Neomisticius platypi n. sp. and N. variabilis n. sp. (Tylenchomorpha: Anguinidae) from dead oak trees in Japan

Summary Two new Neomisticius species, typologically and phylogenetically close to each other, are described and illustrated from dead Quercus trees and an ambrosia beetle, Platypus quercivorus. The two species share some stylet morphological characteristics, namely, they both possess a long conus occupying more than half of the total stylet length, a long crustaformeria composed of more than 160 cells (eight rows of more than 20 cells each), and a short and broad female tail with a digitate tip. They are distinguished from each other by N. variabilis n. sp. having a wide, spindle-shaped male bursa with a blunt terminus and N. platypi n. sp. having an oval bursa with a rounded terminus. In addition, the males and females of both species have three large rectal glands and the posterior end of the male testis (distal end of the vas deferens) bears three cells that seemingly function as a valve between the vas deferens and the cloacal tube. These characteristics have not been reported in other tylenchids. Currently, the genus contains only three species: the two new species and N. rhizomorphoides, which has a normal stylet with a short conus, a short crustaformeria, and lacks rectal glands and valve cells in the vas deferens. Therefore, the two new species are readily distinguished from N. rhizomorphoides and, based on the previous definition, may even represent a new genus. However, considering their phylogenetic closeness and biological similarities (e.g., association with ambrosia beetles), the generic definition of Neomisticius was emended to include these new species.

Electrophysiological Responses of Bactrocera kraussi (Hardy) (Tephritidae) to Rectal Gland Secretions and Headspace Volatiles Emitted by Conspecific Males and Females

Pheromones are biologically important in fruit fly mating systems, and also have potential applications as attractants or mating disrupters for pest management. Bactrocera kraussi (Hardy) (Diptera: Tephritidae) is a polyphagous pest fruit fly for which the chemical profile of rectal glands is available for males but not for females. There have been no studies of the volatile emissions of either sex or of electrophysiological responses to these compounds. The present study (i) establishes the chemical profiles of rectal gland contents and volatiles emitted by both sexes of B. kraussi by gas chromatography–mass spectrometry (GC–MS) and (ii) evaluates the detection of the identified compounds by gas chromatography–electroantennogram detection (GC–EAD) and –electropalpogram detection (GC–EPD). Sixteen compounds are identified in the rectal glands of male B. kraussi and 29 compounds are identified in the rectal glands of females. Of these compounds, 5 were detected in the headspace of males and 13 were detected in the headspace of females. GC–EPD assays recorded strong signals in both sexes against (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-ethyl-7-mehtyl-1,6-dioxaspiro[4.5]decane isomer 2, (E,Z)/(Z,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, and (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane. Male antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-methyl-6-pentyl-3,4-dihydro-2H-pyran, 6-hexyl-2-methyl-3,4-dihydro-2H-pyran, 6-oxononan-1-ol, ethyl dodecanoate, ethyl tetradecanoate and ethyl (Z)-hexadec-9-enoate, whereas female antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and 2-methyl-6-pentyl-3,4-dihydro-2H-pyran only. These compounds are candidates as pheromones mediating sexual interactions in B. kraussi.

Sugar uptake, metabolism, and chloride secretion in the rectal gland of the spiny dogfish Squalus acanthias

The rectal gland of the spiny dogfish Squalus acanthias secretes a salt solution isosmotic with plasma that maintains the salt homeostasis of the fish. It secretes salt against an electrochemical gradient that requires the expenditure of energy. Isolated rectal glands perfused without glucose secrete salt, albeit at a rate about 30% of glands perfused with 5 mM glucose. Gradually reducing the glucose concentration is associated with a progressive decrease in the secretion of chloride. The apparent Km for the exogenous glucose-dependent chloride secretion is around 2 mM. Phloretin and cytochalasin B, agents that inhibit facilitated glucose carriers of the solute carrier 2 (Slc2) family such as glucose transporter 2 (GLUT2), do not inhibit the secretion of chloride by the perfused rectal glands. Phloridzin, which inhibits Slc5 family of glucose symporters, or α-methyl-d-glucoside, which competitively inhibits the uptake of glucose through Slc5 symporters, inhibit the secretion of chloride. Thus the movement of glucose into the rectal gland cells appears to be mediated by a sodium-glucose symporter. Sodium-glucose cotransporter 1 (SGLT1), the first member of the Slc5 family of sodium-linked glucose symporters, was cloned from the rectal gland. No evidence of GLUT2 was found. The persistence of secretion of chloride in the absence of glucose in the perfusate suggests that there is an additional source of energy within the cells. The use of 2-mercapto-acetate did not result in any change in the secretion of chloride, suggesting that the oxidation of fatty acids is not the source of energy for the secretion of chloride. Perfusion of isolated glands with KCN in the absence of glucose further reduces the secretion of chloride but does not abolish it, again suggesting that there is another source of energy within the cells. Glucose was measured in the rectal gland cells and found to be at concentrations in the range of that in the perfusate. Glycogen measurements indicated that there are significant stores of glucose in the rectal gland. Moreover, glycogen synthase was partially cloned from rectal gland cells. The open reading frame of glycogen phosphorylase was also cloned from rectal gland cells. Measurements of glycogen phosphorylase showed that the enzyme is mostly in its active form in the cells. The cells of the rectal gland of the spiny dogfish require exogenous glucose to fully support the active secretion of salt. They have the means to transport glucose into the cells in the form of SGLT1. The cells also have an endogenous supply of glucose as glycogen and have the necessary elements to synthesize, store, and hydrolyze it.

