SCI. MAR., 68 (1): 127-137 SCIENTIA MARINA 2004

Female reproductive cycle of the Southwestern Atlantic estuarine Chasmagnathus granulatus (Brachyura: Grapsoidea: )*

ROMINA B. ITUARTE, EDUARDO D. SPIVAK and TOMÁS A. LUPPI Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Casilla de Correo 1245, 7600 Mar del Plata, Argentina. E-mail: [email protected]

SUMMARY: The female reproductive biology of a Chasmagnathus granulatus population inhabiting the area near the mouth of Mar Chiquita coastal lagoon, Argentina, was studied. An increase in air temperature during the spring is related to the start of the breeding period, when well defined egg-laying and hatching pulses were observed. Hatching is synchron- ic during the whole summer but the egg production was not, probably due to the gradual incorporation of young females to the reproductive population. Neither egg-laying nor larval release showed a clear relation to moon phase or tidal cycles, sug- gesting that reproduction is not rigidly programmed in this unpredictable habitat. Females moult at the beginning of autumn, after releasing the last larvae. However, a new cohort of ovocytes, which was in primary vitellogenesis before moulting, completed the secondary ovogenesis after moulting. Consequently, ovaries remained fully developed throughout the winter. Key words: Chasmagnathus granulatus, breeding cycles, hepatosomatic index, gonadosomatic index, hatching.

RESUMEN: CICLO REPRODUCTIVO DE HEMBRAS DEL CANGREJO ESTUARIAL DEL ATLÁNTICO SUDOCCIDENTAL CHASMAGNATHUS GRANULATA (BRACHYURA: GRAPSOIDEA: VARUNIDAE). – Fue estudiada la biología reproductiva de hembras de una población de Chasmagnathus granulatus en la boca de la laguna Mar Chiquita, Argentina. El incremento de la temperatura del aire en la primavera está relacionado con el inicio del periodo de cría, momento en el cual se observan pulsos de extrusión de huevos y eclosión de larvas bien definidos. La eclosión de larvas es sincrónica durante todo el verano, pero no así la producción de huevos, probablemente debido a la gradual incorporación de hembras jóvenes a la población reproductiva. Ni la extrusión de huevos ni la eclosión de larvas muestran una clara relación con las fases de la luna o los ciclos de marea, sugiriendo que la reproducción no está sujeta a un programa inflexible en un hábitat impredecible. Las hembras mudan a principios del otoño, después de las últimas eclosiones larvales. Sin embargo, una nueva cohorte de ovocitos, que estaban en vitelogéne- sis primaria antes de la muda, completan la vitelogénesis secundaria después de mudar. Consecuentemente, los ovarios están completamente desarrollados durante todo el invierno. Palabras clave: Chasmagnathus granulatus, ciclo reproductivo, índice hepatosomático, índice gonadosomático, eclosión.

INTRODUCTION cate resources “toward reproduction in times of scarcity and toward growth in times of abundance”, The existence of a conflict between growth and scheduling of growth and reproduction is not neces- reproduction is a common premise in studies of sarily determined by resource competition or physi- reproduction and life history patterns. Although ological antagonisms (Nelson, 1991). In fact, crus- long-lived iteroparous malacostracan females allo- tacean growth is the result of periodic moults of the exoskeleton, and since females of most malacostra- *Received January 7, 2003. Accepted September 22, 2003. can species incubate their eggs externally, they

