BULLETIN OF MARINE SCIENCE, 42(1): 101-132, 1988 LARVAL DEVELOPMENT OF THE SPECKLED SWIMMING CRAB, ARENAEUS CRIBRARIUS (DECAPODA: BRACHYURA: PORTUNIDAE) REARED IN THE LABORATORY Kenneth C. Stuck and Frank M. Truesdale ABSTRACT Eight zoeal stages and a megalopa of the speckled swimming crab, Arenaeus cribrarius, are described and figured from larvae of an ovigerous specimen collected at Hom Island, Mis- sissippi (Gulf of Mexico). Crab stages 1-3 are also briefly described. Larvae were reared at 25°C and 300/00salinity; some individuals completed zoeal development in 30 days,and reached crab I, 13 days later. Zoea I characters of A. cribrarius are compared with those of seven other species of shallow water Gulf Portuninae, from larvae reared by the authors, and from the literature. Antennal and telson features are important in distinguishing among zoeae I ofGulfPortuninae. Characters ofzoeae II-VIII and the megalopa of A. cribrarius and those of corresponding stages of Callinecles sapidus, C. similis. and PorlUnus spinicarpus from the literature are compared. In zoeae III and VI, setation of maxillar basal and coxal endites is a distinguishing feature among A. cribrarius, C. sapidus, C. similis, and P. spinicarpus, and in zoea V, maxillular basal and coxal endite setation distinguish each. Antennular aesthetasc formula distinguishes each species having a zoea VIII, and in all zoeal stages this feature distinguishes A. cribrarius from the others. Zoeae IV and VII of C. sapidus, C. similis and P. spinicarpus can be separated by setation of maxillular basal and coxal endites, and in zoea II this same feature distinguishes P. spinicarpus from C. sapidus and C. similis. Zoeae II of C. sapidus and C. simi/is from Atlantic stocks can be separated by maxilliped I endopod setation, but zoeae II of these species from the Gulf are presently inseparable. The megalopa of A. cribrarius is larger (carapace width, length) than those ofthe other three species. Megalo- pae of all four species can be reliably separated by number of hooked setae on pereopod 5 dactylus. The spawning season of A. cribrarius in the Gulf of Mexico extends at least from mid-April to mid-October. The speckled swimming crab, Arenaeus cribrarius (Lamarck, 1818), is known from Vineyard Sound, Massachusetts, to La Paloma, Uruguay (Juanico, 1978; Williams, 1984). Although a large crab, up to 154 mm carapace width (Williams, 1984), and common along southeastern U,S. Atlantic and Gulf of Mexico beaches (Gunter, 1950; Wass, 1955; Anderson et al., 1977; Leber, 1982), little is known of its life history, especially in the Gulf of Mexico. The portuninid genera Arenaeus Dana, Callinectes Stimpson, Cronius Stimp- son, and Portunus Weber are known to occur in the Gulf (Felder, 1973; Powers, 1977). The first zoeal stage of at least one species has been described for each genus except Cronius. For species from the Gulf, complete larval development in the laboratory is known for C. sapidus Rathbun, 1896; C. similis Williams, 1966; and P. spinicarpus (Stimpson, 1871) (see Costlow and Bookhout, 1959; Bookhout and Costlow, 1974; 1977). Partial descriptions from laboratory hatched larvae are available for zoeae I-III of P. gibbesii (Stimpson, 1859) (see Kurata, 1970) and for zoea I of P. depressifrons (Stimpson, 1859) (see Lebour, 1944), P. sayi (Gibbes, 1850) (see Lebour, 1944; Kurata, 1970), and P. spinimanus Latreille, J 8 J 9 (see Lebour, J 950). Sandifer (1972) provided a detailed description of a laboratory hatched zoea I of A. cribrarius. Two reports specifically mention the occurrence of A. cribrarius in the plankton. Goy (1976) reported zoeae I of A. cribrarius from plankton samples at two stations lOl 102 BULLETIN OF MARINE SCIENCE, VOL. 42, NO. I, 1988 DL TL cw TL Frontal View Dorsal View Zoea I Megalope Figure I. Schematic of portuninid zoea I and megalopa indicating: total length (TL); total spine length (TSL); rostral length (RL); dorsal spine length (DL); spine width (SW); carapace length (CL); length oftelson (LT); telson width (TW) telson fork length (FL); outer telson spines (0,1-3); inner telson spines (I, 1-3); and central arch of telson (CA). in the mouth of Chesapeake Bay, in July, and Truesdale and Andryszak (1983) reported megalopae of A. cribrarius from two stations in the northern Gulf, east of the Mississippi River delta. On the other hand, Sandifer (1975) cautioned that Callinectes spp. larvae reported in plankton studies off the southeastern U.S. coast might be a mixture of not only species of Callinectes, but also of Portunus spp. and A. cribrarius. In the present study, we describe the complete larval (zoeae I-VIII and mega- lopa) development ofA. cribrarius and briefly describe crab stages 1-3. To facilitate identification of portuninid first zoeae from plankton