BULLETIN OF MARINE SCIENCE, 27(4): 704-728, 1977 LARVAL DEVELOPMENT OF CALLINECTES SIMILIS REARED IN THE LABORATORY C. G. Bookhout and J. D. Costlow, Jr. ABSTRACT Freshly hatched larvae of Callinectes similis Williams, the lesser blue crab, were reared to the first crab stage. Eight zoeal stages and one megalopa stage are described with par- ticular reference to types of setae on appendages. Updated information on the develop- ment of the commercial blue crab, Callinectes sapidus Rathbun, is also given, as well as similarities and differences between C. similis and C. sapidus. The zoeae of C. similis and C. sapidus are so similar that they can only be separated by a number of minor differences. The dorsal spine of C. similis is significantly longer than that of C. sapidus in all zoeal stages. Other structures, such as the rostrum and antennae, are either longer in early zoeal stages of C. sapidus than in C. simi/is, or the structures of the two species are not significantly different. In later stages, however, structures measured were gen- erally significantly longer in C. similis than in C. sapidus. Also in later zoeal stages, there are generally small differences in setation of appendages. There are diagnostic differences in lengths of parts of the claw of the first leg and setation of pleopods of the megalopa of the two species. There are also minor differences in the setae of the scaphognathite, in seta of the epipodite of the 3rd maxilliped and in aesthetascs of antennules of the two species. A number of genera, Callinectes, Portu- to the megalopa stage: Portunus pelagicus nus, and Arenaeus, belonging to the subfam- (Linnaeus) (Kurata and Midorikawa, 1975) ily Portuninae, are found in North Carolina and Thalamita sima (Herbst) (Kurata, 1975). waters (Williams, 1965), but the complete Attempts to rear other species of Portunus, larval development of only Callinectes sapi- Charybdis, and Thalamita of Japanese wa- dus Rathbun (Costlow and Bookhout, ters to crab or megalopa have failed. 1959) and Portunus spinicarpus (Stimpson) The present study is part of a general pro- (Bookhout and Costlow, 1974) have been gram to rear all species of Portuninae in the described from rearing. North Carolina waters from hatching to first The swimming crabs of the subfamily crab stage. Until this is done it is unlikely Portuninae comprise one of the most domi- that one could determine the larval distribu- nant groups of crabs which support impor- tion of the commercially important blue crab, tant fisheries along the Pacific, East China because the larvae of the subfamily Portuni- Sea, and Japan Sea coasts. Hence, there nae are so similar that it is difficult to distin- have been intensive efforts to rear species guish species. Kurata (1975) also notcd of Portunus, Charybdis, and Thalamita in that zoeae of Portuninac are so much alike the laboratory (Yatsuzuka, 1952, 1957; that the identification of species is practically Kurata, 1975; Kurata and Nishina, 1975; impossible without studying almost every and Kurata and Midorikawa, 1975). The minor difference. only Japanese species of Portuninae which The current study deals with the larval have been reared from hatching to first crab development of Callinectes similis Williams, are Charybdis japonica A. Milne Edward the lesser blue crab. It is difficult to distin- (Yatsuzuka, 1952, 1957) and Portunus tri- guish immature males and adult females of tuberculatus Miers (Kurata, 1975). How- C. similis from C. ornatus Ordway and C. ever, two Japanese species have been reared danae Smith (Williams, 1974). The geo- 704 BOOKHOUT AND COSTLOW: LARVAL DEVELOPMENT OF CALLINECTES SlMILlS 705 graphical distribution of C. similis is from were changed daily to clean bowls of sea- Delaware Bay to Key West, Florida, and water and fed one medicine dropper full of from northwestern Florida around the Gulf Arbacia embryos and the same volume of of Mexico to Campeche, Yucatan. Callinec- freshly hatched nauplii of Artemia salina tes ornatus is also found off the North Caro- hatched from San Francisco eggs. Larvae lina coast but its range is from North Caro- of C. similis are so small that they can con- lina through southern Florida, northwestern sume only parts of Artemia nauplii. Hence, Yucatan to Estado de Sao Paulo, Brazil, and the smaller Arbacia embryos serve as a valu- Bermuda. Callinectes danae does not occur able food supplement. off the North Carolina coast but has a Larvae were fixed at each developmental range from southern Florida and eastern stage in 70% alcohol and also in 70% ethyl- side of Yucatan Peninsula to Estado do ene glycol. Chromatophore patterns were Santa Catarina, Brazil, and is also found in sketched from the Jiving zoeae and megalopa. Bermuda (Williams, 1974). C. similis is, Drawings of larvae