Captive breeding and larval development of the scyllarine lobster Petrarctus rugosus

New Zealand Journal of Marine and Freshwater Research ISSN: 002-330 (Print) 1175-05 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzm20 Captive breeding and larval development of the scyllarine lobster Petrarctus rugosus T.S. Kumar, M. Vijayakumaran, T. Senthil Murugan, Dilip Kumar Jha, G. Sreeraj & S. Muthukumar To cite this article: T.S. Kumar, M. Vijayakumaran, T. Senthil Murugan, Dilip Kumar Jha, G. Sreeraj & S. Muthukumar (2009) Captive breeding and larval development of the scyllarine lobster Petrarctus rugosus, New Zealand Journal of Marine and Freshwater Research, 43:1, 101-112, DOI: 10.100/00233090950995 To link to this article: https://doi.org/10.100/00233090950995 Published online: 19 Feb 2010. Submit your article to this journal Article views: 15 View related articles Citing articles: 2 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalinformation?journalcode=tnzm20 Download by: [46.3.206.45] Date: 21 November 2017, At: 07:15

New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43: 101-112 002-330/09/4301-0101 The Royal Society of New Zealand 2009 101 Captive breeding and larval development of the scyllarine lobster Petrarctus rugosus T.S. KUMAR M. VIJAYAKUMARAN T. SENTHIL MURUGAN DILIP KUMAR JHA G. SREERAJ S. MUTHUKUMAR National Institute of Ocean Technology Pallikaranai Chennai - 600100, India email: vijay@niot.res.in Abstract The scyllarinid lobster, Petrarctus rugosus was reared to the postlarval nisto in 51 days at 24.9-26.5 C between November 2003 and April 2004 in Chennai, India. The lobster had eight phyllosomal instars. The eighth instars died while moulting to nisto. Instar VI was attained in 34 days with an average intermoult period of 5.4 days, whereas the last two moults took 17 days to complete. The captive breeders mated and bred several times between November and April with peak spawning in February. Repetitive breeding was observed with the brooding period varying from 11 to 17 days. Mean fecundity was 17 004 eggs ± 11 46 (SD). Hatching percentage was between 0.00 and 7.44. Keywords phyllosoma instars; nisto; intermoult period; fecundity INTRODUCTION Scyllarid lobsters are a diverse group with a widespread distribution in shallow coastal areas (Mikami & Kuballa 2007). Scyllarinae, the smaller lobsters with carapace lengths below 33 mm, include 3 species belonging to 13 genera (Holthuis 2002), M07119; Online publication date 24 February 2009 Received 30 November 2007; accepted 16 July 200 nearly half the known scyllarids. Scyllarinid species are predominant among the scyllarid phyllosoma collected from coastal and near shelf waters (Sekiguchi et al. 2007). There are many similarities between phyllosoma of scyllarids and closely related palinurid lobsters (see Baisre 1994), but the absence of a setose exopod in the third maxillipid of scyllarids helps to distinguish them from palinurid phyllosoma (Sekiguchi et al. 2007). Among the palinurids, a setose exopod is absent only in Jasus sp. (Baisre 1994) and in early stages of Sagmariasus verreauxi (Kittaka et al. 1997). During mid and late stages, the dorsoventrally compressed second antenna with a lateral process distinguishes scyllarid phyllosoma from those of palinurids, which have cylindrical and unbranched antennae (Sekiguchi et al. 2007). Though there are many descriptions of scyllarid larval morphology, few detail all stages (Sekiguchi et al. 2007). Many scyllarid larvae collected from the wild are yet to be identified beyond genus owing to insufficient identification keys (see Pessani & Mura 2007). One way to provide a reliable identification key is to rear lobsters through the different life stages and record morphological features of the larvae. The larval rearing period in scyllarids varies from 2 days in Thenus orientalis and T. indicus to more than 197 days in Scyllarides haani (see review in Mikami & Kuballa 2007; Sekiguchi et al. 2007). The embryos hatch as an advance-stage phyllosoma in T. orientalis and T. indicus, which passes through four instars before metamorphosing to the postlarval (nisto) phase, whereas the larvae of S. haani pass through eight stages (16 instars) without the final gilled stage (Mikami & Kuballa 2007). The larval phase of scyllarids is only complete with metamorphosis to the postlarval nisto, which settles into its benthic habitat (Mikami & Kuballa 2007). The duration of the nisto varies from 1 to 4 weeks and little is known of its biology (Mikami & Kuballa 2007). The non-feeding nisto relies on the energy reserves accumulated during the phyllosoma stages (Mikami & Kuballa 2007). Only few scyllarids have been reared to nisto stage in indoor culture systems. Takahashi & Saisho (197) grew

