Delkarlye enamalla J. L. Barnard 1972

Delkarlye enamalla

DIAGNOSIS. — With the characters of the genus.

DESCRIPTION. — Based on one female 3.2 mm, and her hatched juvenile, 0.90 mm, completely filling her brood pouch; antenna 1 extremely large, cylindrical, article 2 bearing ventral trough, allowing article 3 to be attached geniculately to article 2 and to be bent ventrally; antenna 2 small and slender, gland cone occurring mesially; head and pereonite 1 each with small dorsolateral hump on each side anteriorly; lacinia mobili and 1 spine fused solidly to body of mandible, unknown whether two parts form only lacinia mobilis or not, or whether both represent spines; one lobe of outer lip bearing 1 cone, other lacking cone; inner plate of maxilla 1 linguiform, naked; outer plate with 7 spines; dactyl of gnathopod 2 with long comb of spinules on medial face; coxa 1 with weak posterior seta; article 6 of perepods 1-2 slightly tumid, spines small but appendage not distinctly prehensile, though dactyl long and curved; pereopods 3-4 with article 6 falconiform, bearing proximal spined protrusion, dactyls long and curved; pereopod 5 very small, article 6 intermediate between that of pereopods 1-2 and that of pereopods 3-4; pereopod 3 with hump (like a gall with heavy cuticular divisions reminiscent of the dinoflagellate Peridinium) on article 5 similar to humps on head and pereonite 1 (consistent on both sides of animal); lateral face of peduncle on uropod 3 dorsally extended, inner ramus extremely flabellate; telson very broad subproximally (appearing squashed in Figure 17 but actually natural); cuticle bearing polygons of moderate development but especially well developed on epimera, coxae, and proximal articles of pereopods 3-4, polygons irregularly developed and of various sizes.

JUVENILE (0.90 mm). — Generally identifiable with adult because of similarities in uropods 1-2, gnathopods 1-2, upper lip, head, and coxae, but eye very small and unclearly discerned, and pereopods 3-4 with immensely elongate article 6, bearing only 1 spine on main protrusion, dactyls of pereopods 1-5 all immensely elongate, otherwise pereopods similar to adult except that flange on article 2 of pereopod 5 undeveloped. One may suggest that juveniles are born with articles 6-7 of pereopods 34 highly enlarged but that, as growth proceeds, these articles have a disproportionately low rate of size increase in comparison to the proximal articles of these pereopods. One may say the same about the setule at the posteroventral corner of epimera 1-3, as it is as large as that found in the adult.

HOLOTYPE. — SAM, female, 3.2 mm.

TYPE-LOCALITY. — Shepherd 18, Toad Head, West Island, South Australia, 4 m, vertical face, in algae, 13 October 1968.

MATERIAL. — The holotype and her offspring.

DISTRIBUTION. — South Australia, sublittoral.

Paradexamine Stebbing

Paradexamine Stebbing, 1899b:210-211.

Dexaminoides Spandl, 1923:87.

DIAGNOSIS (revised). — Ocular lobe of head never verticalized; accessory flagellum a small cube with 1 or more setules and aesthetascs; mandibular molars moderately triturative to nearly smooth, with or without ordinary setae and ragged setae, incisors multitoothed or simple, occasionally heavily cornified, rarely lacking spines, palp absent; inner lobes of lower lip distinct, mandibular lobes long to short, blunt to thin and curled; palp of maxilla 1 uniarticulate; inner plates of maxilliped vestigial to large, setae large or obsolescent, palp 4-articulate; pereopods generally simple, pereopods 3-5 generally similar to one another; coxae not acuminate or bifid; coxa 5 much shorter than coxa 4, body always with a few side teeth on posterior segments, pleonite 4 with sharp dorsal tooth; only pleonites 5-6 fused together.

TYPE-SPECIES. — Dexamine pacifica Thomson.

RELATIONSHIP. — In the expanded Dexaminidae (see J. L. Barnard 1970b), this genus must have statements about mandibular palp, urosome, telson, and head not heretofore necessary. The nearest genus appears to be Dexamine Leach, which occurs only in the Mediterranean and North Atlantic if one considers the high probability that D. serraticrus Walker (1904) (from Ceylon) is a member of Paradexamine. Walker did not describe or figure the mouthparts. Dexamine differs from Paradexamine in the 3-articulate maxillipedal palp, the vestigial inner lobes of the lower lip, and two of its 4 well-known species lack pleonal side teeth. Because they all have pointed ocular lobes and no side tooth on pleonite 4, they appear similar to group IIC of Paradexamine, but, like group IIB3j, they all have the telsonic lobes partially fused basally. Since the loss of maxillipedal palp article 4 would be presumed to be irreversible, the direction of evolution, if any, would appear to occur from Paradexamine toward Dexamine.

