Histological Characteristics of Abnormal Protrusions on Copepods from Lake Michigan, USA

Gretchen A. Messick ； Henry A. Vanderploeg ； Joann F. Cavaletto ； Suzanne S. Tyler

《Zoological Studies》 43卷2期 (2004/04) Pp. 314-322

並列摘要

Abnormal protrusions have been observed on crustacean zooplankton species from Lake Michigan since 1994. Copepods collected from 1994 to 2000 were assayed for the prevalence of protrusions, and histologically characterized for various morphologies. Protrusions occurred more frequently on nauplii than on copepodites or adults. Most protrusions were located laterally on the copepod body. External shapes and surfaces of the protrusions varied from smoothly rounded to bossulated and amorphous. Protrusions had diverse histological characteristics. Necrotic tissue was present in 58% of protrusions. Some protrusions had hyaline, crystal- like structures either on the surface or embedded within tissues of the protrusion. Nearly 40% contained what appeared to be herniated host tissue. A few copepods (3%) had elongated, symmetrical, somewhat transparent gross protrusions that were histologically identified as ellobiopsid parasites. Other protrusions had a histology that suggested ellobiopsid parasites such as a bossulated, bud-like external morphology or a smoothly rounded covering. Additionally, round structures observed within protrusions were similar to sporulation bodies of ellobiopsid parasites. It is unlikely that these protrusions were due to fixation artifacts or were caused by diatoms puncturing copepods in the collection devices. A few protrusions were obvious ellobiopsid parasites, but the histology of most protrusions is not consistent or obvious enough to allow identification of a plausible etiological agent.

並列關鍵字

Cyclopoid ； Calanoid ； Ellobiopsid ； Herniated ； Necrotic