Smithsoniarhynches, a new genus of interstitial
Gnathorhynchidae (Platyhelminthes: Kalyptorhynchia)
from Mosquito Lagoon and Indian River Lagoon, Florida
Rick Hochberg
Smithsonian Marine Station, 701 Seaway Drive, Fort Pierce, FL 34981, USA. E-mail: Hochberg__Rick@yahoo.com
A new genus of marine, interstitial schizorhynch (Platyhelminthes: Kalyptorhynchia) is described from
sediment collected in Mosquito Lagoon and Indian River Lagoon, Florida, USA. Smithsoniarhynches is char-
acterized by the presence of proboscis hooks constructed of ten individual spine-like teeth that emerge
separately from a basal plate. Histology and confocal laser scanning microscopy are used to reveal addi-
tional details of the proboscis musculature and reproductive anatomy. The type species, Smithsoniarhynches
sherryreedae sp. nov., is characterized by well-developed proboscis pads, four pairs of proboscis retractor
muscles, and a pharynx in the midbody region. The male reproductive system consists of an anterior
testis, muscular seminal vesicle, copulatory bulb lined with spiral and circular muscles, and a sclerotic
stylet. The female system consists of an unpaired vitellarium, ovary, uterus and bursa. The bursa tissue
surrounds a muscular bursa seminalis with distinct sphincter muscles. The new genus is compared with
the known 11 genera within the Gnathorhynchidae to establish a tentative hypothesis of relationships.
INTRODUCTION
Kalyptorhynchia is a species-rich taxon of microscopic,
free-living platyhelminthes that occupy the sediments of
salt marshes, sand ?ats and low- and high-energy
beaches. Most species live within the interstitial pore
spaces that characterize these sedimentary environments
and are thus a general component of the meiofauna.
Kalyptorhynchs can reach high abundances and species
diversity in both temperate (Reise, 1988) and tropical
sands (Dittmann, 1998).
As interstitial predators, kalyptorhynchs feed on other
micrometazoa. Prey capture is a function of their terminal
proboscis, an anterior, eversible muscular bulb that is
anatomically separate from their mouth and pharynx but
serves to hold and immobilize prey prior to ingestion. The
structure of the proboscis has systematic value and can be
used to di?erentiate between the two major clades of
Kalyptorhynchia: Eukalyptorhynchia Meixner, 1928 and
Schizorhynchia Meixner, 1928. In the eukalyptorhynchs,
the muscular proboscis is a single cone-like organ, while
in the schizorhynchs, the proboscis is dorsoventrally split
into two equal halves or lips. In both groups, the proboscis
may be naked (i.e. without any noticeable structures) or
bear various papillae or hooks. Within the Eukalyptor-
hynchia, sclerotic elaborations such as proboscis hooks are
produced as intracellular specializations within the
proboscis epithelium, whereas in Schizorhynchia, sclerotic
hooks are derivatives of the basal lamina (Rieger & Doe,
1975; Doe, 1976). In the eukalyptorhynch taxon,
Gnathorhynchidae, the proboscis hooks come in a variety
of shapes and sizes, but are generally present as spine-like
teeth protruding from a single basal plate.The structure of
the hooks is likely to re?ect di?erent prey specializations.
At the taxonomic level, proboscis hooks are diagnostic of
certain genera and species, and along with characters of
the reproductive system, have been used to distinguish the
currently recognized 11 genera and greater than 30 species
within the family (Tyler & Bush, 2003). In this study, a
new genus of Gnathorhynchidae is described from a tidal
?at in Mosquito Lagoon and from dredged sediment in
the Indian River Lagoon, Florida.
MATERIALS AND METHODS
Kalyptorhynchs were collected from 0.5m depth in
Mosquito Lagoon, eastern Florida (288520N 808500W) on
19 February, 2004. Sediment samples were collected by
hand and placed into small containers. An additional
specimen was found by dredge collection at 2.9m depth
at the 500 mid-channel range marker of Fort Pierce Inlet
(27828.120N 80819.130W) in the Indian River Lagoon,
Florida on 10 March, 2004. Animals were extracted from
the sediment using magnesium chloride isotonic to
seawater. All animals were initially observed alive as
wholemounts prior to histological and ?uorescent analysis.