REPRODUCTIVE CYCLE OF CHASMAGNATHUS GRANULATUS 127 should not moult during the breeding period simply González-Gurriarán, 1985; Fukui and Wada, 1986; to avoid the egg loss (Nelson, 1991). Elner and Beninger, 1992; Haddon and Wear, 1993, The reproductive activities of a female crab Gao et al., 1994; McDermott, 1998). (Crustacea: Brachyura) begin before the maturity Dense populations of the semi-terrestrial estuar- moult; the initial growth and development of ovo- ine burrowing crab Chasmagnathus granulatus cytes is based on autochthonous material (primary (Brachyura: Grapsoidea: Varunidae) are found from vitellogenesis). After this moult, the ovocyte growth Paranaguá Bay (Brasil) to San Antonio Bay involves the contribution of allochthonous material (Argentina) (Spivak, 1997). This species breeds dur- (secondary vitellogenesis). It has been shown that ing most of spring, all summer and the beginning of reserves stored in the hepatopancreas are mobilised autumn (Ruffino et al., 1994; Spivak et al., 1994, to the ovaries (Pillay and Nair, 1973; Paulus and 1996, 2001; López Greco and Rodríguez, 1999). Laufer, 1987; Kyomo, 1988). Later, ovocytes are The absence of ovigerous females in Mar Chiquita, fecundated and extruded, eggs are attached to the an Argentinian coastal lagoon, during winter has long pleopodal setae and the embryonic develop- been correlated with a decrease in feeding activities ment takes place in a sort of incubation chamber. caused by low air temperatures (Spivak et al., 1996). Extrusion and larval release may be synchronic in In addition, egg laying has been observed in the lab- intertidal , in agreement with circadian, circati- oratory at high and constant temperatures (21 ± dal and circalunar cycles (Saigusa, 1981, 1982, 1ºC), even during the non-reproductive season 1992; Forward, 1987; Zimmerman and Felder, 1991; (López-Greco and Rodríguez, 1999). On the other Morgan and Christy, 1994; Saigusa and Kowagoye, hand, C. granulatus females mated in the intermoult 1997), according to species and particular habitat. stage of the moult cycle, multiple ovipositions after Multiple broods within an instar are possible one mating were observed in laboratory reared crabs (Cheung, 1969), and the number may vary with (López-Greco and Rodríguez, 1999), and hatching season and size (age) (see Nelson, 1991 for a pulses synchronised with noctural ebbs were detect- review). Since the development of a new cohort of ed in the Mar Chiquita population (Anger et al., ovocytes may begin before the first clutch is 1994). This synchrony allows Mar Chiquita larvae extruded, the ovigerous females may have ovaries to be immediately exported to the sea. in primary or secondary vitellogenesis. When In the present study the female reproductive biol- hatching occurs, secondary vitellogenesis of the ogy of C. granulatus in Mar Chiquita was studied. second cohort is nearly complete, so a new clutch Specifically, we analyzed the effect of air tempera- may be soon extruded (Nelson, 1991). Several ture on the starting and duration of the breeding cycles of ovarian activity could occur during a period, the synchrony of extrusion and hatching reproductive season. The existence of these cycles pulses, the putative relationships of these pulses is evidenced by the successive peaks in the propor- with tides and lunar phases, and the possible mobil- tion of females with mature ovaries, and of oviger- isation of reserves accumulated in the hepatopan- ous females, observed during field studies creas to the ovary. Finally, we propose the schedule (González-Gurriarán, 1985; Zimmerman and of moulting and reproduction in this habitat. Felder, 1991; Sudha and Anilkumar, 1996; Mante- latto and Fransozo, 1999). Finally, the last cohort of ovocytes of the current season arrest their devel- MATERIALS AND METHODS opment at the end of primary vitellogenesis and a premoult process begins (Nelson, 1991). Study area The interval between mating and fecundation is highly variable: mating may be postecdysial, involv- Mar Chiquita coastal lagoon is located between ing soft-shelled females usually protected by the 37º32’ and 37º45’S and 57º19’ and 57º26’W, 35 km male, or anecdysial, involving hard-shelled females. NE of the city of Mar del Plata, Argentina. It has an Within the latter, it may occur anywhere in the long area of 46 km2 and a maximum depth of ca. 1.2 m intermoult period or may be restricted to a short (Fasano et al., 1982), and is divided into a wide period prior to egg extrusion, when the genital pore northern freshwater part and a narrow southern estu- operculum is decalcified (Fukui, 1993). Females of arine part. Water temperature and salinity show many Brachyuran species produce multiple egg great seasonal, daily and local variations (Anger et batches from single matings (Morgan et al., 1983; al., 1994, Reta et al., 2001). The mean water tem-

