Trimusculotrema heronensis sp. nov. (Monogenea, Capsalidae) from the skin of the pink whipray Himantura fai (Elasmobranchii, Dasyatidae) from Heron Island, Queensland, Australia

Abstract

Trimusculotrema heronensis sp. nov. is described from the skin of the pink whipray, Himantura fai, caught at Heron Island on the Great Barrier Reef, Queensland, Australia. The parasite differs from its closest relative,
T. uarnaki, by its greater size and by features of the cirrus. There is evidence that the haptor of T. heronensis secretes cement. The living parasite is unable to swim. Whether Trimusculotrema spp. are benedeniines or entobdellines is discussed.

Full text

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Trimusculotrema heronensis sp. nov. (Monogenea, Capsalidae)
from the skin of the pink whipray Himantura fai
(Elasmobranchii, Dasyatidae) from Heron Island,
Queensland, Australia
Author copy
Ian D. Whittington1,2*and Graham C. Kearn3
1Monogenean Research Laboratory, Parasitology Section, The South Australian Museum, North Terrace, Adelaide,
South Australia 5000, Australia; 2Marine Parasitology Laboratory, School of Earth and Environmental Sciences (DX 650 418),
The University of Adelaide, North Terrace, Adelaide, South Australia 5005, Australia; 3School of Biological Sciences,
University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
Abstract
Trimusculotrema heronensis sp. nov. is described from the skin of the pink whipray, Himantura fai, caught at Heron Island on
the Great Barrier Reef, Queensland, Australia. The parasite differs from its closest relative, T. uarnaki, by its greater size and
by features of the cirrus. There is evidence that the haptor of T. heronensis secretes cement. The living parasite is unable to swim.
Whether Trimusculotrema spp. are benedeniines or entobdellines is discussed.
Keywords
Platyhelminthes, Monogenea, Capsalidae, Trimusculotrema, subfamilial status, ectoparasites of rays
*Corresponding author: whittington.ian@saugov.sa.gov.au
Introduction
In February 1991, examination of the skin surfaces of a sting-
ray identified as a pink whipray, Himantura fai Jordan et Seale
(Dasyatidae), from Shark Bay, Heron Island, Queensland,
Australia revealed a single specimen of a capsalid monoge-
nean in Trimusculotrema Whittington et Barton, 1990. There
are no previous records of species in this genus from fishes off
Heron Island. Atotal of 33 specimens of H. fai was examined
by IDW between 1987 and 1991, during five separate visits
to Heron Island, but only a single specimen of the monoge-
nean described in this paper was found. Since 1991, another
32 specimens of H. fai at Heron Island have been examined
for Monogenea by IDWduring on-going parasitological stud-
ies (e.g. collaborations with Drs L.A. Chisholm, B.W. Cribb
and P.R. Last; teaching Parasitology to undergraduate students
in field courses). Despite these activities, no further specimens
of Trimusculotrema have been recovered from Heron Island.
We appreciate that a descriptive study based on a single par-
asite specimen is not ideal. It was possible, however, to con-
duct a detailed study of the anatomy of this living specimen
using phase contrast microscopy and photomicrography. Fur-
thermore, its anatomy is distinctive. Brief reference has al-
ready been made to this parasite as Trimusculotremasp. in the
following: Kearn (1994, see his Fig. 4E); Whittington and
Last (1994, see their page 288); Kearn (1998, see pages 99–
100 and his Fig. 5.7e), Kearn (1999, see his page S70); Whit-
tington and Cribb (2001, see their page 164).
Materials and methods
During many visits to the Heron Island Research Station of the
University of Queensland, Australia between 1987 and 2002,
live specimens of Himantura fai (wingspans 51–87 cm) were
captured by beach seine or hand line on a rising tide at Shark
Bay. Fish were identified from descriptions in Grant (1987),
by consultation with Dr Peter Last (CSIRO Marine and At-
mospheric Research, Hobart, Tasmania) and by reference to
Last and Stevens (1994) and Whittington and Last (1994).
