Malacostraca Research Articles

Molecular phylogeny of the major arthropod groups indicates polyphyly of crustaceans and a new hypothesis for the origin of hexapods.

A phylogeny of the arthropods was inferred from analyses of amino acid sequences derived from the nuclear genes encoding elongation factor-1 alpha and the largest subunit of RNA polymerase II using maximum-parsimony, neighbor-joining, and maximum-likelihood methods. Analyses of elongation factor-1 alpha from 17 arthropods and 4 outgroup taxa recovered many arthropod clades supported by previous morphological studies, including Diplopoda, Myriapoda, Insecta, Hexapoda, Branchiopoda (Crustacea), Araneae, Tetrapulmonata, Arachnida, Chelicerata, and Malacostraca (Crustacea). However, counter to previous studies, elongation factor-1 alpha placed Malacostraca as sister group to the other arthropods. Branchiopod crustaceans were found to be more closely related to hexapods and myriapods than to malacostracan crustaceans. Sequences for RNA polymerase II were obtained from 11 arthropod taxa and were analyzed separately and in combination with elongation factor-1 alpha. Results from these analyses were concordant with those derived from elongation factor-1 alpha alone and provided support for a Hexapoda/Branchiopoda clade, thus arguing against the monophyly of the traditionally defined Atelocerata (Hexapoda + Myriapoda).

PHYLOGENETIC ANALYSIS OF THE STOMATOPODA (MALACOSTRACA)

ABSTRACT The stomatopods or mantis shrimps are malacostracan crustaceans of the subclass Hoplocarida. All extant hoplocarids belong to the order Stomatopoda and suborder Unipeltata. The Unipeltata comprises the extinct, stem-lineage sculdids, and the crown-group which includes the 19 extant families with more than 400 species. A cladistic analysis of all 20 families of the Unipeltata, rooted with four fossil outgroups, resulted in a single, fully resolved topology. The results largely support the existing five-superfamily classification. The Squilloidea, not the Bathysquilloidea, were the earliest derived crown-group superfamily. The Lysiosquilloidea and Erythrosquilloidea are derived as sister groups, which together are sister to the gonodactyloids. The Bathysquilloidea and Gonodactyloidea, however, were not monophyletic, supporting the erection of new superfamilies for the extinct Sculdidae and the extant Parasquillidae. The Bathysquilloidea is restricted to the Bathysquillidae and Indosquillidae, but, owing to incomplete fossil data, a new taxon is not erected for the sculdids. Instead, the Sculdidae is considered incertae sedis until more fossil data become available. The superfamilial affiliation of the Parasquillidae is also considered uncertain pending further research. Monophyly of the Heterosquillidae sensu Manning (1995) was unsupported. Paracoridon, presently a heterosquillid, is transferred to the Coronididae. Further study of coronidid relationships is necessary and may support the removal of both Acoridon and Paracoridon. The Tetrasquillidae and Heterosquillidae, as restricted here, are recognized as sister taxa, but further study may require their synonymy. Characters based on the modified male first pleopod are informative at superfamily level and further study may reveal characters useful down to the specific level.

Variations on a segmental theme: muscle receptor organs and extensor neuromusculature in the squat lobster Munida quadrispina (Anomura, Galatheidae)

Extensor neuromusculature and the muscle receptor organs (MROs) associated with them have been conserved during the evolution of malacostracan crustaceans, despite species-specific differences between homologous segments in divergent taxa. Investigations of these differences could provide insight into how sensory and neuromuscular elements are modified to accommodate changing behavioural patterns. The most obvious differences between squat lobsters (galatheid anomurans) and macruran decapods, such as crayfish, are the greater dorso-ventral flattening of the galatheid abdomen and its flexed resting posture. To investigate whether the evolution of this altered posture affected extensor neuromusculature and MRO morphology and physiology, we used Methylene Blue staining, cobalt backfilling and extracellular recording techniques to describe these elements in the caudal thoracic and six abdominal segments of the squat lobster Munida quadrispina and compared our results with published descriptions of homologous elements in macrurans. In M. quadrispina, there is segmental variation both in the orientation of the MROs along the abdomen and in their physiological responses to stretch: apparent sensitivity is higher in caudal than rostral MROs. Homologues of three of the four accessory neurones found in crayfish occur, but AN#1 has a major dendrite not present in crayfish. Intersegmental differences in size and morphology of extensor motoneurones occur in M. quadrispina, as have been reported in crayfish, but are dissimilar in the two: abdominal ganglion 5 extensor motoneurones are the largest in M. quadrispina and the smallest in crayfish; this difference correlates with the difference in relative size of axial muscles along the abdomen reported previously for these species. M. quadrispina also differs from macrurans in having a single tonic, and no phasic, MRO on each side of the last abdominal segment. Together, these observations suggest that galatheids have evolved modified or additional neurobehavioural control(s) for the abdomen and tailfan.