See “Taxonomic Characters in Paradexamine and Guernea” under “Dexaminidae.”

KNOWN SPECIES AND PROBABLE NEW SPECIES

alkoomie, new species; Australia

barnardi Sheard, 1938; New Zealand

barnardi of Nagata, 1965; Japan

churinga, new species; Australia

dandaloo, new species; Australia

echuca, new species; Australia

fissicauda Chevreux, 1906; Antarctica

flindersi (Stebbing, 1888); Stebbing, 1910a; Australia

flindersi of Nagata, 1965; Japan

flindersi of Pirlot, 1938; Indonesia

frinsdorfi Sheard, 1938; Australia

goomai, new species; Australia

houtete J. L. Barnard, in press; New Zealand

lanacoura, new species; Australia

linga, new species; Australia

marlie, new species; Australia

maunaloa J. L. Barnard, 1970a; Hawaii

miersii (Haswell, 1885); Australia (unclarified)

moorhousei Sheard, 1938; Australia

muriwai J. L. Barnard, in press; New Zealand

nana Stebbing, 1914; Schellenberg, 1931; Antarctica

narluke, new species; Australia

orientalis Spandl, 1923, 1924; Red Sea

orientalis of J. L. Barnard, 1965; Micronesia

otichi, new species; Australia

pacifica (Thomson, 1879) (see synonymy herein); New Zealand

pacifica of Nagata, 1960

quarallia, new species; Australia

ronggi, new species; Australia

?serraticrus (Walker, 1904); Ceylon

sexdentata Schellenberg, 1931; Antarctica

thadalee, new species; Australia

windarra, new species; Australia

INTERRELATIONSHIPS OF SPECIES

The differences among species of Paradexamine in Australia, New Zealand, Hawaii, and Micronesia have been found to be based on such small and heretofore minor characters that the following taxa, not as yet clarified in many characters, cannot be discussed at present: Dexamine miersi Haswell (1885), Dexaminoides orientalis Spandl (1923), Paradexamine nana Stebbing (1914), and P. sexdentata Schellenberg (1931). The identifications by Nagata (1960, 1965) from Japan of P. pacifica, P. barnardi, and P. flindersi may represent species distinct from those in the southern hemisphere. The Micronesian species is Dexaminoides orientalis as identified by J. L. Barnard (1965).

The relationships of taxa that can be considered are developed in the following key from my concept of the general phyletic order, which is discussed immediately after the key.

Note that P. flindersi (Stebbing) is placed in section I, but if no side tooth really occurs on pleonite 4, the species falls into the same couplet of II, as P. thadalee and P. dandaloo, from which P. flindersi differs in many ways (see Stebbing, 1910a). No conclusion regarding the primitive state of any group of Paradexamine is implied in the order of the above phyletic key. One should note that no species with both a side tooth on pleonite 4 and an ocular tooth has evolved (or has been discovered yet). The relationships delineated in the specific descriptions that follow do not always include every paired relationship for every species; the reader should consult the “Phyletic Key” to discern the network of relationships.

PHYLETIC KEY

The three main groups of species (I, IIB, IIC) do not yet imply any possibility of establishing subgenera as the various exceptions occur in group characteristics noted in the key. Mandibular lobes of lower lip are occasionally uncharacteristic, as are facial spines of epimera. There are undoubtedly other ways to arrange the taxa in terms of mandibular lobes, flagella of antenna 2, and anterior coxae, but so many species probably remain to be described that any further analysis will not prove valuable until these have been found.

The evidence that straight-line phyletic relationships occur in various groups or that characters do not mutate (in an evolutionary sense) from one alternative to another may be seen in the strong similarities between P. thadalee and P. fissicauda, in telsonic spine pairing and in slit-pits, but the mandibular lobes of the lower lip in the two species differ strongly. Similar evidence is also present in (1) P. flindersi, which has mutant mandibular lobes but which otherwise occurs in a group with blunt lobes; and in (2) the “Micronesian species” with blunt lobes otherwise placed in a group with thin curled lobes. An odd coxa 3 crops up in P. otichi and P. goomai that, with other characters, demonstrates their closeness in a statistical cluster, but the differences in their pereopod 5 and uropod 1, plus many other characters, tend to disperse these two species.

