Showing papers in "Journal of Crustacean Biology in 1988"
TL;DR: The Biology of the land crabs: an introduction Warren W. Burggren and Brian R. McMahon present a meta-analyses of the crabs' behaviour and physiology, which shows clear trends in growth, molting, and evolution.
Abstract: 1. Biology of the land crabs: an introduction Warren W. Burggren and Brian R. McMaHon 2. Evolution, systematics and geographical distribution Richard G. Hartnoll 3. Ecology Thomas G. Wolcott 4. Behaviour David W. Dunham and Sandra L. Gilchrist 5. Reproduction and development Rita G. Adiyodi 6. Growth and molting Richard G. Hartnoll 7. Ion and waterbalance Peter Greenaway 8. Respiration Brian R. McMahon and Warren W. Burggren 9. Circulation Warren W. Burggren and Brian R. McMahon 10. Energetics and locomotion Clyde F. Herreid II and Robert J. Full 11. Epilogue Brian R. McMahon and Warren W. Burggren.
271 citations
TL;DR: Size-at-instar, growth-per-molt, reproductive schedules, and morphometric allometries were investigated in four sympatric species of Cancer (magister, the Dungeness crab, gracilis, productus, and oregonensis) in Garrison Bay, North Puget Sound.
Abstract: Size-at-instar, growth-per-molt, reproductive schedules, and morphometric allometries were investigated in four sympatric species of Cancer (magister, the Dungeness crab, gracilis, productus, and oregonensis) in Garrison Bay, North Puget Sound. Complementary observations were made on mating systems, mortality, habitat utilization patterns, and feeding. Numerical methods were successfully employed to discriminate instars in size-frequency distributions. Growth pattern, contrary to our expectation, was determinate in the four species. Geographic variation in prereproductive growth rate of C. magister is attributed to environmental factors. It is suggested that an independent stock may inhabit the Strait of Georgia-North Puget Sound area. Observations on mating behavior suggest that these polygynic species have different types of mating systems, leaning towards resource defense in C. oregonensis, female defense in C. gracilis (and perhaps also in C. productus), and explosive breeding assemblages in C. magister. Degree of sexual dimorphism is consistent with this hypothesis. Adult males of C. gracilis, C. productus, and C. oregonensis have proportionally larger chelae than females; no significant dimorphism was detected in C. magister. Male C. gracilis and C. productus show two clear allometric phases in the chela-carapace size relation. Contemporary studies of diversity within decapod guilds have frequently been done with food-resource partitioning as an explicit or implicit hypothesis. In contrast, we stress the importance of habitat, mating systems, and sexual selection as primary mechanisms underlying the diversification of this genus. the genus Cancer originated during the Eocene, presumably in the Northeast Pacific, and was well diversified in the Miocene (about 15 million years ago) (Nations, 1975). Nations (1975, 1979) postulated a radiation from this area (center of origin) into the Northwest Pacific, the North Atlantic, the Southeast Pacific, and then to New Zealand. The genus is at present restricted to cold temperate waters, and is maximally diversified in the Northeast Pacific, where we conducted our studies. Four species coexist in Garrison Bay (the study area), a small, shallow embayment in North Puget Sound. There are many publications dealing with one of them, Cancer magister (the Dungeness crab), but little is known about the other three (C. productus, C. gracilis, and C. oregonensis). Nevertheless, even for C. magister there are unexplained discrepancies between the life-history schedules reported for different geographic areas. One goal of the present study was to assemble and compare (within and between species) such schedules for the four species. Whenever possible we tried to
103 citations
TL;DR: A comparative morphological study of the brain and medulla terminalis of the spiny lobster Panulirus argus and the crayfish Procambarus clarkii is presented as a basis for investigations of the functional organization of their olfactory systems.