Serotonin immunoreactivity in the ventral nerve cord of the primitive crustacean Anaspides tasmaniae closely resembles that of crayfish

Syncarid crustaceans, of which only a few living species remain, have articulated segments with well-developed appendages along the length of the body, an arrangement thought to resemble that of the earliest malacostracan crustaceans. Decapod malacostracans have fused thoracic segments and reduced abdominal appendages. Modern representatives of the two groups are separated by at least 300 million years of evolutionary history. The serotonin immunoreactivity of ganglia and connectives from the ventral nerve cord of the syncarid Anaspides tasmaniae was compared with that of serially homologous ganglia of the crayfish Cherax destructor. Both species show the serotonin-immunoreactive longitudinal fibre bundles described from other decapods and thought to be part of a neuromodulatory network. They also have in common a number of the cell bodies associated with this system. Each species has some serotonergic cells in the region examined that are not present, or that do not stain, in the other species.

Molecular systematics in the acanthocephalan genus Echinorhynchus (sensu lato) in northern Europe.

New biological species and high levels of inter- and intraspecific genetic divergence were discovered in an allozyme study of some North European members of the acanthocephalan genus Echinorhynchus (sensu lato), parasites of fish and malacostracan crustaceans. (i) A strong differentiation between the marine E. gadi and the fresh- and brackish-water E. salmonis (genetic identity I congruent to 0) supports a generic distinction between these taxa; however, the subdivision would not entirely concur with the concepts of Echinorhynchus (sensu stricto) and Metechinorhynchus suggested earlier. (ii) Samples of E. gadi from the Baltic, Norwegian and North Seas included three distinct, partially sympatric biological species (spp. I-III; I congruent to 0.5). (iii) E. bothniensis, previously only known from the northern Baltic Sea, represents a complex of freshwater taxa with an intermediate host relationship to the 'glacial relict' Mysis spp. and with a distributional and host analogy to the North American E. leidyi. A population in a northern lake in the Barents Sea basin is closely related to E. bothniensis of the Baltic area, but is probably specifically distinct; the divergence between these populations (I congruent to 0.6) is similar to that between their Mysis host species. (iv) Considerable intraspecific differentiation (FST = 0.25), probably reflecting post-glacial population bottlenecks, was found between Baltic and nearby lacustrine E. bothniensis, and between Atlantic and Baltic E. gadi sp. I.

Aspects of Malacostracan Evolution

AbstractThe outstanding success of the Crustacea Malacostraca is largely due to the tagmatization of the malacostracan body and its appendages, which has permitted the evolution of a wide spectrum of adaptations, particularly within caridoid taxa with series of specialized appendages. Non‐caridoid ancestral malacostracans have not materialized, and recent proposals by Schram (Schram, F. R. 1986. Crustacea), according to which the Phyllocarida should be removed from the Malacostraca and transferred to a re‐defined class Phyllopoda, was found to be built upon false premises. Manton (Manton, S. M. 1953.—Symposia of the Society for Experimental Biology 7: 339–376), discussing a hypothetical malacostracan ancestor, was of the opinion that in such an ancestor walking preceded swimming, an opinion which has received considerable support. This also implies that the Malacostraca were originally epibenthic, retaining a number of primitive features. The hypothetical ‘generalized malacostracan’ envisaged by Calman (Calman, W. T. 1909. A treatise on zoology, Part 7, pp. 1–346) was also presumed to be epibenthic, representing what Calman called a caridoid facies, thereby emphasizing an important aspect of the eumalacostracan structural and functional plan.

SENSORY MORPHOLOGY IN THE ANTENNAE OF THE CEPHALOCARID HUTCHINSONIELLA MACRACANTHA

The first antenna of Hutchinsoniella macracantha is a 6-segmented, uniramous appendage carrying 1 aesthetasc and 22 setae (or sensilla). The second antenna is biramous and has approximately 80 setae. The sensory cells of the first antenna are arranged in 3 clusters in the first and second segments; one cluster serving the aesthetasc (approximately 130 cells), one the 11 setae of the sixth segment (approximately 100), and one the remaining setae (approximately 80). The sensory cells of the second antenna are distributed in a medial band along the length of the antenna. The sensory cells of the aesthetasc have 1 cilium each which splits into many branches. The sensory cells of the setae have 1 unbranched cilium each, and the number of sensory cells varies for each seta. The aesthetasc is a presumed olfactory organ, and all setae display features suggesting chemoreception. The aesthetasc combines malacostracan and nonmalacostracan features, whereas the setae conform to a general crustacean pattern. (Less)

