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A new genus and three new species of freshwater
cochliopids (Caenogastropoda) from Goiás, Brazil
Un nuevo género y tres nuevas especies de cochliópidos de agua dulce
(Caenogastropoda) de Goiás, Brasil
Luiz Ricardo L SIMONE* & Emilio ROLÁN**
Recibido el 1-IV-2020. Aceptado el 4-VII-2020
ABSTRACT
Three new species of Cochliopidae collected in a warm spring in Central Brazil in Cha-
pada dos Veadeiros, Goiás, are described, based on conchological and anatomical fea-
tures. One of them belong to the new genus Atomicus, characterized by the minute size
(less than 1 mm), discoid shell, and other anatomical features; the type species is A.
inopinatus n. sp. The other two species belong to the genus Heleobia: H. apua and H.
pukua. All new species are so far only found in the type locality. The conchological,
anatomical exclusivities and differences are explored under the context of other Brazilian
and South American rissooideans/truncatelloideans.
RESUMEN
Se describen tres nuevas especies de Cochliopidae recolectadas en una fuente cálida en el
centro de Brasil, en Chapada dos Veadeiros, Goiás, con base en sus características anató-
micas y conquiliológicas. Una de ellos pertenece al nuevo género Atomicus, caracterizado
por su diminuto tamaño (menos de 1 mm), concha discoidal y otras características anató-
micas; la especie tipo es A. inopinatus n. sp. Las otras dos especies pertenecen al género
Heleobia: H. apua y H. pukua. Hasta ahora, todas las especies nuevas solo se encontraron
en la localidad tipo. Las exclusividades y diferencias conquiliológicas, anatómicas se explo-
ran en el contexto de otros rissooideos / truncatelloideos brasileños y sudamericanos.
urn:lsid:zoobank.org:pub:A191152E-4F3C-458B-91C8-9FB1A4FC6376
KEY WORDS: Brazil, fresh water gasteropoda, Cochliopidae, Atomicus new genus, genus Heleobia, new species.
PALABRAS CLAVE: Brasil, gasterópodos de agua dulce, Cochliopidae, Atomicus nuevo género, género Heleo-
bia, nuevas especies.
INTRODUCTION
The non-marine truncatelloideans
from the Brazilian territory are a con-
stant source of new discoveries. Possibly
due to their low dispersion capacity and
minute size, a high degree of endemicity
is the rule (S
IMONE
, 2006b). In a recent
* Museu de Zoologia da Universidade de São Paulo. Cx. Postal 42494; 04218-970, São Paulo, SP; Brazil. lrsi-
mone@usp.br; lrlsimone@gmail.com. OrcID: 0000-0002-1397-9823
** Museo de Historia Natural, Campus Universitario Norte, Parque Vista Alegre, 15782 Santiago de
Compostela, Spain; emiliorolan@gmail.com
© Sociedad Española de Malacología Iberus, 39 (1): , 2021
1
trip of the second author, some species
of tiny freshwater snails were collected
in a thermal spring in Goiás, central
Brazil area (Figs. 2-3). This region
belongs to the Cerrado biome, and is
somewhat equidistant from Amazon
Rainforest (north), Pantanal (the larger
floodable area in the world – west), and
Caatinga (semiarid environment – east).
The collect region belongs to the
Araguaia-Tocantins rivers basin, a pair
of rivers which are the east extreme of
the Amazon basin. Tocantins River
mouth is together joint with that of
Amazon river, almost directly into the
Atlantic Ocean. The region is very
understudied, and source of several
novelties, as those presently introduced.
The collect area is also close to the
Chapada dos Veadeiros, a protected
National Park with almost no malaco-
logical approach.
The Truncatelloidea encompass 27
families (W
O
RMS, 2020), occurring in all
non-glacial regions, and in almost all
biomes (S
IMONE
, 2006b). The family
Cochliopidae includes 59 valid genera
(W
O
RMS, 2020), but only three of them
occur in South America (Simone, 2006a).
The family is mostly defined molecu-
larly (K
OCH ET AL
., 2015), and has a
somewhat obscure morphological defin-
ition (Hershler, person. obs.), therefore,
anatomical information is always
important to be included. The detailed
study of the morpho-anatomy of the
samples collected in the above men-
tioned locality revealed three new enti-
ties, being two belonging to the complex
genus Heleobia Stimpson, 1865 (type
species Paludina culminea d’Orbigny,
1838, subsequent designation by Pilsbry,
1911) (H
ERSHLER
& T
HOMPSON
, 1992;
K
ABAT
& H
ERSHLER
, 1993; K
OCH ET AL
,
2015), and the third belonging to a new
genus. All taxa belong to the family
Cochliopidae, subfamily Semisalsinae
(K
OCH ET AL
., 2015).
With the continental Brazilian mala-
cofauna inventoried (S
IMONE
, 2006a;
B
IRCKOLZ ET AL
., 2016), including extra-
Andean regions for the freshwater
fauna, the detection of new taxa became
relatively easy. The present paper is
intended to provide a formal descrip-
tion for the three new species from
Tocantins basin, in order to, based at
least on their endemicity, provide a sci-
entific basis for the protection of that
environment and these species.
MATERIAL AND METHODS
The specimens were hand collected
after their visualization on the sediment
(Fig. 1) and also by examining sediment
samples under the stereomicroscope.
They were conserved in 70% ETOH
unanesthetized, and were studied by
standard techniques (S
IMONE
, 2011),
with the specimens dissected immersed
in alcohol. The specimens were ex-
tracted from their shells by crushing the
shell, all dissection steps were pho-
tographed and some structures were
Iberus, 39 (1), 2021
2
Figures 1-3. Type locality images in Colinas do Sul, Chapada dos Veadeiros, Goiás, Brazil,
14°13’19.41”S 47°55’05.01”W, three views at the time of collecting.
Figuras 1-3. Imágenes de la localidad tipo en Colinas do Sul, Chapada dos Veadeiros, Goiás, Brasil, 14°
13’19.41”S 47° 55’05.01” W, tres vistas en el momento del muestreo.
123
processed for histological serial sections.
All drawings were made with the aid of
a camera lucida, the drawing pooling
the average data of several specimens.
Anatomical abbreviations in the
figures and in type lists:
aa, anterior aorta; af, afferent gill vessel;
ag, albumen gland; an, anus; at, female
atrium; au, auricle; bg, buccal ganglion;
bm, buccal mass; br, subradular mem-
brane; ce, cerebral ganglion; cg, capsule
gland; cm columellar muscle; cv, cteni-
dial vein; dc, dorsal chamber of buccal
cavity; dd, duct to digestive gland; df,
dorsal folds of buccal mass; dg, digestive
gland; di, diaphragmatic septum; ef,
esophageal folds; es, esophagus; ey, eye;
fe, fecal pellets; fp, female pore; fs, foot sole;
ft, foot; gi, gill; go, gonad; hg, hypo-
branchial gland; ig, ingesting gland; in,
intestine; jw, jaws; ki, kidney; m2-m10,
odontophore muscles; mb, mantle border;
mc, buccal circular muscle; mj, jaw and
peribuccal muscles; mo, mouth; mt,
mantle; oc, odontophore cartilage; od,
odontophore; op, opercular pad; os,
osphradium; ot, oral tube; ov, pallial
oviduct; oy, ovary; pc, pericardium; pd,
penis duct; pe, penis; pg, anterior furrow
of pedal glands; pl, pleural ganglion; pn,
pedal ganglion; pt, prostate; ra, radula;
rm, snout ventral retractor muscle; rn,
radular nucleus; rs, radular sac; rt, rectum;
sa, salivary gland aperture; sc, subradular
cartilage; se, septum between esophageal
origin and odontophore; sd, salivary duct;
sg, salivary gland; sh, shell(s); sn, snout;
spm, specimen(s); ss, style sac; st, stomach;
su, subesophageal ganglion; sv, seminal
vesicle; sy, statocyst; te, cephalic tentacle;
tg, integument; ts, testis; ve, ventricle; vd,
vas deferens, vo, visceral oviduct.
