Redescription of Acanthochitona terezae

Abstract

Acanthochitona terezae Guerra-Junior, 1983 was described based on 18 specimens collected at the intertidal zone of Bahia state, off ltapuã, NE Brazil. However, important taxonomic features were not addressed in the original description and the type specimens were deposited in neither the designated museum nor anywhere else, which makes the identity of this species unclear. The present paper designates a neotype from Espirito Santo state, and provides a redescription based on the neotype and some additional specimens in order to clarify its identity. The new data extends the species' range approximately 1000km southwards from the type locality.

Full text

Journal of ConChology (2017), Vol.42, no.6 491
REDESCRIPTION OF ACANTHOCHITONA TEREZAE
Jaime a. Jardim1, Sergio m. almeida1, 2 & luiz l. Simone1
1Museu de Zoologia da Universidade de São Paulo, Universidade de São Paulo, Av. Nazaré, 481 – Ipiranga,
São Paulo – SP, 04263–000
2Curso de Ciências Biológicas, Centro de Ciências Biológicas e Saúde, Universidade Católica de Pernambuco,
R. do Príncipe, 526 – Boa Vista, Recife – PE, 50050–900
Abstract Acanthochitona terezae Guerra- Junior, 1983 was described based on 18 specimens collected at the intertidal zone
of Bahia state, off Itapuã, NE Brazil. However, important taxonomic features were not addressed in the original description
and the type specimens were deposited in neither the designated museum nor anywhere else, which makes the identity of this
species unclear. The present paper designates a neotype from Espírito Santo state, and provides a redescription based on the
neotype and some additional specimens in order to clarify its identity. The new data extends the species’ range approximately
1000km southwards from the type locality.
Key words Acanthochitona terezae, redescription, neotype, new records, Brazil
IntroductIon
Acanthochitonidae is a diverse family of poly-
placophorans ranging from tropical to polar
regions. In the Western Atlantic, it is distributed
from the USA and the Caribbean to Brazil. The
genus Acanthochitona encompasses 105 valid spe-
cies living in warm waters from intertidal areas
to 60m depths (Lyons, 1988). On the Brazilian
coast, the following species were recorded: A.
spiculosa (Reeve, 1847); Acanthochitona hemp-
hilli (Pilsbry, 1893); A. pygmaea (Pilsbry, 1893);
A. rhodea (Pilsbry, 1893); A. brunoi Righi, 1971; A.
ciroi Righi, 1971, A. minuta Leloup, 1980, and A.
terezae Guerra- Junior, 1983 (Guerra- Junior, 1983;
Lyons, 1988; Kaas, Jones & Gowlett- Holmes,
1998).
Acanthochitona terezae Guerra- Junior, 1983 was
described from Bahia state, off Itapoã region,
based on the holotype and 17 paratype speci-
mens. Though the types received two catalog
numbers in the Museu Nacional da Universidade
Federal do Rio de Janeiro, they have never been
deposited in their collection or elsewhere, which
causes a taxonomic problem. In the process of
identifying specimens of Acanthochitona collected
off Espirito Santo state by the Marion- Dufresne
MD55 expedition (Simone & Cunha, 2012;
Salvador et al., 2014; Simone, 2014; Cavallari et
al., 2014; Simone & Cunha, 2014) and Trindad
Island in SE Brazil, and Fernando de Noronha
Island off Pernambuco state, NE Brazil, we found
that A. terezae has a problematic identity. In addi-
tion to the absence of the type material, many of
the taxonomically important features were not
described in detail, which makes distinguishing
this species from the other congeners a difficult
task.
In the present paper, we designate a neotype
for A. terezae from Espírito Santo, a location
close to the type locality in Bahia state. We also
take the opportunity to redescribe its morphol-
ogy in detail based on the neotype and some
additional specimens, in order to clarify its
identity.
MaterIal & Methods
All the specimens examined in this study were
preserved dry. Photographs were obtained using
a Zeiss AxioCam MRc5 and Zeiss AxioVision
SE64 Rel 4.8 imaging software. Image slices
were aligned and stacked with CombineZP
(Hardley, 2010). The distribution map was
drawn with DIVA- Gis 7.5 (Hijimans et al.
2001).
Specimens examined under SEM were previ-
ously cleaned with sodium hypochlorite solu-
tion and spur- coated with gold in the SEM-
Laboratory, Museu de Zoologia da Universidade
de São Paulo (MZSP).
Abbreviations: MNRJ, Museu Nacional da
Universidade Federal do Rio de Janeiro; MZSP,
Museu de Zoologia da Universidade de São
Paulo; MD55, R/V Marion Dufresne Expedition
MD55.
Contact author: jardim.jaime@gmail.com

