Growth ‘rules’ and the larvae of decapod crustaceans

Summary

Statements that have attempted to express the relationship between the sizes of successive arthropodan instars are examined with reference to published data on larval decapod crustaceans.

The conclusions reached are (a) that ‘Brooks's Law’, which simply states that the lengths of successive instars form an exponential series, generally holds good in decapod larvae, (b) that ‘Przibram's Rule’, stating that the weight increase between instars is always by some power of 2, is not supported by the observed length changes, and (c) that Gurney's suggestion that growth factors in decapod larvae do not normally exceed about 1·5 is not applicable to the order as a whole, but may be valid for some sub-groups within it.     

Ciliate—decapod epibiosis in two areas of the north-west Mediterranean coast

A study was carried out of the protozoan ciliate epibionts present on diverse decapod crustaceans from two areas of the north-west Mediterranean. A total of 92 crustaceans was examined (65 brachyurans and 27 anomurans, belonging to 15 species). Seventeen ciliate species were identified (two heterotrichs, two chonotrichs, ten suctorians, and three peritrichs). This is the first record of the family of folliculinid ciliates as epibiont on crustaceans in Mediterranean waters. The suctorian Acinetides symbiotica, considered endemic to Lake Nyassa, was found in the sampling areas. Local variations, microlocation on the surface and anatomical units of the decapods, and differential distribution of epibionts were also considered.     

Microscopic morphology of the antennule and antenna of the marine isopod Cirolana harfordi

ABSTRACT

The use of scanning electron microscopy on the cuticle outgrowths called setae (that contain sensilla) in crustaceans is useful for, understanding how crustacean species sense their environment and for taxonomic studies. So far, most of the setal morphology studies have been performed on decapod crustaceans such as lobsters and shrimps and there has been a comparative lack of such research on marine isopods, from which terrestrial isopods such as woodlice or slaters have evolved. In the current study, electron microscopy was used to study the antennal setae of the marine isopod Cirolana harfordi using magnification powers of up to 40, 000. C. harfordi displayed a number of setal types including setae that had a sub-terminal pore that contained a cupule-shaped structure and plumose setae which are pennate in structure and have two rows of setules along the setal shaft in a fashion analogous to a palm leaf. These plumose setae may be useful to the animal in detecting water currents. Differences in the structure and placement of setae on the antennae of C. harfordi as compared to two other marine isopods, Bathynomus pelor and Natatolana borealis (that have had a comprehensive study of antennae setal morphology performed on them in previous studies) indicate that scanning electron microscopy of isopod setae may be useful in taxonomic studies of isopods.     

Abundance and diversity of decapod crustaceans in the deep-Catalan Sea (Western Mediterranean)

The deep-slope decapod fauna of the Catalan Sea was extensively sampled with an OTSB-14 bottom trawl. A total of 67 bottom tows were taken from 1985 to 1989 at bottom depths ranging from 552 to 2261 m. Species in which abundance decreased with depth were Plesionika acanthonotus, Polycheles typhlops, Calocaris macandreae and Geryon longipes. Highest densities of Acanthephyra eximia, Stereomastis sculpta, and Nematocarcinus exilis were attained at the greatest depths studied. Total abundance, biomass and species richness for decapod crustaceans as a whole decreased with depth. Maximum decapod biomass and diversity occurred on the upper-middle slope on soft bottoms in the Catalan Sea and in all regions for which data were available. In the Catalan Sea, an oligotrophic area, the abundance of decapods as a group seemed to be higher than in north-Atlantic eutrophic regions. In these latter areas, other deep-sea benthic invertebrate groups, particularly ophiuroids, predominate.     

