Two new species of Zetzellia Oudemans (Acari: Stigmaeidae) that threaten the concept of genera: disgeneric marriage?
Author
Hernandes, Fabio A.
Author
Feres, Reinaldo J. F.
text
Zootaxa
2005
1048
27
44
journal article
50926
10.5281/zenodo.169935
5158d6ce-aa35-44f2-9272-7a4edbe812dc
11755326
169935
Zetzellia quasagistemas
Hernandes & Feres
sp. n.
(
Figs. 23–41
)
This species resembles
Z. yusti
Summers
in having dorsal shields smooth, two pairs of aggenital setae, tegument on venter and around dorsal shields slightly striated; prodorsal shield bearing 3 pairs of setae (
vi
,
ve
and
sci
), pairs
c2
and
d2
on small platelets, pairs
h1
and
h2
on the same terminal shield, tarsus IV with 7 setae. It differs from the latter in having the bases of pair
c1
completely fused with hysterosomal shield; the solenidion (15) on tarsus I is relatively shorter than in
Z. yusti
(23); dorsal setae
vi
,
ve
,
c1
,
c2
,
d1
,
d2
,
e1
and
e2
also shorter; tarsus I with 13 setae (rather than 12).
Female
(n=5). (
Figs. 23–28
).
Dorsum
. Dorsal shields smooth; prodorsal shield bearing 3 pairs of setae (
vi
,
ve
and
sci
); dorsal setae as in female
Z. agistzellia
sp. n.
;
Venter
. Ventral and anal setae as in female
Z. agistzellia
, 1 long genital pair (
g1
), extending to bases of
ps3
,
ps3
is short, thick and hairy;
ag1
is inserted on plate around anal opening;
ag2
is inserted on the striated tegument.
Gnathosoma
. As in female
Z. agistzellia
.
Legs
. Chaetotaxy (I–IV): coxae 2(1)122; trochanters 1111; femora 542 2; genua 3(1)100; tibiae 5(1)5(1)5(1)5(1); tarsi 12(1)9(1)7(1)7.
Developmental changes [from deutonymph female]: addition of 1 seta on trochanter IV and 1 genital seta (
g1
).
Male
(n=5). (
Figs. 30–35
).
Dorsum
. Dorsal shields smooth; prodorsal shield bearing 3 pairs of setae (
vi
,
ve
and
sci
); hysterosomal shield bearing 5 pairs of setae (
c1
,
d1
,
e1
,
e2
and
f1
); seta
d2
on small platelet; dorsal setae
e1
and
h1
greatly reduced, the shortest of dorsal setae.
Venter
. Ventral and anal setae as in
Z. agistzellia
sp. n.
; 1 pair of aggenitals;
ps1
short and thin, each inserted in a tubercle, being visible dorsally due to the curvature of this region.
Gnathosoma
. As in female.
Legs
. Chaetotaxy (I–IV): coxae 2(1)122; trochanters 1111; femora 5422; genua 3(1)100; tibiae 5(1)5(1)5(1)5(1); tarsi 12(2)9(2)7(1)7(1).
FIGURES 23–29
:
Zetzellia quasagistemas
sp. n.
(female) 23. dorsum, 24. anogenital region, ventral, 25. palp, 26–29. legs I–IV.
Developmental changes [from deutonymph male]: hysterosomal shield includes pair
f1
; dorsal seta
e1
reduces largely at this stage; addition of 1 seta on trochanter IV, and 1 solenidion on tarsi I, II and IV; aggenital setae unchanged.
FIGURES 30–36
:
Zetzellia quasagistemas
sp. n.
(male) 30. dorsum, 31. anogenital region, ventral, 32. palp, 33–36. legs I–IV.
Deutonymph female.
(n=2). (
Figs. 41–42
).
Dorsum
. Dorsal setae as in female;
Venter
. Ventral and aggenital setae as in female.
Gnathosoma
. As in female.
Legs
. Chaetotaxy (I–IV): coxae 2(1)122; trochanters 1110; femora 5422; genua 3(1)10 0; tibiae 5(1)5(1)5(1)5(1); tarsi 12(1)9(1)7(1)7.
