Gastrotricha: India

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Faunal Diversity In India: Gastrotricha

This is an extract from

FAUNAL DIVERSITY IN INDIA

Edited by

J. R. B. Alfred

A. K. Das

A. K. Sanyal.

ENVIS Centre,

Zoological Survey of India,

Calcutta.

1998

( J. R. B. Alfred was

Director, Zoological Survey of India)

Gastrotrich

Introduction

The Gastrotricha constitutes a group of minute and unsegmented worms which swim or crawl with the help of their ciliated epidermis. Their length is quite variable from 0.1 mm to 3.0 mm, with a majority of them being less than 1.0 mm. The body is elongated, strap-shaped or fusiform. Dorsal surface of the worm is generally covered with a variety of cuticular structures as bristles, scales, spines, adhesive tubes, etc., to withstand the mechanical effects of abrasion in the turbulent habitat. The ventral surface is flattened and covered with patches of locomotory cilia for a smooth gliding over solid substrata. The cuticle is thin, flexible and transparent. Adhesive tubes are quite characteristic of this group of animals. These tubes are supplied with cement glands and are used for adhesion to sand grains or vegetation. Gastrotrichs are mostly hermaphrodites, having both male and female reproductive organs.

All the gastrotrichs are free-living and harmless. They occur in all marine, brackish and freshwater habitats. Marine gastrotrichs are mostly interstitial animals liVing in spaces between particles of sandy sediments. They largely feed on fine detritus, bacteria and diatoms of the sedimental. Their greatest density and diversity are limited to intertidal and subtidal parts of the sea. They are known to inhabit from top to 1 m depth below surface. Quantitatively, their densities are known to range from 50 to 1500 individuals per 10 cm2 of the sediment.

Status Of The Taxon

Global and Indian Status

The Gastrotricha constitutes one of the most interesting groups of meiobenthic invertebrates on this earth. They occur in all freshwater and marine habitats in considerable abundance. Being quite sensitive to ecological stress in the habitat, they are practically eliminated in polluted aquatic ecosystems. However, the Gastrotricha still remains one of the most neglected groups of the animal kingdom, our present knowledge of the phylum being limited mostly to the work carried out on European, American and Indian coasts. The number of gastrotrich species at the global level is estimated to vary between 2000 and 3000, with many areas remaining largely unexplored or underexplored for this fauna. The phylum is represented by two major orders, 13 families and 50 genera. Hitherto, the 13 genera Acanthodasys, Dinodasys, Polymenlnls, Xenodasys, Desmodasys; Pseudoturbanella, Marinellina, Musellifer, Clllorodasys, Planodasys, Megadasys, Tlliodasys and Draculiciteria remained monotypic in this phylum, each representing a single. species. Within the Indian region, about 100 species have been recorded pertaining to 2 orders, 9 families and 21 genera. The taxonomic composition and abundance of the gastrotrich genera and species occurring in this region are more or less in agreement with those known from other parts of the world.

Distribution

The gastrotrichs are well represented in all the natural aquatic ecosystems in and around India. Extensive habitats with unpolluted conditions, however, favoured the colonization and evolution of a variety of species and sub-species of the group. Hitherto, only limited areas of this region were explored for the fauna, studied and the taxonomic results reported. These areas include some scattered freshwater bodies on land and littoral sediments along the east and west coasts, including Lakshadweep and the Andaman and Nicobar Islands. Faunistic surveys conducted in recent years at several areas on the Indian coast, however, indicated a remarkable decline of this fauna both in their density and diversity. This is largely to be attributed to the increasing effects of human activities, resulting in pollution of the habitats and degradation of the natural environment.

Biological Diversity And Its Special Features

The phylum Gastrotricha is divided into two main orders, the Macrodasyida and the Chaetonotida. The Macrodasyida are exclusively marine and comprise heterogeneous groups of animals with great morphological diversity. The discovery and study of these worms have made a remarkable contribution to systematic zoology during the present century. A large number of interesting genera and species were described as new to science. The longest gastrotrichs are seen in this order with ribbon¬shaped bodies highly modified and well-adapted for interstitial life. The posterior part of pharynx is generally associated with openings. The characteristic feature of macrodasyidans is the presence of numerous adhesive tubes, occurring typically in three groups, i.e., anterior, lateral and posterior. These worms are highly thigmotactic and contractile to suit life in the turbulent coastal marine environment.

