles located

anterior to the first pair of testisacs or at the level of

testisacs 1 or 2; straight rods or ampullae, or single

and multiple loops. Vasa deferentia straight, slightly

or strongly coiled. Ejaculatory ducts variously located

relative to ganglia: from half distance between

ganglia 3 and 4, to ganglia 5; they can be sharply

or gently bent once, parallel or transverse to the body

long axis, or multiply bent. Prostatic glands on atrium

very large, well developed or poorly developed,

rarely vestigial. Ovisacs short, reaching first pair of

testisacs, or long, reaching second pair of testisacs,

located between testisacs or on them, of varied shape:

coiled in many planes, cylindrical; posterior ends free

or intertwined. Oviducts merge into female gonopore

anterior to vector tissue, much remote from conduct-

ing strands, running separately. Vector tissue as a

plate located posterior to the oviduct opening, of

varied shape: ellipse parallel or transverse to the body

long axis, circular or triangular. Conducting strands

very long, long or short, narrow or wide, may connect

the ovisac with anterior, mid or posterior part of

vector tissue.

Description

Body shape and size: Length, 7.5–13.1 mm; width,

0.9–2.15 mm. L/D

2

, 5.8; C

1

1

/d

1

, 1.6; C

1

1

/D

1

, 0.8;

R

1

/M

1

, 4.0; C

1

1

/C

1

, 1.0; L

1

/D

1

, 1.7; D

1

/N

1

, 2.3; S

1

/

S

2

, 1.2; L

2

/D

2

, 4.3; D

2

/N

2

, 2.6; K

1

/K

2

, 0.6; C

1

2

/d

7

,

1.7; C

1

2

/D

2

, 0.9; R

2

/M

2

, 2.5; C

1

2

/C

2

, 0.9; L

2

/L

1

, 2.7;

D

2

/D

1

, 1.3; N

2

/N

1

, 1.2; C

1

2

/C

1

1

, 1.4 (Figs. 4, 5;

Table 2).

Body form: Division into trachelosome and urosome

visible, especially in specimens full of blood

(Figs. 11, 13, 15–18; Table 1). Body short, rather

cylindrical. Anterior and posterior suckers round,

connected strongly eccentrically (Fig. 19).

Body size and shape depends, to a large extent, on

the amount of blood in the alimentary tract. Two

specimens had a different body form and weight

because their alimentary tract was filled with blood.

(L/D

2

, 9.55; weight, 44 mg; and L/D

2

, 10.30; weight,

48 mg; Figs. 11, 13; Table 1). In further analysis of

the material, we adopted the average size for all 12

specimens (Tables 1, 2).

Pulsatile vesicles white (11 pairs), not large, but

well visible (Fig. 15).

Posterior sucker with 14 each narrow white and

broader brown radial bands (Fig. 20); with 10 spots

resembling eyes, situated at the edge of the dark

radial bands (Figs. 15, 17, 18).

Anterior sucker with large, symmetric, white spots,

with irregular edges; with 2 pairs of eyes. The first

pair, which is the larger of the 2, situated in the lower

part of the white spots (Figs. 15, 19).

A full mid-body somite consists of 4 annuli

secondarily divided into 12 subannuli (Fig. 8).

However, further rows are visible on these 4 annuli.

The first annulus, is the broadest and is 4 sections.

The second annulus, with pulsatile vesicles, is also

divided into 4 sections, whereas the third and fourth

annuli are each divided into 2 sections. Thus, a

somite is composed of 12 rings. This unique somite

has not been reported in Palearctic species of

Piscicola but has been reported in the leech

precursors Acanthobdellidae (Acanthobdella peledina

Grube, 1851 and Paracanthobdella livanowi Epstein,

1966), although in these species the annuli are further

divided by secondary furrows on subannuli (Epstein,

1987).

Body coloration: The coloration is quite characteris-

tic in this species and results from the mixture of

white and brown melanophores. Even preserved

specimens retain pigmentation, facilitating discrimi-

nation of this species from other Palearctic species of

Pisciola.

