Female Pleopods Research Articles

New Nemertean Worms (Carcinonemertidae) on Bythograeid Crabs (Decapoda: Brachyura) from Pacific Hydrothermal Vent Sites

Several species of crabs from hydrothermal vent sites in the Pacific Ocean were found to be infested by small, symbiotic nemertean worms. Worms occurred on both male and female crabs, and were located in mucous sheaths adhering to the axillae between the limbs of males and females, the setae of the pleopods of females, and the sterna of infested male and female crabs. Only juvenile and regressed adult worms were observed, primarily because no ovigerous hosts were examined. Similar species of worms mature by eating eggs, then regress or die after host eclosion. Based on the size of the worms from the vent crabs, their habitus with their crustacean hosts, the presence of accessory stylet pouches, and the presence of a single stylet on a large basis (monostiliferous), we place the worms in the family Carcinonemertidae, within the genus Ovicides. Infestations were found on crabs from vent sites on the western Pacific back-arc basins, on the southern East Pacific Ridge, and on the Pacific-Antarctic Ridge, indicating a widespread distribution of the symbioses. This represents the first record of Carcinonemertidae from a deep-sea host, a new host family, Bythograeidae, for these symbionts, as well as the first record of parasitism on a deep-sea bythograeid crab.

Nephropid lobsters from the Indian Ocean with descriptions of four new species (Crustacea: Decapoda: Nephropidae)

Seventy-five specimens of Nephropid lobsters captured using bottom trawls at 24 stations in the Indian Ocean include nine species ofNephropsis, three species ofMetanephrops and one species ofThymopides, among which four species ofNephropsis are new to science. Thelyca of females and gonopods of males are described for the first time in some species. Some data concerning fecundity, i.e. the numbers of eggs attached to pleopods of females, are provided. All species examined have a hitherto unknown structure on pereopod 5, which is presumably a “stridulating organ”. In the northern part of the Indian Ocean the nephropids are found deeper compared to their depth range in other areas. This is thought to be a result of warm, deep water masses from the Red Sea and the Gulf of Oman.

THE FECUNDITY, TIME OF EGG DEVELOPMENT AND JUVENILE PRODUCTION IN SPINY-CHEEK CRAYFISH (ORCONECTES LIMOSUS) UNDER CONTROLLED CONDITIONS

We comprehensively describe the fecundity and time of embryonic development of the spiny-cheek crayfish (Orconectes limosus). Linear relationships between female size and ovarian fecundity, pleopodal fecundity, and production of juveniles at the 3rd stage, were confirmed. The ovarian fecundity was evaluated for the smallest as well as largest females in the sampled population (43-93 mm of body length); the number of oocytes (eggs) ranged widely, between 46 and 505. No significant difference was found between the ovarian and pleopodal fecundity observed just after egg laying. The value of the female gonadosomatic index just before laying was 4.2 ± 1.8% (0.8-7.7%). The mean diameter of eggs on female pleopods was 1.8 ± 0.2 mm (1.45-2.15 mm). A statistically significant difference was found between the numbers of eggs carried on individual pairs of pleopods. Mean time from laying to hatching was 46 ± 3.8 days (37-56 days), i.e. 647 ± 39.9 CTU (Celsius Temperature Units = degrees Celsius × days). Mean production of juveniles at the 3rd stage was found to be 135.7 ± 67.24 (15-243) juveniles. The early sexual maturation and also high number of juveniles at the 3rd stage per female gives this species a good predisposition for quick establishment in new localities.

Fecundity and sexual maturity of the crab Macrophthalmus depressus (Brachyura: Ocypodidae) from Inhaca Island, Mozambique

Some reproductive aspects of the ocypodid crab Macrophthalmus depressus, were investigated, with emphasis on fecundity and sexual maturity. Random intertidal crab samples taken in October 2002 were identified, sexed, measured, checked for the presence of eggs on female pleopods, dissected for gonad analysis and their egg numbers were determined. Fecundity averaged 1249.86 ± 991.96 eggs, ranging from 100 to 5000 eggs, increasing in accordance with female size. A very low variation in number of eggs was observed within the same size class, probably indicating synchronous spawning within the same reproductive season. Gonad analysis suggested that females and males become mature at carapace widths of 13.4 and 13.6mm, respectively. The potential effects of variations in fecundity in this species, and in the Ocypodidae family, were compared and discussed.