Abbreviation in listed material:
sh, shell(s); spm, specimen(s).
Institutional abbreviations:
MHNS: Museo de Historia Natural,
Santiago de Compostela, Spain; MNCN:
Museo Nacional de Ciencias Naturales,
Madrid, Spain; MNHN: Muséum natio-
nal d’Histoire naturelle, Paris, France;
MNRJ: Museu Nacional de Rio de
Janeiro; MZSP: Museu de Zoologia da
Universidade de São Paulo, São Paulo,
Brazil; NHMUK: National History
Museum United Kingdom, London.
S
IMONE
& R
OLÁN
: New genus and species of freshwater cochliopids from Goiás, Brazil
3
SYSTEMATICS
Family C
OCHLIOPIDAE
Subfamily S
EMISALSINAE
Genus Atomicus new genus
urn:lsid:zoobank.org:act:BDF23509-C2A9-4D67-AE70-A25C49AA28CA
Type species: Atomicus inopinatus n. sp.
Etymology: The generic name is derived from the Greek tomikos, meaning cutting, precedes by
prefix “a”, a negative. The term means “not divisible”, an allusion to the minute size.
Diagnosis: Shell discoid to turbini-
form, umbilicus wide; minute (~1 mm).
Peristome and operculum rounded.
Peristome preceded by region detached
from spire. Snout small; head-foot short,
columellar muscle with both ends ele-
vated. Gill wanting, but osphradium
present. Radular teeth with multicuspid
cutting edge. Odontophore with m5
muscle pair originated from cartilage.
Stomach posteriorly bilobed, style sac
short. Intestine zigzagged both in vis-
ceral and pallial regions. Penis simple,
lacking appendices, glands and papillae,
relatively short; pallial vas deferens
originated from anterior prostate end.
Pallial oviduct with ingesting gland
along terminal end of visceral oviduct;
seminal receptacle multilobed.
List of included species: monotypic so far.
Iberus, 39 (1), 2021
4
Description: Shell (Figs. 4-9, 11-14, 16,
17): Very small (up to 1 mm), discoid,
almost planispiral; height/width ratio
0.7. General colour yellowish to pale
beige (Figs. 6-9), translucent; some spec-
imens (~30%) with additional brown
coating, possibly sediment (Figs. 4-5).
Spire scarcely elevate, ~30% of total
height; of ~2.25 whorls (Figs. 5-7, 13-14).
Protoconch (Figs. 9, 11, 16) almost one
whorl, diameter of ~260 µm, nucleus of
~70 µm; surface smooth, not shiny (Figs.
16, 17). Teleoconch ~1.5 whorls, smooth,
no sculpture except for prosocline
growth lines (Figs. 11-14); region pre-
ceding aperture slightly detached from
spire (Figs. 5, 7, 13, 14). Suture well
marked, relatively deep (Figs. 16, 17).
Aperture rounded (Figs. 5, 6, 13, 14),
slightly prosocline (~20° with vertical
axis) (Figs, 7, 8, 14), ~35% of total width,
~65% of total height; peristome continu-
ous, very fine, with little contact or no
contact with the previous whorl, nor-
mally clearly separate (Figs. 5, 6, 13, 14).
Umbilicus wide, occupying ~25% of
inferior area (Figs. 6, 8, 12).
Head-foot (Figs. 19, 22, 24): Rela-
tively small, stubby, unpigmented. Foot
thick, as wide as shell aperture, 1/4-1/2
larger than head. Eyes (ey) dark, located
in the base of tentacles. Mesopodium (ft)
thick, short, flanked dorsally by shallow
lateral furrows. Anterior furrow of
pedal glands (pg) deep, relatively short,
restricted to anterior edge. Opercular
pad elliptic, terminal, occupying most of
posterior foot dorsal surface. Pair of
cephalic tentacles laterally positioned
(te), each tentacle simple, thick, rather
cylindrical ~same length as foot. Snout
from ~80% (fig 19) to ~60% (Fig. 22) ten-
tacles length (sn), ~twice tentacles’
width; anterior end bilobed; mouth as
transverse slit, ventral, central (mo).
Columellar muscle (cm) thick, wide,
~3/4 whorl; right and left ends more
elevated than medial region, right end
~twice as tall as left end. Haemocoel
elliptical, on central region of head-foot
(Fig. 24).
Operculum (Figs. 10, 15): Corneous,
thin, translucent, yellow-beige, flexible,
paucispiral. Outline elliptical-almost
circular, occupying entire shell aperture
(Fig. 6). Edges thin. Nucleus located in
middle region of interior half, slightly
displaced towards the inner side; from
nucleus series of undulations corre-
spondent to inner-superior growth
edge. Inner surface glossy, scar
rounded, occupying ~half of inner sur-
face, located closer to internal edge, but
not touching it.
Mantle organs (Figs. 23, 27): Some-
what wide, ~1 whorl in length. Mantle
edge (mb) simple, thick; unpigmented.
Osphradium short (os), softly curved
(concavity left), simple; length ~10%
pallial cavity length; located in anterior-
left corner of cavity, close to mantle
border. Gill wanting. Hypobranchial
Atomicus inopinatus n. sp. (Figures 4-27)
urn:lsid:zoobank.org:act:3BF9C5E2-274F-4275-A71D-329A6C7DD507
Type material. Holotype: BRAZIL • 1 spm (Figs. 4-5); Goiás, Chapada dos Veadeiros, Colinas do
Sul; 14°13’19.41”S 47°55’05.01”W; E. Rolán leg.; in a hot spring with a small river; MZSP 151666.
Paratypes: BRAZIL • 30 spm; same data as for holotype; MZSP 97859 • 1 spm (Figs. 6-9); same data
as for holotype; MZSP 151667 • 12 sh; same data as for holotype; MZSP 144658 • 1 sh (Fig. 11);
same data as for holotype; MZSP 144656 • 1 sh (Fig. 12); same data as for holotype; MZSP 144662
• 1 sh (Fig. 13); same data as for holotype; MZSP 144657 • 1 sh (Fig. 14); same data as for holotype;
MZSP 114654 • 2 spm; same data as for holotype; MNRJ • 2 spm; same data as for holotype; MNCN
• 2 spm; same data as for holotype; MHNS • 2 spm; same data as for holotype; NHMUK.
Type locality: BRAZIL, Goiás, Chapada dos Veadeiros, Colinas do Sul, 14°13’19.41”S 47°55’05.01”W,
in a hot spring with a small river.
Etymology: The specific name is from the Latin “inopinata”, “not expected” alluding that this species
was found several weeks after the collecting, in the sediments, having been overlooked because by
its small size in the first examination in situ.
S
IMONE
& R
OLÁN
: New genus and species of freshwater cochliopids from Goiás, Brazil
5
Figures 4-18. Atomicus inopinatus anatomical features. 4, 5: holotype MZSP 151666, apical and
frontal views (W 0.98 mm); 6: paratype MZSP 151667, frontal view (W 0.98 mm); 7: same, left
view; 8: same, umbilical view; 9: same, apical view; 10: operculum, direct illumination, outer view
(W 0.28 mm); 11: paratype MZSP 144656, SEM, apical view (W 0.98 mm); 12: paratype MZSP
144662, SEM, umbilical view (W 0.98 mm); 13, 14: paratypes MZSP 144657, 144654 resp.,
SEM, frontal-slightly right views (W 0.81, 1.00 mm); 15: operculum, SEM, outer view (W 0.29
mm). 16: detail of apex, apical view; 17: same, detail of sculpture; 18: radula, SEM, general view.