For comparison, specimens of Drepanorhynchides hastatus
were collected from Fort Meyers beach in western Florida
on the Gulf of Mexico (268270N 82800W).
Specimens were processed for histology using the
following protocol: ?x in 2.5% glutaraldehyde in 0.1M
phosphate-bu?ered sodium (PBS) for 24 h, rinse in PBS
for 1h, post?x in 1% OsO4 in 0.1M PBS for 1h, rinse 1h
in PBS, dehydrate in standard ethanol series, transfer
through propylene oxide to a mixture of Epon^Araldite.
Resin blocks were sectioned at 1.5 microns using glass
knives, a?xed to glass slides, and contrasted with
Richardson?s stain at 608C.
The structure of the proboscis and positions of muscular
reproductive organs were determined by whole-mount
muscle staining with Alexa Fluor 488 phalloidin
J. Mar. Biol. Ass. U.K. (2004), 84, 1143^1149
Printed in the United Kingdom
Journal of the Marine Biological Association of the United Kingdom (2004)
(Molecular Probes, Eugene, OR, USA). Kalyptorhynchs
were ?rst relaxed for 10min in 7.5% magnesium chloride
solution prior to ?xation in 5% formaldehyde in 0.1M
PBS (1h). Kalyptorhynchs were next rinsed in 0.1M PBS
for 1h, permeabilized for 1h in 0.2% Triton X-100 in PBS,
stained 1h with Alexa Fluor 488 phalloidin and rinsed in
PBS before mounting with Gel/Mount (Biomeda Corp.).
Specimens were examined using a CLSM on a Nikon
Eclipse E800 compound microscope equipped with a
Biorad Radiance 2000 laser system. Series of 0.05 mm
optical z-projections were made using Confocal Assistant
version 4.02.
Type and voucher specimens of all examined species are
deposited in the National Museum of Natural History,
Smithsonian Institution.
SYSTEMATICS
KALYPTORHYNCHIA Gra?, 1905
EUKALYPTORHYNCHIA Meixner, 1928
GNATHORHYNCHIDAE Meixner, 1929
Genus Smithsoniarhynches gen. nov.
Type species
Smithsoniarhynches sherryreedae sp. nov.
Etymology
The generic name is constructed from Smithsonia, a
dedication to the research sta? at the Smithsonian
Marine Station at Fort Pierce, combined with the Greek
su?x rhynches (rhynchus?snout), used in reference to the
everscible proboscis. The gender is feminine.
Description
Gnathorhynchidae with paired proboscis hooks
consisting of ten individual spine-like teeth protruding
from a single basal plate with lateral ?anges. Anterior tegu-
mentary retractors and four pairs of proboscis retractors
present. Paired pigmented eyespots. Pharynx rosulatus at
approximately 60%body length. No adhesive girdles.
Male reproductive system consists of an unpaired, ante-
rior testis and single large seminal vesicle in posterior body
region. Seminal vesicle lined with longitudinal muscles
only. Muscular copulatory bulb containing prostatic fasci-
cles and surrounded by two muscle coats, inner circular
muscles and outer spiral muscles. A muscular ductus
ejaculatorius proceeds axially through the copulatory
bulb. A funnel-shaped sclerotic stylet is present. Genital
pore is ventral and subterminal. Female system consists of
a muscular female genital canal (ductus uterocommunis)
that gives rise to a short uterus and elongate bursa semi-
nalis. Uterus and bursa are lined with longitudinal
muscles. Unpaired vitellarium and ovary present.
Smithsoniarhynches sherryreedae sp. nov.