Exploring the Mechanisms Causing a High Allometric Value of Female Pleopod in the Crayfish Procambarus clarkii

Female pleopods in Procambarus clarkii have a function of holding eggs, and their length shows positive allometry. It is likely that the positive allometry has resulted from directional selection in terms of egg holding ability. Firstly, we examined the allometry of reproductive potential (ovarian egg number). The allometric value of reproductive potential was lower than that of pleopod length, which indicates that the positive allometry of pleopod length is not merely the reflection of the allometry of reproductive potential. Secondly, we examined the relationship between the relative length of pleopod and egg holding ability to test the presence of directional selection on the pleopod length, and then compared the strength of the directional selection between the individuals differing in their body sizes to infer the mechanisms causing the positive allometry for female pleopods. There was a positive relationship between relative pleopod length and relative egg mass remaining to the pleopod, and this relationship was stronger in small individuals. These relationships were not merely the reflection of relationship between pleopod length and reproductive potential. These results indicate that directional selection was acting on the length of female pleopods, and the strength of the directional selection was stronger in smaller individuals. Therefore, it appears that the positive allometry of female pleopods in P. clarkii has been caused by the constraint for possessing longer pleopods in small individuals, although the mechanisms of the constraint remain unknown.

Reproductive Aspects of a Tropical Population of the Fiddler Crab Uca annulipes (H. Milne Edwards, 1837) (Brachyura: Ocypodidae) at Costa Do Sol Mangrove, Maputo Bay, southern Mozambique

Uca annulipes(H. Milne Edwards) is the dominant fiddler crab inhabiting mangrove forests in East Africa. However, several aspects concerning its reproduction are poorly known. Such information is necessary for a better understanding of several biological aspects occurring in this species. The aim of this study was to assess the reproductive biology of Uca annulipes as well as some factors determining its breeding season. Samplings were undertaken from January to December 2002 at Costa do Sol, a tropical mangrove forest around Maputo Bay, southern Mozambique. Crabs were randomly sampled, measured for carapace width (CW) and checked for the presence of eggs on female pleopods. Like most tropical brachyurans, Uca annulipes follows a continuous reproduction throughout the year with peaks of spawning during summer season and low frequency of egg-bearing females during winter. The frequency of ovigerous females was correlated with the air temperature (r 2= 0.652, p < 0.05) and rainfall (r 2= 0.897, p < 0.001), with the last parameter being the most important factor regulating the reproductive activity of this crab.

Energy storage during the transition from endogenous to exogenous feeding in Australian redclaw crayfish Cherax quadricarinatus (Von Martens, 1898)

Summary The Australian redclaw crayfish Cherax quadricarinatus hatches at an advanced stage. Two post-hatching stages rely on yolk reserves before the organism becomes a juvenile. After a juvenile appears, the yolk is depleted and young crayfish might spend a few days among female pleopods before starting to feed independently. During this phase, the juvenile organism needs alternative energy sources. Offspring from three females were analyzed with histological and histochemical techniques, from hatching until reaching the 2-week juvenile stage, to trace digestive system development and internal organ lipid and glycogen accumulation. Neutral lipids are stored in specialized cells of the hepatopancreatic tissue until the juvenile stage is reached. An increasing rate of accumulation was found. Glycogen was stored in hepatopancreas and tail muscle cells until post-embryo II, and no increasing or decreasing rate was found in storage functions.

