Bach de Roca, Carmen

Gaju-Ricart, Miguel

Molero-Baltanás, Rafael

Notario-Muñoz, M. J.

Revistes Catalanes amb Accés Obert

O 1997 Museu de Zoologia 
Miscel.lania Zoologica 20.1 (1997) 119 
The antennal basiconic sensilla 
and taxonomy of Machilinus 
Silvestri, 1904 (Insecta, 
Apterygota, Microcoryphia) 
M. J. Notario-Muñoz, C. Bach de Roca, R. 
Molero-Baltanás & M. Gaju-Ricart 
Notario-Muñoz, M.  J . ,  Bach de Roca, C . ,  Molero-Baltanás, R .  & Gaju-Ricart, M . ,  1997. The antennal 
basiconic sensilla and taxonomy of Machilinus Silvestri, 1904 (Insecta, Apterygota, Microcoryphia). 
Misc. ZOO~., 20.1: 119-123. 
The antennal basiconic sensilla and taxonomy of  Machilinus Silvestri, 1904 (Insecta, Apterygota, 
Microcoryphia).- Some special antennal sensilla ('rosettenformige' and basiconica) of five species 
of Mach~fihus (Mei nertellidae): M .  casasecai, M .  helicopalpus, M .  kleinenbergi, M .  rupestris gallicus 
and M .  spinifrontis were studied. The distribution patterns of the sensilla are different for each 
examined species and identical in both sexes. The sensillogram thus provides a good taxonomic 
characteristic for their identification. 
Key words: Taxonomy, Antennal sensilla, Basiconic sensilla, Machilinus. 
(Rebut: 8 VI1 96; Acceptació condicional: 4 XI 96; Acc. definitiva: 17 XII 96) 
María José Notario-Muñoz, Rafael Molero-Baltanás & Miguel Gaju-Ricart, Depto. de Biología Animal 
(Zoología), Univ. Córdoba, 14005 Córdoba, España (Spain).- Carmen Bach de Roca, Depto. de 
Biología Animal, Vegetal y Ecología, Univ. Autónoma de Barcelona, Bellaterra 08193, Barcelona, 
España (Spain). 
This work was supported by Fauna Ibérica I I I  SEUI-DGICYT PB92-0121. 
l 
Notario-Muñoz et al. 
lntroduction 
The insects' antennae are provided wi th  
specialized sensilla which function, rnainly, 
as chaernoreceptors. Their nurnber and dis- 
tr ibution along the antennal flagellurn have 
been suggested as characteristics w i th  taxo- 
nomic ( L A R I N K , ~ ~ ~ ~ )  and phylogenetic 
(WALTHER, 1983) irnportance. 
The sensillograrns of sorne Machiloidea 
(Machilidae and Meinertellidae) were car- 
ried out  by BOCKHORST (1988) who studied 
the distribution of al1 sensilla Dresent in the 
antenna (chaetica, trichodea, basiconica, 
coeloconica and 'rosettenformige') w i t h  
optical and electron rnicroscopy. Using Scan- 
ning Electron Microscopy (SEM), BACH et al. 
(1986) and FANCIULLI et al. (1988) provided 
more data about the types of Microcoryphia 
antennal sensilla. 
The scales cover a great part o f  the 
Microcoryphia body. In rnost Machilidae, 
these scales are present al1 around the 
antenna, bu t  this i s  no t  so in the case of 
Meinertellidae. The study o f  sensilla is 
therefore easier. 
As fernales of Machilinus lack the sec- 
ondary sexual characters present in males, 
these cannot be identified at a specific 
leve1 in rnany cases. 
The aim o f  the present study was t o  
evaluate whether the distribution pattern 
o f  t h e  basiconic antennal  sensilla i n  
Machilinus can be used as a specific charac- 
ter and whether it remains immutable in 
males and fernales o f  a given species. 
Material and methods 
The study was carried o u t  w i t h  f ive 
Machilinus species. To give taxonomic sig- 
nificance and avoid differences related t o  
geographical distante, the studied rnate- 
rial was collected near description locality 
o f  each species. 
Studied material 
M. kleinenbergi (Giardina, 1900), 3 88 y 19, 
Siena (Italy) 25 Vlll 89 and 23 IX 95; M. 
