Gamasellodes (Moraes et al., 2016)

De Castro, Matheus C., Barros, Ávyla R. A., De Azevedo, Emiliano B., Britto, Erika P. J., Castilho, Raphael C. & De Moraes, Gilberto J., 2020, A new species of Gamasellodes Athias-Henriot (Mesostigmata: Ascidae) from Brazil and a key to the world species of the genus, Zootaxa 4801 (2), pp. 291-300 : 297-298

Key to the world species of Gamasellodes , based on adult females

The preparation of a key of this type is a challenge, given that many of the available descriptions are not sufficiently detailed for an adequate recognition of the species. A revision of the Gamasellodes is considered highly desirable. The main objective of the present key is to help the separation of described species based on what is available in the literature. Care was taken to avoid taking into consideration characters that could be more easily overlooked, as absence of structures common for species of the genus, as summarised by Moraes et al. (2016).

Gamasellodes eusetosus ( Karg, 2007) has some odd characteristics for a species of this genus, especially the relatively broad dorsal and ventral shield in relation to other species of the genus, the distinctly reticulate sternal and ventrianal shields, the close genital and ventrianal shields, the absence of differentiated presternal region and the insertion of S 4 and S 5 on small protuberances. This species was originally described in Leioseius Berlese , but in the key to ascid genera provided by Moraes et al. (2016), it keys out as a Gamasellodes , genus to which it was transferred in that publication. That species is also included in the subsequent key.

The original description of Gamasellodes bicolor ( Berlese, 1918) is not sufficiently detailed. In the construction of the key, we based ourselves on the redescription provided by Bernhard (1963).

1. With anal shield (bearing only circumanal setae)............................................................. 2

- With ventrianal shield, bearing 3–4 pairs of setae in addition to circumanal setae................................... 3

2. Opisthonotal shield with 14 pairs of setae (S 1 absent); Z5 long, whip-like, longer than distance to seta of the same type on op- posite side; peritreme extending anteriorly to anterior margin of coxa I; dorsal shields strongly reticulate; anal shield oval............................................................................. G. ericae Walter, 2003 ; Australia

- Opisthonotal shield with 15 pairs of setae (S 1 present); Z5 shorter than distance to seta of the same type on opposite side; peri- treme extending anteriorly to level of coxa II; dorsal shields smooth over most of their extent, striate laterally and over anterior margin of podonotal shield; anal shield bell-shaped.................... G. tatricus Gwiazdowicz & Walter, 2005 ; Poland

3. Seta J 4 absent; with a transverse curved line about parallel to the anterior margin of podonotal shield, anteriad of j 3– z 2; with an undulate line anteriad of J 5– Z 5....................... G. andinus Rueda-Ramirez, Varela & Moraes, 2016 ; Colombia

- Seta J 4 present; with or without a transverse curved line about parallel to the anterior margin of podonotal shield, anteriad of j 3– z 2; ornamentation of opisthonotal shield variable.......................................................... 4

4. Ventrianal shield with three pairs of setae in addition to circumanal setae......................................... 5

- Ventrianal shield with four pairs of setae in addition to circumanal setae.......................................... 7

5. Unsclerotised cuticle along lateral margins of opisthonotal shield with two pairs of R setae; unsclerotised cuticle of the opistho- gaster with three pairs of setae (Jv 1, Zv 1 and Zv 2)................................ G. lentiformis Tseng, 1989 ; Taiwan

- Unsclerotised cuticle along lateral margins of opisthonotal shield with 6–7 pairs of R/UR setae; unsclerotised cuticle of the opisthogaster with 5–6 pairs of setae (Jv 1, Jv 3 and Zv 1– Zv 3; Zv 4 present or absent)................................. 6

6. Anterior region of epistome with three distally denticulate projections; seta z 1 present....... G. claudiae Walter, 2003 ; USA

- Anterior region of epistome with three pointed and smooth projections; seta z 1 absent.. G. hildae Jordaan, 1988 ; South Africa