II.—Notes on some Australian Polyzoa

Forty-one species of 20 families of fishes were observed being cleaned at Bonaire by two species of decapod crustaceans and four species of fishes. Of 525 observations of fishes being cleaned (clients), over 60% involved species of the Serranidae, Scaridae and one species of Pomacentridae (Chromis multilineata). Gobies (Gobiosoma spp.) and Pederson's cleaner shrimp (Periclimenes pedersoni) were the most frequent cleaners of all three groups of clients. Only P. pedersoni performed a display that may have attracted clients. Cleaner species except Thalassoma bifasciatum cleaned the mouth and gills of clients, as well as the rest of the body. Clients approached cleaners, presented part of their body to the cleaner, opened their mouth or flared their gills, remained relatively motionless, and then twitched their tail and body and swam away. Unlike other clients, species of the Serranidae rarely assumed a vertical posture during cleaning. Chromis spp. and Clepticus parrai formed tight ball-like formations around cleaners. The behaviour of cleaner fishes and shrimp at Bonaire was more similar to that reported for eastern Pacific species than that of Labroides spp. of the Indo-Pacific area.     

Morphology of the alimentary tract in relation to diet among gobioid fishes

Summary

The morphology and general course of the alimentary canal, the relative length, number and morphology of the gill rakers, and the pattern of the buccal and pharyngeal dentition in 20 species of gobioids belonging to 3 families are studied. The food of the species studied is analysed from gut contents. Depending on the predominance of different food items in the gut the fishes can be categorized into herbivores feeding on algae, omnivores on algae, crustaceans or fish any of which may be dominant and detritivores on soft benthic ooze. The morphology of the alimentary canal, the R.L.G., the morphology of the gill rakers and the pattern of buccal and pharyngeal dentition are found to be related to the food of the fishes.     

Studies on gorgoderid digeneans from Australian and Assian Freshwater fishes

Pseudophyllodistomum gen. nov. is proposed for a section of Phyllodistomum Braun, 1899. The new genus is distinguished by the simple form of the uterus, the eggs which reach over 60 μm long in length, the saccular excretory bladder, the 2[3 + 3 + 3) + (3 + 3 + 3)] = 36 flame-cell formula, the metacercaria which may have fully developed genitalia and is parasitic in decapod crustaceans, the use of corbiculid bivalves as first intermediate hosts, and the cercaria which has a long tail not enclosing the cercarial body. Two species, P. johnstoni sp. nov. and P. murrayense sp. nov., are described from Australian freshwater fish and five new combinations of previously described Phyllodistomum species from Asian freshwater fish are proposed — P. macrobrachicola (Yamaguti, 1934) comb. nov., P. lesteri (Wu, 1938) comb. nov., P. srivastavai (Rai, 1964) comb. nov., P. lucknowense (Pandey, 1970) comb. nov. and P. mingense (Tang, 1985) comb. nov. The first intermediate host of P. johnstoni is a Corbiculina species. The long-tailed cercariae infect the gonads of palaemonid prawns, Macrobrachium spp., in which they grow to unencysted metacercariae which may have fully developed genitalia. The metacercaria of P. murrayense also infects a Macrobrachium species. The evolution of the Gorgoderinae is discussed and it is suggested that, prior to the erection of Pseudophyllodistomum, Phyllodistomum may have encompassed as many as five different phylogenetic lines, each with similar adult morphology but distinguishable by life-cycle characters. It is postulated that more study will lead to further division of Phyllodistomum.     

Crustaceans associated with the deep-water gorgonian corals Paragorgia arborea (L., 1758) and Primnoa resedaeformis (Gunn., 1763)

To explore the crustacean fauna associated with deep-water gorgonian corals, suction samples were taken from colonies of Paragorgia arborea and Primnoa resedaeformis using a Remotely Operated Vehicle. Seven colonies of P. arborea and eight of P. resedaeformis were sampled from 330–500?m depth in the Northeast Channel off Nova Scotia. A total of 17 species were identified as being associated with the corals. The P. arborea fauna was richer than the P. resedaeformis fauna in both abundance and number of species, with 1303 versus 102 individuals and 16 versus seven species, respectively. However, 13 of the species associated with P. arborea were from hydroids attached to the coral. Amphipods dominated the fauna both in abundance and numbers of species and the most common species were Metopa bruzelii, Stenopleustes malmgreni, Proboloides calcarata and Aeginella spinosa. The isopod Munna boecki and the cirripede Ornatoscalpellum stroemii were also quite common. The most strongly associated crustaceans were two parasitic poecilostomatid copepods; these are common also on tropical gorgonians and are most likely obligate associates. The frequently occurring shrimp Pandalus propinquus probably avoids predation by seeking protection among the coral branches. Shrimp counts from video records showed that visual inspection without physically disturbing colonies will generally not reveal the crustaceans hidden in coral colonies. The galatheid Eumunida picta was observed on P. resedaeformis colonies. The fauna of the deep-water gorgonians corresponded to the fauna of tropical shallow-water gorgonians in the numerical dominance of amphipods and parasitic copepods; however, species richness is higher and decapods, which constitute a rich fauna on tropical gorgonians, were only represented by two species.     