Immediately after capture, live stingrays were placed in a
large concrete pool (capacity: 7500 l) containing flow-through
sea water for no longer than five days before examination for
monogeneans. Rays were killed by pithing. Using a scalpel
blade, skin scrapings from dorsal and ventral surfaces of ray
specimens were placed in separate glass Petri dishes contain-
ing filtered sea water (FSW; filtered through two sheets of
Whatman No. 1 filter paper) and examined for parasites using
DOI: 10.2478/s11686-008-0044-5
© 2008 W. Stefañski Institute of Parasitology, PAS
Acta Parasitologica, 2008, 53(3), 251–257; ISSN 1230-2821

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Ian D. Whittington and Graham C. Kearn
a stereomicroscope with transmitted illumination. The anato-
my of the single specimen found was studied alive while par-
tially flattened beneath a coverslip and viewed using bright
field and phase contrast microscopy. Extensive use was made
of bright field photomicrography. When studies of the live
parasite were complete, the specimen was flattened and pre-
served beneath a coverslip in 10% buffered neutral formalin at
room temperature (24°C), stained with Ehrlich’s haematoxy-
lin, dehydrated in an ethanol series, cleared in methyl salicy-
late and mounted in Canada balsam. The flattened whole
mount was examined using a compound microscope equipped
with phase contrast optics and a drawing tube. Measurements
were made using a computerised digitising system similar to
that described by Roff and Hopcroft (1986). Unless otherwise
indicated, measurements are presented in micrometres. For
paired structures (e.g. posterior hamuli, anterior attachment
organs, testes), measurements of each structure are given sep-
arately, followed by the mean in parentheses. Where mea-
surements are presented in paired sets separated by a multipli-
cation sign, the first figure is length, the second width. Haptor
terminology for capsalids follows Whittington et al. (2001).
Comparison was made with 7 specimens of Trimusculo-
trema uarnaki from the personal collection of Dr Ian Whit-
tington (7 of the 11 paratypes given by Whittington and Bar-
ton 1990 as in the ‘collection of senior author’; these slides are
etched as CAP39–41; CAP43–45; CAP48). This material is
now deposited as paratypes in The Australian Helmintholog-
ical Collection, Parasitology Section, The South Australian
Museum, North Terrace, Adelaide 5000, South Australia,
Australia (SAMAAHC; contact: Dr Ian Whittington) as AHC
29482–AHC 29488 (7 slides, 1 specimen per slide). The sin-
gle specimen (holotype) of the proposed new species is also
deposited in the Australian Helminthological Collection
(AHC 29481).
Results
Capsalidae Baird, 1853
Benedeniinae Johnston, 1931 (but see Discussion)
Trimusculotrema heronensis sp. nov. (Figs 1–7)
Type host and locality: Himantura fai Jordan and Seale (Da-
syatidae) (pink whipray); Heron Island (23°27´S, 151°55´E),
Great Barrier Reef, Queensland, Australia.
Site on host: Ventral skin surface.
Infection details: One of 65 stingrays infected (prevalence
1.54%) between November 1987 and November 2002; inten-
sity 1 adult specimen. The only specimen of this new taxon
was collected on 26 February 1991 from a female H. fai with
a wingspan of 69 cm.
Origin of name: The species name refers to the type-local-
ity, Heron Island, a small coral cay at the southern end of the
Great Barrier Reef, Queensland, Australia.
Holotype: SAMAAHC 29481 (1 whole mount).
Description (Figs 1–7): Trimusculotrema sensu Whitting-
ton et Barton, 1990. Based on single, sexually mature speci-
men studied alive (Fig. 1) and following preservation as well-
flattened whole mount (Fig. 2); measurements from well-flat-
tened, preserved whole mount. Total length including haptor
5.753 mm; maximum breadth at level of testes 3.754 mm
(Figs 1 and 2). Haptor oval 1.677 × 1.422 mm, aseptate; notch
in haptor margin (see Figs 1, 2 and 3A) considered abnormal.