helicopalpus Janetschek, 1954,8 88 y 5 99, 
Ávila (Spain) 10, 11 VI 95; M. rupestrisgallicus 
Bitsch, 1968,3$8 y 3 99 (paratypes) France: 
Draguignan 29VI 64and Roquebrun 6 VI1 58; 
M. casasecai Bach, 1974, 8 88 y 2 99, 
Lérida (Spain) 28 V 86; M. spinifrontis Bach, 
1984, 4 88' y 5 99, Jaén (Spain) 11 VI1 82 
and 10 X 82. 
The specimens were preserved wi th 70% 
alcohol. Their antennae were dissected and 
mounted wi th Tendeiro medium, the slides 
were dried and clarified in a heater at 35OC 
for 30 days. 
The slides were observed wi th  conven- 
tional optic microscopy or, when neces- 
sary, wi th differential interference contrast 
(Nomarsky). 
Like al1 insects, Microcoryphia antenna 
are cornposed o f  scape, pedicel and fla- 
gellum, the latter w i th  a variable number 
of annuli which, on  the distal part, are 
arranged in  clear groups called 'distal 
chains', also variable in  nurnber and sepa- 
rated by a narrow part. The distal chains 
o f  al1 Machilinus are composed o f  eight 
annuli except M. rupestris gallicus which 
has nine. 
The distal chains are enumerated from 
the apex t o  the scape (n, n-1, n-2, n-3, 
etc.). To identify each annuli of a given 
distal chain, they are enurnerated in the 
same way, the distal being number one and 
the basal number eight or nine (fig 1). The 
different kinds of sensilla are named wi th 
letters (A, B, C, etc.) preceded by the number 
o f  sensilla per annuli (IBZCID: one sensillum 
B and D and two  sensilla C). 
Results 
The sensilla studied are the basiconic and 
'rosettenformige'. Al1 different types are 
represented in figure 2. The nurnber and 
position o f  each one of them are indicated 
in table 1. 
The 'rosettenformige' sensillum i s  widely 
represented in  many Microcoryphia species 
and can be found in different parts of the 
body. In al1 stcidied species, only one 
sensillum per annuli has been found and is 
therefore not  included in  table 1. 
Another sensillurn present i n  al1 studied 
species is the B (fig. ZB), which like the 
remaining sensilla is basiconic. Only one 
sensillum has been found in the first annuli 
o f  each distal chain. It is srnall, sunken and 
cornpletely hidden, w i t h  only a srnall 
Miscel.lania Zoologica 20.1 (1997) 121 
rp::;: ;
8 n-1 1 8  n 1 
E P F - 
Fig. 1. Outline of Machilinus antenna: E. Scapus; F. Flagellum; n. Last distal chain; n- l .  
Penultimate distal chain; P. Pedicel; 1. Distal chain annuli 1; 8. Basal chain annuli 8. 
(Scale 0.05 mm.) 
Esquema de antena de Machilinus: E. Escapo; F: Flagelo; n. Última cadena distal; n - l .  
Penúltima cadena distal; P. Pedicelo; 1. Ani l lo  1 (distal); 8. Ani l lo 8 (basal). (Escala 
0,OS mm.) 
-A ~3 l ' /~{/- 
+&$=p 
A 
B @I 4 
bE & flG l?j 
Fig. 2. Special sensilla in Machilinus antennae: A. "rosetenformige" sensilla; B-H. 
Basiconic sensilla. (Scale 0.01 mm.) 
Sensilios especiales en las antenas de Machilinus: A. Sensilio en roseta; 8-H. 
Sensilios basicónicos. (Escala 0,01 mm.) 
cuticular opening t o  the outside. most frequent case; sometimes this number 
The C sensillum is the typical basiconic changes in different distal chains o f  the 
one (fig. 2C); It is found in al1 the species, same antenna. Moreover, as demonstrated 
but  its number and position changes. The by BACH et al. (1986) and FANCIULLI et al. 
annuli 3 always presents the highest num- (1988) using SEM, different types may be 
ber (between t w o  and four). The numbers found beneath its shape. 
expressed in table 1 correspond t o  the The D sensillum (fig. 2D) is very close in 