102 New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43 phyllosoma of Ibacus ciliatus and I. novemdentatus to the nisto stage, whereas Marinovic et al. (1994) achieved complete development of I. peroni. Mikami & Greenwood (1997) were successful in rearing the complete life cycle of T. orientalis and Thenus sp. Among scyllarinids, Robertson (196) reported the first successful completion of the life cycle of Scyllarus americanus, whereas other authors described early larval stages of few other laboratory-reared scyllarinids such as S. acquinoctialis (Robertson 1969), Sc. sordidus (Prasad & Tampi 1960; Sankoli &Shenoy 1973), and Petrarctus demani (Ritz 1977). Robertson (1979) further succeeded in rearing Sc. planorbis to the eighth and last instar, whereas Ito & Lucas (1990) completed the larval development of P. demani through eight instars to the nisto. This study was undertaken after a chance collection of large numbers of the scyllarinid, P. rugosus H. Milne Edwards 137 in an exploratory survey in 2003 off Chennai, India. Even though the type specimen of P. rugosus described by Holthuis (2002) was collected from the Pondicherry coast, near Chennai, no further occurrence of this species was reported from Chennai. Petrarctus rugosus started appearing occasionally in trawl catches from 40-60 m depth from 2004 onwards (M. Vijayakumaran pers. obs.). The main aim of the present study was to complete the life cycle of this species and describe the morphological features of larvae. No berried (eggbearing) specimen was obtained in the collection, but spawning occurred during captive breeding. As there are no published studies on reproduction of any scyllarinids, some reproductive data are presented with the larval descriptions. MATERIALS AND METHODS Petrarctus rugosus, collected from 20 m depth off Chennai, India (12 49.60 N, 0 7.63 E to 12 50.20 N, 0 17.50 E) by trawling in October 2003 were grown at the Sea Front Laboratory of the National Institute of Ocean Technology, Chennai, India. Identification of the species was confirmed following the key by Holthuis (2002). Adult P. rugosus, 9 females and 5 males, were stocked in a1m 3 fibre-reinforced plastic (FRP) tank with a sand bed covering 50% of its bottom. Lobsters were fed meat of live marine clam (Donax cuneatus) and green mussel (Perna viridis) at a rate of 5% body weight in the evening and unconsumed feed was removed by bottom siphoning before water exchange the subsequent morning. Continuous aeration was provided to keep dissolved oxygen concentrations above 4 mg/litre. All lobsters were coded individually, after measuring carapace length (± 0.01 mm), total length (± 0.01 mm) and weight (± 0.01g), with polyvinyl numbers on the carapace and the number code was replaced after moulting. Water quality parameters were recorded every day before water exchange. Salinity of sea water in the broodstock and phyllosoma rearing tanks was between 26.1 and 33.0 PSU, while temperature and ph ranged from 24.9 to 2.1 C and.2 to.5, respectively. Dissolved oxygen concentrations were between 4.0 and 5. mg/litre. Lobsters were examined at weekly intervals initially and every 3 days after first spawning. Lobsters bearing eggs were weighed and transferred to 700-litre circular FRP tanks for hatching. Mating usually occurred at night followed by spawning with no sperm mass remaining in the sternum. The gestation period was calculated from the day of spawning to larval release. The number of eggs per brood was determined by weighing (± 0.1 mg) and counting three samples, with a minimum of 100 eggs in each sample. Immediately after the release of phyllosoma, the breeder was weighed (± 0.01 g) to determine total egg