Crustacean olfaction: The daphnid aesthetascs lead to a changed structural concept

Aesthetascs situated on the first antennae of crustaceans are easily recognized and distinguished from other sensilla by their hose-like appearance and thin cuticle. Their internal structure is known from decapod, mysid and isopod, i.e. malacostracan crustaceans. The aesthetasc is characterized in these animals by a large number of sensory neurons below each single aesthetasc. The neurons give rise to - from their dendrites - two cilia. The cilia protrude into the external hose-like portion of the aesthetasc splitting up into many branches. It is generally agreed that the aesthetascs are the structural base for crustacean olfaction and experiments to verify this have been performed mostly on malacostracan species.The water-flea, Daphnia, is a non-malacostracan species. It has greatly reduced first antennae and externally only nine pairs of aesthetascs remain (Figs 1, 2). The outer morphology agrees with that of malacostracan species. The internal morphology does not. Each of these aesthetascs has only four sensory cells situated deep inside the animal. The sensory cells have only one cilium (Fig. 3) extending unbranched into the external portion of the aesthetasc (Fig. 4).

Central Nervous System of Hutchinsoniella Macracantha (Cephalocarida)

The central nervous system of the cephalocarid Hutchinsoniella macracantha is well developed, although missing several structures which are characteristic of the general crustacean plan. There are no signs of eyes either in the adult or in the larva. The organ of Bellonci, central body, protocerebral bridge, and paracentral lobes are absent. The mushroom bodies occur in the central nervous system in a form different from that found in malacostracan crustaceans and are unexpectedly well developed. They are connected to the olfactory lobes, which in this species are displaced ventrally into the clypeus (anterior part of the so-called labrum), extremely large, and of hitherto unseen construction. The central nervous system of Hutchinsoniella does not conform to a paradigm of overall primitiveness and must have evolved separately in the cephalocarid line for a long period.

Stygofauna of the Canary Islands, 23. A freshwater amphipod from La Gomera, Melita dulcicola n.sp.

Description of a new species of Melita, M. dulcicola n.sp. (Amphipoda), discovered in a well fed by fresh ground water on the island of La Gomera in the Canary archipelago. This is the third limnic, oculate malacostracan crustacean becoming known from the Canary Islands, and it is the third species of Melita (with world-wide over 65 marine or brackishwater species) recorded from fresh waters.

Environmental controls on the taphonomy and distribution of Carboniferous malacostracan crustaceans

ABSTRACTShrimp-like malacostracan crustaceans first appeared in the late Devonian and underwent a substantial adaptive radiation in the Carboniferous. They are rarely found in rocks of fully marine origin but are well represented in sediments laid down in brackish water and marginal marine conditions; such transitional environments provide the exceptional circumstances required for the preservation of unmineralised shrimps. The best examples are in the Dinantian of Scotland, the Namurian of Montana, and the Westphalian of Illinois. It is probable that shrimps were widespread in contemporaneous marine environments, but are not preserved.Any approach to understanding the physiology of fossil organisms is necessarily indirect. The diversity of crustacean communities, and the nature of associated taxa and trace fossils, are the most useful biotic factors for interpreting the habitat and tolerance of fossil examples.All known Carboniferous crustacean communities lived in brackish conditions; none is fully marine. Malacostracan assemblages in the Dinantian of Britain show a general trend of increasing diversity with salinity, from a single taxon at Gullane (stratified freshwater lake or brackish lagoon) to ten at Glencartholm (approaching normal marine).Tealliocarisis associated with low salinities.Crangopsis socialisis confined to the brackish water interdistributary bay environment, butBairdopsandBelotelsondisplay a broader environmental tolerance.Crangopsis eskdalensis, Sairocaris, andPerimecturusoccur only at Glencartholm, indicating a requirement for a strong marine influence. Those taxa confined to a limited environmental range all occur where a marine influence is pronounced; none occurs solely in areas of lower salinity. While salinity was apparently the dominant influence on distribution, a complex of independently varying environmental factors was involved. The range of habitats colonised early in the Carboniferous indicates that the preserved taxa had already developed advanced osmoregulatory mechanisms.