Developmental changes [from protonymph]: addition of 2 setae on coxa IV, 1 seta on trochanters I, II and III, 1 seta on femora I and IV and on tarsus IV; addition of 1 pair of aggenital setae.
Deutonymph male.
(n=2). (
Fig. 43
).
Dorsum
. Dorsal setae as in female;
Venter
. Ventral setae as in female; 1 pair of aggenitals.
Gnathosoma
. As in female.
Legs
. Chaetotaxy (I–IV): coxae 2(1)122; trochanters 1110; femora 5422; genua 3(1)10 0; tibiae 5(1)5(1)5(1)5(1); tarsi 12(1)9(1)7(1)7.
Developmental changes [from protonymph]: same leg chaetotaxy as in deutonymph female; there is no addition in aggenital setae, that distinguishes this stage from deutonymph female; this condition remains in the adult male.
FIGURES 37–43
:
Zetzellia quasagistemas
sp. n.
(immatures) 37–38. Larva. 37. dorsum, 38. anogenital region. 39–40. Protonymph. 39. dorsum, 40. anogenital region. 41–42. Deutonymph female. 41. dorsum, 42. anogenital region. 42. Anogenital region of deutonymph male.
Protonymph
(n=2). (
Figs. 39–40
).
Dorsum
. Dorsal setae as in female.
Venter
. Ventral setae as in female; 1 pair of aggenitals.
Gnathosoma
. As in protonymph of
Z. agistzellia
.
Legs
. Chaetotaxy (I–IV): coxae 2(1)120; trochanters 0000; femora 442 1; genua 3(1)100; tibiae 5(1)5(1)5(1)5(1); tarsi 12(1)9(1)7(1)6.
Developmental changes [from larva]: addition of leg IV; addition of one ventral seta on coxae I and II, and two ventral setae on coxa III; addition of 1 pair of aggenital setae.
Larva
(n=3). (
Figs. 3738
).
Dorsum
. Prodorsal shield smooth, partly invaded by tegumental striae along median line; dorsal setae setting on isolated platelets, no hysterosomal shield formed; platelets bearing setae
e1
and
e2
fused; median transversal suture dividing prodorsum and hysterosoma.
Venter
. 2 pairs of ventral setae (
1a
and
3a
) between coxae II and III, respectively; 3 pairs of anal setae,
ps3
shortest of anals,
ps1
a little slender than other anals.
Gnathosoma
. As in larva
Z. agistzellia
.
Legs
. Chaetotaxy (I–IV): coxae 1(1)00; trochanters 000; femora 442; genua 2(1)10; tibiae 5(1)5(1) 5(1); tarsi 12(1)9(1)7(1).
Remarks
: This species inhabits mostly the base of rubber tree leaflets, in association with the mites
Lorryia formosa
Cooreman, 1958 (Tydeidae)
, preying on their eggs and immatures, and with
Tenuipalpus heveae
Baker
, 1945 (Tenuipalpidae)
(Hernandes & Feres, submitted). It was found associated with
Z. agistzellia
sp. n.
Etymology
: From Latin
quasi
, meaning almost, suchlike, and Latin
mas
, meaning male. The specific designation refers to the similarities of males of
Agistemus
concerning some dorsal aspects: pair
f1
born on the main shield, and pair
e1
reduced; the pair
d2
, however, is set on small platelets aside the main shield in males as much as in females.
Type
material
:
Holotype
female (n. 5.832) collected from
Hevea brasiliensis
Muell. Arg. (Euphorbiaceae)
,
February 6, 2002
, Cedral, São Paulo,
Brazil
.
Paratypes
:
4 females
,
5 males
, 2 deutonymph females, 2 deutonymph males, 2 protonymphs,
3 larvae
from the same host and
type
locality, collected from
May 2001
to
January 2003
.
Both species herein described appear to present some difficulties for their placement among stigmaeids. Females of
Zetzellia agistzellia
sp. n
, undoubtedly fit in
Zetzellia
, whereas males clearly fit under
Agistemus
. If only females or males had been found, they would certainly have been classified as
Zetzellia
or
Agistemus
, respectively. However, all stages were found together, and no females of
Agistemus
nor any “traditional” males of
Zetzellia
were found, and that fact allows us to conclude that they belong to the same species. Analysis of immature stages also adds more strength to this hypothesis, as we have found two kinds of deutonymphs: female, with dorsal arrangement of shields and genital setae as in the adult female (except seta
g1
, present only in adult females), and male, with dorsal shields and genital setae as in the adult male. In
Z. quasagistemas
sp. n
, females expressly fit under this genus, whereas males have the setae
f1
unusually inserted on the main plate, resulting in an additional pair on this shield. This latter character is often found in males of
Agistemus
. In this species, there are also two kinds of deutonymphs, which resemble females and males, respectively (
Figs. 41–43
).