samples, particularly Gulf samples, we compare zoea I of A. cribrarius with those of some other Gulf species (c. sapidus, C. similis, Portunus depressifrons, P. gibbesii, P. sayi, P. spinicarpus, and P. spinimanus) using our own and published descriptions. We also compare A. cribrarius zoeae II-VIII and the megalopa with published descriptions of cor- responding larvae for C. sapidus, C. similis, and P. spinicarpus. Collection of ovigerous A. cribrarius during this study allowed us to elaborate its northern Gulf spawning season. This paper is the first in a projected series describing larval development of portunids from the Gulf of Mexico, intended to aid researchers studying larval recruitment of the commercially important blue crab C. sapidus. STUCK AND TRUESDALE: LARVAL DEVELOPMENT OF ARENAEUS CR/BRARlUS 103 Table I. Duration and survival of larval stages of Arenaeus cribrarius at 25°C and 300/00salinity Duration (days) No. moiling Stage Minimum X Mode Maximum Died in molt to next stage Zoea I 4 5.1 5 6 9 Zoea II 4 5.4 6 6 7 Zoea III 3 4.0 4 5 6 Zoea IV 4 4.3 4 6 6 Zoea V 3 3.5 3 5 6 Zoea VI 5 5.4 5 6 5 Zoea VII 3 4.5 6 4 Zoea VIII 2 3 3 4 4 Megalopa MATERIALS AND METHODS An ovigerous specimen of A. cribrarius was collected in the surf zone of Horn Island, Jackson County, Mississippi, 0.8 km east of Dog Keys Pass on the night of 28 April 1982. The eggs hatched during the night of 29 April 1982. Larvae were placed, one per compartment, into an 18-compart- mcnted polystyrene tray. Approximately 200 larvae were mass cultured in each of three IO-cm diameter glass finger bowls. Megalopae obtained in mass culture were separated into individual finger bowls. Tray and bowls were placed in a constant temperature unit at 25°C with a 12-h photoperiod. Aged scawater (300/00salinity), filtered through a I-Itm filter to which 50 mg per liter streptomycin sulfate and 40 mg per liter penicillin had been added, was changed daily in each compartment and bowl. Larvae were fed daily the following diet: zoeae I-III, rotifers (Brachionus plicatilis); zoeae IV-VI, a mixture of rotifers and frcshly hatched brine shrimp nauplii; zoeae VI-VIII, brinc shrimp nauplii only; megalopa and crabs, pieces of penaeid shrimp abdominal tissue. Exuviae, dead larvae, and a developmental series from the mass culture were initially preserved in 5% buffered formalin and later transfcrred to 70% ethanol. At least six specimens were measured and dissected for each stage, zoea through megalopa. Seven crab I specimens were measured, but only two specimens of crab 2, and one of crab 3. Ovigerous females of the following species were collected in Mississippi Sound or nearshore Gulf waters on the dates indicated: A. cribrarius, 12 August 1981; C. sapidus, I September 1982; C. similis, I August 1981; P. gibbesii. 20 August 1981; P. sayi. 12 August 1984; P. spinimanus, 14 October 1982; and P. spinicarpus, 14 October 1982. Zoea I larvae were subsequently obtained from laboratory or shipboard hatchings. At least five zoea I specimens of each species were examined and measured. Measurements ofzoeal and megalopal stages were adapted from Kurata (1975) and were made with an ocular micrometer using a dissection microscope as indicated in Figure I. Carapace width (CW) for crab stages was measured between lateral carapace spines. A developmental series of zoea I through crab 3 has been deposited in the National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM 373829). RESULTS OF THE REARING EXPERIMENT No prezoeae were observed; eight zoeal stages followed by a megalopa were observed among tray-reared specimens. In mass culture, a few specimens appeared to share characteristics of both zoeae VI and VII. Table I summarizes duration of instars for tray-reared larvae. Although no tray-reared larvae survived to mega- lopa, zoea VIII larvae died in molt to megalopa 34-40 days after hatching. In mass culture, viable megalopae were obtained in 30 days, and crab 1 specimens, 13 days later. Types of Setae. - Setae types recognized on the appendages of the zoeae and megalopa of A. cribrarius were similar to those described and figured by Bookhout and Costlow (1974; 1977) with three exceptions. We defined a sparsely plumose seta (Fig. 2D)-slender bearing scattered «20) setules along entire shaft or few (4-6) setules confined to proximal half of shaft; hooked serrate seta (Fig. 21)- longest and distalmost setae on dactylus of pereopod 5 of the megalopa; serrate 104 BULLETIN OF MARINE SCIENCE, VOL. 42, NO.1, 1988 A B c o E F G ;-- H K Figure 2. Types of setae identified from Arenaeus cribrarius. A, Simple; B, Aesthetasc; C, Plumose; D, Sparsely plumose; E, Plumodenticulate; F, Cuspidate; G, Multidenticulate; H, Serrate; I, Hooked serrate; J, Modified hooked serrate; K, Heavy toothed serrate.