Body size in the ant-associated isopod Platyarthrus hoffmannseggii is host-dependent

Abstract

Many symbionts live in association with different species. It can be expected that these distinct hosts might have a different effect on key life-history traits of the associated symbionts. Here, we compared the key trait body size of the obligatorily ant-associated isopod Platyarthrus hoffmannseggii collected in nests of two types of sympatric ant hosts. This isopod species showed surprisingly large differences in body size depending on type of host ant, with the head width of females and males associated with organic mound building red wood ants (RWAs) being, respectively, 1.30 and 1.17 times larger than isopods sympatrically living in earth nests of Lasius flavus. There was also a higher proportion of females in many RWA nests, but this pattern was not consistent across all nests. Genetic analyses and aggression trials did not reveal cryptic groups specialized to different hosts. Therefore, we argue that the isopods exhibit size plasticity because of different host nest conditions. Absence of host aggression and optimal abiotic conditions in RWA nests might promote a larger isopod body size. Overall, this study shows that the association of a symbiont with different hosts might induce phenotypic plasticity in a symbiont key trait.

Multiple phenotypic traits as triggers of host attacks towards ant symbionts: body size, morphological gestalt, and chemical mimicry accuracy

“…Several authors have suggested that body size also affects the interactions between social insects and their guests [ 2 , 4 , 13 , 14 , 43 , 68 , 69 ]. Parmentier et al recently provided the first quantitative evidence for this relationship in wood ant-associated guests ([ 70 , 71 ]; but see also [ 72 ]). In fact, most social insect guests appear to be smaller than their hosts and diminutive body size is common [ 2 , 4 , 13 , 14 ], likely impeding recognition and thus protecting the intruders from attacks by host workers [ 2 , 14 , 73 ].…”

“…In fact, most social insect guests appear to be smaller than their hosts and diminutive body size is common [ 2 , 4 , 13 , 14 ], likely impeding recognition and thus protecting the intruders from attacks by host workers [ 2 , 14 , 73 ]. However, body size has not been studied intensively as a predictor of host attacks [ 14 , 70 – 72 ], and it remains largely unclear whether this trait is indeed related to host tolerance.…”

Surprisingly high genetic divergence of the mitochondrial DNA barcode fragment (COI) within Central European woodlice species (Crustacea, Isopoda, Oniscidea)

“…1 ). It is a small, white, and blind oniscid isopod that is widely-distributed in Europe and strictly associated with various ant species (e.g., Mathes and Strouhal 1954 ; Gruner 1966 ; Parmentier et al 2017 ). A few other species are found in the Mediterranean region, e.g., Platyarthrus schoebli Budde-Lund, 1879 ( Garci and Cruz 1986 ), which can be easily differentiated from Platyarthrus hoffmannseggii .…”

Woodlice of Belgium: an annotated checklist and bibliography (Isopoda, Oniscidea)

“…Bibliography: Mac Leod (1880) , Moniez (1886) , Pelseneer (1886), Preudhomme de Borre (1886b) , Lameere (1895, 1897) , Maitland (1897), Schouteden (1901) , Bagnall (1907), Massart (1912) , Collart (1936) , Lameere (1938) , Adam and Leloup (1940) , Capart (1942), Polk and Van Oye (1956) , Polk (1957, 1959a,b) , Kersmaekers and Deroeck (1973) , Tavernier (1981) , Tavernier and Wouters (1989, 1991), Boon et al (1993) , Wouters et al (2000) , Dekoninck et al (2007) , Segers (2015), De Smedt et al (2017a) , Parmentier et al (2017) .…”