Appl. Entomol. Zool. 43 (2): 281–285 (2008) http://odokon.org/
Thermal requirement for development of Carpophilus marginellus (Coleoptera: Nitidulidae), a potential pollinator of cherimoya and atemoya trees (Magnoliales: Annonaceae)
Morio TSUKADA,1,* Daisuke TANAKA1 and Hirokazu HIGUCHI2 1 Insect Ecology Laboratory, Faculty of Bioresources, Mie University; Mie 514–8507, Japan 2 Laboratory of Tropical Agriculture, Faculty of Agriculture, Kyoto University; Kyoto 606–8502, Japan (Received 22 February 2007; Accepted 21 January 2008)
Abstract Carpophilus marginellus is a candidate pollinator of the subtropical orchard trees cherimoya and atemoya. We investi- gated the developmental period and adult size of this species at constant temperatures of 18, 20, 25, and 30°C as basic information for mass rearing and release in greenhouses as a pollinator. The photoperiod was 16-h light/8-h dark at all temperatures. The developmental period was shorter and the adult size was smaller at higher temperatures. Mortality was lowest at 25°C and highest at 30°C. The thermal threshold (developmental zero) ranged from 11.9 (female larvae) to 15.6°C (female pupae) among developmental stages and sexes. The thermal constant (total effective temperature) of the period from egg to adult emergence was ca. 292 degree-days.
Key words: Degree-days; developmental zero; adult size; Annona; beetle pollination
Such facilities are favorable for the use of mass- INTRODUCTION released insect pollinators, since the greenhouse The cherimoya, Annona cherimola Mill. (Mag- can prevent the insects from escaping. We have noliales: Annonaceae), is a subtropical orchard been studying visitors to cherimoya flowers in tree. Although it is self-compatible, autogamy is Japanese orchards for the purpose of finding suit- generally impossible because of protogynous di- able pollinators during the flowering season chogamy (Sanewski, 1991). This is a relatively (Tsukada et al., 2005b). Annona spp. floral differ- archaic plant that does not use bees as pollinators. entiation occurs year-round in their natural distri- Thus, hand pollination is used to obtain an ade- bution area. However, in Honshu, pruning in early quate fruit set, but this takes time and money spring results in full-blooming around June. We (Gazit et al., 1982; Richardson and Anderson, found several individuals of Carpophilus marginel- 1996). Several studies have been conducted to lus Motschulsky (Coleoptera: Nitidulidae) on the identify suitable pollinators of cherimoya and its flowers, among other species such as Mimemodes relative, atemoya (A. cherimola squamosa), to monstrosus (Reitter) (Rhizophagidae) and Hapton- reduce orchard labor. Nitidulid beetles are the main cus ocularis (Fairmaire) (Nitidulidae) during the visitors of Annona spp. flowers world widely flowering season. (Gazit et al., 1982; George et al., 1989; Nagel et We have already reported the developmental al., 1989; Nadel and Peña, 1994), and secondary characteristics of H. ocularis as a candidate polli- visitors include staphylinid beetles and Orius spp. nator (Tsukada et al., 2005a). However, high mor- (Hemiptera: Anthocoridae) (Caleca et al., 1996, tality at high temperatures limits its use in green- 1998; Palmeri and Longo, 1997). houses during summer (Higuchi et al., unpub- These fruit trees were introduced to the Japanese lished). This prompted us to investigate another main island, Honshu, two decades ago. They are candidate pollinator. Among the flower visitors in cultivated in greenhouses to avoid frost damage. Japan, the number of C. marginellus was second
*To whom correspondence should be addressed at: E-mail: [email protected] DOI: 10.1303/aez.2008.281
281 282 M. TSUKADA et al. largest, after M. monstrosus (Tsukada et al., 2005b). moya in an experimental orchard of Mie Univer- Both males and females enter the female-stage sity, central Japan. They were reared in plastic con- flowers and leave them during the male stage with tainers measuring 26 cm 18 cm 8 cm (height). much pollen on their bodies (unpublished data). Three holes of 4-cm diameter were made in the lid Therefore, we assume that they pollinate the plant. of each container and covered with a fine gauze, This sap beetle has a body length of ca. 3 mm which allowed sufficient ventilation but prevented (Hisamatsu, 1985), and is distributed widely in insects from escaping. Cut pineapple was periodi- warm regions from East Africa to Japan (Kirejt- cally supplied as food, and the bottom of the con- shuk, 1998). Females lay their eggs on rotting tainer was lined with autoclave-sterilized soil for fruits such as orange and pineapple. Larvae de- pupation. Water was sprayed as needed on the soil. velop there, and pass through three instars before The beetles were easily reared at 25°C in a 16-h pupation. Mature last-instar larvae wander about light/8-h dark (16L8D) photoperiod. before entering the soil, where they pupate. Larvae Development from egg to adult. The procedure also develop on ripened Annona