Abstract: We present a comparative morphological study of the brain and medulla terminalis (fourth eyestalk ganglion) of the spiny lobster Panulirus argus and the crayfish Procambarus clarkii as a basis for investigations of the functional organization of their olfactory systems. Both the brain and medulla terminalis of P. argus display folding with respect to those of P. clarkii, which alters the relative locations of analogous soma clusters, tracts, bundles, and neuropiles. The major olfactory neuropiles of the central nervous system are the olfactory lobes and the accessory lobes in the brain, and the hemiellipsoid bodies and regions IV of the glomeruli centrales in the medullae terminales. All of these paired regions of neuropile have a glomerular organization. The glomeruli of the olfactory lobe are radially arranged, and each glomerulus is divided into distinguishable regions. The glomeruli of the accessory lobe are smaller and more numerous than those of the olfactory lobe, are spherically shaped, and are organized into three groups within each accessory lobe (this tripartite arrangement is much more obvious in P. argus than in P. clarkii). The medulla terminalis contains 13 distinct neuropile regions, including the hemiellipsoid body and region IV of the glomeruli centrales, both of which are interconnected with the olfactory lobes and accessory lobes via the olfactory-globular tract and contain numerous microglomeruli.
96 citations
TL;DR: The functional anatomy of the male reproductive system and the female spermatheca was investigated using histological methods, transmission and scanning electron microscopic techniques, and microscopic observation of fresh material to elucidate the reproductive characteristics of the Atlantic snow crab Chionoecetes opilio.
Abstract: To help elucidate the reproductive characteristics of the Atlantic snow crab Chionoecetes opilio, the functional anatomy of the male reproductive system and the female spermatheca was investigated using histological methods, transmission and scanning electron microscopic techniques, and microscopic observation of fresh material. Several fundamental corrections and additions to earlier descriptions of spermatozoan structure in C. opilio were made: radial arms are present, while a chromatin ring is not; the acrosome protrudes only slightly and spermatozoa are not mushroom-shaped. The spermatozoa and the matrix of the anterior vas deferens are packed into spermatophores and surrounded by a pellicle which appears to be secreted by the cells lining the anterior vas deferens proximal to the testis. The highly folded configuration of this pellicle may act as a safeguard against dehiscence induced by contact with sea water during copulation. The posterior vas deferens contains two distinct secretions which are probably ejaculated along with the spermatophores and the matrix of the more anterior vas deferens. Anatomical and in vitro observations suggest that fertilization is initiated by exposure of the spermatophores to a hypotonic medium. Such a medium may be generated within the spermathecae by dilution of the seminal fluids/spermatophore storage matrix with sea water prior to egg mass extrusion. Devagination of the liberated spermatozoa may be facilitated by the same mechanism. Most of the females processed for histology had distended spermathecae devoid of spermatophores or spermatozoa. It is thus impossible to deduce successful copulation and spermatophore storage without direct observation of spermathecal contents.
91 citations
TL;DR: A description and definition of the different stages of the molt cycle was developed which included information on the duration of each stage and the implications of the findings to the snow crab.
Abstract: Male snow crabs, Chionoecetes opilio, 67-94 mm carapace width (CW), were held in laboratory conditions over a 6-month period and examined regularly for changes in shell rigidity, shell color, ecdysial suture, setal development, and feeding behavior. Softening and decalcification of the cheliped merus, posterior carapace, and first abdominal segment occurred during premolt. Hardening of these areas and the mouthparts and dorsal carapace together with changes in the ecdysial suture and shell color were useful for defining postmolt stages. Setal changes at the tip of the maxilliped exopodites provided a reliable method for defining premolt stages. Crabs stopped feeding 3-6 weeks before molt and for 3-4 weeks after molt. From these results a description and definition of the different stages of the molt cycle was developed which included information on the duration of each stage. The implications of the findings to the snow crab
83 citations
TL;DR: In this paper, the authors compared the brood weight, fecundity, and egg size as a function of female body size in the deep-sea red crab Geryon quinquedens and the deepsea golden crab geryon fenneri.