The Chaetonotida are marine, brackish and freshwater inhabitants. However, they are more common in living and decaying benthic vegetation, detritus and floating plants. They are very small in size, with fusiform body, anterior head lobe and two posterior caudal furca, each supporting a single adhesive tube. Tufts of long sensory cilia occur on head lobe. Cuticle has a complex ornamentation, often with spined scales. Pharyngeal pores are lacking. Adhesive tubes are limited to 1-2 pairs on tail forks, but these are absent in pelagic species. The locomotory cilia on ventral body surface are transformed into groups of cirri in the aberrant genus XenotriclIla. The chaetonotids largely reproduce by parthenogenesis. Hitherto, about 98 species of freshwater and marine gastrotrichs have been recorded in Indian region Table -1. They belong to 9 families and the following 21 genera :-Dactylopodola, Cephalodasys, Mesodasys, Paradasys, Macrodasys, Urodasys, Planodasys, Crasiella, Turbanella, Paraturbanella, Dinodasys, Thaumastoderma, Tetranchyroderma, Acanthodasys, Platydasys, Diplodasys, Pseudostomella, Chaetonotus, Aspidophorus, Xenotricula and Dasydytes. Any further extensive exploration of marine, brackish and freshwater habitats is quite likely to reveal the existence of more number of genera and species unknown in these areas. However, the composition of the faunal element hitherto recorded from the Indian region is quite similar to the one recorded on other parts of the world.

Endemic And Threatened Species

A high percentage of endemism is generally known for the terrestrial fauna in insular ecosystems due to their isolation for long periods, while in the marine environment they are eurytopic in their distribution due to great scope for dispersal. As an exception, the marine meiofauna and particularly the macrodasyid gastrotrichs of the intertidal sediments exhibit a high percentage of endemism due to their peculiar mode of existence in a restricted habitat. A perusal of the data presented in Table 1 shows that out of the 98 species hitherto known, 64 are endemics, exhibiting interesting morphological variation. The endemism at supra-specific level is quite negligible. Out of the 21 known genera, only 1 genus Planodasys has been reported as endemic to the Indian region. The endemicity in general is far more greater in the highly thigmotactic Macrodasyida than in the agile Chaetonotida, which are endowed with great power of environmental tolerance, locomotion and dispersal. As a result, many species of the Chaetonotida have been reported as cosmopolitan in their distribution. These geographical ranges are likely to change as more and more area in the Indian Ocean are intensively investigated and some of the presently supposed endemics may join the rank of eurytopics. However, the probable rate of endemism for gastrotrichs in this region appears nearly to be the same as that reported for this fauna from other parts of the world.

Although the whole phylum is being threatened with increasing effects of habitat destruction and organic pollution in the environment, no qualitative or quantitative data are available on the percentage of decline of any species or varieties of populations in this region. Due to these reasons, it is not possible to categorize any particular taxa of this group as threatened or endangered. There is also no published record of any introduced biodiversity for this group of worms which are not in any way related with the routine activities of the common man.

Value

Many of the interstitial marine gastrotrichs are highly modified both in structure and habit to suit the needs of the specialized environment in which they live. Their morphological diversity has contributed largely to augment our knowledge on systematic zoology. They form excellent material for the study of morphological organization, for which reason they are being extensively utilised in laboratories of western countries as types of study for zoology students. These worms are also used in a variety of experimental and interesting ecological investigations related to aquatic biology. As they are quite sensitive to ecological stress, they are being widely employed as indicators of pollution in aquatic ecosystems. Due to their small size, large numbers and short generation times, they are very well-suited for the study of population biology. Thus, the gastrotrichs both in marine and freshwater habitats offer ample scope for carrying out various types of investigations on taxonomy, biology, ecology and distribution.

Further, the gastrotrichs constituting part of meiobenthos in aquatic ecosystems, play an important role in their trophic cycle by forming food for larger animals and by contributing remarkably to the regeneration of nutrients after their death and disintegration. Hence, their mass destruction, no doubt, results not only in great loss of biological diversity, but also upsets the ecological balance in the natural ecosystems. But, hitherto no keystone species as such has been identified in this phylum, playing an important role in the freshwater or marine ecosystem.

Threats

A large number of sand beaches are being removed on a large scale for commercial and construction purposes. Further, the aquatic ecosystems are getting increasingly polluted in recent decades, destroying these natural habitats and their associated meiofauna, including the gastrotrichs. As the organic pollution generates a lot of ecological stress in the environment affecting these highly sensitive organisms, many of them are getting easily eliminated. As a result, the species composition, population density and spatial distribution of gastrotrichs have been very much affected in the intertidal sediments in the vicinity of all human settlement areas. For these reasons, many of these strange animals are perishing undiscovered, undescribed and unknown. Thus, the sand beaches are becoming increasingly barren for many of these organisms. The effects of pollution are also quite likely to increase in the following years seriously endangering the life of these micro-denizens.