Figuras 4-18. Características anatómicas de Atomicus inopinatus. 4, 5: holotipo MZSP 151666,
vistas apical y frontal (W 0,98 mm); 6: paratipo MZSP 151667, vista frontal (ancho 0,98 mm); 7: el
mismo, vista izquierda; 8: el mismo, vista umbilical; 9: el mismo, vista apical; 10: opérculo, ilumina-
ción directa, vista externa (0,28 mm ancho); 11: paratipo MZSP 144656, MEB, vista apical (ancho
0,98 mm); 12: paratipo MZSP 144662, MEB, vista umbilical (W 0,98 mm); 13, 14: paratipos
MZSP 144657, 144654 resp., MEB, vistas frontales ligeramente desde derecha (W 0,81, 1,00 mm);
15: opérculo, MEB, vista externa (W 0,29 mm); 16: detalle del ápice, MEB, vista apical; 17: mismo
ejemplar, detalle de escultura; 18: rádula, MEB, vista general.
10 µm
20 µm
200 µm
gland inconspicuous. Rectum wide,
with strong zigzagged loop; bearing
aligned series of elliptical fecal pellets
(fe), easily seen by transparency. Anus
simple, sessile (Fig. 27: an) to shortly
siphoned (Fig. 23), located close to
mantle border. Genital structures rela-
tively massive, described below.
4
567
8910 11
12
13 14
15
16 17 18
Visceral mass (Fig. 23): Length ~2.5
whorls. Most structures pale beige to
white in colour. Stomach (st) as anterior
structure, compressing ventrally small
reno-pericardial structures (pc, ki);
stomach of ~0.5 whorl and with almost
entire adjacent whorl width. Digestive
gland (dg) of ~1.5 whorls, mostly poste-
rior and right to stomach. Gonad (oy)
running along columellar surface of
each whorl when mature, weakly dis-
tinct from digestive gland.
Circulatory and excretory systems
(Figs. 23, 27): Pericardium narrow,
located longitudinally between stomach
and pallial cavity (pc), volume ~1/20 of
that of visceral mass; auricle (au) ante-
rior, just posterior to posterior end of
ctenidial vein (cv) detectable running
along left-posterior edge; ventricle (ve)
posterior, simple. Kidney (ki) minute,
slightly smaller than pericardium,
located in right side of pallial cavity
posterior end; inner tissue totally solid,
white. Nephrostome small, transverse,
close to pericardium.
Digestive system (Figs. 20-21, 24, 26-
27): Mouth as slit in antero-ventral end
of snout (Fig. 24: mo). Buccal mass
bulged, occupying entire snout inner
surface and ~1/3 of haemocoelic volume
(Fig. 24: od). Pair of jaw plates (Fig. 20:
jw) somewhat separated from each
other; each jaw oval, thin, translucent.
Odontophore spherical, with ~half of
buccal mass volume (Fig. 20: od). Odon-
tophore muscles (Figs. 20, 26): mj, pair of
jaw and peribuccal muscles, and odon-
tophore protractors, originating in lateral
and ventral region of mouth, running to-
wards posterior as part of oral tube
along ~half odontophore length (Fig. 20),
inserte in latero-ventral mid region of
odontophore cartilages, more distinct in
lateral region; m2, pair of posterior re-
tractor muscles of odontophore (Fig. 20),
narrow, originating in lateral region of
haemocoel inner surface, in its middle
level, running towards anterior distance
equivalent to buccal mass length, in-
serted in postero-lateral region of odon-
tophore; m4, pair of main dorsal tensor
muscle of radula (Fig. 26), broad, thick,
surrounding outer lateral surface of
odontophore cartilages, originating from
their ventro-lateral surface; m5, pair of
secondary dorsal tensor muscles of
radula (Fig. 26), narrow and thick, origi-
nating in posterior edge of odontophore
cartilages, running towards medial and
anterior; m6, horizontal muscle, thin,
wide, connecting ventral edge of both
odontophore cartilages along ~80% of
their length (Fig. 26). Odontophore carti-
lages elliptic, somewhat thick and flat-
tened laterally (Fig. 26: oc). Radular sac
with length ~twice that of odontophore
(Fig. 20: rs); radular nucleus (rn) slightly
broader. Radula (Fig. 18): rachidian occu-
pying ~1/5 of radular width, cutting
edge with more prominent central cusp,
5-7 pairs of secondary cusps gradually
becoming smaller towards lateral; ante-
rior edge strongly concave, ~70% of pos-
terior-basal edge; pair of basal cusps as
long as central cusp, located in middle
region of pair of strong concavities. Lat-
eral teeth as wide as rachidian; ~12
cusps on their cutting-lateral border;
middle cusps larger, with central cusps
larger than that of rachidian. Inner mar-
ginal teeth spoon-like, base narrow ~half
of rachidian; ~33-35 rather uniform
small cusps in lateral-terminal edge.
Outer lateral teeth similar to inner ones,
as long as, but with ~half their width;
cusps preceding both sides of terminal
end; internal edge with 5-6 decreasing
cusps; outer edge with ~ 18 small,
slightly uniform cusps.
Pair of salivary glands small (Fig. 24:
sg), white, with length equivalent to
buccal mass length, ~3 times longer than
wide. Esophagus slightly sinuous (Figs.
20, 24: es), with no detectable glandular
region (Figs. 23, 27). Stomach dimen-
sions and positions above described (vis-
ceral mass); possessing main gastric
chamber posterior, with rather bilobed
posterior surface, each lobe separated by
duct to digestive gland (dd); style sac
marked by gradual narrowing (Figs. 27:
ss), length equivalent to remaining
gastric length. Style sac totally separated
from intestine; esophagus inserted just
ventrally to style sac and intestinal
origins, on middle-ventral stomach side
(Fig. 27); duct to digestive gland as wide
Iberus, 39 (1), 2021
6
S
IMONE
& R
OLÁN
: New genus and species of freshwater cochliopids from Goiás, Brazil
7
Figures 19-27. Atomicus inopinatus anatomical features. 19: head-foot, female, frontal view; 20:
foregut, right-slightly ventral view, jaw plate seen by transparency; 21: central nervous system,
ventral view; 22: head-foot, male, frontal view, adjacent region of prostate also shown as in situ
and slightly deflected to the right (left in Fig.); 23: pallial cavity roof, female, ventral-inner view,
and uncoiled visceral mass; 24: head and haemocoel, ventral view, foot and columellar muscle
removed; 25: pallial oviduct, ventral view; 26: odontophore, dorsal view, outer layer of muscles
and membranes removed, left structures (right in Fig.) deflected, right ones as in situ; 27: mid and
hindgut, and pericardium, ventral view, topology of mantle border also shown.
Figuras 19-27. Características anatómicas de Atomicus inopinatus. 19: cabeza-pie, hembra, vista
frontal; 20: intestino anterior, vista ventral ligeramente derecha, placa de la mandíbula vista por trans-
parencia; 21: sistema nervioso central, vista ventral; 22: cabeza-pie, macho, vista frontal, mostrando
también la región adyacente a la próstata como in situ y ligeramente desviada hacia la derecha
(izquierda en la Fig.); 23: techo de la cavidad paleal, hembra, vista ventral-interna y masa visceral
desenrollada; 24: cabeza y hemocele, vista ventral, retirados el pie y músculo columelar; 25: oviducto
paleal, vista ventral; 26: odontóforo, vista dorsal, retiradas la capa externa de músculos y membranas,
estructuras izquierdas (derecha en Fig.) desviadas, derechas como in situ; 27: intestino medio y posterior,
y pericardio, vista ventral, también se muestra la topología del borde del manto.
100 µm
100 µm
19 20
21
22
23
24
27
26
25
cm
ey
ft
sn
mo
pg
te
rn
bg
rs
od
mj
es
m2
jw
ot
mo
su
sy
pn
ce
pl
pt
vd
vd
cm
pe
an te
sn
ft
fs
pg
ovdd
vo
dg
oy st es
ss
mb
inpcki fe
rt
os
sr
at
ig
fp
m4
m6 oc m4
m5
vo
mo
sn
te
od
rs
sg
bg
ce
an
ss in pc
dd
st
tg es es ve au cv
rt
mb
m5
100 µm
100 µm
100 µm
100 µm
100 µm
100 µm
ag
as posterior esophagus (Fig. 27: dd),
running towards posterior. Intestine
originating dorsally and to the left of
esophageal insertion (Fig. 27: in), as wide
as local esophagus; three closely set
intestinal loops, similar in size, first loop
ventral, second loop dorsal-right from
style sac. Third loop pallial as rectum
(Figs. 23, 27: rt). Rectum fecal pellets and
anus described above (pallial cavity).
