Bijdragen lol de Dierkunde, 60 (3/4) 225-232 (1990) SPB Academie Publishingbv, The Hague Growing knowledge and understanding of dichromatism and sex reversal in Labridae Machteld J. Roede Health Sciences, State University Limburg, P. O. Box 616, 6200 MD Maastricht, The Netherlands sexual Keywords: Sex reversal, hermaphroditism, diandry, monandry, sex dimorphism, color changes, behavior, Labridae Abstract pour l’explication de l’évolution des divers modes typiques de la biologie reproductive des Labridae. A brief survey is given of current literature in comparison with former studies. Since the 18th century phenotypic diversity of Labridae is of At first in dribs and a matter argument. drabs, yet Introduction last decades at a rapid rate, dichromatic adult morphs are sy- nonymized. There are few monochromatic species. introduction to the marine world was a Wrasses are protogynous hermaphrodites. Most species are My during with Jan Stock described as monandric, but a minority (of slightly or extremely student field trip to southernFrance dichromatic)species is diandric,with both primary and second- of the leaders. fieldwork the as one Later, during on males. Terminal males with but in- ary reproduce single females, "girelle" in Banyuls-sur-Mer and PhD-work on itial phase males spawn in aggregations. Some species are Caribbeanwrasses, Jan happened to be passing by. haremic, and large males are permanently or temporarily ter- he succeeded the late as ritorial. Last decades insight in the various social factors has Finally, professor Engel my Just while contribution greatly increased, resulting in theoretic models to explain the promotor. preparing a to evolution diverse of labrid reproductive of the typical, modes Stock's farewell, Charnov's analysis of sex reversal biology. in labroid fish (1982) was brought to my notice. I refrained from an intended paper on present day work, and became wrapped up once more in the Résumé fascinating world of "my" wrasses, that I left a quarter of a century ago. On passe brièvement enrevue la littérature récente, encomparai- When labrid work my was published (1966- son avec les études plus anciennes. Depuis le XVIIIèmesiècle, la 1975) there was hardly any response. Conform to diversité phénotypique des Labridae est un sujet de discussion. D’abord de façon sporadique, mais ces dernières décennies à un the "ignoration of hermaphroditic fish by com- rythme rapide, les morphes dichromatiques adultes sont syn- parative endocrinologists, behaviorists, and ecolo- onymisées. Il y a peu d’espèces monochromatiques. gists - all of whom should find among these un- Les Labridae sont des hermaphroditesprotogynes. La plupart usual fish exceptions to prove their rules" (Atz, des sont espèces décrites comme étant monandriques, mais il y or an illustration of the drawback of the atti- a une minorité d’espèces diandriques (faiblement ou extrême- 1965)? mâles aussi bien tude scientist to stick to the facts and but ment dichromatiques), aux primaires que secon- as nothing daires. Les mâles terminaux se reproduisent avec des femelles the facts, according to Hull's observation (1989) Cer- seules, mais ceux de phase initiale fraient enaggregations. that "Those scientists who have attempted to taines espèces ont des harems, et les mâles de grande taille sont produce theory-free descriptions of natural territoriaux, de façon permanente ou temporaire. Pendant ces have had little the dernières décennies, la connaissance de facteurs sociaux divers phenomena pitifully impact on of science"? a beaucoup progressé, ce qui a abouti à des modèles théoriques course 226 M.J. Roede - Dichromatism and sex reversal in Labridae Later, several ichthyologists extended both the mention its relation to sex - a first comparative, labrid empiric and theoretic knowledge about the swift, demographic study (data on abundance, of size- the agile fish. Yet, except for the world-topic harem color-, and sex-composition of popula- Labroidesdimidiatus(cf. Robertson, 1972) and the tions) was performed. Investigations of 5800 speci- Science coverstory of Thalassoma bifasciatum (cf. mens belonging to one Mediterranean and seven Warner et al., 1975), the wrasses stayed mainly a Caribbean species conclusively proved reversal of small in all and in- field of interest for a relatively in-crowd. sex eight species studied, quantified an However, in view of the models labrids offer terspecific variability with in some species a strict, population biologists, and the interest of e.g. par- in others a more loose relationbetween color, size, tial and total outsiders as sociobiologists and and sex (Roede, 1966, 1972, 1975). and of sexual be- feminists for the evolution of sex The present paper intends to check the universali- havior in Labridae deserve