Conservation

Hitherto, no conservation measure as such has been undertaken to protect these microscopic animals from lethal effects of potential pollution in the aquatic ecosystems. It is a sad augury that the fauna discovered in the present century is also being finished in the same century due to the disturbing activities of man. Thus, the present status of gastrotrichs is also one of the saddest chapters in the recent history of animal discoveries. In the circumstances, these tiny creatures are to be protected from pollution and habitat destruction. Unless effective conservation measures are undertaken in time, it would be difficult to preserve this unique group of organisms from indiscriminate destruction and irreparable loss. But whatever conservation measures we now undertake at this stage, matters have already reached such a critical condition at several areas that the rich variety of animal life we inherited in this region can never be the same again.

Selected References

Beauchamp, P. 1965. Classe des Gastrotriches. Traite de Zoologie, 4 : 1381-1430. Hyman, L. H. 1959. The Invertebrates: Smaller cae/ornate groups. McGraw-Hill Book Company, New York, 5 : 697-766. Remane, A. 1936. Gastrotricha and Kinorhyncha. Klassen and Ordnungen des Tierreichs, 4 : 1-242. Schmidt, P. 1974. Interstitialle fauna von Galapagos IV. Gastrotricha. Mikrofauna Meeresboden, 26 : 497-570. Schrom, H. 1972. Nordadriatische Gastrotrichen. Helgolander wiss Meeres. 23 : 286-351. Voigt, M. 1958. Gastrotricha, Tierwelt Mittelleuropas, 1 : 1-74. Wielkopolski, S. 1968. Gastrotricha. Posnan. Towar. Pn.y. Nauk, 36 : 1-91. Wilke, U. 1954. Mediterrane Gastrotrichen. Zool. lb. (Syst.), 82 : 497-553.

Gastrotricha

This is an extract from
ANIMAL RESOURCES OF INDIA:
Protozoa to Mammalia
State of the Art.
Zoological Survey of India, 1991.
By Professor Mohammad Shamim Jairajpuri
Director, Zoological Survey of India
and his team of devoted scientists.
The said book was an enlarged, updated version of
The State of Art Report: Zoology
Edited by Dr. T. N. Ananthakrishnan,
Director, Zoological Survey of India in 1980.

Note: This article is likely to have several spelling mistakes that occurred during scanning. If these errors are reported as messages to the Facebook page, Indpaedia.com your help will be gratefully acknowledged.

Introduction

Gastrotricha constitutes one of the most interesting and challenging groups of meiobenthic marine invertebrates. They are minute, unsegmented and acoelomate worms which swim or crawl by means of their ciliated epidermis. The length of the wonn is generally less than 1.0• mm, the smallest ones being even less than 0.1 mm, while the largest ones are more than 3.0 mm. The body is elongated, straP7.shaped or fusiform and dorsally covered with a variety of cuticular structures as bristles, scales, spines, adhesive tubes, etc., to withstand effects of abrasion in the habitat. The ventral swface is flattened and covered with patches the locomotory cilia for smooth gliding over solid substratum. The cuticle is thin, flexible and transparent. Adhesive tubes supplied with cement glands are used for adhesion to sand grains or vegetation. They are mostly hermophrodites.

The gastrotrichs are highly varied and sufficiently distinctive to be classified as a separate phylum, which is divided into two main orders, the Macrodasyida and the Chaetonotida. The Macrodasyida are exclusively marine and comprise heterogeneous group of animals with great morphological diversity. The discovery and study of those worms during the present century have been a significant landmark in zoology. The longest gastrotrichs are seen in this group with ribbon-shaped bodies well adapted for interstitial life. Anteriorly, head is not always delineated and posteriorly the tail is truncate or round or forked or pointed or drawn to a tapering filament.

