Nine stages and substages of post-, inter- and premoult were distinguished in the West Coast rock lobster Jasus lalandii by microscopic examination of the cuticle, epidermal retraction and setal development in the pleopods.The postmoult condition is characterized by progressive thickening of the setal walls and cuticle through to intermoult. Premoult commences with apolysis (Stage D0), followed by setal development (Stage D1’, D1”, D1’”)and culminates with cuticle deposition (Stage D2). The diagnostic features of the stages are generally similar to those of other decapod crustaceans

Cockcroft, AC

De Villiers, CJ

Gibbons, MJ

Isaacs, G

English

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Most decapods spend their lives in a continuouscycle of moult-related events (Aiken 1980). Based onintegumental changes, Drach (1939 as cited by Chanet al. 1988) first divided the crustacean moult cycleinto four phases: metecdysis (subdivided into StagesA and B), the period immediately following ecdysis;anecdysis (Stage C), a period of tissue growth andaccumulation of food reserves; proecdysis (Stage D),a period of active morphological and physiologicalchange in preparation for the next moult; and ecdysis(Stage E), the shedding of the old cuticle.Macroscopic changes in exoskeletal condition(shell state) or colour have been used to “stage” themoult cycle of lobsters (Heydorn 1969, Silberbauer1971, Aiken 1980). The “hardness” or “softness” of thecarapace usually enables classification into broadcategories (e.g. “soft new” defines a newly moultedstage and “hard old” an intermoult stage), but thegrouping does not allow for exact identification ofthe moult stage. These macroscopic changes alsolack the resolution needed to identify the transitionfrom intermoult to premoult, a key point within themoult cycle (Aiken 1980).Because of differences in the onset and rate ofcompletion of different premoult events, reliability canonly be achieved by basing subdivisions on changes ina single developing system (Aiken 1980). The systemthat has proved to be the most convenient and reliableis the state of setal development, and changes associatedwith this have been used for moult staging in variouscrustacean species (Aiken 1973, Peebles 1977, VanHerp and Bellon-Humbert 1978, Lyle and MacDonald1983, Chan et al. 1988). This method uses internalchanges in the morphology of the developing setae ofsuch appendages as pleopods, together with exoskeletalchanges in order to assess moult stage (Lyle andMacDonald 1983). The general details of setal develop-ment are similar for a variety of crustaceans (Turnbull1989).Jasus lalandii is distributed from about 23°S, justnorth of Walvis Bay in Namibia, to about 28°S, nearEast London on the east coast of South Africa. Com-mercial densities are restricted to the area between25°S (southern Namibia) and Cape Point in SouthAfrica (Pollock 1986). The South African fishery ismanaged mainly by means of Total Allowable Catch(TAC), size limits, closed seasons and specified fishingareas. A coastwide decrease in the somatic growthrate of J. lalandii over the past decade (Cockcroftand Goosen 1995) has been part of the reason for decreased catches and ultimately a decrease in theTAC for the species. Subsequent studies on aspects oflobster growth identified the lack of detailed infor-mation on moult stages as a major drawback in theinterpretation of field and laboratory data (Cockcroft1997). An accurate reassessment of the moult stageswould allow: (1) detailed comparison of the moult cycles between various areas; (2) more accurate inter-pretation of commercial catch data on an area andmonthly basis; (3) better interpretation of behaviourand physiology (both laboratory and in the field), in-cluding biochemical changes during the moult cycle;and (4) comparison with the currently used moult-staging method, using exoskeletal condition. The aim of this study is to detail the stages in themoult cycle of Jasus lalandii, using epidermal retractionand the degree of setal development in the pleopodsas the basis for determination. S. Afr. J. mar. Sci. 22: 177–1832000 177DETERMINATION OF MOULT STAGE IN THE SOUTH AFRICAN WEST COAST ROCK LOBSTER JASUS LALANDII (H. MILNE EDWARDS)(CRUSTACEA: DECAPODA)G. ISAACS*, A. C. COCKCROFT†, M. J. GIBBONS* and C. J. DE VILLIERS*Nine stages and substages of post-, inter- and premoult were distinguished in the West Coast rock lobster Jasuslalandii by microscopic examination of the cuticle, epidermal retraction and setal development in the pleopods.The postmoult condition is characterized by progressive thickening of the setal walls and cuticle through to inter-moult. Premoult commences with apolysis (Stage D0), followed by setal development (Stage D1’, D1”, D1’”)and culminates with cuticle deposition (Stage D2). The diagnostic features of the stages are generally similar tothose of other decapod crustaceans.