Firoloida demarestia Lesueur 1817

Introduction

Firoloida is a monotypic genus represented by the cosmopolitan species F. demarestia. It is the smallest (maximal body length of 40 mm) and most transparent species in the family Pterotracheidae. The visceral nucleus is terminal on the trunk, followed by a short ventral tail and either a permanent egg string (in females) or a tail filament (in males). Prominent tentacles and a fin sucker are present in males, but are absent in females.

Brief Diagnosis

A pterotracheid with:

• elongated, cylindrical body divided into a proboscis, trunk and a very short tail
• tentacles, fin sucker and tail filament only in males
• permanent egg string in females

Characteristics

1. Body morphology
1. Body elongate, cylindrical
2. Proboscis short relative to the long trunk
3. Visceral nucleus terminal on trunk
   
4. Tail ventral and short
   
   


Figure. Body regions and selected structures in Firoloida demarestia. ©

2. Sexually dimorphic characters
1. Permanent egg string extends posteriorly from base of visceral nucleus in females


Click on an image to view larger version & data in a new window



Figure. Posterior body region, right side in female Firoloida demarestia. ©

2. Tail filament posterior to visceral nucleus in males
   
3. Sucker small and located on anterior margin of swimming fin in males
   
4. Tentacles prominent, located anterior to eyes in males (see photo below)


3. Eye morphology
1. Lens capsule oblong, with lens basal and distal portion slightly opaque


Click on an image to view larger version & data in a new window



Figure. Dorsal view of right eye in male Firoloida demarestia.©

4. Larval shell (shed at metamorphosis)
   
   
   
   
   
   Figure. Larval shell of Firoloida demarestia.  Left: dorsal view (scale bar = 100 µm). Right: apertural view (scale bar = 50 µm). © 2007 Arie W. Janssen
   
   
5. Radula
1. Central tooth bears two long, sickle-shaped and pointed posterior processes on its basal plate
   

References

Lalli, C. M. and R. W. Gilmer. 1989. Pelagic snails. The biology of holoplanktonic gastropod mollusks. Stanford Univ. Press, Stanford, pp. 1-259.

Richter, G. and R. R. Seapy. 1999. Heteropoda, pp. 621-647. In: D. Boltovskoy (ed.), South Atlantic Zooplankton. Leiden: Backhuys Publ.

Tesch, J. J. 1949. Heteropoda. Dana Rep. 34, pp. 1-53.