Effects of starvation on reproduction of the predacious mite Neoseiulus californicus (Acari: Phytoseiidae)

Impact of starvation on paternal reproductive investment in Neoseiulus californicus

Neoseiulus californicus is an important biological control agent of small arthropod pests, widely used in preventive releases at low prey densities. Therefore, it is important to study reproductive investment of this species, both females and males, under environmental pressure of limited prey availability. Laboratory experiments were performed to investigate N. californicus male reproductive investment after short-time fasting or long-term starvation. When fasted for 36 h, males are still able to complete a single mating with no significant change in reproductive parameters of its mate. But the total mating duration became 24% longer, especially timing for the male to fill the first spermatheca of its mate increased by 35%. If daily food availability was less than 20% of demand, males were still able to mate until the end of life, but their fertility reduced after ca. the seventh mating. Mating of some males at the end of their lives are invalid, with their mates failing to oviposit. Overall, we summarized that reproductive investment demand for a single mating was low in N. californicus males, but its priority in energy allocation was high. When starved, males tried to guarantee their mating capability, but their fertility decreased gradually.

Ultrastructure of the male genital tract, spermatogenesis and spermatozoa of Hattena cometis Domrow (Acari: Gamasida: Ameroseiidae)

The ameroseiid mite Hattena cometis has a male genital system that consists of an unpaired, u-shaped testis and paired deferent ducts leading into an unpaired accessory genital gland and ejaculatory duct. The genital opening is located anteriorly immediately in front of the sternal shield. Spermatogenesis is simple, probably due to the haploid nature of the male. Eight stages of spermatogenesis could be roughly distinguished. Mature spermatozoa as found in the deferent duct lumen are peculiar in having a bisected nucleus and numerous peripheral flat chambers, which were formed from indentations of the plasmalemma. In inseminated females, spermatozoa were observed in the syncytial tissue of the sperm access system and in the somatic cells of the ovary. These spermatozoa have achieved a new structure, i.e., an electron-dense plate dividing the cell into two unequal halves. The dense plate has an intricate substructure. Its function is unknown. These sperm cells are considered to represent capacitated spermatozoa. The peripheral chambers are reduced in number inside the female. Similar sperm cells, containing a dense plate, were seen in vacuoles within the epithelium of the deferent duct of one male. These cells are evidently under destruction, but before being completely dissolved had undergone a development leading beyond that of the mature sperm cells found in the deferent duct. Apparently, entering the cell of the deferent duct epithelium or the syncytium tissue triggers the production of the dense plate (or the capacitation process). Our observations are compared with results obtained from other anactinotrichid Acari, mainly Gamasida, and confirm and complete the interpretation of the correlated evolution of components of gamasid reproductive systems.