Figures 1^6
Material examined
Twelve specimens examined in total from Mosquito
Lagoon, FL (288520N 808500W): six specimens examined
alive as wholemounts, four specimens examined as ?uores-
cent wholemounts stained for F-actin, and two specimens
sectioned. One live specimen examined from Fort Pierce
Inlet in the Indian River Lagoon, FL (27828.120N
80819.130W). Holotype is a wholemount mature specimen
from Mosquito Lagoon, mounted in resin on a glass slide
(USNM1026575). Two paratypes are mature wholemount
specimens in resin on glass slides; one from Mosquito
Lagoon (USNM 1026575) and one from Indian River
Lagoon (USNM 1026577). A fourth paratype of a
Mosquito Lagoon specimen is sectioned parasagittally
(USNM1026578).
Etymology
The speci?c epithet, sherryreedae, is dedicated to Sherry
Reed, Research Assistant at the Smithsonian Marine
Station at Fort Pierce, for her gracious assistance in
collecting the specimens. The gender is feminine.
Description
Specimens are translucent, slender in outline and range
from 700 mm to 960 mm long and 95 mm to 130 mmwide. A
pair of large, pigmented eyes, to 10 mm long, is positioned
approximately 200 mm from the tip of the head (Figure
1A). Pharynx rosulatus is positioned at approximately 60
1144 R. Hochberg A new genus of Gnathorhynchidae
Journal of the Marine Biological Association of the United Kingdom (2004)
Figure 1. Smithsoniarhynches sherryreedae sp. nov., holotype. (A)
General organization; (B) copulatory hook; (C) copulatory
stylet. bs, bursa seminalis; cb, copulatory bulb; duc, ductus
uterocommunis; ey, eyes; gp, common gonopore; gt, gut; ov,
ovary; ph, pharynx; phg, pharyngeal glands; pg, proboscis
glands; pr, proboscis; sv, seminal vesicle; ut, uterus; vt, vitel-
larium. Scale bars: A, 250 mm; B, 12 mm; C, 60 mm.
per cent body length and up to 75 mm in diameter. Several
pharyngeal glands are present.The body wall epidermis is
completely ciliated and up to 3 mm high. Cilia are 4^6 mm
long. No adhesive girdles are present.
The terminal proboscis cavity, lined with thin circular
and longitudinal muscles, is up to 65 mm long and leads
posteriorly to an unsplit proboscis (Figure 2E). The
proboscis is up to 65 mm long and consists of a terminal
apex and sclerotic hooks on paired muscular cones
(?Muskelwu? lste of Meixner? (1929)). The apex and central
region of the proboscis consists of longitudinal muscles,
some as cone retractors and some as cone protractors
(Figure 2F). Longitudinal muscles of the proboscis cavity
insert on the proboscis cone musculature. Tegumentary
retractors are present. On either side of the terminal apex
are circular muscle cells that appear as distinct columns
(?bourrelets musculaires de la trompe? of L?Hardy (1966)).
At the anterior end of each column is a single sclerotic
hook. Each hook consists of a basal plate with lateral
?anges and ten individual teeth (Figure 2A^D). In the
holotype, the plate is 11mm long and 15 mm wide, with
lateral ?anges to 8 mm long, and an 8 mm wide base that
contacts the proboscis column (Figure 2A,C,D). Ten teeth
protrude from the basal plate. The teeth are present in
three sizes with the largest three teeth positioned termin-
ally; the central tooth is 4.5 mm long and ?anked by a
tooth on either side to 3.5 mm long. Seven smaller teeth,
all approximately 2 mm long, are positioned more
centrally on the plate body, with two bilateral groups of
three teeth surrounding a single tooth. Four pairs of long-
itudinal retractor muscles attach to the base of the
proboscis (Figure 2E,F). Three to ?ve proboscis glands,
approximately 30 mm to 40 mm long, are present at the
base of the proboscis.