122 Notario-Muñoz et al. 
Table 1. Patterns o f  distribution o f  the sensilla in the studied species represented 
by means o f  the last two  distal chains (n and n-1). All annuli present a special 
sensilla (A), not  indicated because o f  its constancy. Annuli 6 t o  8-9 have been 
omit ted since they lack special basiconic sensilla: Mc. M. casasecai; Mh. M. 
helicopalpus; Mk. M. kleinenbergi; Mr. M. rupestris gallicus; Ms. M. spinifrontis. 
Patrones de distribución de los sensilios de las especies estudiadas, representadas 
mediante las dos últimas cadenas distales (n y n-1). Todos los anillos presentan 
sensilio A que no se ha incluido debido a su constancia. Se han omitido los anillos del 
6 a l  8-9 porque carecen de sensilios basicónicos especiales: Mc. M. casasecai; Mh. M. 
helicopalpus; Mk. M. kleinenbergi; Mr. M. rupestris gallicus; Ms. M. spinifrontis. 
Annuli n n-1 n n-1 n n-1 n n-1 n n-1 
3 1G2C 1G2C 1F3C 1F3C 3C 4C 4C 4C 1F2C IF2C 
- 
4 
5 IDIC IEIC IEIC I D  IDIC 1H 1H 1E IEIC 
shape t o  C but  i s  stronger. I t  has been 
found only in two  species M. kleinenbergi 
and M. casasecai. I t  is placed in a small 
cuticle depression. 
The sensillum E (fig. 2E) is present in M. 
helicopalpus and M. spinifrontis. I t  is simi- 
lar in shape t o  D but  shorter and quite 
broad, inserted into a relatively wide and 
deep cuticular depression. The sensillum t ip  
is always clearly seen outside. These two  
species present another sensillum (F) very 
close t o  E, but  narrower (fig. 2F). 
M. casasecai has a unique sensillum (G) 
not  found in  the remaining species (fig. 2G). 
The sensillum shape is like C but  is inserted 
in a deep narrow cuticular depression; i t s  
t ip  is practically at surface level. 
Finally M. rupestris gallicus has another 
typical sensillum (H) not  found in the other 
species (fig 2H). The sensillum shape is simi- 
lar t o  E o f  M. helicopalpus, but  closest t o  G 
o f  M. casasecai by i t s  position in a deep 
cuticular depression; i t s  t ip  never protrudes 
outside. 
All these sensilla are located in a con- 
crete position. As a result, the overall set 
provides the distribution pattern or sensi- 
llogram for each species. 
Sometimes the sensilla can appear thin- 
ner than usual. This can be due t o  altera- 
tions after the manipulation o f  the an- 
tenna. However, they can be precisely 
distinguished by their constant position and 
the characteristic cuticular base of each 
type. 
Curiously, the pattern implies not one, 
but  two  distal chains; so i s  a replication 
(n+n-1 = n-2+n-3 = n-4+n-5= etc). Every two  
distal chains represent the sensillogram for 
each species. 
The distribution partterns from table 1 
include only the last two  distal chains. 
Discussion 
In general the sensillograms expressed in 
table 1 are coincident wi th the results given 
by BOCKHORST (1988) though the author 
presents a lineal arrangement of al1 sensilla 
found, from the first t o  the last flagellum 
annuli. The differences wi th our results are 
related t o  the sencillum C which i s  consid- 
ered by the author as containing various 
Miscel.lania Zooloaica 20.1 (1997) 
subtypes. BACH et. al. (1986) and FANCIULLI et
al. (1988) found various types o f  sensilla C 
using SEM. Their cuticular surfaces may be 
rough or smooth. This type o f  sensillum, 
although differing in number and position 
among the species, does not  appear t o  be 
essential for the pattern, at least in the 
