Genetic variability of tehuelche scallop, Aequipecten tehuelchus (d`Orb., 1835) populations from atlantic patagonian coasts.

REAL LUCIANO ; NOEMI C. GARDENAL; NESTOR CIOCCO

Workshop; 13TH INTERNATIONAL PECTINID WORKSHOP; 2001

GENETIC  VARIABILITY   OF  TEHUELCHE  SCALLOP,  Aequipecten tehuelchus (dOrb.,  1846), POPULATIONS  FROM ATLANTIC PATAGONIAN COASTS. Lucano E. RealCU,  Noemi C. GardenaIO & Néstor F. CioccoflX3) Lucano E. RealCU,  Noemi C. GardenaIO & Néstor F. CioccoflX3) (1)  Universidad  Nacional  de Ia Patagonia  San Juan  Bosco,  ARe. Brown  sIn  (9120)  Puerto  Madryn Chubut, Argentina. (2)  Cátedra  de  QuFmica BioTôgca, Fac.  de  Cs. Médcas,   Univ. Nac. de Côrdoba, (5000) Côrdoba, Argentina. (3) Centro Nacional Patagônico (CONICET), Alte. Brown s/n (9120) Puerto Madryn, Chubut, ArgenUna. Introduction. The Tehueiche scaflop, Aequipecten  (=Chiamys)  tehueichus  (dOrb.,   1846)),  is a warm temperate species that inhabits shallow shelf bottoms from Brazil 23°S) to Argentina  (45°S).  In  most of its distribution  (north of 42°30S), this pectinid has typically  14-19 ?squamous   and relavely rounded ribs.  Towards  the southern  end of its distribution  (42°30?-45°S)  the Tehuelche  scallop  present  11-14 comparativ&y   smoother  and more marked  ribs.  This geographic  variant  has been  described   as  a separate  species, Chiamys  madrynensis   (Lahille,  1906) (Castellanos,   1971),  or subspecies,    Ch. !ehuelchus madiynensis  (Orensanz et a?.,  1991) An eventual  correlation  between  morphological  and genetic differentiation  between the two phenotypes  has never been explored. In  the  northern gulfs of  Patagonia  (41D_42030S), the  Tehuelche   scallop  is the  target  of small inshore sheries, involving dredging  (San Matias Gulf, Figi)  and commercial  diving  (San José  Gulf,  Fig.  1). In spite of the small volumes   landed,  these fisheries   are  of considerable  signicance for the local economies Both  fisheries  are  managed   independenUy  and  are  under  different  provincial   fisheries administrations.  One relevant question is whether the San Matias and the San José Gulfs   sca?lops are independent or inter-connected stocks - We report here  preliminary  results  of the  first  study on  allozyme  variation  of the  A.  tehuelchus populations in order to clarify the taxonomic status of the  madtynensis  fan-n and to explore the genetic structure of San Matias  and San Jose Gulfs stocks. Material  and  Methods.    We examined genetic variation  in a total of 102 individuals from  5 locations (20-22  scallops   each):  1: North  of San Matias Gulf (Bajo  Oliveira-El  SOtano,  4058S-650O6Vd),  2: South  of San Matias  Gulf (Puerto  Lobos  42°01?S-65°04W),   3: San José  Gulf (Tehuelche,  42°23?S- 64°1 9?9,  4: Nuevo  Gulf (Puerto  Madryn,  42°45?S-65°O1 ?W), 5: San Jorge Gulf (Cabo Achaima  45°02?- 65°53?W)  (Fig.  1). Sections of  adductor muscle   and   digestive gland were homogenized    in   distilled water and electrophoesed   in vertical starch gel as described  by Boyer  & Hiner (1963).  Eleven enzymes were studied:  GPI (EC 5.3.1.9), MT  (EQ 2.6.1.1),  PGM  (EC 2.7.5.1),  MDH  (EC  1.1.1.37),  IDH (EQ 1.1.1.42),  SDH  (EC  1.1.1.14),  FAG (EC 3.1.3.2),  EST (EC 3.1.1.1),  LAP (EC  3.4.11.1),  HXDH  (EC  1.1.1.204),  SOD (EC