fruits. However, for the rearing of insects was similar to that used Annona fruits usually ripen after harvest, so for H. ocularis (Tsukada et al., 2005a). The fe- C. marginellus is not likely to damage the fruit in males laid their eggs into the pineapple, but be- orchards. Also, even though some flower visitors, cause finding eggs there was extremely difficult, including nitidulid beetles, are known to injure we used the following procedure to obtain eggs. plant ovaries, which causes aesthetic damage to First, 52 pairs of male and female were prepared. some orchard fruits, this seems not to occur on the Each was allowed to oviposit into a cut pineapple cherimoya (personal observation). Thus, the use of in a 30-ml vial in a chamber kept at 18, 20, 25, or this species as a pollinator by mass release in 30°C under a 16L8D photoperiod. The opening of greenhouses is feasible. On the other hand, C. mar- the vial was plugged by cotton to allow moderate ginellus, as well as other Carpophilus species, can ventilation. The insects were then removed within a be pests of dried fruits and cereals, but adequate day and placed into a new vial with another piece pest management has not been established, because of pineapple for the next oviposition. This proce- of the lack of published data on their basic biology. dure was repeated until sufficient larvae were ob- To investigate the use of beetles as pollinators of tained. Each vial with the pineapple piece was kept the cherimoya, especially by mass rearing and at the same temperature, and the pieces were exam- release in greenhouse orchards, researchers must ined every day. When larvae were found, they were know their developmental characteristics. Among isolated and each was gently transferred to a 10-ml many abiotic environmental factors, circumstantial vial with a ca. 5 g pineapple piece as food and a temperature is one of the most crucial factors that piece of wet tissue paper as a pupation site. Usu- regulate the development of insects. Except at ally, there was no need to add another peace of extremely high or low temperatures, insects de- pineapple, but we added one when the food ap- velop faster and attain smaller adult size at higher peared insufficient. The tissue paper was ca. 0.4 g temperatures (Atkinson, 1994). Data of develop- in weight and contained ca. 1.2 ml of water, a suit- mental rate and adult size offers basic information able volume for the pupation of C. marginellus for the mass rearing of insects. In this study, we (unpublished data). The vials were examined every experimentally elucidated the thermal requirements day, and pupation date and adult emergence date and adult size of C. marginellus. Our results offer were recorded. The dates of oviposition and ap- basic information both for the use of C. marginel- pearance of new larvae (regarded as egg hatch) lus as a pollinator for cherimoya and other Annona were also recorded. The sex of each individual was plants, and for management of it as a pest of dried determined after adult eclosion by observation of fruits. the tip of the abdomen under a binocular micro- scope. Adult size. The emerged adults were individu- MATERIALS AND METHODS ally dried, and head width (distance between ante- Insect stock culture. The insects originated rior ends of the compound eye) was measured from feral individuals caught in the flowers of ate- using a micrometer under a binocular microscope. Development of Carpophilus marginellus 283
Table1.Developmental period (days) of C. marginellus at four temperatures. Mean SD
Temp. Sex (n) Egg Larva Pupa Total
18°C ? (44) 12.41 1.69 25.73 1.78 22.20 2.08 60.07 4.04 / (42) 12.76 1.49 25.36 1.48 22.00 2.54 59.64 3.99 20°C ? (35) 9.26 1.48 22.06 1.92 17.94 1.63 49.83 3.33 / (36) 8.78 1.17 21.81 2.07 18.75 2.59 49.28 3.78 25°C ? (46) 5.24 0.97 12.96 1.35 7.96 1.03 26.22 1.95 / (40) 5.20 0.91 12.75 1.33 7.68 1.10 25.63 1.90 30°C ? (27) 4.44 0.80 8.89 1.40 5.07 1.07 18.41 1.53 / (33) 4.48 0.94 9.15 1.28 4.79 1.05 18.45 1.62
Statistical procedures. The parameters of ther- Table2.Total effective temperature (K; degree-days) and mal requirements (i.e., thermal constant [K] and the developmental zero (T0) of C. marginellus. The data at 30°C were omitted from calculation of parameters of egg stage thermal threshold [T0]) were obtained from the regression of 1/D against T, where D is days Stage Sex r2 a KT required to complete a stage and T is temperature 0 (°C). These regressions were estimated from the Egg ? 0.8132 60.24 13.16 raw data, not from the means of each temperature. / 0.8398 59.52 13.22 The effect of temperature on mortality at larval and Larva ? 0.9040 158.73 12.37 pupal stages was analyzed using a log-linear / 0.9142 163.93 11.90 Pupa ? 0.8764 74.07 15.19 model. Adult size was analyzed using a GLM two- / 0.8422 67.11 15.58 way ANOVA followed by a Tukey-Kramer multiple comparison test. These and other statistical tests a r2 of the regression line of 1/D on temperature. were performed with the NCSS statistical package (NCSS, 1995).