Ventral surface of haptor bearing radially arranged papillae,
circular (diameter 24–46) or oval (38 × 24–56 × 38) (Figs 1,
2 and 3A), lacking associated sclerites or petal-like exten-
sions. Papillae tend to increase in size and adopt a more oval
shape from margin of haptor towards centre, but papillae ab-
sent in region of peduncular connection (Fig. 3A). Lengths of
median haptoral sclerites as follows: accessory sclerite (one of
pair absent, Figs 2 and 3A; considered abnormal) 78 (n = 1),
proximal bifid notch ill-defined (Fig. 3B), no tendons ob-
served associated with accessory sclerite; two anterior hamuli
56, 56 (56, n = 2) respectively (Fig. 3C); two posterior hamuli
46, 48 (47, n = 2) respectively (Fig. 3D). Fourteen hooklets
distributed around haptor periphery (Fig. 3A, E); posterior-
252
Œl¹ski
Fig. 1. Trimusculotrema heronensis sp. nov. in ventral view.
Composite image of nine bright field photographs of the live single
specimen reported here. Scale bar = 1 mm
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Trimusculotrema heronensis sp. nov. from Himantura fai in Australia
most pair (hooklets II, see Llewellyn 1963 for numbering sys-
tem) between posterior hamuli. Distances between adjacent
hooklets increase in posterior-anterior direction. Hooklets lo-
cated at a distance from haptor margin, posterior hooklets
approximately 38 from haptor edge, anterior hooklets approx-
imately 62 from edge. Hooklets in line with rows of papillae
(Fig. 3A). Most hooklets not flat, hence unsuitable for length
measurements; lengths of two flat hooklets about 15 (Fig. 3E).
Marginal valve absent; no marginal ribs on haptor. Three nar-
row circular muscle bands visible on right side only of haptor
(Figs 2 and 3A); extra (fourth) band created for short distance
by branching of inner band. Peduncle from body joining hap-
tor centrally.
Two anterior attachment organs as saucer-like discs, almost
circular 457 × 525, 478 × 557 (468 × 541, n = 2) respectively;
anterior region of each disc glandular. Gland cells with weak
affinity for Ehrlich’s haematoxylin in anterior region of body
between attachment discs (Fig. 2); because of opacity, these
gland cells are conspicuous in the living animal viewed by
transmitted light (Figs 1 and 4); ducts not observed. Ventral
surface underlying gland cells bears narrow convoluted orna-
mentations (ridges?) resembling human fingerprint (Fig. 5).
Eyes two pairs, dorsal, pigment shielded, immediately ante-
rior to pharynx; no lens remnants observed. Mouth ventral,
median, at level of eyes. Pharynx 494 × 810. Intestinal caeca
dendritic anteriorly laterally and medianly; posterior conflu-
ence not determined. Excretory bladders conspicuous (Figs 1,
2 and 4), orientated along longitudinal body axis at level of
male copulatory apparatus, ootype and vagina.
Reproductive system shown in Figure 2 and enlarged in
Figure 6; general plan clear in live specimen (Fig. 1). Arrange-
ment of reproductive organs and associated ducts as in other
Trimusculotrema spp. (e.g. see Whittington and Barton 1990).
Testes ovoid, juxtaposed, relatively small, 331 × 577, 354 ×
600 (342 × 588, n = 2) respectively. Glands of Goto not ob-
served in posterior angle between testes but two large con-
spicuous, uninucleated cells resembling glands of Goto locat-
ed one on each side of germarium, immediately anterior to
each testis (Fig. 2); no ducts observed from these cells. Vasa
efferentia not observed in whole mount. Vas deferens narrow
proximally following course shown in Figure 6. Male copu-
253
Stanis³a
Zdzis³aw
Fig. 2. Trimusculotrema heronensis sp. nov. in ventral view. Drawn
from the single specimen (holotype): ad – adhesive disc, b – excre-
tory bladder, c – cirrus, cl – cell resembling gland of Goto, e – egg
in ootype, g – germarium, gc – gland cells, h – haptor (see Fig. 3 for
detail), m – mouth, mr – male accessory gland reservoir, p – pharynx,
sr – seminal receptacle, sv – seminal vesicle, t – testis, u – uterus,
uo – uterine opening (dorsal), v – vitellarium, va – vagina, vd – vas
deferens, vo – vaginal opening (ventral), vr – vitelline reservoir.
