68 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



MESIAL COXOPODITE ADDUCTOR MUSCLE OF 

 FIRST MAXILLA 



Figure 40 



Arising from the large sternal apodeme of the 

 coxopodite promotor muscle, the first maxilla 

 mesial (= medial) coxopodite adductor muscle 

 (fig. 40) inserts in the coxopodite. The muscle 

 functions to turn the first maxilla to the midline, 

 thus bringing the opposing gnathal lobes together. 

 The first maxilla mesial coxopodite adductor mus- 

 cle in Penaeus is the same muscle as the musculus 

 adductor medialis coxopoditis I maxillae in 

 Astacus and Pandalus. Callinectes does not ap- 

 pear to have this muscle. 



ANTERIOR COXOPODITE ADDUCTOR MUSCLE OF 

 FIRST MAXILLA 



Figure 40 



The first maxilla anterior coxopodite adductor 

 muscle (fig. 40) originates on the laterotergal 

 plate adjacent to the origin of the lateral coxopo- 

 dite adductor muscle. The muscle passes antero- 

 ventrally, diverging from the lateral adductor, 

 and inserts somewhat anteriorly of the insertion 

 of the lateral adductor. Together with the 

 medial and lateral coxopodite muscles, the an- 

 terior adductor closes the gnathal lobes of the 

 first maxilla. The anterior adductor is not evi- 

 dent in Astacus or Pandahtx, but does appear in 

 Callinectes. 



COXOPODITE ABDUCTOR MUSCLE OF FIRST 

 MAXILLA 



Figure 40 



The first maxilla coxopodite abductor muscle 

 (fig. 40) originates with the anterior and lateral 

 adductor muscles on the laterotergal wall. The 

 muscle runs anteriorly and inserts in the lateral 

 lobe of the coxopodite. Upon contraction, the 

 muscle pulls the first maxilla away from the mid- 

 line, opening the gnathal lobes. The coxopodite 

 abductor muscle is found in Pandalus, Astacus, 

 and Callinectes. 



COXOPODITE LEVATOR MUSCLE OF FIRST 

 MAXILLA 



Figure 40 



The first maxilla coxopodite levator muscle 

 (fig. 40) is attached to the sternal apodeme upon 

 which the medial adductor and the promotor and 



remotor muscles originate. It inserts on the cox- 

 opodite. The angle of the muscle attachment 

 is such that its contractions raise the first max- 

 illa. The same muscle as the coxopodite levator 

 in Penaeus appears in Astacus, Pandalus, and 

 Callinectes. 



COXOPODITE DEPRESSOR MUSCLE OF FIRST 

 MAXILLA 



Figure 40 



The first maxilla coxopodite depressor muscle 

 (fig. 40) originates on the base of the sternal 

 apodeme mentioned above. The muscle runs to its 

 insertion on the coxopodite so that its contractions 

 draw the first maxilla ventrad, thereby lowering 

 the gnathal lobes away from the mandibles and 

 paragnatha. The coxopodite depressor muscle ex- 

 ists in the other crustaceans referred to above. 



ENDITE ADDUCTOR MUSCLE OF FIRST MAXILLA 



Figure 40 



Intrinsic to the endite of the basipodite is a 

 group of muscles, the first maxilla endite adductor 

 muscle (fig. 40), which pass across the proximal 

 neck of the gnathal lobe of the basipodite to the 

 base of the endite flagellum. The muscle bends 

 the flagellum mesad. The endite adductor muscle 

 is common to the first maxilla of Penaeus, Panda- 

 lus, Astacus, and Callinectes. 



DORSOVENTRAL MAXILLARY TENSOR MUSCLE 



Figures 33, 34, 35, 37 



This muscle originates by a broad, fan-shaped 

 apodeme in the connective tissue of the dorsal cara- 

 pace just laterad of the gastric mill (fig. 35) . The 

 apodeme runs ventromedially to the small dorso- 

 ventral maxillary tensor muscle (fig. 37) lying 

 laterad of the muscle of the dorsoventral mandibu- 

 lar ligament and closely applied to it. Schmidt 

 (1915) described the muscle as the anterior dorso- 

 ventral muscle in Astacus and Berkeley (1928) 

 has followed this terminologly in her work on 

 Pandalus dan-ae. Grobben (1917) studied the 

 muscle in species of Penaeus, Palaemon, Leander, 

 and Pandalus, and concluded that, on grounds of 

 its innervation by nerves of the first maxilla, the 

 muscle should be renamed the "dorsoventral max- 

 illary tensor muscle." The name given by Grob- 

 ben is adopted here. 



