Differentiation of male reproductive system inOryctes rhinoceros (Coleoptera: Scarabaeidae)

Abstract

The male reproductive system of adult Oryctes rhinoceros consists of a pair of testes with 6 follicles in each, connected to vasa deferentia by small vasa efferentia, a pair of accessory glands, a median ejaculatory duct and a chitinous intromittent organ. The differentiation of these structures in the successive instars is described in detail. In the first. second and early third (final) instar larvae the reproductive system is rudimentary consisting of a pair of testes (each testis is a rounded aggregate of 6 follicles held together in a connective tissue sheath), a pair of delicate ducts or the vasa deferentia connected to 'genital disc' at the mid-ventral aspect of the 9th abdominal sternite. A chitinous plate makes its appearance in the 'genital disc' of second instar and is discarded alongwith prepupal exuvium. In the pupa, each testicular follicle gets separated to independent disc shaped organ. The ejaculatory duct and accessory glands differentiate from the distal part of 'genital disc' whereas the proximal part gives rise to the intromittent organ. Definitive spermatogonia differentiate in the late third instar larval testis. Spermatocysts and meiotic figures are seen only in the pupal stage and spermiogenesis after adult emergence. Sperm bundles are noticed only in a 2-4·day old adult. Accessory glands release secretion in 10-14-day old adult. Gradual degeneration of testis and ducts is observed in the adults from the third month onwards.

Effects of the Insect Growth Regulator, Methoprene, onOnthophagus taurus(Coleoptera: Scarabaeidae)

“…When applied to ventral abdominal segments of male pupae of Oryctes rhinoceros L., methoprene (20, 50, and 100 g or Ϸ2.5, 6.25, and 12.5 ppm) inhibited normal development of the male reproductive system (Jacob 1989), whereas in this study, topical methoprene application to sexually mature O. taurus adults did not seem to inhibit their reproductive ability. In addition, rhinoceros beetle pupae died after applying methoprene topically or through injection at 125, 25, and 5 ppm (Dhondt et al 1976).…”

“…However, this study showed that methoprene in the manure at a higher concentration (4.5 ppm) reduced feeding by O. taurus progeny. This was not surprising because topical application of methoprene resulted in inhibited normal male reproductive development (Jacob 1989) or pupal death in O. rhinoceros (Dhondt et al 1976). …”

Age‐specific sensitivity of sperm length and testes size to developmental temperature in the bruchid beetle

“…These different thermal response pathways could act on different developmental stages. The early stages of larval development tend to be associated with gonadal differentiation whilst the latter stages of larval development are associated with testicular differentiation and spermatogenesis (Jacob, 1989; Friedländer et al, 2005). In Drosophila, primordial germ cells and somatic precursor cells coalesce to form an early gonad around stage 12–14 (~12 h following fertilization), with testes development largely complete by the end of embryogenesis (Clark et al ., 2007; Whitworth et al ., 2012).…”

Discovery of a complex sclerotized sperm pump in Monotomidae (Coleoptera): Functional morphology and phylogenetic value

“…The male reproductive organs were studied in detail in the archostematan beetle Tetraphalerus bruchi Heller, and no specialized section of dej was found (Hünefeld et al, 2011); and such structures are also unknown in Adephaga (e.g., Sasakawa, 2007; Schubert et al, 2017). Within Polyphaga, a plesiomorphic dej is known among Scarabaeoidea (Scarabaeoidae: Jacob, 1989); and Tenebrionoidea (Meloidae: Muzzi et al, 2020; Tenebrionidae: Hopkins et al, 1993). Plesiomorphic dej was also found in certain groups of the polyphagan Chrysomelidae (Chrysomeloidea), as in Criocerinae (Matsumura & Suzuki, 2008), but in Donaciinae a distinct swelling of dej is present (Matsumura & Suzuki, 2008).…”

“…Considering the remarkable size of the pump (Figure 1 organs were studied in detail in the archostematan beetle Tetraphalerus bruchi Heller, and no specialized section of dej was found (Hünefeld et al, 2011); and such structures are also unknown in Adephaga (e.g., Sasakawa, 2007;Schubert et al, 2017). Within Polyphaga, a plesiomorphic dej is known among Scarabaeoidea (Scarabaeoidae: Jacob, 1989); and Tenebrionoidea (Meloidae: Muzzi et al, 2020;Tenebrionidae: Hopkins et al, 1993).…”