Genetica (1973) 44:139-145

F U R T H E R S T U D I E S ON K A R Y O T Y P E S AND

SEX D E T E R M I N A T I O N OF P H Y T O S E I I D

MITES (ACARINA: MESOSTIGMATA)

M. WYSOKI

Division of Entomology, Institute of Plant Protection, The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel

Received and accepted A ugust x 5, ~972

Chromosome studies were made on embryonic tissues of eggs of 15 species of predaceous mites of the family Phytoseiidae belonging to six genera: Amblyseius Berlese, Seiulus Berlese, Typhlodromus Scheuten, Phytoseiulus Evans, Phytoseius Ribaga and Paragigagnathus Amitai et Grinberg. In 14 species, the chromosome numbers n = 4, 2n = 8 were found. In cytological studies of post-embryonic stages based on these results, the haplo-diploid (arrhenotokous) mechanism was established. In the species Amblyseius deleoni Muma et Denmark, which was found to be thelytokous, only meta- phases with 5 chromosomes were found.

Introduction

In our previous work (WYSOKI • SWIRSKI, 1968) we reported the

results of karyotype analysis of ten species of predaceous mites of the

family Phytoseiidae belonging to four different genera: Phytoseiulus

Evans, Iphiseius Berlese, Typhlodromus Scheuten and Amblyseius Berlese.

The present work presents a description of the chromosomes of

some more species of those genera already examined by us in the past,

as well as of certain addi t ional genera: Seiulus Berlese, Phytoseius Ribaga, Paragigagnathus Amita i et Grinberg.

Material and Methods

Embryonic somatic tissues were removed from mite eggs, par t ly

Contribution from the Volcani Center, Agricultural Research Organization, Bet Dagan, Israel. 1972 Series, No. 2178-E.

140 M. WYSOK1

T A B L E 1

THE ORIGIN AND CHROMOSOME NUMBERS OF THE PHYTOSEIID MITES STUDIED

S p e c i e s O r i g i n

A b n o r m a l

C h r o m o - N u m b e r of c h r o m o s o m e

s o m e eggs meta- c o u n t ;

N u m b e r phases No. of ce l l s

A mblyseius aberrans I s r a e l

O u d e m a n s

A mblyseius barkeri I s r a e l

H u g h e s

A rnblyseius chiapensis C o s t a

De L e o n R i c a

A mblyseius cucumeris I s r a e l

O u d e m a n s

* A mblyseius deleoni I s r a e l

M u m a e t D e n m a r k

A mblyseius sp. (VII ) I s r a e l

Typhlodromus contiguus H o n g

C h a n t K o n g

TypModromus drori I s r a e l

G r i n b e r g e t A m i t a i

Typhlodromus phialatus I s r a e l

A t h i a s

Typhlodromus porathi I s r a e l

S w i r s k i e t A m i t a i

Typhlodromus sternlichti I s r a e l

S w i r s k i e t A m i t a i

Typhlodromus sp. I s r a e l

Seiulus isotrichus I s r a e l

A t h i a s

Phytoseius /initimus I s r a e l

R i b a g a

**Phytoseiulus persimilis I s r a e l

A t h i a s

S ic i ly

2 n = 8 2 26 1 6 ( 4 ) ; 7 ( 1 ) ; 2 ( 1 )

n = 4 6 30

2n = 8 32 64 7 (6); 3 (2)

n = 4 16 34

2n = 8 I I 21 3 (I)

n = 4 6 17

2n = 8 12 23 7 (2); 6 (1)

n = 4 4 16

2n = 8 40 110 7 (3)

2n = 8 12 18 7 (2); 5 (I)

n = 4 3 16

2n = 8 4 26 7 (2); 2 (2)

n = 4 2 17

2n = 8 4 7

n = 4 1 6

2n=S I0 38 6(I);5(I);3(2)

n = 4 4 20

2n = 8 16 72 7 (3)

n = 4 7 64

2n = 8 15 58 7 (1); 3 (1)

n = 4 6 38

2n = 8 8 32 7 (I)

n = 4 4 20

2n = 8 6 27 7 (I)

n - - 4 4 15

2n = 8 24 I15 7 (5); 6 (1); 3 (3)

n = 4 16 96

2n = 8 13 75 7 (4)

n = 4 11 60

2n = 8 38 82 7 (3); 6 (3); 3 (5) n = 4 14 44

* T h e l y t o k y

** WYSOKI & SWIRSKI, 1968.

C Y T O L O G Y O F P H Y T O S E I I D M I T E S 141

obtained from laboratory cultures, while only A. aberrans was col-

lected under natural conditions from plant leaves highly infested with this predaceous mite. Permanent smear preparations were made ac-

cording to WYSOKI (1968) and histological preparations were fixed

in Bouin's fixative, stained with iron hematoxylin and mounted in Canada balsam.