Abstract: Brood weight, fecundity, and egg size as a function of female body size were compared in the deep-sea red crab Geryon quinquedens and the deep-sea golden crab Geryon fenneri. Females of G. fenneri attained a larger body size than G. quinquedens, and body size in both species was the main determinant of reproductive output (brood mass) and fecundity per brood. Both species differed from most other brachyurans in having larger reproductive outputs, larger eggs, and lower fecundities relative to their large body sizes. After statistical adjustment for differences in body size between the two species, G. quinquedens had space in the body cavity for yolk accumulation and a brood mass which were 50% larger than G. fenneri. Geryon quinquedens, however, produced eggs 2.18 times the volume of G. fenneri, resulting in equivalent number of eggs per brood in similar-sized crabs. Large, yolky eggs in G. quinquedens are likely to contribute to the nutritional flexibility of its larvae, but apparently have coevolved with significant changes in female morphology and reproductive output.
81 citations
TL;DR: It was observed that SM and BC males are more sexually active than OC males, while the OC males grow more rapidly than SM andBC males, and the changes in specific ratio between the two organs reflect the inverse relationship between reproduction and growth.
Abstract: Adult males of the fresh-water prawn Macrobrachium rosenbergii in a single-age population can be categorized into three morphotypes. Each morphotype represents a different stage in the development of the adult males from small males (SM) through orange-claw (OC) males to blueclaw (BC) males (Cohen et al., 1981; Ra'anan, 1982). All males are capable of developing through all of the above stages, but individual males largely differ in the rate in which they transform from one morphotype to another. It was observed that SM and BC males are more sexually active than OC males, while the OC males grow more rapidly than SM and BC males (Ra'anan and Sagi, 1985). To examine further this behavioral observation, two internal organs in each of the morphotypes were measured and compared. The development of the reproductive system (testes, sperm ducts, and ampullae), as an indication of sexual activity, was compared with the development of the midgut gland (hepatopancreas), an organ which is suggested to be in correlation with somatic growth. The hepatopancreas is significantly larger and the reproductive system is relatively smaller, in relation to body size, in OC males. The opposite is true of SM and BC males, in which the reproductive system is significantly larger while the hepatopancreas is much smaller in relation to body size. Thus, the relative sizes of the two organs of an individual prawn are closely associated with its position in the male developmental pathway from the SM through OC to the BC morphotype. Further, the changes in specific ratio between the two organs reflect the inverse relationship between reproduction and growth.
61 citations
TL;DR: All American species of the Lynceidae Stebbing are redescribed, with two exceptions, and the validity of two species is questioned on the basis of the poor condition of type material and inadequate original descriptions.
Abstract: The North, South, and Central American species of the Lynceidae Stebbing are reviewed. Morphological characters that distinguish the family, including several not previously known or not recognized as being of familial importance, are illustrated and discussed. Of the three known genera in the family, only two, Lynceus Muller and Paralimnetis Gurney, are known from North, Central, and South America; the genus Lynceiopsis Daday, known only from Africa, is described and discussed for comparative purposes. Taxonomic characters that can be reliably used to identify American species are primarily those of the male first thoracopods (claspers) and head region (rostrum). All American species are redescribed, with two exceptions. The validity of two species, Lynceus tropicus and L. rotundirostris. is questioned on the basis of the poor condition of type material and inadequate original descriptions. One new species of Paralimnetis Gurney is described from Texas. A key to the American species is included.
56 citations
TL;DR: Analysis of deep-water female golden crabs collected monthly from the southeastern coast of Florida indicates an annual reproductive cycle with a single batch of eggs produced each year, and changes in gonopore margins associated with molting and the onset of ovarian activity indicate that size at sexual maturity is between 85 and 100 mm CW.
Abstract: Examination of deep-water female golden crabs collected monthly from the southeastern coast of Florida indicates an annual reproductive cycle with a single batch of eggs produced each year. Oviposition begins in late August and continues through October with eggs retained for approximately 6 months until hatching during late February and March. Sizes of ovigerous females examined ranged from 96 to 147 mm carapace width (CW). Extruded eggs averaged 540 μm in diameter, increasing to between 580 and 600 μm prior to hatching. Fecundity estimates range from 131,000 to 347,000 eggs with brood size highly correlated to CW. Changes in gonopore margins associated with molting and the onset of ovarian activity indicate that size at sexual maturity is between 85 and 100 mm CW. Although sampling depth ranges were limited, Geryon fenneri may display similar segregation by sex and size with depth as other species of Geryon.