weight for the fecundity calculation. Egg dimensions were measured (± 0.001 mm) using a stereo zoom microscope (Nikon SMZ 00 microscope with Nikon Coolpix 4500 camera). Healthy and actively swimming phyllosoma were removed from the hatching tank and reared in a flow-through rearing system. Phyllosoma rearing Eight light green rectangular plastic trays (30 cm 25 cm 10 cm) were used to rear phyllosoma. Eight to twenty phyllosoma were added to each tray and six trials were conducted. The trays were arranged on a table with a glass top with movable fluorescent light underneath. The phyllosoma were grown in the natural light/dark environment and the fluorescent light was used only during removal of unconsumed feed, debris, moults and dead phyllosoma. Chlorinated and UV-sterilised sea water from an overhead tank was fed into the trays at a steady flow rate to achieve a complete water exchange twice a day. Freshly hatched Artemia nauplii (mean ± SD: 41.6 ± 1.2 µm length, 176.9 ± 0.6 µm width) were the only feed provided (6 nauplii/ml) and fed overnight to the first three phyllosoma instars. Detachable 100 µm mesh strainers were fitted to the outlets of the trays to prevent escape of freshly hatched

Kumar et al. Larval development of the scyllarine lobster Petrarctus rugosus 103 Artemia nauplii. Unconsumed Artemia nauplii were removed every morning by increasing the flow rate and using bigger mesh strainers (400 µm). A combination of feeds was used from the fourth instar onwards. Artemia nauplii were fed overnight and removed the following morning after which frozen Cyclop-eeze (Argent Laboratories, Unites States) and shrimp postlarval pellets (C.P. Foods, Thailand) were added for 2-3 h. After removing these feeds, meat of live marine clam (D. cuneatus) or green mussel (P. viridis) or ovary of green mussel (5-6 pieces per phyllosoma) was added for another 2-3 h. Freshly hatched Artemia nauplii were added again in the evening after removing all uneaten food. The trays were cleaned once every week. Moultings were recorded by daily observation of exuvia as well as the size of the phyllosoma. The same instar phyllosoma were grouped together after each moult. The phyllosoma were measured (total length, carapace length, carapace width, abdomen length, and thorax width; ± 0.01 mm) and photographed as they entered a new instar using a stereo zoom microscope (Nikon SMZ 00 microscope with Nikon Coolpix 4500 camera). They were preserved in 4% buffered formalin for further examination. RESULTS Spawning was first recorded in November 2003 and continued until April 2004. The lobsters spawned three times in November, December and March, twice in January, and once in April. Peak spawning was in February, when seven of the nine females spawned. Newly spawned eggs were yellow-orange and turned dark orange before hatching. Repetitive breeding was observed, with three of the nine females spawning three times and one twice. Up to two spawnings were recorded within one moult cycle. Average carapace length and weight (± SD) of the spawners were 20.27 ± 0.95 mm and 6.0 ± 1.49 g (n = 9), respectively. Number of eggs in a single brood varied from 2747 to 22 619 and mean fecundity was 17 004 ±11 46 eggs (range: 4117-39 51 eggs). The brooding period varied from 11 to 17 days and the hatching percentage was between 0.00 and 7.44, with a release of 4254 ± 2923 phyllosoma (range: 1200-9600). Egg diameter and individual weight varied with developmental stage with an average of 0.46 ± 0.02 mm and 0.047 ± 0.014 mg, respectively. Lobsters shed all eggs three times during the period of observation. Phyllosoma development Of six trials conducted to rear phyllosoma, instar V was attained in three trials and the nisto stage in one. The last two instar VIII phyllosoma died while moulting to the postlarval nisto. One instar VIII phyllosoma almost completed moulting, whereas the other died in the early stage of moulting. The exuvium of the first larva was removed by using forceps and a needle, but the carapace was damaged in the process with the appendages distorted and broken. Hence, only the abdominal portion of the nisto was intact. The first moult was observed on the fifth day (Table 1). Survival was 100% (initial stocking