Site by Bennett Web & Design Co.
2009 SOUTHEASTERN NATURALIST 8(4):599–608
Pathology of the Trematode Alloglossidium renale in the
Freshwater Grass Shrimp Palaemonetes kadiakensis
Stephen C. Landers1,* and Rebecca D. Jones1
Abstract - The trematode Alloglossidium renale was commonly observed in the
freshwater shrimp Palaemonetes kadiakensis in Pike County, AL, with a prevalence
of 30.2% and 12.7% at two different collection sites. Sectioned antennal glands
demonstrated tissue damage near the parasite, including antennal gland tubule cell
compression and destruction of host cells. Normal tubules as well as those showing
cellular changes were functional and contained parasite ova. Grass shrimp outlive
this infection, as evidenced by masses of ova and debris within infected antennal
glands, but no viable parasite. The non-lethal nature of the parasite helps to explain
the high intensity of infection observed at one of the collection sites. This study
furthers our understanding of the effect of this parasite on its host, and extends the
reported range of Alloglossidium renale to Alabama.
Alloglossidium renale Font and Corkum is a parasite (Trematoda: Macroderoididae)
found within the antennal glands of Palaemonetes kadiakensis
Rathbun (Mississippi Grass Shrimp). It was first described in Louisiana
(Font and Corkum 1975), and has since been the subject of many articles
(Brooks 2003; Carney and Brooks 1991; Font 1980; Font and Corkum 1976,
1977; Lefebvre and Poulin 2005; Smythe and Font 2001). The complete life
cycle is not known (the molluscan intermediate host has not been identified),
though it has been determined that the parasite becomes mature within the
antennal glands of shrimp and that no vertebrate host is required. The shrimp
stage is considered either an adult or a progenetic metacercaria by different
authorities (Lefebvre and Poulin 2005). Within the Order Plagiorchiformes,
the genus is considered to be derived due to its 2-host life cycle, having
likely evolved from a 3-host life cycle (Carney and Brooks 1991, Smythe
and Font 2001)
During the summer of 2007, numerous freshwater shrimp from Pike
County, AL, were observed with dark masses behind the antennal scales
where the antennal glands are located. The masses were identified as A.
renale, prompting a histological investigation into the effects of the worm
on its host. The objectives of this study were to determine the pathological
effects of A. renale on the host antennal gland and to determine if such infections
impair kidney function and host size.
1Department of Biological and Environmental Sciences, Troy University, Troy, AL
36082. *Corresponding author - firstname.lastname@example.org.
600 Southeastern Naturalist Vol. 8, No. 4
Materials and Methods
Palaemonetes kadiakensis were collected along the grassy edges of the
Conecuh River (31º48'15"N, 86º2'49"W) and Olustee Creek (31º56'38"N,
86º7'6"W) by dip net in Pike County, AL, between June 2007 and August
2008. The animals were returned to Troy University and maintained in water
from the collection site. Animals were measured (anterior end of rostrum–
posterior end of uropods), and infection with A. renale was recorded. Worms
for whole-mount preparation were fixed in 5–10% formalin and stained with
Gill’s hematoxylin. Except for the initial collection of 3 worms, the fixative
was used at room temperature and was not heated. Worms and antennal glands
prepared for paraffin sections were fixed in 5–10% formalin before infiltration
with Paraplast. Ten-μm sections were cut on a rotary microtome and stained
with Gill’s hematoxylin and fast green. Worms and antennal glands prepared
for plastic sections were fixed at room temperature in 2–3% glutaraldehyde
buffered in 0.1M sodium cacodylate, pH 7.2, and post-fixed in 2% buffered osmium
tetroxide before infiltration with Spurr’s resin. Sections (1–2 μm) were
cut on an ultramicrotome with a diamond knife and stained with toluidine blue
(1% toluidine blue, 1% sodium tetraborate). Some specimens for plastic sections
were fixed in unbuffered 2% glutaraldehyde only.
Specimens were photographed with a Nikon DXM 1200 digital camera
mounted on a Nikon E600 light microscope. Images were adjusted for brightness,
contrast, and gamma levels using Adobe Photoshop Elements 6.0.