55 citations
TL;DR: Assortative pairing for body size in pairs was not found, probably because any fitness advantage accruing to males in choosing large females is offset by the costs of longer seeking time and the loss of mating opportunities with smaller females.
Abstract: The distribution of Inachus phalangium (Decapoda: Majidae) on the sea anemone Anemonia sulcata was investigated from 1982 to 1984 in the coastal region of Banyuls-sur-Mer (southern France). Most adult crabs (64.5%) were found alone on an anemone, but groups of 2, 3, and 4 adults sharing an anemone were decreasingly frequent. Spider crabs were randomly distributed on the anemones; 79.5% of the occupied anemones held only one crab. In cases of multiple occupation of a given anemone, (1) heterosexual pairs were more frequent than could be expected for random association, and homosexual pairs less frequent, (2) reproductive males were paired more frequently than expected with females ready to spawn, and (3) adult males pairing with females ready to spawn were larger than solitary males or those males with females not yet ready to spawn. In multiparous females 27% of the variance in the number of eggs per brood was explained by body size; egg number was positively correlated with body size but varied strongly within the same body-size class. Assortative pairing for body size in pairs was not found, probably because any fitness advantage accruing to males in choosing large females is offset by the costs of longer seeking time and the loss of mating opportunities with smaller females.
52 citations
TL;DR: Previous work is reviewed and new observations on the morphology and mechanics of the thoracic endopodites and exopodite of Euphausia superba are presented, which suggest that reconsideration of the biomechanics of filter feeding is in order.
Abstract: Recent observations of "compression filtration" in live euphausiids and unresolved historic controversies about filter feeding in euphausiids based mostly on inferences from preserved specimens suggest that reconsideration of the biomechanics of filter feeding is in order. Explanations of filter feeding in reviews by Mauchline and Fisher (1969) and Mauchline (1980) are incorrect. Here I review previous work and present new observations on the morphology and mechanics of the thoracic endopodites and exopodites of Euphausia superba. Movements of the endopodites are rapid and stereotyped. As the feeding basket expands laterally a pressure gradient is created which sucks water and particles into the basket from the front. Water and particles never enter the basket from the sides, below, or behind. Once inside the feeding basket, particles are retained on the filter and water is squeezed out laterally between the setae. During expansion of the basket the exopodites act as flapper valves which inhibit lateral entry of water, but during the compression stroke the exopodites lift for approximately 100 ms and permit expulsion of water. Comb setae loosen food particles trapped on the filter setae and the tips of the filter setae brush them to the mandibular palps. When phytoplankton is scarce, krill feed steadily with metronomic sweeps of the basket. When phytoplankton is abundant, they exhibit discontinuous feeding patterns. Filter feeding by compression pumping may occur in all those euphausiids that have thoracic appendages like those of E. superba and which filter feed on
TL;DR: Analyses based on criteria for introduced species indicate the four species are introduced in 26 of 27 possible instances and are thus exotic as predicted, and partially corroborate Carlton's thesis that extensive and persistent faunal invasions have occurred in northeast Pacific estuaries.
Abstract: Northeast Pacific estuaries may be severely altered by a broad diversity of accidentally introduced exotic invertebrates (Carlton, 1979a, b, 1987), but few detailed analyses of individual species have been made. The gammaridean amphipods Ampelisca abdita, Melita nitida, Corophium alienense, new species, and Parapleustes derzhavini have previously appeared to be introduced (Carlton, 1979b). However, the specific identities of the last two species and the origins of the last three species have remained unknown. Analyses based on criteria for introduced species, that include evidence from systematics, geography, and ecology, indicate the four species are introduced in 26 of 27 possible instances. They are thus exotic as predicted, and partially corroborate Carlton's thesis that extensive and persistent faunal invasions have occurred in northeast Pacific estuaries.