of this brief of general, the certainly ty variability by a survey current more general recognition. literature, including theoretical explanations con- The speciose family of Labridae is most diverse cerning the evolution of dichromatism and sex in terms of size and form. Closely related species reversal. often cannot be separated on basis of meristic Color offers relevant identifi- characters. pattern a cation mark, though complicated by the fact that Labridae numerous species display a striking phenotypic diversity during life. Juveniles may differ from the General information. — (If no specific reference is adults, and there may be a smaller, plainly colored given, the informationis from Roede, 1972.) as well as a larger, brightly colored adultphase. The Labrid fishes are (sub)tropical and temperate marine of clear lattermay exhibit an elongation of parts of the dor- species coastal waters. Typically, sal fin or of the pelvic fins, a strongly forked caudal they have thick lips and protruding teeth. fin, or a prominent hump on the forehead. Most wrasses are reef-dwellers, active during Since Linnaeus, roughly speaking, five steps in daytime, but with approach of sunset or danger the approach of this dimorphism can be distin- rapidly seeking shelter among the rocks or dense guished. At first, the adult forms were separated layers of algae, or digging into the sand. Tropical into different consid- species. Secondly, they were species can be observed the whole year through but ered to be females and males of one protogynous in colder areas in autumn and winter the fishes species. This concept was unsettled when among either move to deeper water or hibernateburrowed the "female" morph functional males were found. under the sand. The first indications in this direction date back to Various species form abundant aggregations, the end of the 19th but with crowds labroid century these findings were mingling the of other species. not taken Skin- and scuba- Less less certainly generally up. common are numerous, homospecific spe- diving underwater observations on labrid cies at rockless sand in expanded staying cays or seagrass social and sexual be- beds. In the Labridae ben- systems, including territorial general greedy are havior. This knowledge formed the base for thophagic carnivores, not overparticular in the hypotheses to explain labrid dichromatism and choice of their food. Though some interspecific reproductive in biology the framework of evolu- differences in diet occur, there is a great overlap. tionary theories; at first, by field researchers (vari- According to size the diet changes from copepods ous papers by Warner and Robertson c.s.), later to mainly crustaceans and molluscs. Robertson & also by mere theoretic analysis (Charnov, 1982). Polunin (1981) and Robertson (1984) experimental- Around — 1960/1963 when for some European ly refuted the traditional view of a food resource color matter species and sex were a of argument, partition among reef fishes. (The young of) some and for the of Caribbean majority wrasses change species are cleaner fishes, feeding on ectoparasites of color was not or only vaguely described, not to of other fishes. - Bijdragen tot de Dierkunde, 60 (3/4) 1990 227 Color patterns and dichromatism Besides, Randall and others described: (a) A few monochromatic species: Coris venusta (Randall, 1976), Labroides dimidiatus (Robertson & Hoffman, 1977), Two categories of color changes can be distinguished: Pseudolabrus semifasciatus, P. torotai and P. gayi (but P. color - due to and a. Fast, reversible shadings of aggregations fuentesi is sexually dichromatic) (Russell & Randall, 1980) and dispersions of the pigment within the chromatophores. These Labroides phthirophagus (Randall, 1985). are related to affective behavior. Yet, prudence is called for when uniform coloration is record- b. Morphologicalcolor changes - in which the number of chro- ed, because this can be due to the fact that the relatively more matophores may alter as well as the amount of pigment they rare TP specimens were just not included in collected samples. contain. These are relatively slowly developing processes of a As illustrated by Thalassoma cupido, an abundant Japanese rather irreversible character. wrasse that became listed as dichromatic when Katherine Meyer (1977) bothered to collect a 220 specimens. (b) Some species showing just a fading of colors in relation to The following refers to the morphological, adult increase in size, in some combined with alteration of particular color changes. Roede found in relation to increas- spots, e.g. Halichoeres podostigma(Randall, 1980), H. hortula- size of: color ing a variety (a) no striking changes of nus and H. trispilus (Randall & Smith, 1982), H. ornatissimus (Halichoeres