Scale bar = 1 mm
Fig. 3. Haptor and sclerites of Trimusculotrema heronensis sp. nov.
A. Enlarged ventral view of haptor rotated into antero-posterior ori-
entation. Broken circle: position of peduncle joining haptor to body.
Arrow: notch in haptor margin, considered abnormal; ah – anterior
hamulus, as – accessory sclerite (one of pair missing), h – hooklet,
mb – muscle band, pa – papilla, ph – posterior hamulus. B. Acces-
sory sclerite. C.Anterior hamulus. D.Posterior hamulus. E.Hooklet.
Scale bars = 250 µm (A), 25 µm (B-E)
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Ian D. Whittington and Graham C. Kearn
latory organ a cirrus (see below). Vas deferens enters double-
walled cirrus sac dorsally, travels proximally, widening to
form narrow reservoir (seminal vesicle?) containing droplets
ranging in diameter from 3 to 9, together with finer granular
material in places; sperm not identified in seminal vesicle.
Cirrus sac also contains capacious elongate male accessory
gland reservoir (termed ‘spermatophore matrix reservoir’by
Whittington and Barton 1990), containing prominent droplets
(16 to 53 in diameter) and granular matrix; receives narrow
ducts from presumed male accessory glands entering cirrus
sac proximally but gland cells not observed. Ducts from sem-
inal vesicle and accessory gland reservoir run parallel and
enter short chamber communicating with proximal end of cir-
rus (Fig. 6). Male pore through which cirrus everts ventral,
submarginal, near left body margin (Fig. 2). Lining of un-
everted cirrus bears ridges (Figs 1 and 6); as cirrus everts, ridges
transported to outer surface of cirrus where they appear rough-
ly transversely orientated with respect to cirrus (Fig. 7A);
ridges project from everted cirrus in proximal direction, like
eaves of roof or posterior margins of segments of craspedote
tapeworm (Fig. 7A). There are indications that ridges are spi-
rally arranged and continuous (Fig. 7A). Diameter of everted
cirrus 152; length of everted region of cirrus bearing ridges
998.
Germarium with large, central fertilisation chamber con-
taining at least 75 ripe oocytes giving rise to oviduct, receiv-
ing common vitelline duct to become ovo-vitelline duct (Figs
2 and 6). Vitelline reservoir immediately anterior to germar-
ium. Ootype at level of excretory bladders. Uterine pore sep-
arate from male pore, capacious in whole mount and opening
dorsally near left body margin, just posterior to male pore at
level of eyes and mouth (Fig. 2). No distinct sphincter ob-
254
Roborzyñski
rosbœŸæv
fjad kadsææ¿æ
Fig. 4.Anterior region of Trimusculotrema heronensis sp. nov. pho-
tographed alive (bright field optics) in dorsal view, showing gland
cells (gc) between anterior adhesive discs (ad); b – excretory blad-
ders, c – cirrus, p – pharynx. Scale bar = 500 µm
Fig. 5.Ornamentation (ridges?) on ventral surface of Trimusculotrema
heronensis sp. nov. between anterior adhesive discs (ad). Phase con-
trast image. Scale bar = 50 µm
Fig. 6. Semi-diagrammatic, enlarged ventral view of most of the
reproductive system of Trimusculotrema heronensis sp. nov.: c – cir-
rus in uneverted position, cs – cirrus sac, fc – fertilisation chamber,
md – ducts of male accessory gland, ov – ovo-vitelline duct, rm – cir-
rus retractor muscle (?). Other lettering as in Figure 2. Scale bar
= 500 µm
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Trimusculotrema heronensis sp. nov. from Himantura fai in Australia
served in association with uterine pore. Vagina thick walled,
with voluminous proximal region bearing seven roughly spher-
ical seminal receptacles in living animal (Figs 2 and 6); recep-
tacles less distinct in whole mount. Single short duct connects
proximal region of vagina with anterodorsal region of vitelline
reservoir. From large proximal region, vagina runs anterolater-
ally for short distance, narrows before opening ventrally be-
tween mid-line and left body margin at level of ootype (Fig. 2).