TL;DR: The study suggested that settled pueruli and juveniles have a diurnal homing ability; they hid in their holes during daytime and emerged at night, then returned to the same holes early next morning.
Abstract: Field surveys were conducted to understand the benthic ecology of the settled puerulus and juvenile stages, up to 23-mm carapace length, of the Japanese spiny lobster Panulirusjaponicus. Both the settled puerulus and juvenile stages were found individually in small holes near algae on the side or underside of rocks or boulders in nearshore shallow waters. The study suggested that settled pueruli and juveniles have a diurnal homing ability; they hid in their holes during daytime and emerged at night, then returned to the same holes early next morning. The first juvenile stage generally continued to occupy the same holes that it used during the puerulus stage, for some period after molting. As juveniles became larger, they moved to larger holes.
TL;DR: The sperm of species of Geryon are typical of brachyurans in having a complex acrosome, a membranous lamellar complex, uncondensed chromatin in the nucleus, and nuclear arms or spikes of varying lengths.
Abstract: The sperm of species of Geryon are typical of brachyurans in having a complex acrosome, a membranous lamellar complex, uncondensed chromatin in the nucleus, and nuclear arms or spikes of varying lengths. There are no microtubular elements in the arms. The spermatophores are ellipsoidal or round and contain varying numbers of sperm. The wall of each spermatophore is two-layered and fairly impermeable to fixatives. Globules of seminal fluid surround the spermatophores in the vasa deferentia. The golden crab Geryonfenneri Manning and Holthuis, 1984, is a nonswimming brachyuran from deep water in the eastern Gulf of Mexico. Relatively little is known about the reproductive biology of the golden crab or a related species, the red crab G. quinquedens Smith, 1879. The golden crab is a recently described species (Manning and Holthuis, 1984) and supports a newly established commercial fishery. Though many studies have been made of the sperm of other brachyurans, no ultrastructural studies have been made of the sperm of the genus Geryon. In this study, the morphological structure of the sperm of G. fenneri and G. quinquedens is examined and compared with that of other crustaceans.
TL;DR: Analysis of monthly quadrat samples taken between November 1985 and December 1986 at Sebastian Inlet, Florida, revealed a variable seasonal abundance of Clibanarius vittatus and spatial distribution of hermit crabs, which significantly reduced the number of amphipods, tanaidaceans, and nemerteans in areas of sea grass and areas of bare sand.
Abstract: Analysis of monthly quadrat samples taken between November 1985 and December 1986 at Sebastian Inlet, Florida, revealed a variable seasonal abundance of Clibanarius vittatus (Bosc, 1802) and spatial distribution of hermit crabs. Mean annual abundance of C. vittatus was 7.7 hermit crabs per m2 with maxima in November (13.9 crabs per m2) and in March (13.8 crabs per m2) and a minimum in January (1.5 crabs per m2). Fine mud and sea-grass habitats appear to be preferred over sandy bottoms. The average sex ratio of females to males was 3.1:1, but January and April samples approached 1:1. Large males (shield length > 10 mm) emigrated during late fall and returned in April, while females and small males remained in the study area. Egg production occurred during April through September, while recruitment of small crabs (SL < 2 mm) into shells began in September and peaked in the winter months. Females tended to have a unimodal size distribution, while males showed a polymodal size distribution with a broader range of size classes. Laboratory experiments showed that C. vittatus significantly reduced the number of amphipods, tanaidaceans, and nemerteans in areas of sea grass, and significantly reduced the number of polychaetes and isopods in areas of bare sand. It is suggested that disturbance of the substratum may explain this reduction.
TL;DR: It is hypothesized that six new species of luminescent myodocopid ostracodes, Vargula psammobia, V. ignitula,V.