* Zoology Department, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa† Marine & Coastal Management, Private Bag X2, Rogge Bay 8012, South Africa. E-mail: cockcrof@sfri.wcape.gov.zaManuscript received September 1999; accepted April 2000178 South African Journal of Marine Science 22 2000(a)(b)(c)Fig. 1: Post- and intermoult stages of Jasus lalandii – (a) Stage A, with thin setal walls (sw), poorly defined setalbases (sb) and wide, grainy setal lumen (sl); (b) Stage B, with thicker setal walls, well defined setalbases, narrower, less grainy setal lumen and thin cuticle; (c); Stage C, with thick setal walls, narrow setallumen and thick cuticle. Scale bar = 100µmMATERIAL AND METHODSJuvenile lobsters were collected monthly usingSCUBA at Green Point and from the Cape TownHarbour Wall during the period February 1996 –February 1997. The exoskeletal condition (shellstate) was determined using the method of Heydorn(1969), and individuals considered to be in premoultor in intermoult (20–45 mm carapace length, CL) wereretained for further observation.The lobsters were kept in aquaria supplied withrunning seawater at a temperature of 12–14°C, tem-peratures broadly similar to those experienced bylobsters along the west coast of South Africa. Thelobsters in intermoult were fed three times a week ona diet of fish and various invertebrates. Pre-moultlobsters did not require feeding (Silberbauer 1971,Pollock 1973). Pleopods from animals in premoultwere removed on alternate days to determine changesin premoult stage, whereas those of postmoult indivi-duals were removed daily, whenever possible. Lobstersin intermoult were sampled on an ad hoc basis, untilthey entered premoult.In all, 1 450 pleopods were cut at their base andfrozen for later examination. After thawing, the pleopodwas placed in an aquaculture slide in water and exam-ined at 63, 100 and 160× magnification using a ZeissIM35 inverted, phase-contrast photo-microscope. Thepleopods were photographed and then used to describethe various moult stages. Freezing and thawing ofpleopods did not influence the accuracy of staging(Lyle and MacDonald 1983).DESCRIPTION OF MOULT STAGESNine stages and substages, based on the developmentof setae and the degree of epidermal retraction in thepleopods, are described.PostmoultStage A (Fig. 1a) – The setal walls show little orno thickening and the internal walls appear wavy.The setal bases are not well defined compared tothose of Stage B. The setal lumen is wide and granular.The entire exoskeleton is extremely soft.Stage B (Fig. 1b) – The setal walls begin to thicken.The setal lumen is narrower and less grainy, and thesetal bases are well defined. The cuticle is relativelythin compared to Stage C. The exoskeleton starts toharden.IntermoultStage C can be divided into four substages, basedon shell rigidity (Aiken 1980), with the fourth stage(C4) usually referred to as the intermoult phase.Stage C4 (Fig. 1c) – The setal walls become thick.The setal lumen is narrow and sometimes nonexistentowing to the thick setal walls. The cuticle is thickand the epidermis lies close to it. The exoskeleton ishard throughout this stage.PremoultThe onset of premoult is often associated with achange in colour of the abdominal flesh from pink toa dark brown/black. However, the absence of acolour change does not necessarily mean that an in-dividual has not entered the premoult stage.Stage D0 (Fig. 2a) – This stage is characterized byapolysis, or the retraction of the epidermis from thecuticle of the pleopod, which results in a transparentgap between the two tissues. Retraction starts at theapical tip of the pleopod and continues laterally.Stage D1’ (Fig. 2b) – The tips of the new setae become visible in the zone of retraction, as flaccidwisps of tissue, which are small and irregular in appear-ance.Stage D1” (Fig. 2c) – This stage commences withthe invagination of the setae.Stage D1”’ (Fig. 2d) – Appearance of barbulesalong the setal axes. The proximal ends of the setaeare poorly defined. There is no epicuticle deposition.Stage D2 (Fig. 2e) – The proximal ends of thesetae appear bifurcate and deposition of the new epi-cuticle has begun.Stage D3 (Fig. 2f) – The new exoskeleton has fold-ings to accommodate subsequent growth. The proxi-mal ends appear blunt (but not clear in Fig. 2f).No further changes appeared to be visible in thepleopods until ecdysis/moult. A diagrammatic repre-sentation of moult Stages A–D3 is given in Figure 3.DISCUSSIONLyle and MacDonald (1983) grouped Stages A andB of postmoult together in Panulirus