Alloglossidium renale infections were visible through the host exoskeleton
at the base of the antennal scale. The worms occasionally moved within
the antennal glands. When dissected from the host, the worms moved actively,
contracting and expanding the oral sucker. Some worms regurgitated
material from the digestive caeca when removed from the host, and others
released a string of ova from the genital pore. The ova were sticky and remained
in a string until disturbed. The prevalence data and host measurments
for the 2 collection sites are reported in Table 1.
Alloglossidium renale was identified by 1) its specific habitat in the antennal
gland of freshwater Palaemonetes kadiakensis in North America, 2) its
progenetic development in an invertebrate definitive host, and 3) comparison
Table 1. Occurrence of Alloglossidium renale in Palaemonetes kadiakensis from Pike County, AL.
Average host length
Location # infected Total % infected Infected (mm) Uninfected (mm)
Conecuh River 23 76 30.2 23.4 19.7
Olustee Creek 31 243 12.7 31.0 29.4
All sites 54 319 16.9 27.8 27.5
2009 S.C. Landers and R.D. Jones 601
of whole stained specimens with the species description (Font and Corkum
1975). Specifically, the diameter of the testis relative to the body width, and
the absence of a metacercarial wall were diagnostic characteristics used in
the key provided in the previous reference. Further, the body length:width
ratio (less than 3:1), testis:ovary ratio, ovary shape, and absence of a metacercarial
wall were diagnostic characteristics for A. renale in a comparative study
of numerous species within the Macroderoididae (Smythe and Font 2001).
The average values of A. renale structures (Table 2) were smaller than those
reported in the original species description, though the maximum sizes were
within those ranges. The average length and width were within the ranges
reported by Carney and Brooks (1991). The ova were smaller than the species
description, though the maximum sizes fell within the published range.
Voucher specimens of gravid A. renale have been deposited in the US National
Parasite Collection in Beltsville, MD (USNPC 101574).
Pathology of Alloglossidium renale infections (Figs. 1–12)
Paraffin and plastic sections of Alloglossidium renale within the host or
isolated antennal glands were analyzed. The best fixation and histology were
observed with buffered glutaraldehyde and osmium, with plastic sections.
Sections revealed either one or two parasites folded within an antennal gland
(though we have observed 5 worms within one antennal gland). The worms
were surrounded by antennal gland tubules with intact lumena (Fig. 1). In
some cases, the trematode had grown to a large enough size to reduce the
amount of remaining host renal tissue (Figs. 2–3, 5). The tissue loss was
apparently due to parasite feeding and compression due to parasite growth.
Compression of host cells was obvious when tubule nuclei were concentrated
against the parasite (Fig. 1). There was no metacercarial cyst wall or extracellular
secretion separating the parasite from the host. Evidence of parasite
material traveling throughout the antennal gland was found, including ova,
and dark spherical inclusions similar to material within the parasite uterus
(Figs. 6–9). Cellular differences were evident in some but not all host cells
near or touching the parasite (Figs. 7–9). Normal tubule cells were typically
cuboidal, had a microvillar border, and in plastic sections revealed a large
open nucleus with scattered chromatin granules (a homogeneously tinted
nucleus was produced if osmium was not used as a post-fixative). Close to
the parasite, many cells had a more squamous shape, denser cytoplasm, and
a compact nucleus (Figs. 7–9). A gradient of tubule cell morphologies was
observed in some specimens, with healthy cuboidal cells transitioning to
compact squamous cells closer to the parasite. This transition affected the
Table 2. Measurements from gravid (ova producing) Alloglossidium renale (in microns).
Body Body Oral Ventral Anterior Posterior Ova Ova
length width sucker sucker testis testis Ovary length width
Average 992 423 108 92 84 100 214 22 12
n 14 14 12 8 4 3 4 10 10
Range 600–1560 225–545 90–135 47–125 50–120 75–125 195–230 19–25 9–14
602 Southeastern Naturalist Vol. 8, No. 4
Figures 1–5. Sections through shrimp antennal glands. CP: cirrus pouch, DC: digestive
caeca, M: host muscle, PC: parenchymal cells, OS: oral sucker, U: uterus with
ova, V: vitellarium, VS: ventral sucker. 1–3. Paraffin sections. 4–5. Plastic sections.