Dorsal pigmentation more visible than ventral

pigmentation; white melanophores create a charac-

teristic and common pattern on the brown back-

ground. This background is either very bright or dark

brown. In some specimens, the brown melanophores

are in the form of patches, whereas the background

consists of brown dots or patches. This pattern is

present also on the ventral side, but it is less visible.

The trachelosome is the darkest. The urosome, due to

transparency and shining of the alimentary tract, is

slightly brighter.

The white melanophores on the trachelosome form

4 or 5 spots in the central part of the body; the fourth

or fifth spot is the largest, occurring on 1.5–2 annuli

and joining the large white spots that are present on

Figure 8. Diagrammatic interpretation of Piscicola

siddalli mid-body somite consisting of 4 annuli (S1–S4)

secondary divided on 12 annuli (dashed lines).

BIELECKI ET AL.—PISCICOLA SIDDALLI N. SP. 223

Figures 9–10. Dendrograms of 21 species of Pisciolinae. 9. Dendrogram based on mean value of 19 body proportion

indices (Ward’s method, Manhattan distance). 10. Dendrogram based on 113 characters (Ward’s method,
Manhattan distance)

the sides of the body, extending to the ventral surface

and forming a band around trachelosome. On the left

and right sides of the white spots, at the same level,

there are 4 or 5 white paramedial spots. On the sides

of the body, there are also 4 or 5 white spots.

The white spots on the urosome retain a similar

pattern. There are 14 medial spots, but the last medial

spot is present on the dorsal side of the posterior

sucker. On the left and right sides of the median plane

there are 2 rows of 13 of smaller white paramedial

spots. On each side of the body, as in the

trachelosome, there are 13 white spots. Within 11

of the largest white spots there are pulsative vesicles

(Figs. 15–19, 21).

On some of the somites between the white

paramedial and big lateral spots there are additional

external paramedial white spots, and there are internal

paramedial white spots on the left and right sides of

the medial spots.

All white spots, apart from the 13 lateral spots, i.e.,

the medial, internal paramedial, and external para-

medial, consist of 2 or 3 parts. In some specimens, the

white spots may disappear partly or completely.

The pigmentation of the ventral surface is more

consistent and the white external paramedial spots are

often clearly visible.

The pigmentation of the 2 specimens with full

alimentary tracts was quite different from that

described above; in these specimens, the spots are

less visible and brighter (Figs. 11, 13).

The pigmentation of P. siddalli n. sp. is superfi-

cially similar to that of Italobdella ciosi Bielecki,

1993 and Hemiclepsis marginata (O. F. Mu¨ller,

1774). However, I. ciosi undoubtedly belongs to a

different genus, whereas H. marginata belongs to a

different family (Bielecki 1993, 1994, 1995, 1997,

2001; Bielecki and Cios, 1998).

Alimentary tract: Mouthpore located in the center of

the anterior sucker. Proboscis between the first and

third nerve ganglia (Fig. 23). Visible salivary glands

present on either side of the proboscis; esophageal

gland (a pair of pockets) opens to the esophagus.

Crop composed of 7 pair of ceca (Fig. 23). Below

the seventh ceca, a thin-walled cecum is situated

ventrally; cecum composed of two pair of 5 sacs.

Intestine proper, large and well developed; with 5

paired branches; the first 3 pairs are well developed

and directed laterally and anterad; fourth pair is

slightly smaller, with branches displaced to the axial

plane; fifth pair small and poorly visible (Fig. 24).

Posterad to the fifth pair of branches, intestine forms

a twisted tube which further passes into the rectum.

Anus visible, open, situated on the white field in the

middle of the dorsum, 2 rings anterad to the posterior

sucker. Arrangement of alimentary tract (crop and

posterior crop cecum) resembles that of I. ciosi and

Piscicola fasciata Kollar, 1842.

