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- Title
Morphological variability of Pleuromamma abdominalis (Copepoda, Calanoida, Metridinidae) along two latitudinal transects in the eastern North Pacific Ocean.
- Authors
Fornshell, John; Ferrari, Frank D.
- Abstract
Adult females and males of Pleuromamma abdominalis were examined from 26 plankton samples taken at stations in the eastern North Pacific Ocean along two latitudinal gradients, 150°W between 21.55°N and 14.00°S, and 119°W between 17.09°N and 20.00°S. The species was found at all stations except three between 17.9°N and 12.6°N along 119°W. Variation within a sample was observed in the ventral attenuations [= spiniform outgrowths] of the first segment of antenna 1 of females, and specimens referable to P. abdominalis forma edentata could not be distinguished unequivocally from other females. Males with a strongly asymmetrical urosome and re-curved lateral seta on the left caudal ramus, referable to P. abdominalis forma abdominalis, were found, as were males with a quasi-symmetrical urosome and simple lateral seta on the left caudal ramus, referable to P. abdominalis forma abyssalis. Specimens of the latter form were not restricted to deep water but were present in samples taken as shallow as 200 m. Males with a slightly asymmetrical urosome, not as pronounced as that of P. abdominalis forma abdominalis, and with a simple lateral seta on the left caudal ramus, also were found. The degree of asymmetry among this third group of males was variable. There was no discernable pattern in depth or geographical distribution of either female or male morphs. Based on gradations of morphological states traditionally used to diagnose the different forms of P. abdominalis, the species appears to be variable, but the nominal forms should not be considered subspecies. Morphological variation among females and males of P. abdominalis should continue to be registered; in situations where groups of P. abdominalis can be clearly categorized, they should be denoted simply as morphs.
- Subjects
PACIFIC Ocean; PLEUROMAMMA; TRANSECT method; PLANKTON culture; PHYTOGEOGRAPHY; SOBOLEV gradients
- Publication
Crustaceana, 2010, Vol 83, Issue 6, p753
- ISSN
0011-216X
- Publication type
Article
- DOI
10.1163/001121610X492120