Sexual difference in modes of selection on the pleopods of crayfish (Decapoda: Astacoidea) revealed by the allometry of developmentally homologous traits

Crayfish have five pairs of abdominal limbs called pleopods. In males, the first and second pairs of pleopods are used for transferring spermatophores to the female during copulation. The remaining pleopods in males have no obvious function. Female crayfish use their pleopods to carry eggs. Accordingly, it is expected that the selection pressures that act on the pleopods differ between males and females. To test this hypothesis, we estimated modes of selection on pleopods in two species of crayfish (Procambarus clarkii and Pacifastacus trowbridgii) by comparing allometric relationships in functional and nonfunctional pleopods. Since pleopods are serially homologous traits, developmental constraints on these traits appear to be minimal. The lengths of the first male pleopods, used in copulation, showed lower allometric values and less dispersion around the regression line, suggesting that they have been under stabilizing selection. This likely occurs because the major selective force is the ability of males to copulate with females of various sizes. The pleopods of females showed higher allometric values than pleopods of males without an assigned function. This suggests that the pleopods of females have been under directional selection, most likely because they are longer and can therefore carry more eggs.

Population biology of the Norway lobster, Nephrops norvegicus (L.) in the Firth of Clyde, Scotland II: fecundity and size at onset of sexual maturity

The fecundity and size at onset of sexual maturity of Nephrops norvegicus was estimated at different locations within the Firth of Clyde, S.W. Scotland. The “potential” fecundity was estimated from oocyte counts in mature ovaries, while estimates of “actual” fecundity were made from counts of the eggs attached to the pleopods of ovigerous females. Size at onset of maturity of Nephrops norvegicus was estimated from the study of primary (ovary maturity and eggs on pleopods) and secondary (allometric) sexual characteristics. Relationships between potential fecundity and female carapace length were found to conform to a power function (F=aLb). Comparison of the logarithmic formulations of the relationships for seven locations revealed no differences in power terms, but there were significant differences in the constants. Results suggested that differences in fecundity mainly reflected a geographical variation in oocyte volume (expressed in terms of mean dry weight) which appeared to be related to growth. Where growth rate was characterized by a low value for the asymptotic length of the carapace (L∞), females appeared to have smaller oocytes and larger size-specific fecundity. Estimates of size at onset of sexual maturity varied over small geographic scales (tens of km) and ranged between 21–34 mm carapace length for females and 29–46 mm for males, the estimate obtained from the different approaches being similar. Size at onset of maturity was positively related to L∞(p<0.05) and negatively related to adult density (p<0.05). Age at onset of maturity appeared relatively constant geographically but varied between the sexes (males, 4–4.5 years; females, 3–3.5 years).

MICROTHELPHUSA SUCREENSIS, A NEW SPECIES OF PSEUDOTHELPHUSIDAE (DECAPODA), WITH NOTES ON ABNORMALITIES IN THE SEXUAL APPENDAGES OF FRESH-WATER CRABS

Malformations of the sexual appendages of Neotropical freshwater crabs are very rare. In two lots of specimens of a new species of the pseudothelphusid, Microthelphusa sucreensis, collected in 1930 and 1993, one male specimen from each lot has gonopodal malformations. In one case, the left first gonopod displays gross morphological deviations from the normal shape, and in the second case the right second gonopod has an additional rudimentary appendage resembling the first gonopod. In the Trichodactylidae, a specimen of Sylviocarcinus pyriformis (Pretzmann, 1968) was observed to posses a bifid first left male gonopod. An intersexual specimen of Valdivia serrata White, 1847, had normal first and second male gonopods and three pairs of additional pleopods all similar to the second gonopod. The left appendage on the fifth pair was clearly a female pleopod.

A new species of Gastrosaccus (Crustacea, Mysidacea) from Algoa Bay (South Africa)

Gastrosaccus wittmanni sp. nov. was collected from surface-waters near Kings Beach in Algoa Bay (South Africa). Morphologically, it is characterised by having seven strong spines on each side of the telson. In between the strong spines, spinules are present except between the first most proximal pair. The endopod of the first female pleopod bears one terminal plumose seta. Most of the setae on antennules, antennae, thoracopods, pleopods and uropods are jointed.

