Table 5 Comparative data for morphological characters among the selected cryptogonimid genera based on [44] and this study

Body shape

Irregular oval

Elongate, fusiform

Long, relatively narrow

Elongate-oval to distinctly elongate

Fusiform

Elongate with distinct constriction immediately posterior to oral sucker

Elongate-oval

Very elongate

Oval, enlongate-oval

BL/BW

1.5–2.5

4–7

c.11

2–3.5

2–2.5

c.6

c.3

11–16

2–3.5

OS

Almost round, opens subterminally

Infindibular or cup-shaped, massive, relatively large, longer than wide, squared-off posteriorly, opens terminally

Massive, broadly infundibular, opens terminally

Funnel-shaped, opens terminally

Nearly round, opens terminally

Funnel- or cup-shaped, opens almost terminally

Almost round, opens subterminally

Longer than wide, opens subterminally

Nearly round, opens almost terminally

Circumoral spines

Absent

Absent

Absent

Enlarged (rarely absent)

Enlarged

Absent

Absent

Absent

Absent

VS

Pre-equatorial, rounded, unspecialised, not obviously embedded in ventrogenital sac

Pre-equatorial, rounded, unspecialised, embedded in ventrogenital sac

Pre-equatorial, rounded, much smaller than oral sucker.

Pre-equatorial, rounded, unspecialised, not obviously embedded in ventrogenital sac

Pre-equatorial, rounded, unspecialised, embedded in ventrogenital sac

Pre-equatorial, rounded unspecialised, deeply embedded in ventrogenital sac

Pre-equatorial, rounded, unspecialised, not obviously embedded in ventrogenital sac

Pre-equatorial, rounded, unspecialised, not obviously embedded in ventrogenital sac

Pre-equatorial, rounded unspecialised, embedded in ventrogenital sac, usually smaller than VS

OSW/VSW

1.5–2.1

0.8–1.7

c.2.7

1–2.5

1.5–2.5

c.2.5

2.0–2.5

c.2.0

1–2.5

Tegument

Smooth or spined, spines reach to posterior extremity, largest in mid-region

Spined, spines can reach at about level of ovary

Spines not observed

Smooth or spined, spines reach to posterior extremity

Spined, spines reach to posterior extremity

Spines not observed

Spines not observed

Spines not observed

Spined

Forebody

26–40% of BL

30–62% of BL

c.24 % of BL

5–40% of BL

20–25% of BL

c.40% of BL

c.20% of BL

20–25% of BL

20–33% of BL

Prepharynx

Short or absent

Variable in length

Broadly oval, larger than ventral sucker

Short

Very short

Very short

Very short

Short

Short

Oesophagus

Short or indistinct

Shorter than prepharynx

Absent

Short

Very short

Short

Very short

Long

Short

Intestinal bifurcation

In about mid-forebody, at level of ventral sucker

In posterior forebody just anterior to VS

In posterior forebody

Immediately anterior to VS

Immediately anterior to or dorsal to VS

In anterior forebody

In mid-forebody

In posterior forebody

In mid-forebody

Caeca

Blind, end at level of testes or post-testicular region

Blind, reach into post-testicular region

Blind, reach into post-testicular region

Opens via separate ani close to posterior extremity

Blind, end close to posterior extremity

Blind, end posteriorly to testes

Blind, end close to posterior extremity

Blind, end close to posterior extremity

Blind, end close to posterior extremity

Testes

2, symmetrical or oblique, lobed, contiguous or slightly separated

2, entire, tandem, contiguous, in posterior third of hindbody; anterior testis oval, posterior testis sub-triangular

9, transversely oval, entire, in tandem row, contiguous, in posterior third of hindbody