An unusual song-pattern in the Chorthippus mollis group (Orthoptera: Acrididae): local variant or hybrid population?

Summary

Published accounts of geographical variation in the songs of Orthoptera are briefly reviewed. An unusual song-pattern produced by an isolated alpine population of a grasshopper belonging to the Chorthippus mollis group is described and illustrated with oscillograms. Both the song and morphological characters of this population are compared with those of typical C. mollis and C. biguttulus. The status of the population is discussed and it is concluded that the balance of evidence favours the hypothesis that it is a hybrid population resulting from a cross between these two species.     

XXX.—On tertiary transarctic brachiopod migration

Abstract

Of brachiopod species previously considered to illustrate late-Tertiary transarctic migration, it is concluded from the evidence of recent and fossil distribution that Hemithyris psittacea (Gmelin) and Glaciarcula gen. nov., are true transarctic forms, Dallina and Macandrevia are doubtfully so, and Tegulorhynchia is not.     

Studies on the Indian species of the genus Coccophagus Westwood, 1883

Summary

Two species of muntjac deer, the Indian and the Reeves', were introduced into England in the nineteenth and the present centuries. Feral muntjac deer now occur widely over the southern half of England. Their identity, however, is uncertain with claims being made for both species and for hybrids. Skulls and jaws of the two species of muntjac deer from their native countries and from feral animals from eight counties in England have been examined. From these measurements and from chromosome studies it is concluded that the feral muntjac deer in England are Reeves' muntjac. No evidence has been found to substantiate claims for the presence of either the Indian muntjac or hybrids.     

The prey and predators of Homalopsine snakes

The diets of all South-East Asian water snakes of the subfamily Homalopsinae are reviewed. New diet observations for 10 species of homalopsine snakes are presented. The data on four of these, Cantoria violacea, Enhydris doriea, E. longicauda and Gerarda prevostina represent the first published diet records for these species. The observations for Fordonia leucobalia, Myron richardsonii andEnhydris enhydris represent the first taxonomically detailed diet records for these three species. The records provided for Cerberus rynchops, Enhydris plumbea and Homalopsis buccata add new taxonomic categories to previous records. The records provided for Cerberus rynchops, E. plumbea and Homalopsis buccata add new taxonomic categories to previous records. Four generalities emerge from our findings: (1) freshwater homalopsines feed primarily on fish and the adults and larvae of amphibians; (2) at least four of the eight estuarial species specialize on crustaceans while two primarily prey on fish; (3) feeding on crustaceans appears to have evolved independently at least twice; (4) prey are usually less than 10% of the predator's mass. The known predators of homalopsines are summarized and include both invertebrates and vertebrates. The microhabitats of the estuarial species are discussed and related to prey and habitat preferences.     

The cuticle of two species of Bothrodendron [Lycopsida: Lepidodendrales]

Summary

The variability of four characters commonly used in the separation of species of Limnodrilus has been described, and their relative values assessed. The number of setae per bundle is useless as a specific character; the shape of the setae can serve to distinguish only a single species and the length: breadth ratio of the penial sheath is more useful as an additional or confirmatory character. The shape of the penial sheath proved to be the most important character, but even this was not completely reliable, and it is concluded that several characters must be used in the identification of species of Limnodrilus. It is suggested that structures other than the cuticular derivatives should be examined and that a similar study be carried out on North American species.     

