Troglomyces triandrus

Enghoff, Henrik & Santamaria, Sergi, 2015, Infectious intimacy and contaminated caves-three new species of ectoparasitic fungi (Ascomycota: Laboulbeniales) from blaniulid millipedes (Diplopoda: Julida) and inferences about their transmittal mechanisms, Organisms Diversity & Evolution (New York, N. Y.) 15 (2), pp. 249-263 : 258

Troglomyces triandrus

The distribution of thalli strongly suggests that transfer happens during courtship/copulation. Copulation in A. pallidus has not been described, but Mauriès (1969) studied the closely related species Blaniulus lorifer (Brolemann, 1921) . In B. lorifer , the male uses his strongly modified mandibles to grip the female’ s antennae before inserting his gonopods (modified legs on body ring 7) into the female gonopore (located on body ring 3), see Fig. 6 . Like in B. lorifer , and indeed most other species of Blaniulidae , the male mandibles of A. pallidus are modified: The basal and middle segment (cardo and stipes) of the three-segmented mandible each bear a projection, and the two projections in combination form a pair of parrot bill-like forceps, one on each side of the head ( Figs. 4 and 5 ). There is no reason to believe that courtship and copulation in A. pallidus differs from that observed in B. lorifer . The thalli of T. triandrus are strongly concentrated on exactly those body parts which come into contact during the millipedes’ ‘love kiss’: the male mandibles and the female antennae (and the head capsule at the base of the antennae), see Fig. 6 . This inference is supported by the fact that T. triandrus has never been found on an immature millipede nor has it been found on millipedes belonging to male-less, supposedly parthenogenetic populations. (Admittedly, the number of studied females from male-less populations is not very high, and T. triandrus is also absent from several male-rich populations, notably in Sweden.)

Figures

Fig. 6 Position of Troglomyces spp. on their blaniulid hosts, shown on a drawing of copulating blaniulids from Mauriès (1969). Left: T. triandrus on Archiboreoiulus pallidus—green squares thalli on male host, mainly on mandibles; red dots thalli on female host, mainly on and at base of antennae. Right: T. bilabiatus on Acipes sp.— green inverted triangles thalli on male host, mainly on ventral parts of body ring 7; red triangles: thalli on female host, mainly on ventral parts of body ring 3

Fig. 4 A freshly killed male Archiboreoiulus pallidus with a group of T. triandrus (arrow) on the right mandible. Inset: close-up of mandibular ‘parrot bill’ and fungi. Scale bar 0.5 mm

Fig. 5 Troglomyces spp. on their blaniulid millipede hosts (SEM images). a Archiboreoiulus pallidus male, front end, showing the parrot bill-like mandible and the anterior gonopods (modified legs of body ring 7). b Close-up of a group of T. triandrus lodged between the two mandibular processes (the diagnostic triseriate antheridia are clearly seen). c A. pallidus female, head, with a group of T. triandrus at the base of each antenna (circles). d Acipes atlanticus female, front end, with a group of T. bilabiatus ventrally on body ring 3 and a single thallus on body ring 4. e Close-up of area in rectangle in d, thalli indicated with arrows. f Close-up of a group of T. triandrus at the base of the antenna of an A. pallidus female (the diagnostic tri-seriate antheridia are clearly seen). ant antenna, md mandible, gp gonopod. Scale bars 0.1 mm (a, c, d, e), 0.01 mm (b, f)