NOTES 339
Mauri, M. and E. Orlando. 1983. Variability of zinc and manganese concentrations in relation to sex and season in the bivalve Donax trunculus. Mar. Pollut. Bull. 14: 342-346. McConchie, D. and L. M. Lawrance. 1991. The origin of high cadmium loads in some bivalves molluscs from Shark Bay, Western Australia: a new mechanism for cadmium uptake by filter feeding organisms. Arch. Environ. Contam. Toxicol. 21: 303-310. Nugegoda, D. and P. S. Rainbow. 1987. The effect of temperature on zinc regulation by the decapod crustacean Palaemon elegans Rathke. Ophelia 27: 17-30. Orlando, E. ]985. Valutazione dell'inquinamento marino da metalli pesanti tramite ]'uso di indicatori biologici. Oebalia XI: 93-100. Orren, M. J., G. A. Eagle, H. F.-K. O. Hennig and A. Green. 1980. Variations in trace metal content of the mussel Choromytilus meridionalis (Kr.) with season and sex. Mar. Pollut. Bull. 11: 253- 257. Rainbow, P. S. and A. G. Scott. 1979. Two heavy metal-binding proteins in the midgut gland of the crab Carcinus maenas. Mar. BioI. 55: 143-150.
DATE ACCEPTED: April 13, ]994.
ADDRESSES: (K.F.) Western Australian Marine Research Laboratories, PO Box 20, North Beach 6020, Australia; (CS.) Chemistry Centre of Western Australia, 125 Hay Street, East Perth 6004, Australia; (M.J.) Health Department of Western Australia, 189 Royal Street, East Perth 6004, Aus- tralia.
BULLETINOF MARINESCIENCE,56( I): 339-343, 1995
KARYOLOGICAL STUDIES ON THE COMMON ROCKY EGYPTIAN CHITON, ACANTHOPLEURA GEMMATA (POLYPLACOPHORA: MOLLUSCA)
Ahmed E. Yaseen, Abdel-Baset M. Ebaid and I. S. Kawashti
Acanthopleura gemmata (Blainville, 1925) is one of the commonest polypla- cophoran species and is very common along the Egyptian coasts (northwestern part of the Red Sea) (Soliman and Habib, 1990). Several studies on polyplacopho- rans carried out along the coast of the Red Sea show that the largest and most common species are in the genus Acanthopleura (Bemert and Rupert, 1981). A recent revision of the genus Acanthopleura by Ferreira (1986) using morphometric data revealed that the most common species, present virtually everywhere in the tropics, is A. gemmata. At present very little is known about the chromosomes of Polyplacophora. Vitturi (1982) reported that the diploid chromosome number of Chiton olivaceus is 2n = 26. Vitturi et al. (1982) mentioned that the two species, Middendorffia caprearum and Acanthochiton communis possess a diploid chromosome number of 2n = 24 even though they belong to different families and orders as well, To the best of our knowledge chromosomal studies on Egyptian invertebrates are generally lacking, so the aim of the present research is to examine the chro- mosomes of A. gemmata.
MATERIALS AND METHODS
The specimens of A. gemmata were collected from the supra]ittoral to the lower mid-intertidal zones during low tide at day time along the coasts of the northwestern part of the Red Sea. The specimens 340 BULLETIN OF MARINE SCIENCE. VOL. 56. NO. I. 1995
I. II -1---2--3-_4_h " A II " -5--6--7-_8_•• .. II •• --9 --10- .{!.,~·-~t- Figure 1. A cell spread (left) and karyotype (right) of the Acanthopleura gemmata [2n = 26].
were collected using a sharp knife to release the specimens from dead coral blocks and large stones. The specimens were transferred directly to the laboratory and kept alive in tanks of aerated sea water. They fed largely on minute algae encrusting the rocks and various kinds of seaweeds (AI-Hussaini and Demian, 1969). For cytological studies, chromosome preparations were made by the warm-dry method (Corni and Mancini, 1986 and Nakamura, 1986) employing several males and females of A. gemmata as follows: following an intraperitoneal injection of 20 ILlof 0.05% colchicine after I h, testis, ovaries and gills were diced into 10 mm cubes under I% sodium citrate and kept therein 20 min, fixed in Carnoy fluid for 30 min, treated in 60% acetic acid on a warm slide and stained with Giemsa (pH 7) for 15-20 min at room temperature. Chromosomes were examined and photographed with a Zeiss Ultraphot microscope. Nomenclature for centromeric position of chromosomes followed the terminology of Levan et al. (1964).