The reproductive system consists of a ventral, subterm-
inal common gonopore that leads into a muscular genital
atrium (Figures 3 & 4B). The female reproductive system
A new genus of Gnathorhynchidae R. Hochberg 1145
Journal of the Marine Biological Association of the United Kingdom (2004)
Figure 2. Smithsoniarhynches sherryreedae sp. nov. (A) Proboscis
of holotype; (B) proboscis of paratype; (C) proboscis hooks of
holotype, terminal spines in focus; (D) proboscis hooks of holo-
type, subterminal spines in focus; (E) z-projection of f-actin
stained specimen, anterior end; (F) z-projection of f-actin
stained specimen, close-up of proboscis musculature. pa, term-
inal apex of proboscis; pc, proboscis cavity; pr, proboscis
retractor muscles. Scale bars: A,B, 25 mm; C,D, 5 mm; E,
40 mm; F, 15 mm.
Figure 3. Smithsoniarhynches sherryreedae sp. nov., schematic of posterior reproductive organs observed in lateral view. bo, bursal
organ tissue; bs, muscular bursa seminalis; cb, copulatory bulb; duc, ductus uterocommunis; ga, genital atrium; gp, common
gonopore; ov, ovary; ovd, ovovitelline duct; st, copulatory stylet; sv, seminal vesicle; ug, uterine glands; ut, uterus; vd, vas deferens;
vt, vitellarium.
branches o? the base of the atrium as a long female genital
canal (ductus utero-communis sensu Den Hartog 1968), is
75 mm to 100 mm long, and leads anteriorly to an uterus
and bursa seminalis (Figure 3). Both uterus and bursa
seminalis are lined with longitudinal muscles (Figure
4A,B). The uterus is a small bag-like structure approxi-
mately 18 mm long and demarcated from the female
genital canal by ?ve to six sphincter muscles (Figure 4B).
No eggs were present in the uterus of any examined indi-
viduals. Several glands emanate from the base of the
uterus and extend anteriorly (Figures 1A, 3 & 6C). A
bursa seminalis branches o? the ductus uterocommunis
just prior to the uterine sphincters. A single sphincter is
present at its base. The bursa is an expansive organ that
consists of weakly staining bursal tissue surrounding a
muscular extension of the bursal canal (bursa seminalis
sensu stricto) (Figure 4A,C). The bursa seminalis is a
loosely de?ned muscular bag lined with thin longitudinal
muscles and containing sperm (Figure 4A); sperm were
present within the bursal tissue outside of the bursa semi-
nalis. A pair of concentric sphincter muscles is present on
the lateral side of the bursa seminalis where it approaches
the ovovitelline duct (Figure 4A). These muscles were not
located in histological sections, but based on location, they
appear to demarcate the bursa seminalis from the ovovi-
telline duct; a short non-muscular canal probably connects
the bursa to the ovovitelline duct. Anteriorly, the ovovitel-
line duct leads to a short ovary and elongate vitellarium,
and posteriorly to the genital canal.
The male reproductive system consists of a single, ante-
rior testis that often appears as a pair of testis follicles
because of a slight median constriction (Figure 1A). A vas
deferens leads posteriorly to an ovoid seminal vesicle,
50 mm to 83 mm in diameter, lined with longitudinal
muscles only (Figure 5A). In section, the seminal vesicle
was ?lled with sperm. From the base of the seminal
vesicle is a single, muscular spermatic duct that connects
to the male copulatory bulb.The copulatory bulb is 58 mm
to 73 mm long and 28 mm to 43 mm wide. The bulb is
wrapped in an outer coat of crossed spiral muscles that
are continuous with most of the genital atrium (Figure
5B,C). Inside the spiral muscle coat is a layer of circular
muscles that encloses only the bulb itself. Together, both
layers of muscle are approximately 7^9 mm thick. The
copulatory bulb is thick-walled and ?lled with compact
spherical tissue (1^2 mm diameter) that stains regularly
but poorly (Figure 5C). In some longitudinal sections, the
tissue appears to be divided, indicating fascicles (Figure
5D). A straight canal, the ductus ejaculatorius, penetrates
the copulatory bulb and connects the spermatic duct to the
proximal opening of the copulatory stylet (Figure 5B,C).