to 40 larvae) up to instar HL 50% up to instar IV, 25% up to instar VI and 17% up to instar VIII. Description of phyllosoma instars of P. rugosus. The total length (TL) of instar I (Fig. 1) was 1.4 mm (1.40-1.51 mm) (Table 2). The eyestalk was unsegmented and the width of cephalic shield was 1.2 times its length and 1.2 times the thorax width. The abdomen length was 1/ 7 of the TL. The antennule was uniramous and unsegmented with three long terminal setae, a short spine at the inner distal angle and a short spine in the mid lateral portion. The antenna was uniramous and extended up to ¼ of the length of the antennule. The antenna terminated in a spine with two sub-terminal setae. Maxilliped 3 had five segments and a coxal spine. Coxal spines and sub-exopodal spines were present in pereiopods 1-3. Pereiopods 1 and 2 had well developed exopods with seven pairs of setae (Table 3). Pereiopod 3 did not have setae on the exopod and pereiopod 4 appeared as a bud. The abdomen width was almost equal at the proximal and distal ends and included posteriorlateral spines with four basal setae. Table 1 Cumulative intermoult period (days ± SD) of the phyllosoma instars of Petrarctus rugosus. Instars I-II n-m I-IV IV-V V-VI VI-VII VII-VI VIII-Nisto Cumulative intermoult period (days) Range n Mean ± SD 5-9-10 15-16 21-23 2-29 34-3 42-44 51 4 3 3 2 2 5.25 ± 0.6 9.50 ± 0.53 15.0 ± 0.75 21.66 ±1.15 31.33 ±0.5 35.33 ± 2.30 43.00 ±1.41 51.00 ±0.00

New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43 Fig. 1 Phyllosoma instar I of Fig. 2 Phyllosoma instar II of Table 2 Body dimensions (mm ± SD) of phyllosoma instars of Petrarctus rugosus. (TL, total body length; CL, carapace length; CW, carapace width; AL, abdomen length.) Parameters I (n = ) II (n = ) m (n = ) Phyllosoma instars rv V (n = 4) (n = 3) VI (n = 3) vn (n = 2) vm (n = 2) TL CL CW AL CW/CL AL/TL 1.4 ±0.03 0.6 ±0.02 1.03 ±0.05 0.19 ±0.01 1.20 0.14 1.94 ±0.06 1.06 ±0.04 1.35 ±0.04 0.23 ± 0.01 1.27 0.12 2.91 ± 0.02 1.94 ±0.03 2.23 ± 0.03 0.30 ± 0.02 1.15 0.10 3.25 ± 0.03 2.2 ± 0.05 2.43 ± 0.02 0.37 ± 0.01 1.07 0.09 3.67 ± 0.04 2.5 ± 0.07 2.67 ± 0.05 0.47 ± 0.01 1.03 0.13 4.74 ±0.16 2. ±0.03 3.61 ±0.05 0.67 ±0.0 1.25 0.14 6.03 ±0.13 4.09 ±0.14 4.53 ±0.11 1.19 ±0.01 1.11 0.20 9.96 ±1.20 5.19 ±0.0 5.59 ± 0.05 3.00 ±0.71 1.0 0.30

Kumar et al. Larval development of the scyllarine lobster Petrarctus rugosus 105 Fig. 3 Phyllosoma instar III of Table 3 Instar I n m IV V VI vn vni Number of setae on the exopods of pereiopods in phyllosoma instars of Petrarctus rugosus. P1 7 9 10 10-11 11-12 13-14 16 P2 7 9 10 11 12 13-14 16 P3 Exopod bud Elongated bud 6 9 12-13 14 No. of setae P4 Pereiopod bud Elongated pereiopod bud Exopod bud appears Elongated exopod bud Elongated exopod bud 6 9-10 12 The TL of instar H (Fig. 2) was 1.94 mm (1.6-2.02 mm) (Table 2). The eyestalk became segmented in this instar. The width of the cephalic shield was 1.27 times its length and 1.5 times the thorax width. The abdomen length was 1/ of the TL. The antennule had three long and one small terminal setae and a spine on inner side at the distal end. A pair of subterminal sensory setae was present and the inner ramous appeared as a short protuberance at the base of the mid lateral spine. The antenna was about 1/ 3 the length of the antennule, terminated with a spine, and had two sub-terminal setae. Pereiopods 1 and 2 had well developed exopods bearing eight pairs of setae, whereas the exopod of pereiopod 3 was elongated but without setae (Table 3). Pereiopod 4 was longer than the abdomen and not segmented. The coxal spine with an accessory seta was present P5 0 0 Pereiopod bud Elongated Pereiopod bud Pereiopod bud with two segments Pereiopod, longer than the abdomen, with four segments Pereiopod with five segments Pereiopod extends well beyond the abdomen. Gill buds present in maxilliped 3 and pereiopods 1 to 4 in maxilliped 3 and pereiopods 1, 2, and 3. The abdomen width was almost equal at proximal and distal ends and included posterior-lateral spines with four basal setae. The TL of instar m (Fig. 3) was 2.91 mm (2.90-2.94 mm) (Table 2). The cephalic shield was 1.15 times wider than its length and 1.93 times wider than the thorax. The length of the abdomen was 1/ 10 of the TL. The antennule became biramous with two segments and the shorter arm had three terminal setae. The long arm had three long terminal setae, one slender seta on the outer distal angle and a spine at the inner distal angle. The long arm had two pairs of sub-terminal setae along the inner side. The antenna was 1/ 3 the length of the antennule. The exopods of pereiopods 1 and 2 had nine pairs of setae. The exopod of pereiopod 3 became segmented

