FISHERY BULLETIN : VOL. 81, NO. 4 



herbstii, s.s., P. simpsoni, P. obesus, and P. lacustris 

 from throughout their ranges as determined from the 

 series in the USNM. Characters of the chelae were 

 noted as these measurements were made, and it was 

 seen that the specimens assorted into two apparent 

 groups: 1) Those with major chelae in which cusps on 

 the fixed finger almost always reached or fell below 

 (rarely exceeded) a straight line drawn between its 

 tip and the angle formed by its base and the anterior 

 margin of the palm — the herbstii-simpsoni group, and 

 2 ) those with major chelae in which some cusps on the 

 fixed finger were raised above or exceeded such a 

 line (if the chela was not regenerating or other- 

 wise altered) — the lacustris-austrobesus-obesus 

 group. 



Members of the first group have a carapace which is 

 relatively narrower than those of the second group 

 (Tables 1-2, Fig. 9), P. simpsoni being the narrowest 

 of all, ( a point made by Rathbun 1930), the regression 

 line describing this width-length relationship cutting 

 across analogous lines for the other species. 

 Moreover, the major chela of P. simpsoni is relatively 

 larger than that of P. herbstii, an observation that is 

 difficult to quantify but one that can be expressed by 

 the relationship of the height of the anterior margin of 

 the palm (i.e., region above articular condyle of dac- 

 tyl) to the length of the fixed finger. This relationship 

 is greater in P. simpsoni (>0.80) than in P. herbstii 

 (<0.70). In addition, both of these species have 

 similarly smooth surface granulation; variably mot- 

 tled dorsal coloration; and third maxillipeds with a 

 basal red spot on the internal surface of the ischium 

 in males, in about 50 f /r of female P. herbstii (see 



FIGURE 9.— Proportional values and basic statistics for length per- 

 cent width for samples of six species of Panopeus from the west em 

 Atlantic. Top row of numbers = N in samples, vertical bars = range, 

 horizontal bars = mean, open rectangles = SD. 



Williams 1965), but never in females of P. simpsoni 

 (see Heard 1982). 



Rathbun (1930) conceived the center of distribu- 

 tion for P. simpsoni to be the northern Gulf of Mexico, 

 but she considered some specimens from South Car- 

 olina to belong to this group as well and found 

 specimens of P. herbstii from Virginia to vary toward 

 P. simpsoni. Panopeus herbstii exhibits considerable 

 variation in form of the anterolateral teeth, some 

 specimens from South Carolina resembling in acute- 

 ness those of P. simpsoni, as do other specimens from 

 as far north as New Jersey. Among such variants are 

 females with internal red spots on the ischium of the 

 third maxillipeds. On the whole, the Atlantic P. 

 herbstii is morphologically distinct from the Gulf of 

 Mexico P. simpsoni, as confirmed by electrophoretic 

 patterns of the respective hemocyanins (Sullivan et 

 al. 1983). 



Members of the second group are relatively larger 

 and more robust than those of the first group, more 

 coarsely granular on carapace and chelipeds, and 

 they share curious veined or reticulate patterns of 

 coloration on the outer surface of the chelae which 

 often extend from the upper to lower margin of the 

 palms. This pattern is rarely seen in members of 

 group 1. Both males and females have a proximal red 

 spot on the inner surface of the ischium of the 

 third maxilliped. 



Teeth of the fixed finger of the major chela (except 

 for certain regenerated examples) are developed into 

 a conspicuous raised "molar area" in the proximal 

 and middle parts of the prehensile edge. This 

 development is extreme in P. lacustris in which teeth 

 of the molar area are impacted, often worn flat at 

 their crowns, and broadened such that their lateral 

 faces and that of the adjacent finger are bowed or 

 swollen laterally. This development is seen in either 

 right- or left-handed individuals, but some, evidently 

 with chelae in an intermediate stage of development 

 or regeneration, do not exhibit the extreme molar 

 development. Panopeus obesus has the molar area 

 developed but its teeth are not impacted or con- 

 spicuously broadened and are arranged in line 

 with the axis of the finger; the fingers are relatively 

 longer than those of P. lacustris. A counterpart to 

 the tooth pattern of P. obesus is found in P. 

 austrobesus.. 



The carapace of P. obesus tends to be tumid, with 

 rounded anterolateral teeth; P. lacustris has a less 

 tumid carapace, with regions often well developed 

 and angular anterolateral teeth; the carapace of P. 

 austrobesus resembles the latter, but is somewhat 

 less strongly developed. Rathbun (1930) tacitly 

 recognized this southern Brazilian population in that 



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