1146 R. Hochberg A new genus of Gnathorhynchidae
Journal of the Marine Biological Association of the United Kingdom (2004)
Figure 4. Smithsoniarhynches sherryreedae sp. nov., female
reproductive system. (A) Z-projection of female reproductive
system; (B) z-projection of uterus and sphincter muscles; (C)
longitudinal section of bursal organ. bo, bursal organ tissue; bs,
muscular bursa seminalis; cs, concentric sphincter muscles of
bursal organ.
Figure 5. Smithsoniarhynches sherryreedae sp. nov., views of
male reproductive system. (A) Z-projection of region
around seminal vesicle; (B) z-projection of copulatory bulb;
(C) longitudinal section of copulatory bulb; (D) longitudinal
section of penis papilla projecting into the copulatory stylet.
cb, copulatory bulb; cm, inner circular muscle layer of copula-
tory bulb; ed, ejactulatory duct; ga, genital atrium; gp, genital
pore; pp, penis papilla; spm, spiral muscle coat; sv, seminal
vesicle; ut, uterus; arrow heads, walls of sclerotic stylet. Scale
bars: A, 25 mm; B, 20 mm; C, 10 mm; D, 5 mm.
Approximately ten longitudinal muscle ?bres are present
within the canal (Figure 5B). The canal is wide at the
proximal end of the bulb, narrows at its centre, and
widens again as it approaches the distal end of the bulb
where a penis papilla projects into the proximal aperture
of a sclerotic stylet (Figure 5D). The stylet is funnel-
shaped, to 60 mm long, has a gradual dorsal^ventral
curvature, and a proximal opening of 15 mm to 22 mm
wide that tapers to 1mm at its distal tip (Figures 1C &
6A^C). Prostatic secretions, presumably originating from
the walls of the copulatory bulb, are present within the
proximal opening of the stylet of one individual. There
are no prostatic glands outside of the copulatory bulb.
Ecology
Twelve specimens of the new species were collected from
a tidal ?at in Mosquito Lagoon. The sediment was mixed
with coarse and ?ne sand grains covered with a layer of
silt. Fauna included: Oligochaeta and Polychaeta (Anne-
lida), Copepoda and Ostracoda (Arthropoda), Macrodasys
sp. and Urodasys sp. (Gastrotricha), Acoela, Macrostomida
and Proseriata (Platyhelminthes), and Nematoda.Various
molluscan and crustacean larvae were also present. A
single specimen of the new species was collected from
Indian River Lagoon. Sediment was mixed with ?ne silt.
Fauna included: Copepoda and Ostracoda (Arthropoda),
Macrodasys sp. and Tetranchyroderma sp. (Gastrotricha),
Acoela and Proseriata (Platyhelminthes), Nematoda, and
Polychaeta (Annelida).
DISCUSSION
The family Gnathorhynchidae was erected in 1929 by
Meixner to unite species of Eukalyptorhynchia with
sclerotic hooks on their proboscis. Several species of
Schizorhynchia also possess sclerotic hooks, namely
species of Karkinorhynchidae and some species of
Schizorhynchidae, but the ultrastructural origin of hooks in
these species is di?erent from those of Gnathorhynchidae,
at least in the few species that have been examined
A new genus of Gnathorhynchidae R. Hochberg 1147
Journal of the Marine Biological Association of the United Kingdom (2004)
Figure 6. Smithsoniarhynches sherryreedae sp. nov., light micrographs of stylets viewable in mounted type specimens. (A) Focus on
proximal region of stylet in holotype; (B) focus on distal region of stylet in holotype; (C) stylet of paratype. cb, copulatory bulb; ug,
uterine glands. Scale bars: A,B, 30 mm; C, 40 mm.
Figure 7. Drepanorhynchides hastatus from Fort Pierce, FL, USA. (A) Light micrograph of proboscis hooks showing three terminal
spines or teeth; (B) z-projection of f-actin stained specimen, distal portion of copulatory bulb revealing inner circular muscles of
bulb and outer longitudinal muscles; (C) copulatory stylet. cb, copulatory bulb; ut, uterus. Scale bars: A, 10 mm; B, 20 mm; C,
25 mm.