Genital system, male (Fig. 22): Vas
deferens relatively straight in gastric and
renal region, inserted terminally in
prostate (vd). Prostate (pt) with ~1/6
width of pallial cavity , ~1/3 its length,
white, totally closed (tubular). Pallial vas
deferens originating by tapering prostate
anterior region (inferior vd); in short dis-
tance penetrating in floor of pallial
cavity by side of penis base, running
immersed in integument. Penis (pe),
simple, stubby, curved, base broad, grad-
ually tapering to bluntly pointed tip;
length ~1/4 total head-foot length and
width. Penis duct seen by transparency
along central penial region, up to penis
distal tip; aperture distal, simple, small.
Genital system, female (Figs. 23, 25):
Ovary (oy) subterminal in last visceral
whorl, ~1/5 size of digestive gland. Vis-
ceral oviduct very narrow, running along
middle level of columellar surface of vis-
ceral mass ~1 whorl long (vo). Oviduct
insertion lateral in tip of elongated
ingesting gland (ig), gradually tapering
towards anterior, inserted between
middle and anterior thirds of pallial
oviduct gland. Seminal vesicle (sv) flat-
tened, trifid posterior end, narrowing
rather subtly; inserted to the right and
slightly anterior to insertion of ingesting
gland. Capsule gland with anterior third
narrower than posterior 2/3, ending in
very short hollow atrium (at). Female
pore as small, protruded papilla (fp).
Central nervous system (Fig. 21):
Nerve ring located just posterior to buccal
mass (Fig. 24: ce). Each cerebral ganglion
(ce) greatly fused with pleural ganglia (pl),
both forming somewhat oval mass, with
size equivalent to esophageal section; cere-
bral commissure narrow, with ~half length
of each ganglion. Pleural ganglia (pl) of
difficult individualization, with ~half size
of cerebral ganglia, located just ventral to
them. Each pedal ganglion (pn) as large
as cerebral ganglion, somewhat spherical;
pedal commissure as long as cerebral com-
missure. Pair of statocysts (sy) located in
ventro-posterior side of pedal ganglia;
with large, single statolith inside.
Measurements (width and height in
mm): Usually between 0.7-0.9 mm in
width (N= 30). Holotype MZSP 151666
(Figs. 1-2): 0.98 by 0.55; Paratype MZSP
151667 (Figs. 6-9): 0.98 by 0.66;
Distribution: Only known in the type
locality.
Habitat: Found under leaves of a
small river (Fig. 1) which continues the
warm spring (Figs 2, 3), sandy-mud
bottom, ~0.5 m deep, slow water flow.
Presence of anthropogenic impact.
Remarks: See Discussion.
Iberus, 39 (1), 2021
8
Genus Heleobia Simpson, 1865
Heleobia apua n. sp. (Figures 28-53)
urn:lsid:zoobank.org:act:D6015FB3-8FD3-4EAE-81F7-8EC251756317
Type material. Holotype: BRAZIL • 1 spm (Fig. 29) ; Goiás, Chapada dos Veadeiros, Colinas do Sul;
14°13’19.41”S 47°55’05.01”W; E. Rolán leg.; in a hot spring with a small river; MZSP 144664. Paratypes:
BRAZIL • same data as for holotype; MZSP 27863 • 6 sh; same data as for holotype; MZSP 144665
• 30 spm; same data as for holotype; MZSP 97861 • 2 spm; same data as for holotype; MNRJ • 2
spm; same data as for holotype; MNCN • 2 spm; same data as for holotype; MHNS • 2 spm; same
data as for holotype; NHMUK.
Type locality: BRAZIL, Goiás, Chapada dos Veadeiros, Colinas do Sul, 14°13’19.41”S 47°55’05.01”W,
in a hot spring with a small river.
Etymology: The specific name is a Latinization from the Guarani language, the word apu’a, meaning
rounded, and allusion to the shell’s outline.
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: New genus and species of freshwater cochliopids from Goiás, Brazil
9
28 29
30
31
32 33 34 35 36
37 38 10 µm
20 µm
50 µm
Figures 28-38. Heleobia apua anatomical features. 28: paratype MZSP 97861, frontal view (L 3.86
mm); 29: holotype MZSP 144664, SEM, frontal view (L 3.60 mm); 30: paratype MZSP 144665
right view (L 3.75 mm); 31: same detail of apex, apical view; 32, 33: operculum of figure 28, outer
and inner views (W 1.27 mm); 34, 35: paratype MZSP 97861 operculum, SEM, outer and inner
views (W 1.37 mm); 36: detail of operculum surface; 37, 38: radula, SEM.
Figuras 28-38. Características anatómicas de Heleobia apua. 28: paratipo MZSP 97861, vista frontal
(L 3,86 mm); 29: holotipo MZSP 144664, MEB, vista frontal (L 3,60 mm); 30: paratipo MZSP
144665 vista derecha (L 3,75 mm); 31: mismo detalle de ápice, vista apical; 32, 33: opérculo de la
figura 28, vistas externa e interna (ancho 1,27 mm); 34, 35: paratipo MZSP 97861 opérculo, MEB,
vistas externa e interna (W 1,37 mm); 36: detalle de la superficie del opérculo; 37, 38: rádula, MEB.
200 µm
Diagnosis: shell shorter than 4 mm;
suture shallow, whorls profile convex,
tip slightly pointed; wide complete peri-
stome; umbilicus lacking. Operculum
simple, reticulated. Penis long, thick,
lacking appendices. Receptacle bifid;
ingesting gland zigzagging. Freshwater.
Description: Shell (Figs. 28-31): size up
to 4 mm; elongate, ovate to cone-shaped,
with slightly curved profile, not umbili-
cate; whorls slightly convex, shallow su-
ture, adult ~4-5 whorls. Sculpture absent
except for growth lines, and some obso-
lete, sparse spiral striae (Figs. 29, 31).
Colour pale brown, translucent (Fig. 28).
Protoconch (Fig. 31) of ~250 µm, with
~1.5 smooth whorls. Teleoconch of ~3.5
whorls. Spire angle ~45°. Aperture semi-
circular, peristome continuous; ~40% of
total shell length, ~65% of shell width;
profile orthocline (Fig. 30); inner lip al-
most straight, ~50° in relation to longitu-
dinal axis; outer lip and inner third of in-
ner lip forming continuous semi-circle
(Figs. 28, 29), relatively thick; anal region
with relatively narrow notch, with small
callus on left edge; incurrent region
widely rounded. Umbilicus closed.
Head-foot (Figs. 41, 42, 44, 50): Rela-
tively wide, stubby; exposed areas pig-
mented dark brown, almost black, ex-
cept for lighter region in peri-buccal re-
gion of snout. Mesopodium thick,
relatively short (Fig. 41: fs). Anterior fur-
row of pedal glands (Fig. 41: pg) deep,
restricted to anterior edge. Opercular
pad (Fig. 41: op) elliptic, subterminal, oc-
cupying most of posterior foot dorsal
surface. Head bulbous, with ~90% of
foot width; pair of cephalic tentacles (te)
simple, thick, with ~half foot length. Eye
(ey) at outer side of tentacles base; ~half
width of tentacles base. Snout slightly
shorter than tentacles length; ~1/4 tenta-
cles width (sn); anterior end rounded
dorsally, notched ventrally (Fig. 44);
mouth triangular, subterminal, ventral
(Figs. 44: mo). Columellar muscle thick,
~3/4 whorl, simply curving to right
(Figs. 41, 41: cm). Haemocoel elongated,
in central region of head-foot (Fig. 44).
