DIFFERENTIATION OF PRIONOTUS CAROLINUS AND 



PRIONOTUS EVOLANS EGGS IN HEREFORD INLET ESTUARY, 



SOUTHERN NEW JERSEY, USING IMMUNODIFFUSION 



Walter J. Keirans, 1 Sidney S. Herman, 2 and R. G. Malsberger 2 



ABSTRACT 



Immunochemical techniques were used to classify the planktonic eggs of Prionotus carolinus (northern 

 searobin) and Prionotus evolans (striped searobin) collected from a southern New Jersey estuary. Results 

 of immunochemical identifications were compared with identifications based upon the commonly used 

 morphological character of egg oil globule distribution. An average identification error of 22.3% was found 

 when results using this conventional morphological characteristic were compared with immunodiffusion 

 results. Improved accuracy of searobin egg identification can be achieved in future ichthyoplankton studies 

 by using immunochemical techniques. A similar application of immunochemical identification techniques 

 should also better resolve classification uncertainties among other morphologically similar co-temporal 

 and co-spatial planktonic fish eggs. 



The accuracy of ichthyoplankton analysis is often 

 limited by the lack of reliable, distinguishing, mor- 

 phological characteristics that are useful for identi- 

 fying fish eggs and larvae. Conventional character- 

 istics used to identify fish eggs include egg and oil 

 globule diameters; number, distribution, and pigmen- 

 tation of oil globules; and pigmentation patterns on 

 developing embryos. However, overlapping diameters 

 of eggs and a similar if not identical number of oil 

 globules with comparable pigmentation and size 

 among closely related species impose a relatively 

 high degree of uncertainty concerning the identity 

 of planktonic fish eggs from many areas. Increased 

 accuracy has been more recently achieved through 

 the analysis of fish eggs using biochemical, im- 

 munological, and ontogenetic methods. Morgan 

 (1975) examined electrophoretic patterns of white 

 perch and striped bass egg extracts and found dif- 

 ferentiation was possible on this basis. Orlowski et 

 al. (1972) differentiated cunner, Tautogolabrus ad- 

 sperus, from tautog, Tautoga onitis, eggs using 

 monospecific antisera in microimmunodiffusion 

 analyses. The technique was especially useful with 

 early stage eggs which were morphologically iden- 

 tical. Ontogenetic methods allow careful study of 

 laboratory-reared eggs and larvae of known paren- 

 tage to document species-specific developmental 

 histories. These studies may provide new distin- 



1 Department of Biology, Lehigh University, Bethlehem, PA; pres- 

 ent address: E. I. du Pont de Nemours Co., Inc., Glasgow Research 

 Laboratory, Wilmington, DE 19898. 



department of Biology, Lehigh University, Bethlehem, PA 

 18015. 



guishing morphological features for future egg iden- 

 tifications. However, additional means are required 

 where well-documented features shared with other 

 species do not provide adequate differentiation of 

 field-collected eggs. 



This paper is a report on the results obtained from 

 a microimmunodiffusion analysis which successful- 

 ly differentiated the planktonic eggs of the north- 

 ern searobin, Prionotus carolinus, from those of the 

 striped searobin, Prionotus evolans, which were col- 

 lected from the Hereford Inlet estuary, southern 

 New Jersey, between May 1973 and September 1974 

 (Keirans 1977). Identifications based separately upon 

 immunochemical and morphological evidence were 

 also compared to evaluate the reliability of differen- 

 tiations based entirely upon conventional mor- 

 phology. Prionotus spp. were selected in our study 

 first because the searobins represent a large 

 breeding population which appears co-temporally 

 and co-spatially near shore to provide an abundant 

 source of gravid adults. Eggs of known parentage 

 became readily available for preparation of ex- 

 perimental reagents and specimens. Secondly, this 

 study would expand the application of microimmuno- 

 diffusion analysis to species differentiation as an ex- 

 tension of the study of Orlowski et al. (1972), which 

 documented differentiation of eggs from two genera. 

 Finally, the identification of Prionotus spp. ova has 

 never been properly resolved. 



Prionotus carolinus ova were described by Kuntz 

 and Radcliffe (1918) as highly transparent but slight- 

 ly yellowish spherical eggs ranging from 1.0 to 1.15 

 mm in diameter. The yolk sphere contained a 



Manuscript accepted March 1985. 



FISHERY BULLETIN: VOL. 84. NO. 1. 1986. 



63 