(Rieger & Doe, 1975; Doe, 1976). To date, there are 11
genera and greater than 30 species of gnathorhynchs
known worldwide, though only a few novel species have
been described from North America (Ax & Armonies,
1987, 1990; Karling, 1995; Ax, 1997).
Den Hartog (1968) reviewed the characters of
Gnathorhynchidae with a particular emphasis on the
structure of the proboscis, proboscis hooks and repro-
ductive anatomy, and concluded that considerable
variation in characters (e.g. organ topology, hook struc-
ture) made it di?cult to establish generic relationships,
though individual genera are easily de?ned taxonomically.
The new genus, Smithsoniarhynches, is distinguished from
other gnathorhynchs primarily by the structure of the
proboscis hooks. As opposed to the sclerotic hooks of
other species, where a single or occasionally two to three
spines (e.g. Orbiculorhynchus luebbeni Noldt, 1989) emerge
from a basal plate, the hooks of S. sherryreedae sp. nov.
bear ten individual spines that originate separately from
the basal plate. The three terminal spines are arranged in
a similar fashion to those of Orbiculorhynchus luebbeni and
might in fact represent the plesiomorphic, multispined
condition; three terminal spines are a common condition
in species of Drepanorhynchides (see Figure 7A),
Odontorhynchus, and Prognathorhynchus. However, the
straight, thin shape of the spines di?erentiates those of
Smithsoniarhynches gen. nov. from the more broad, curved
appearance of most sclerotic teeth in other species. Addi-
tional di?erences exist in the structure of the basal plate.
The plate appears ?at in several wholemount specimens,
but is distinctly arched in live animals, similar to the
condition in Psittacorhynchus verweyi Den Hartog, 1968.
The plate is also rounded-square in shape, with lateral
?anges di?erent from the lateral outgrowths of the basal
plate in other species.
Four pairs of proboscis retractors arise o? the plate-like
muscular pads (?Muskelwu? lste?) of Smithsoniarhynches
gen. nov., a condition present in most other genera
including Ancistrorhynchus, Odontorhynchus, Orbiculorhynchus,
Neognathorhynchus, Prognathorhynchus and Uncinorhynchus.
Tegumentary retractors are also present in most of the
these species with the exception of Ancistrorhynchus.
Den Hartog (1968) distinguished three general posi-
tions of the pharynx within the body of species of
Gnathorhynchidae: anterior, middle and posterior. While
the position of the pharynx is recognized to vary with
body length, it is in general a good diagnostic character,
and aligns Smithsoniarhynches gen. nov. more closely to
species of Neognathorhynchus than perhaps any other genus.
The structure of the gnathorhynch reproductive system
is relatively constant throughout the family though there is
some variation in the structure and general topology of
certain organ systems. Concerning the male reproductive
system, Smithsoniarhynches gen. nov. possesses an anterior
testis, similar to the condition in species of Ancistrorhynchus
and Drepanorhynchides; however, as pointed out by Den
Hartog (1968), many of these and others species of
Gnathorynchus, Uncinorhynchus, and Psittacorhynchus possess a
highly elongate testis that extends from in front of to well
beyond the length of the pharynx. Posteriorly, a single vas
deferens generally leads to a seminal vesicle (?spermaducal
vesicle? of Den Hartog) lined with longitudinal muscles; a
seminal vesicle is absent in Psittacorhynchus. The seminal
vesicle of Smithsoniarhynches gen. nov. is large and oval,
quite di?erent in appearance from the more general
elongate seminal vesicle present in most other species.
The structure of the copulatory bulb (?granular bulbus?
of Den Hartog) displays some variation throughout the
Gnathorhynchidae, in both histological organization and
its surrounding musculature. Smithsoniarhynches gen. nov. is
characterized by a copulatory bulb with an outer coat of
spiral muscles that extends from the genital atrium, an
inner layer of ?ne circular muscles restricted to the bulb
itself, and an axial ejactulatory duct lined with longitu-
dinal muscles. Interestingly, there do not appear to be any
external prostatic glands, but the walls of the bulb may be
divided into prostatic fascicles (see Figure 5D). Taken
together, this condition appears unique within the family.