New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43 Fig. 4 Phyllosoma instar IV of Fig. 5 Phyllosoma instar V of with six pairs of setae. Pereiopod 4 was elongated and four-segmented with the exopod appearing as a short bud (Table 3). Pereiopod 5 was present as a short bud. The abdomen was slightly broader at the base. The uropod appeared as a rudimentary bud on each side of the abdomen. The TL of instar IV (Fig. 4) was 3.25 mm (3.20-3.2 mm) (Table 2). The cephalic shield was about 1.07 times wider than long and 1.97 times wider than the thorax. The abdomen length was Vu of the TL. The antennular peduncle had two segments and the outer ramus was divided from the antennular peduncle. It had four long terminal setae, a slender seta, a spine at the outer distal angle and two additional groups of sub-terminal sensory setae. The inner ramus had two spines. The antenna was biramous and extended up to 1/ 3 the length of the antennule with the inner lobe terminating on a spine with two setae and a triangular outer lobe. The exopods of pereiopods 1 and 2 had 10 pairs of setae and pereiopod 3 had eight pairs of setae in its exopod (Table 3). The exopod bud of pereiopod 4 was elongated. Pereiopod 5 was elongated extending up to ¾ of the abdomen along its lateral margin. The

Kumar et al. Larval development of the scyllarine lobster Petrarctus rugosus 107 Fig. 6 Phyllosoma instar VI of B Fig. 7 Phyllosoma instar VII of telson was differentiated with a straight posterior margin and had four posterior-lateral spines. The TL of instar V (Fig. 5) was 3.67 mm (3.60-3.71 mm) (Table 2). The width of the cephalic shield was almost equal (1.03 times) to its length and 1.71 times the thorax width. The abdomen length was / of the TL. The antennular peduncle was longer with two segments and with the outer ramus having six groups of sensory setae. The inner ramus was about half the length of the outer ramus. The outer lobe of the antenna was slightly larger than in the previous instar, the distal end of inner lobe was pointed with a spine, and three sub-terminal setae. The exopod of pereiopod 1 had 10-11 pairs of setae and pereiopod 2 had 11 pairs of setae on its exopod (Table 3). The exopod of pereiopod 3 had eight pairs of setae, whereas pereiopod 4 was elongated without setae. Pereiopod 5 was two-segmented and extended beyond the abdomen. The uropod was biramous and the telson was differentiated with a straight posterior margin bearing posterio-lateral spines. The TL of instar VI (Fig. 6) was 4.74 mm (4.66-4.0 mm) (Table 2). The cephalic shield was 1.25 times wider than long and 1.7 times wider than the thorax. The abdomen length was 1/ of the TL. The antennular peduncle had two segments with the outer ramus bearing eight pairs of sensory setae. The inner ramus was about 2 / 3 the length of the outer ramus which had three spines and five rows of long lateral setae. The outer lobe of the antenna was elongated

10 New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43 Fig. Phyllosoma instar VIII of and the inner lobe had three spines on its lateral margin. The exopod of pereiopod 1 had 11-12 pairs of setae and pereiopod 2 had 12 pairs of setae on its exopod. Pereiopod 3 had nine pairs of setae on the exopod. The exopod of pereiopod 4 was setose with six pairs of setae (Table 3). Pereiopod 5 was segmented and longer than the abdomen. The coxal spine had an accessory seta present in maxilliped 3 and pereiopods 1-4. The first sign of segmentation appeared on the abdomen as four pairs of uniramous pleopod buds. The uropod was expanded with both rami reaching slightly beyond the rounded posterior margin of the telson. The TL of instar VII (Fig. 7) was 6.03 mm (5.94-6.12 mm) (Table 2). The cephalic shield was 1.11 times wider than its length