This is not the first time these two genera have been the subject of discussion.
Wood (1967)
argued that the dorsal organization of platelets in
Zetzellia
has four different patterns, which exhibit a gradual change from 3 pairs of small median plates to a large median plate (= the hysterosomal shield). In that context, the genus
Agistemus
, which has a far more uniform arrangement, appears to represent a next step towards the integration of hysterosomal shield. Since both genera share many features and can only be distinguished by the location of seta
d2
(
Wood 1967
), Wood considered that the distinction was not enough to support a new genus,
Agistemus
. He solved this by suggesting the definition of
Zetzellia
to be enlarged to include all species of
Agistemus
. However, his suggestion was not accepted by most acarologists (
e.g.
Meyer 1969
,
Khanjani & Ueckermann 2002
), who continued to use the previous definition of
Summers (1960)
and
Gonzalez (1965)
.
Based on ontogenetic data,
Gonzalez (1965)
believed that
Agistemus
evolved from the
Z. maori
group of species.
Meyer (1969)
, however, suggested ontogenetic data could merely support that “
Zetzellia
is ancestral to
Agistemus
” (p. 256). The present authors believe that
Agistemus
probably originated from a
Zetzellia
like ancestor, which evolved a large median shield comprising 5 pairs of setae, including
d2
. Since
Zetzellia
spp. present heterogenous arrangements of dorsal shields, and if
Gonzalez (1965)
is right, that genus might be paraphyletic, with a group of species giving birth to a new genus,
Agistemus
.
The discovery of such species raises some problems concerning the genus concept among
Stigmaeidae
. Since we found two species which have features of both
Agistemus
and
Zetzellia
present in different sexes, maybe those features do not reflect a real degree of difference enough to split two genera, and should be under review.
Wood (1967)
mentioned another two species of
Zetzellia
,
Z. maori
Gonzalez (1965)
and
Z. oudemansi
Wood (1967)
, which have different organization of dorsal shields for females and males. Males of the two latter species resembles
Z. australis
in the aspect of dorsal shields.
Zetzellia malvinae
Matioli, Ueckermann & Oliveira (2002)
and
Z. graeciana
(
Gonzalez 1965
)
also have different dorsal organization for females and males.
It is an intriguing fact that, concerning two species that closely resemble
Z. agistzellia
sp. n
, namely
Z. gonzalezi
and
Z. silvicola
, only females were found, and it would be worthwhile to speculate on whether the males of those species also resemble the
Agistemus
like males of
Z. agistzellia
. Males of
Zetzellia quasagistemas
sp. n
, are unusual in having 5 pairs of setae on the hysterosomal shield. The presence of at most 4 pairs of setae was thought to be the rule in
Zetzellia
(
Summers 1966
)
. A remarkable feature of males of
Agistemus
is that the dorsal seta
f1
is borne on the hind margin of hysterosomal shield, and seta
e1
seems to be frequently reduced.
Zetzellia quasagistemas
also has those features. Unusually,
Agistemus tarsilobus
Flechtmann (1995)
appears to have that setae
f1
directly inserted on the tegument.
It is an unfortunate fact that only a few descriptions of
Zetzellia
spp. include details of males, e.g.
Z. mali
(Ewing, 1917)
,
Z. graeciana
,
Z. maori
,
Z. oudemansi
and
Z. malvinae
. Most species have been described based only on females, which is problematic given that a single species can show sex differences enough to possibly mislead taxonomists to erect new taxa. The discovery of more species with such sexually dimorphic features shall help to solve this puzzle, and a complete cladistic analysis of stigmaeid genera using molecular, morphological and ontogenetic characters should provide a clearer picture of the evolution of this family. Descriptions of immatures should also throw more light on this matter.