Results

A list of the species studied and the results of karyological analysis

are given in Table 1. Their chromosomes are illustrated in Figures

1-27. Five representatives of the genus Amblyseius were found to have

a haploid number of 4 and a diploid number of 8 chromosomes, all of

them being acrocentric, the homologous chromosomes differing from each other only in size. All five are arrhenotokous.

One species, Amblyseius deleoni, which is similar to A. largoensis Muma, was found to be thelytokous. No males were found in this

species, virgin females establishing generations of progeny (cf. Tab. 2).

In A. largoensis, virgin females do not lay eggs (as is the case with

other Phytoseiidae mites) ; egg laying began only after the introduction of males. This species was found to have 4 and 8 chromosomes (WY-

SOKI & SWlRSKI, 1968); in a similar species 8 chromosomes were found

at metaphase only. Although males of A. largoensis copulated with

A. deleoni, t ransparent examinations of the mites showed that they

were not fertilized (S. AMITAI, personal communication).

TABLE 2

DEVELOPMENT OF SINGLE ISOLATED MITES, AND MEAN NUMBER OF EGGS PRO- DUCED BY VIRGIN FEMALES OF A M B L Y S E I U S DELEONI MUMA ET DENMARK

Generation Number of Number of maturing ovipositing Eggs/~/day females virgin females (range)

I 24 18 0.5-1.6

II 20 16 1.2-1.3

I [ I 12 till laying of first egg

142 M. WYSOKI

I n p rev ious work Phytoseiu lus persimil is f rom Is rae l was e x a m i n e d .

I n the p resen t work mi tes o r ig ina t i ng f rom Sici ly a n d d e s i g n a t e d A.

tardii L o m b a r d i n i , were e x ami n e d . Ch ro mosom a l ana lys i s of example s

of th i s m a t e r i a l f rom b o t h count r ies d id n o t show a n y di f ferences:

c ross -breeding was successful a n d the i r p r o g e n y were ferti le. The

i d e n t i t y of the two species was es tab l i shed b o t h morpho log ica l ly a n d

wi th the a id of c ross -breeding (ATHIAS-HENRIOT, vide KENNETT ~¢

CALTAGIRONE, 1968).

A s imi la r c o m p l e m e n t was seen in species of the gene ra Typhlodro-

mus , Se iu lus a n d Phytoseius , i.e., the same n u m b e r of acrocent r ic

ch romosomes were f o u n d (4-8), differ ing o n l y in size.

His to log ica l s tud ies were m a d e of females f rom several species wi th

the fol lowing o b s e r v a t i o n s : A . iudaicus Swirski et A m i t a i - 8 ch romo-

somes in th ree cases (in somat ic tissues), T. rhenanus (Oud) - once 4

a n d once 8 ch romosomes (in gonads) , S. isotrichus - twice 8 ch romo-

somes (in somat i c t issues), P h . / i n i t i m u s - once 4 (in gonads) a n d three

t imes 8 ch romosomes (in somat ic tissues).

I n smears p repa red f rom Paragignathus tamaricis A m i t a i et Gr in -

berg, n y m p h s were f o u n d to have 8 ch romosomes in th ree cases,

whereas ma le a d u l t s h ad 4 ch romosomes in six cases, a n d females once

4 a n d once 8 chromosomes .

I n all species a r e l a t i ve ly smal l n u m b e r of i ncomple t e m e t a p h a s e s

was found , w i th one or more chromosomes a b s e n t (Tab. 1). Th i s

p h e n o m e n o n was p r o b a b l y an ar t i fact . I n A . aberrans, cases of poly-

p lo idy were also found .

