between the label of Cat. No. 38619 in the 

 USNM and the statement of Wilson (1911: 

 359) : "There is but a single lot of this species, 

 which was taken from the northern swell-toad, 

 Spheroides maculatus, at Woods Hole, Massa- 

 chusetts, and is numbered 38619, U.S.N.M. It 

 includes three females, two of which bear egg- 

 strings." The label of Cat. No. 38619 clearly 

 says, however, that there are only "2 5 speci- 

 mens," the host is "Chilomycterus geometri- 

 cus." and no egfr strings were found in the vial. 

 Another USNM collection of T. corpulentus is 

 Cat. No. 79595. The label of this collection fits 

 better with Wilson's statement. It says that 

 there are "3 specimens" and the host is "Gills, 

 Spheroides maculatus," but the three specimens 

 of this collection are Pseudochondracanthus 

 diceraus Wilson. They are mature adult females 

 and all carry a pygmy male on their poster- 

 oventral surface. This collection was not men- 

 tioned by Wilson in any of his reports, not even 

 in his reports of P. dicemus (1908: 436; 1932: 

 496), but the label says "Identified by C. B. 

 Wilson." I have taken the two specimens kept 

 in the vial of Cat. No. 38619 as Wilson's type 

 specimens of T. corpulentus and synonymized 

 the species with T. impressus. 



One of the three immature adult females in 

 the vial of Cat. No. 38625 was obviously mis- 

 taken by Wilson for an adult male. The rather 

 small size, the different shape and proportion of 

 various body regions, and the two bean-shaped 

 reproductive organs inside the urosome might 

 suggest incorrectly a male, if the process of 

 metamorphosis in the female is unknown. The 

 pair of stout hooks described by Wilson on the 

 ventral surface at the posterior corners of the 

 genital segment of this "male" specimen are 

 merely two sclerotic protrusions (see fig. 3). 



NOTES ON METAMORPHOSIS 



The absence of the male parasites on the 

 diodontid and tetraodontid fishes perhaps oc- 

 curs because males do not grow beyond the 

 copepodid stage. They probably die after copu- 

 lation as do the males in the families Lernae- 

 idae, Lernaeoceridae, and Pennellidae, in which 

 only the female copepodid (after copulation) 

 attaches to the fish host and metamorpho.ses 

 into an adult. 



The two youngest females recovered from the 

 diodontid fish caught off Cape San Bias, Fla., 

 still show a cyclopoid form of body; they are 

 particularly remini.scent of bomolochid and 

 taeniacanthid copepods (see fig. 20). The 

 cephalothorax is the widest part of the body, 

 and the metasomal segments are still distin- 

 guishable (see table 3 for measurements). 

 These features, in comparison with the meta- 

 morphosed adult female, indicate that they are 

 either still in the last copepodid stage or, at 

 most, just on the way to metamorphosis. The 

 somewhat older females that I have in the 

 same collection are the nine copepods that show 

 no segmentation in the metasomal region, have 

 swollen trunks as wide as the head or a little 

 wider, and carry no egg sacs (see figs. 21, 22). 



T.iBLE 3. — Measurements of female copepodid from three 

 collections. 



Record and 

 body part 

 measured 



Specimen 1 



Host 



Locality 



Date 



Cephalothorax 



ihead) 



Thorax (neck 



+ trLink) 



Urosome 



("tail") 



Total 

 length.-. 



Mm. 



Chilo- 

 mycterus 

 schoepfi 



Panacea, 

 Fla. 



May 14, 1965 



0.27 by 0.37 



.30 by 0.26 



.17 by 0.23 



.70 



Specimen 2 I Specimen 3 



Specimen 4 



Mm. I Mm. Mm. 



Chilo- Chilo- I Cliilo- 



jjiycteriis \ myclerus myctfrus 



schofpfi I schofpft j anifnnntus 



Cape San ' Cape San Montego 

 ma.s, Fla, Hlas, Fla. 



May 16, 196,1 



0.31 by 0,41 



,34 by 0.32 



,16 by 0.23 



,81 



May 16, 1965 



0.30 by 0.42 



.36 by 0.31 



,17 by 0,21 



.83 



Hay, 



Jamaica 

 June 15, 1910 



0.31 by 0.47 



,41 by 0,37 



.15 by 0,23 



These females I have considered as the imma- 

 ture adults inasmuch as they have attained 

 ■sexual maturity and have copulated but have 

 not yet produced ef^g sacs. 



Metamorphosis occurs only in the cephalo- 

 thorax and the last two segments of the meta- 

 some. As far as the size and shape are con- 

 cerned, the second pedigerous segment and the 

 urosome in the copepodid are not significantly 

 different from the neck and the "tail" in the 

 immature adult female, nor in the ovigerous 

 female. The second thoracic segment, urosome, 

 and all appendages are not transformed during 

 metamorphosis, but the cephalothorax and the 

 third and fourth pedigerous segment are tre- 

 mendously changed. 



The size of the head of an immature adult 



294 



U.S. FISH AND WILDLIFE SERVICE 