Life cycle of the pea crabpinnotheres halingisp. Nov., an obligate symbiont of the sea cucumberholothuria scabrajaeger

Abstract A new species of pea crab, Pinnotheres halingi sp. nov. (Pinnotheridae), found encysted in the right respiratory tree of the sea cucumber, Holothuria scabra (Holothuridea), from Solomon Islands, is described. The reproduction, infestation and pairing behaviour of the crabs were investigated through field observations and experiments. Infestation frequency in 8 monthly samplings of 25–30 holothurians was 98.6±2.6% in Kogu Halingi bay and 0% in two nearby sites. Of 403 pea crabs, 91.4% were found in pairs of opposite sex, 7.9% were single females and <1% were single males. The embryos developed on the female pleopods over ca. 30 days from fertilisation to the release of first zoeae and subsequently went through five pelagic zoeal stages. Infestation occurred at the megalops stage after about 59 days of development. A single pea crab (male or female) per host was found three months after larval infestation. Young males appeared to be strongly attracted to hosts that sheltered a single female, suggesting that pairing occurred as a male <6 mm carapace width joined a female. Larger crabs could not enter the host. Copulation was observed within the female cyst, preceding or overlapping oviposition. The male then progressed away from the female and from the anus, forming its own cyst along the way. Both larvae and small sub-adults invaded H. scabra with a minimum length of 80 mm, exclusively. P. halingi induced atrophy of the right respiratory tree of its host.

Fecundity of the Norway lobsternephrops norvegicusin galicia (NW Spain) and a review of geographical patterns

Abstract The fecundity of the Norway lobster Nephrops norvegicus in Galician waters (NW Spain) was estimated based on the number of eggs attached to the pleopods of ovigerous females in the initial, middle and final stages of the incubation period. The number of eggs per brood was related allometrically to the carapace length (CL), with an allometry coefficient ranging between 3.0 and 4.1 in the different incubation stages (P>0.05). Incubation lasts 6–7 months (from August–September to January–February) and the average egg loss is estimated to be 44% during this period. The mean fecundity (corresponding to a mean CL of 38.6 mm) was 2636 eggs in the initial stage and 1475 in the middle and final stages of incubation. The literature points to a high variability in the fecundity of the Norway lobster throughout its geographical range of distribution. Fecundity decreases with latitude in the NE Atlantic from Western Ireland to the South of Portugal, with the Mediterranean populations showing lower values than those in the Atlantic. However, considering the periodicity of spawning, which tends to be biennial towards the northern distribution area, the annual production of eggs per female may be similar in the different zones and may even increase towards the south. Egg loss during the incubation period has been estimated at between 32 and 68% for the different geographical areas.

Male sexual ornament size but not asymmetry reflects condition in stalk–eyed flies

Models of sexual selection predict that females use ornament size to evaluate male condition. It has also been suggested that ornament asymmetry provides females with accurate information about condition. To test these ideas we experimentally manipulated condition in the stalk-eyed fly, Cyrtodiopsis dalmanni, by varying the amount of food available to developing larvae. Males of this species have greatly exaggerated eyestalk length and females prefer to mate with males with wider eyespans. Our experiments show that male ornaments (eyestalks) display a disproportionate sensitivity to condition compared with the homologous character in females, and to non-sexual traits (wing dimensions). In contrast, in neither sex did asymmetry reflect condition either in sexual ornaments or in non-sexual traits. We conclude that ornament size is likely to play a far greater role in sexual selection as an indicator of individual condition than does asymmetry.

Analysis of Size, Gonadal Maturation, and Functional Maturity in the Spiny Lobster Panulirus japonicus (Decapoda: Palinuridae)