Absence of Epicuticle from the Repair Cuticle Produced by Four Malacostracan Crustaceans

Absence of Epicuticle from the Repair Cuticle Produced by Four Malacostracan Crustaceans

ABSENCE OF EPICUTICLE FROM THE REPAIR CUTICLE PRODUCED BY FOUR MALACOSTRACAN CRUSTACEANS

ABSTRACT Small lesions were made in the integument of Cambarus bartonii, Crangon septemspinosa, Gammarus oceanicus, and Idotea baltica. Examination by light and transmission electron microscopy of tissue removed at several intervals up to 8 weeks after injury demonstrated that all species produced repair cuticle across the wound. While there were differences in the organization of this material in the four species, none of the repair cuticles contained an epicuticle. These observations, together with others reported in the literature for Crustacea and other arthropods, suggest that the absence of epicuticle is a general property of arthropod repair cuticle.

Feeding patterns of Nesogobius sp., Gymnapistes marmoratus, Neoodax balteatus and Acanthaluteres spilomelanurus from a Tasmanian seagrass meadow

The diet, feeding chronologies, gastric evacuation rates and daily ration of four species of fish from a seagrass meadow in south-eastern Tasmania were determined by field and laboratory studies. Nesogobius sp. is an active species feeding mainly as intertidal regions are flooded and taking predominantly errant polychaetes and amphipods. G. marmoratus feeds continuously, mainly on malacostracan crustaceans. N.balteatus and A. spilomelanurus both feed only during the daylight hours; the former feeds mainly on slow-moving and benthic animals and some zooplankton whereas plant material and zooplankton are important in the diet of the latter. The gastric evacuation rate and daily lation are lowest in G, marmoratus. N. balteatus and A. spilomelanurus have high evacuation rates and, together with Nesogobius sp., high daily rations. These differences are probably due to the proportion of time spent feeding, the quality of the dietary items, and activity patterns.

Introduction to the palaeontology of the Dinantian of Foulden, Berwickshire, Scotland

ABSTRACTThe Foulden Site of Special Scientific Interest is one of the few Cementstone Group localities that yields significant fauna and flora. Excavations in 1980 and 1981 removed a 1·3 m2 slab of the Fish Bed for laboratory study of the vertical and spatial distribution of the biota. Layer by layer analysis revealed an almost mutually exclusive relationship between the vertical distribution of the palaeoniscoid fishes and malacostracan crustaceans, as well as a horizon crowded with juvenile acanthodians. Elongate elements of this biota showed slight preferred orientations at that prolific horizon. Some 27 m of strata including the Fish Bed, Plant Bed and Shell Bed are recorded in detail, and their biota noted. Interim results of work on the main groups collected are summarised in associated papers in this part of Transactions. Brief reports are given here on the euryhaline marine bivalve mollusc Modiolus latus (Portlock), a rare durophagous bradyodont shark tooth and an Eogyrinus-like amphibian scute.

On the Classification of Eumalacostraca

Traditional views of phylogeny are not in accord with current understanding of the fossil record. Another approach results from identification of basic morphotypes upon which radiations were built in the course of history. Random association of characters (absence or varying conditions of the carapace, biramous or uniramous thoracopods, and presence or absence of subthoracic brood pouch of some form) yields an array of 16 morphotypes, of which 10 are recognized in the fossil and Recent record. The resultant paper animals combined with an analysis by cladistic methods yield six possible phenograms of phylogeny. An evolutionary uncertainty principle precludes definitive choice among these patterns to produce a cladogram and taxonomy. However, a taxonomic system is advocated with the subjectivity associated with uncertainty clearly acknowledged. Perhaps one of the greatest noncontroversies in crustacean evolution has been the phylogeny and interrelationships of the Eumalacostraca. Since Calman (1904, 1909) it has been taken for granted that the higher malacostracans could be classified as discreet superorders which were derived from an ancestral type neatly delineated by a set of characters known as the caridoid facies. However, Calman's synthesis was the result of several decades of debate over how malacostracan groups were related. Boas (1883) visualized a single line arising from the phyllopods and giving off the malacostracan groups at successive levels. Claus (1885) envisioned three branches arising from a eumalacostracan stock: leptostracans, stomatopods, and urschizopods, and this was essentially Grobben's (1892) position as well, except that Grobben had the stomatopods as the earliest offshoot from the urschizopods.' Haeckel (1896) derived his proschizopods from the Leptostraca and in turn treated these as an ancestral stock for five lines: mysids, cumaceans, other eucarids, and stomatopods. Calman's caridoid concept, however, exerted a stablizing influence on all succeeding speculations on higher malacostracan phylogeny, with the result that subsequent phyletic schemes for these groups have been essentially similar (Giesbrecht, 1913; Grobben, 1919; Balss, 1938; Siewing, 1956, 1963; and Brooks, 1962). Of these, Siewing came to be a focus of a certain school (viz., Fryer, 1964; Hessler, 1969) which essentially holds that all superorders arose from a central stem. Schram (1969a, b) recently suggested that the Hoplocarida had nothing to do with other Eumalacostraca, but rather had an independent origin separate from the Eumalacostraca sensu stricto. This latter position was objected to by Burnett and Hessler (1973) but supported by Reaka (1975), Bowman and Abele (in press), and Kunze (personal communication). Through all this, the essential stability and supposed interrelationships of the Eumalacostraca sensu stricto, viz., syncarids, eocarids, peracarids, pancarids, and eucarids has remained relatively constant. The Eocarida and Syncarida were interpreted as near the base of the line; and supposedly from somewhere within the eocaridan stock the Eucarida and Peracarida were derived, with the Pancarida seeming to bear some relationships to peracarids (some authors placing them as a separate superorder and others as an order of peracarids). This traditional arrangement of orders is outlined in Fig. 1.

