FISHERY BULLETIN: VOL. 75, NO. 1 



red crabs was quantified by measuring ovary 

 volume and deriving gonad indices (Giese and 

 Pearse 1974) for the various stages. Certain ovar- 

 ian samples were selected on the basis of relative 

 size and color and treated in the following manner. 

 Displacement of ovaries was measured by placing 

 the entire, excised ovary in volumetrically 

 graduated tubes containing a known quantity of 

 seawater. Ovary volume (V in milliliters) was 

 used to compute a gonad index: G, = (Ovary 

 weight)/* Total body weight) x 100, where weights 

 in grams were calculated as follows Ovary weight 

 = 1.025 V , assuming ovarian specific gravity 

 equals that of seawater. Total body weight was 

 derived from the following relationship based on 

 measurements of 142 females: log body weight = 

 -3.134 + 2.8833 log length, r = 0.968. 



Portions of the ovaries were then preserved in 

 Davidson's fixative for histological processing and 

 in Gilson's fluid (Bagenal and Braum 1971) for 

 measurement of ova size. 



Histological sections were stained in 

 haematoxylin and eosin and mounted in Per- 

 mount. 7 Descriptions of developmental stages 

 were made from the resultant slides. 



Samples in Gilson's fluid were shaken to release 

 ova which were then observed with a dissecting 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



microscope. The diameters of 20 spherical ova 

 from each sample were measured with a cali- 

 brated ocular micrometer. Misshapen ova were 

 not considered. Similarly, 20 extruded eggs from 

 11 ovigerous crabs were removed and measured 

 (length and width). A mean diameter was com- 

 puted for each crab. 



RESULTS AND DISCUSSION 



The Ovary 



The following account of the gross morphology 

 and histology of the red crab ovary is based on 

 examination of the gross anatomy of 255 crabs and 

 on histological preparations from 34 crabs. 



The ovary is an H-shaped organ located dorsally 

 just beneath the carapace (Figure 1). Two horns 

 extend anterolateral^ from either side of the 

 gastric mill and lie dorsal to the hepatopancreas. 

 At the posterolateral borders of the gastric mill, 

 near the origin of the posterior mandibular muscle 

 bundles, the anterior horns are joined by a 

 commissure. Two posterior horns, which lie ven- 

 tral to the heart, extend posteriorly on either side 

 of the intestine. The seminal receptacles arise 

 from the midlateral border of the posterior horns 

 and open externally through gonopores (vulvae) 

 on thoracic sternite VI, immediately adjacent to 

 sternite V. 



FIGURE 1. — Dorsal dissection of 

 female Geryon quinquedens. Heart 

 and medial portion of branchial 

 chamber removed. Anterior (aov), 

 posterior (pov) and commissure (cov) 

 of ovary, gastric mill (g), gill (br), 

 intestine (i), hepatopancreas (hp), 

 seminal receptacle (sr), midgut caeca 

 (mc). 



92 