2, entire, tandem, contiguous, in posterior third of hindbody

2, symmetrical to slightly oblique, close to posterior extremity

2, strongly oblique to tandem, in mid-hindbody

9, irregular, in posterior hindbody

2, mostly intercaecal, distinctly elongate, strongly oblique to slightly tandem

Usually 9, in two lateral groups, or one large group in hindbody

Seminal vesicle

Elongate-oval, naked

Tubulo-saccular, naked, long, convoluted

Naked, long, convoluted

Tubular

Tubulo-saccular

Tubulo-saccular, in forebody

Tubular

Tubular

Tubulo-saccular

Gonotyl

Absent

Absent

Absent

Absent

A spined muscular structure immediately anterior to VS

Absent

Absent

Absent

Absent

Genital pore

Median, immediately anterior to VS

Median, immediately anterior to VS

Median, immediately anterior to VS

Median, immediately anterior to VS

Median, immediately anterior to VS

Median, at mid-level of intestinal bifurcation and VS

Sinistral to VS

Median, immediately posterior to VS

Median, posterior and slightly sininstral to VS

Ovary

Dextral, pretesticular, regularly lobed

Oval, pre-testicular, overlapping anterior testis

Irregularly subtriangular, pre-testicular

Entire, pre-testicular; in posterior hindbody

Entire, anterior to testes in posterior hindbody

Entire, immediately anterosinistral to anterior testis

Deeply lobed, median, immediately anterior to testes

Deeply lobed, well separated form anterior testis, occupies full width of body in mid-hindbody

Deeply lobed, immediately anterior to testes

Uterus

Fills much of body from intestinal bifurcation to anterior testicular region, mostly intercaecal

Fills much of hindbody from anterior testis anteriorly, passes dorsally to VS, mostly intercaecal

Narrow, reaches between VS and anterior testis, passes dorsally to VS, mostly intercaecal

In hindbody between ovary and VS

In hindbody between ovary and VS

In hindbody, extends close to posterior extremity

In hindbody, between gonads and VS

In hindbody, between VS and anterior testis

In hindbody, extends close to posterior extremity

Vitelline follicles

In 2 lateral groups from just post intestinal bifurcation to close to posterior extremity, just overlapping caeca

In 2 lateral groups, reach from VS to level distinctly anterior to ovary, just overlapping caeca dorsally and ventrally

In 2 lateral groups, reach from about halfway between VS and ovary to level of posterior testis

In 2 lateral groups, in hindbody, from slightly posterior to VS to level of anterior testis or mid-body

In 2 lateral groups, in hindbody, from slightly anterior to ovary to the posterior extremity

In 2 restricted lateral groups between VS and gonads

In 2 lateral groups, confluent posteriorly, from level of pharynx to posterior extremity

In 2 bands, occupy full body width from midway between VS to ovary and ovary to anterior testis

In 2 lateral groups, may extend from forebody to level of testes

Excretory vesicle

Y-shaped, bifurcates lateral to ovary, narrow posteriorly, widens and reaches uterus

Not clear

Not clear

Y-shaped, bifurcated

Bifurcated

Bifurcated

Unknown

Bifurcated

Y-shaped, bifurcated

Excretory vesicle arms

May extend to level of pharynx, excretory pore terminal at posterior end of body

Not clear

Not traced beyond posterior testis

Reach level of pharynx

Reach pharynx

Reach pharynx

Unknown

Reach pharynx

Reach level of pharynx

Hosts

Freshwater fishes (Latidae: L. angustifrons, L. mariae, L. microlepis)

Freshwater fishes (Latidae: L. angustifrons, L. microlepis)

Freshwater fishes (Latidae: L. angustifrons, L. microlepis)

Freshwater and marine fishes; reptiles

Freshwater fishes (Malapteruridae, Citharinidae and pelicans - probable pseudoparasitism)

Marine fishes (Albulidae, Sphyraenidae)

Freshwater fishes (Pimelodidae)

Marine fishes (Uranoscopidae)

Marine fishes

Site in host

Immature specimens in intestine; eggs-bearing specimens in pyloric caeca and gall-bladder

Intestine

Intestine

Intestine

Intestine

Intestine

Intestine

Intestine

Intestine

Distribution

Africa (Lake Tanganyika)

Africa (Lake Tanganyika)

Africa (Lake Tanganyika)

Cosmopolitan

Africa

North America (Florida, USA)

South America (Brazil)

Japan

Atlantic, Indian and Pacific Oceans

Type-species

N. tanganyikae (Prudhoe, 1951) Manter & Pritchard, 1969

Tanganyikatrema fusiforma n. g., n. sp.

Grandifundilamena novemtestes n. g., n. sp.

A. spiniceps  (Looss, 1896) Looss, 1899

B. pelecani Dollfus, 1950

C. longula Overstreet, 1969

I. iheringi Travassos, 1947

I. mediolecithale Ozaki, 1927

S. vinaledwardsii (Linton, 1901) Linton, 1910