FIVE SPECIES OF MATUTA (CALAPPIDAE, BRACHYURA, DECAPODA) FROM INDONESIA

Five species of Matuta from Indonesia i.e. lunaris, planipes, banksii, inermis and cuntispina are differentiated and grouped according to several important morphological characters. Each species is briefly described but extensively illustrated including the first and the second male pleopods. The first male pleopod of M. curtispina is quite different from the other four. The use of the structure of the stridulating organs as one of the important characters in classifying the species is emphasized and a new key is established.


INTRODUCTION
In a previous paper (ROMIMOHTARTO 1967) I recorded four species of Matuta from eastern Indonesian waters, two of which were not identified.
I was able to re-examine that material and compared it with the reference material of the National Museum of Singapore.
Several corrections in identification and synonyms given by some authors have been made, but sometimes the situation of some species is somewhat confused in the litterature.
In the existing keys, some of the discrepancial characters to separate the species, such as the breadth of the frontal border in regard to the length of the orbit have a relative value.A comprehensive review of the morphological characters of the species, therefore, seems to be necessary in order to facilitate the grouping of those species and their identification.
My new key refers to such a review for the five species of Matuta i.e. lunaris, planipes, banksii, cuntispina and inermis.
MORPHOLOGICAL ACCOUNT 1. S t r i d u l a t i n g organs.-The stridulating organs provide one of the most clear characters to separate at least the male of the five species.Three pairs of stridulating organs always exist on the male and at least two pairs exist on the female, i.e. one on the pterygostomian region close to the cavity; one on the inner surface of the palm of the cheliped; and one stridulating organ, like a longitudinal striated line, on the external face of the dactylus or on the outer face of the palm of the cheliped (Fig. 1 -4).
That organ is considered as a "subsidiary" or additional stridulating mechanism by BARNARD (1950), who mentions it on lunaris and banksii.It is called eccessory stridulating organ by GUINOT & DUMORTIER (1960).
The accessory stridulating organs do not exist or are very feeble on the female of certain species (lunaris, planipes and banksii) while they are well developed on the outer face of the dactylus of the male.
In curtispina and inermis, the accessory stridulating organs are well developed in both sexes, but instead of being on the dactylus, they are on the longitudinal median line of the outer face of the palm extending from the cleft between the dactylus and the palm to the posterior border of this palm.In inermis this organ differs in both sexes.In the male it runs along the middle line from the left between the dactylus and the palm to the posterior border of the palm, while in the female it is replaced by five sharp tubercles.In curtispina there is no difference in both sexes.
Those morphological structures emphasize the sexual dimorphism existing on Matuta, which is only briefly mentioned by some authors (MIERS, 1879, 1884, ALCOCK, 1896).But BARNARD (1950) has noticed that on lunaris and banksii the accessory stridulating organs are feeble or nil on females and young males.
2. Other discrepancial characters.a.The development of the epibranchial spine gives a clear separation of the species into two group i.e. group I (lunaris, planipes, banksii), of which the epibranchial spine is well developed and group II (curtispina and inermis), of which the epibranchial spine is poorly developed or rudi mentary.
b.The tubercles on the dorsal surface of the carapace are clearly more salient in some species and less so in others.The values of this character is sometimes difficult to evaluate without comparative material.Nevertheless the presence of a salient tubercle on the postero-lateral border of the carapace in banksii provides a good character ,as it never or faintly indicated in any other species.
c.The outer face of the palm of the cheliped is ornamented with four or five ridges, three on the upper half, which in curtispina and inermis is somewhat irregular and one or two on the lower half.
In lunaris and planipes there is only one ridge on the lower half, which connects anteriorly with penultimate tooth of the immobile finger.This ridge ends posteriorly in a spine.In lunaris, this ridge is smooth and continuous.In plardpes, this ridge is disconnected from the spine by irregularly granulated line in the proximal half (Fig. 5 -6).
In banksii, the lower half of the outer palm is ornamented with two dentate ridges (Fig. 7).One on the middle line, running from the cleft between the mobile and immobile fingers to a spine posteriorly; in curtispina and inermis, this ridge is replaced by the accessory stridulating organ.The other, which corresponds to those of lunaris and planipes, lies below that ridge, anteriorly reaches the pinultimate tooth of the fixed finger.
On banksii the dentate ridge of the outer face of the lower margin of the palm corresponds to those of curtispina and inermis and banksii could be considered as an intermediate species between the first group and the second group.
d.The teeth of the dactylus of the chelipeds differ on curtispina and inermis from those of plariipes y lunaris, banksii; a character which has already been mentioned only on curtispina by SAKAI (1965).
e.The male abdomen was used by CHOPRA and DAS (1931) to separate lunaris from planipes; the abdomen being narrower on lunaris.It has the telson 1.4 longer than broad at base on lunaris and nearly as long as broad at base on planipes.The character seems to have no absolute value; specimens of approximately the same size have, in any way, to be compared.
f.The first male pleopod of this genus is characterized by the presence of a horny tooth on the innner face, near to the outer margin of the distal portion  and the presence of two batches of granules, one on the outer face, bordering a part of the outer margin of the distal portion, the other on the inner face near to the inner margin of the distal portion.These batches of granules, however, are not seen in curtispina.The Atlantic species (M.michaelseni BALSS) shows a very different form, without horny tooth and with tapering apex.(MONOD 1956, p. 99).
In curtispina the shape of the first male pleopod is quite different from the other three.The rounded apex is deflexed downwards, so that the horny tooth is exposed on the top and can be seen partly from ventral side.No sign of sharpish granules visible.
The second male pleopod, which is always longer than the first one, varies a little in Matuta.The middle part of its hemp is provided with a hook which migM serve as a mean of attachment to the first male pleopod.
In curtispina the tip of the second pleopod is clearly different from those of the first group.In our specimen, it is characterized by the presence of five minute spines.But in general the morphological differences among the second male pleopods of Matuta are so slight so as to have little taxonomic importance.

