Morphological variation and a remarkable new sexual dimorphism in the <em>Pseudocyclops xiphophorus</em> population of Lake Faro in northeastern Sicily</span></td>

Abstract

, the natural history museum, Cromwell road, london sW7 5BD, u.K.summary: the population of P. xiphophorus in lake faro exhibits variation in the form of caudal seta V. in some specimens of both sexes, this seta is spatulate but in others it is slender and unmodified. occasional specimens are asymmetrical. in addition to this variation in caudal seta form, the lake faro population displays variation in male body length and in the extent of the sexually dimorphic specialisation of the right swimming leg 2. the scale of these differences between the morphotypes might suggest their taxonomic treatment as distinct species. the modification of the distal two segments of the exopod of right leg 2 in the male is a unique sexual dimorphism. We infer, from the presence of this hook on the right exopod in adult males only, that it is involved in mating behaviour. laboratory-based breeding experiments between females and males showing different combinations of these characters were also performed. experiments comparing egg production rates in females that have mated with modified or unmodified males revealed no significant differences. it appears therefore that gene flow is not interrupted between the morphotypes and that reproductive segregation does not occur. observations of male leg 5 morphology and musculature revealed no significant differences between the two P. xiphophorus morphotypes.Keywords: Pseudocyclops xiphophorus population, lake faro, morphotypes, sexual dimorphism, morphological observation and interbreeding experiments.resumen: Variación morfológica y un nuevo y remarcable tipo de dimorfismo sexual en la población de PseudocycloPs xiPhoPhorus del Lago Faro en el noreste de Sicilia. -la población de P. xiphophorus del lago faro muestra variación en la forma de la seda caudal V. en algunos especímenes de ambos sexos presenta una morfología espatulada, pero en otros es esbelta y sin modificaciones. ocasionalmente, es asimétrica en un mismo individuo. la población del lago faro muestra también variabilidad en la longitud corporal del macho y en el grado de dimorfismo sexual de la segunda pata natatoria derecha. la escala de estas diferencias entre morfotipos podría sugerir un tratamiento específico diferente para ellos. la modificación en el macho de los dos segmentos distales del exópodo de la segunda pata natatoria derecha es un carácter desconocido en otras especies del género. la presencia de un gancho en el exópodo derecho de los machos sugiere que esta modificación está relacionada con el comportamiento de apareamiento. se han realizado cruzamientos en laboratorio entre hembras y machos que mostraban diferentes combinaciones de estos caracteres. la comparación de las tasas de producción de huevos en hembras que se han cruzado con machos con o sin modificaciones no muestra diferencias significativas. parece por tanto que el flujo génico entre morfotipos no está interrumpido y que no tiene lugar segregación reproductiva. la observación de la morfología y del patrón muscular de la pata quinta del macho no ...

Pseudocyclops schminkei (Copepoda, Calanoida, Pseudocyclopidae): a new species from Okinawa

“…nov. is polymorphic; as reported here, it is usually broad proximally and thin distally on most females, but on a few specimens it may be thick proximally but tapering smoothly distally, like the males. A similar polymorphism also has been reported for P. obtusatus asymmetrica by Ummerkutty 1968 and for P. xiphophorus by Brugnano et al (2009). Vervoort (1964) initially described a male genderlimited asymmetry of the exopod of swimming leg 2 of Pseudocyclops, viz.…”

“…the distolateral seta on the distal exopodal complex of males of P. paciWcus. Subsequently, Brugnano et al (2009) described the genderlimited asymmetry of male right swimming leg 2 of P. xiphophorus as a gender-limited dimorphism. In this study, the subtle diVerence in the proximolateral seta of the distal exopodal complex of swimming leg 2 on males of P. schminkei sp.…”

“…Pseudocyclops magnus and P. latens are known only from females and for this reason separating either from similar species remains problematical. Pseudocyclops magnus and P. xiphophorus have been redescribed, respectively, by Yeatman (1975) and by Zagami et al (2005) and Brugnano et al (2009).…”

“…Pseudocyclops obtusatus and its subspecies have been reported from the Atlantic Ocean (Brady and Robertson 1873), the Indian Ocean (Sewell 1932;Ummerkutty 1968), and the PaciWc Ocean (Vervoort 1964), but the conspeciWcity of these specimens has been questioned (Haridas et al 1994). Pseudocyclops xiphophorus Wells, 1967 has been reported as occurring naturally in coastal waters of the Indian Ocean oV Mozambique and in Lake Faro, Sicily (see Wells 1967;Zagami et al 2005;Brugnano et al 2009) although neither a Lessepsian dispersion (Por 1971) nor an introduction by ship ballast water (Carlton 1985) was considered for either of these populations. A broad distribution for P. magnus Esterly, 1911 from Bermuda in the Atlantic Ocean resulted when Nicholls (1944) placed it in synonymy with P. latens Gurney, 1927 from the Red Sea, adjacent to the Indian Ocean, despite a notable diVerence in size between the only female specimen known for each species (0.63 mm vs. 1.1 mm).…”

“…They are almost exclusively marine (Markhaseva and Dahms 2004), although a few species have been reported from brackish waters (Zagami et al 2005, Brugnano et al 2006, 2009. Among the 36 nominal species that have been assigned to Pseudocyclops, excluding 2 nominal subspecies of P. obtusatus Brady and Robertson, 1873, only P. stephoides Thompson, 1895 has been removed from the genus, to Thompsonopia Jaume, Fosshagen and IliVe, 1999.…”