Columbianum Verhoeff, 1941

Read, Helen J. & Enghoff, Henrik, 2018, Siphonophoridae from Brazilian Amazonia Part 1 - The genus Columbianum Verhoeff, 1941 (Diplopoda, Siphonophorida), European Journal of Taxonomy 477, pp. 1-23 : 6-7

Genus Columbianum Verhoeff, 1941

Columbianum Verhoeff, 1941: 216 . Type species: Siphonophora gracilicornis Carl, 1914 , by monotypy.

Columbiozonium Verhoeff, 1941: 216 . Type species: Siphonophora pearsei Chamberlin, 1923 , by monotypy, synonymized by Jeekel (2001).

[ Chamberlinium Verhoeff, 1941: 215 . Invalidly proposed without a type species.]

Diagnostic notes

As understood here Columbianum , is a Central and South American genus with a clear demarcation between the head and rostrum.

Other characters that may help to distinguish this genus are:

• a relatively short rostrum relative to the head length. Rostrum more or less parallel-sided and much narrower than head. Rostrum straight or slightly downcurved.

• relatively long antennae clearly reaching well beyond the tip of the rostrum.

• the anterior margin of the collum appearing to be strongly curved posteriorly, but under SEM this can be seen to be mostly due to a thin, non-tuberculate region bordering on the concavity and contrasting with a thickened region with tubercles. This can usually be seen under light microscope when looking carefully.

• a short tergite 2 which is less than half, sometimes only one third, of the length of the collum.

• pleurites in those species examined have a sinuous ventral margin, at least on anterior pleurites, to accommodate the coxae, and often a stepped posterior margin, sometimes with a distinct spike.

• constriction between pro- and metazonite with a single line of setae.

• metazonites slightly larger than prozonites, giving a more or less pronounced ridged effect, at least anteriorly on the body.

• short tergal setae.

• a crenulated limbus on posterior margin of tergites.

• hind edge of pleurites crenulated or strongly serrate when seen from ‘inside’.

• sensory fields on antennomeres 5 and 6.

• the gonopods appear to conform to the general siphonophorid plan and are quite simple. The anterior gonopods are robust and with abundant spines, bent sharply anteriad and frequently with an additional projection on the mesal side. The apical segment of the posterior gonopods is long and thin, frequently with a small spine towards the base and with a web-like or bifurcated tip.

• the accessory claws of the three species examined from Brazil are all very large and robust and arising from the anterior side of the claw. They are visible under light microscope at least on the legs in the anterior half of the body but not on the first few leg pairs. Claws hence almost appearing to be double.

These characters are not necessarily apomorphies, nor diagnostic generic features, because the extent to which they occur in previously described species is not yet known.

The distinguishing features between the three new species are outlined below in the species descriptions. In addition, a plot of body width against number of podous tergites was made, and three clear groups can be seen. That for the males is given in Fig. 1A and for the females in Fig. 1B .

Tentative list of species included in Columbianum

Columbianum andecola (Kraus, 1954) – Peru

Columbianum aviceps (Loomis, 1961) comb. nov. ex Siphonophora – Panama (perhaps synonymous with telana )

Columbianum corynetes (Chamberlin, 1923) comb. nov. ex Siphonophora – Guiana

Columbianum fallens ( Chamberlin, 1922) comb. nov. ex Siphonophora – Guatemala and Panama

Columbianum gracilicorne (Carl, 1914) – Colombia

Columbianum meinerti (Silvestri, 1898) comb. nov. ex Siphonophora – Venezuela

Columbianum monzonica (Kraus, 1960) comb. nov. ex Siphonophora – Peru

Columbianum paulistum ( Schubart, 1945) comb. nov. ex Siphonophora – Brazil

Columbianum pearsei (Chamberlin, 1923) – Colombia (perhaps synonymous with gracilicorne )

Columbianum porcullae (Kraus, 1954) – Peru

Columbianum progressor ( Chamberlin, 1922) comb. nov. ex Siphonophora – Honduras

Columbianum relicta (Chamberlin, 1923) comb. nov. ex Siphonophora – Guiana

Columbianum telana ( Chamberlin, 1922) comb. nov. ex Siphonophora – Honduras

Dubiously included species

Siphonophora platops Loomis, 1941 – Dominican Republic

Siphonophora pseustes Chamberlin, 1923 – Mexico

Siphonophora lafloridae Kraus, 1955 – Peru

Figures

Fig. 1. Body width (mm) against the total number of tergites with legs for new species of Columbianum Verhoeff, 1941. A. Males. B. Females.