Attraction and Electrophysiological Response to Identified Rectal Gland Volatiles in Bactrocera frauenfeldi (Schiner)

Bactrocera frauenfeldi (Schiner) (Diptera: Tephritidae) is a polyphagous fruit fly pest species that is endemic to Papua New Guinea and has become established in several Pacific Islands and Australia. Despite its economic importance for many crops and the key role of chemical-mediated sexual communication in the reproductive biology of tephritid fruit flies, as well as the potential application of pheromones as attractants, there have been no studies investigating the identity or activity of rectal gland secretions or emission profiles of this species. The present study (1) identifies the chemical profile of volatile compounds produced in rectal glands and released by B. frauenfeldi, (2) investigates which of the volatile compounds elicit an electroantennographic or electropalpographic response, and (3) investigates the potential function of glandular emissions as mate-attracting sex pheromones. Rectal gland extracts and headspace collections from sexually mature males and females of B. frauenfeldi were analysed by gas chromatography-mass spectrometry. Male rectal glands contained (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro [5.5]undecane as a major component and (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane as a moderate component. Minor components included palmitoleic acid, palmitic acid, and ethyl oleate. In contrast, female rectal glands contained (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and ethyl laurate as major components, ethyl myristate and ethyl palmitoleate as moderate components, and 18 minor compounds including amides, esters, and spiroacetals. Although fewer compounds were detected from the headspace collections of both males and females than from the gland extractions, most of the abundant chemicals in the rectal gland extracts were also detected in the headspace collections. Gas chromatography coupled electroantennographic detection found responses to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane from the antennae of both male and female B. frauenfeldi. Responses to (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane were elicited from the antennae of females but not males. The two spiroacetals also elicited electropalpographic responses from both male and female B. frauenfeldi. Ethyl caprate and methyl laurate, found in female rectal glands, elicited responses in female antennae and palps, respectively. Y-maze bioassays showed that females were attracted to the volatiles from male rectal glands but males were not. Neither males nor females were attracted to the volatiles from female rectal glands. Our findings suggest (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane as components of a sex-attracting pheromone in B. frauenfeldi.

Rectal Gland Chemistry, Volatile Emissions, and Antennal Responses of Male and Female Banana Fruit Fly, Bactrocera musae

The banana fruit fly, Bactrocera musae (Tryon) (Diptera: Tephritidae), is an economically important pest endemic to Australia and mainland Papua New Guinea. The chemistry of its rectal glands, and the volatiles emitted during periods of sexual activity, has not been previously reported. Using gas chromatography–mass spectrometry (GC-MS), we find that male rectal glands contain ethyl butanoate, N-(3-methylbutyl) acetamide, ethyl laurate and ethyl myristate, with ethyl butanoate as the major compound in both rectal gland and headspace volatile emissions. Female rectal glands contain four major compounds, ethyl laurate, ethyl myristate, ethyl palmitate and (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, as well as 11 minor compounds. For both male and female B. musae, all compounds found in the headspace were also present in the rectal gland extracts, suggesting that the rectal gland is the main source of the headspace volatiles. Gas chromatography–electroantennography (GC-EAD) of rectal gland extracts confirms that male antennae respond to male-produced ethyl laurate and female-produced (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, while female antennae respond to male-produced ethyl butanoate but no female-produced compounds. This is an important step in understanding the volatiles involved in the chemical communication of B. musae, their functional significance, and potential application.

Chemical Compounds from Female and Male Rectal Pheromone Glands of the Guava Fruit Fly, Bactrocera correcta

The guava fruit fly, Bactrocera correcta, is one of the major pests affecting mango (Mangifera indica) and guava (Psidium guajava) production in China. The compound β-caryophyllene was identified from the rectal gland extracts of wild B. correcta males and was demonstrated to be a more specific and potent male lure than methyl eugenol (ME) for B. correcta. In order to find potential additional pheromone attractants for the monitoring and mass-trapping of this fruit fly, a series of chemical and behavioral assays were conducted in this study. Ten compounds were identified from the rectal glands of virgin B. correcta females. These compounds consisted of five major compounds (i.e., ethyl dodecanoate, ethyl tetradecanoate, ethyl (E)-9-hexadecenoate, ethyl hexadecanoate, and ethyl (Z)-9-octadecenoate) in high quantities, and other compounds (i.e., octanal, N-(3-methylbutyl) acetamide, (Z)-9-tricosene, ethyl octadecanoate, and ethyl eicosanoate) in trace amounts, while virtually no compounds were found in male rectal glands. The bioassays indicate that female rectal gland extracts are attractive to virgin females and males. Furthermore, a cyclical production of the five major compounds was found, recurring at roughly 10-d intervals with peaks in 10–13-, 25-, and 35-d-old females. Collectively, these results will contribute to the understanding of pheromone communication in B. correcta and may provide important information for improving existing monitoring and control methods for this pest.