. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NEUROHAEMAL ORGANS IN BRACHYURA 321 esophagus. heart FIGURE 2. Dissection of preserved Caliinectes ornatus showing location of pericardia! organs and anterior ramifications. Digestive gland, stomach, and bladder removed. Amm, musculus abductor maior mandibulae; AR, anterior ramifications; lig, ligament; mdp, musculus dorsoventralis posterior; mvst, musculi ventrales superficiales thoracis; pcllm, musculus proximalis coxopoditis II maxillae; PO, pericardial organ; ri, recurrent integumentary nerve; sn 1, first segmental nerve
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NEUROHAEMAL ORGANS IN BRACHYURA 321 esophagus. heart FIGURE 2. Dissection of preserved Caliinectes ornatus showing location of pericardia! organs and anterior ramifications. Digestive gland, stomach, and bladder removed. Amm, musculus abductor maior mandibulae; AR, anterior ramifications; lig, ligament; mdp, musculus dorsoventralis posterior; mvst, musculi ventrales superficiales thoracis; pcllm, musculus proximalis coxopoditis II maxillae; PO, pericardial organ; ri, recurrent integumentary nerve; sn 1, first segmental nerve; tg, thoracic ganglia. The region bounded by a rectangle to the right of the esophagus is enlarged in Figure 3. Several overlying muscles and ligaments have been removed on the left half of the dissection. anteriorly and laterally together to the endopleurite of the last head segment. There they pass upward through a ligament loop and angle more laterally toward the musculus dorsoventralis posterior (mdp). The integumentary nerve is often medial and anterior to the segmental nerve at this point. After passing through the liga- ment loop, and usually before passing beyond the mdp, the first segmental nerve gives off two branches. One angles posteriorly to the muscles attached to ligaments overlying the ventral nerve mass (musculi ventrales superficiales thoracis, Fig. 6), the other larger branch runs anteriorly beneath and beyond the mdp where it pro- ceeds to break up into a network or plexus, the anterior ramifications. These apparently lie beneath a sinus membrane separating the ventral respiratory muscles from the dorsal thoracic cavity. Portions of the AR may dip ventrally in blood spaces between the muscles, or ma}- spread over the membranes covering skeletal elements in the region or over the surface of a nerve (Fig. 3) apparently passing out toward the Y-organ and muscles of the mandible (Echalier, 1959). The form of the AR varies among species; for example, in Caliinec
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