Eyes and classification of malacostracan crustaceans

During the past 100 yr various methods of classifying mysids, krill, prawns, shrimps, crabs and lobsters have been proposed, including the use of behaviour, gill type and the relationship of the carapace with the head and the thoracic segments. At least two factors have been ignored in all these schemes—larval characters and optical mechanisms. A survey of malacostracan crustaceans reveals three types of optical mechanism. The simplest uses apposition optics, often with hexagonal facets, and is found in all decapod larvae and most adult brachyuran crabs. Refracting, superposition eyes with hexagonal facets occur in mysids and euphausids, and reflecting, superposition eyes with square facets using mirror optics are found in adult prawns, shrimps, macrurans such as lobsters, and dromiid ‘crabs’. Artificial relationships have been imposed on malacostracan crustaceans by a failure to incorporate eye structure in schemes of classification. Once evolved, eye structure is a stable character and provides evidence for the continued grouping together of penaeid, caridean and stenopid prawns and shrimps; it demonstrates their affinity with lobsters and other Macrura, and confirms the unity of a re-defined Brachyura and the weakness of the Anomura as a coherent taxon.

Paleozoogeography of Late Paleozoic and Triassic Malacostraca

Paleozoogeography of Late Paleozoic and Triassic Malacostraca

Rhabdom Adaptation and Its Phylogenetic Significance

AbstractElofsson, R. (Zoological Institute, University of Lund, S‐223 62 Lund, Sweden.) Rhabdom adaptation and its phylogenetic significance. Zool. Scr. 5 (3–4): 97–101, 1976. — The rhabdoms of arthropod compound eyes are structurally differentiated into open, fused layered, and fused continuous. All are capable of perceiving polarized light. The fused layered, and under certain conditions the fused continuous, perform particularly well. — The fused layered rhabdoms occur in malacostracan crustaceans and in various insect groups. This, together with, among other things, the presence of open rhabdoms in insects and crustaceans, indicates convergent development of organs and parts of organs. — Elaborate visual organs of more than one kind occur in crustaceans, as is exemplified by the compound and nauplius eyes. This shows that more than one construction on the organ level is possible in a restricted taxo‐nomical unit for the. perception of light. The different rhabdom types performing well in receiving polarized light also show parallel evolution on a level below the organ. — The result of adaptation analyses indicates the need for a restricted use of the concept of homology basic to morphological investigations and a base for phylogenetic speculations. It also envisages a fruitful approach to a peep into the workshop of evolution. — It is concluded that a fully formed compound eye in arthropod ancestors is hardly conceivable. A realistic alternative is an inherent capacity of forming a compound eye. Thus the ancestral compound eye could have ranged from nothing to a partly‐developed stage. The recent eyes need not originate from one source.

Monoaminergic neurons in the nervous system of crustaceans.

Certain neurons in the nervous system of the malacostracan crustaceans give rise to a predominantly green and a sparse yellow fluorophore in the histochemical fluorescence method of Falck-Hillarp. The same applies to the whole of Crustacea. The green fluorophore is probably a catecholamine; the yellow to brown-yellow has not yet been identified. The biogenic amine responsible for the green fluorescence, besides being found in diffusely distributed fibres, also appears in distinct areas of fibre concentrations in the central nervous system. The protocerebrum of the malacostracans contains three areas: the central body and two areas in the top of the brain, one anterior and one posterior. The latter two are not recognized as separate areas in ordinary histological preparations. In addition, the optic neuropiles are fluorescent, some with a distinct stratification of the fluorophore. The deuto- and tritocerebrum and the ventral nerve cord also contain monoaminergic neurons. Of the brightly fluorescent areas in the whole of Crustacea, only the central body consistently exists in all species. The other areas of concentrated fluorescent neuropile are restricted to smaller taxonomic units and differ from each other.