Operculum (Figs. 32-35): Corneous,
thin, translucent, pale yellow-beige,
flexible, paucispiral. Outline semi-circu-
lar, ~twice as long as wide, occupying
partially shell aperture (Fig. 28). Edges
relatively thick. Nucleus located in
middle region of inner third, (Figs. 32,
34); after nucleus, only sub-parallel
growth lines and microscopic mosaic of
reticulate striae (Fig. 36). Inner surface
glossy, scar elliptic, ~3 times longer than
wide, occupying ~half of inner surface,
located closer to internal edge, but not
touching it (Figs. 33, 35).
Mantle organs(Figs. 39, 40, 45): Some-
what narrow, with ~1 whorl in length.
Mantle edge simple, not very thick, wide,
unpigmented. Osphradium short (os),
elliptical, simple; length ~6% pallial cavity
length, located in anterior-left corner of
cavity, close to gill, away from mantle
border. Gill (gi) elongated, narrow, with
~80% of pallial cavity length and 25% of
cavity width; anterior end bluntly pointed,
posterior to mantle edge; posterior region
narrowing gradually, filaments ending at
some distance from pericardium. Gill fil-
aments rather triangular, distal tip
rounded (Fig. 45: gi). Between gill and
rectum, a short distance equivalent to 5%
of pallial cavity width. Hypobranchial
gland (hg) thin. Rectum wide, relatively
straight, reaching up to 1/3 of pallial
cavity width in some points; bearing
aligned series of rounded fecal pellets (fe),
easily seen by transparency (Figs. 39, 40,
51); rectum displaced from right mantle
cavity edge by pallial genital ducts. Anus
simple, shortly siphoned, located a dis-
tance from mantle edge ~5% of cavity
length. Genital ducts running along right
edge, relatively massive, described below.
Visceral mass (Figs. 39, 40, 43, 51):
Length ~3 whorls, leaving ~2 first shell
whorls empty in adult specimens. Most
structures pale beige to white in colour,
mantle locally pigmented dark brown.
Stomach as anterior structure, compress-
ing ventrally small reno-pericardial
structures; stomach of ~0.5 whorl, with
width almost as entire adjacent whorl.
Digestive gland greenish, of ~2.5 whorls,
mostly posterior to stomach. Gonad
running along columellar surface of each
whorl when mature, weakly distinct
from digestive gland. Other genital and
digestive details below.
Iberus, 39 (1), 2021
10
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: New genus and species of freshwater cochliopids from Goiás, Brazil
11
Figures 39-45. Heleobia apua anatomical features. 39: pallial cavity roof, female, ventral-inner
view, and coiled visceral mass; 40: same for male, pallial vas deferens detached from integument
and shown as in situ; 41: head-foot, male, ventro-right view; 42: same, frontal view; 43: detail of
first whorl of visceral mass slightly uncoiled, female, apical view; 44: head and haemocoel, ventral
view, foot and columellar muscle removed; 45: pallial cavity roof, female, transverse section along
its middle region.
Figuras 39-45. Características anatómicas de Heleobia apua. 39: techo de la cavidad paleal, hembra,
vista ventral-interna y masa visceral enrollada; 40: lo mismo para macho, los conductos deferentes palea-
les desprendidos del tegumento y mostrados como in situ; 41: cabeza-pie, macho, vista ventral-derecha;
42: lo mismo, vista frontal; 43: detalle de la primera vuelta de masa visceral ligeramente desenrollada,
vista apical, hembra; 44: cabeza y hemocele, vista ventral, pie y músculo columelar extraídos; 45: techo
de la cavidad paleal, hembra, sección transversal a lo largo de su región media.
500 µm
39
40
42
41
43
45
44
dg ki agrt fe cg fp
an
mb
oy
st
ss
es in aa ve pc au
gi cv os
cm
vd
pt rt fe
an
ts
dg
st
sv es gi cv os
es
mb
op
mb
te
ft fs
pg
sn
oy
dg rt af
pe
cm
mb
ey
te ft sn mt cg hg gi
rm
sy
sn mo
te
ey
pn
od
sg
es
di
cv
es
tg
500 µm
500 µm
500 µm 500 µm
500 µm
Circulatory and excretory systems
(Fig. 39): Pericardium narrow, located
longitudinally between stomach and
pallial cavity (pc), volume ~1/10 of that
of visceral mass; auricle (au) anterior,
small, just posterior to posterior end of
ctenidial vein (cv); ventricle (ve) poste-
rior, simple. Kidney (ki) minute, slightly
smaller than pericardium, located in
right side of pallial cavity posterior end;
inner tissue totally solid, white.
Nephrostome small, transverse, located
close to pericardium.
Digestive system (Figs. 46-49, 51):
Mouth at antero-ventral end of snout
(Fig. 44: mo). Pair of strong ventral retrac-
tor muscles of snout and mouth (Figs. 44,
53: rm); originating in middle level of
haemocoelic ventral floor; running close
to median line towards anterior, flanking
ventral surface of buccal mass, passing
through nerve ring (Fig. 53); inserted
along ventral wall of snout. Buccal mass
occupying entire inner surface of snout
and ~1/4 of haemocoelic volume. Pair of
jaw plates (Fig. 47: jw) close to each other,
restricted to dorsal wall of buccal cavity;
each jaw oval and very thin, translucent.
Odontophore spherical, with ~half of
buccal mass volume. Odontophore mus-
cles (Figs. 48, 49): mj, pair of jaw and
peribuccal muscles, originating in lateral
and ventral region of mouth, running to-
wards posterior as part of oral tube along
~half odontophore length (Fig. 46), in-
serted in latero-ventral mid region of
odontophore cartilages (Fig. 48), united
in median region; m1l, pair of thin retrac-
tor jugal muscle, originating in middle
par of haemocoel floor, running anterior-
ly along ~half odontophore length, in-
serted on lateral branch of mj (Fig. 46);
m2, pair of posterior retractor muscles of
odontophore (Figs. 46, 48), narrow, origi-
nating in lateral region of haemocoel in-
ner surface, in its middle level, running
towards anterior for a distance slightly
longer than buccal mass length, inserted
in postero-lateral region of odontophore
cartilages (Fig. 46); m4, pair of main dor-
sal tensor muscle of radula (Fig. 49),
broad and thick, surrounding outer later-
al surface of odontophore cartilages, orig-
inating from their ventro-lateral surface,
inserted in lateral edges of subradular
cartilage in its region in buccal cavity, and
also in radular sac region preceding buc-
cal cavity; m5, pair of secondary dorsal
tensor muscles of radula (Figs. 48, 49),
narrow and thick, originating in posteri-
or surface of m4, running towards medial
and anterior, between cartilages, inserted
in ventral side of radular ribbon in its re-
gion exposed in buccal cavity (Fig. 49);
m6, horizontal muscle, thin and wide,
connecting ventral edge of both odon-
tophore cartilages along ~75% of their
length (Fig. 49); m10, pair of ventral pro-
tractor muscles of buccal mass (Fig. 46),
relatively narrow and thin, originating in
ventral edge of mouth, just ventral to re-
tractor muscle (mr) origin, running to-
wards posterior for a distance equivalent
to odontophore length, inserted in poste-
rior-ventral edge of odontophore carti-
lages; mc, layer of transversal muscles in
ventral region of buccal mass, covered by
m10 pair (Figs. 46, 47). Subradular carti-
lage relatively wide in region of buccal
cavity (Fig. 48: sc). Odontophore carti-
lages elliptic, somewhat flattened lateral-
ly, ~twice as long as wide, anterior and
posterior edges rounded and similar (Fig.