128 R. B. ITUARTE et al. val of ca. 7 days. The astronomic tides of January 2001, tabulated for Mar del Plata Harbour by the Servicio de Hidrografía Naval, Argentina, are shown in Figure 1a as an example. Air temperatures of Mar del Plata Airport, 35 km south of Mar Chiquita, were obtained from the Servicio Meteorológico Nacional, Argentina, and the National Climate Data Center, U.S.A. The highest temperatures occurred in January 2000 and February 2001, the lowest in July 2000. During the period 1981-1990, the maximum and minimum mean monthly temperatures were 26.8 and 3.1°C respectively (Fig. 1b). The number of days with temperature ≤ 0°C was 19.2 ± 2.71 per year during the period 1997 to 2002.

Collection and analysis

Crabs were collected weekly on a muddy beach located in the southern part of the lagoon (site #3, see Spivak et al., 1994), from November 7, 2000 to March 14, 2002. All crabs present on the surface or in burrows were collected by hand along several 10 m transects approximately perpendicular to the water edge. The number of transects varied accord- ing to crab density. Males were discarded, and females (N from 93 to 114) were transported to the laboratory and sorted into ovigerous and non- FIG. 1. – Chasmagnathus granulatus. a) Tidal regime and lunar ovigerous. The percentage of ovigerous to total phases in Mar del Plata during January, 2001; b) Maximum, mean and minimum monthly air temperatures registered in Mar del Plata females (POF) was calculated. A few eggs were between 1981 and 1990. removed from each ovigerous female, examined under microscope and classified into one of the 9 perature of this shallow water lagoon corresponds embryonic developmental stages (ES1 to ES9) pro- closely to air temperature cycles (Reta et al., 2001). posed by Bas and Spivak (2000). The frequency of Semidiurnal tides (amplitude < 1m) superimposed ovigerous females carrying embryos in each stage by irregular, often strong, wind action cause an (fn) was registered and a mean embryonic stage was irregular pattern of influx and outflux of water, calculated as follows: which is hampered by a sandbar at the entrance to Σ the lagoon (Anger et al., 1994). Intertidal environ- MES = ( ESn.fn)*100/No ments at the lagoon comprise mud flats and large surrounding cordgrass Spartina densiflora areas where n ranges from 1 to 9 and No is the number of (Olivier et al., 1972). The more abundant crab ovigerous females. species of Mar Chiquita lagoon are Chasmagnathus Non-ovigerous females were reared for 7 days in granulatus, Cyrtograpsus angulatus and Uca a 60 x 40 x 20 cm aquarium filled with 23 PSU uruguayensis. C. granulatus and U. uruguayensis water and examined daily in order to detect extru- inhabit the upper intertidal; C. angulatus inhabits sion. The water was at ambient temperature and was the lower intertidal and subtidal (Spivak et al., 1994; aerated continuously. The females were not fed dur- Spivak et al., 1996). ing this period. The percentage of females that Few data are available on the hydrographic and spawned during a week in comparison with non- climatic conditions of Mar Chiquita. The tidal ovigerous females (PE) was calculated. regime of the study area corresponds to a mixed, Females with developed embryos (ES7 to ES9) dominant semi-diurnal type: “large tides” (LT) and were placed individually in 1-litre flasks and exam- “half tides” (HT) alternate with a regular time inter- ined daily in order to detect the release of larvae.