Figure 1. Sagittal section through the worm revealing host antennal gland tubules
being consumed (top of photo at oral sucker) and tubule compression and necrosis
(compacted tubule cell nuclei at arrow). Bar = 220 μm. Figures 2–3. An infected
antennal gland in which little of the organ remains. This antennal gland contained
two worms. Only a thin layer of tissue exists between the worm and the host musculature
(arrow). Arrowhead indicates ovum. Figure 2 Bar = 200 μm. Figure 3 Bar =
100 μm. Figure 4. Uninfected right antennal gland showing normal tubule cells. Host
musculature is on the right. Bar = 100 μm. Figure 5. Left antennal gland (infected)
from same host animal as in Figure 4. Parasite tegument with spines (small dots on
surface) indicated by an arrow. Ova trapped between the host and parasite indicated
by arrowhead. Bar = 100 μm.
2009 S.C. Landers and R.D. Jones 603
cell shape, nuclear shape, chromatin distribution, and cytoplasmic density.
Very thin (<5.0 μm) squamous cells commonly abutted the parasite. Some
cells in contact with the parasite had a microvillar border, and others had lost
their brush border.
Parasite ova were present in numerous areas of infected antennal glands,
including tubules presumably leading downstream to the nephridiopore.
Most significantly, they were found within the antennal gland tubules in
areas showing pathological effects as well as normal tubules, indicating
that infected antennal glands are able to filter and transport fl uid throughout
the remaining tubule system (Fig. 7–9). Ova were also present between the
parasite and host tissue (Figs. 3, 5), as well as within the digestive caeca of
the trematode. The later location was evidently due to the parasite ingesting
its released ova while feeding upon the antennal gland.
Worm remnants or evidence of past infection were present in some antennal
glands (Figs. 10–12). Sections of antennal glands containing parasite
remnants revealed masses of ova, host cells, and debris within the host
tubules. This condition was observed twice, in the same shrimp, with both
antennal glands appearing functional and exhibiting little tubule damage. In
one antennal gland with evidence of infection (Fig. 10), sections throughout
Figure 6. Plastic section of A. renale within the host. Arrows indicate material
within the antennal gland tubule (left arrow) that is similar to material within the
parasite uterus (right arrow). This individual worm had many dark spherical inclusions,
lipid droplets, and ova within the uterus. Arrowheads indicate parasite
surface. Bar = 50 μm.
604 Southeastern Naturalist Vol. 8, No. 4
Figures 7–8. Plastic
sections of A. renale
within the host. OV:
ova, U: uterus with ova,
V: vitellarium. Figure 8
is an enlargement from
Figure 7. Ova within
antennal gland tubules
are labeled. Near the
parasite, the tubule
cells are fl attened and
have a densely-stained
cytoplasm. Nuclei in
the fl attened cells (large
arrows) are compact
and dense compared to
healthy tubules farther
away from the parasite.
Healthy tubule cells are
cuboidal, stain lightly
with toluidine, and
have open spherical
nuclei with scattered
chromatin. The brush
border is indicated in
both normal and compressed
cells (small arrows).
Bars = 100 μm.