49: oc). Radular sac with length ~1.5
times that of odontophore (Fig. 46: rs);
radular nucleus (rn) not widening. Radu-
la (Figs. 37-38): rachidian tooth triangu-
lar, distal tip curved inwards, with ~25%
of radular ribbon width, height about 3/4
of width, base simple, weakly arched, 2
pairs of latero-basal cusps; 5 terminal tri-
angular cusps, central cusp more than
twice as large as others, cusps greatly di-
minishing towards lateral; cusps restrict-
ed to distal, curved edge; lateral tooth
with main region rectangular, with
~twice rachidian height and its same
width, ~5-6 cusps similar to those of
rachidian, cusps smaller in both ends, be-
ing gradually larger towards median,
slightly lateral region; inner and outer
lateral tooth of similar shape, the outer
tooth ~30% narrower than inner margin-
al tooth, ~twice the length of lateral tooth
and ~40% narrower, general form as a
rod curved inwards at tip, tip flattened,
bearing ~10 inner terminal cusps of simi-
lar size; each cusp small, sharply pointed.
Iberus, 39 (1), 2021
12
S
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: New genus and species of freshwater cochliopids from Goiás, Brazil
13
Figures 46-53. Heleobia apua anatomical features. 46: foregut, left view; 47: buccal cavity and
anterior esophagus, both opened longitudinally, odontophore removed, salivary duct (sd) seen by
translucency; 48: odontophore, ventral view, first layer of muscles and membranes removed; 49:
odontophore, dorsal view, radular sac removed, both cartilages (oc) deflected; 50: isolated head,
male, dorsal view; 51: mid and hindgut, ventral view, topology of some adjacent structures shown;
52: pallial oviduct, ventral view, topology of anus shown; 53: central nervous system, ventral view,
adjacent retractor muscle of snout (rm) shown.
Figuras 46-53. Características anatómicas de Heleobia apua. 46: digestivo anterior, vista izquierda;
47: cavidad bucal y esófago anterior, ambos cortados longitudinalmente, odontóforo retirado, conducto
salival (sd) visto por transparencia; 48: odontóforo, vista ventral, primera capa de músculos y membra-
nas retiradas; 49: odontóforo, vista dorsal, saco radular retirado, ambos cartílagos (oc) desviados; 50:
cabeza aislada, macho, vista dorsal; 51: intestino medio y posterior, vista ventral, se muestra la topología
de algunas estructuras adyacentes; 52: oviducto paleal, vista ventral, se muestra la topología del ano; 53:
sistema nervioso central, vista ventral, se muestra el músculo retractor adyacente del morro (rm).
500 µm
46 47
48
49
50
52
53
51 500 µm
500 µm
500 µm
500 µm
500 µm
mo
momj
mc
jw
sa
sd
df
bg
dc
se
sd
sd
es ef
od
ot
m10
mc
m1l
rs
m2
es
sc
ra
m5
rs
rn
mj
m2
rn
mj
m4
mo
br m6 oc
m5
ov
fe
in
sn
ey
pd
mo
te
vd
pe
tg
st
dd es pc rt
ss in ki
su
dg vo
go sy
cg
ce
pl
fp
pn
an
rm
sr
ag
ig
vo
Salivary gland small (Figs. 44: sg),
white, with maximum length ~half buc-
cal mass length; salivary aperture (Fig
41: sa) in middle level of the inner edge
of dorsal fold , preceded by short por-
tion of salivary ducts (sd) running im-
mersed in them. Dorsal folds of buccal
mass (Fig. 47: df) smooth, simple, wide,
located close to each other, originated
from jaw plates, fainting in esophageal
origin. Esophagus simple along haemo-
coel (Figs. 23-24: es), almost straight,
lacking glandular areas (Figs. 46, 47);
esophageal inner surface simple, low,
weak longitudinal folds. Stomach di-
mensions and positions described above
(visceral mass); possessing main gastric
chamber posterior, with rounded poste-
rior surface, and narrow style sac (Figs.
51: ss), style sac length ~half remaining
gastric length. Style sac totally separated
from intestine; esophagus (es) inserted
just posterior to style sac and intestine
(in), on left stomach side; duct to diges-
tive gland ~half of posterior esophagus
width, originating at a short distance
posterior to esophageal insertion (Fig.
51: dd), running towards posterior. In-
testine originating anterior to
esophageal insertion (Figs. 51: in), with
~twice esophagus width, and left of
style sac; running surrounding ven-
trally-anteriorly the style sac up to dor-
sal region of kidney, subtly curving in
region preceding pallial cavity. Rectum
fecal pellets and anus described above
(pallial cavity). Fecal pellets formed
only after renal portion of intestine
(Figs. 51: fe).
Genital system, male (Figs. 40, 42,
50): Testis (ts) restricted to posterior half
of digestive gland (Figs. 40: ts). Seminal
vesicle (sv) very convolute, located in
columellar region of visceral mass
ventral to stomach, colour pale grey-iri-
descent; inserted in prostate subtermi-
nally (Fig. 40: sv), just posterior to
middle level of prostate. Prostate with
~1/4 pallial cavity width, somewhat
dorso-ventrally flattened, white (Fig. 40:
pt). Vas deferens originating from
prostate ventral-middle region, rela-
tively close to visceral vas deferens
insertion (Fig. 40: vd); after long dis-
tance penetrating in floor of pallial
cavity up to penis base, running
immersed in integument (Fig. 50: vd).
Penis (Figs. 42, 50: pe), simple, curved,
elongated (almost as long as pallial
cavity) base slightly broad, slightly and
gradually tapering up to rounded tip.
Penis duct seen by transparency,
running straight along central penial
region, up to penis distal tip (Fig. 50:
pd); aperture distal, simple, small.
Genital system, female (Figs. 39, 43,
45, 52): Visceral structures similar to
those of males; ovary (Fig. 43: oy) pos-
sessing 3-4 relatively distant bundles.
Visceral oviduct very narrow, running
along middle level of columellar surface
of visceral mass ~1 whorl (vo). Visceral
oviduct inserted subterminally in poste-
rior-left region of pallial oviduct (Fig.
52: vo). In this region, seminal receptacle
projected anteriorly, and ingesting gland
projected posteriorly. Seminal receptacle
bilobed distally, size ~1/30 of pallial
oviduct (sr). Ingesting gland similar in
size to receptacle, looking like tubular
zigzag (ig). Albumen gland (ag) and
capsule gland (cg) about half and half
along oviduct length; walls thick glan-
dular, white, lumen flattened (Fig. 45);
minute terminal atrium with walls not
very thick, tapering up to small female
pore. Female pore shortly siphoned,
papilla-like, turned anteriorly (fp),
located close to and to the right of anus.
Central nervous system (Fig. 53):
Nerve ring located just posterior to
buccal mass, with pedal ganglia slightly
more anterior (Fig. 44: pn) than remain-
ing ganglia. Each cerebral ganglion (ce)
oval, with size equivalent to esophageal
section; cerebral commissure narrow,
about as long as each ganglion. Pleural
ganglia (pl) with ~half size of cerebral
ganglia, located just ventral to them
widely fused with cerebral ganglia.
Each pedal ganglion (pn) slightly larger
than cerebral ganglion, somewhat
spherical, pedal commissure ~half of
each ganglion length. Cerebro-pedal
and pleuro-pedal connectives about as
long as pedal ganglia. Subesophageal
ganglion (su) with ~half pleural gan-
glion size, located a short distance from
Iberus, 39 (1), 2021
14
Heleobia pukua n. sp. (Figures 54-66)
urn:lsid:zoobank.org:act:3638E295-7514-4A39-99E7-35DFAC22D384
Type material. Holotype: BRAZIL • 1 spm (Fig. 57); Goiás, Chapada dos Veadeiros, Colinas do
Sul; 14°13’19.41”S 47°55’05.01”W; E. Rolán leg.; in a hot spring with a small river; MZSP 151668.
Paratypes: BRAZIL • 19 spm (Figs. 54-56); same data as for holotype; MZSP 97863 • 3 sh; MZSP
144666.
Type locality: BRAZIL, Goiás, Chapada dos Veadeiros, Colinas do Sul, 14°13’19.41”S 47°55’05.01”W.
