Ostracoda of the Family Cytheruridae from the Gulf of Panama

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The present paper represents the first in a series on ostracoda from Gulf of Panama, and deals with Cytheruridae which comprise 31 species distributed among nine genera. Three genera : Serrocytherura, Nearocytherura, and Lobosocytheropteron; and twelve species : Eucytherura sanjoensis, E. pinasensis, Gytherura nodosa, C. purii, Semicytherura reticuliforma, Serrocytherura panamaensis, Kangarina complicata, K. delicata, K. pervadera, Lobosocytheropteron perlasensis, L. bartolomensis and L. pinasensis, are described as new. Several microstructures peculiar to certain genera were recognized with the aid of the scanning electron microscope. Noteworthy are : 1) the weak reticulation in the lateral surface in forms referred to Kangarina; 2) in Eucytherura, each solum has sieve-plate-like coarse perforations, which correspond to internal openings; 3) in Paracytheridea, the presence of papillae, rings, sieve plates and simple pores armored by papillae; and 4) relatively large, simple internal openings in forms of Kangarina that serve to distinguish "Kangarina." Under the scanning electron microscope the wide extension of calcified posterior inner lamella which has been a basis for Semicytherura is not necessarily distinct from non-calcified one. Under the circumstances, in this report, the species referred to Semicytherura are based on the wide extension of posterior inner lamella observed without concern as to whether well calcified or not. Using frequency of occurrence rather than presence-absence data, four main distributional patterns are recognized among the cytherurid species. The major patterns and their subdivisions are : I. Widespread pattern : These forms prevail widely on the entire shelf area. I-A. Bahia San Miguel subdivision : Semicytherura sandbergi and Nearocytherura bananaformis are found abundantly in the Bahia San Miguel as well as in the outer area. This distribution suggests that those forms do not have any preference for particular environmental condition in this Gulf. I-B. Punta Garachine subdivision : Kangarina pervadera, Eucytherura guaymasensis, and Cytheropteron assimiloides are distributed widely, but are absent from Bahia San Miguel, and seem to show preferences for the outer shelf area. II. Eastern pattern : The forms in this pattern are distributed in the eastern half of the Gulf, with rare occurrence from the other realms. II-A. Archipelago subdivision : Among the eastern pattern, Paracytheridea tschoppi, P. clara, and Cytherura nodosa occurred dominantly in the areas around Archipielago de las Perlas and Bahia San Miguel, showing a preference for shallow water. II-B. Bahia Pinas subdivision : Lobosocytheropteron pinasensis and L. bartolomensis frequently occurred off Bahia Pinas, showing a preference for outer shelf area. II-C. Off Bahia Pinas subdivision : The forms prevail in the restricted to the southeastern part of the Gulf and are not found on inner shelf. This subdivision may show a narrow tolerance to the environmental condition and represented by Kangarina complicata. III. West-Central pattern : The forms representing this pattern prevail frequently in the southwestern to central parts of the Gulf and are very rarely found from the other realm. The pattern is represented by Kangarina delicata and Eucytherura sanjoensis which are dominant at depths of about 100 m. IV. Outer Shelf pattern : Four species are found in low numbers at three stations with depths more than 1000 m. Three of these species are not found on inner shelf. These are Lobosocytheropteron? sp. A, L.? sp. B, and L.? sp. C.
東北大学の論文
1974-11-15

Ostracoda of the Family Cytheruridae from the Gulf of Panama

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