and 1.49 times wider than the thorax. The abdomen was more elongated and formed 1/ 5 of the TL. The antennular peduncle was in three segments. The inner ramus was almost equal in length to the outer ramus and terminated in three spines and setae. Nine pairs of sensory setae were present on the outer ramus. The antenna was broader than in the previous instar and extended with small spines. Its outer lobe was more elongated. The exopod of pereiopods 1 and 2 had 13-14 pairs of setae. Pereiopod 3 had 12-13 pairs of setae and pereiopod 4 had 9-10 pairs of setae on the exopods (Table 3). Pereiopod 5 was more elongated and had five segments. The coxal spine with accessory seta was present in pereiopod 5. Four pairs of bifurcated pleopods were present in the abdomen. The uropod was fully developed with five flaps. The TL of instar VIII (Fig. ) was 9.96 mm (9.11-10. mm) (Table 2). The cephalic shield was 1.0 times wider than long and 1.36 times wider than the thorax. The abdomen was more elongated and formed almost 1/ 3 of the TL. The antennular peduncle had six pairs of setae laterally. The outer ramus had nine or more groups of sensory setae. The antenna was broader and segmented with the outer lobe expanded. The inner margin of the inner lobe contained spines. The exopods of pereiopods 1, 2, 3, and 4 had 16, 16, 14, and 12 pairs of setae, respectively (Table 3). The long, pereiopod 5 had five segments reaching well beyond the posterior margin of the telson. Gill buds were present on maxilliped 3 and pereiopods 1-4. The abdomen had biramous and elongated pleopods whose inner rami were slightly longer than the outer ones. The uropod was well developed beyond the posterior margin of the telson. As the carapace of the nisto was damaged when the exuvium of instar VIII was removed, only the abdomen could be examined in detail. The abdominal somites 1-5 had prominent mid dorsal carinae. The pleural and the posterio-lateral margins of abdominal somites 1-5 were serrated. The posterior margin of abdominal somite 6 had sharp spines in the middle and on the lateral margins. Pleopods 1-4 were biramous and setose. DISCUSSION Oceanic species of scyllarids with high natural mortality of larvae tend to produce a large number of small eggs that hatch at an early stage of development with an extended larval period allowing

Kumar et al. Larval development of the scyllarine lobster Petrarctus rugosus 109 wide dispersal (see Webber & Booth 2007; Sekiguchi et al. 2007). In contrast, coastal species produce fewer and larger eggs and have a shorter larval life (Stewart & Kennelly 1997; DeMarteni & Williams 2001 ; Booth et al. 2005; Sekiguchi et al. 2007). Many smaller scyllarids species have a considerably shorter inshore development, whereas other, mostly larger, species have greater offshore dispersal (Booth et al. 2005). Petrarctus rugosus, caught from 20-60 m depth had the smallest reported egg size among scyllarids (0.46 mm diam. and 0.047 mg weight) and had a higher fecundity (average of 17 004 eggs with a maximum of 39 51 eggs). Fecundity may be higher as captive breeders produce fewer eggs than those in the wild (Vijayakumaran et al. 2005). Tropical spiny lobsters breed throughout the year, both in the wild and in captivity (Vijayakumaran et al. 2005), whereas scyllarids including P. rugosus have a shorter breeding season of 5-6 months, from November to April (Mikami & Kaballa 2007; present study). Like palinurids, P. rugosus also bred repetitively and the average spawning in captive breeders was 1.5 times per year compared with four times per year for palinurid lobsters such as Panulirus homarus and Pa. ornatus (Vijayakumaran et al. 2005; Senthil et. al. 2005). Hatching percentage and the number of phyllosoma released in P. rugosus showed wide variation. Similar observations of hatching percentage were made in captive breeders of Pa. homarus (0 to 93%) and Pa. ornatus (0.0 to 5.7%) also (Vijayakumaran et al. 2004; Vijayakumaran et al. 2005; Senthil et al. 2005). Larval development Booth et al. (2005) and Mikami & Kuballa (2007) have tabulated available literature on scyllarid reproductive and larval parameters including female size, number of instars and stages, and length of larval life. In