Argulus Japonicus Research Articles

The Ultrastructure of the Newly Hatched Argulus Japonicus Thiele, 1900 Larvae (Branchiura)

Abstract Fcrtilized Argulus japonicus Thiele, 1900, eggs were hatched in the laboratory. The morphology of the first developmental stage was studied by means of scanning electron microscopy and light microscopy. The surface topography of the carapace and appendages are described. It is shown that the mandible base is fused with the labrum and metastome to form the proboscis.

The male reproductive system and mechanism of sperm transfer in Argulus japonicus (Crustacea: Branchiura).

The histomorphology of the male reproductive system and surface morphology of the "peg-and-socket" in Argulus japonicus are described from serial sagittal and transverse sections and scanning electron micrographs. The prostate complex consists of a glandular part, a reservoir for storing the secretion, and an efferent duct opening into the ejaculatory duct. The openings of both the vas deferens and the prostate duct into the ejaculatory duct are guarded by sphincters. The ejaculatory ducts, which are lined by tall columnar epithelial cells, do not open into the cuticle-lined genital atrium but are blind-ending tubes. This observation and results obtained from observing live specimens, as well as the fact that no spermatophores are formed, suggest that semen could leave the ejaculatory duct only after puncturing of its walls. It is suggested that sperm transfer is accomplished in the following manner: during copulation contraction of the muscular walls of the vas deferens and prostate duct causes semen to be pumped into the ejaculatory duct, which is then closed off by sphincters and a high internal pressure is developed. When a spermathecal spine penetrates the walls of the ejaculatory duct, semen flows from the ejaculatory duct into the spermathecal vesicle due to the higher pressure in the ejaculatory duct. This mechanism is analogous to the sucking up of fluid with a hypodermic syringe. © 1993 Wiley-Liss, Inc.

Comments on the morphology of the pre-oral spine in Argulus (Crustacea: Branchiura).

A histological study of the pre-oral spine and associated structures in Argulus japonicus reveals that two exceptionally long and slender muscles casuse retraction of the spine into the spinal sheath. Originating from the body wall mid-dorsally the two muscles proceed through the nerve ring and the blood-filled lumen of the spinal sheath before being inserted on a bolster of tissue constituting the base of the spine. Movement of the spinal sheath is affected by two muscles originating from a common apodeme in the dorsal body wall, just posterior to the nauplius eye, and inserted on the lateral walls of the base of the spinal sheath. Two ducts, each leading from a glandular complex in the lateral parts of the carapace, proceed rostrally through the haemocoelic spaces. After passing the tritocerebrum laterally they accompany the retractor muscles of the spine on their course to the base of the spine. Passing through the bolster of tissue at the base of the spine the two ducts run all the way up to the tip of the spine where they open separately. The glandula praeboscoidalis is not associated with the pre-oral spine since its duct runs posteriorly in the wall of the proboscis. The labial spines are associated with giant glandular cells located beneath the optic tracts. © 1992 Wiley-Liss, Inc.

Lack of Host Species Selection by the Exotic Parasitic Crustacean,Argulus japonicus

Abstract We tested the hypothesis that Argulus japonicus, an external parasite of fishes, would prefer goldfish (Carassius auratus), a cyprinid with which it evolved, to the fathead minnow (Pimephales promelas), a common cyprinid native to North America. In each of two experiments, parasites were confined individually with goldfish and fathead minnows, and attachments to each fish were recorded. The frequencies of attachment were not significantly different from random, regardless of whether expected frequencies were adjusted to reflect the relative surface areas of the two host species. Moreover, once attached to a host, an Argulus was not more likely to detach from either host species within the first thirty seconds of attachment.

Response by the Parasitic CrustaceanArgulus japonicusto Host Chemical Cues

ABSTRACT Argulus japonicus. an ectoparasite of fishes, displayed greater activity when exposed to a treatment of water conditioned by carp than when exposed to a control treatment of unconditioned water. Treatment order had no significant effect. Argulus can thus respond to host chemical cues in the absence of cues detectable by other sensory modes.

The Effect of a Fish Medication onArgulus japonicus, a Crustacean Parasite of Fish

ABSTRACT The effect on Argulus japonicus of Furan-2, a medication for fish, was tested in three trials. In each trial, survival of A. japonicus treated with Furan-2 was as high or higher than that of the controls. It is possible that Furan-2 inhibits microorganisms that otherwise would attack A. japonicus stressed by handling and held without food. When fish and Argulus must be confined together in the laboratory, it may be possible to use Furan-2 to treat the fish for pathogens without harm to the Argulus.

Laying, development and hatching of eggs of the fish ectoparasite Argulus japonicus (Crustacea: Branchiura)

Egg laying of the fish‐louse Argulus japonicus was observed and examined experimentally. The effect of temperature on development time and hatching yielded an inverse exponential function. Hatching started after 61–10 days in a temperature span of 15–35 °C. Eggs are laid in strings on hard substrata and covered by a gelatinous material. Females lay between 1–9 strings, 5–226 eggs per string, arranged in 1–6 rows. Four embryonic developmental stages were recognized and the mean hatching efficiency was 50% in the optimal temperature range of 20–30 °C. Hatching efficiency was not related to either the number of eggs in a string or the total number of eggs laid by any particular female. Argulus japonicus displays continuous egg‐laying activity with a possibility of an overwintering mechanism which suggests a seasonality of a sort.