Whether groups I, IIB, and IIC each represent monophyletic flocks is open to question, especially on the basis of phenetic taxonomy, in which characters have no rank. One might thus consider P. fissicauda a member of group I, with only one character of difference: the loss of the side tooth on pleonite 4. The species is an aberrant member of group IIB because the mandibular lobes are blunt and straight and it has a slight anteroventral invagination of the head and the narrow telsonic lobes also characteristic (more or less) of group I. But it fits group IIB equally well because of the facial setae on maxilla 2, the thin article 2 of pereopod 5, the facial spines of the epimera, and because, like a few other members of group IIB never found in Group I, it has paired telsonic spines and a slight fusion of the telsonic lobes basally. Paradexamine fissicauda, therefore, forms a unit between the two clusters, but whether the loss of the side tooth of pleonite 4 came first or later cannot be decided.

By ranking the latter character, one judges it came first or it is a major character change. One then has to judge whether P. fissicauda could be closer to the basic stock of group IIB than to other species, like some of its siblings that share its unique characters, such as P. churinga or P. thadalee (indicated by cleft and spines of telson). As a bridge species, it will deserve great attention in further studies of the evolution of this genus.

One also may point to the Micronesian species (identified as Dexaminoides orientalis Spandl by J. L. Barnard, 1965) as a taxon that has lost the side tooth of pleonite 4, bearing acute ocular lobes, but that still bears the blunt mandibular lobes of group I, yet otherwise has affinities with P. moorhousei in mandibles. There is no way as yet to decide whether the direction of evolution has been the gain or loss of a side tooth, or of an ocular cusp, or the change in mandibular lobes, nor whether the alternatives can be regained, once lost — or lost, once gained.

In conclusion, the scheme presented has the advantage of placing together pairs and triads of species considered to be siblings, and thus it demonstrates that flocks of species do occur in the genus, that clusters of species do occur, and that bridge or satellite species represent links between the clusters.

DORSAL PLEONAL TEETH

The number of dorsal pleonal teeth increases with growth in the juveniles of Paradexamine, but in adults the teeth remain fairly stable in their count. Juveniles of the few species known so far have rudimentary teeth on pleonites 4-5 similar to those in adults, but, anterior to pleonite 3, teeth are usually absent. In most species the dorsal tooth of pleonite 2 appears to develop first, then the 2 laterals, and then the sequence is repeated on pleonite 1 and on pereonite 7 (if that point is reached by the species in question). Some species, however, especially P. moorhousei, have lateral teeth developing before the dorsal tooth. The following formulae are those found so far in Australian species. The formulae are of occasional assistance in the identification of specimens known to be adult, but caution should be used because aberrancies and even the ranges of normal formulae are unknown in several of the rarer species. The species with the largest numbers of specimens examined in this study have been fairly consistent in tooth formulae: churinga, frinsdorfi, lanacoura, moorhousei, quarallia. The very large dorsals of P. lanacoura are especially noticeable, and the poorly developed teeth of P. quarallia represent the opposite extreme. The side teeth on pleonite 4 of P. quarallia are very difficult for one to see without mounting the specimen and examining it through a compound microscope, but the lobular side teeth of pleonites 2-3 make this procedure unnecessary. The odd situation on pleonite 1 of P. moorhousei is characteristic also of the majority of specimens.

To facilitate printing the formulae, I have quoted them from rear to front, commencing with pleonite 4 and progressing forward to pereonite 6. The six theoretical formulae not yet found on any Australian species are omitted. Number “3” means the segment has 1 dorsal and 2 side teeth; “2” means the dorsal tooth is absent and only the side teeth are present; “1” means only the dorsal tooth is present. Paradexamine flindersi (Stebbing) probably has lateral teeth on pleonite 4, since the species is otherwise similar to several species bearing these teeth.

DORSAL TOOTH FORMULAE

(Rear to front, commencing with pleonite 4)

The young male, in the process of changing from its female appearance and acquiring the male secondary characteristics, can be a difficult specimen to identify as it may actually lose some characteristic typical of the female and yet not definitely appear to be a male in other respects. For example, in Key B-l, couplet 2, following, the young male may lose the ventrodistal process on article 1 of antenna 1 before the specimen otherwise is easily recognizable as a male; therefore, it appears to be a female without that process, which is so misleading as to prevent exact identification. Specimens that do not readily fit the keys and their alternatives should be set aside temporarily until more observation is made, when perhaps some could be identified by a process of elimination discussed under “Identification.” Many stages of transformation in the males of Paradexamine have yet to be described, and of course undiscovered species also may occur.