the organ revealed no indication of a parasite except for ova, which were
found scattered in the organ and in a small spherical mass. A portion of the
gland was not sectioned (removed during initial trimming), though a worm,
if present, would not have been missed by our examination. The mass of ova
was associated with host tubule cells, recognizable by their nuclei. Debris
filled the gland tubules, and the lumen was distended, though no trace of the
worm was observed. The other infected antennal gland revealed a large mass
of parasite tissue and ova (Figs.11–12). This large mass was surrounded by
condensed and uncondensed tubule cell nuclei. The mass contained accumulations
of ova, lipid droplets, and apparently necrotic parasite tissue that was
difficult to interpret. The antennal gland was distended to accommodate the
infection, while clusters of ova were observed in tubules downstream from
Alloglossidium renale is now recorded from southeastern Alabama in
the freshwater shrimp Palaemonetes kadiakensis. This is a new distribution
record, adding to the known distribution in Louisiana (Font and Corkum
2009 S.C. Landers and R.D. Jones 605
1975) and North Carolina (Carney and Brooks 1991). In Pike County, there
was a disparate prevalence between the two collecting sites. This disparity
was not surprising given what has previously been reported for locational
and seasonal variations in the occurrence of A. renale (see Font and Corkum
1976). The disparity was probably related to the distribution of the presumed
intermediate snail host in the life cycle. We have not collected or analyzed
Palaemonetes paludosus, another reported host for this parasite (Carney and
The destruction and trauma to antennal gland cells was attributed to
1) the scraping of the parasite’s spiny tegument against the host cells, 2)
parasite growth and compression of the tubules, and 3) ingestion of host tissue.
We did not critically differentiate between the regions of the antennal
gland (antennal gland tubules [labyrinth], bladder, coelomosac) for all of the
cells in our sections (Bell and Lightner 1988, Miller 1990, Parry 1955, Peterson
and Loizzi 1973). Most of the cells surrounding the worm were consistent
with tubule cells, but may represent other antennal gland cell types as
well. It is likely that all cells involved in the antennal gland complex were
Figures 9–10. Plastic
sections of A. renale
or ova within the host.
M: host muscle, U:
uterus with ova. Figure
9. Compressed antennal
gland tubules (containing
ova) are between
the parasite and
host muscle tissue. A
(top right) also contains
ova. Small arrow inidcates
brush border of
tubule cells; Large arrows
indicate nuclei of
damaged tubule cells;
parasite surface. Bar
= 100 μm. Figure 10.
Small mass of ova and
debris within antennal
gland tubules. This
section revealed the
largest mass observed
in this antennal gland,
which is evidence of an
earlier viable parasite.
nucleus of a host tubule
cell. Bar = 50 μm.
606 Southeastern Naturalist Vol. 8, No. 4
potentially affected. A similar loss of antennal gland tissue and tissue damage
due to abrasion was reported for Alloglossoides caridicola in a crayfish
host (Turner 1985).
Font and Corkum (1976) reported that the host shrimp can outlive the
parasite. We observed evidence of this as either a necrotic mass within
Figures 11–12. Plastic sections of a large A. renale remnant within the host. Figure
11. Mass of ova and debris (right) from a necrotic A. renale within the host antennal
gland. Ova (arrowhead) are found within the surrounding tubules. Bar = 100 μm.
Figure 12. A higher magnification and different section of the remnant in Figure 11.
The mass is surrounded by host tubule cells (nuclei at arrowheads). Individual cells
are not recognizable in the mass. Bar = 50 μm.
2009 S.C. Landers and R.D. Jones 607
the host or as a mass of ova without any remnant of a worm. In these two
specimens, damage to the host organ was minimal, with apparently healthy
tubules surrounding a mass of debris with ova. These observations indicated
that the worm does not always destroy the host antennal gland before
its death. Ova present in multiple locations throughout the antennal gland
tubules (labyrinth) indicated that infected glands were able to filter fl uid
from the hemocoel and transport that fl uid downstream to the urinary bladder.
Ova within the nephridial tubule system occur in other antennary gland
parasites, such as Allocorrigia filiformis, where they were located in the
interstitial space and resulted in nodule formation and a host melanin reaction
in Procambarus clarkii (Turner 1984). We did not observe a visible
melanin reaction when non-osmicated, non-stained plastic sections were
examined. Alloglossidium infections were not only non-lethal, but in some
cases had minimal affects on the host despite the tissue damage that occurs.
The data indicating similar host lengths for infected and non-infected shrimp
(Table 1) supported this conclusion.