Scyllarinae, adult females are small (<30 mm carapace length) (Booth et al. 2005). The phyllosoma have at least 6-12 instars with a larval development duration of 1-4 months (see Booth et al. 2005; Sekiguchi et al. 2007). The size of the final phyllosoma of scyllarinids ranges from c. 10-30 mm total length (Mikami & Kuballa 2007). Twelve stages have been assigned to P. rugosus phyllosoma from wild collections (see Mikami & Kuballa 2007), whereas only eight instars and a postlarval nisto were recorded in this study. Similarly, only instars and a nisto are described for other hatchery-reared scyllarinids such as P. (previously Scyllarus) demani (Ito & Lucas 1990) and Sc. planorbis (Robertson 1979). The larval development of P. rugosus was completed in 51 days at 24.9 to 2.1 C. The larval development period reported for other scyllarinids is 42-53 days for P. demani (Ito & Lucas 1990), 54 days at 25 C for Sc. planorbis (Robertson 1979) and 32-40 days for Sc. americanus (Robertson 196). Sankoli & Shenoy (1973) obtained instar VI in Sc. sordidus in 30 days at 26-2 C. Unlike the palinurid, Pa. homarus, which has substages within an instar (Radhakrishnan & Vijayakumaran 1995), each moult produced the next instar in P. rugosus. Instar VII of P. rugosus was attained in 34 days, with an average of 5.7 days per instar and the next two moults took 17 days to complete. Freshly-hatched Artemia nauplii, the main feed available to P. rugosus 17 h a day, were too small for the bigger phyllosoma, which had to spent more energy to capture sufficient numbers to fulfill their feed requirements. Vijayakumaran & Radhakrishnan (196) made similar observations in Pa. homarus phyllosoma and in other species of scyllarids; Artemia nauplii alone were also insufficient to complete the larval cycle (Mikami & Kuballa 2007). Petrarctus rugosus were able to consume large particles of feed such as clam/mussel meat but these feeds were given only for 5-6 h a day. Hence, inadequate feeding may have been the reason for the delay in moulting in the last two instars. Appropriate feeding strategies could considerably reduce the larval phase of lobsters as evidenced in Pa. elephas fed with live marine fish larvae (Kittaka 2000). Comparison of larval instars of scyllarinids Studies on larval distribution and recruitment mechanisms of scyllarids have been mainly based on palinurid recruitment (Booth et al. 2005). Most of the earlier reports of scyllarid phyllosoma were from plankton collections that often provided incorrect and unresolved identification (see Booth et al. 2005), which has been remedied for many scyllarids through larval culture experiments (Sekiguchi et al. 2007). Whereas many bigger scyllarids such as T. orientalis, Thenus sp., I. ciliatus, I. novemendatus, I. peroni, whose life histories have been completed, attracted attention owing to their commercial potential for aquaculture, only few smaller scyllarinids (P. demani, Ito & Lucas 1990; Sc. planorbis, Robertson 1979, and P. rugosus, present study) have been reared through their life cycle in hatcheries. Sankoli & Shenoy (1973) described Sc. sordidus phyllosoma up to instar VI and Tampi & George (1975) described some stages of P. rugosus phyllosoma from plankton

110 New Zealand Journal of Marine and Freshwater Research, 2009, Vol. 43 collections. These phyllosoma were compared to identify distinguishing characters of each one. The phyllosoma instar I of P. rugosus was similar in size to that of P. demani. The setae in pereiopods 1 and 2 are fewer in Sc. planorbis and almost the same in the other three species. The pereiopod 4 bud is present only in P. rugosus and in P. demani (almost as long as the abdomen). Only P. demani phyllosoma has a pair of setae in the exopod of pereiopod 3. The antennule has three long apical setae and a small one in P. rugosus, whereas only three apical setae were described in the other three species. The instar H of P. rugosus is bigger than that of Sc. sordidus and Sc. planorbis, but slightly smaller than that of P. demani. The exopod of pereiopod 3 is setose only in P. demani (4 pairs). The pereiopod 4 bud is unsegmented in P. rugosus and three- or more segmented with an exopod bud in P. demani. The pereiopod 5 bud is