Vitelline follicles extend from level of pharynx to posterior end
of body proper; not extending anterior to eyes (Figs 1 and 2).
No free eggs observed; one egg in ootype of flattened
whole mount seen in side view; roughly triangular; total cap-
sule length 198, capsule breadth 126; appendage folded back
on itself, total length 499 (Figs 1 and 6).
Observations on the living parasite (Fig. 1): Trimusculo-
trema heronensis attached itself to a glass surface by means of
the haptor. When the edge of the haptor was lifted using a fine
needle, the haptor did not detach immediately from the glass.
It was necessary to peel off the haptor, which was still firmly
attached when about one third of the haptor surface was free
of the substrate.
There were no indications that the fully detached parasite
could swim.
Differential diagnosis: Trimusculotrema heronensisis sig-
nificantly larger (total length 5.753 mm) than the four other
species of Trimusculotrema, namely T. micracantha (Euzet et
Maillard, 1967) Whittington et Barton, 1990 (total length 2–3
mm; see Euzet and Maillard 1967), T.leucanthemum(Euzet et
Maillard, 1967) Whittington et Barton, 1990 (also described
from a single specimen; total length 1.65 mm; see Euzet and
Maillard 1967), T. uarnaki Whittington et Barton, 1990 (total
length 1.432–2.661 mm; see Whittington and Barton 1990)
and T. schwartzi Dyer et Poly, 2002 (total length 0.9–3.425
mm; see Dyer and Poly 2002). Trimusculotrema heronensisis
readily distinguished from T. micracantha by the vagina,
which in the former opens at the level of the ootype and in the
latter opens close to the left anterior adhesive disc (Euzet and
Maillard 1967). Each haptor papilla of T. leucanthemum is
surmounted by a central circular sclerite and surrounded by
11–13 thin petal-like extensions, creating the appearance of a
flower (Euzet and Maillard 1967). The haptor papillae of
T.heronensis have no sclerites or petal-like extensions. More-
over, the haptor margin of T. leucanthemum has equally
spaced radial ribs, not present in T. heronensis. Trimusculo-
trema schwartzi is readily distinguished from T.heronensis by
the following features: the anterior hamuli of T. schwartzi are
longer (mean 114, range 60–205) compared with 56 in T. he-
ronensis; T. schwartzi has no pigment shields associated with
the eyes; in T.schwartzi,the two large cells resembling glands
of Goto occupy a more median position between the testes and
germarium; no ridges were described on the cirrus of
T. schwartzi. Trimusculotrema heronensis is most similar to
T. uarnaki but, with the exception of the lengths of the haptor
sclerites, anatomical measurements of the former parasite are
significantly larger. The everted cirruses of T. heronensis and
T. uarnaki bear transverse ridges, but those of T. heronensis
appear to be continuous and spirally arranged and resemble
the overlapping posterior margins of the segments of a cras-
pedote tapeworm (Fig. 7A), whereas no spiral pattern was
detected on the cirrus of T. uarnaki and the transverse ridges
are narrow and appear to be incomplete (Fig. 7B, C). Trimus-
culotrema heronensis is parasitic on the ventral skin surface
of the stingray, Himantura fai (Dasyatidae), known as the pink
whipray.