Many unsolved questions remain to be answered concerning A. renale and
its brief life history. As reviewed by Font and Corkum (1976), the parasites can
mature and produce ova within 6 weeks. The death of the worms occurred before
the seasonal mortality of the host, leading the authors (Font and Corkum
1976) to propose a close seasonal adaptation between parasite and host. Our
study supports this earlier work, and suggests little effect at all on the hosts
when comparing body length of infected and non-infected shrimp. An interesting
future avenue of research may be to investigate the effect of the host on
A. renale, to uncover any host response that limits the parasite. Additionally,
given the brief and predictable life cycle, and the accessibility of the parasite
(visible externally through the shrimp), this trematode may be a good model
organism for studying the biology of senescence.
The authors thank Dr. Alvin Diamond for help in collecting Palaemonetes kadiakensis
and for reviewing this manuscript, and Sarah Braune for help in the laboratory.
Portions of this research were presented at the annual meeting of the Association of
Southeastern Biologists: Jones, R.D., and S.C. Landers 2008. Morphological analysis
of the trematode parasite Alloglossidium. Southeastern Biology 55:230–231.
Bell, T.A., and D.V. Lightner, 1988. A handbook of normal penaeid shrimp histology.
Special Publication No. 1. World Aquaculture Society, Baton Rouge, LA.
Brooks, D.R. 2003. Lessons from a quiet classic. Journal of Parasitology 89:878–885.
Carney, J.P., and D.R. Brooks. 1991. Phylogenetic analysis of Alloglossidium
Simer, 1929 (Digenea: Plagiorchiiformes: Macroderoididae) with discussion of
the origin of truncated life cycle patterns in the genus. Journal of Parasitology
608 Southeastern Naturalist Vol. 8, No. 4
Font, W.F. 1980. The effect of progenesis on the evolution of Alloglossidium
(Trematoda, Plagiorchiida, Macroderoididae). Acta Parasitologica Polonica
Font, W.F., and K.C. Corkum. 1975. Alloglossidium renale n. sp. (Digenea: Macroderoididae)
from a freshwater shrimp and A. progeneticum n. comb. Transactions
of the American Microscopical Society 94:421–424.
Font, W.F., and K.C. Corkum. 1976. Ecological relationship of Alloglossidium
renale (Trematoda: Macroderoididae) and its definitive host, the fresh-water
shrimp, Palaemonetes kadiakensis, in Louisiana. American Midland Naturalist
Font, W.F., and K.C. Corkum. 1977. Distribution and host specificity of Alloglossidium
in Louisiana. Journal of Parasitology 63:937–938.
Lefebvre, F., and R. Poulin. 2005. Progenesis in digenean trematodes: A taxonomic
and synthetic overview of species reproducing in their second intermediate hosts.
Miller, D.S. 1990. Crustacean urinary bladder as a model for vertebrate renal proximal
tubule. Pp. 47–60, In A. D. Woodhead and K. Vivirito (Eds.). Nonmammalian
Animal Models for Biomedical Research, CRC Press, Boca Raton, FL. 393 pp.
Parry, G. 1955. Urine production by the antennal glands of Palaemonetes varians
(Leach). Journal of Experimental Biology 32:408–422.
Peterson, D.R., and R.F. Loizzi. 1973. Regional cytology and cytochemistry of the
crayfish kidney tubule. Journal of Morphology 141:133–146.
Smythe, A.B., and W.F. Font. 2001. Phylogenetic analysis of Alloglossidium (Digenea:
Macroderoididae) and related genera: Life-cycle evolution and taxonomic
revision. Journal of Parasitology 87:386–391.
Turner, H.M. 1984. Orientation and pathology of Allocorrigia filiformis (Trematoda,
Dicrocoeliidae) from the antennal glands of the crayfish Procambarus clarkii.
Transactions of the American Microscopical Society 103:434–437.
Turner, H.M. 1985. Pathogenesis of Alloglossoides caridicola (Trematoda) infection
in the antennal glands of the crayfish Procambarus acutus. Journal of Wildlife
Diseases 21:459–461.dget studies employing instantaneous sampling. Ethology 114:999–