ABSTRACT Relationships between relative growth of various body parts, gonadal maturation, and functional maturity were examined in male and female Panulirus japonicus by regression techniques and histological study of the ovary, testis, and vas deferens. Relative growth of the first pleopod and the first and second pereiopods against the carapace length (CL) is described best by two power regressions for both sexes, except for the male first and second pereiopods, which are described by three power regressions. Sexual differences in relative growth were observed when size exceeded 28-mm CL for the pleopod, and 52- and 54-mm CL for the first and second pereiopods, respectively. In all sizes less than these CLs, regressions between males and females were not significantly different from each other. For female pleopods, an inflection point was observed at 43-mm CL, whereas it occurred at 52- and 54-mm CL in male pereiopods. Females with immature ovaries often were less than 45-mm CL and their gonadosomatic indices were less than 1%, whereas all females greater than and including 45-mm CL had developing or ripe ovaries. In males, sperm were present in the testis and vas deferens of all individuals examined histologically (≧37-mm CL). In individuals greater than and including 54-mm CL, ratios of the diameter of the middle vas deferens to that of the posterior vas deferens were almost constant, and high sperm density was observed in the middle vas deferens, whereas in some individuals less than 54-mm CL sperm were absent in a part of the middle vas deferens and the ratio was low. These histologically observed values correspond well with the inflection points of the relative growth regressions for female pleopods (43-mm CL) and those in male pereiopods (52- and 54-mm CL). This indicates that the inflection points are closely related to gonadal maturation in females and functional maturity in males.

ANALYSIS OF SIZE, GONADAL MATURATION, AND FUNCTIONAL MATURITY IN THE SPINY LOBSTER PANULIRUS JAPONICUS (DECAPODA: PALINURIDAE)

Relationships between relative growth of various body parts, gonadal maturation, and functional maturity were examined in male and female Panulirus japonicus by regression techniques and histological study of the ovary, testis, and vas deferens. Relative growth of the first pleopod and the first and second pereiopods against the carapace length (CL) is described best by two power regressions for both sexes, except for the male first and second pereiopods, which are described by three power regressions. Sexual differences in relative growth were observed when size exceeded 28-mm CL for the pleopod, and 52- and 54-mm CL for the first and second pereiopods, respectively. In all sizes less than these CLs, regressions between males and females were not significantly different from each other. For female pleopods, an inflection point was observed at 43-mm CL, whereas it occurred at 52- and 54-mm CL in male pereiopods. Females with immature ovaries often were less than 45-mm CL and their gonadosomatic indices were less than 1%, whereas all females greater than and including 45-mm CL had developing or ripe ovaries. In males, sperm were present in the testis and vas deferens of all individuals examined histologically (≧37-mm CL). In individuals greater than and including 54-mm CL, ratios of the diameter of the middle vas deferens to that of the posterior vas deferens were almost constant, and high sperm density was observed in the middle vas deferens, whereas in some individuals less than 54-mm CL sperm were absent in a part of the middle vas deferens and the ratio was low. These histologically observed values correspond well with the inflection points of the relative growth regressions for female pleopods (43-mm CL) and those in male pereiopods (52- and 54-mm CL). This indicates that the inflection points are closely related to gonadal maturation in females and functional maturity in males.

HISTOLOGY AND EXTERNAL MORPHOLOGY OF A GYNANDROMORPH OF QUADRELLA CORONATA DANA (DECAPODA: TRAPEZIIDAE)

ABSTRACT Two gynandromorph specimens of the trapeziid crab Quadrella coronata Dana were collected in the Philippines. The specimens display both the female characteristic broad abdomen and male pleopods. Histological examination revealed only fully developed testes.

EGGS OFPALAEMON MACRODACTYLUS:I. ATTACHMENT TO THE PLEOPODS AND FORMATION OF THE OUTER INVESTMENT COAT

Eggs of the estuarine shrimp, Palaemon macrodactylus, were examined for their method of attachment during the brooding period. They were attached to each other and to setae of the maternal pleopods by an externally applied outer investment coat that is believed to originate within the pleopods. A precursor substance was stored in packets extending longitudinally along the basipodites of the female pleopods, apparently originating in specialized epithelial cells continuous with the packets. At ecdysis prior to oviposition, the packets became depleted and the attachment or adhesive material became evident externally, conforming to the external surfaces of the pleopods. This occurred in the presence and absence of mature eggs in the ovary. If mature eggs were present, they were soon (within one-half day) extruded into the incubation chamber, coated with the adhesive material, and attached. Both fertilized and unfertilized eggs attached in the same manner, although unfertilized eggs were either shed or removed by the female within a few days. Eggs from pleopod-excised females did not attach, had no outer investment coat, and deteriorated rapidly. This attachment mechanism differs from those described for other decapods.