7. Peritreme short, extending anteriorly at most to level of r 3..................................................... 8

- Peritreme extending anteriorly at least to level of s 1......................................................... 11

8. Peritreme extending anteriorly only to level of r 5; podonotal and opisthonotal shields with many wavy, irregularly oriented lines............................................ G. intermedius Rueda-Ramírez, Varela & Moraes, 2016 ; Colombia

- Peritreme extending anteriorly to level of r 3; podonotal and opisthonotal shield mostly smooth, with scant lines or puctation. ................................................................................................... 9

9. Seta s1 on dorsal shield; seta r 3 about three times as long as r 2; epistome with lateral projections distally trifid................................................................................. G. minor Athias-Henriot 1961 ; Algeria

- Seta s1 on unsclerotised cuticle; seta r 3 about as long as r 2; epistome with lateral projections sharp-tipped............. 10

10. Distance between posterior margin of genital shield and anterior margin of ventrianal shield less than half maximum width of genital shield; with a pair of transverse, slightly arched lines between j 4– z 4................................................................................................ G. insignis ( Hirschmann, 1962) ; type locality not stated

- Distance between posterior margin of genital shield and anterior margin of ventrianal shield more than maximum width of genital shield; without arched lines between j 4– z 4........................ G. zaheri Nasr, 1986 ; Egypt (in Zaher, 1986)

11. Anterior region of epistome with two projections; posterior region of genital shield rounded; podonotal shield smooth................................................................... G. sternalis Bhattacharyya & Sanyal, 2003 ; India

- Anterior region of epistome with three projections; posterior region of genital shield rounded or truncate; podonotal shield smooth or ornamented................................................................................ 12

12. Setae S 4 and S 5 inserted on small tubercles; sternal and ventrianal shields reticulate; sternal shield slightly longer than wide; without distinct lightly sclerotised, punctate presternal region................. G. eusetosus ( Karg, 2007) ; Lesser Antilles

- Setae S 4 and S 5 not inserted on tubercles; sternal and ventrianal shields not reticulate; sternal shield distinctly longer than wide; usually with distinct lightly sclerotised presternal region (not distinctly shown in the descriptions of G. andhraensis , G. vulgatior and G. seminudus )............................................................................ 13

13. With a single pair of R setae (R 1) on unsclerotised cuticle laterad of opisthonotal shield; many dorsal shield setae spine-like; central anterior projection of epistome denticulate, with distinctly broader base than the sharp and smooth lateral projections.............................................................. G. spinosus Bhattacharyya & Sanyal, 2003 ; India

- With more than one pair of R setae on unsclerotised cuticle laterad of opisthonotal shield; dorsal shield setae not spine-like; the three sharp anterior projections of epistome usually of similar sizes and smooth [except in G. bicolor (Berlese) ]......... 14

14. With two pairs of R setae on unsclerotised cuticle laterad of opisthonotal shield................................... 15

- With more than two pairs of R setae on unsclerotised cuticle laterad of opisthonotal shield.......................... 16

15. Setae st 1– st 3 of similar lengths; setae J 1– J 5 of similar lengths; with a single pair of metapodal plates..................................................................................... G. andhraensis Bhattacharyya, 2003 ; India

- Setae st 1 and st 3 of similar lengths, much shorter than st 2; setae J 3 and J 4 much shorter than other J setae; with two pairs of metapodal plates.............................................. G. islandicus Bhattacharyya & Sanyal, 2003 ; India

16. Podonotal and opisthonotal setae of about uniform length, tiny, with Z 5 only slightly longer than other setae and much shorter than distance to base of J 5; genital shield posteriorly truncate; ventrianal shield with anterior margin uniformly arched............................................................................... G. vermivorax Walter, 1987 ; USA

- Not all podonotal and opisthonotal setae tiny; at least Z 5 distinctly longer than others and at least as long as distance to base of J 5; posterior region of genital shield and anterior margin of ventrianal shield variable.............................. 17