The most interesting and characteristic feature of macrodasyidans is the presence of numerous adhesive tubes arranged in rows in a bilaterally symmetrical fashion. These tubes typically occur in three groups distributed anteriorly on ventral, surface of head, laterally on ve~tral surface of trunk and posteriorly along the tail region. However, some exceptions to this general pattern are seen. The posterior part of pharynx is generaIly associated with pharyng.eal openings. These worms are highly thigmotactic, contractile and exhibit leech-like movements to suit life in this turbulent and dynamic environment

The Chaetonotida are marine, brackish and freshwater inhabitants. They are very small in size, with fusiform body, anterior head lobe and two posterior caudal furca, each with a single adhesive tube. Tufts of long lateral sensory cilia occur on head lobe. Cuticle has a complex ornamentation, often with spined scales. Pharyngeal pores are lacking. Adhesive tubes are limited to 1-2 pairs on tail forks. These tubes are, however, absent in the pelagic families-Dasydytidae and Neogosseidae. The characteristic locomotive cilia on the ventral body surface are transformed into groups of cirri in the genus Xenotrichula. All the body parts are largely bilaterally s•ymmetrical. Chaetonotids mostly reproduce by parthenogenesis.

Marine gastrotrichs are mostly interestitial animals living in spaces between particles of sandy sediments, their greatest density and diversity being limited to intertidal and subti~al parts of the sea. They are also known to inhabit from top to 1 m depth below surface. Quantitatively, their densitieS in marine sediments were reported to range from 50 to 1500 individuals per 10 cm2 of the sediment. On the other hand, the freshwater gastrotrichs are less common in soft sediments due to absence of adequate interstitial spaces for colonisation, while they are more common in living and decaying benthic vegetation, detritus and floating plants. The chaetonotidans, due to their great powers of locomotion and tolerance to wide range of environmental variation, are mostly cosmopolitan in their distribution. All the gastrotrichs are free-living and hannless. They play an important role in the troph~c cycle of aquatic habitats by forming food for larger animals and by contributing to the regeneration of nutrients in the ecosystems after their death and disintegration. As the gastrotrichs also form excellent material for the study of morphological organisation, they G.C. Rao, Zoological Survey of India) Port Blair. are being extensive utilised in laboratories of western countries as types for zoology students. They are also used in a variety of experimental and interesting ecological investigations. As these wonns are quite sensitive to ecological stress, they are widely utilised as indicators of pollution in aquatic ecosystems. Thus, the gastrotrichs, both in marine and freshwater habitats, offer ample scope for carrying out various types of investigations on taxonomy, biology, ecology and distribution.

Historical Resume

The earliest gastrobichs were discovered during different periods of the 19th century and since then a large number of genera and species were described as new to science, particularly on the European and North American coasts. Most of our basic knowledge and conception of the rich variety of gastrotrichs is due to the pioneering contribution made by Prof. Adolf Remane of the Kiel University from North, Baltic and Mediterranean seas. However, in Gastrotricha still remains one of the most neglected groups. While studying the sand-living copepods on Madras coast, Krishnaswamy (1957) reported for the rust time the occurrence of marine gastrotJtichs on the Indian coast.

Later, Ganapati and Rao (1962) in a pioneering effort reported the occurrence of gastrotrichs from the interstitial meiofauna in the intertidal sands on Waltair coast. Detailed investigations of the gastrobichs from Waltair beach sands resulted in the discovery of 13 known species (Rao and Ganapati, 1968). Subsequent studies of the fauna in this region have resulted in the description of a new species, new genus and new family (Rao and Clausen, 1970). Exploration of the intertidal sediments at several localities on the east coast of India has brought to light more known and unknown species of gastrotrichs (Rao, 1969, 1970, 1980, 1981a, b). On the south-west coast of India, Govindan Kutty and Nair (1969) reported the occurrence of 7 species from intertidal sands, of which one was described as new to science.

They have also studied (1974) the behaviour of gastrotrichs in the colonisation of different grades of marine beach sands. Beyond the Indian subcontinent, studies on the interstitial meiofauna of the intertidal and subtidal sediments have led to the•discovery of more known and unknown species of marine gastrotrichs from Andaman & Nicobar Islands (Rao, 1975, 1980, 1987, 1988, 1989) and Lakshadweep (Rao, 1983, 1990).

Limited work has been carried out on freshwater gastrotrichs of the Indian subcontinent. Vanamala Naidu (1962), Dhanapati (1976), Rao and Chandramohan (1977) and Sharma (1980, 1987) reported on the occurrence of several known species of chaetonotid gastrotrichs from different wells and ponds in India. There are many areas within the Indian region which remain unexplored or under explored in marine, brackish and freshwater habitats, offering ample scope to carry out taxonomic and ecological investigations on the gastrotrich fauna.