255
Fig. 7. The everted cirruses of A – Trimusculotrema heronensis sp. nov. photographed alive (bright field optics) in dorsal view and of B and
C – T. uarnaki Whittington et Burton, 1990, and for comparison also in dorsal view, photographed from a preserved and mounted specimen
viewed with phase contrast optics in two different focal planes. Scale bars = 250 µm (A), 50 µm (B, C)
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Ian D. Whittington and Graham C. Kearn
Discussion
In spite of an intensive search of many individual specimens
of the pink whipray, Himantura fai, at Heron Island over a
period of 15 years, only one adult specimen of the skin para-
sitic monogenean Trimusculotrema heronensis has been found.
However, this single parasite specimen was alive and in excel-
lent condition (Fig. 1). It not only has a different host species
but is significantly larger than the four other known species
of Trimusculotrema, namely T. micracantha (Euzet et Mail-
lard, 1967) Whittington et Barton, 1990, T. leucanthemum
(Euzet et Maillard, 1967) Whittington et Barton, 1990 (also
known only from one specimen), T. uarnaki Whittington et
Barton, 1990 and T. schwartzi Dyer et Poly, 2002. Moreover,
other features, particularly of the vagina, cirrus and haptor
papillae, readily distinguish T. heronensis from the other
species of Trimusculotrema.
There is uncertainty as to whether Trimusculotrema spp.
belong to the Benedeniinae Johnston, 1931 or to the Entobdel-
linae Bychowsky, 1957. Whittington and Barton (1990) re-
garded them as benedeniines but the possibility that Trimus-
culotrema spp. may belong to the Entobdellinae was men-
tioned by Kearn et al. (2007). The reason for this systematic
uncertainty relates to the absence of what is regarded as the
most reliable difference between benedeniines and ento-
bdellines, namely the route taken by the two tendons running
into the haptor from extrinsic muscles at the posterior end of
the body. In benedeniines and entobdellines, each of these ten-
dons passes through a posterior notch in an accessory sclerite,
but in benedeniines the tendon runs out into the haptor and
attaches to the base of the ventral haptor tegument, while in
entobdellines this tendon typically attaches to the anterior end
of the anterior hamulus. In Trimusculotrema spp., all of the
median haptor sclerites (accessory sclerites, anterior and pos-
terior hamuli) are greatly reduced in size (e.g. Figs 2 and 3),
the notch in the accessory sclerite is barely discernible and
there is no trace of tendons associated with the accessory scler-
ites. The problem is exacerbated by other anatomical features:
anterior attachment discs are generally regarded as features
of benedeniines while the presence of haptor papillae is a fea-
ture of entobdellines. In addition, benedeniines are primarily,
possibly exclusively, parasites of teleosts (Yamaguti 1963,
Whittington 2004), while elasmobranchs are the principal
hosts for entobdelline monogeneans except for Entobdel-
la spp. which mostly parasitise teleost flatfishes (Kearn et al.
2007). As pointed out by Whittington and Barton (1990), the
similar anatomy of benedeniines and entobdellines could
reflect their similar life styles leading to convergent evolution,
and features such as adhesive discs could have evolved inde-
pendently in entobdellines as well as in benedeniine monoge-
neans. The application of molecular techniques may be the
only way to solve this dilemma.