Etymology: The specific name is a Latinization from the Guarani language, the word puku, meaning
elongated, long, an allusion to the shell’s outline.
for: head slightly wider; anterior region
of snout flatter, with mouth (mo) in middle
of pair of convexities; colour brown in
exposed areas, with white band just above
anterior surface of snout (Fig. 54 by
translucency). Operculum more rounded
by ~10%; inner scar also more rounded,
mainly in middle; operculum with two
layers, separated from each other in middle
and superior regions (Fig. 66).
Mantle organs (Figs. 61, 65): Features
similar to H. apua, distinctions follow-
ing: osphradium (os) slightly ~20%
larger and longer; gill (gi) filaments
~20% taller; intestine (in) slightly more
zigzagging in pallial hoof.
Visceral mass (Fig. 61): As that of H.
apua, except for one more whorl in
length.
Circulatory and excretory systems
(Fig. 61): Similar to those of H. apua,
except in being ~10% smaller.
Digestive system (Figs. 61, 62): Most
attributes similar to those of H. apua,
distinctions and remarkable characters
following: buccal mass (bm) and odon-
tophore with same components, ~30%
larger, with esophageal pair of folds
slightly longer and taller. Radula (Fig.
60) with similar components and pro-
portions; rachidian with 7 more uniform
and smaller distal cusps, 4 pairs of basal
S
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: New genus and species of freshwater cochliopids from Goiás, Brazil
15
Diagnosis: shell shorter than 4 mm;
suture shallow, whorls profile straight,
tip slightly pointed; wide incomplete
peristome; umbilicus lacking. Opercu-
lum double-layered, only with growth
lines. Penis long, narrow, lacking appen-
dices. Receptacle balloon-like; ingesting
gland with single loop. Freshwater.
Distinctive description: Shell (Figs. 54-
59): elongate, conical, with somewhat
straight profile; whorls weakly convex,
shallow suture, adult ~5-6 whorls.
Sculpture absent except for growth
lines. Colour pale brown, translucent
(Figs. 54-56). Protoconch (Figs. 58-59) of
~340 µm with ~1 smooth whorl, mostly
eroded in adult forms. Teleoconch of ~6
whorls. Spire angle ~35°. Aperture semi-
circular, peristome interrupted in supe-
rior columellar area; ~35% of total shell
length, ~70 of shell width; profile ortho-
cline (Fig. 55); inner lip weakly concave,
~40° in relation to longitudinal axis;
outer lip and interior third on inner lip
forming continuous semi-circle (Figs. 54,
57), relatively thick; anal region lacing
notch, only angle of ~85°; incurrent
region widely rounded, slightly pro-
jected anteriorly. Callus very thin.
Umbilicus closed.
Head-foot and operculum (Figs. 62,
63): Characters similar to H. apua, except
right pleural ganglion. Pair of statocysts
(sy) located in ventro-posterior side of
pedal ganglia; left one slightly more
distant than right statocyst.
Measurements (length and width in
mm): The largest specimens reach up to
4 mm. Holotype 3.60 by 1.88; paratype
MZSP 97861 (Fig. 28): 3.86 by 1.90.
Distribution: Only known in the type
locality.
Habitat: Found under leaves in the
water course of a small river (Fig. 1)
which continues the warm spring (Figs
2, 3), sandy-mud bottom, ~0.5 m deep,
slow water flow. Presence of anthro-
pogenic impact.
Iberus, 39 (1), 2021
16
Figures 54-60. Heleobia pukua anatomical features. 54-56: paratype MZSP 97863 (L 4.39 mm),
frontal, right and dorsal views; 57: holotype, SEM (L 4.28 mm); 58: paratype MZSP 97863,
detail of protoconch, SEM, apical view; 59: same for paratype 144666; 60: radula, SEM.
Figuras 54-60. Características anatómicas de Heleobia pukua. 54-56: paratipo MZSP 97863 (L 4,39
mm), vistas frontal, derecha y dorsal; 57: holotipo, MEB (L 4,28 mm); 58: paratipo MZSP 97863,
detalle de la protoconcha, MEB, vista apical; 59: lo mismo para el paratipo 144666; 60: rádula, MEB.
pointed projection in right side of its
main portion; style sac (ss) and intestine
(in) slightly broader; intestine with
~20% larger fecal pellets (pe) and more
zigzagging in pallial roof.
Genital system, male (Figs. 63, 64):
Most characters similar to those of H.
cusps more uniform and proportionally
smaller; lateral and marginal teeth with
proportionally smaller and more
uniform distal cusps. Esophagus
slightly longer, stored in zigzag fashion
in haemocoel (Fig. 62: es). Salivary
glands absent. Stomach (st) with
54 55
56
57
58
59 60 10 µm
100 µm
100 µm
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& R
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: New genus and species of freshwater cochliopids from Goiás, Brazil
17
Figures 61-65. Heleobia pukua anatomical features. 61: pallial cavity roof, male, ventral-inner view,
and visceral mass, prostate slightly deflected; 62: head and haemocoel, ventral view, foot and col-
umellar muscle removed; 63: head-foot, male, frontal view; 64: detail of penis region, dorsal view;
65: pallial oviduct, ventral view, topology of some adjacent structures also shown.
Figuras 61-65. Características anatómicas de Heleobia pukua. 61: techo de la cavidad paleal, macho,
vista ventral-interna y masa visceral, próstata ligeramente desviada; 62: cabeza y hemocele, vista
ventral, pie y músculo columelar retirados; 63: cabeza-pie, macho, vista frontal; 64: detalle de la región
del pene, vista dorsal; 65: oviducto paleal, vista ventral, también se muestra la topología de algunas
estructuras adyacentes.
apua, except for: Seminal vesicle (sv)
coiling in smaller area, coiling appar-
ently more chaotic. Separation between
visceral and pallial vas deferens (vd) in
prostate (pt) ~60% further away. Penis
(pe) narrower, slender, ~50% longer,
profile more uniform; colour pure
white.
Genital system, female (Fig. 65): Vis-
ceral and pallial structures mostly like
those of H. apua, with main differences
in posterior region of pallial oviduct:
500 µm
61
65
64
63
62
500 µm
500 µm 500 µm
500 µm
cm
vd fe
pt
in
sv
ss
st dd
es
aave ki au pc rt cv
an
mb
os
gi
sy
pn
te
sn
bm
tg
di
es
rs
rm
mo
dg
ft
fs
pe
es
te
ey
pg
sn
pe
cm
vd
cg
pd
vo ig
ag
sr
mb
an
fp
at
Iberus, 39 (1), 2021
18
Figure 66. Heleobia pukua operculum in light microscopy in three positions from inner view (left)
to profile (right), showing double layers (W 1.2 mm).
Figura 66. Opérculo de Heleobia pukua en microscopía óptica en tres posiciones desde vista interna
(izquierda) hasta perfil (derecha), mostrando capas dobles (W 1,2 mm).
visceral oviduct (vo) inserted in base of
ingesting gland (ig), containing single
wide loop inside; seminal receptacle (sr)
simple, balloon-like. Separation between
albumen (ag) and capsule (cg) glands
slightly wider. Female atrium (at) ~3
times longer and wider.
Central nervous system (Fig. 62):
With same features as those of H. apua,
except for subesophageal ganglion (su)
being less sharp and located slightly
further away.
Measurements (length and width in
mm): Holotype: MZSP 151668: 4.28 by
1.76. Paratype MZSP 97863 (Figs. 54-56):
4.39 by 1.99.
Distribution: Only known in the type
locality.
Habitat: Found under leaves in the wa -
tercourse of a small river (Fig. 1) which con-
tinues the warm spring (Figs 2, 3), sandy-
mud bottom, ~0.5 m deep, slow water flow.
Presence of anthropogenic impact.
Remarks: see Discussion.
DISCUSSION
As stated elsewhere (S
IMONE
, 2006b,
2011), what is now referred as Ris-
sooidea Truncatelloidea and Littori-
noidea are part of a single taxon sup-
ported by several interesting synapo-
morphies, such as the closure of the
male and female genital ducts. They can
be regarded as forming a single super-
family within Caenogastropoda, or as
three superfamilies united in a suborder
within that order. This taxonomical
treatment is still in a state of flux, as the
group is highly diverse. This is the
reason for calling “rissooideans/trun-
catelloidean” in present paper.