RESULTS The chromosome number for A. gemmata (25 females and 22 males) was de- termined from gills, oogonial and spermatogonial germ line cells. The chromo- somes of 25 mitotic metaphase spreads (15 from females and 10 from males) were counted. All cells showed the diploid chromosome number of 2n = 26 as shown in Figure lao The chromosome complements were arranged into pairs in two groups on the basis of size and centromeric position for the karyotype (Fig. Ib). Group A consists of 10 pairs of metacentric (arm ratio 1.00-1.40) and group B consists of three pairs of submetacentric (arm ratio 1.82-2.17). Arm ratio, relative length and centromeric indices were given in Table 1. Idiograms (Fig. 2) were constructed based on relative lengths and centromeric indices. For the latter, the centromeres were drawn at the same level making visual comparison easier. No sex differentiated chromosomes were detected.
DISCUSSION Our study revealed that the basic chromosome number of A. gemmasta is 2n = 26. This result is in agreement with Vitturi et a1. (1982) which reported the diploid chromosome number of Chiton olivaceus (2n = 26) without karyotypes. Our results revealed also that no differences were observed in the sex chromo- somes of both sexes in this species. We conclude that this result was recorded for the first time in Egypt. They also confirm the opinion of the importance of using chromosomal analysis in recent NOTES 341
, c ·til 0 ~§ ::E::E::E u~ ::E::E::E::E::E::E::E::E::E::Euiuiui
r--OO\ •..•OOOOO"
_~ ______N 00'D00'D'D'D'D'Dr--000\0\ •..• 0 .9 Vl cicicicicicicicicicicicici 1:! + +++++++++++++ E ~c -< ~'" ~~~~~~~~-:~~
16 NOTES 343
taxonomy and the coupling of morphological description and chromosomal anal- ysis is ultimately useful in this respect.
LITERATURE CITED
Al-Hussaini. A. H. and E. S. Demian. 1969. Practical animal biology. II: 231-237. Bemert, Gunnar and O. Rupert. 1981. Red Sea coral reefs. Ke-Gan-Paul Press Ltd, Kent, London. 192 p. unavailable Blainville, H. D. 1925. Oscabrion, Chiton. 36. Pages 519-55 in F. Guvier, ed. Dictionnaire de sciences naturelles, 60 Vols. Paris and Strasbourg. Corni, M. G. and T. Mancini. 1986. A chromosome study of Chamelea gallina (L.) (Bivalvia: Ve- neridae). Bull. Zool. 53: 23-24. Ferreira, J. A. 1986. Acanthopleura. Guilding, 1829 (Mollusca: Polyplacophora). Veliger 28(3): 221- 279. Levan, A., K. Fredga and A. A. Sandberg. 1964. Nomenclature of centromeric position on chromo- somes. Heredity 52: 201-220. Nakamura, H. K. 1986. Chromosome of the Archaeogostropoda (Mollusca-Prosobranchiata) with some remarks on their cytotaxonomy and phytogeny. Publ. Seto. Mar. BioI. Lab. 31 (316): 191- 267. Soliman, F. and T. Habib. 1990. Studies on the Acanthopleura gemmata. The common rocky Egyptian chiton species (Mollusca: Polyplacophora) in the northwestern Red Sea. Bull. Fac. Sci., Assiut Univ. 19 (I-E): 55-70. Vitturi, R. 1982. The chromosome of Chiton olivaceus (Spengler) (Polyplacophora). BioI. Zbl. 101: 647-651. ---, M. B. Rasotto and N. Farinella-Ferrizza. 1982. The chromosomes of 16 molluscan species. Boll. ZooI. 49: 61-71.
DATEACCEPTED:May 5, 1994.
ADDRESSES:(A.E. Y. and A.M.E.) Cytogenetic Laboratory, Zoology Department, Faculty of Science (Qena)-Assiut University, Egypt; (I.S.K.) Zoology Department, Faculty of Science, Al-Azhar University, Egypt.