In entobdellines, the fully developed extrinsic body mus-
cles and their tendons serve to generate suction by lifting the
anterior ends of the anterior hamuli and thereby raising the
roof of the cup-shaped haptor in which the shafts of the hamuli
are embedded (Kearn 1964). Avalve around the margin of the
haptor prevents any influx of seawater into the cup when its
roof is lifted. Presumably the haptor of a benedeniine func-
tions in a similar way, except that the haptor roof is lifted
directly by the muscle/tendon system. Trimusculotrema has
abandoned this system, having lost the tendons and their mus-
cles and has greatly reduced median haptor sclerites. It is
known that Entobdella soleae has a second method of gener-
ating haptor suction using the intrinsic muscles of the haptor
rather than the extrinsic muscle/tendon/sclerite system (Kearn
1988). As suggested by Whittington and Barton (1990), Tri-
musculotrema spp. may have become dependent on the intrin-
sic muscles of the haptor to generate suction, permitting a re-
duction of the extrinsic muscle/tendon/sclerite system. How-
ever, the absence of a marginal valve suggests that the haptor
of Trimusculotrema does not generate suction for attachment
and the notch (regarded as abnormal) in the haptor margin of
T. heronensis also seems likely to prevent an adequate seal at
this point. Our observations on the single healthy living spec-
imen of T. heronensis indicate that an adhesive secretion may
be used for haptor attachment. The use of adhesive secretion
for haptor attachment, with associated reduction of haptor
sclerites has also been adopted by other monogeneans, such as
Leptocotyle minor (see Kearn 1965), Hamatopeduncularia
spp. (see Kearn and Whittington 1994) and Neocalceosto-
moides brisbanensis (see Kearn et al. 1995).
Within the cirrus sac of T. heronensis, the male accessory
gland reservoir and the seminal vesicle contain droplets and
finely granular material. The droplets in the accessory gland
reservoir were mostly larger than those in the seminal vesicle
(Fig. 1). Granular material is described by Whittington and
Barton (1990) in the ‘spermatophore matrix reservoir’(= male
accessory gland reservoir) of T. uarnaki and is visible in their
fig. 13, a photograph of a living animal. Bullard et al. (2004)
found similar material in the male accessory gland reservoir of
the capsalid monogenean Listrocephalos corona. The origins
and function of this material are obscure. In T. heronensis, the
gland ducts entering the proximal end of the cirrus sac and
communicating with the male accessory gland reservoir are
too narrow to accommodate droplets of the size found in the
reservoir, indicating perhaps that the droplets condense after
the male accessory secretion enters the reservoir. The droplets
in the seminal vesicle are small enough to enter via the vas
deferens but none were found here. Like the droplets in the
male accessory gland reservoir, they may condense after en-
tering the seminal vesicle from material produced by the
testes. It is also possible that handling the living animal may
result in reflux into the seminal vesicle of some of the contents
of the accessory gland reservoir and the partial trituration of
the larger droplets from the reservoir.
It is known that juveniles and adults of the entobdelline
monogenean Neoentobdella natans Kearn et Whittington, 2005
from the skin of the stingray Pastinachus sephen(Dasyatidae)
and of N. parvitesticulata Kearn et Whittington, 2005 from
the skin of H. fai at Heron Island are able to swim freely by
undulating the body when fully detached from the host (Kearn
256
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Trimusculotrema heronensis sp. nov. from Himantura fai in Australia
and Whittington 1991, as Entobdella sp. for N. natans; Kearn
and Whittington 2005 for N. parvitesticulata). There were no
indications that the fully detached living specimen of T. hero-
nensis could swim.
Acknowledgments. We are indebted to Di Barton, Leslie Chisholm,
Marnie Horton, Margaret Kearn, Sally and Ray Roth and numerous
undergraduate students enrolled between 1994 and 2001 in
Parasitology Field Studies at The University of Queensland for help
with collecting rays at Heron Island. We appreciate the access to
infrastructure and facilities at the Heron Island Research Station
(HIRS) of The University of Queensland. Financial support for this
investigation was provided by Australian Research Council (ARC)
grant no. A191941 awarded to both authors in 1991, grant nos.
A18716336 (1988–89), A19130175 (1992–94) and A19231545
(1993–95) awarded to IDW and grant no. DP0556780 (2005–07)
awarded to IDW and Professor Steve Donnellan (Evolutionary
Biology Unit, South Australian Museum). The visit by GCK to
Queensland, Australia in 1990–91 was supported jointly by an
Overseas Study Visit Grant from The Royal Society (UK) and a
Travel Grant from The University of Queensland. GCK also grate-
fully acknowledges financial assistance from the Browne, Hill and
Murray Committee of The Royal Society (UK) for a visit to HIRS.
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