REPRODUCTIVE CYCLE OF CHASMAGNATHUS GRANULATUS 129 The percentage of females with these embryos in comparison with all ovigerous females (PH) was calculated. Morphollogically mature females (n = 50), char- acterised by a wide pleon that covers the base of limb coxae, were collected monthly from October 1999 to April 2001, except in July and October 2001. They were transported to the laboratory, frozen to death at –10 ºC and dissected. Their ovaries were examined and classified into one of the following 5 stages: Stage 1: filiform and translucent; pale grey. Stage 2: both ovarian filaments tubular and nar- row ; orange, red or brown. Stage 3: both ovarian filaments tubular, wider but FIG. 2. – Chasmagnathus granulatus. Mean air temperatures and reproductive season duration in two successive years (2000-2001 without differences between the anterior and the and 2001-2002). *** significant differences between temperatures posterior part ; sometimes granular; brown to violet. (t-test, p < 0.05). Solid and dotted horizontal bars corresponds to the presence of ovigerous females during 2000-2001 and 2001-2002 Stage 4: the anterior part expanded, though not respectively. covering either the cardiac stomach or the hepatopancreas; the posterior part with both fila- ments already visible; always granular; orange to between the mean GSI and HSI, and between both dark violet. indexes and the mean air temperature of the current Stage 5: all the organ expanded, covering the car- month, were analysed by means of a correlation test. diac stomach and the hepatopancreas; always granu- When the statistical power of a performed test was lar; bordeaux to dark violet. below the desired power of 0.8, negative results The percentage of females with ovaries in each should be interpreted cautiously (Norman and stage was calculated. Streiner, 1996). Ovaries and hepatopancreas of these 50 morpho- logically mature females were carefully dissected, dried for 48 h at 80ºC, and weighed individually to RESULTS 0.0001 g; the exoskeleton and remaining organs were also dried for 48 h at 80ºC and weighed indi- The annual pattern of mean air temperatures pre- vidually to 0.01 g. Eggs of ovigerous females were sented a similar pattern during the two reproductive previously removed. The gonadosomatic and seasons (Fig. 2). However, August and October were hepatosomatic index (GSI and HSI) were calculated significantly warmer in 2001 than in 2000; the mean as the ratio between the dry weight of the organ and value observed in August 2001 (~10ºC) was reached the dry weight of the whole crab including the only in October 2000 (~11ºC) (Fig 2). The begin- organ, and expressed as a percentage. The mean GSI ning of a reproductive season coincided with a rise and HSI were calculated for each sample. in air temperature (Fig. 2). The minimum air tem- perature registered during each reproductive season Statistical methods was > 8°C (April 2001) and > 6°C (September 2001) (data not shown). The null hypotheses of no difference in monthly Ovigerous females were present from November temperatures between years were compared by Stu- 2000 to April 2001 during the first reproductive sea- dent test. The null hypotheses of no difference in son. Several peaks of the percentage of ovigerous time to larval hatching among females with embryos females (POF) were observed (Fig. 3a). Three of in stage 7 to 9, and in PH and PE between tidal and these peaks include > 70% of the collected females: lunar phases were analysed by ANOVA, after check- 80% in November, 73% in December, and 83% in ing for normality and homocedasticity. A spectral March. From December to February, POF was analysis was made for rhythmicity of egg extrusion between 36 and 70%. The POF reached the lowest and larval release, using the Kolmogorov-Smirnov value after the first peak (8% in November), and (K-S) d-test for significance. The relationships decreased continuously after the last peak, reaching

130 R. B. ITUARTE et al. FIG. 3. – Chasmagnathus granulatus. Percentage of ovigerous females (POF), mean embryonic stage (MES), percentage of egg-laying occur- rence (PE), and percentage of hatching occurrence (PH). a) and c) reproductive season 2000-2001, b) and d) reproductive season 2001-2002.

10% in April. The proportion of ovigerous females During the second reproductive season ovigerous that liberated larvae in the laboratory during the females were present from September 2001 to week that followed their collection (PH) ranged March 2002. Several peaks of POF were observed, between 3.8 and 66.7%; the highest values were but in a lower proportion than in 2000-2001: 72% in observed at the beginning and the end of the repro- October, 62% in December, 83% in January, 43% in ductive season and coincided with minimum POF February and 35% in February. POF reached its low- (Fig. 3a). est value after the first peak (November 2%). PH The mean embryonic stage (MES) increased dur- varied from 0 to 57%; the highest values coincided ing November 2000 to a maximum (66%), and with minimum POF (Fig. 3b). decreased to a minimum (36%) in December. The The MES was high from October to November MES ranged from 45 to 53% during January and 2001 (~60%), decreased to a minimum (30%) in February 2001, and increased during March 2001, December, and increased to 49% in January 2002. It reaching 70% at the end of this month (Fig. 3c). The remained at similar values during January and Feb- proportion of non-ovigerous females that laid eggs ruary and increased again, reaching 61% in March. during the week following their collection (PE) var- Several peaks of PE were observed, coinciding with ied from 0 to 33%. The values of PE increased dur- the lowest MES (Fig. 3d). ing the end of spring, reached its maximum in Larvae hatched successfully from all females December (33.3%) and decreased in the following 2 with developed embryos (stages 7, 8 and 9) in 41 of weeks. From January to February, PE varied the 45 observed samples. The time elapsed from between 3.9 and 12% (Fig. 3c). collection to hatching differed significantly among