studied species, sensilla D, E, F, G and H 
being much more important. Only M.  
helicopalpus presents as characteristic a C 
sensillum on annuli 2. Once the sensillogram 
of al1 Machilinus species is known, it might 
be o f  interest t o  determine the differences 
between subtypes o f  sensillum C. 
BOCKHORST (1988) found differences be- 
tween sensilla o f  M. spinifrontis in males 
and females. This was not  so wi th our speci- 
mens, as we found the distribution pattern 
for each species t o  be perfectly coincident 
in  both sexes. Those differences are due 
without doubt t o  individual alterations of 
some specimen and t o  the low quantity o f  
material studied. 
In conclusion, not  only the kind o f  sen- 
silla are characteristic for some species, but 
also their distribution Dattern, which shows 
constancy for males, females'and subadult 
specimens. I t  would therefore seern that 
this taxonomic character should be included 
wi th the description o f  any new species. 
Resumen 
Los sensilios basicónicos de la antena y taxo- 
nomía de Machilinus Silvestri, 1904 (lnsecta, 
Apterygota, Microcoryphia) 
Se han estudiado los sensilios especiales de 
t ipo roseta "rosettenformige" y basicónicos 
que se hallan en las cadenas distales de las 
antenas de cinco especies de Machilinus: M. 
casasecai, M. helicopalpus, M. kleinenbergi, 
M. rupestris gallicus y M. spinifrontis. En 
todas las especies las cadenas distales cons- 
tan  de ocho anillos excepto las de M. 
rupestris gallicus que poseen nueve. Se han 
hallado siete tipos diferentes de sensilios 
basicóncos (fig. 2) de los cuales sólo uno 
aparece en la misma posición y número para 
todas las especies (sensilio B); los restantes 
tipos de sensilio, o bien son exclusivos de 
algunas especies o bien varían en posición y 
número. 
En la tabla 1 se da el patrón de distribu- 
ción (sensiliograma) de todas las especies 
estudiadas. Únicamente se indican los 
sensilios presentes en las dos últimas cade- 
nas distales, ya que, sa ha comprobado, 
que es el conjunto de dos cadenas lo  que 
constituye el sesiliograma, repitiéndose el 
mismo a lo  largo del flagelo. 
La importancia del hallazgo de esta 
característca radica en que el mismo sensi- 
liograma se encuentra tanto en machos, 
como en hembras, como en individuos ju- 
veniles (subadultos) permitiendo la identifi- 
cación específica de los ejemplares que ca- 
recen de caracteres sexuales secundarios 
(hembras y juveniles). 
Ref erences 
BACH, C., DALLAI, R., FANCIULLI, P. P. & GAJU, M., 
1986. Characteristics o f  some species o f  
Catamachilis (Insecta, Apterygota) ob- 
served under Scanning Electron Micro- 
scope. Redia, 69: 489-522. 
BOCKHORST , K. G., 1988. Sensillenmuster auf 
den Antennen verschiedener Machiliden 
(Insecta: Archaeognatha). Braunschw. 
naturkdl. Schr. 3(1): 137-1 70. 
FANCIULLI, P. P., BACH, C., DALLAI, R. & GAJU, M., 
1988. Morfo logía de la hembra de 
Machiloides tenuicornis Stach 1930, al mi- 
croscopio electrónico de barrido (Apte- 
rygota: Microcoryphia). Eos, 64: 63-71. 
LARINK, O., 1986. Pattern of Antennal Sensilla 
in some Lepismatidae (Insecta: Zygen- 
toma). 2nd Int. Seminar on  Apterygota: 
237-242. 
WALTHER, JR., 1983. Antennal Patterns o f  
Sensilla o f  the Hymenoptera. A complex 
Character of Phylogenetic Reconstruction. 
Verh. naturwiss. Ver. Harnburg (NF), 26: 
373-392. 


The antennal basiconic sensilia and taxonomy of Machilinus Silvestri, 1904 (Insecta, Apterygota, Microcoryphia)

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