Abstract: Six new species of luminescent myodocopid ostracodes, Vargula psammobia, V. ignitula, V. noropsela, V. scintilla, V. micarnacula, and V. lucidella, from the San Bias Islands, Panama, are described. Males of these species secrete pulses of luminescence in species-specific trains in the vicinity of shallow coral reefs at night. These species differ both in bioluminescent signaling patterns and in morphological characters. We hypothesize that these species form a monophyletic group, which we call Group H, and which also includes V. contragula Cohen and Morin, 1986, from the San Bias Islands, and possibly V. tsujii Kornicker and Baker, 1977, from California. We also hypothesize that V. psammobia and V. ignitula are sibling species, as are V. noropsela and V. scintilla. Two keys are given to the eleven known species of Vargula in the San Bias Islands, one based on morphology and the other based on bioluminescent display characters and habitat. Vargula psammobia produces a series of pulses in the shape of an "L," low over sand patches near reefs. Vertical downward displays are produced by V. ignitula, V. scintilla, and V. micamacula. However, they differ in a number of respects including train length and pulse number. Vargula ignitula displays over grass beds, V. scintilla over slopes or patches of coral, and V. micamacula at the edge of reef crests. Vargula lucidella produces vertical upward displays along reef crests. Vargula noropsela generates horizontal to long oblique trains over sand channels in the reef.
TL;DR: The hippolytid shrimps Somersiella sterreri Hart and Manning and Janicea antiguensis (Chace) are recorded from a cave on Cozumel Island, and it is felt to be premature to place them in new taxa.
Abstract: The second known agostocaridid shrimp, Agostocaris bozanici, is described from a cenote on Cozumel Island. The new species is characterized by having a dorsally unarmed rostrum, and 5 pairs of lateral, and 5 pairs of posterior spines on the telson. A new genus and species of hippolytid, Yagerocaris cozumel, is described from a different cenote and an anchialine cave on Cozumel. The genus is characterized primarily by the possession of a very strong pterygostomian spine on the carapace, subequal second pereiopods in which the carpi have 5 articles, a single arthrobranch of maxilliped 3, and a rectangular posterior lobe on the telson. Both shrimps are true anchialines, having been taken from marine-salinity water in cenotes well away from the coast, and both have reduced eyes. The hippolytid shrimps Somersiella sterreri Hart and Manning (previously known only from Bermuda) and Janicea antiguensis (Chace) (previously recorded from Antigua, Bermuda, and the Bahamas) are recorded from a cave on Cozumel Island. While these latter 2 species show some differences from the original descriptions, it is felt to be premature to place them in new taxa.
TL;DR: Keys to identification of all 131 species of Copepoda and 10 species of Branchiura known to parasitize Canadian fishes are provided, with brief descriptions and illustrations of all salient morphological features of each species.
Abstract: KABATA, Z. 1988. Copepoda and Branchiura, p. 3-127. In L. Margolis and Z. Kabata [ed.] Guide to the parasites of fishes of Canada. Part II. Crustacea. Can. Spec. Publ. Fish. Aquat. Sci. 101: 184 p. Keys to identification of all 131 species of Copepoda and 10 species of Branchiura known to parasitize Canadian fishes are provided, with brief descriptions and illustrations of all salient morphological features of each species. An appendix to the Copepoda describes the most common larval stages of these parasites occurring on Canadian fishes. Achtheres corpulentus is transferred to the genus Salmincola and S. extumescens is relegated to synonymy with it. Achtheres micropteri and A. ambloplitis are synonymized with A. pimelodi. Clavella insolita is recognized as a synonym of C. stichaei and a suggestion is put forward that C. pinguis might also be a synonym of that species. Argulus canadensis is tentatively treated as a junior synonym of A. stizostethii.
TL;DR: In the case of Cythere, the diversification of copulatory organs does not seem to reflect taxonomic distance between species because of their function, and the results do not always coincide with their phylogenetic relationship.