GROUPING AND DIFFERENTIATION OF THE SPECIES.
The five species can be divided into two different groups by some outstanding morphological characters; i.e, epibranchial spine, male acces-sory stridulating organ, the stridulating organ on the inner face of the palm of both sexes and the presence or absence of a molariform tooth on the cutting edge of dactylus of the cheliped.
In group I the accessory stridulating organ of the male is found along the outer face of the dactylus and none on the outer face of the palm.In group II, on the contrary, this organ does not exist on the dactylus, but is found along the middle line of the outer face of the palm, The stridulating organ on the inner face of the palm in strongly striated in group I and granulated or very feebly striated in group II.
In each species of the first group, the disposition, the number ajid the shape of the , striae constituting the accessory stridulating organ are specific and thus give by themselves a mean for specific differentiation.In lunaris the striae numbering 24 -26 are comparatively thick and broadly separated from each other.In planipes the striae numbering 34 -36 are less thick and narrower.I banksii the organ consists, on the distal portion (about a quarter of the dactylus length), about 26 conspicuous striae followed posteriorly by a line of very fine ones numbering more than 300.
In the second group the difference between the accessory stridulating organ of the species are as follows: In inermis (Fig. 14) it constitutes a median longitudinal line of the palm from the articulation with dactylus to the proximal border of the outer face of the palm.In curtispina this line is replaced by three sharp tubercles on the proximal half of the palm so as to constitute shorter striated line (Fig. 12).
The striking morphological differences of the two groups of Matuta can be summarized as follows:  (1896, for M. victor), CHOPRA & DAS (1931) and BARNARD (1950).The length-breadth proportion of the composite segment of the abdomen (3 -5) is 1.05 and that of the last segment is 1.33.The male-pleopod of the species has never been illustrated.
Distribution.This species has a wide Indo-Pacific distribution, from Polynesia, Japan, Indonesia to Red Sea and Cape region.Matuta lunaris ALCOCK 1896: 161 -162.Matuta planipes CHOPRA & DAS 1931: 384;SAKAI 1936: 50, Pl. 8, fig. 1;SAKAI 1965: 60, PL 24, fig. 3. Material. N.M.S. 1965.10.13.31, ♂ of 37mm. breadth;36mm. length;8mm. lateral 1931) use, among other characters, the length-width proportion of the 3 -5 segment and terminal segment of the abdomen to differentiate this species and the closely allied one (M.lunaris).But this character is not absolutely applicable since one or two of our specimens do not conform exactly with this character.Sufficient material might help to clarify this thing.However, the two species are easily differentiated by the different number of striae of the accessory stridulating organ of the adult male specimen, as mentioned in the key.
Observation.The adult male specimen of this species is easil; recognizable by the structure of the accessory stridulating organ, on th outer face of the movable finger, which consists of very fine striae hardl: visible to the naked eye, which DE MAN (1886) considers as nearly absolete and followed by gradually enlarged ones distally.The other character which clearly differentiate this species from the former two are the texture of the outer face of the palm, which instead of having the fourth ridge (counting from above) smooth, is sharply tuberculated, and the tuberculation of the carapace and posterolateral border, which is alway; prominent and not so in the other two.
Distribution.This warm Indo-Pacific species has a wide distribution from the Red Sea and east coast of Africa to the east coast of Asia -] to Polynesia.In Indonesia it is found from Java to many islands in the eastern Indonesian water up to West Irian.Matuta curtispina SAKAI 1961. (Figs. 11, 12;33-38;Pls.IIb, b 1 b 11 , Hie, e 1 ).Matuta curtispina SAKAI 1961: 139, PI. 3, fig. 7;SAKAI 1965: 60 This species is characterized by the very small lateral spine and the presence of the accessory stridulating organ on the middle line of the outer face of the palm, instand of along the outer face of the movable finger.The cutting edge of the movable finger equipped with a molariform tooth near the proximal end which is absent on the former three species.
Distribution.Sagami Bay and off Mikawa Archiprefecture, Arafura Sea.The description of MIERS (1884) agrees with our specimens.But the presence of dimorphism in this species is not mentioned by him.The accessory stridulating organ on the outer face of the palm of the male does not exist on the female.Instead of this the ridge consists of 5 teeth.
This species closely resembles M. curtispina in having the very short lateral spine and a molariform tooth on the cutting edge of the movable finger, differs considerably in the texture of the outer face of the palm and the granulation of the dorsal carapace.
It is interesting to note that this species was found in the same locality and at the same time with M. inermis, in Arafura Sea.

ACKNOWLEDGEMENT.
My sincere gratitude to: Dr. Raoul Serene, UNESCO Expert for South East Asia, for his constant guidance in preparing this paper and his invaluable support in correcting and reviewing the manuscript.
Mr. Eric Alfred M.Sc, Acting Director of the National Museum of Singapore in giving me facility during my work in his Museum.
The present specimens were caught in Arafura Sea near the western coast of West Irian by beam trawl at approximately the same depth (70 m) with that of the type specimen from Japan and was a little smaller than the type.
Observation.MIERS (1884, p. 256 -257)describes one female of 21 mm.length, 20 mm.breadth from Albany Island, 3 -4 fms: two small males from Thuerday Island, 3 -4 fms; three from Prince of Wales channel, 7 fms.and four from Torres Strait, 10 fms. and four other with uncertain locality.All of them are deposited in British Museum.