Ja Jardim et al
492
systeMatIcs
Acanthochitona terezae Guerra- Junior, 1983
(Figs 1, 2a–f, 3a–e)
Neotype (selected herein) MZSP 115203 size
45mm × 10mm; coll. Bouchet, Leal, Métivier, 17-
05- 1987, lat. 20º50.9' S, long. 33º44.6' W, depth
63m., R/V Marion Dufresne, dry, entire, not
disarticulated.
Material examined MZSP 131609, 5 spm, size
(2.1mm × 1.2mm; 2.3mm × 1.4mm; 2.5mm × 1.2mm;
3.9mm × 1.8mm; 4.2mm × 2.6mm), 10- 07- 2012,
Fernando de Noronha Is. – Pernambuco State,
Pereira- Filho, G. col.; MZSP 131611, 1 spm
size (7.0mm × 3.5mm), 10- 07- 2012, Fernando
de Noronha Is.– Pernambuco State, Pereira-
Filho, G. col.; MZPS 131625, 2 spm size
(5.0mm × 3.2mm; 5.3mm × 2.2mm), 03- 11- 2016,
Fernando de Noronha Is.– Pernambuco State,.
Pereira- Filho, G. col.; MZSP 114221, 1 specimen,
size (8.7mm × 4.0mm), 20- 06- 2013, Trindade Is.
Espirito Santo State, Lima, P. col; MZSP 131636,
1 specimen, size (2.6mm × 1.5mm), 12- 05- 2014,
Trindade Is. Espirito Santo State, Mendonça, J.;
MZSP 131199, 1 specimen, size (6.0mm × 2.5mm),
12- 08- 2016, Trindade Is. Espirito Santo State,
Mendonça, J..
Neotype locality Brazil, Espirito Santo state,
20º50.9'S, 33º44.6'W, continental shelf.
Original type locality Brazil, Bahia state, Salvador,
off Farol de Itapuã, 12°57'25.18''S 38°21'13.37''W,
intertidal zone; coll. Orlando Guerra- Junior,
ii/1966.
Diagnosis (description of neotype) Animal large-
sized, up to 45mm × 10mm. Tegument cream to
beige, with many white spots mainly on api-
cal region. Girdle white with transverse orange
bands. Intermediate valves trapezoidal to
oblong in outline, subcarinate, weakly beaked.
Jugum pusturous not well demarcated from
latero- pleural areas. Pustules on latero- pleural
area round to oval, randomly arranged; each
Figure 1 Acanthochitona terezae Guerra- Junior, 1982, map of occurrence: Triangle indicates the original type local-
ity; star indicates the neotype locality; circles indicate other new localities of the A. terezae.

