Reproduction, egg morphology and development observed in two Australian penicillate millipedes, Lophoturus queenslandicus (Lophoproctidae) and Phryssonotus novaehollandiae (Synxenidae) (Diplopoda)

Abstract

Lophoproctid and synxenid millipede species observed in this study showed clear differences in their sexual reproduction, including sperm web structure, egg morphology and development compared with species from Polyxenidae. Male Lophoturus queenslandicus (Lophoproctidae) produce a single spermatophore on a sperm web without signal threads due to their lack of silk-producing coxal glands. Females of this species lay fewer eggs and differ in their egg cluster arrangement, which includes nest trichomes for protection. Lophoproctid chorion has a thin protective membrane and the pupoid has fused papillae covering the entire anterior region and an aperture bordered by protective papillate sensilla is present at the apex of the pupoid. Lophoproctid millipedes have a comparatively short intermoult period between stadia. In contrast, male Phryssonotus novaehollandiae (Synxenidae) produce two spermatophores separated by a large gap on their sperm web, with signal threads that are less obvious. Synxenid chorion and pupoid stages were unique; the chorion was tough and thick and the pupoid had anterior projections without an aperture bordered by sensilla, unlike those observed in lophoproctid and polyxenid millipedes. This study extends knowledge of the reproduction of species from three major millipede families from the Suborder Polyxenida (Penicillata: Diplopoda). Additionally, the results indicate that the reproductive strategies of Australian lophoproctid and synxenid species are adapted to their harsh environment.