Estimation of Taxa

The number of gastrotrich species at the global level are estimated to vary between 2000 and 3000, with many areas remaining largely unexplored or under explored. Taxonomic features generally utilised in the identification of gastrotrichs include the shape of body, head lobes, tentacles and ciliary tufts, pestle and chordoid organs, structure of mouth and buccal cavity, pharyngeal pores, structure of cuticular armature as scales, spines, hooks, papillae, etc., arrangement of locomotory ciliary bands or cirri, structure of tail lobes and caudal forks, number and disposition of adhesive tubes and the ammgement and structure of reproductive organs.

The Macrodasyida are presently represented by 28 genera belonging to 6 families namely, Dactylopodolidae, (Xenodasys, Dactylopodola, Dendrodasys), Lepidodasyidae (Lepidodasys, Cephalodasys, Pleurodasys, Mesodasys, Megadasys, Dolichodasys, Paradasys), Macrodasyidae (Macrodasys, Urodasys), Planodasyidae (Planodasys, Thiodasys, Crasiella), Turbanellidae (Turbenella, Paraturbenella, seudoturbanella, Dionodasys, Desmodasys) and Thaumastodermatidae (Thaumastoderma, Tetranchyroderma. Acnthodasys, Platydasys, Hem idasys Diplodasys, Pseudostomella, Ptychostomella).

The Chaetonotida are known to comprise 21 genera belonging to 7 families, namely Chaetonotidae (Chaetonotus, Muselli/er, Aspidophorus, Halichaetollotus, Lepidodermella, Heterolepidoderma, Ichthydium, Polymerurus), Neodasyidae (Neodasys),

Xcnobichulidae (Xenotrichuia, Heleroxenotrichula, Draculiciteria), Dichaeturidae (Dichaeture. Marinellina), Proichthydidae (Proichydium, Proichthydioides), Neogosseidae (Neogossea, Kijanebalola) and Dasydytidae (Dasydytes, Metadasydytes, Stlochaeta).

Within the Indian region, all the six recognized families of Macrodasyida and only 3 families of Chaetonotida viz.• Chaetonotidae, Xenotrichulidae and Dasydytidae are hitherto represented with the 20 genera Dactylopodl?la, Cephalodasys, Mesodasys, Paradasys, Macrodasys, Urodasys, Planodasys, Crasiella. Turbanella, Paraturbanella, Dinodasys, Thaumastoderma, Tetranchyroderma, Acanthodasys, Platydasys, Diplodasys, Pseudostomella, Chaelonolus, Aspidop~rus, Xenotrichula and Dasydytes. Any further intensive explorations of marine and freshwater habitats are, however, likely to reveal the existence of more genera unknown in this region. The family-wise representation of the gastrotrich species hitherto recorded from this area is given below.

The composition and abundance of the gastrotrich genera and species occurring in this region are more or less in agreement with those known from other parts of the world. A perusal of the data presented here shows that out of the 88 species encountered, 60 are endemics,' the endemicity being, however, more in Macrodasyida than in Chaetonotida endowed with greater powers of locomotion. These geographical ranges likely to change as more and more areas in the Indian Ocean are intensively investigated, some of the presently supposed endemics joining the ranks of eurytopics. The probable endemism pf gastrotrichs in this region, however, appears nearly to be the same as reported for the fauna in other parts of the world.

Studies from Different Environs

Among the Macrodasyida, the Dactylopodolidae are poorly represented on the Indian coast. Dactylopodola indica was described by Rao and Ganapati (1968) from the beach sands of Waltair coast and the same later reported from the intertidal sediments on Orissa coast (Rao, 1969), Andaman Islands (Rao, 1980) and Lakshadweep (Rao, 1983). The Lepidodasyidae are represented by 3 interesting species Paradasys liltoralis, P. lineatus, Mesodasys hexapodus described on the east coast, which are likely to prove endemic to this region, The Macrodasydae are better represented by the two eurytopic species Macrodasys caudatus Remane and Urodasys viviparus Wilke, while 4 new species of Macrodasys were also described, M. waltairensis and M. hexadactylus on the east coast (Rao and Ganapati, 1968; Rao, 1970) and M. indicus from Lakshadweep (Rao, 1990). Two new species of the family Planodasyidae viz.• Planodasys marginalis and Crasiella indica were described from Waltair and Gopalpur beaches, respectively (Rao and Clausen, 1970; Rao, 1981).

