Brachyura and Anomura of Puget Sound — Knudsen 
23 
FAMILY MAJIDAE 
MOLTING: It has been suggested by Drach 
(1939:106-377) that the spider crab Maia 
squinado reaches what is known as a puberty 
molt, at which time no further molting occurs. 
At the time of the puberty molt crabs of the 
Majidae become sexually mature and then be- 
gin egg production. This is contrary to the 
other brachyuran families found in Puget Sound, 
for which molting continues after maturity. 
In order to test Drach’s theory for the Puget 
Sound majids a number of experiments and field 
observations were attempted. Animals were 
maintained in the laboratory for up to 9 
months without any molting. Such experiments 
became unsatisfactory in time as feeding and 
overcrowding became problems in the aquaria. 
A female Pugettia producta was encountered on 
November 14, just after having completed molt- 
ing, but the exuvium became lost before it was 
noted whether or not this was immature or 
mature. Several additional molts of this species 
and of other species of Puget Sound spider 
crabs were recorded, but in all cases these were 
either prepuberty molts or puberty molts and 
none demonstrated that molting occurs after the 
puberty molt. Likewise, no exuvia of mature 
females were ever located on the beaches, as 
were those for other families of crabs. 
If there is a puberty molt and the female 
spider crab autotomizes a leg either prior to or 
following the puberty molt, then regeneration 
(or at least complete regeneration) would be 
impossible. With this thesis in mind, a series 
of experiments and field observations was be- 
gun where mature animals with partially re- 
generated limbs were collected and maintained 
in the laboratory, and additional specimens were 
brought into the laboratory and were forced to 
autotomize limbs. In no case did any of the 
partially regenerated limbs continue to develop 
when additional molts were lacking, and no 
other method of regeneration was used. Freshly 
autotomized appendages of mature individ- 
uals showed the primary stages of regeneration 
which consist of scabbing, but no papillae or 
subsequent growth occurred. Thus, one must 
conclude that adults with partially regenerated 
limbs completed this regeneration prior to the 
puberty molt, at which time the growth ceased. 
Some inconclusive light was shed on this 
problem when specimens of P. producta were 
dissected. On one occasion a female which had 
recently completed hatching a brood of eggs 
died in the aquarium. This animal was dissected 
and it was noted that the spermatheca was com- 
pletely empty but that the ovaries were ex- 
tremely well developed and laden with "ripe” 
eggs. This demonstrated that a new reproductive 
cycle was in the making and suggested that a 
molt could occur at this time, as would be true 
for other families of crabs. However, no new 
integument was formed beneath the exoskeleton 
as can be seen in crabs about to molt. The 
old integument, moreover, was firmly attached 
to the exoskeleton, suggesting that no pre- 
molt metabolic activity was occurring. Numer- 
ous field dissections gave the same data. 
A size differential found in sexually mature 
females of P. producta suggests either that the 
number of molts prior to the puberty molt is 
not consistent in all specimens, or that molting 
may continue after sexual maturity is reached. 
Another somewhat negative point is found in 
the encrusting organisms living as commensals 
on the carapace of Pugettia. The majority of the 
specimens bearing eggs have no encrusting or- 
ganisms such as barnacles on the carapace, 
which suggests that these animals have recently 
molted. Whether or not this molt was the 
puberty molt is unknown. Some individuals, on 
the other hand, have barnacles which appear to 
be far larger than one-year old animals and 
suggest that they have been growing on the 
carapace for more than a year. This tends to rule 
out the fact that these individuals have molted 
in the recent past. Although all of these data 
are somewhat negative and could readily be 
ruled out by one positive datum, they strongly 
support the theory that spider crabs cease molt- 
ing following sexual maturity. 
Pugettia gracilis 
HABITAT: The graceful kelp crab, Pugettia 
gracilis, ranges from the western extremity of 
the Aleutian Islands eastward and southward to 
Monterey Bay (Garth, 1958:196-197), and 
from the intertidal zone down to about 40 
fathoms (Way, 1917:371). Way records it as 
being abundant everywhere in the Friday Har- 
