Abstract

   The wolf spider Pardosa pseudoannulata is a dominant predator in paddy
   ecosystem and an important biological control agent of rice pests.
   Temperature represents a primary factor influencing its biology and
   behavior, although the underlying molecular mechanisms remain unknown.
   To understand the response of P. pseudoannulata to temperature stress,
   we performed comparative transcriptome analyses of spider adults
   exposed to 10°C and 40°C for 12 h. We obtained 67,725 assembled
   unigenes, 21,765 of which were annotated in P. pseudoannulata
   transcriptome libraries, and identified 905 and 834 genes significantly
   up‐ or down‐regulated by temperature stress. Functional categorization
   revealed the differential regulation of transcription, signal
   transduction, and metabolism processes. Calcium signaling pathway and
   metabolic pathway involving respiratory chain components played
   important roles in adapting to low temperature, whereas at high
   temperature, oxidative phosphorylation and amino acid metabolism were
   critical. Differentially expressed ribosomal protein genes contributed
   to temperature stress adaptation, and heat shock genes were
   significantly up‐regulated. This study represents the first report of
   transcriptome identification related to the Araneae species in response
   to temperature stress. These results will greatly facilitate our
   understanding of the physiological and biochemical mechanisms of
   spiders in response to temperature stress.

   Keywords: Gene regulation, Pardosa pseudoannulata, temperature stress,
   transcriptome, wolf spider

Introduction

   In the paddy ecosystem, spiders are important natural predator and
   represent a natural control factor for paddy insect pests (Barrion and
   Litsinger [30]1995; Haiming [31]1996). The wolf spider Pardosa
   pseudoannulata (Fig. [32]1) (Araneae: Lycosidae) is a dominant
   predatory species widely distributed in the rice ecosystem of the East
   Asia (World Spider Catalog [33]2016) and plays an important role in
   regulating the population densities of rice insect pests (Zhang et al.
   [34]1995; Zhao [35]2001; Li et al. [36]2002). Wolf spiders thus serve
   as effective biological control agents in the development and
   implementation of integrated pest management with rice ecosystems
   (Zhang et al. [37]1996).

Figure 1.

   Figure 1
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   The female and male of Pardosa pseudoannulata in the field.

   The growth, development, survival, reproduction, and predatory behavior
   of P. pseudoannulata are significantly influenced by the ambient
   temperature in the rice ecosystems, which is often lower than 0°C in
   winter and higher than 40°C in summer (Sun et al. [39]2007).
   Comparatively, the optimal temperature of P. pseudoannulata is from
   20°C to 30°C, whereas the developmental threshold temperature of males
   and females are 10.49°C and 9.75°C respectively. For this species, the
   maximum egg number and mean hatchability occur at 25°C, and the optimum
   temperature for development through the juvenile stages is at 30°C
   (Wang et al. [40]1982; Zhao et al. [41]1989; Li and Jackson [42]1996).
   In addition, temperature significantly influences the intervals of
   oviposition, the number of egg sacs, the survival rate of larvae, and
   the adult life‐span (Zhao et al. [43]1989). When the temperature is
   lower than 10°C, the spiders cease to feed, grow, and develop, and at
   temperatures higher than 40°C, the spiders act slowly, and most remain
   under objects or hide inside soil holes (Wang et al. [44]1982). How
   this spider species adapts to the stress of temperature variation and
   has become the dominant species in this ecosystem is unknown, and few
   references are available regarding how temperatures influence the