RESULTS Among the three developmental stages exam- ined, the larval stage required the longest time and the egg stage the shortest (Table 1). All three stages required less time at higher temperatures in both sexes. However, the developmental time (D) of the egg stage at 30°C was longer than suggested by a linear relationship between developmental rate Fig. 1. Mortality of C. marginellus during larval and (1/D) and temperature. Thus, data for 30°C were pupal stages at different temperatures. omitted when regression was carried out to obtain the parameters K and T0. There was no difference cantly different from 0.5 at each temperature (bino- in 1/D from egg to adult between the sexes at 15, mial test, p 0.05). The mortality rate from egg to 20, or 25°C (ANCOVA with temperature being the adult was lowest at 25°C and highest at 30°C. The covariate, p 0.05; data at 30°C omitted). among-temperature variation in mortality was
T0 of both sexes was about 12°C at the larval attributed mostly to that during the pupal stage stage (Table 2), and above 13°C at the other two (Fig. 1). Temperature significantly affected mortal- stages and for the total developmental period from ity at the pupal stage (log-linear model, p 0.0195 egg to adult. K from egg to adult, obtained by sum- for the interaction), but not at the larval stage (p ming the value of three stages, was ca. 293 and 291 0.05). degree-days (DD) for male and female, respec- Head width was largest at 18°C, and decreased tively. significantly with increasing temperature in both The sex ratios of the adults were not signifi- sexes (Table 3; GLM, two-way ANOVA, p 284 M. TSUKADA et al.
Table3. Head width (mm) of adult C. marginellus reared at Other than the temperature itself among the rearing four temperatures. Mean SD (n) conditions, difference in humidity in the vials also might have affected the result. During the pupal Temperature ?/ stage we did not control the water content of the 18°C 0.759 0.008 (44) 0.760 0.008 (42) tissue paper not to disturb the insect. Therefore, 20°C 0.755 0.009 (35) 0.754 0.008 (36) evaporation rate of water via the cotton plug would 25°C 0.736 0.005 (46) 0.729 0.005 (40) be different among the temperature conditions, i.e., 30°C 0.714 0.008 (27) 0.718 0.007 (33) it is likely that at low temperature condition the water content of pupation site was higher and at high temperature it was lower than the optimal. 0.0024). Sex and interaction of sex and tempera- It is well known that in the favorable tempera- ture did not show significant effects (p 0.05). ture range, insects that develop at lower tempera- tures attain a larger size at eclosion (Atkinson, 1994). In this study, the adults were consistently DISCUSSION larger at lower temperatures. This also suggests The developmental period of each of the three that the temperatures we used are in the favorable stages was always longer at lower temperatures range, and C. marginellus follows the general rule than at higher temperatures, the same as in most on the relationship of body size and temperature. other ectotherms. However, at 30°C, the length of Although we did not examine the effect of body the egg period was longer than expected from a lin- size on fecundity and longevity, it is frequently ear regression of the other three temperatures. Fur- shown that larger individuals lay more eggs and thermore, at this temperature, mortality during the live longer (Sopow and Quiring, 1998; Rodriguez pupal stage was high. These results suggest detri- et al., 1999). Therefore, rearing this insect at lower mental effects of high temperature on develop- temperatures has a likely merit of larger fecundity. ment. It is likely that more serious detrimental Besides temperature, the density of the larvae and effects would occur above 30°C, since other Car- type of food also affect development. It is worth- pophilus species show that below 30°C the devel- while to carry out additional experiments to con- opmental rates increase as temperature increase, firm the best conditions for mass rearing of this but 32.5°C or over, the rates are mostly the same beetle. (James and Vogele, 2000). Considering that C. The developmental biology of Carpophilus spp. marginellus is distributed widely in warm regions has been studied by James and Vogele (2000). The of the world (Gillogly, 1982; Kirejtshuk, 1998), tol- thermal constant from egg to adult for three Car- erance to relatively high temperatures would be pophilus species ranged from 260.4 to 320.0 DD, expected. In addition, although the free-living and T0 ranged from 14.6 to 15.4°C under constant stages of this species would be directly exposed to temperature (James and Vogele, 2000). The ther- air temperature, the pupal stage in the soil would mal constant and threshold for C. marginellus ob- be somewhat insulated (Skinner et al., 2004), and tained here were similar to those of the congeneric larvae would choose an appropriate depth for pupa- species. On the other hand, H. ocularis has a tion according to the temperature (Dimou et al., smaller body and requires a lower cumulative tem- 2003). Thus, the detrimental effect of high temper- perature (Tsukada et al., 2005a). Another nitidulid ature on pupation under natural conditions might species, Librodor japonicus, with larger body size, be smaller than that determined in this study. requires ca. 800 DD until eclosion (Okada and The sex ratio of the emerged adults suggests that Miyatake, 2007). Thus, larger species tend to re- although temperatures affect the mortality rate, this quire more day-degrees in this family. effect is the same on both sexes. This result differs This study revealed developmental characteris- from that of H. ocularis, in which mortality of tics of C. marginellus that are indispensable for males tended to be high at low (15°C) and high mass rearing, but prerequisites for mass release (30°C) temperature (Tsukada et al., 2005a). The must yet be investigated. Considering that this species-specific characteristics that make such dif- species visits Annona flowers, we assume that ference between the two species are not known. mass-released insects will visit the flowers readily. Development of Carpophilus marginellus 285
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