A muscular coat of outer orthogonal muscles is character-
istic of many species, while some species such as
Drepanorhynchides hastatus (Meixner, 1929) appear to lack
circular muscles in the outer layer (though present in the
genital atrium, see Figure 7B); spiral muscle coats are also
variously known throughout the family, most recently
observed in Oribiculorhynchus lubbeni by Noldt (1989).
Running axially through the copulatory bulb is an ejacu-
latory duct lined with longitudinal muscles. In several
gnathorhynchs, the ejaculatory duct is lined with ortho-
gonal musculature or no musculature at all, and the condi-
tion of many species remains undetermined, so the
polarity of this character also remains unknown.
External prostatic glands that supply secretions to the
copulatory bulb and stylet are well known from several
species of Gnathorhynchidae, so it is surprising that
similar glands were not present in Smithsoniarhynches gen.
nov. In most gnathorhynchs, and other kalyptorhynchs,
prostatic tissue is generally present as external prostatic
glands and/or internal prostatic fascicles. In S. sherryreedae
sp. nov., prostatic tissue appears to be restricted to internal
longitudinal fascicles, though this was not evident in all
sectioned material. Secretions were only observed in the
stylet of a single live specimen and these were not charac-
terized. Regarding the stylet, its funnel shape is not unique
in the family, but similar in structure to species of
Drepanorhynchides (Figure 7C) and Neognathorhynchus.
The female reproductive system of Smithsoniarhynches
gen. nov. is characteristic of the Gnathorhynchidae, with
an unpaired vitellarium, ovary, and uterus. In many
gnathorhynchs including the new genus, a ductus utero-
communis (female genital canal) also exists, connecting
the genital atrium to the uterus and ovovitelline duct.
This duct is present in species with a bursa seminalis such
as Odontorhynchus aculeatus and species without a bursa such
as Prognathorhynchus dubius Meixner, 1929. Den Hartog
(1968) correctly points out that this character is somewhat
variable in distribution, but in general, the ductus utero-
communis is absent from species that lack a bursa
seminalis. In Smithsoniarhynches gen. nov., the ductus
uterocommunis presumably connects indirectly to the
bursa seminalis by way of a short canal. The canal is
cordoned o? from the bursa seminalis by a pair of
concentric sphincter muscles on the lateral wall of the
bursa.These sphincters may function to control movement
of allosperm into the ductus uterocommunis.
Despite a growing knowledge of anatomical characters
on gnathorhynchs worldwide, phylogenetic relationships
1148 R. Hochberg A new genus of Gnathorhynchidae
Journal of the Marine Biological Association of the United Kingdom (2004)
within the family remain unknown, hindering attempts to
de?ne the systematic position of novel species such as
Smithsoniarhynches sherryreedae. Schockaert (1977) warns
that the use of reproductive characters alone to determine
phylogenetic relationships may give erroneous results
because of convergence in stylet and glandular structures,
at least for the Polycystididae. A similar warning may be
warranted for the Gnathorhynchidae until such time that
homology of these characters, and characters of the
proboscis, are evaluated in greater detail (e.g. ultrastruc-
ture).
I gratefully acknowledge Dr Scott Santagata for his assistance
with the confocal laser scanning microscope and ultramicrotome.
I also thank the sta? of the Smithsonian Marine Station for their
assistance with various aspects of this research.This research was
supported by the Sumner Gerard Foundation through a post-
doctoral fellowship to the Smithsonian Marine Station at Fort
Pierce, Florida. This is Smithsonian Marine Station at Fort
Pierce contribution no. 595.
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Submitted 15 March 2004. Accepted 14 September 2004.
A new genus of Gnathorhynchidae R. Hochberg 1149
Journal of the Marine Biological Association of the United Kingdom (2004)