74 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



PROTOPODITE PROMOTOR MUSCLES OF FIRST 

 MAXILLIPED 



Figures 42, 43 



The protopodite promoter muscles (fig. 43) orig- 

 inate on the small sternal apodemes (para- 

 phragms) arising from the sternal braehia be- 

 tween the first and second maxillipeds. The long- 

 er, medial promotor inserts on an apodeme on the 

 anterior wall of the protopodite and the lateral 

 promotor inserts in connective tissue ventrad of 

 the medial promotor. Contractions of the promot- 

 ors turn the first maxilliped forward and dorsad 

 about a transverse axis. The protopodite promot- 

 ors of Penaeus are very likely homologous with 

 the lateral and medial promotor muscles of Asta- 

 cus, Callinectes, and Pandalus. 



PROTOPODITE LEVATOR MUSCLES OF FIRST 

 MAXILLIPED 



Figure 43 



Penaeus has at least three protopodite levator 

 muscles. All of them take origin on a small sternal 

 apodeme overhanging the medial margin of the 

 maxillipedal foramen. They fan out as they pass 

 laterally to insert in connective tissue in the lateral 

 part of the coxopodite. Contractions of the pro- 

 topodite levators lift the dorsal edges of the coxop- 

 odite exites dorsad. At least a part of this mus- 

 cle group is homologous with the levator muscle of 

 Pandalus, Astacus, and Callinectes. 



COXOPODITE ADDUCTOR MUSCLE OF FIRST 

 MAXILLIPED 



Figure 43 



Taking origin in the proximal region of the 

 coxopodite, the coxopodite adductor muscle passes 

 ventrad along the medial wall of the coxopodite 

 to insert on the coxopodite endite. Upon contrac- 

 tion, the muscle turns the endite mesad. The cox- 

 opodite adductor in Penaeus appears to be the 

 maxillipedal depressor muscle of Astacus and 

 Pandalus, and possibly one of the small unknown 

 muscles in the coxopodite of Callinectes. 



COXOPODITE ABDUCTOR MUSCLES OF FIRST 

 MAXILLIPED 



Figure 43 



Two coxopodite abductor muscles exist in the 

 first maxilliped of Penaeus. The muscles origi- 

 nate in the lateral part of the coxopodite, near 



the posterior exite, and run ventromedially to a 

 point of insertion on the lateral margin of the 

 coxopodite endite. Their contractions draw the 

 endite laterad, in opposition to the coxopodite ad- 

 ductors. The endopodite reductor muscle of Asta- 

 cus is a possible homolog of the coxopodite ab- 

 ductor in Penaeus. 



EXITE ATTRACTOR MUSCLES OF FIRST 

 MAXILLIPED 



Figure 43 



The first maxilliped of Penaeus contains at least 

 two exite attractor muscles which pull the cox- 

 opodite exites caudad. The muscles originate on 

 apodemes of the sternal braehia and insert on 

 the medial margin of the posterior coxopodite 

 exite. The epipodite attractor muscle in Astacus 

 is very likely the homolog of the exite attractors 

 of Penaeus. 



EXOPODITE ADDUCTOR MUSCLE OF FIRST 

 MAXILLIPED 



Figure 43 



The flagellum, or exopodite, of the first maxil- 

 liped is moved towards the midline by means of 

 a short muscle, the exopodite adductor muscle, 

 which originates at the base of the exopodite and 

 runs distally within the structure. The homolog 

 in Astacus is the exopodite adductor muscle. 



EXOPODITE ABDUCTOR MUSCLE OF FIRST 

 MAXILLIPED 



Figure 43 



The exopodite abductor muscle originates at 

 the distal end of the exopodite adductor and runs 

 distally in the flagellum. Its contractions tend to 

 straighten the flagellum, thus turning the struc- 

 ture laterad. The muscle in Penaeus is in all 

 probability the flagellum muscle of Astacus. 



4b. Second Maxilliped 



The structure of the second maxilliped is much 

 more like that of the typical arthroappendage 

 than the anterior gnathal appendages already 

 treated. The typical number of appendage arti- 

 cles are found, albeit those of the basipodite and 

 ischiopodite are fused. A large, flagellar exopo- 

 dite is developed. A notable difference is that 

 some of the endopodite articulations of the second 

 maxilliped permit far more extensive movements 

 than do the hinges of the anterior gnathal iimbs. 