17. Seta Jv 5 about twice as long as post-anal seta; Z 2 more than half as long as distance to base of Z 3........................................................................................ G. vulgatior Athias-Henriot, 1961 ; Algeria

– Seta Jv 5 shorter to slightly longer than post-anal seta; Z 2 less than half as long as distance to base of Z 3 (if longer, in G. adri- anae, then with only three pairs of setae on unsclerotised cuticle laterad of opisthonotal shield)...................... 18

18. With only three pairs of setae on unsclerotised cuticle laterad of opisthonotal shield................................ 19

- With more than three pairs of setae on unsclerotised cuticle laterad of opisthonotal shield........................... 20

19. Setae Z 2– Z 4 about half as long as distance to base of subsequent setae in the series; except for Jv 2, ventrianal setae tiny, so that para-anal setae about as long as distance to margin of anal opening, Jv 4 and Jv 5 shorter than distance to each other and post-anal shorter than distance to anal opening; z 1 about half as long as j 1....................... G. garmani Hurlbutt, 1970 ; USA

- Setae Z 2– Z 4 more than half as long as distance to base of subsequent setae in the series; ventrianal setae not tiny, so that para- anal setae longer than distance to anal opening, Jv 4 and Jv 5 about as long as distance to each other and post-anal almost as long as distance to anal opening; z 1 about 2/3 as long as j 1............................. G. adrianae Walter, 2003 ; Australia

20. Anterior margin of ventrianal shield about transversely straight between bases of Zv 2 setae.......................... 21

- Anterior margin of ventrianal shield about uniformly arched between bases of Zv 2 setae............................ 22

21. With four pairs of setae on unsclerotised cuticle laterad of opisthonotal shield; j 1 of length comparable to other podonotal setae; opisthonotal shield with scant ornamentation behind J 3– J 4........................ G. rectiventris Lindquist, 1971 ; USA

- With 7–8 pairs of setae on unsclerotised cuticle laterad of opisthonotal shield; j 1 much shorter than other podonotal setae; opis- thonotal shield lightly punctate-reticulate laterad of J 1– J 3 and strongly reticulate behind J 3 and Z 3............................................................................. G. plaire Halliday, Walter & Lindquist, 1998 ; Australia

22. Anterior and posterior margins of ventrianal shield undulate (almost serrate); Jv 2 distinctly shorter than Jv 3................................................................................. G. seminudus ( Ryke, 1962) ; South Africa

- Anterior and posterior margins of ventrianal shield not undulate; Jv 2 longer than Jv 3............................... 23

23. Seta Z 5 about as long as distance to base of J 5; ornamentation between J 4 and J 5 represented by a pair of ladder-like structures connected posteriorly by an arched undulating line.................................. G. bicolor ( Berlese, 1918) ; Italy

- Seta Z 5 distinctly longer than distance to base of J 5; ornamentation between J 4 and J 5 different...................... 24

24. Setae r 4 and r 5 absent................................................................................ 25

- Seta r 4 and r 5 present................................................................................. 26

25. Opisthonotal shield with an arched and undulating line connecting bases of both Z 4 setae; Jv 2 anteromediad of Jv 3.................................................................................. G. novibicolor Ma, 2005 ; China

- Opisthonotal shield smooth; Jv 2 mediad or posteromediad of Jv 3................... G. changjiangensis Ma, 2008 ; China

26. Seta Z 3 about as long as distance to base of Z 4; ornamention of opisthonotal shield consisting of scant lines between bases of J 1 and J 2 and posteriad of J 4; with a single pair of ellipsoidal metapodal platelets....................................................................................... G. magniventris Mineiro, Lindquist & Moraes, 2009 ; Brazil

- Seta Z 3 distinctly shorter than distance to base of Z 4; most of opisthonotal shield with very fine and barely noticeable puncta- tion, reticulate in region between J 4, J 5 and Z 4; with two pairs of elongate metapodal plates......................................................................... Gamasellodes lavafesii Castro, Azevedo & Castilho sp. nov.; Brazil