Water Mites from Argentina Author(s): Ruth Marshall Source: Transactions of the American Microscopical Society, Vol. 59, No. 3 (Jul., 1940), pp. 377-382 Published by: Wiley on behalf of American Microscopical Society Stable URL: http://www.jstor.org/stable/3222553 . Accessed: 25/06/2014 00:29 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . Wiley and American Microscopical Society are collaborating with JSTOR to digitize, preserve and extend access to Transactions of the American Microscopical Society. http://www.jstor.org This content downloaded from 185.2.32.106 on Wed, 25 Jun 2014 00:29:34 AM All use subject to JSTOR Terms and Conditions
Transcript
Water Mites from ArgentinaAuthor(s): Ruth MarshallSource: Transactions of the American Microscopical Society, Vol. 59, No. 3 (Jul., 1940), pp.377-382Published by: Wiley on behalf of American Microscopical SocietyStable URL: http://www.jstor.org/stable/3222553 .
Accessed: 25/06/2014 00:29
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp
.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].
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Wiley and American Microscopical Society are collaborating with JSTOR to digitize, preserve and extendaccess to Transactions of the American Microscopical Society.
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This paper is a study of a collection of hydracarina from certain small lakes of Argentina secured by Dr. Stillman Wright who kindly gave them to the author for examination. It will add something to the scanty knowledge of the water mites of this country. Four species of four genera are described; one of these is new and two are first records for Argentina. In addition to these the collection contained a few unidentified nymphs of Eylais.
Diplodontus peregrinus Koen.
(Plate I, Figs. 6, 7) This species, described by Koenike (1905) from material collected in
Brazil, is represented by 19 individuals found in Lake Lenora, San Luis, Dec. 10, 1936.
It is closely related to the cosmopolitan soecies, D. despiciens (Muill.), as pointed out by Koenike, but differs from it in several well defined details. Papillae on the body surface of D. peregrinus are smaller than in the related species; the two eyes of either side are smaller and closer together; the legs are slimmer; the maxillary organ (not correctly shown in Fig. 3 by Koenike) is shorter and broader, while the palpi are very similar in the two species. In the epimera a conspicuous feature is the deep bay, broad posteriorly, formed by the first pair; each plate has a median posterior prolongation of the underlying part. The genital plates are somewhat broader in the an- terior part, have very long fine hairs, and their acetabula are smaller and less numerous than in the related species.
Piona erratica n. sp. (Plate II, Figs. 8-11)
A species related to P. tuberifera Viets (Europe) and P. dejecta Viets (Brazil), it is represented here by 29 adults, two of them males, together with six undetermined nymphs, from four small lakes in Province de San Luis, Dec. 1936.
The body is oval, elevated, the anterior end lower, bulging between the eyes. Males measure 0.85 mm., the largest female, 1.67 mm. The cuticula is delicate and structureless. The antennary bristles are very small. Colors could not be determined. The epimeral groups are well separated in the fe- male, close together in the male with the posterior groups fused medially. The anterior outer borders of the first and second pairs are somewhat trun- cated. The fourth epimera are long, with deeply concave posterior borders. The genital plates do not extend laterally beyond the limits of the posterior angles of the fourth epimera; the 30 to 40 acetabula are very variable in
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number and arrangement, even on the two sides of the same individual, a character which suggested the specific name. In the female the acetabula are arranged in an irregular sickle-shaped formation, some clustered on three (or more) small plates, with the central ones scattered. In the male there are two wing-shaped united plates, well fused with the fourth epimera medially, extending directly out from a central shallow depression in which lies the genital opening; the acetabula are scattered irregularly on these. The palpi are wider than the legs, a little larger and stouter relatively in the male than in the female, with a few short broad bristles; segment four has two large papillae (smaller in the female) bearing each a long hair in the middle of the concave side; segment five ends in three small finger-like proc- esses. The third leg in the male has a long fifth segment, while the sixth segment is about half its length and has one elongated claw and one short one. The male fourth leg has but a slight concavity in the fourth segment.
Krendowskia convexa (Rib.) (Plate II, Figs. 12-15)
The original descriptions of the species by Ribago (1902, 1903), under the name Arrenurella convexa, were based on the study of a single male found in Chili; but as they are incomplete and the drawings very diagram- matic, it is difficult to recognize the form. The new material appears to conform sufficiently in most details (although measurements differ) to jus- tify the opinion that it represents the Ribago species. Two specimens, male and female, in excellent preservation, came from a large artificial lake (Lago Embalse, Rio III, southern part of Prov. de C6rdobay, Dec. 18, 1936).