1\'lap slu)\ving the a.•cas on Indian Coast \vhere marine gast'rotrichs were collected, studied and .•l'ported. Nunlbers indicate the species recorded. The Turbanellidae are common in the intertidal sediments and the following species were encountered viz.• Turbenella bengalensis. T. india and T. eminensis, Paraturbenella boadeni, P. palpibara. P. mesoplera. P. brevicaudatus (Rao and Ganapati, 1968, Rao, 1970, 1981, 1990). The ThaumastodermaLidae constituting the most diversified taxa of marine Gastrotricha are represented by 16 species with many species yet to be described, the morphologically interesting ones being Telranchyroderma indica. T. swedmarki. T littoralis. T. paralittoralis. Diplodasys remanei and Pseudostomella indica (Rao and Ganapati, 1968; Rao, 1970, 1973, 1990). The widely distributed specics, Thaumastoderma heideri Rename was recorded at many places on the Indian coast including Lakshadwcep and Andamans.

Among the marine Chaetonotida, except for the ubiquitous species Aspidophorus marinus Remane, majority of the species bclong to the genera Chaetonotus and Xellotrichula. The occurrence of the European species, Chaetonotus atrox Wilke, Xenotrichula velox Remane and X. subterranea Remane on the Indian coast is quite interesting. The new chaetonotid taxa described from this region inclupe Xenotrichula tentaculatus. X. laccadivensis and Chaetonotus triradiatus (Rao and Ganapati, 1968; Rao, 1990). The freshwater gastrotrichs, on the other hand, are mostly dominated by the genus Chaetonotus with the record of about 20 widely distributed species. Visvesvara (1963) described two new species from Nagpur in Central India.

Current Studies

Studies on thc systematics and distribution of marine Gastrotricha are being presently carried out by G. C. Rao in the Zoological Survey of India. These studies are mostly based on the collections made during different faunistic surveys undertaken by this department along various coastal rcgions. Outside ZSI, no serious attempts are made to study the gastrotrich fauna. Intensive swvey of unexplored and under explored areas are quite likely to reveal the existence of more known and unknown species of the gastrotrichs. Faunistic surveys conducted at several areas on the Indian coast for the past three decades, however, indicated a remarkable and progressive decline of this fauna both in their density and diversity. This was largely due to the increasing effects of human activities, resulting in the degradation of natural environment due to pollution.

Expertise India

In ZSI

G. C. Rao, Zoological Survey of India, Middde Point, Port Blair -744 101.

Abroad

P. J. S. Boaden, Marine Biological Station, Portaferry, Northern Island, U. K.

C. Clausen, Zoologisk Laboratorium, AIlegt. 41, N-5000 Bergen, Norway.

S. A. Gcrlach, Institute fur Mcereskunde, Dustembrookerweg 20, 0-2300 Kiel, Gcnnany.

J. L. Hondt, Laboratoire Biologic Invertebres Marines, Museum Historie Naturelle, 57 Rue Cuvier, F-75 Paris-5, France.

W. D. Hunnon, Departnlent of Zoology, Ohio University, Athens, Ohio, U.S.A.

J. Rcnaud-Mornant, Muscum national d'Historie naturelle, Laboratoire des vcrs, 61 rue de Buffon, 75231 Paris Ccdcx 05, France.

R. M. Ricger, Institut fur Zoologie, TechnikerSlr. 25, A-6020 Innsbruck, Austria.

E. E. Fuppcrt, Department of Biological Sciences, Clemson University, Clemson, SC 29634,


Schmidt, Zoologisches Institut der Universitat Gouingen, Gottingen,Gennany.

Schrom, Mediterranean Marine Sorting Centre, Khereddine. Tunisia.

Selected References

Beauchamp, P. 1965. Classe des Gastrotriches. Traite de Zoologie, 4: 1381-1430.

Hyman, L. H. 1959. The Inyertebrates : Smaller coelomate groups. McGraw-Hill Book• Company, New York, 5 : 691-166.

Remane, A. 1936. Gastrotricha und Kinorhyncha. Klassen und Ordnungen des Tie"eichs, 4: 1¬ 242. Schmidt, P. 1914. Interstitialle fauna von Galapagos IV. Gasttotricha. Mikrofauna 26 : 497-570. Schrom, H. 1912. Nordadriatische Gastrotrichen. Helgolander wiss Meeres, 23: 286-351. Voigt, M. 1958. Gastrotricha, Tierwelt Mitteleuropas, 1 : 1-14. Wielkopolski, S. 1968. Gasttotticha. Posnan. Towar. Przy. Nauk. 36 : 1-91. Wilke, U. 1954.' Mediterrane Gastrotrichen. Zool. Jb. (SysL), 82 : 491-553.

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