Light and Electron Microscope Observations of the Male Reproductive Organs of Adult Julodis ehrenbergii Laporte (Coleoptera, Buprestidae)

Abstract

This paper was the first preliminary description of the male reproductive organs in Julodis ehrenbergii Laporte (Coleoptera, Buprestidae) using light and scanning electron microscope techniques. The structure has a couple of testes, a couple of vasa deferentia, a couple of accessory glands, a couple of spermatophoral glands, and a single ejaculatory duct opening in the aedeagus. Each testis is made up of many elongated testicular follicles. Our histological observation showed cysts at different stages of development in the testicular follicles. In other words, spermatocytes, spermatids, and spermatozoa, respectively, are formed from the spermatogonia located at the distal end of the testicular follicles. Mature sperm bundles were observed in the lumen of the vasa deferentia. The male accessory glands are curved and thin tube-shaped. There are dense secretion granules in the cytoplasm of the accessory glands' epithelial cells. The spermatophoral glands are roughly oval-like structures and have three lobes on one side. The ejaculatory duct is characterized by the presence of the cuticle layer on the apical surface of the cells. The findings were compared with the male reproductive structures of some other species in the Coleoptera order. Some characteristics, including the number and shape of testicular follicles and accessory glands, among the species of the Coleoptera order, show differences. These features help allow future comparisons with the male reproductive organs of other Coleoptera species.

Keywords: jewel beetles; light microscopy; scanning electron microscopy; spermatophoral glands; testicular follicles.

FIGURE 1

(A) 2D drawing of the male reproductive organs of an adult J. ehrenbergii. (B) The stereomicroscope image of the male reproductive organs of an adult J. ehrenbergii. T: testes, *: vasa deferentia, Sg: spermatophoral glands, →: male accessory glands, Dg: ductus ejaculatorius.

FIGURE 2

(A) The scanning electron microscope image of the outer surface of the testes. (B) High magnification image of one testis (SEM). T: testes, *: vasa deferentia, Tr: tracheal network.

FIGURE 3

(A) The scanning electron microscope image of the testicular follicles (F). : trachea. (B) Testicular follicle (F) is marked in red and is seen with its distal region closed (SEM). : trachea. (C) The cross section of the testicular follicles (SEM). (D) The longitudinal section of the testicular follicles in LM (HE staining). *: vasa deferentia, dz: differentiation zone, mz: maturation zone, gz: growth zone.

FIGURE 4

(A) Round‐shaped tailless spermatocytes in SEM. (B) and (C) Round‐shaped tailless spermatocytes (Sp) in LM (Mallory's trichrome staining). (D) The spermatozoa at the end of the spermiogenesis stage in SEM. (E) and (F) The spermatozoa (Sz) at the end of the spermiogenesis stage in LM (E) HE staining, (F) Mallory's trichrome staining).

FIGURE 5

(A) The scanning electron microscope image of the outer surface of the vasa deferentia. (B) and (C) The cross section of the vasa deferentia (SEM). (D) The cross section of the vasa deferentia (LM) (HE staining). Tr: trachea, E: epithelial layer, L: lumen, ◌: sperm tails.

FIGURE 6

(A) The scanning electron microscope image of the outer surface of the male accessory glands. (B) The muscle layer (M) on the outer surface of the male accessory glands (SEM). (C) The cross section of the male accessory glands. Different sizes of granules (○), which are in the lumen (SEM). (D) Different sizes of granules (○), which are in the cytoplasm of the cells (SEM). E: epithelial layer.

FIGURE 7

(A) The stereomicroscope image of the spermatophoral glands that have knotted on one side. (B) The scanning electron microscope image of the outer surface of the spermatophoral glands that have knotted on one side. (C) The muscle layer (M) on the outer surface of the spermatophoral glands (SEM). (D) and (E) The scanning electron microscope images of the multilayered epithelial cells. (F) The cross section of the spermatophoral glands (LM) (HE staining). M: muscle layer, Tr: trachea, : nucleus.

FIGURE 8

(A) The scanning electron microscope image of the outer surface of the ductus ejaculatorius. (B) The muscle layer (M) on the outer surface of the ductus ejaculatorius (SEM). (C) The cross section of the ductus ejaculatorius (SEM). (D) The scanning electron microscope image of the inner surface of the ductus ejaculatorius. The small figure in the corner in Figure 8D is a different view of the chitin spines on the inner surface of the ductus ejaculatorius. E: epithelial layer, *: cuticle layer, : long spines on the cuticle layer.