A COMPARISON OF ARTIFICIAL INCUBATION METHODS USING OVA OF THE RED CRAB GERYON QUINQUEDENS SMITH (DECAPODA, BRACHYURA)

The efficacy of culture systems for incubating eggs of the commercially important red crab Geryon quinquedens was investigated. Three artificial systems, two flow-through and one static, were designed and tested over a 60-day incubation period. During the incubation period, death was due primarily to the fungus Lagenidium and other diseased conditions reported herein. Although the long development time of Geryon eggs precluded hatching during the study period, development did proceed to the C+ stage of Meredith (1952). A comparison of egg incubation techniques for decapod crustaceans shows that certain techniques are more successful than others, and the two alternative methods evaluated in the current study are among the most effective. Recent investigations into the physiology, biochemistry, genetics, embryology, taxonomy, aquaculture, and the effects of toxicants on decapod crustaceans have resulted in a marked increase in interest in methodology for hatching and larval rearing of these organisms (Kinne, 1977). In spite of the fact that the decapods are a large and diverse group relatively few techniques for incubating ova have emerged. Allowing the eggs to mature and hatch while still attached to the specialized setae of the female pleopods (Rice and Williamson, 1970) is still the most widespread technique. While release of larvae from ovigerous females is successful in some instances, this method of incubation may be neither possible nor desirable in many others. Successful techniques for the artificial incubation of decapod eggs have used either flow-through or static designs. Flow-through systems are far less intensive and permit mass culture, but static systems permit the effective use of chemotherapeutic agents to control bacterial and fungal pathogens. Hagmeier (1933), in order to hatch eggs of Homarus gammarus, used a flow-through incubator in which a small egg container was maintained in an aquarium with a continuous flow-through of sea water. Phillips (1971) hatched eggs of the English prawn Palaemon serratus using an inverted Fiberglas? cone with a ceramic air diffuser set at its base to provide aeration and circulation while water flowed continuously through the vessel. Lochhead and Newcombe (1942) hatched a high percentage of Callinectes sapidus eggs in a static system consisting of shallow pans providing neither circulation nor chemotherapeutic agents, but they reported increased rates of mortality as egg densities increased. Costlow and Bookhout (1960) developed a static system now widely used. In this system, eggs are placed in compartmentalized plastic boxes, the water treated with antibiotics, and the boxes agitated on a mechanical shaker during incubation. Wickins (1972) hatched ova of Palaemon serratus in a static system, but used gentle water currents created by rising air bubbles to provide continuous circulation of the eggs. The present study was undertaken to develop and evaluate additional artificial hatching methods and to ascertain parameters necessary for successful egg hatching of the red crab Geryon quinquedens in the laboratory. Geryon was selected because data were available for comparison with hatching of eggs carried by the female (Perkins, 1973) and with the static system of Costlow and Bookhout (Sulkin and Van Henkelem, unpublished). In addition, Geryon quinquedens was chosen be

Artificial incubation of the eggs of the crayfish Austropotamobius pallipes (Lereboullet)

In Great Britain, incubation time for eggs of the native crayfish, Austropotamobius pallipes, is approximately 9 months, with hatching occurring in May and June in Midlands waters. Artificial incubation at higher than ambient temperature would possibly reduce this time and make juveniles available for stocking in early spring. To test this hypothesis, fertile eggs were removed from the pleopods of ovigerous females maintained at ambient temperatures at different times (30-day intervals from late November through late April) and incubated in flowing water baths at 7 ± 1°C, 13 ± 1°C and 18 ± 1°C. Only eggs stripped from females from late January–April survived to hatching in the artificial incubation system, and none survived at 7 ± 1°C. However, incubation at 13 ± 1°C and 18 ± 1°C produced large numbers of juveniles as early as March and April. Overall, 13 ± 1°C was the best incubation temperature, considering both survival to hatching (average of 72% from February through April) and early development of the hatchlings. Daily dosing of the eggs with malachite green (10–20 ppm) eliminated fungal infections from the artificial incubation systems.