New association between the mite Erythraeus sp. (Acari: Prostigmata: Parasitengona) and the psyllid Russelliana adunca (Hemiptera: Psylloidea)

The association between the ectoparasitic mite, Erythraeus Latreille (Acari: Prostigmata: Parasitengona) and the psyllid Russelliana adunca Burckhardt (Hemiptera: Psylloidea) is reported for the first time. Larval erythraeid mites are not common on psyllids, therefore this first report adds a new host association and widens the distribution of the mite in South America.

Psylloidea or jumping plant-lice are generally highly host specific plant sap sucking hemipterans. Hosts are mostly dicotyledonous plants on which the five larval instars complete their development (Burckhardt, 2008). Psyllidae is the largest family, with more than 1,300 species with a cosmopolitan distribution and a wide range of host families (Burckhardt, 2008;Ouvrard, 2021). In the New World, several species of psyllids are serious agricultural and forestry pests, such as species belonging to Cacopsylla pests of pear, and Russelliana solanicola Tuthill pest of potato (Percy 2014;Serbina & Burckhardt, 2017). Moreover, some psyllids transmit plant pathogens as Diaphorina citri Kuwayama vector for Candidatus Liberibacter in citrus (Halbert & Manjunath, 2004;Halbert & Núñez, 2004).
The Cohort Parasitengona comprises terrestrial and aquatic mites, whose main characteristic is the complex life-cycle (Proctor, 1998 Buenos Aires, Argentina. The psyllid was identified as R. adunca following the keys of Burckhardt (2008) and Serbina & Burckhardt, (2017).
Currently, the genus Russelliana includes 43 species restricted to the Neotropics, and they are associated with a surprisingly wide range of hosts from several plant families (Serbina & Burckhardt, 2017). Russelliana adunca is distributed in Bolivia, Chile and, in Argentina, it is known from Chubut province (Burckhardt et al., 2012;Serbina & Burckhardt, 2017;Baliotte et al., 2021). Here, the genus Russelliana and the species R. adunca are recorded for the first time from Neuquén province. In addition, the record in L. divaricata must be considered casual, because the adult was not found feeding and no other developmental stage of the species was found (Burckhardt et al, 2014;Ouvrard, 2021). It is important to continue with the sampling to obtain a more accurate association with the plant and to have more representatives of the psyllid, given that there are no females or nymphal stages.
The mite was identified as larva belonging of the genus Erythraeus and it was not fit with larval species of the genus worldwide key (Xu et al., 2019). No information about this genus in Argentina is available, nonetheless we mention some features that will help in future identifications: Body 352:175; two pairs of eyes on each side, dorsal scutum rounded and finely dotted Parasitengona mites are parasites of insects and arachnids or, exceptionally, free living, while adults and deutonymphs are predators of small arthropods (Salmane & Mąkol, 2018). Some parasitengone families (between them Erythraeidae) parasitize hemipterans of the Auchenorrhyncha, Heteroptera and Sternorrhyncha suborders (Stroiński et al., 2013). The genus Erythraeus Latreille comprises about 124 known species, with two Subgenera: Erythraeus Latreille and Zaracarus Southcott, mostly distributed in the old world, and in a few regions of the American continent (Peru, USA and Galapagos) (Mąkol & Wohltmann, 2012;Xu et al., 2019). Larvae of Erythraeus (Erythraeus) species were found associated with at least 29 hemipteran species belonging to nine families (Haitinger & Mehrnejad, 2017 (Haitlinger & Mehrnejad, 2017;Costa et al., 2019;Ouvrard, 2021).
The aim of this work is to report for the first time the association between the mite Erythraeus sp. (Acari: Prostigmata: Parasitengona) with the psyllid Russelliana adunca Burckhardt (Hemiptera: Psylloidea) in Argentina.
During a sampling on Larrea divaricata Cav. (Zygophyllaceae) in Añelo, Neuquén province, Argentina (38°19´18´´S; 68°44´45´´W, 396 m.a.s.l.), one reddish mite firmly attached by their chelicerae to the abdomen of a psyllid (Fig. 1) was collected. The samples were collected within the framework of the Baseline Study of Biodiversity in Areas of the Neuquén Basin, developed by Yacimientos Petrolíferos Fiscales S.A. (YPF S.A.) in October 5, 2019; a 3 m 2 plastic blanket was placed on the ground around the entire plant and the foliage was tapped with a stick. Then the material was collected from the blanket and stored in 70% ethanol. The mite was removed with a fine forceps and stored in 70% ethanol, then it was cleared in lactophenol for identification and mounted on a semipermanent slide in Hoyer's (Walter & Krantz, 2009). The terminology and abbreviations are adapted from Haitlinger & Saboori (1996). All measurements were taken from a slide-mounted specimen and are given in micrometers (μm); either as length or length: width. Abbreviations used in the text are: AL: length of anterolateral scutala, PL: length of posterolateral scutala, ASE: length of anterior sensillary seta of dorsal scutum and PSE: length of posterior sensillary seta of dorsal scutum.
The psyllid was preserved in 70% ethanol and one of its forewings was mounted in Canada balsam for the identification using a stereomicroscope Leica S8APO and a microscope Trinocular "Biotraza" XSZ146AT. The studied material was deposited in the collection of the División Entomología of the Museo de La Plata (MLP), (125:126), bearing AL (54), ASE (32). PL (32) and PSE (60) (Fig. 2), palp femur and palp genu with one barbed seta each; two pairs of sternalae setae, one of them between coxae I, and the other pair between coxae III (no setae between coxae II), between coxae II and III one pair of setae. Each coxa I-III with one seta (coxalae); all opisthosomatic setae are similar in shape and size (28; with barbs), but ventral are more slender than dorsal (38) (2019) key, it was not possible to advance in the determination of the species. However, we consider that the association between the mite Erythraeus sp. and R. adunca constitutes a valuable record for Argentina and especially for Neuquén, Patagonia.
The association reported herein widens the host list known for this parasite and represents the first record of the same in Argentina. It may promote further efforts regarding jumping plant lice-mite association studies.