and their appendages therefore, the most northern species of the were made from fixed larvae and preserved three and is usually found in salinities above exuviae. Appendages were dissected and 15%0 in North Carolina and Florida. In mounted on slides in ethanol and glycerine. Mississippi Franks et al. (1972) reported Drawings were made on squared paper with that C. similis was caught in trawl samples the aid of a Whipple disc mounted in an at depths from 9 to 92 m at temperatures ocular of a compound microscope. The from 13.2 to 29.0°C and in salinities rang- Whipple disc was calibrated with a stage ing from 24.9 to 37.4%". micrometer. Whole mounts were examined The major objectives of this investigation under a magnification of 100x and appen- were: ( 1) to rear C. similis from the time dages under 200x. Details of appendages of hatching until the first crab stage is and setae were studied under a magnification reached; (2) to give a detailed description of 400x and under oil immersion lens. of each larval stage with emphasis on the Measurements of the combined carapace number and type of setae on each appen- and abdominal lengths, lengths of antennae, dage; and (3) to determine the chief charac- lengths of rostral and dorsal spines and teristics which distinguish the larvae of C. widths between lateral carapace spines were similis from C. sapidus. made to determine if there were significant differences between larvae of C. similis and MATERIALS AND METHODS C. sapidus. Ten C. sapidus larvae hatched from one mother crab and 10 C. similis Ovigerous Callinectes similis were col- larvae hatched from each of three different lected in trawl samples in the vicinity of the mother crabs, designated as C. simi, C. sim2, Beaufort Inlet, North Carolina. In the lab- and C. sima, were measured (Table 1). oratory, eggs were removed from the female, Similar measurements were made of larvae washed and placed in flasks or in compart- in zoeal stages II-V. Not enough larvae mented boxes of filtered seawater at a salin- ity of 30%c. The containers of eggs were from C. sim2 survived to measure after stage maintained on an Eberbach variable speed V or from C. sima after zoeal stage VII. shaker until hatching, following the proce- Hence, comparison between C. sapidus and dure described by Costlow and Bookhout C. similis were between 10 larvae of each (1960). After hatching, the larvae were species in zoeal stage VIII and megalopa reared in mass cultures. Initially about 700 (Table 1). A single classification ANOV A newly hatched larvae were placed in large with equal sample sizes was calculated and finger bowls (19.4-cm diam) containing a comparison of means was made to deter- 307<" filtered seawater. The living larvae mine if the means of each structure mea- 706 BULLETIN OF MARINE SCIENCE, VOL. 27, NO.4, 1977 sured in C. sapidus were significantly differ- ent from the means of similar structures in C. similis. Measurements of the total length were made from the base of the rostrum to the c~ end of the telson. This was calculated by the addition of carapace length with the ab- dominal length from the middle of the sec- D ond segment, where it emerges from the posterior margin of the carapace, to the pos- terior tip of the telson. Measurements were E made of the dorsal spine from the point of emergence from the carapace to the tip, the rostral spine from the frontal edge of the orbital socket to the tip, and the antenna from the point of articulation with the cara- pace to the tip. The spine tip width was F calculated as the distance between the tips G of lateral carapace spines as seen from frontal view. RESULTS Types of setae Figure 1, A-E This is the second paper in which there Figure 1. A-E. Additional types of setae on has been an attempt to determine the type developmental stages of Subfamily Portuninac not reported by Bookhout and Costlow, 1974. F-G. and location of setae on all appendages in Frontal views of lOeal stage I of C. similis and the development of a crab following the ter- C. sapidus: A, papillate; B, stout serrate; C, minology used by Thomas (1970) in his heavy toothed serrate; D, long toothed serrate; study of setae of crayfish, Austropotamobius E. fine serrate; F, frontal view of C. similis; G, pallipes (Lereboullet) . In the first paper, frontal view of C. sapidlls. the larval development of Portunus spini- carpus (Bookhout and Costlow, 1974), most types of setae found in the development of four types of serrate setae on the 3rd maxil- crabs in the subfamily Portuninae were de- liped of the megalopa of C. similis and P. scribed. During the course of the current spinicarpus: (a) stout serrate seta has a study several additional types were observed heavy shaft with horn-shaped, forward-pro- jecting serrations along the shaft (Fig.