REPRODUCTIVE CYCLE OF CHASMAGNATHUS GRANULATUS 131 FIG. 4. – Chasmagnathus granulatus. Tidal amplitude and the number of females that laid eggs and that released larvae in the laboratory each day during both reproductive seasons.

± ± embryonic stages: 3.6 1.22 d (ES7), 2.9 1.29 d The ovary of all ovigerous females studied dur- ± (ES8) and 1.2 0.81 d (ES9) (ANOVA, p < 0.0001). ing both reproductive seasons were in stage 1 to 3 The differences in hatching and egg laying pro- (Fig. 5a). Stage 1 (post-extrusion) predominated in portions (PH and PE) observed between 4 tidal con- most samples and the ovaries of all ovigerous ditions (spring LT, spring HT, neap LT, neap HT) females were at stage 1 at the beginning of the sec- and between 4 lunar phases were non-significant ond reproductive season (September 2001). Ovarian (ANOVA: PH-lunar phases, P = 0.1550, PE-lunar stages 4 and 5 were observed only in non-ovigerous phases, P = 0.6771; PH-tides, P = 0.6537, PE-tides, females. Most females had ovaries in stage 3 at the P = 0.4213). However, the power of the performed beginning of the non-reproductive period (April, tests wass < 0.8. 2000), but during the rest of this period (May to Larval release showed significant rhythmicity in August) ovaries were mostly in stage 5 (Fig. 5b). the 2000-2001 (Fisher Kappa: 5.825; Barlett K-S d: The GSI ranged between 0.2 and 1 during most 0.2686) and 2001-2002 (Fisher Kappa: 12.10; Bar- the reproductive season, except in September 2000 lett K-S d: 0.3308) reproductive seasons (Fig 4). The (Fig. 6). It increased at the beginning of the non- periodogram peaks corresponded to periods of 8, 15, reproductive season (April) and reached the highest and 27 days. Egg extrusion showed significant values during winter (ca. 3). The hepatosomatic rhythmicity in the 2000-2001 (Fisher Kappa: 9.807; index was always higher than the gonadosomatic Barlett K-S d: 0.1595) but not in the 2001-2002 index but showed a similar temporal pattern, with an reproductive seasons (Fig. 4). The periodogram increase during the non-reproductive season (Fig. peaks of the 2000-2001 season corresponded to peri- 6). In fact, a significantly linear relationship ods of 4, 10, and 20 days. between mean HSI and GSI was detected (analysis

132 R. B. ITUARTE et al. FIG. 5. – Chasmagnathus granulatus. Stages of ovarian develop- ment (SO1-SO5) of ovigerous (a) and total (b) females from October 1999 to April 2001.

FIG. 7. – Chasmagnathus granulatus. Relationships of mean hepatosomatic index (HSI) and gonadosomatic index (GSI) with the monthly mean air temperature. Data from the reproductive season 1999-2000. mean GSI and air temperature (analysis of variance of regression, P < 0.0001); these variables were neg- atively correlated (Fig. 7b). Although mean HSI diminished with air temperature, a significant rela- tionship was not found (P = 0.0374); however, the

FIG. 6. – Chasmagnathus granulatus. Monthly variation in the mean power of the performed test was < 0.8. hepatosomatic index (HSI) and gonadosomatic index (GSI). The percentage of ovigerous females (POF) indicates the reproductive seasons 1999-2000 and 2000-2001. DISCUSSION of variance of regression, P = 0.0005; Fig. 7a). How- ever, the HSI began to increase earlier than the GSI The life of mature female crabs has two out- at the end of both reproductive seasons (February vs standing, and externally evident, events: egg laying March 2000 and January vs February 2001 respec- and larval, or juvenile, release. Both extrusion and tively). On the other hand, the differences between hatching are generally programmed “so that brood GSI and HSI were high during most of the first release occurs at a time most appropriate for the reproductive season, diminished from May to growth of the young” (Adiyodi, 1988). Intertidal and December 2000, and increased again by the end of land crabs inhabiting temperate regions are general- the second reproductive season (Fig. 6). A signifi- ly seasonal breeders and avoid breeding during the cantly linear relationship was detected between winter months (Sastry, 1983; Adiyodi, 1988: 140).