redeSCription of acanthochitona terezae 493
pustule convex, bearing 4–7 pores on superior
to median surface, lacking microaesthete pores.
Tail valve with prominent, submedian mucro;
postmucronal area concave. Dorsal side of girdle
covered with minute elongated spicules; spicule
height about 8–9 times as long as wide (80–90µm
in length), sculptured by longitudinal parallel
fissures. Sutural tufts with elongated spicules
about 350–450µm long and sculptured by longi-
tudinal fissures.
Redescription Animal large in size, up to
45mm × 10mm, oval and moderately elevated.
Valve i (Figs 2a, 3a, f) semicircular, with five
shallow slits; posterior margin almost straight;
anterior slope convex. Tegument sculptured by
randomly arranged, round to drop- like convex
pustules.
Valves ii- vii (Figs 2a, b, 3b, e) trapezoidal, mod-
erately elevated and subcarinate. Jugum area
(Fig. 3b) not clearly demarcated, with longitudi-
nal ridge- like, fused pustules. Pustules on latero-
pleural area round to oval, randomly arranged;
each pustule convex, 15–20µm in height, with 4–7
aesthete pores on anterior and median surface
(macropores and micropores undistinguishable).
Valve viii (Figs 2c, d, 3c) small, triangular;
mucro raised, submedian; postmucronal area
concave.
Articulamentum well developed, roughly
quadrate, color white. Valve i with insertion plate
short; with five shallow slits. Valves ii- vii with
sutural laminae reduced; insertion plates only
slightly expanded laterally beyond tegument.
Valve viii of sutural laminae broad separated
of insertion plates by shallow slits; slits formula
5/1/2.
Girdle (Figs 2a–f, 3d) white with orange bands.
Dorsal side of girdle covered by minute spicules
of variable size: 80–90 µm × 10 µm, sculptured
by longitudinal shallow fissures. Sutural tufts
with spicules (350–450 µm length) sculptured by
longitudinal shallow fissures; Spicules of girdle
margin large, five to six times longer than minute
dorsal spicules, more or less flattened, with about
25 longitudinal riblets of 150–250 µm in length:
Spicules of ventral side of girdle rectangular,
20–35 µm in size, smooth.
Gill abanal, merobranchial, with 7–10 filaments
on each side.
Radula (3mm length) with about 43 trans-
verse rows of mineralized teeth. Central tooth
rectangular, with a constriction on median por-
tion of structure; cusp smooth, with lobes on
each side that extend from apex of the tooth to
base, with about 23 µm in height. First lateral
tooth with nodulous antero- dorsal corner. Major
lateral tooth with tricuspid head; tip of each cusp
blunt. Major uncinal tooth slender, with narrow
blade and rather long base.
Additional description from other specimens
In the complete assemblage studied herein, body
length varied from 8mm to 15mm. Valves ii- vii
may present different levels of pustule fusion in
the jugal area. In small specimens, the sculpture
reported to larger specimens is the same but
with proportionally reduced pustules, and weak
predominance of non- fused pustules; valve viii
follow the same parameters described to valves
ii- vii. Large and smaller specimens present the
same distribution pattern of aesthete pores.
Distribution Brazilian coast, Morro do Pernam-
buco, Bahia state, 12°57'25.18''S 38°21'13.37''W to
Espirito Santo State, 20°51'S, 33°45'W, from inter-
tidal zone to 63m. (Fig. 1).
dIscussIon
Designation of the neotype
After the premature passing of Guerra- Junior,
the whereabouts of the voucher material
of Acanthochitona terezae were still unclear.
According to the original description, the type
material was deposited in the MNRJ (holotype
MNRJ 4584; paratypes MNRJ 4585, 17 spm).
However, Pimenta et al. (2014) reported that these
specimens have never been found, and probably
were never deposited in MNRJ collection. The
Instituto Oswaldo Cruz (Fiocruz), where Guerra-
Junior used to work, stated that any specimens
related to this species would have remained in
his personal study material. His family, how-
ever, assured us that no such material was found
among his personal belongings.
The original description of A. terezae is brief,
but the following are recognizable as important
taxonomic features: the intermediate valves are
wide, and the articulamentum only slightly
extends laterally beyond the lateral margins of the
tegmentum. The head valve, lateral areas of the
intermediate valves and the posterior area of the
tail valve have no prominent radial ribs although

Ja Jardim et al
494
Figure 2 Neotype of Acanthochitona terezae – MZSP 115203: a lateral view (left side) indicating sp –
spicules tufts, hv – head valve, av – tail valve, scale 0.5mm; b dorsal view, scale 0.5mm; c ventral view indicating
gr – girdle, scale 0,5mm; d of tail valve, indicating marginal spicules scale 0.1mm; e enlargement of lateral view
(left side) of girdle, scale 0,2mm; f enlargement of sculpture of intermediate valves (5–6) indicating tu – pustules,
scale 0.2mm.