Abstract: The male copulatory organs of 10 Recent species of Cythere were compared and the relationship between the copulatory organ and geographic distribution was examined. For 9 pairs of species whose geographic distributions overlap each other, the copulatory organs are morphologically different. Conversely, the pairs of species whose copulatory organs are similar show either of the following characteristics: (1) their distribution areas are completely isolated, or (2) their distribution areas are very close or more or less overlap each other, but their reproductive seasons or their habitats are different. The significant morphologic differences between the copulatory organs of such sympatric pairs are thus interpreted as responsible for mechanical reproductive isolation. Examination of copulatory organs is very useful in ostracod systematics, especially for discrimination of sympatric species. However, the results do not always coincide with their phylogenetic relationship which is well reconstructed from the ontogenetic development of the distribution pattern of normal pores. In the case of Cythere, the diversification of copulatory organs does not seem to reflect taxonomic distance between species because of their function. Finally, geographic variation of the male copulatory organ of Cythere omotenipponicais shown.
TL;DR: Fresh and preserved specimens of Aristaeomorpha foliacea caught in the Sicilian Channel were examined in order to establish a macroscopic scale for the rapid determination of sexual maturity in females with good macro/microscopic agreement.
Abstract: Fresh and preserved specimens of Aristaeomorpha foliacea caught in the Sicilian Channel were examined in order to establish a macroscopic scale for the rapid determination of sexual maturity in females. Four macroscopic criteria were identified as being useful for classification under difficult field conditions. The scale was tested against a microscopic examination of ovarian histological preparations, and corresponding stages were identified on the same specimens with good macro/microscopic agreement. Both procedures were compared to the gonadosomatic index method which, although less practical, may also prove to be a robust indicator of maturity. Practical uses for the proposed scale are given.
TL;DR: Details regarding the nervous system of Crustacea rest heavily on the larger Decapoda, and investigations into the arrangements in all the other groups and of larval stages are few and far between.
Abstract: THE NUMBERS OF NEURONES IN CRUSTACEA Details regarding the nervous system of Crustacea rest heavily on the larger Decapoda. Investigations into the arrangements in all the other groups and of larval stages are few and far between. In many ways this is understandable, for the larger adult decapods are much more amenable to physiological work and it is often studies on function that demand more information on
TL;DR: Comparison of characters considered plesiomorphic reveals that each larval stage can be clearly distinguished from the corresponding stage in P. herbstii s.s. (?) and in the other species.
Abstract: The South American mud crab Panopeus austrobesus was described only recently (Williams, 1983) as one of six distinct species that formerly had been considered local forms of P. herbstii s.l. Milne-Edwards 1834. The larval development in this group of closely related species has been described only in P. herbstii s.s. (or, possibly, P. obesus?) from Beaufort, North Carolina. In the present study, larvae of Brazilian P. austrobesus were reared in the laboratory from hatching to metamorphosis. Development consists of a non-feeding prezoea, four zoea, and one megalopa stage. Duration of each of the zoea stages at 25 °C is 4 to 6 d, and in the megalopa stage about 10 d, i.e. total larval development duration lasts ca. one month. The morphology of the larvae is described and compared with that of larvae of P. herbstii s.s. (?) and of the three Panopeus species, P. americanus, P. occidentalis, and P. bermudensis, that occur on the Brazilian coast and for which descriptions have recently become available. Comparison of characters considered plesiomorphic reveals that each larval stage can be clearly distinguished from the corresponding stage in P. herbstii s.s. (?) and in the other species. Surprisingly, some morphological characters of P. austrobesus larvae show similarity more to P. bermudensis rather than to P. herbstii (?) from Beaufort. Possible relationships among these species are discussed, and an identification key is given for the larval stages of the above mentioned Brazilian Panopeus species.
TL;DR: Results of the current study have shown that several significant characters were either overlooked or misinterpreted in earlier studies of the usefulness of larval characters in determining phylogenetic relationships among species of the hermit crab genus Pagurus.