marginatus,whereas these stages were separate for Panulirus or-natus (Turnbull 1989) as well as for J. lalandii in thecurrent study. The key features of the postmoultstages are the thickening of the setal walls and thewide diameter of the setal lumen, which is filled witha granular protoplasm. The postmoult stages of J. la-Isaacs et al.: Moult Stages in Jasus lalandii2000 179180 South African Journal of Marine Science 22 2000(a)(b)(d)(e)(f)(c)Fig. 2:(a) Stage D0, showing epidermal retraction (er); (b) Stage D1’, with new setae (ns) visible in the retracted zone; (c) Stage D1”, showing invagination (i) ofthe new setae; (d) Stage D1”’, with  barbules (b) along the setal axes and poorly defined proximal ends (pe); (e) Stage D2, showing bifurcate (bi) proximalends of the setae and with new epicuticle deposition (ep); (f) Stage D3, showing folding (f) of new exoskeleton. Scale bar = 100µmlandii are characterized here by a progressive thickeningof the setal walls through to intermoult. Turnbull (1989)determined the same for P. ornatus, and he noted thatthe setal walls of individuals at Stage A were wavy andthat the setal lumen was filled with a granular proto-plasm. Van Herp and Bellon-Humbert (1978) describedthe setae in Astacus leptodactylus as being filled with afibrillar protoplasm during moult Stage A, and then bya homogenous protoplasm in Stage B. Mills and Lake(1975) attributed these changes in the setal lumen ofParastacoides tasmanicus to the development of aninternal matrix in the setae.The intermoult Stage C is characterized by thicksetal walls, and a narrow, and sometimes occluded,setal lumen. The cuticle is thick. Turnbull (1989) de-scribed setae in this stage as having narrow lumenthat had lost most of its grainy appearance, and alsonoted thick and smooth setal walls, and a thick cuticlethat extended to below the setal bases. It is not knownwhether the appearance of the setal lumen is a resultof a retraction of the cellular contents, but it appearsto involve a thickening of the setal walls (Lyle andMacDonald 1983). As for P. marginatus (Lyle andMacDonald 1983), Stage C in J. lalandii could not befurther subdivided on the basis of microscopic exami-nation of the pleopods.As reported for Homarus americanus (Aiken 1980)and Jasus edwardsii (R. Musgrove, South AustralianResearch and Development Institute [SARDI], pers.comm.), the absence of a blackened abdominal fleshcolour in J. lalandii does not necessarily indicate thatan individual is not in premoult. The premoultIsaacs et al.: Moult Stages in Jasus lalandii2000 181Fig. 3: Diagrammatic representation of moult Stages A–D3. Stages A–C show progressive thickening of thesetal walls (sw) and cuticular (c) thickening; Stage D0 shows epidermal retraction (er); and Stages D1’–D3show the various stages of setal development (new setae = ns, invagination = i, proximal end = pe, bifurcateend = bi, epicuticle = ep)condition in J. lalandii has been divided into StagesD0, D1, D2 and D3. The onset of premoult (Stage D0)in decapods is generally identified by the retractionof the epidermis from the exoskeleton (Kurup 1964,Aiken 1973, Mills and Lake 1975, Turnbull 1989), acondition known as apolysis (Jenkin and Hinton1966). There appears to be considerable epidermalretraction in J. lalandii before the appearance of thenew setae, indicating that the duration of this stage isrelatively long. P. ornatus also has a relatively longStage D0 (Turnbull 1989), and Aiken (1973) de-scribed this stage as having a broad transitionalphase between intermoult and premoult. However,this stage is very short in J. edwardsii (R. Musgrove,pers. comm.).Stage D1 can be divided into three substages in J. lalandii, as is generally the case for other lobsters.Substage D1’ is characterized by the appearance ofthe tips of the new setae in the retracted zone. Earlysetal development is a common feature in many otherdecapods (Kurup 1964, Stevenson et al. 1968, Aiken1973, Mills and Lake 1975, Van Herp and Bellon-Humbert 1978). Maximum epidermal retraction in P.marginatus is attained during D1’, and the formationof the new setae is assigned to substage D1”.Although substages D1’ and D1” in P. ornatus weregrouped by Turnbull (1989), because maximal epider-mal retraction and the appearance of new setae occurat approximately the same time, the substages are dis-tinct in J. lalandii.Progressive invagination of the new setae into theepidermis was characteristic of Stage D1” in J. lalandi,as in other decapods (Aiken 1973, Mills and Lake1975). However, this feature is sometimes obscure.For example, Lyle and MacDonald (1983) found thepleopods of P. marginatus to be heavily pigmentedand opaque, which made identification difficult.Stage D1’” is