redeSCription of acanthochitona terezae 495
Figure 3 Acanthochitona terezae (specimen sampled from Bahia state): a dorsal view of head valve, scale 100µm;
b intermediate valve (valve V), scale 100µm; c dorsal view of tail valve, scale100µm; d dorsal side of girdle, scale
10µm; e pattern of formation of the sculpture (valve VIII), scale 10µm, f pattern of the sculpture well developed
(intermediate valve), scale 10µm, g radula, dorsal view, scale 10µm, h radular central tooth oblique view from
right side, scale 10µm. (add clear, close up image of minute spicules of the girdle).

Ja Jardim et al
496
the head valve has five obsolete radial undula-
tions. The jugum of the intermediate valves and
the tail valve are pustulous, not clearly separated
from other areas. The sutural tufts are promi-
nent, composed of long, thick, slightly curved
spicules. Those features separate A. terezae on
the Brazilian coast, from Acanthochitona minuta
Leloup, 1980, which was also described from
Bahia State. Moreover, the type specimens seem
to be young, and our observation of larger size
specimens revealed that the sculpture of the teg-
mentum is different from that of the young speci-
mens, especially in morphology of the jugum
described above. The absence of any kind of type
specimen and its brief description based on prob-
ably young specimens, which could be applicable
to a number of other species, result in an unclear
identity and taxonomic confusion among closely
related congeners. Thus, the authors regard that
this situation fills all requirements proposed by
ICZN (Article 75) to designate the neotype. The
present material was collected in a location that
is close to the type locality, and possesses the fea-
tures discussed in the original description. Hence
we designate this specimen, MZSP 115203, as the
neotype.
Comparisons with other species
In A. terezae, the valves i, v and viii (post mucronal
area) are sculptured by elliptical nodules of simi-
lar size, while in A. brunoi, the nodules are 2 to
3 times larger in the marginal region in relation
to the apical region of the same valves; in A.
ciroi, the nodules are circular and up to 2 times
larger in the marginal region in relation to the
apical region; A. hemphilli shows reniform and
convex nodules, with aesthete channels in the
central region, and A. rhodea has cuneiform nod-
ules with aesthete channels distributed from the
central area to the margin; A. pygmaea shows
concave nodules with elongated oval shape
(remembering A. rhodea) with aesthete channels
distributed from the central area to the margin
of the nodules. The jugal areas of the interme-
diate valves, and the anteromucral area of valve
viii in A. terezae did not present column forma-
tion, as shown in the original description of A.
brunoi. Moreover, the jugal area in A. terezae is
nodulose, while in A. hemphilli and A. rhodea, it is
smooth.
Regarding body size, A. terezae is approxi-
mately 4 times larger than A. brunoi and A. ciroi.
There are differences between the radular teeth:
the central tooth of A. terezae is rectangular with
a constriction in the upper third of its length,
and the regions before and after this constriction
have the same width. In A. brunoi, there are no
constrictions, but a gradual decrease in width
towards the base, resulting in a subtriangular
shape; in A. ciroi, it is a short and broad. Finally,
the rachidian teeth in A. terezae showed a base 2
to 3 times wider than the apex. In A. brunoi, these
proportions are inverted.
The new records extend the range of A. terezae
212km northward (Morro do Pernambuco,
Bahia state) and 1002km southward (MD55 sta.,
Espirito Santo State) (Fig. 1).
acknowledgeMents
The authors are very grateful to Dr. Philippe
Bouchet for inviting us to study the MD55 mate-
rial housed at the MNHN, Paris. To José Coltro
Jr., Femorale, for providing the trip to Paris. To
Prof. Sergio Vanin for the taxonomical remarks.
Mariana Tupiniquins for sending the additional
material analyzed herein. Jeremy Dickens and
Daniel Cavallari for the English tips. This pro-
ject is partially supported by CNPq (Conselho
Nacional de Desenvolvimento Científico e
Tecnológico), proc # 557166/2009–8.
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