REPRODUCTIVE CYCLE OF CHASMAGNATHUS GRANULATUS 133 Furthermore, the duration of the breeding season is demonstrated in (Nelson, 1991), negatively correlated with latitude in several grap- including non-brachyuran (Quackenbush, 1989; soid and ocypodid crabs (Emmerson, 1994; McDer- Harrison, 1990; Haefner and Spaargaren, 1993; mott, 1998; Leme, 2002). Chasmagnathus granula- Spaargaren and Haefner, 1994) and brachyuran tus breeds during most of spring and summer in Mar decapods (Pillay and Nair, 1973; Paulus and Laufer, Chiquita and, apparently, ovigerous females appear 1987; Kyomo, 1988). The energy partitioning of one month after the mean air temperature rises female crabs means that: i) lipids are stored in the above 10°C. Cold “limits the active season, and hepatopancreas of crabs (Adiyodi, 1969); ii) there hence time available for feeding, and therefore, the is a compromise between reproduction and growth energy available for growth and reproduction” of (Sastry, 1983; González-Gurriarán, 1985; Abelló, land crabs (Wolcott, 1988: 60); the same argument 1989; Nelson, 1991; Mantelatto and Fransozo, was applied to C. granulatus (Spivak et al., 1996), 1999; López-Greco and Rodríguez, 1999); and iii) although the annual variations in feeding activity nutrients stored in the hepatopancreas can be used have not yet been quantified. However, photoperiod for moulting (Zimmerman and Felder, 1991; Koga, is another factor that may control the beginning of 1995) or transferred to the ovaries (Pillay and Nair, female breeding seasons, acting alone (Zimmer- 1973; Paulus and Laufer, 1987; Kyomo, 1988). The mann and Felder, 1991) or associated with tempera- annual changes in hepatopancreas and ovary of ture (Knudsen, 1964; Pillay and Ono, 1979; Flores Chasmagnathus granulatus females can be and Negreiros Fransozo, 1998). Only careful exper- explained under these assumptions. During the imental evidence could help to separate the effects summer, part of the energy obtained from food must of photoperiod and temperature on the breeding sea- be used to prepare females for the autumn moult, son in C. granulatus. while the ovaries produce several clutches, until Female Chasmagnathus granulatus reached sex- reserves are exhausted by the end of March. A tran- ual adulthood in less than one year after their sient nutrient accumulation in the hepatopancreas recruitment in the Mar Chiquita lagoon (Luppi et al., may occur in January, and these reserves could be 2002). The presence of small ovigerous females was used during the premoult processes. From February evident at the beginning of summer. They produced to April, the hepatopancreas accumulated reserves more than one clutch during summer and moulted at that could be later transferred to the ovaries; the the beginning of autumn. A higher moult frequency ovaries were thus ready for the first oviposition that of C. granulatus was observed during early autumn took place in September. Interestingly, the eggs of in Mar Chiquita (Luppi and Bas, unpublished) and the first annual clutch of C. granulatus were larger in Samborombón Bay (López-Greco and Rodríguez, than those of subsequent clutches (Bas, 2001). 1999). Autumn was an active but unreproductive Since crabs fed during spring and summer, at least period. The mean air temperature was still above part of the nutrients obtained during this period 10°C, and crabs fed and accumulated reserves. Dur- could be used for successive cycles of ovarian ing the winter they remained inactive, inside their development. The growth of C. granulatus ovaries burrows, and apparently did not feed. At the begin- during the non-reproductive season was also ning of spring, they became active and, after a few observed in northern populations (Ruffino et al., weeks, these larger females were synchronously 1994; López-Greco and Rodríguez, 1999). ovigerous. During their second breeding season, Our results agree with the proposed schedule of they could also have produced more than one clutch moulting and reproduction in crabs, based on data and moult in autumn. The life span of these females from Neopanope sayi (Swartz, 1978) summarised was estimated in less than 3 years (Kittlein et al., by Nelson (1991: 84, Figure 4g), except at the end of 2000). Similar life-phases were described by the breeding season. Nelson’s (1991) figure showed Kyomo (1986, 1988) in Sesarma intermedia in that the last cohort of ovocytes arrested their devel- Japan. opment during primary vitellogenesis before moult- Ovocyte development involves the contribution ing, and was reinitiated after moulting. In fact, most of autochthonous and allochthonous material Chasmagnathus granulatus females had their (Adiyodi, 1988; Quackenbush and Keeley, 1988; ovaries in stage 1 during March (when adults usual- Nelson, 1991). The mobilisation of reserves stored ly moult, Bas and Luppi, unpublished). However, in the body fat or midgut gland (= hepatopancreas, the presence of developing ovaries during April and sensu lato) to the ovary during vitellogenesis was May suggests that secondary ovogenesis may begin