The body is broadly elliptical, strongly convex dorsally and ventrally, 1.70 mm. long in both sexes. (Ribago gives the body as oval, 1.30 mm.) The color is pale olive green, showing dorsally several small dark blotches and a central somewhat reddish figure. The cuticula is coarsely lined length- wise: the body wall is heavily chitinized and the pores are conspicuous. The dorsal shield is large, its anterior outline crenated. Hairs on the surface are numerous, the more anterior being short. The epimera are clearly outlined,
EXPLANATION OF PLATE I
1. Arrenurus oxyurus, ventral posterior end, male; HY, hyaline appendage. 2. Arrenurus oxyurus, left palpus, male. 3. Arrenurus oxyurus, dorsal view, male. 4. Arrenurus oxyurus, lateral view, male. 5. Arrenurus oxyurus, leg IV, 4-6, male. 6. Diplodontus peregrinus, ventral plates, female. 7. Diplodontus peregrinus, maxillary organ and right palpus.
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the surfaces reticulate; the partly fused first pair leave a broad bay for the maxillary organ and have pointed anterior outer margins, as do also the second pair (but not the third, as shown by Ribago, 1903, Fig. 42). The medial borders of the third epimera are heavy. The fourth epimera are broadly triangular, with rounded posterior angles; the excavation on the anterior medial corner is faintly outlined; the gland pore here is not con- spicuous and the accompanying hair is small. The genital organ in the male, as shown by Ribago, is narrow and enclosed for about one-third of its length by the bay formed by the last epimera; in the female it lies farther in and is broader. There are six oblong genital acetabula in both sexes. The max- illary organ is broad shield-shaped with a slight beak. The short stout palpi are slightly wider than the legs; comparison of Fig. 3 (Ribago, 1903) and Fig- ure 13 of the present paper shows essential similarity. On the second palpal segment the characteristic two long hairs are a little removed from the proximal inner surface; the third segment is relatively short; the more elongated fourth segment has its distal end much drawn out and truncated, while the small claw-like fifth is bifid. The legs are shorter than the body and weak, the ends reddish. The ends of the first three pairs are slightly widened. Swimming hairs are present and bristles are abundant on all legs; claws are small.
Arrenurus oxyurus Rib.
(Plate I, Figs. 1-5) In Ribago's papers (1902, 1903) he describes this species from one male
found in Argentina. Seven males secured by Dr. Wright in a pond near Dufaur, Prov. di Buenos Aires, Jan. 26, 1937, appear without doubt to be Arrenurus oxyurus, although the original descriptions and drawings need revision.
The body, very short and bulky as shown by Ribago (1903, Fig. 32), is difficult to measure, but 1.50 mm. as originally given is found to be approx- imately correct. The color is dull orange with some dark blotches. The body is broadest at the origin of the appendix, narrower and concave be- tween the eyes where there are two protuberances as well as a bulge over each eye. The dorsal line runs over on each side onto the appendix; within
it are two large humps and two others of the same size anterior to the line. The appendix, though short, is well developed and complex; the details are best understood by reference to the drawings (Figs. 1, 3, 4) which agree substantially with the diagrammatic sketches of Ribago (1903, Figs. 30, 32, 36, 37). The petiole is distinctive, as shown in both sets of drawings; viewed laterally it is like a stout claw but with lateral appendages seen in other views. Above it is a narrow but well developed hyaline appendage (HY). In the epimera the first pair are joined by a long medial border but the suture is evident; the anterior outer margins of this pair and the second are pointed and the fourth have rather pronounced posterior angles. Palpi (not shown by Ribago) carry a few bristles; the long fifth segment shows a wavy outer outline. The legs are of the usual form, with a short spur on the fourth segment of the fourth leg.
BIBLIOGRAPHY
Koenike, F. 1905. Zwei neue Wassermilben aus den Gattungen Megapus und Diplodontus. Zool. Anz. 28: 696.
Ribago, C. 1902. Acari sudamericani. Zool. Anz. 25: 504. 1903. Diagnosi di alcune specie nuove di Hydrachnidae e di un Ixodidae del Sud America.
An. d. R. Scuola Sup. Agr. in Portica, 5: 1-28.
Viets, K. 1931. Ober einige Gattungen und Arten der Axonopsae, etc. Zool. Anz. 93: 42.
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