Figures 1-27. Photomicrographs of chromosome complements from egg smears of different phytoseiids: (1) A. aberrans, n = 4; (2) A. aberrans, 2n = 8; (3) A. barkeri, n = 4; (4) A. barkeri, 2n = 8; (5) A. chiapensis, n = 4; (6) A. chiapensis, 2n = 8; (7) A. cucumeris, n ~ 4; (8) A. cucumeris, 2n = 8; (9) A. deleoni, 2n = 8; (10) Amblyseius sp. (VII), n = 4; (11) Amblyseius sp. (VII), 2n = 8; (12) T. ~ontiguus, n = 4; (13) T. contig~us, 2n ~ 8; (14) T. drori, n = 4; (15) T. drori, 2n ~ 8; (16) T. phialatus, n ~ 4; (17) T. #hialatus, 2n = 8; (18) T. porathi, n = 4; (19) T. porathi, 211 = 8; (20) T. sternlichti, n = 4; (21) T. stern- lichti, 2n = 8; (22) Typhlodromus sp., n = 4; (23) Typhlodromus sp., 2n = 8; (24) S. isotrichus, n = 4; (25) S. isotrichus, 2n = 8; (26) Ph. finitimus, n = 4; (27) Ph. linitimus, 2n = 8.

CYTOLOGY OF P H Y T O S E I I D I~ITES 143

144 M. WYSOKI

Discussion

In previous works (HANSELL, MOLLISON & PUTMAN, 1964; TREAT, 1965) the number of chromosomes was found to be n = 4, 2n = 8,

except in Typhlodromus occidentalis Nesbitt, which had 3 and 6

chromosomes (WYsoKi & SWlRSKI, 1968). Dr~ W. HELLE (personal

communication) found a similar number of chromosomes in Typhlo- dromus longipilus Nesbitt. DAVIS (1970) claims that T. occidentalis and T. longipilus are very similar and suggests that they be cross-bred.

This was performed by KENNETT & CALTAGIRONE (I 970) (preliminary

communication from "Spider Mite Newsletter" No. 3, 1970). I t was

found that the two species were identical. Karyological studies

undertaken by Dr. Helle and the present authors support this view,

considering the exceptional number of chromosomes in both instances.

The same number of chromosomes was found in A. cucumeris by TREAT (1965) and the present authors.

Besides establishing the haplo-diploid (arrhenotokous) types, an

additional case of thelytoky was found in A. deleoni. Previous cases

of thelytoky were described in A. guatemalensis Chant (KENNETT,

1958) and in Clavidromus aff. jackmickleyi De Leon = Clavidromus transvaalensis Nesbitt (AMITAI, WYSOKI & SWlRSKI, 1969).

Considering the results obtained from the cytological and histo-

logical studies undertaken in the previous and present work, it can be

stated that the mites examined in this work are of the haplo-diploid

(arrhenotokous) type (except in one case of thelytoky in A. deleoni).

Grateful appreciation is extended to Prof. E. SWlRSKI for his interest and

advice in this research, to Dr. W. HELLE of the University of Amsterdam for information on Typhlodromus longipilus Nesbitt, and to Mr. S. AMITAI for information on Amblyseius deleoni Muma et Denmark.

REFERENCES

AMITAI, S., 1Y[. WYSOKI ~: E. SWIRSKI (1969). A case of thelytoky in a phytoseiid mite (Acarina: Mesostigmata), with cytological studies. Israel ]. agri¢. Res. 19: 49-52.

DAVIS, D. W. (1970). Variations in the anatomy of Typhlodromus occidentalis (Acarina: Phytoseiidae). Ann. Ent. Soc. Am. 63: 696-699.

HANSELL, R. J. C., •. M. MOLLISON & W. L. PUTMAN (19(2~4). A cytological demonstration of arrhenotoky in three mites of the family Phytoseiidae. Chromosoma 15: 562-567.

CYTOLOGY OF PHYTOSEIID MITES 145

KZNNETT, C. E, (1958}. Some predaceous mites of the subfamilies Phytos~iinae and Aceose]inae (Acarina: Phytoseiidae, Aceosefidae) from Central Cali- fornia, with description of new species../Inn, Ent. Soc. Am. 51 : 471-479.

KENNETT, C. E. & L. E. CALTAGIRONE (1968). Biosystematics of Phytoseiulus persimilis Athias-Henriot (Acarina: Phfloseiidae). Acavotogia 10: 563-577.

TREAT, A- E. (1965)- Sex dist inctive chromatin and the frequency of males in the moth ear mite. Jl. N.Y. ent. Soc, 73: 12-18.

W~csoxI, M. (1968). A smear method for making permanent mounts of the metaphase chromosomes in eggs of phytoseiid mites (Acarina: Phytoseiidae). Israel J. E•t. 3: 119-122.

WxzsoKi, M. & E. SWIRSKI (1968). Karyotypes and sex determinat ion of ten species of phytoseiid mites (Acarina : Mesostigmata), Genetica 39 : 220--228,