The new genus Atomicus is the first
discoid Rissooidea/Truncatelloidea
taxon found in Brazilian territory, and
possibly in South America as far as
known. That, beforehand, makes easy
its distinction with other local genera.
Additionally, with less than 1 mm, it
appears to be the smallest freshwater
taxon in the mainland. The fully devel-
oped genital structures and gonads with
developed gametes show that the exam-
ined specimens are adult. Anatomically,
on the other hand, Atomicus looks
similar to the local cochliopids, such as
the Heleobia described herein. The main
difference is in the absence of the gill,
which can be explained by the minute-
ness of the species. However, the
osphradium remained (Fig. 23: os), its
size is proportional to the osphradia of
the other genera. The overall anatomical
attributes also look like the taxa of the
same family, including the size, position
and form of digestive tubes and genital
structures. Because of the small size,
most structures look simplified. As main
differences of the new genus, the follow-
ing can be evoked: the foot is propor-
tionally shorter (Figs. 19, 22); the odon-
tophore pair m5 originated directly
from the cartilages (Fig. 26); the central
radular tooth (rachidian and lateral) has
minute, more numerous and more
uniform cusps (Fig 18); prostate has its
connection with vas deferens at both
extremities (Fig. 22: pt) (they are not
subterminal); and the central nervous
system lacks the bulged region of pedal
nerves (Fig. 21). The female pallial
oviduct has a somewhat similar
arrangement as in Heleobia, with an
ingesting gland in the end of visceral
oviduct and a receptacle originating
close to it (Fig. 25). This feature justifies
the familiar placement. The simplified
inner gastric surface, lacking sorting
areas, distinguishes Atomicus from
several north hemisphere genera, e.g.,
Hydrobia Hartmann, 1821 and Spur-
winkia Davis, Mazurkiewicz & Man-
drachia, 1982 (D
AVIS ET AL
, 1982).
Both Heleobia species described
herein are apparently small species for
the genus. They rarely reach 4 mm,
while the other species are easily larger
than 6-7 mm (S
IMONE
, 2006a, as Littorid-
ina). Two species are still smaller, such
as H. inconspicua (H
AAS
, 1938), from the
Brazilian northeast, and H. pusilla (Haas,
1949), from the Amazon region, from
which both species described herein dif-
fer in having a more pointed spire and
protoconch; from the former both still
differ in having a proportionally larger
aperture; and from the latter in having
less convex whorls and a sharper pro-
file. Heleobia apua and H. pukua are sym-
patric and similar in shell attributes.
Most of the distinctive features between
both species are explored above. This
discussion is mostly based on what ap-
pears to be the more important features.
The shells can be distinguished from
each other by the following characters:
H. apua (Figs. 28-30) has a shorter,
smaller and more inflated shell than H.
pukua (Figs. 54-57); the protoconch of H.
apua is 1.5 whorls long (Fig. 31), while
that of H. pukua has only 1 whorl (Figs.
58-59), which is difficult to see as it is
eroded in most adult specimens (Figs.
54-56); the shell aperture is shorter and
wider in H. apua (Figs. 28-29) than in H.
pukua (Figs. 54, 57). Anatomically, there
are the following additional differences:
the snout has a flap-like, slightly oblique
anterior surface in H. apua (Fig. 44),
while that of H. pukua is flatter and
transverse (Fig. 62); the operculum of H.
pukua is unique in being double layered
(Fig. 66); H. apua has a simpler and
shorter anterior esophagus (Fig. 44) than
that of H. pukua, which is coiled inside
haemocoel (Fig. 62: es); the penis of H.
apua is shorter, with a wider base (Fig.
50), while the penis of H. pukua is ~50%
longer, slender and with a more uniform
width along its length (Figs. 63-64); in
the pallial oviduct, H. apua has a zigzag
S
IMONE
& R
OLÁN
: New genus and species of freshwater cochliopids from Goiás, Brazil
19
of ingesting gland, and the receptacle is
bifid (Fig. 52), while in that of H. pukua
the ingesting gland has a single loop,
and the receptacle is simpler, balloon-
like (Fig. 65).
The genus Heleobia is very diverse,
with about 90 species in South America
(H
ERSHLER
& T
HOMPSON
, 1992; C
AZ
-
ZANIGA
, 2011; C
OLLADO
, 2015). As most
species have a high degree of endemic-
ity, the comparison of both new species
is focused in the species which occur in
the region (S
IMONE
, 2006a: 88-94) and in
freshwater environment, disregarding
some species which only occur in brack-
ish waters. Heleobia apua and H. pukua
differ from H. bertoniana (Pilsbry, 1911),
from Paraguay, in having a proportion-
ally shorter shell, with less convex
whorls, and a proportionally shallower
suture; both differ from H. manni (Baker,
1913), from Northeast Brazil, and from
H. siolii (Haas, 1949), from Pará, in hav-
ing a much less obese and more elon-
gated profile, and a proportionally
smaller aperture; both differ from H. par-
chappei (d’Orbigny, 1835), from South
Brazil, in having a less pointed spire,
fewer whorls, with a flatter profile; both
differ from H. robusta Silva & Veitern-
heimer-Mendes, 2004 in being much
more elongated, and in having a propor-
tionally smaller aperture; both differ
from Lyrodes subgranulatus (Haas, 1952),
from Pará, in having less convex whorls,
and a proportionally shallower suture;
both additionally differ from both Idiopy-
rgus species, from N-NE Brazil, in being
much smaller, with fewer whorls, spire
more obese and last whorl not fully pro-
jected from the normal shell growth.
Anatomically, the distinction of both
Heleobia species are difficult to explore, as
the anatomical information is scanty in
literature, and is not as detailed as the
present one. They differ from most
species [e.g., H. atacamensis (Philippi,
1860), H. deserticola Collado, 2015] (S
ILVA
,
2003; C
OLLADO ET AL
, 2013; C
OLLADO
,
2015) in lacking bulged glandular struc-
tures, also called stalked glands (D
AVIS ET
AL
, 1982) on the outer edge of the penis.
In fact, the smooth penis, lacking bulged
structures, approaches both new species
to the genus Andesipyrgus Hershler &
Velkovrh, 1993, in which both new
species cannot belong because lacking a
peristome totally detached from the
penultimate whorl, a pupiliform outline,
a pigmented animal, and a coiled
oviduct. The simple penis appears to be
linked to the subterranean cochliopid
taxa (H
ERSHLER
& V
ELKOVRH
, 1993),
which is not the case of both new species.
The anatomical features of the
genital system of the three species
studied here has the usual configuration
of the family Cochliopidae. The bulged
portion in the end region of the visceral
oviduct, however, have not attracted the
attention. It is called ingesting gland
herein, as it does not look like a recepta-
cle or a bursa copulatrix, and is not fully
hollow. On the other hand, a seminal
receptacle located close to the pallial
oviduct insertion appears to be a
common cochliopid feature. It is some-
times called bursa copulatrix, a struc-
ture that usually is located anteriorly,
close to the female genital aperture. The
insertion of the male visceral vas defer-
ens in the prostate has also not attracted
attention, but seems an interesting
feature, as sometimes it is terminal, and
sometimes subterminal. The same can
be said of the origin of the pallial vas
deferens after prostate portion.
The three new described species
apparently are not widely distributed.
They are possibly endemic of that
region. Further studies on their distribu-
tion and local anthropic impact are nec-
essary for confirming the degree of
endemicity and possible protective mea-
sures for them.
ACKNOWLEDGEMENTS
We are thankful to Jesús Méndez
and Inés Pazos, who made the SEM
photos in the Centro de Apoyo Cientí-
fico y Tecnológico a la Investigación
(CACTI) of the University of Vigo. we
also thank the anonymous referees for
improvement of several points of this
paper. The collect permit is IBAMA-
SISBIO # 10560-1.
Iberus, 39 (1), 2021
20
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21
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