Reproductive system: Male and female gonopores

separated by 4 annuli. Male gonopore large; female

gonopore small. Seminal receptacle situated 3 annuli

behind female gonopore (F). Copulatory area (CA)

occupies the first 4 annuli of urosome and consists of

a loop (Fig. 22). Six pairs of testisacs situated

between segments from XIII/XIV to XVIII/XIX;

vasa efferentia depart and join the longitudinal vasa

deferentia. The latter pass anterad into seminal

vesicles (VS) anterior to the first pair of testisacs

(T

1

), forming ejaculatory ducts (ED) in the form of

thick semiloops, not reaching the fifth neural

ganglion, and unite with the common part of atrium.

Atrium (A) lacking any process; prostate glands

on atrium present (Fig. 26). Ovisacs cylindrical,

consisting of 2 parts; posterior ends touching first pair

of testisacs (Figs. 25–27). Oviducts open near female

gonopore anterior to the vector tissue. Vector tissue

large and circular. Conducting strands of vector tissue

are wide but short, joining each ovisac with vector

tissue (VT); vector tissue and conducting strands of

vector tissue are easily visible after putting aside the

ovisacs (Fig. 25–27). The CA consists of a loop. This

character was known only in the species P. fasciata.

Conducting strands of vector tissue in P. siddalli n.

sp. resemble the strands in P. fasciata only in respect

of length (i.e., they are short). They clearly differ as

regards their width (in P. siddalli n. sp., they are

much broader).

Biology: After capture the leeches were put into a jar.

When they settled on the walls their reaction to light

was checked. After passing a hand between the jar and

the sun, only a few specimens reacted weakly to this

movement by slightly raising their body. This reaction,

together with the fact that they were present only under

stones, may indicate a certain preference for sites with

low light. However, most of the specimens were

collected after feeding, so their location under stones

could be predator avoidance behavior. Leeches in the

jar could have reacted weakly to light also because

they were in a poor physiological condition. No

specimens were collected in fast moving water.

Taxonomic summary

Type host: Grayling, Thymallus thymallus.

Type locality and collection date: River Ure, in the

vicinity of Lords Bridge, England, 54u17953.50N;

01u5398.80W, 26 July 2006, by Stanisław Cios and

Stuart Crofts.

Specimens deposited: The holotype (Figs. 15, 16, 19,

21–26) and paratypes (Figs. 11, 13, 27) were

deposited in the Museum of the Institute of Zoology

of the Polish Academy of Sciences in Warsaw, Coll.

MIZ 225897 and MIZ 225898, respectively.

Etymology: The specific epithet is an honorific

honoring Dr. Mark Siddall, Curator in the Division of

Invertebrate Zoology at the American Museum of

Natural History in New York. He has greatly

contributed to our knowledge of the biology and

phylogenetics of the Hirudinida.

Remarks

Considering morphotypes of all the analysed

species and also of other genera, P. siddalli n. sp.

body form is most similar to Piscicola respirans

Troschel, 1850 (Figs. 6, 7, 9, 12, 14). Very similar,

almost identical, characteristics are as follows: C

1

1

/d

1

,

C

1

1

/D

1

,C

1

1

/C

1

,L

1

/D

1

,D

1

/N

1

,D

2

/N

2

,C

1

2

/d

7

,C

1

2

/C

2

,

and N

2

/N

1

.Piscicola siddalli n. sp. differs from

P. respirans in the following characteristics: L/D

2

,

R

1

/M

1

,S

1

/S

2

,L

2

/D

2

,K

1

/K

2

,R

2

/M

2

,L

2

/L

1

,D

2

/D

1

, and

C

1

2

/C

1

1

.

The tree diagrams presented in Figures 9 and 10

shows P. siddalli n. sp. placed in a large group of

species in the genus Piscicola, however, excluding

Piscicola geometra (L.)—the only species known to

occur in Great Britain. Species with similar body

forms, P. siddalli n. sp. and P. respirans, cluster with