Some Monogenetic Trematodes from the Galapagos Islands and the Neighboring Pacific

Authors

Frank Grose Meserve, University of Nebraska

First Advisor

Harold W. Manter

Date of this Version

8-1-1935

Citation

Thesis (PhD), 1935--University of Nebraska, ii, 221 pages.

A thesis presented to the Faculty of the Graduate College in the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy, Department of Zoology, Lincoln, Nebraska, United States, August 1, 1935.

Comments

Approved by Harold Winfred Manter (major advisor), David Day Whitney, Myron Harmon Swenk, James Melvin Reinhardt, Joseph Emanuel Alexander Alexis, Elda Rema Walker, Joy Paul Guilford, and Bernard Clifford Hendricks.

Abstract

Introduction

Trematodes are parasitic, unsegmented, flattened (rarely cylindrical) worms. They have ventral, anterior, posterior or median attachment organs. The sense organs are poorly developed. The mouth is terminal or ventral and subterminal. The intestine is usually forked with or without lateral branches. The animals, with few exceptions, are hermaphroditic. The ovary is usually single. They have one, two, or more testes. The development is direct with only one host in the ectoparasitic Monogenea and indirect in the Digenea which have two or more hosts. The digenetic trematodes usually parasitize vertebrates which serve as their primary hosts and invertebrates (Mollusca) which serve as their secondary hosts. The Monogenea are usually small, flattened, elongate or leaf-shaped, hermaphroditic worms. They frequently have two suckers in the mouth cavity. The posterior end has a well developed attachment disc with suckers or clasping organs and is frequently armed with two or more hooks. The mouth is usually ventral and subterminal, The intestine is usually forked, separated or united at the posterior end, and usually with few or numerous lateral branches. There are two excretory pores which open dorsally near the anterior end. A vagina may be absent or present. When present, it opens dorsally, medianly, or laterally and may be single or double. A genito-intestinal canal is frequently present. The development is direct without alternation of hosts. They live on the gills and skin or in the mouth and nasal cavities and rarely in the urinary bladder of vertebrates. They are common gill parasites of fish.

The present paper is an account and description of new species of ectoparasitic trematodes found on marine fish in the South Pacific in the region of the Galapagos Islands. The animals were collected and preserved by Professor H. W. Manter who was a member of the Third G. Alan Hancock Expedition to the Galapagos Islands in 1934. All the specimens were collected in January, February and early March. In a preliminary report Manter (1934) states: "Over 500 marine fish, representing approximately 100 species, were examined for parasites. Approximately 100 species of trematodes were collected, 80 per cent of the species of fish and 43 per cent of the Individuals examined being infected. Approximately 80 per cent of the trematodes collected were Monogenea.”

The writer wishes to extend acknowledgement and express sincere appreciation to Professor H. W. Manter under whose direction these studies were made. Descriptions of all animals were made from specimens collected by him with the exception of type material of Protomicrocotyle which was made available through the courtesy of Doctor E. W. Price. Particularly valuable in this research was the loan of books and reprints from Professor Manter's personal library. The writer is also indebted to Professor T. J. Fitzpatrick for his valuable aid in securing periodicals and reprints from other libraries. Special acknowledgement is given to Doctor Emmett W. Price of the Bureau of Animal Industry, United States Department of Agriculture, for the loan of type material of Protomicrocotyle mirabile (MacCallum 1918) from the National Museum. Sincere gratitude is also expressed to Professor D. D. Whitney who cooperated in many ways and expressed a keen and kindly interest throughout these studies.

Material and Methods. No new methods of technique were used. The animals were killed in formol-alcohol-acetic acid solution (formalin 6.5 parts, 50 per cent alcohol 100 parts, glacial acetic acid 2.5 parts) under a cover glass. Slight pressure was applied to the cover glass to flatten the specimen. After several hours the killing solution was removed and the specimens were preserved in 70 per cent alcohol. Specimens were stained in Delafield's haematoxylin. Some were counterstained with orange G, eosin, or erythrosin. Serial sections were made except where there were few specimens. Toto mounts were cleared in cedar oil and serial sections in xylol. All were mounted in balsam.

Summary and Conclusions

A study was made of twenty-two species of Monogenea collected from the gills of marine fish by Doctor H. W. Manter from the following localities: open sea off the coast of Mexico, Isabel, Socorro, Secas, and Clarion Islands, and Tangola Tangola, Mexico; open sea off the coast of the Galapagos Islands, Tagus Cove, Albermarle Island, James, Chatham, Hood and Charles Islands, Galapagos; Bahia Honda, Panama; San Francisco, Ecuador; Port Utria, Colombia; and Port Culebra, Costa Rica.

Twenty new species are described. All are placed in known genera with two exceptions. Two previously described species are Encotyllabe pagrosomi MacCallum and Axine aberrans Goto. The distribution of Encotyllabe pagrosomi MacCallum, first described from gills of Pagrosomus auratus of Australia by MacCallum in 1917, is extended to James Island, Galapagos from gills of Caulolatilus sp. Axine aberrans, first described from the gills of Belone schismatorhynchus from Hagi, Japan by Goto in 1894, was collected near Secas Island, Mexico from the gills of Tylosurus fodiator (Jordan and Gilbert).

Two new genera are proposed; Pseudomicrocotyle which is similar to Microcotyle with the exception that it bears hooks at the posterior end, and Acanthocolpa, which has a characteristic lateral vaginal opening and a spine imbedded in the wall of the distal end of the vagina. Microcotyle acanthurum Parona and Perugia 1890 is removed from Microcotyle and placed in the new genus, Pseudomicrocotyle.

Ancrocotyle, which Johnston included in the subfamily, Ancrocotylinae, is placed in the subfamily Benedeninae Johnston.

The subfamily Benedeniinae Johnston 1931 is discussed. The genus Benedenia includes those with true anterior suckers. The genus Entobdella includes those with false suckers.

The genus Thoracotyle MacCallum 1913 is expanded. The second species to be described and the first to be described from the Pacific Ocean is discussed. MacCallum's species from the Atlantic Ocean and the new species both occur on the same host, Scomberomorus maculatis (Mitchill), Spanish mackerel. The new species, T. paradoxica was collected at Tangola Tangola, Mexico.

Type material of Protomicrocotyle mirabile (MacCallum 1918) was examined. Corrections are made in MacCallum's measurements and interpretations. The genus is redescribed and expanded. A new species, P. pacifica, from the gills of Xurel marginatus (Gill) collected at Port Culebra, Costa Rica, is described. This is the second species to be described in the genus and the first species to be described from the Pacific Ocean.

New species were described in the following genera: Benedenia, Entobdella, Heterobothrium, Diclidophora, Octocotyle, Microcotyle, Pseudomicrocotyle, Thoracotyle, Axine, Pseudaxine, Acanthocolpa, and Protomicrocotyle.

Previously undescribed structures surrounding the genital pore of Acanthocolpa cypseluri and A. yamagutii are described and the name, giant cells, proposed for them.

The name glands of Goto is proposed for post-testicular glands first described by Goto and called different names by various authors. They are considered of taxonomic significance.

The fact that related species of ectoparasitic trematodes live on related hosts is pointed out and discussed. Acanthocolpa was collected from flying fish at Clarion Island, the open sea off the coast of Mexico, and Port Culebra, Costa Rica. A similar undescribed species of Acanthocolpa has been collected from the gills of flying fish at Tortugas, Florida by H. W. Manter. The twenty-two species described in this paper were each found on only one specific host although over five hundred fish representing approximately one hundred species were examined.