Abstract: In a continuing study of the usefulness of larval characters in determining phylogenetic relationships among species of the hermit crab genus Pagurus, the developmental sequence of Pagurus hirsutiusculus hirsutiusculus (Dana) has been reexamined using laboratory-reared larvae. Results of the current study have shown that several significant characters were either overlooked or misinterpreted in earlier studies.
TL;DR: Reexamination of a crustacean parasitic on the gills of the scallop Patinopecten yessoensis has revealed that it is a copepod and not, as has been claimed, a rhizocephalan.
Abstract: Reexamination of a crustacean parasitic on the gills of the scallop Patinopecten yessoensis has revealed that it is a copepod and not, as has been claimed, a rhizocephalan. The female is without appendages and its unsegmented, 8-mm broad body presents 1 dorsal unpaired and 2 pairs of lateral peripheral bulges. A small posterodorsal birth pore leads into a capacious brood pouch which is divided into 5 compartments by lateral septa. The mouth occurs in the middle of a circular area which is fused with a conical stalked structure made up of the host's connective tissue. The host's ctenidial epithelium lines the exterior of the stalk as well as the parasite body. The mouth opens into a blood lacuna in the middle of the stalk, and host blood is sucked into the digestive system which, in addition to a much subdivided pharynx, comprises an esophagus and a blind midgut. The female reproductive system consists of a branched ovary, 2 short oviducts, and an unpaired seminal receptacle; cement glands are absent. The males, 1-6 per female, are enclosed within a vesicle connected with the brood pouch; they are ovoid and have minute antennules, antennae, and mandibles placed on a small cephalic prominence. Spermatophores are attached to the inside of the male vesicle from where sperm are transferred to the seminal receptacle. Eggs are incubated in the brood pouch and develop into typical copepod nauplii.
TL;DR: The spiraling swimming behavior exhibited by zoeae of C. nigricauda is not the result of an antagonistic effect of respiratory ventilation currents on swimming speed, Rather, it is a dynamicbehavior exhibited by healthy z Zoeae that probably helps maintain a relatively fixed vertical position in the water column, thereby possibly aiding in escape from predation.
Abstract: Ovigerous females of Crangon nigricauda were captured in Humboldt Bay, California, and their larvae were reared in the laboratory. A larval form intermediate in morphological complexity between previously described zoea V and postlarva was discovered. The new form, an "early megalopa," is described. There are no discrete morphological "stages" in the ontogeny of C. nigricauda after instar III when independence of ecdysis and morphogenesis becomes apparent. Variable larval development of C. nigricauda is discussed in terms of relative maturity of individual larvae of the same age. During development, the natatory exopods of the thoracic appendages gradually degenerate as the pleopods differentiate, resulting in a gradual transition in swimming emphasis: from strictly thoracic (zoeae), to thoracic-abdominal (megalopae), to strictly abdominal (juveniles). The spiraling swimming behavior exhibited by zoeae of C. nigricauda is not the result of an antagonistic effect of respiratory ventilation currents on swimming speed. Rather, it is a dynamic behavior exhibited by healthy zoeae that probably helps maintain a relatively fixed vertical position in the water column, thereby possibly aiding in escape from predation.
TL;DR: A new genus and species of copepod, Norkus cladocephalus (Siphonostomatoida: Sphyriidae), is described from specimens collected from the hemibranchs of the shovelnose guitarfish Rhinobatos productus from southern California.
Abstract: A new genus and species of copepod, Norkus cladocephalus (Siphonostomatoida: Sphyriidae), is described from specimens collected from the hemibranchs of the shovelnose guitarfish Rhinobatos productus (Ayres) from southern California. The new genus is distinguished from confamilial genera by the presence of (1) an elaborately branched holdfast on the cephalothorax, (2) an expanded collar on the anterior end of the neck, (3) a dorsoventrally flattened discoid trunk, and (4) simple, cylindrical posterior processes (modified caudal rami). A phylogenetic analysis of the Sphyriidae, using the lernaeopodid genus Ommatokoita as the outgroup, was conducted. A single parasite cladogram and host summary and ecological summary cladograms are presented and discussed.