134 R. B. ITUARTE et al. soon after moulting and is completed in autumn. ovigerous females have been studied in other deca- The ovaries remain fully developed during the pod species (e.g. Somerton and Meyers, 1983; Paul whole winter. and Paul, 1996; Mantelatto and García, 1999). The Different patterns of the relationship between the increase in the rate of embryonic development of ovary and the hepatopancreas were observed in crabs observed at higher temperatures (González- other intertidal, estuarine, and burrow-building Gurriarán, 1985; Omori et al., 1997) and the tem- grapsoids. The minimum HSI values of Sesarma perature differences between Chasmagnathus gran- intermedia females were observed in winter, the ulatus microhabitats in Mar Chiquita (Spivak et al., maximum in summer and autumn; HSI increase pre- 1994) may also explain the asynchrony of embryon- ceded GSI increase. Females of this crab have accu- ic development during summer. mulated reserves in the hepatopancreas by the end of Well-defined hatching pulses of Chasmagnathus the reproductive season and use these reserves for granulatus were observed during both breeding sea- ovarian development in the following year (Kyomo, sons. Such synchrony may be expected at the begin- 1988). In Helice tridens and H. japonica, the maxi- ning of the season, as a consequence of extrusion mum HSI was observed in summer, together with pulses. However, hatching continues to be synchron- the minimum GSI; the maximum GSI values were ic during the whole summer, suggesting that females observed in winter and spring (Omori et al., 1997). or embryos could partially control the incubation The number of broods produced by a crab in a duration, as was demonstrated in other decapod single reproductive season could be as high as 13, as species (Sastry, 1983; De Vries and Forward, 1991). Cheung (1969) observed in Menippe mercenaria. A The timing of larval release with particular environ- single Chasmagnathus granulatus female could mental conditions is usually “related to survival of hatch 6 times in a season in Mar Chiquita lagoon. the adult female and her larvae” (Forward, 1987). The mean period between hatches was 20.8 days; the An export strategy for larvae of C. granulatus in duration of the embryonic development estimated in Mar Chiquita has been postulated on the basis of the the laboratory was 21 days in vitro (Bas and Spivak, higher frequency of zoea I in the lagoon plankton 2000) and ca. 15 days in vivo (Bas and Luppi, unpub- during nocturnal ebbs (Anger et al., 1994). This lished). Our data agree with reports on the incubation strategy would make it possible to avoid the low period duration (20 to 30 days at a temperature of ca. salinity of the lagoon and the effect of visual orient- 20°C) and number of broods per year (2-6) in many ed predators. In fact, C. granulatus zoeae I could not grapsoid crabs (Kyomo, 1986; Fukui, 1988; Zim- survive for a long time at reduced salinities (Anger mermann and Felder, 1991; Omori et al., 1997; and Ismael, 1997). López Greco and Rodríguez McDermott, 1998). However, all these figures dif- (1999) detected a lunar hatching rhythm in Sam- fered sharply from those reported for another Chas- borombón females kept under constant laboratory magnathus granulatus population: females collected conditions. in Samborombón Bay and reared in the laboratory at Reproductive lunar or tidal rhythms were 21°C produced 4 hatches separated by 60 days observed in several intertidal or terrestrial grapsoids (López-Greco and Rodríguez, 1999). The observed (Forward, 1987; Zimmermann and Felder, 1991; differences between C. granulatus populations are Quinn et al., 1997; Saigusa and Kawagoye, 1997; probably a consequence of temperature and laborato- Omori et al., 1997; Flores et al., 2002). Neither the ry rearing. The time between hatching and a new percentage of females of C. granulatus in Mar Chiq- extrusion was 7 days in Sesarma intermedia uita that spawned during a week in comparison with (Kyomo, 1986); no such information is available for non-ovigerous females, nor the percentage of C. granulatus in Mar Chiquita. females with advanced embryos in comparison with Two pulses of egg laying were observed at the all ovigerous females, coincided with a particular beginning of the breeding season in Mar Chiquita, lunar phase or an astronomically predicted tidal con- probably as a consequence of a synchronic ovocyte dition. Although a circatidal larval release rhythm development during winter. On the other hand, egg was detected using spectral analysis, this pattern is production was not synchronic during the rest of the not as clear as that observed in several intertidal summer, probably due to the gradual incorporation marine species (e.g. Gove and Paula, 2000, Figs. 4 of smaller females, which were extruding their first and 8). The geomorphology and climatology of Mar egg clutch, to the reproductive population. The Chiquita made this habitat unpredictable (Anger et fecundity and reproductive behaviour of young al., 1994), so it is reasonable to expect that repro-