The taxonomic position of Alma worthingtoni Stephenson

Summary

1. 1. Alma worthingtoni is compared with A. emini from a taxonomic point of view.

2. 2. The size of the type specimen of A. worthingtoni falls well within the range for A. emini.

3. 3. The character of the body chaetæ as well as the chaetal distances is the same in both species.

4. 4. The internal anatomy in both species is the same. The absence of spermathecae in Alma worthingtoni is explained.

5. 5. The character of the copulatory appendages as well as that of the genital chaetæ in both species closely correspond.

6. 6. It is concluded that Alma worthingtoni Stephenson 1930 is the same as Alma emini Michaelsen 1892.

     

Natural diet of fish and crabs associated with the phytal community of Sargassum cymosum C. Agardh, 1820 (Phaeophyta,Fucales) at Ponta das Garoupas,Bombinhas, Santa Catarina State,Brazil

The diet of fish and crabs associated with Sargassum cymosum beds was analysed at Ponta das Garoupas, Santa Catarina State, southern Brazil. They are reported to feed on phytal organisms. The relative importance of food items was established for these consumers, and the frequency of occurrence and volumetric methods were used for quantitative analysis. The analysis of 272 guts from 11 fish and two decapod species revealed that eight fish and one crab species had phytal organisms as important items in their diet. Amphipods and molluscs were the main phytal animals in the diet of these fish and the crab; notably Caprella scaura, Hyale media, Atylus minikoi, Tricolia affinis and Bittium varium. Commercially important fish, such as the grouper Epinephelus guaza, feed on these fish and crabs, showing that Sargassum beds constitute an important link between benthic autotrophic producers and several levels of consumers on rocky shore ecosystems at Ponta das Garoupas.     

Insects and spiders on snowfields in the Cairngorms,Scotland

Summary

An account is given of seven collections of insects and spiders made in summer 1979 on snowfields above 1100m elevation in the Cairngorm mountains, Scotland. In one comprehensive collection 278 recently deposited animals representing 35 species were obtained in 25 m²; the other collections were selective. A high proportion of the roughly 700 specimens obtained have been identified. They represent at least 130 species, including 12 species of Araneae and 34 species each of Coleoptera, Hymenoptera and Diptera. Only 10 species are known to be restricted to ‘montane’ environments and it is concluded that the composition of fallout on mountain snowfields, both in Britain and elsewhere, reflects mainly the nature of the vegetation, and thus of the insect communities, in upwind areas at lower elevations. The discussion concerns the significance of fallout as a resource for high altitude communities and as a manifestation of long-distance migration and potential gene flow among populations of terrestrial arthropods.     

Feeding behaviour of fifteen species of hermit crabs (Crustacea: Decapoda: Anomura) from the Otago region,southeastern New Zealand

Summary

The feeding behaviour of 15 species of hermit crabs from four families (Pylochelidae, Diogenidae, Paguridae and Parapaguridae) and from habitats ranging from rocky intertidal through continental shelf gravelly sediments to finer sediments on the shelf edge and continental slope, is described.

Feeding mechanisms found include various methods of deposit-feeding, browsing, suspension-feeding, predation and scavenging. Each species employs one or two primary feeding mechanisms but also a number of secondary mechanisms. Depositfeeding techniques include scooping up detritus-rich sediment, scrubbing detritus from the surface of small granules, scraping it from larger surfaces, picking it out of crevices and other irregularities, and brushing out and ingesting material which adheres to the general body setation. A few species browse on algae and sedentary colonial invertebrates which they slice or pluck off with the chelae. A number of species filter particles out of suspension using either the general setation of the body and/or specially modified appendages which are swept through the water. Predators either capture and ingest small organisms they encounter more or less accidentally, or actively search for prey. The latter include two species which excavate pits in the sediment in search of burrowing invertebrates. All the species studied fed upon carrion although some fed much less readily than others.

Feeding behaviour in the species studied is discussed in relation to their morphology and habitat. Previously published work on feeding in hermit crabs is reviewed. It is concluded that the broad range of feeding techniques shown by most species is probably of adaptive significance as it enables the crabs to deal with a variety of different foods and substratum types.