present in P. rugosus and P. demani. The antenna has four long apical setae, one small seta and a short spine on the inner side in P. rugosus and P. demani, whereas instar H of Sc. sordidus has no spine. The instar III of P. rugosus is bigger than those of Sc. sordidus and Sc. planorbis, but smaller than that of P. demani. The antennular peduncle is twosegmented in P. rugosus and P. demani. The exopod of pereiopod 3 has 6 pairs of setae in P. rugosus and Sc. sordidus, 7 to pairs in P. demani, and 3 to 5 pairs in Sc. planorbis. The exopod of pereiopod 4 is short in S. sordidus and elongated in the other three species. The size of the reared instar m of P. rugosus is comparable to instar III of S. sordidus collected from plankton by Tampi & George (1975), but the pereiopod 5 bud was present in the reared phyllosoma. The size of instar IV is bigger in P. demani than in the other three species which are similar in size. The exopod of pereiopod 4 is setose only in P. demani. The antennal peduncle is clearly separated from the outer ramus in P. rugosus and P. demani and not so in the other two species. The antenna is bifurcated in all species but Sc. sordidus. Petrarctus rugosus has fewer setae in the exopod of pereiopod 3. The pleopod buds are present only in P. demani. The instar V is similar in size in P. rugosus and Sc. sordidus, but markedly bigger in P. demani. The antennal peduncle is three-segmented in P. demani and two-segmented in the other three species. Pereiopod 5 has a coxal segment and is as long as the abdomen in P. rugosus and P. demani, 3 / 4 of the abdomen length in Sc. planorbis and a small unsegmented bud in Sc. sordidus. The exopod of pereiopod 4 is not setose in P. rugosus. Instar VI of P. demani is bigger than that of the other three species, which are almost equal in size. The exopod of pereiopod 4 is setose in P. rugosus and Sc. sordidus, with the least number of setae (6 pairs) in P. rugosus. The pereiopod 5 bud is threesegmented in P. demani and Sc. planorbis and twosegmented in P. rugosus and unsegmented in Sc. sordidus. Four pairs of pleopod buds were present in all species. The uropod extended beyond the distal margin of the telson in P. rugosus and P. demani. The size of instar VII was bigger in P. demani than in the other three species. The antennular peduncle is three-segmented in all species. The pleopods are bifurcated and the abdomen is elongated and formed / 5 of the TL in P. rugosus. The cephalic shield is longer in P. rugosus than in the other three species. Instar VU! was the largest in P. demani followed by that of P. rugosus and Sc. planorbis. Whereas the TL of instar VIII of P. rugosus in this study was only 9.1-10. mm, those collected from the wild had a size range of 15-19 mm (Berry 1974; Prasad et al. 1975). In this instar, the abdomen is more elongated forming almost / 3 of the TL. The gill buds appear in maxilliped 3 and pereiopods 1 to 4 in all three species. The postlarval nisto is an important phase in the life cycle of scyllarids as it provides the link between planktonic and benthic phases similar to the puerulus in palinurids (see Booth et al. 2005). Only the abdominal portion of the nisto could be described for P. rugosus, which resembled that of P. demani (Ito & Lucas 1990). However, the mid dorsal carinae in abdominal somite 3 were not as prominent in P. rugosus compared with those in P. demani. Similarly, the serration in the pleural margin of abdominal somites 2 to 5 was not as pointed as those in P. demani. Scyllarinids, the small lobsters, do not form a prominent fishery in any part of the world, but they form an important link in the benthic and pelagic biodiversity in nearshore waters (Booth et al. 2005; Sekiguchi et al. 2007). More effort is needed to describe the complete life cycle of scyllarinid species, to allow identification of the phyllosoma, which are predominant in plankton collections in near shore waters. ACKNOWLEDGMENTS We thank T. Subramoniam, Fellow, Indian National Science Academy, NIOT, Chennai, R. Kirubagaran (Scientist) and G. Dharani (Scientist) Ocean Science and Technology for Islands (OSTI), NIOT, Chennai for critically reviewing the manuscript.

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