REPRODUCTIVE CYCLE OF CHASMAGNATHUS GRANULATUS 135 ductive events of C. granulatus are not rigidly pro- Fukui, Y. – 1988. Comparative studies on the life history of the grapsid crabs (Crustacea, Brachyura) inhabiting intertidal cob- grammed. Thus, most larvae would hatch under ble and boulder shores. Pub. Seto Mar. Biol. Lab., 33: 121-162. favourable environmental conditions. Fukui, Y. – 1993. Timing of copulation in the molting and repro- ductive cycles in a grapsid crab, Gaetice depressus (Crustacea: Brachyura). Mar. Biol., 117: 221-226. Fukui, Y. and K. Wada. – 1986. Distribution and reproduction of four intertidal crabs (Crustacea, Brachyura) in the Tonda River AKNOWLEDGEMENTS Estuary, Japan. Mar. Ecol. Progr. Ser., 30: 229-241. Gao, T., S. Tsuchida and S. Watanabe. 1994. Growth and repro- duction of Rhynchoplax caralicola Rathbun (Brachyura: This paper was funded by the Universidad de Hymenosomatidae). Crust. Res., 23: 108-116. Mar del Plata (UNMdP, grant 15/E082) and the González-Gurriarán, E. 1985. Reproducción de la nécora Macropi- pus puber (L.) (, Brachyura), y ciclo reproductivo en Consejo Nacional de Investigaciones Científicas y la Ría de Arousa (Galicia, NW España). Bol. Inst. Español Técnicas (CONICET, grant PIP 838/98) to EDS. Ocean., 2: 10-32. Gove, D. and J. Paula. – 2000. Rhythmicity of larval release in three This paper is based on work done by RBI in partial species of intertidal brachyuran crabs (Crustacea: Brachyura) fulfilment of the “Licenciada en Biología” degree at from Inhaca Island (Mozambique). Mar. Biol., 136: 685-691. Haddon, M. and R. Wear. – 1993. Seasonal incidence of egg-bear- the UNMdP. We are grateful to two anonymous ing in the New Zealand paddle crab Ovalipes catharus (Crus- reviewers for helpful comments and advice. tacea : Brachyura), and its production of multiple egg batches. N. Z. J. Mar. Fresh. Res., 27: 287-293 Haefner, P.A. and D.H. Spaargaren. – 1993. 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