Family Microlaimidae

                                 Revised 07/17/26

Classification:

Phylum Nematoda

  Class Chromadorea

    Subclass Chromadoria

Microlaimida

Microlaimina

Microlaimoidea

Microlaimidae Micoletzky, 1922          

A family consisting mainly of free-living marine nematodes; a few soil-inhabiting species. 

• Cuticle with striations, often smooth ate anterior end,  withut lateral fields.
• Head with cap or cephalic helmet
• Cepalic sensillae in 3 distinct circles (6,6,4) with the four cephalic setae short.
• Amphids circular or unispiral, near base of stoma.
• Stoma simple, funnel-shaped, with denticles.
• Esophagus cylindrical; muscular, sometimes ending in a terminal bulb.
• Females diovarial with ovaries outstretched.
• Males less common than females, without supplements
• Tail elongate conoid with caudal glands and terminal spinneret.
• Mainly marine nematodes; a few soil-inhabiting species.

The family Microlaimidae is often one of the most abundant groups of free-living nematodes in the benthos from shallow to deep-sea habitats.  They have been found to depths of  7800 m in the southern  Pacific Ocean (Revkova, 2017).

Key to some genera of the family Microlaimidae (adapted from Kovalyev and Tchesunov, 2005)

1  Cephalic sensillae of the third circle equal to or longer than sensillae of the second circle .���.. 2

2. Males diorchic............................................................������ ����������.3

3. Body cuticle covered with numerous spines ��.........................��....................Acanthomicrolaimus

4. Body cuticle without spines ������.................................������������.5

5. Caudal gland with separate outlets. Spicules and gubernaculum weakly sclerotized� Ixonema

6. Caudal glands with common outlet. Spicules and gubernaculum more or less sclerotized��...�..7

7. Cephalic sensillae of second and third circles closely spaced (<1/3 head diam apart).

Peribuccal tissue of esophagus enlarged in pharyngeal bulb ��......������������.8

8.  Left subventral of stoma with numerous denticles�......................................���Pseudomicrolaimus

9  Subventral denticles not numerous or absent.................................�������.Bolbolaimus

10. Cephalic sensillae of second and third circles widely spaced (>1/3 head diam apart).

Peribuccal tissue not enlarged or weakly enlarged ��������������.Microlaimus

11. Males monorchic.............................................������������������...12

12. Somatic setae on short processes........................................................................... Bathynox

13. Somatic setae not located on processes ��................................������.Aponema

14. Cephalic sensillae of third circle shorter than those of second circle..................................���15

15. Numerous postamphidial somatic setae present. Amphids multispiral .����� Spirobolbolaimus

16 Postamphidial somatic setae absent. Amphids monospiral..................................�..Caligocanna

    Go To Dictionary of Terminology 

References

Kovalyev, S.V. & Tchesunov, A.V. 2005. Taxonomic review of microlaimids with description of five species from the White Sea (Nematoda: Chromadoria). Zoosystematica Rossica, 14: 1-16.

Leduc, D., Verdon, V., Zhao, Z.Q. 2017. Phylogenetic position of the Paramicrolaimidae, description of a new Paramicrolaimus species and erection of a new order to accommodate the Microlaimoidea (Nematoda: Chromadorea). Zoological Journal of the Linnean Society, 20:1-18

Revkova, T.N. 2017. Two new species of free-living nematodes genera Microlaimus de Man, 1880 and Aponema Jensen, 1978 (Nematoda: Microlaimidae) from the Black Sea. Zootaxa 4344:387-394.

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