characterized by the formation ofbarbules on the new setae in J. lalandii, as in P. or-natus (Turnbull 1989), Astacus leptodactylus (VanHerp and Bellon-Humbert 1978) and Parastacoidestasmanicus (Mills and Lake 1975), as well as for somestomatopods (Reaka 1975). However, this feature isnot found in P. marginatus (Lyle and MacDonald1983) or Homarus americanus (Aiken 1973), barbulesonly becoming apparent in those species at Stage D2.The deposition of the new cuticle is indicative ofStage D2 in J. lalandi and the final stage that can beidentified before ecdysis is Stage D3. The blunting ofthe proximal ends of the setae in Stage D3 is a featurethat has been observed in H. americanus (Aiken1973), but it appears to be absent in J. edwardsii(R. Musgrove pers. comm.), in which bifurcation isstill present at Stage D3.ACKOWLEDGEMENTSWe thank Messrs M. Noffke and A. Hazell (Univer-sity of the Western Cape) for their assistance in thefield. Dr R. Musgrove (SARDI) is thanked for his assistance with staging methodology. The Universityof the Western Cape, the South African Network forCoastal and Oceanographic Research, and Marine &Coastal Management are acknowledged for financialand logistic support. LITERATURE CITEDAIKEN, D. E. 1973 — Proecdysis, setal development, and moltprediction in the American lobster (Homarus americanus).J. Fish. Res. Bd Can. 30: 1337–1344.AIKEN, D. E. 1980 — Molting and growth. In The Biology andManagement of Lobsters. 1. Physiology and Behavior.Cobb, J. S. and B. F. Phillips (Eds). New York; AcademicPress: 91–163.CHAN, S-M., RANKIN, S. M. and L. L. KEELEY 1988 —Characterization of the moult stages in Penaeus vannamei:setogenesis and hemolymph levels of total protein, ecdys-teroids, and glucose. Biol. Bull. mar. biol. Lab., WoodsHole 175: 185–192.COCKCROFT, A. C. 1997 — Biochemical composition as a growthpredictor in male West Coast rock lobster (Jasus lalandii).Mar. Freshwat. Res. 48: 845–856.COCKCROFT, A. C. and P. C. GOOSEN 1995 — Shrinkage atmoulting in the rock lobster Jasus lalandii and associatedchanges in reproductive parameters. S. Afr. J. mar. Sci. 16:195–203. HEYDORN, A. E. F. 1969 — The rock lobster of the SouthAfrican west coast Jasus lalandii (H. Milne-Edwards).2. Population studies, behaviour, reproduction, moulting,growth and migration. Investl Rep. Div. Sea Fish. S. Afr.71: 52 pp.JENKIN, P. M. and H. E. HINTON 1966 — Apolysis in arthropodmoulting cycles. Nature, Lond. 211: p. 871.KURUP, N. G. 1964 — The intermoult cycle of an anomuran,Petrolisthes cinctipes Randall (Crustacea – Decapoda).Biol. Bull. mar. biol. Lab., Woods Hole 127: 97–107.LYLE, W. G. and C. D. MACDONALD 1983 — Molt stage deter-mination in the Hawaiian spiny lobster Panulirus marginatus.J. crustacean Biol. 3: 208–216.MILLS, B. J. and P. S. LAKE 1975 — Setal development andmoult staging in the crayfish Parastacoides tasmanicus(Erichson), (Decapoda Parastacidae). Aust. J. mar. Freshwat.Res. 26: 103–107.PEEBLES, J. 1977 — A rapid technique for moult staging in liveMacrobrachium rosenbergii. Aquaculture 12: 173–180.POLLOCK, D. E. 1973 — Growth of juvenile rock lobster Jasuslalandii. Investl Rep. Sea Fish. Brch S. Afr. 106: 16 pp.POLLOCK, D. E. 1986 — Review of the fishery for and biologyof the Cape rock lobster Jasus lalandii with notes on larvalrecruitment. Can. J. Fish. aquat. Sci. 43(11): 2107–2117.REAKA, M. L. 1975 — Moulting in stomatopod crustaceans. 1.Stages of the moult cycle, setagenesis and morphology. J.Morphology. 146: 55–80.SILBERBAUER, B. I. 1971 — The biology of the South Africanrock lobster Jasus lalandii (H.Milne-Edwards). 2. The re-182 South African Journal of Marine Science 22 2000productive organs, mating and fertilisation. Investl Rep.Div. Sea Fish. S. Afr. 93: 46 pp.STEVENSON, J. R., GUCKERT, R. H. and J. D. COHEN 1968— Lack of correlation of some proecdysial growth and devel-opmental processes of the crayfish. Biol. Bull. mar. biol.Lab., Woods Hole 134: 160–175.TURNBULL, C. T. 1989 — Pleopod cuticular morphology as anindex of moult stage in the ornate rock lobster, Panulirusornatus (Fabricius 1789). Aust. J. mar. Freshwat. Res. 40:285–293.VAN HERP, F. and C. BELLON-HUMBERT 1978 — Setal develop-ment and molt prediction in the larvae and adults of thecrayfish, Astacus leptodactylus (Nordmann, 1842). Aqua-culture 14: 289–301.Isaacs et al.: Moult Stages in Jasus lalandii2000 183

Determination of moult stage in the South African West Coast rock lobster Jasus Lalandii (H. Milne Edwards) (Crustacea: Decapoda)

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Determination of moult stage in the South African West Coast rock lobster Jasus Lalandii (H. Milne Edwards) (Crustacea: Decapoda)

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